Blackdog36

iTrader: (3)

My goal for this post is to provide information and further discussion on how to properly design an optimally “tuned” TPI system. I’ve read posts that mention how runner length needs to match cross sectional area for it to be tuned among other things. We also seem to know what components make a good strong engine combination depending on what intake and cam you use. However, I have never seen a real good explanation of how different aspects of a TPI system work together. More importantly how you can blueprint an engine build for maximum efficiency and not just throw parts together.

I’ve done extensive searching online and found some interesting information that I believe shows us how to properly design an optimized TPI system. I made several excel sheets that show what the tuned (effective) rpm will be for a stock TPI, FIRST and Accel Superram system on various engine sizes and cam durations.

I basically found two formulas, plotted their values on a graph. Where these two graphs intersect is the optimal tuned rpm for that engine size, cam intake duration and intake runner diameter.

I tried to make excels files easy to adjust for your particular intake, engine size or cam duration if you are using something different (TPIS, Edlebrock, stealth ram, etc)

Tuned RPM from intake Length

The first formula I found on www.grapeaperacing.com/tech/inductionsystems.pdf. Grapeaperacing did a tremendous job explaining intake fundamentals particularly intake length. Pages 6 & 7 of the pdf list the following formula which allows you to determine required intake length from cam intake duration, velocity of pressure wave, desired tuned rpm, reflective value (harmonic) and intake diameter.

L = ((EVCDx.25xVx2)/(rpmxRV))-.5D

I rearranged formula to yield tuned rpm based upon intake length. As intake lengths are usually set (unless Siamese runners), this is the most helpful expression of the formula.

rpm = [(EVCDx.25xVx2)/(L + .5D)]/RV

You can read linked pdf for an in depth explanation of the formula and wave harmonic theory. The primary factor in determining tune rpm value with this formula is the intake tract length and cam intake duration. Intake runner diameter has very little effect since its magnitude is minimal compared to others in equation. Plotting this formula yields almost a flat line with rpm changing slightly with different intake diameter sizes.

I like this formula since it incorporates many variables into determined tune rpm value. Most formulas I found online for determining tuned rpm from intake length are very basic or rule of hand “approximations”. This formula takes into account cam intake advertised duration (not duration at 0.05”) to determine EVCD (effective valve closed duration). Also in finding EVCD, you have to subtract 20 degrees so that pressure wave inside intake tract will hit intake valve before it closes and after it opens. I think this is the key aspect of maximizing TPI power and this formula takes it into consideration.

For each intake, I used ECVD derived from the Comp Cam XFI line. They have advertised intake durations of 252, 260, 268, 280 and 292. Changing which duration is used, alters tuned rpm value by a few hundred rpm. If you intake length is fixed, one way of fine tuning rpm value is to use a different duration.

Note that the intake length (L) used is entire length of intake from backside of intake valve in cylinder head to where tube runner starts in plenum. I personally measured intake length from my FIRST unit and used values found online for stock TPI and Accel Superram.

It also appears that reflective value (RV) of 3 yields best tuned rpm for street use from 3,700 to 4,800 rpm depending on what intake is used. Higher RV of 2 while increasing power from tuned effect; raises tuned rpm too high beyond street rpms. At higher rpms, intake runner diameters cannot be opened wide enough to properly feed engine (see below).

Peak Torque rpm from intake diameter

Second formula I found is one that allows you to determine peak torque rpm from engine size, number of cylinders and intake area. It can be located here www.wallaceracing.com/runnertorquecalc.php. I am not sure of the specific formula as you input values to generate rpm value.

I used this calculator to determine peak torque rpm keeping engine size the same while increasing intake area. As expected, rpm increased when intake area was made larger. An engine will peak at a higher rpm if more air is fed to it through a larger intake runner. Graphing results from this calculator yielded an increasing diagonal line from left to right.

Analysis and Conclusion

I’ll discuss the stock TPI graph results for simplicity. Results we see from stock TPI graph are the same with other intakes, just that intake runner diameters and engine sizes are different. Trends and selection procedures are alike.

Graphing values for stock TPI yields results that we are familiar with. Based upon stock intake diameter, a 305 produces peak torque at 3,933 rpm, 350 at 3,427 rpm and 383 at 3,132 rpm. These peak rpm values do increase as runner diameter increases for each engine.

Lines graphed from both formulas meet at around 3,933 rpm for a 305 engine, with stock TPI diameter of 1.47 inches and cam advertised intake duration of 268. This combination will produce best power for parts involved. You’ll notice that if a higher duration cam is used (280 or 292), the tune rpm based upon Grapeaperacing formula is reduced. Tuned rpm value for a 292 duration cam is 3,735 rpm at stock intake diameter. However rpm engine produces peak torque is still at 3,933 rpm. A difference of 200 rpm (3,933,-3,735). Therefore your intake runner diameter is not best matched to intake length and cam duration for producing peak power!

At stock intake diameter produces peak torque of 3,427 rpm on a 350 and 3,132 rpm on a 383. The highest duration cam used of 292 degrees only produces a peak torque rpm at 3,735 rpm. So even though a 383 engine could use a 292 cam and be “street-able”, the tuned rpm values from each formula would be off by 600 rpm (3,735-3,132)! Stock intake diameter is not large enough to feed 383 where it wants to peak based upon intake length and cam duration. This verifies why we see lower power numbers and rpm band on larger engines with stock intake. Stock intake runners would have to be opened up to 1.60 inches in order to match rpm value from stock intake length and 292 cam duration. I am not sure if opening runners that much on stock intake is possible.

Interesting to note for a given engine size, shorter intake duration cams require larger diameter intake runners. I believe this is due to fact that shorter duration cams result in less valve opening time and therefore less air into engine. The engine still needs the same amount of air to work at a given rpm, regardless of the intake duration. Larger diameter intake runners will enable engine to get more air during that shorter cam duration to still function optimally.

I hope the above will help people in building their engines to understand what is needed for maximum performance. I would appreciate feedback and any questions or corrections you have. I am very excited that in the future I may be able to test everything out on large 400+ sbc with my properly ported FIRST TPI intake and matched cam

Blackdog36

iTrader: (3)

PDF's of graphs.

Guest

The formulas you posted are theoretical, and there are more factors to airflow or waveforms than just length, or diameter. For example, the following statement:

You might want to visit the brochures from Chevrolet or Pontiac, both of which show nothing of the sort. In fact the RPM of the TQ peak they list on 305's and 350's with the same cam are identical.

Theories are nice to look at, and maybe make generalizations, but not much good in practice. Way too many other factors not being considered. Bends, changes in area as an example.

1989GTATransAm

iTrader: (3)

So lets take a look at the First Intake graph. If you had a diameter of 1.800" it looks like peak torque would be just above 5000 rpm. With loses maybe 5000 rpm.

1.800" equals a CSA of 2.54 inch square. So if you were to maintain that for the total length of the First intake system it seems to me you could start picking up the 2nd harmonic wave in the upper 5000 range and carry well into the 6000rpm range. The 3rd harmonic would be in the 4000 rpm range and the 4th harmonic would be in the upper 3000 range.

So if one were to shift at say 6500 and the rpm would drop in the 4000 rpm range you would be right in the middle of the third harmonic for good acceleration after the shift. At 6500 rpm you would be able to pick up the benefits of the extra boost of the 2nd harmonic wave.

If you have good exhaust scavanging it would cover some of the dip between the 3rd and 2nd harmonics as the rpms increase. Interesting subject. Here are the links to a couple of calculators I have come across.

http://www.bgsoflex.com/intakeln.html

http://webcache.googleusercontent.co...&ct=clnk&gl=us

With last one make sure you read the first post regarding the Super Flow information.

1989GTATransAm

iTrader: (3)

Right now I am investigating using 2" diameter aluminum u-bends for runner material and making my own. They have an ID of 1.875" and a CSA of 2.76". It appears for my motor maybe a total runner length of between 20" and 21" will allow me peak horsepower at 6500 rpm. Peak torque at 5000 rpm. I am hoping to pick up the 2nd, 3rd and 4th harmonics.

I am still working on the CSA of the base itself. Like to taper or not to taper and the final CSA where the intake base meets the head. One thing about EFI you don't have to worry about fuel falling out of suspension. I have the exhaust tuning about where I want it but I might want to extend the collector link a tad to help cover the dips between the 3rd and 2nd harmonics.

Then there is the inertia of the air mass in the runner. This is one of the major players in getting cylinder filling. So between air inertia in the intake runner, harmonic wave tuning and exhaust wave tuning maybe we can get a pretty good VE. Who said TPI is outdated.

1989GTATransAm

iTrader: (3)

Found this nugget of information of Speed Talk by Erland ***. The research continues.

"And also the volume of the runner is important. I have never seen a well developed racing engine with less than a cylinders volume in the runner."

So it sounds to me you want the total runner volume including what is in the head to be more than 100% of the displacement of one cylinder. 100%VE is of course 100% cylinder filling. Than the question is would 110% runner volume be part of the equation for 110%VE?

Just thinking about the First intake and the long runners. By the way Extrude Hone is good for adding .039" per wall or .078" of runner diameter. Something to think about on increasing the nominal 1.75"D of the First intake runners.

Blackdog36

iTrader: (3)

Madmax – Of course I know formulas are theoretical. They are one of the many tools we can use to optimize TPI. As I mentioned, you normally only read descriptions from people on what parts work best, not why they do. We put a lot of time and money into our cars. If these formulas help me get closer to my goals, then great. Trying to learn more than just slapping parts together. I could not find stock cam advertised duration values to see exactly how a stock 305 or 350 would look like with these formulas. The graphs still helps us understand why stock TPI is limiting even on a 350.

1989gtatransam – you always seem to be making an intake You’ll have to post some pics of aluminum u-bend runners if you ever get it setup. Indeed interesting if you could design engine and drivetrain to benefit from other harmonics as well. I don’t know if I will be going down the road of custom headers. Only thing I have done for my FIRST manifold is to port match runners to the base. I have to open runners up somewhat and not sure if I want to spend $$ on extrude hone. Worried that honing runners would make opening near base too large since I’ve already port matched them to manifold. I think there would be many variables that make up VE but having more volume in runners than cylinder would help compensate for items Madmax mentioned (bends, transitions, wall roughness, etc). Will have to check out volume calculations once I settle on an engine size.

1989GTATransAm

iTrader: (3)

The way I see it is the mathematics will get you in the ball park. It certainly is better than just cobbling something together without a plan and praying that it will work. To fine tune it one would have to make adjustments and see what effect it has on the dyno. We do not have the time or resources to do that. So all we can do is try and get it close by using the formulas and engine building programs that are available to us.

As to making a new intake the more I get into this the more I learn. As to the exhaust I have been working on my "exhaust termination box" project for close to two years and we are getting to the final phase. I just got my headers back from the coating shop. So they are ready to be installed when Dyno Don can fit me in. At that time I will do the final fitting of the termination boxes. In the meantime I still have the opportunity to play with the exhaust collector length to put where I want the peak rpm tuning to be. I am thinking of augmenting the intake harmonic wave tuning.

sam85iroc

http://www.gmtips.com/3rd-degree/dox/tips/cams/cams.htm

it was compiled by a member, Vader.. I've heard and seen that he has a handle on induction...

InjectorsPlus

iTrader: (1)

FINALLY a decent discussion. Nice to see a thread that doesn't say "I bolted these hacked parts together and we all danced around the dyno". This is the stuff to discuss on how to put a combination together. Not "I bolted together really cool parts everyone worship my dyno sheet". We never know if the modifications are effective, could be more effective, are done right, wrong..... there's no way to tell. A dyno sheet tells you nothing other than that combination of parts, or hacked parts, made XXX HP. ON THAT DYNO ON THAT DAY WITH THAT OPERATOR.

I don't care what the result is. Great thread. Seems so "grown up"...

InjectorsPlus

iTrader: (1)

EXCELLENT! I think that every build should be measured against the theory and see where reality and theory part and adjust the theory to fit reality.

Saying "I hacked up a head/intake this much and made this much power when bolted together with these other parts" really accomplishes nothing. There's no expertise in that. That is why I like PREDICTIONS out of the gate based on understanding of the physics, and not generated by desktop dyno. Generated by knowledge and theory.

How can you possibly get the best results if you don't understand WHY things are being done. The old "I got better flow but it made more power" BIG DEAL! This is the difference between an professional engine builder, and a cool parts screwer together.

Again OP...... great thread.

DAREDEVIL 1

I believe that it all depends what u do with your car !!!!

Is it a race car, daily driver, fun and weekend cruiser...it all depends where u need the tourge and how often u want to brake your engine down to rebuild !!!

High RPM is killing your engine, so if u want to set up the engine to make peak tourge at 4500-5500 RPM ..good luck on your reliabilaty, u just threww it out the door !!!

The stock intake is not the best for racing but its an overall midrange piece!

The best tourge for a dily or weekend car is around 3500-4500 RPM IMO !
And tourge is what u want thruout the complete RPM range ..HP is just there and realy has no use for ya ( kind of )

Tourge is what moves your car..not HP

EXAMPLE: well build engine has ( lets just say ) 350 HP & 400+ FPT @ 4000 RPM
is better then 500 HP & 550 FPT @ 6000 RPM !!

But again, it all depends on what u are using it for !!!!

dhirocz

iTrader: (2)

Nice to see someone trying to understand TPI instead of bashing it for a change.

You and I are on the same page as far as manifold theory. I'm sure you know at this point that the approach in designing a tuned port system is very different than your average engine, like an LT1 for example.

Yes, it's correct that those calculators are based solely on theory, and as such, it doesnt take into consideration real world factors like bends and imperfections in the intake. For example, there are frictional flow losses in the runner based on shape alone, not to mention the clearance bumps for the bolt holes, and variations in cross sectional area which affects the pressure waves, or the head entry angle problem the factory bases have.

A couple of things to add here. First, the peak torque RPM of the heads (pushrod pinch/CSA), cam, exhaust and intake all come into play, with the intake being the biggest factor in a TPI engine. Slight mismatches are ok since it's very hard to get things spot on. A better way to get an idea of your torque peak if there are variances are to take an average of all of them, counting the major factor (intake) twice.This will get you a good idea of where you will peak torque for tuning purposes (if mail order).

Your engine will peak HP roughly 1200-1500 RPM higher than the torque peak in a properly built engine. Flow numbers play a larger role here with throttle response and the difference in peak torque and peak HP RPM. Calculate your I/E flow ratio at .200-.600 lift and take an average. 75% makes a good street/strip head, more making the engine more HP biased with less throttle response and less increases throttle response but chokes the peak HP RPM down. The same poor exhaust port on a vortec is what also gives it it's throttle response, for example. So when I ported my heads, I just profiled the guide and cleaned and polished the exhaust port. Plotting the I/E flow ratio based on flow charts can help a ton in head selection, as well as cam lift. Bottom line is a high I/E flow ratio will extend your peak HP RPM, at the expense of some on the bottom end.

Another big factor people ignore in a TPI engine- exhaust. The primary length and diameter acts in the same way on a tuned port engine, scavenging the cylinder of spent gasses. You need a longer primary in order to provide this suction, which is why long tube headers make sense on a tuned port. Collector length also helps here, so I like using a rather long collector (15"-18") and terminating it into a pressure wave termination chamber.

Lastly, to be effective, the TPI to a point HAS TO be restrictive. People just don't seem to understand this. Don't confuse this with being inefficient. The same restriction to flow is what speeds up the air in the runners which contributes the the wave effect. This means that extra 20 or 30 cfm you get from hogging it out huge can actually hurt performance down low by means of port velocity though it can help it up top. I ignore flow numbers in the intake, and concentrate on using the right size and length. Best place to worry about flow numbers is in the heads.

The 305 TPI is a good example of this happening. Why do you think GM had the 'peanut cam'? Can't have 305's running up there with the 350's, can we? 305 TPI auto cars are cam limited as hell. Stock for stock, the 305 TPI actually has a good bit of potential for a tuned port since the intake matches the engine so well. With some massaging and the right cam and exhaust, a 305 can suprise you. This is why you have a few guys on the boards with suprisingly fast 305 TPI's and nobody chooses to believe it.

dhirocz

iTrader: (2)

If you look at the graphs, you can see the peak torque RPM on the 305, 350, 383 and 434 all hover at 4000 RPM using common runner sizes of stock, 1.575", 1.660" and 1.75". Length is a factor that cannot be changed in regards to wave tuning at a specific RPM; it doesnt change with CID like size needs to.

The mismatch in CSA and runner length on the stock 350 supports the fact that the TPI intake was designed for the 305, not the 350. Also shows how this mismatch can be exaggerated on a 383 using stock parts. Even though this can still make awesome torque with little or no intake tuning, the 383 will stall the port because of the increased flow demand and fall off fast and will never run to it's potential unless the right stuff is used. That pressure wave is what boosts flow past 100% VE (acting like a supercharger)that makes the car so fun to drive near peak torque, and if it can't happen because of poor parts selection, well, that just sucks

Keep in mind this is using the 4th harmonic in the graphs. You can utilize others, which is why sometimes a larger intake works ok on a smaller engine, like the FIRST on a 350. This also requires significantly more RPM which is where the added size helps. Problem is the runner length, you still have that hurdle to tune since intakes aren't that easy to adjust length that much and the port length on a TPI is intended to use the 4th harmonic wave.

Good post! I got tired of trying to explain it, and getting zombified answers like 'why not use a stealthram' and 'it wont make as much HP as XXX intake'.

DAREDEVIL 1

I AGREE WITH ALL OF THIS 99.9 %

thank u !!!!

VERY GOOD AND PRO WRITE UP !

this should be a STICKY !! by itself ..

InjectorsPlus

iTrader: (1)

I have to disagree on I/E ratio. I don't subscribe to that theory. In practice I have never seen it bear out.

Up to the last sentence you had me, so I will ask for clarification. You're not saying flow numbers are the only basis or most important factor on which to judge a head are you?

InjectorsPlus

iTrader: (1)

Great post. Thanks. This is interesting.

InjectorsPlus

iTrader: (1)

Oh no, that is wrong. Torque will get you moving, but it will not keep you moving or going faster. The faster you go, the LESS torque you need and the more HORSEPOWER you need.

For an extreme example look at open wheel race cars. They idle at 9000 RPM and top out about 18,000 rpms. Those engins have gobs of HP but very little torque.

Oh no, if you want to go fast, it's HP at the top end. I'd take that 500HP motor all day long, and the torque on that motor will not be at 6000 RPMs. Unless of course, you are building a dumptruck engine, which for reasons that escape me, seem to be popular.

DAREDEVIL 1

So u say if u had 0 tourge at 4000 and 500 HP u would still move ???

OMG

Its also with in your gears...try to gear a regular car like your example !!! mmhhhhh

oscarfromla

iTrader: (9)

Drag forces due to air grow EXPONENTIALLY with speed, and drag is what keeps your car from going 200 mph and beyond. True, you need torque to get your car moving, but it is torque that is going to overcome the drag forces at high speed.

Horsepower is not a tangible measure of performance in my opinion since it is nothing more than Torque multiplied by engine RPM. This is why I use the torque profile (graph) to judge an engine. High horsepower engines make torque at high RPM. You can play with the numbers to see how torque and RPM affect horsepower. In your example, engines that rev at 18000 RPM can make 1 ft-lb of torque and it can still be "High HP." A die grinder spins at high RPM, but why isn't it high horsepower, torque isn't there.

All engines make torque. Question is where on the RPM range does it make the most. Engines that make most of their torque at high RPM are commonly referred to as high horsepower engines, where as those that make it at lower RPM's are dubbed Torque motors. S

DAREDEVIL 1

[quote=oscarfromla;4766480]Drag forces due to air grow EXPONENTIALLY with speed, and drag is what keeps your car from going 200 mph and beyond. True, you need torque to get your car moving, but it is torque that is going to overcome the drag forces at high speed.

Horsepower is not a tangible measure of performance in my opinion since it is nothing more than Torque multiplied by engine RPM.


, at any speed !!!!

THANK U !

Guest

Power isnt a factor? K...

DAREDEVIL 1

TOURGE IS POWER !!!!!

Hp is a term for a example messurment and actually a side effect !!!!

NO TOURGE = NO HP !!!!

NO HP , can still be TOURGE !!!!

But then again, can we get back to intakes ...it was more fun reading then trying to explain how it realy works..LOL

dhirocz

iTrader: (2)

Torque is a measurement, horsepower is a calculation that refers to the engine's ability to work over time (RPM). Torque must be present over the ENTIRE powerband for the engine to propel the car, however, above peak torque, horsepower, torque over time (ability to work under load) takes over. Since horsepower is a calculation based off torque, torque must be present. Make sense?

Flow numbers are important to a degree. When the tuning takes over and the engine goes over 100% VE, air is being forced in, something like a tiny supercharger. At this point, airflow characteristics through the heads change. Air is being forced in rather than sucked in. The best way to approach this is to improve efficiency around your required specifications and dont concentrate on flow as a whole like many would for a HP based engine.

IP, reread the last sentence. CFM in this case should be used for a judgement of efficiency ONLY and not judgement of performance of the part as a whole (since the tuning pushes the engine over 100% VE, unlike many other designs). If you can gain 20 or 30 cfm and stay within your specifications, GREAT. If you push the intake out of spec in order to do so (hogging it out), then that 20 or 30 cfm is likely to weaken or kill the tuning effect. This will help it push further up in the powerband somewhat, but hurt torque below peak since your max VE will be reduced at and near peak torque due to the weaker intake tune. This can also hurt throttle response and cylinder fill (torque) and mileage among other things. Is that 20 or 30 cfm really worth it to you? If so, I would say that a TPI engine is not what you should be using.

Painful truth is the TPI engines work great when designed and built correctly, with care and attention to detail. That's the only way I will build them. But the are very sensitive to parts selection and modification and need to be as close to spot on as possible to maintain/improve the tune. How well you can do this will show in the final product. This is why TPI engines are unpopular with many, and engines that are untuned like the LT1 and SBC are more favored.

I dont hold it against my TPI engine that it's sensitive. I like a challenge But damn, it's rewarding when it's running good! I'm all for instant gratification, reliability and mileage in one stockish package!

DAREDEVIL 1

Damn, u shure can write good...i wouldnt know how to say all that but i 99.9% agree !!!!

Guest

That must be why 18 wheelers are tearing up the dragstrips all the time, because of all that torque they make.

The tq/hp argument always goes in the same direction, with people making incorrect conclusions based on false assumptions. Go back and visit the physics of the matter.

The discussion of the TPI "theory" is not anything new here, its been around since before this board officially became thirdgen.org. The formulas originate from DECADES ago and are also nothing new. To me, this is just a rehash of old topics, that ended up with the same end... theory and discussion, with no physical results tying the two together. Thats why I said theory is nice, but impractical and to a degree somewhat useless. Until you address the tiny runners and tiny CSA of the intake base, not to mention the complete lack of transitions in all the parts, you are still not going to net much HP or TQ which is what we are all after.

DAREDEVIL 1

DUDE,,,now your very far off...can u go anywhere with 500 Hp in your camaro pulling 30 tons ???

Guess not, but a 18 wheeler can , and u know why,,,,,,because of tourge !!!!

Every dyno messures the tourge of an engine and the HP # u see is calculated by the dyno..this is also why the HP/Tourge always over laps at ~ 5238 RPM...,HP is a mathematical phrase for tourge...which is POWER !!!!
Again, this is getting no where since most here that have no clue what its all about ( ecsept for nice wheels and paintjobs ) want to know things about they have no clue from !!!

NITE !!!!!

OH, AND MERRY X-MAS !!!!



lol http://www.streetfire.net/video/18-w...ing_548262.htm

Guest

Well thank you for confirming that HP is not a useless term, but do you believe yourself or not?

DAREDEVIL 1

U dont speak english well i guess...???

It is useless..but if evrybody would tell u , hey my engine has 405 FPT isn't that cool..then u would say whats that...i need HP !!!
Like most others too.

The reason for stroking a motor is gaining rotating MASS , which in first place is TOURGE !!!! and thast what makes u go wroom wroom !!! got it ??

DAREDEVIL 1

so we can all learn !!!!

http://www.howstuffworks.com/horsepower.htm

mroth2008

great info will be usefull when I start tinkering with my 88

InjectorsPlus

iTrader: (1)

No, that's not what I'm saying.

I am saying that if you want to go fast you need HP in the higher RPM ranges.

Don't believe me, believe reality. I don't see very many guys running 8s with high torque motors with 5000 RPM peak.

Once your moving (torque) you need HP to keep going faster.

InjectorsPlus

iTrader: (1)

Exactly.

Good post.

It's new to me. But I guess if you've seen it before it's old hat.

I'm just tired of threads where people hack away at parts, get a mediocre dyno graph by some dyno that's looser than a $3 prostitute and everyone circle jerks around it. Then use "science" to fit their results. I find it irritating. Science fist then see what the results are. No one ever wants to commit on results or bench mark beforehand.

Maybe it's old in content but refreshing in approach.

InjectorsPlus

iTrader: (1)

Like all urban legends has a grain of truth. problem is there is no relationship. Once you are moving, and the faster you are going, less torque is required to move you and HP makes you go faster. Short, but that's the point.

Do you realize how rare it is go get engines over 100% VE in a NA engine? Engine Masters does it on occasion.

I'd love to know your definition of "efficiency" there is no industry accepted term, and when you ask 10 people, you get 11 answers. Not being an ***, this is a question I have asked for a long time, just looking for an answer, while pointing out it's not an accepted term.

As far as port speed, optimum port speed is 345FPS. You can manage port speed with CSA but faster isn't always better. The port will lock somwhere around 600 FPS.

Again, it is very very rare to get over 100% VE. ESPECIALLY in a TPI.

Good point. The issue is, is this a result of design change? Was it hogged out or hacked out? That's why I always ask the question when people start doing this stuff. So what, you picked up CFM, what happened? Why?

Right. I'll go with that.

Again, I'll go with that too. Too many people slapping "cool" parts together and having no idea why and don't understand enough to get optimum results.

It has its place.

InjectorsPlus

iTrader: (1)

How much torque do you think this guy has?

http://www.streetfire.net/video/ford...hp_2096659.htm

dhirocz

iTrader: (2)

efficiency-here Im referring to maximizing flow quality without a loss of velocity due to size or turbulence.

madmax, where are the lack of examples? If you look at the info, there are plenty. The problem is this theory is rarely put into practice, compromises are always made. Thats when all goes to hell. Like I said, these are VERY sensitive to parts selection and porting. But somehow I doubt the engineers and the aftermarket are that far off base. Even with their financial compromises in design and production they still produce rather decent parts.

As far as 8 second quarter miles, thats absurd. Thats not realistic. Anyone who wants that opened the wrong thread.

As far as going over 100 % VE, yes I realize its rare in a NA engine. Most are in the 75%-90% range. Tuned ports ARE capable of going over 100% VE though. Ask a good tuner. One factor in torque production is cylinder fill which is why the ram effect in the TPI makes such awesome torque.

There is a direct relationship between torque and HP. Look at some calculators that factor one into another with rpm.

These are old principles, yes. They are also the same ones put into the TPI intake as well. What hasnt happened yet though, is application of these principles in modification and improvements. Since it can be tedious, most would rather go a different route, or ignore the theory, and when things go wrong, blame the parts and not their lack of understanding and research.

DAREDEVIL 1

Best about intake i ever heard !!!!!
this was in an other thread.

Re: Trying to upgrade my 350 TPI Engine
IF you run the same intake heads and cam on top of a 383 vs 355, the two are likely to make the same hp, but the 383 will make more torque. The 383 will just peak few hundred rpms sooner than the 355. If you go 383, you should go 5-6 deg more duration on the cam on both lobes to take advantage of the cubes. The increased stroke will require more duration. As long as the heads/intake dont restrict the air flow a 383 needs, you could see more hp but its not surprising to see same.
Yes cubes make more power but you need the induction package to use the cubes. I've seen this happen on a few LT1 builds... some of the "stage 3" 355 packages are equivalent to "stage 2" 383 setups...roughly same hp, but less rpm for the 383 and much more torque.
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1989 Twin Turbo IROC-Z
"Twin Turbo 401 Buildup Pics "
"FQuick Garage"
9.86 at 141 mph 14psi, pump gas street tune

InjectorsPlus

iTrader: (1)

OH c'mon your'll killing me. What's with this "STAGE 1,2,3" crap.....

There's no industry standard, it's made up by manufacturers.

hear that? (thump thump thump) that's me beating my head against the wall.

As far as the 355/383 comparison, who put up better times?

Doom86

Great thread.

It's always good to see someone try to make sense of theory, even if it isn't perfect. There is no such thing as perfect in these regards IMO. If there was such a thing there would be no competition, we would all have "The One" motor, ect.

DAREDEVIL saying Horse Power isn't important because it's found using Torque is like saying Torque isn't important because it's found using Force. Should we all start measuring joules at the crank? If this doesn't make sense we won't get far into that discussion.

InjectorsPlus

iTrader: (1)

Just thought of something.. how would 1000 ftlbs of torque work at 12 hp and 4000 RPMs?

That's one hell of a tractor, but I wouldn't want to race it.

Guest

I'll agree with that.

Part of the problem with the formulas is they require some resemblance of adhering to the caveats, like a proper sized and placed plenum, runners with reasonable changes in area and direction, and the right balance of parts from start to finish. That often requires a lot of money, that most of us are not willing to spend. Cant blame em. The siamesed runners and bases kind of ruin the plenum theory so things kind of go out the window on those setups. They would be very difficult to model mathematically. Its kind of a test it and see what happens thing. That is most of what has been posted here as far as results and the issues with the TPI and the theory are pretty readily apparent in those results if you're looking at them.

What TPI really needs is bigger runners (getting ASM to make some with 1.875 ID would be nice) and an entirely different base. Something physically higher, with a lot taller runners at the head, and larger outlets at the runner end.

Guest

The examples you refer to follow the practice and compromises you mention. Thats why I said what I did.

I'm not in agreement with that. A good study of the runner size, shape, and direction between a TPI head and intake vs a LS1 head and intake should show you a very significant issue that nobody is touching on. Well... maybe almost nobody. You may have even mentioned it without realizing it when you said "without a loss of velocity due to size or turbulence." I realize GM was not working with a "clean sheet" design on the TPI like they did with the LS1, but they could have done a lot better. As it is, the crossfire is not all that far off from the TPI and we all know how well those do in relatively stock form. At the cost of welding and porting, it would make more sense to cast an intake like the crossfire guys have now done.

dhirocz

iTrader: (2)

I wouldn't trust any dyno that said that, lol!

That's 761.6 HP. It's impossible to have 1000 ft/lbs and 12HP at 4000 RPM. Like I said, they go hand in hand. Play with this and you can get an idea why:

http://www.wallaceracing.com/HP-TQ-RPM%20Calc.php

dhirocz

iTrader: (2)

One of the compromises that I was referring to was creating an 'intake up' tuned system. This was by no means a system created for a sole purpose started from scratch or there would also be oval port or round port TPI heads for example. However, that would require a change in valvetrain geometry, since two 1.5" round passages next to each other would push the runners in the heads into the pushrods, and I'm sure GM was fine with loosing a little to this. In a perfect world, the round shape of the runners would either extend into the heads for a more consistent cross section (since the heads are also considered in runner length and are about 5.5" of it), or the shape of the runners would not be round.

I'm sure the thought crossed the engineer's minds briefly, and maybe the exec's, but for what most people were looking for at the time out of an engine just coming out of the smog era with the bean counters watching, investing several times more into doing that to improve an engine when they already deemed the finished product adequate for it's purpose in the end was probably a waste of money from a corporate standpoint. The factory makes compromises too. That's why we have this board, to improve on what GM didn't do.

When I was referring to them not being far off base, I was referring to manifold theory, not the design. You dont have to be a rocket scientist or an automotive engineer to know the TPI system could use alot of improvements. In comparison to the LS1, we now have a better idea of airflow dynamics thanks to computers which were still in their infancy when the TPI manifold was designed. We also have better and cheaper casting processes that yield a better product. I'm sure there are more reasons, but things are improving as technology gets better. Look at the FIRST. If GM was able to make the TPI intake like the first in the mid 80's, would we be having this conversation?

1989GTATransAm

iTrader: (3)

"What TPI really needs is bigger runners (getting ASM to make some with 1.875 ID would be nice) and an entirely different base. Something physically higher, with a lot taller runners at the head, and larger outlets at the runner end."

Rumor control has it that something just like that is under construction.

dhirocz

iTrader: (2)

I'd be interested in your idea of using mandrel bent aluminum bends to make runner tubes. I've found some that are 1.62 ID, 1.74 ID, and 1.875 ID 18 guage elbows. Mind sharing your approach? I've cut up some doomed runners, so far I plan on reusing the top flange after working it on the bridgeport and using aluminum bar stock for the lower flanges since they dont leave much room to work with.

I've even pondered the idea of building a new base that turns oval instead of rectangular at the head port entry, and modifying the heads into an oval port. I think I'd rather use the energy and expenses here on a big block with oval port heads though.

1989GTATransAm

iTrader: (3)

The factory flanges "may" work for the smaller diameter tubing if bored out. However I am using 2" tubing with 1.875" ID, 3" Radius and this requires new flanges to be made. The upper flanges that bolt onto the plenum are already done.

I am currently waiting to get the intake manifold/base back from the welder. I am having a lot of weld added so that I can get the CSA that I want in the runners. Then I will have the 4 lower flanges made. I am debating on whether or not to post pictures of my current long tube runner project as quite a few people think I over do it. I do get incoming flak.

dspencer24

iTrader: (3)

yeah you over acheiver lol looking foward to seeing your results in the future!

Guest

I think you missed my point. A one off runner does not really help many people. I considered it over 2 years ago and threw out the idea for numerous reasons, one of them being the poor execution of the base and no good way to deal with it among other trivial things like having enough space to attach them to "stock" parts.

I dont think an oval port is going to do anything good, especially for the amount of headache that would create. It would make more sense to stick with the rectangular shape and carry that all the way to the plenum.

1989GTATransAm

iTrader: (3)

"A one off runner does not really help many people"

I would consider it a prototype to prove whether or not the concept will work. I plan on having a round port all the way from the plenum to well into the base. Then it will transition from the round port to the rectangular port to match the AFR 195 head entrance.

The CSA will be maintained at 2.76" sq. right up to the head entrance. Yes the base will have to have a lot of welding for this to occur. Maybe $200 worth of welding. If the concept fails then I will resort to a SuperRam plenum setup and go with the 4th and 3rd haronic waves and still retain the same CSA. I also hope to get a lot of "inertia" from the column of air in the runner.