quadgoat

iTrader: (1)

Hey guys, I posted this up over on stealthram.com as well and I've gotten some help there, but I figured I'd throw it up here as well. Thanks in advance for your help, and sorry it's such a long post.

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Well, while I was home for spring break I finally got a chance to dyno my Trans Am. A friend of mine works at a local shop which just recently got a Mustang dyno installed so I was able to work a good deal for some dyno time on a Saturday. I was hoping that with my combo I would come close to 300 WHP and a little over 300 WTQ. Granted I would have loved to be a little over 300 HP but I didn't want to get my expectations up too high. I was also hoping to do some high rpm/WOT tuning, although I don't have a wideband set up yet. Anyway, long story short, my best peak HP number was 190 HP and peak torque was pretty consistently about 320 ft. lbs. Basically the torque curve peaked pretty close to where it was supposed to based on the graph Holley has on their site for the topend kit I have, but once the torque peaked it just dropped off and the car didn't really pull any more, although it sounded just fine once I smoothed out some hiccups in the fuel map. Unfortunately I don't have a good graph to post right now because we didn't complete any of the high RPM pulls that we ran. I hit peak torque at about 3500 RPM, and the only other thing to note was that after a couple high RPM pulls the dipstick had pushed out of the tube a bit and was squirting oil out. I don't have a conclusive answer on this, but is it quasi-normal to have this sort of thing happen at high rpm when the engine has gotten fairly warm (220-230ish degrees) or could this be a sign of an internal engine problem (ring not seated properly, resulting in blowby) that could be contributing to my low HP #'s? I know that my fuel map isn't tuned perfectly yet (I'm using a Commander 950 system), but the car really runs and sounds pretty darn good at this point. The only other odd thing is that if I bump the timing up (I'm running 30* at 6000) the engine starts cutting out like crazy. I feel like I should be able to run more timing than that though?

Sorry for the long post, but I'd really appreciate any and all input you guys can provide. I'm pretty disappointed in how this turned out and I'm hoping to pinpoint the problem. On a happier note I think I got rid of my last HSR oil leak by double-gasketing the distributor! :P I've been asking the guys over at Chevytalk for advice concerning my dyno results, but I thought I'd pick your brains over here too. Thanks again!

-Paul

Specs. on the Holley SysteMax II package:

This is all on a 350 bored .030 over with a CR of approximately 9.3:1 or so. I went lower than Holley's recommended 10:1 because it is mainly a street car.

CAM:
Intake valve gross lift/duration: .490"/290°
Exhaust valve gross lift/duration: .490"/297°
Intake valve duration @ .050": 235°
Exhaust valve duration @ .050": 240°
Intake valve lobe centerline: 107°
Lobe separation: 112°

HEADS:
Holley Aluminum
2.02/1.60 valves
68cc chambers
184cc Intake Runners

Holley engine dyno graph:

SysteMAX dynamometer tests document 425 HP @ 6150
RPM and torque of 425 ft./lbs. @ 4250 RPM.

Grim Reaper

Your compression ratio is too low for a cam that big. Also, a cam that size can easily handle 36* without detonation. It "bleeds" pressure and can tolerate more spark.

REALPOWER

I agree. You should be running about 10 or 10.3 to 1.

quadgoat

iTrader: (1)

So you guys are saying that I'm making 100 HP or so less than I expected due to the fact that I'm running 9.3:1 instead of 10:1 with this cam? 7 10ths of a point of compression will really make that big of a difference? I played around with Desktop Dyno some (I realize it's just a simulation and not necessarily that accurate) and I changed compression ratios around from just below 9:1 up to 10:1 and the changes didn't alter estimated HP output as much as you're suggesting. I feel like there's another answer, but I obviously am not sure lol. I really appreciate the input, and keep it coming! The more I think about it the more I'm thinking that this engine may be coming out this summer, after only being in for a couple summers and 5,000 miles or so

-Paul

AlkyIROC

Do a compression test and a leakdown test. Without knowing what's going on inside the engine, everything else is just a guess.

What's with the graph saying 425 hp?

xpndbl3

iTrader: (5)

that graph is off holley's website for their head/cam package for the engine. it's not his dyno graph.

quadgoat

iTrader: (1)

Yep, you got it, sorry I wasn't clearer on that

My plans for as soon as I get home from school are to recheck TDC and verify that my timing tape I installed when I built the motor is accurate. After that a compression and leakdown test are the next on the agenda. Just trying to collect some other thoughts, but I agree, I've gotta find out what's going on inside, and that issue with the dipstick pushing out at higher RPMs has me wondering/worried....

AlkyIROC

What kind of crankcase vent system do you have?

Solid sealed off valve covers
Typical PCV system
Open breathers in both valve covers

Dipstick being blown out means there's too much pressure in the crankcase. Anything other than solid covers will allow excess pressure to vent off. I use a header evac system myself to pull the pressure out of the crankcase with the exhaust.

That dyno graph should also be flywheel dyno. My guess is that you might get 300 to the wheels so you're still off about 100 hp somewhere.

Lots of things can't be accounted for with dyno software. Ignition timing, base and total. Spark plug gap. Jetting but you're playing with EFI fuel curves so you need to account for injector sizes and fuel pressures also. Fuel supply, maybe there's just not enough fuel reaching the injectors.

ljnowell

Something to take into consideration, the mustang dynos are very unreliable. I once saw a guy with an LS1 dyno 225hp. The same guy dynoed 310 a week before and 308 a week later. Dont always trust what the mustang dyno says.

Marc 85Z28

iTrader: (3)

Not unreliable, just different. Those 300+ pulls were made on a completely different dyno, like a DynoJet.

quadgoat - Where the dyno operators complete morons? Most can offer suggestions for tuning based on what results you get. A dyno graph can tell A LOT about want an engine needs and when. Can you please post yours?

Lo-tec

I would suggest using a wideband O2 while dynoing...will point you in the right direction for a/f ratio. I tried tuning my DFI by seat of the pants and was at 10:1 WOT and it felt good. Got fixed easily when I put it on the dyno with a wideband and saw how fat it was.

Also, looking a holleys chart, your torque peak is low by about 800rpm.

Grim Reaper

My comment was on how to optimize your tune. 7/10th of a point, combined with running significantly lower spark than your engine can tolerate (and improper fuel mixture) can cost a significant amount of power.

Also the points about other mechanical problems (do a leak down with compression test) and dyno's in general are all valid as to why you may not be seeing 300RWHP. Even "dyno run vs dyno run" on the same dyno but different days can result in different readings.

FYI, I helped tuned a guy with a Holley Stealth Ram on a ZZ4 with a much milder cam than yours (the exact specs I forget at this time but it was close to 224/230 @ .050). He pulled close to 270 RWHP. Which would be "in the money" with your engine specs. And no, it was not a Mustang Dyno either.

But between the tune, compression ratio (I would have gone with 10.5:1), possible mechanical issues and dyno operator error, you may be loosing your 100 RWHP. I believe with the proper mixture and getting your spark to 36* you may find another 35-50 RWHP. 6* of spark is pretty significant when it comes to tuning.

quadgoat

iTrader: (1)

I'm running a PCV with the line hooked to a port on the throttle body in one valve cover and a breather in the other valve cover.

Correct, the graph I posted is flywheel HP from Holley's site, I was hoping to hit around 300 RWHP, probably a little below that, so I agree, I'm missing 100 HP somewhere

No, the dyno operator isn't a complete moron lol, he's actually a friend of mine I was in at the shop on a weekend and he came in and ran the dyno for me as a favor and gave me a very good rate. Basically my intentions were to see what numbers I put down and try to fine tune the top end/WOT portion of my fuel map. I only did a couple high RPM pulls and we didn't actually complete them (let off before we reached the specified MPH on the dyno) so I didn't get graphs from those runs. When I'm home for the summer I'm going to go back over and try to look at some of the other graphs that are on the computer and see if I can gather more data from them.

Lo-tec:
I'm planning on installing a wideband O2 setup in the car this summer, so that will help me diagnose what's going on as well.

Glenn91L98GTA:
Thanks again for the input! Like I said, I'm planning on a compression & leakdown test as well as checking my timing tape for accuracy. I would also love to throw more timing at the engine, but it sure doesn't like it one bit if I try to do that!

I realize I've left a lot of unanswered questions, and that I'm not being all that helpful with my replies and I'm sorry if that's frustrating to you guys, but I don't have the answers to give at this point unfortunately. It's frustrating being stuck at school in NY when the car is at home in ME! I really appreciate all your patience and the ideas that you've been giving me will be a HUGE help once I get home and can start troubleshooting this thing! Thanks again and keep it coming, you guys are great!

-Paul

REALPOWER

If your using stock pistons, your running even less compression than that. If you did not deck the block, even lower than this.

REALPOWER

Also a compression check doesn't mean much except comparing one cylinder to another. My motor has so much duration and overlap that it doesn't produce more than 180psi. A leakdown is what you should be looking at.

quadgoat

iTrader: (1)

I'm not using stock pistons. I bought a complete forged, balanced bottom end kit with flat-top pistons from Powerhouse and they said it would yield 9.7:1 compression with 64 cc heads and 8.6:1 compression with 76 cc heads. I did some calculations and figured my setup at around 9.3:1 based on those numbers. I had the block checked for truness on the deck, but didn't actually check measurements with the pistons installed, thus I didn't get it 0-decked or anything. I also realize that a compression test is really just for comparison, but if I find a cylinder or two that are significantly lower than the others then that would be an early clue as to which cylinders are giving me trouble (if any). A leakdown test is my primary priority though

AlkyIROC

I pumped a bunch of numbers into a calculator and came up with 9.32:1 so your calculations are pretty close.

Bore = 4.030
Stroke = 3.48
Head cc = 68
Piston Volume = 6cc (flat top pistons with 2 valve reliefs)
Deck height = -.030 (how far down the piston is in the cylinder at TDC) - average guess if block wasn't decked
Head gasket thickness .034 - guessing

If the block was zero decked, compression would only increase to 9.97:1. Decked and 64cc heads would put it to 10.43

What altitude are you at? What octane is being used. As mentioned above, bump up the timing to 36* and try again.

Since you have an open breather on one of the valve covers and you're still blowing a dipstick out, you must be producing a lot of crankcase pressure. A compression test will show a bad cylinder if you have some broken rings. A leakdown test will also show this plus any bad valves.

When I had some broken rings I kept blowing my dipstick out also. A long spark plug boot over the dipstick solved that problem. The engine has been rebuild but I still have the boot on the dipstick just in case.

REALPOWER

piston volume should be -6cc for valve reliefs.

AlkyIROC

Depends on the formula. Positive number for piston volume is normally considered a relief. Negative number is a dome. I know what you'r thinking and I think it should be that way also.

It's not so much as how much area it displaces but how much area it adds or reduces the combustion chamber.

6cc valve reliefs are adding 6 more cc to the combustion chamber size so it's considered positive.

My combustion chambers are 119cc and the domes on my pistons displace about 49cc so my piston volume is -49cc

ljnowell

Different, like a dodge?

I have to say, that when two seperate dynos are within 5-15 hp of each other and then a third one is about 85 hp off, its unreliable. This isnt the only time I have seen, or heard of it with mustang dynos.

quadgoat

iTrader: (1)

I'm at sea level and running 93 octane fuel in the car. I would love to give it more timing, but every time I do the engine starts cutting out. Not like you hear it detonating or pinging or anything, but it starts cutting out violently. It's done this since I put the EFI system on. With the carb I ran about 8* base and I think it came in to 33-36* total and it was fine, but I can't give it that much timing with the EFI for some reason?

As for the pressure in the base, I am definitely concerned about it, and will be looking for some answers from the compression and leakdown tests. I'm hoping it doesn't come to pulling the engine, because it's only got 5000 miles or so on it, but if it comes to that, so be it! Also, I've never seen the dipstick pop out and oil come out of it until the dyno run. Even drag racing and shifting at 6000 RPMs last summer I didn't see that happen at all. Just something to note, don't know if it's significant or not. But yeah, there's something amiss that's causing this, I'm just trying to convince myself that I *might* not have to tear down the bottom end of my engine

As far as the dyno thing goes, you need to understand how differently a Mustang dyno works than a DynoJet or other similar inertia dynos. A Mustang dyno uses an "eddy current" to simulate real-world loads on the vehicle being tested. A DynoJet simply consists of big heavy rollers and it calculates how quickly a vehicle can accelerate these rollers. The way the two dynos work results in different numbers being produced for the same car. A Mustang dyno tends to be more useful to people doing tuning and such because it can hold a vehicle under load just like it's actually driving down the road, whereas a DynoJet can't really do that because once the rollers are spinning it doesn't take as much energy to keep them spinning at a certain speed, so the car isn't under the same kind of load it would be on the street. It's pretty much agreed that DynoJet dynos will show you higher HP #'s than a Mustang, but that's not necessarily bad. Mustangs tend to be more repeatable, and in the end the real prize is having spent some time on the dyno, made some changes, and come away with more HP than you went in with, no matter what the actual number is.

Anyway, sorry for another long post, just thought I'd throw out some info on the dyno situation that I myself just learned recently. By the way, my friend with an '01 Z28 6 speed ran on this dyno a few weeks back and put down 310 HP and 321 ft. lbs of torque. The only mods to the car were an intake lid and an exhaust. I was pretty impressed, and I also know that the issue is with my car, and not the dyno most likely

Bowtie67

On a 350 engine and that cam, I would believe you will never be happy with it. Low Compression with this big a cam is going to be a big hit in performance regardless of what Desktop Dyno says. On the same note try plugging the XE276 and the XE268 cams in and see what your numbers are. As a daily driver and having proper tourque when you need it on the road you will be major disappointed. This cam would be much better suited at full throttle. With the lower compression I would recomend the XE268 Compcam and a little higher CR then I would go with the XE276 cam. I ran a 286 Roller cam in a 350 that was great in the lowend or all out with 10.2cr on the highway during normal cruise it had no great power at all unless I really dropped down the gears. On a dyno of my current engine 413ci sbc w/10.2cr, 650cfm carb and the XM276HR cam at the rear wheels is 340HP & 350TQ that is basically about 430HP at the Flywheel.

quadgoat

iTrader: (1)

UPDATE!!!!!!!!!!!!!!! Since the last time I dyno'd the car I've replaced the distributor, installed a 255 lph Walbro in-tank fuel pump, and installed an Accel 300+ digital ignition system. I've done a few other things too, but nothing that should affect how the engine runs. Well, today I dyno'd it again, using one of Holley's base maps right out of the box with no fine tuning I put down 295 RWHP and 310 RWTQ!!!!!!!! I'm stoked! I know I can pull a little fuel out of the base map and maybe give it a touch more timing to boost me up to 300, or possibly a little over 300 HP!! My biggest issue was the old distributor I had in it was JUNK, the new fuel pump helps out quite a bit too, and I'm sure the MUCH hotter spark from the new Accel box and coil can't hurt either

Here's my dyno graph:


-Paul

89gta383

iTrader: (5)

You are still too low on the compression for that cam.

I would pull the heads off and have them milled to get your compression to AT LEAST 10.75:1 with that cam. Run a 160* thermostat and turn your fans on early with a good part throttle tune and you should have no problems running every day with that car.

It is your car and your decision, but you are leaving power on the table by not running the correct combo for your part selection.

Lo-tec

That looks alot better. What was the a/f ratio, and any reason you didn't pull it up past 6K?

quadgoat

iTrader: (1)

We didn't have the wideband on it, but my narrowband was reading fairly rich all the way up. We didn't pull farther because it looked like the HP curve was getting pretty flat, but this summer after I do some more tuning I'll be doing some higher RPM pulls

grumpyvette

Id agree with those that say 9.1:1 cpr is WAY TO LOW for that cam, 10.0-10.5:1 cpr would really wake that engine combo up significantly

you might want to read thru this thread and insert your cams timing into the calculators provided

https://www.thirdgen.org/techbb2/sho...hreadid=339026

theres nothing wrong with the (CAM) (below)

http://www.crower.com/misc/cam_spec/...00471&x=22&y=7

in fact ive used a very similar cam to get outstanding results in 11:1 cpr 383 engines matched to a drive train with a high stall converter and 3.73-4.11 rear gears, without getting into detonation with aluminum heads (92 octane) and YEAH! before you ask, it REQUIRES a tight quench (.038-.042) a pollished combustion chamber,aluminum heads, 180 degree t-stat, great cooling,high capacity oil system, and a finely adjusted EFI, with a knock sensor, and a well controlled ignition advance curve you can program, and true 92-93 octane fuel to run that cpr without getting into detonation, but the power curve IS WORTH THE TIME AND EXPENCE