project89

iTrader: (1)

i belive ur making alot more power then u belive u are. turbo355 ran a bone stock tpi with small port/small valve truck heads and layed down over 800rwhp with a pair of stock gran national turbos.

ppl have moade over 1000 hp with the old style banks log headers i dont see why ur header would be an issue.then again u are running a single t4 turbo, and iirc the banks manifolds were twin t4

if u want to get a good idea if ur manifold is holding u back hook up a boost gauge to the ex pre turbine and compare the presure to boost pressure
1-1 ideal
2-1 ratio is acceptable
3+-1 is getting up there

Street Lethal

iTrader: (16)

No, Marty's engine made 554-RWHP w/the stock Grand National turbo's and those truck heads which had 1.72"/1.50" valves, but it wasn't a bone stock engine though, he was running 1.6:1 rockers, and a Comp High Energy 268 camshaft with the Tuned Port Injection setup, and even that had a little work done to it from what I was reading. ZZ3Astro, in my opinion that turbo manifold isn't the problem at all...

project89

iTrader: (1)

reread his build thread later in the thread they dynoed over 800

Street Lethal

iTrader: (16)

Don't have to...

"That's when Marty got his next great idea. The replacement motor had 150,000 miles on it and came from a guy who had been using it in his truck to commute for the last 60,000 miles. Marty was ready to get back to his junkyard roots with a little science experiment: How long until the used engine grenaded? Instead of rebuilding it, Marty just dropped it in including the original 991 truck heads with the 1.72/1.50 valves simply because they were free. "After all, the Buick GN was doing it with 1.71/1.50 valves; why not?" says Marty.

That engine made 554 at the wheel on Shelley's Automotive dyno using two bone-stock '87 Grand National turbos that he bought used for $400. The only nonstock parts of that combo were 1.6:1 rockers and a Comp High Energy 268 cam swap. The small cam allowed him to pass emissions and get some tags to drive it on the street. "I got sick of trailer queens," he says. At the strip the car ran 10.23 at 133 with 20-22 pounds of boost, and then Marty sprayed it with nitrous. "We couldn't kill it; it wouldn't die, so it needed nitrous." Using parts from a carbureted plate system, Marty plumbed a 90-shot about one foot before the throttle body. It made 616 at the wheel and hit 24 pounds of boost. At the track it carried the wheels and ran 9.75 at 141 mph. "What a good feeling," he says"....

http://www.carcraft.com/featuredvehi...d/viewall.html

With the small truck heads and two stock GN turbo's;

554 w/out nitrous...
616 w/the nitrous...

ZZ3Astro

Marty's engine was definitely milder than mine. My cam is 224/224 .530"/.539" hydraulic roller on a 114. Not only do I have a bit more duration and lift, but the 268 has a 110 lobe separation. My cam is much better as a turbo cam. My heads are pocket ported aluminum L98's so they are at least as good as Marty's truck heads did.

I'm pretty sure I'm not wrong on the power it is making. I just recently dynoed at only 346 rwhp (before fixing fuel delivery and ignition issues (ignition not a factor in that dyno session though)). After those fixes, the car does run better but not 150 rwhp better. In theory with 22 psi it should be making over 600 rwhp with my engine - assuming it makes about 325 crank hp NA. So it should feel more like 250 rwhp better at 22 psi!

I'm all rigged up this morning to test exhaust manifold pressure. Results coming...

Street Lethal

iTrader: (16)

IMO, if your reading 22-psi of boost pressure then your exhaust manifold is fine, and is definitely not a restriction. I agree with project89 in that we tend to get used to this power, and sometimes a slight increase will feel like nothing at all. It's hard to reread the entire thread because I am at work, but what were you air temps during these testing comparisons? What kind of shape is your transmission in, is it rebuilt, or the stocker w/high mileage? Which converter are you running. I can tell you that at 15-psi, my air temps were very high when I ran the stock TPI setup, but were then reduced substantially once I siamesed them, w/the results being far more better at the same boost pressure...

ZZ3Astro

As measured from the driver side manifold at cylinder #7, I am seeing about 50 psi exhaust pressure at 20 psi of boost. This puts me at about 2.5:1. Is this enough to affect power this much?

DIGGLER

iTrader: (1)

got room to go up on your hot side a/r?

ZZ3Astro

It's a .96 turbine so not really, but can't be the turbo in this case anyway. I don't think Precision would send me the wrong configuration for my build specs. I need to measure the pressure right below the turbo flange. There is a fitting but obviously will be a pain to get to with the turbo mounted. That would give me a good indication if its a restriction at the merge vs the turbo flange (or turbo!) itself.

A friend keeps telling me my wastegate is too small to vent off the excess pressure, but it has no problem controlling boost all the way down to 14 psi. I had to crank the spring adjustment nearly as tight as it would go to see 20-21 psi. I can't see how a larger wastegate would fix this problem because as I see it, excess exhaust pressure at the turbine inlet would just increase boost even more (as long as there was nothing restricting that in the downpipe. However as I am still learning at this turbo charging game, I am open to all input.

DIGGLER

iTrader: (1)

if you are still able to control the bost, i would say the wastegate is fine. if it was too small there should be some boost creep evident? im thinking you could tap into the manifold to get a pressure reading, and then again on the turbo housing and take the difference in readings... this would show you how much the merge/flange is restricting flow. maybe you could modify a couple things to squeeze a $600 t6 bw turbo on there? tee hee hee

sailtexas186548

iTrader: (2)

a .96 AR should be more than enough for 500rwhp, have you checked the obvious like a collapsing intake tube, air filter, restricive intercooler, TB not being 100% open, etc?

what does your exhaust look like once the DP gets inder the car? maybe too much backpressure there

DIGGLER

iTrader: (1)

thats a good point too... where are you tapping into the cold piping to read boost? might be a good check if you could test on the compressor outlet. if boost is quite a bit more there than at the tb you may have a restriction in the piping/intercooler.
you could also try running it without the filter or whatever tubing is on the turbo inlet to rule out collapsing tubing or whatnot.

ZZ3Astro

Definitely no boost creep. I do have a boost spike to 14 psi if I set the wastegate below that, but if it's 14+ then it maintains boost to the setting no problem. That one I can blame on the wastegate size.

I just got finished testing boost pressure at the turbo flange (actually about 1/2 inch below the flange but just as well). I just measured 48 psi to make 21 psi. Good God man, I just spent $1000 on this Precision 67mm that supposedly supports up to 900 hp, I hope I don't have to go buy another turbo!! LOL


Only thing I haven't tested on the cold side yet is the boost at the turbo vs the intake. I will say that I used to run the wastegate directly off the intake plenum but have since switched to directly off the turbo housing (since the PT has a fitting on it) . After doing that, the amount of boost at the intake is virtually the same for a given wastegate spring adjustment. A big restriction in the intercooler would have sent higher boost to the wastegate and resulted in a lower intake plenum pressure at a given wastegate adjustment. However I will measure this next just to rule it out!

Exhaust is 3" straight through to the back. A slightly restrictive bend (non mandrel) over the axle, however I've ran both with the entire cat-back disconnected as well as with only the muffler disconnected with little change. I see about 1-1.5 psi difference with no exhaust other than the downpipe vs the full exhaust. No I haven't measured back pressure behind the turbo.

Cold air is 4" mandrel to the filter. I'll drop the whole thing off and take it for a ride.

DIGGLER

iTrader: (1)

hmm... i was just thinking a pair of 67's would be good for around 1000-1100rwhp. 900 out of a single 67 sounds a bit on the high side, no?
im sure you could sell it and recoup alot of money out of the turbo if you decided to upgrade.

Orr89RocZ

iTrader: (20)

Yeah 67 should do 700 but 900 seems optimistic and only on optimal conditions, meaning right motor cubes and rpms. The compressor map may flow enough at super high compressor rpms at high high pressure ratios but you will never see that on a V8

single 3" is a restriction for 500whp but if thats the best you can get, then work with it. 3.5" or even 4" single would be much better

ZZ3Astro

Right, the billet 67 is very capable of handling 700 crank hp. I'm only looking for 625. Trust me I made sure Pete at Precision knew exactly what I had and wanted. He prefered a 72mm for me but my limited mounting space dictated the 67. He said the 67 was more than up to the task of handling 500 rwhp, but that it (of course) limited my upgrade options should I decide later to go after more. I assured him that would not be the case as my 700r4 is good for 675 crank hp max (per pro-built).

I won't rule out a future upgrade to larger exhaust, but once again I refer to my friend's turbo tpi vette which runs a single 3 and far exceeds my 1/8 mile goals with it.

DIGGLER

iTrader: (1)

you just need to buy 1 more of those 67's and swap a 4l80e in there. it would fix everything. heh heh heh

project89

iTrader: (1)

u are starting to creep into the to much backpresure area.u have a few options

upgrade turbine wheel, hqve the turbine wheel clipped for more flow( will lag a lil more)
better headers ( dont belive u need these)
1.15 t4 turbine housing
t6 turbo time

a bigger wastegate will help bleed off some of the excessive ex presure but its only a bandaid fix not a solution

uve pretty much goten to the point with ur system that ur either happy with it or ur going to spend some money to go faster

and rob u were parially correct marty didnt put down bigger numbers till he swaped to the 487x heads

i know he made over 800 after that artical with the same setup though

project89

iTrader: (1)

twin 67's would be to much, as orr found out his twin 70's were to much.

on the motor he has id place twin 57mm or twin 60-1's on it for a perfect fit

my motor is very close to his and i went with twin 57's good for around 1100 crank

that is of course if he decided to go with twins, if he stays single i think he should have atleast an t70 on there if not a t72/t74

sailtexas186548

iTrader: (2)

check this out, guy is using a 4" ebay IC core, similar issues to you

http://ls1tech.com/forums/forced-ind...explain-4.html

project89

iTrader: (1)

he swaped intercoolers and is having the same issues still.

while i wont say that its not a possibility but plenty of ppl have gone 7,8's9,s with ebay intercoolers.but then again ive used tons of ebay turbos and never had one fail were some ppl have had 2 of them fail in a row.

sailtexas186548

iTrader: (2)

oh yeah tons of ppl have great success with the EBAY units, I was refering to the whole thread really since they have similar issues

DIGGLER

iTrader: (1)

Orr just didnt turn his up enough.

project89

iTrader: (1)

also true though i dont think orr wants to run 23+ psi though, the gn guys have it down pretty good though" use the smallest possible turbo that will reach ur goals"

Street Lethal

iTrader: (16)

Dave, please don't make me embarrass you lol You were entirely incorrect with your first statement and I corrected you, as you clearly stated "a bone stock tpi with small port/small valve truck heads and layed down over 800rwhp with a pair of stock gran national turbos", when he didn't. That is what you said, and it was clearly incorrect. What Marty did after that is completely irrelevant because after that he swapped to 487 heads with 1.94/1.50 valves, and he also stepped up to two TE44 turbo's, which are way better than the stockers, and even that setup was nowhere near over 800-RWHP...;

648 w/out nitrous
703 w/the nitrous

... after that, a lot then changed with his setup. Try again.

ZZ3Astro

Talked to Precision today. They said the smaller opening on the T4/T3 flange is 100% the problem. So I am going to remove the manifold and look at opening that up.

ZZ3Astro

Also, tonight I tested for restrictions in the filter/cold air tube by removing everything from the front of the turbo. No change in anything. The last test I need to do is pressure drop from one side of the intercooler to the other, but we know that isn't the problem. Ultimately I believe this is going to come down to the turbo itself. However I will open the flange per PT's request.

DIGGLER

iTrader: (1)

keep up the good work! i am enjoying this!

ZZ3Astro

LOL.. I wish I could say the same!

project89

iTrader: (1)

even if u open up the flange on the header the inlet to the turbo is still the same size, u wont accomplish anything really

i do have to ask is ur turbo manifold a t3 or t4 flange?

iirc
t3 = 2.25 inch pipe
t4 = 2.75 inch pipe

or it may be
2.50
3.00

Orr89RocZ

iTrader: (20)

Correct, I didnt turn my setup up enough to really shine but I dont want to run that much boost. I want to keep at and under 20 if possible on pump gas, so I went with larger heads/cam this year to make the 70's work better for my setup. The twin 70's were too large for the motor it was working with. Small heads/cam, mild boost range really fit the 60's well. Now 70's will fit my setup well

ZZ3Astro

The manifold is a dual pattern flange. It's probably somewhere between an T3 and T4 opening size. You can see the carbon deposits outline the difference between the manifold and my ebay T4 turbo. The Precision turbo might be a bit bigger (not sure how closely they stick to exact dimensions on the inlets.

The 48 PSI pressure reading was taken from right here. See those two hex pipe plugs at the bottom? I took the front one out and measured there.

The tube coming up in the center is the crossover. It's a bit tight right there. The wastegate return isn't connected in this pic because the downpipe is sitting lower than when bolted up. Note the three broken off T3 bolts!

project89

iTrader: (1)

ok in ur case opening up the flange to the t4 dimensions will help, im just not sure how much. id open up the flange so it matches the turbo inlet then take readings again. if u can get the back presure down hp will go up.

just out of curosity what size wastegate are u using? looks like a 38mm unit

DIGGLER

iTrader: (1)

could you tap the turbo housing so you can check boost after the flange? if it would be an easy thing to do, i would consider it.

its still looking like you need a larger a/r, imo.

ZZ3Astro

Yeah I could but I have too much money in this thing to drill holes in it. As it is now, I can get them to swap the turbine housing if needed. Wastegate is older than the car and I believe a 38mm. I agree with Diggler that this is ultimately going to come down to the turbo itself and maybe the larger a/r is the answer.

As for opening up the flange, I think it wouldn't be too bad of a job with a plasma cutter. At this point its the easiest option, followed by changing the a/r. After that it becomes a turbo replacement issue, which automatically mandates a new header to relocate everything. Since I'm within several PSI from cylinder #7 to the bottom of the turbo flange, I believe it is safe to say the issue is not the turbo log. I just can't see that 1/4" on each side of the flange making a 20 psi difference. If it does, it will be yet another huge lesson in turbocharging for me!

Orr89RocZ

iTrader: (20)

Manifold design has alittle to do with the back pressure as well so improvements can be made in that area but you would be looking at redoing everything and starting to move away from a budget setup.

Turbine size and a/r can have big changes on the pressure too. But running a .96 a/r is already big enough for 500+ whp so not sure what the deal is. Maybe its a TPI air flow harmonics restriction?

I'm not sure how much the flange will hurt performance, but definately will be some flow gains there so opening it up to T4 size will increase spool time due to more flow and should decrease some backpressure but I doubt its gonna be more than 10 psi. I could be wrong but I just dont see it.

Street Lethal

iTrader: (16)

This is exactly what I was referring to above. Not sure how ZZ3 is obtaining his boost pressure reading, but if it is reading 20+ psi then his exhaust manifold and turbo are not the problem. I asked what his air temps were earlier running that much boost with the TPI restriction but didn't get an answer. Again, if the boost pressure is there, if air temps are low, and if the fuel and spark supply are adequate, then I would seriously look into either the tune, or the transmission....

project89

iTrader: (1)

he is at more then a 2 to 1 ex presure vs boost presure ratio thats the issue, cant get air in if u can get it out.

and i cant belive nobody asked but what turbine wheel are u running?
that has a whole lot to do with as well
t4 .96 ar with a p or q trim wheel is a huge difference

opening up that flange to a t4 dimmension will also help, should speed up spool time as well and since u know its a restriction since its smaller then the turbo inlet start there

Orr89RocZ

iTrader: (20)

he's got a PT-6766 so it has the 66mm, 76 trim turbine wheel. Thats bigger than P trim which should do 500whp atleast.

project89

iTrader: (1)

thanks not up on the pt turbos so wasnt sure what size turbine he had

turbine wheel is big enough, ur flange opening is going to be the restriction or atleast part of it

Street Lethal

iTrader: (16)

Again, you are wrongly correlating this build w/Marty's and your own. Exhaust back pressure highly depends more on engine speed, and less on engine load, so you want a healthy combination of both when it comes to pressure pulse tuning. Dumping the whole exhaust won't fair much better. You don't just throw a turbo on because of a particular map, there is more to it than that. He is not running a high revving small block, not to mention the Tuned Port Injection as well as the exhaust turbine alone are more of a restriction than anything else. Incidently, my stock Grand National should have a ratio between 2:1 to 3:1, are you saying that I won't see 500-RWHP because of it running a bigger turbo...?

ZZ3Astro

Temps are ok. I had to tilt my intercooler to less than optimal position for air flow so I can't compare it so well to the old engine/turbo. That combo was usually less than 5 degrees above ambient at the end of a run. This new turbo I routinely see around 100F temps. That is measured just ahead of the throttle body. I could probably reposition the intercooler back against the radiator now (with the cooler weather) and my guess is it would also maintain the same +5F ambient.

My original config was no fog lights/trim and the center of the bumper behind the tag mount was cut out. Now I run the full stock fog light/trim/tag bracket, plus the intercooler is tilted forward at the bottom so that more air can get to the radiator. It's a large intercooler though and seems to do a reasonable job even with the reduced airflow. I haven't really looked at the air temp in this recent cold weather other than casually making sure the line on the datalog doesn't have an unusual spike during boost. I'll try and drive it tonight since it's in the 40's and see what temps are doing.

daverr

iTrader: (1)

Whats your back pressure ratio at 14psi of boost??????

Have you checked for leaks on the coldside???

Have you checked for pressure drops between the compressor outlet and intake manifold???

Orr89RocZ

iTrader: (20)

As long as your fueling issues seem to have been solved, take it to the track if possible or put it on a dyno and see what it does. It may make more power than you expect

ZZ3Astro

I was going to dyno it today but after thinking about the exhaust manifold leak on #2 I decided it would be best not to keep running it that way. With 50 psi of exhaust pressure it may already have etched the manifold or head. Hopefully not. When I get it back together I can dyno it. My butt dyno is calibrated quite well and if it is any faster I can get a pretty good idea of what the current hp is compared to the opened up flange 'fix'. Yes I'm skeptical.

Coming off starting tonight.

DIGGLER

iTrader: (1)

i know it sucks for you, but i feel like im learning something here. lol

ZZ3Astro

K I found the problem with the leaking manifold. Holy Cow!! The two exhaust bolts for #2 were loose. One showed threads between the manifold and washer!! The other was still touching. I shined a light at the copper gasket and it lit up the inside of the manifold.

This is amazing to me. I have 48 psi of exhaust backpressure between the engine and turbo, yet less than three inches away the manifold is so loose I can move the gasket back and forth. And they expect that problem to go away with a little port matching to the turbo T4 flange? I highly doubt it now. That leak had to be bleeding off a ton of pressure, which makes the quick spool even more suspect to me. I verified the turbine is 66mm and the housing is .96 A/R as ordered.

Anyway the manifold should be off in the morning. I'll have it machined flat this coming week and throw away the copper gasket. Will try to track down a plasma cutter and get to work on the flange.

Also will be planning my next move when this does not resolve the backpressure problem.

To the person who asked, I have not yet ruled out a leaking BOV. I think I get what you're suggesting.. if the turbo is being forced to move enough air to make up for a leak, the exhaust pressure could be higher as a result of the wastegate holding more pressure waiting for the requested intake pressure. When I get it all back together I'll bypass it or otherwise block it off. I really doubt it has a leak on that side though as I again refer to the insane low end power and off idle spool time of this turbo.

Orr89RocZ

iTrader: (20)

I've had a leak like that...i actually was MISSING 2 bolts they backed out soo far. Thought it was a lifter problem I fixed it and it still spooled the same, and didnt feel much different. I didnt get a chance to do back pressure measurements, but judging by the carbon deposits coming out of the loose spots, I dont think it was leaking all that bad.

I also had a leak on my wastegate flange to the point where it kept eating gasket materials and I saw some of the gas stream shooting out. It whistled prettty good coming out of there but again flow wise, i dont think alot of gases came out.

You just need to fix it up and try again to see if it does anything for you.

DIGGLER

iTrader: (1)

i would think you could hear it if the bov was leaking that bad?
turbo is just too small on the hot side. my pt cruiser is the same way, i think i can have it spooled up by 1200rpms. lol tiny little turbo.

back in ~1990 my car had a banks twin turbo setup on it. the turbos were t04b's, t4 flanges with .68 a/r. it made somewhere around 500hp on pump gas with cats and passing emissions testing. it had a tpi on it and later a miniram.
it seems like a pair of those turbos would be the equivalent of a single t6 ~.90 a/r in terms of raw exhaust flow capacity?

junkcltr

iTrader: (1)

The overlap on both cams is about the same. Your cam has a higher rpm range. The smaller cam fit the TPI better and would make more torque under the curve. You might make more peak HP but less average power.