Zombie

iTrader: (2)

The way the turbo boosts is very sensative to temperature here. I really noticed this when I tried the pt88. At 60 degrees the car would barely build boost and would take forever to spool. At 40 degrees I could achieve 2 psi on the trans brake compared to 0 psi at 60 degrees.

With the .96 a/r housing on my t76 i've been limited to 10psi now, unless it's 40 degrees out, then it will boost 12-14psi.

Looks like the best housing choice for me is the .81 housing and i'll be swapping it back on the car. Never would have guessed that the housing size would limit my boost the way it has.

Car went 10.6 @ 129.1 on 12 psi with the .96 a/r t76 last time i ran it, it was a very cold night though and the DA was a little under 1000'. I wonder if twins would spool better on a rear mounted setup.

Backpressure was 27psi with 10psi of boost, not much of an improvement from the 3:1 ratio I was seeing with the .81 housing.

I really would like to put the turbo up in the engine, but I just can't justify the cost of doing that right now, way too expensive.

FormulaFire

iTrader: (20)

your mph is about the same with 15psi on the other housing.. and times are really close..with just 12psi. What all have you tried to get your boost up? I would say stick with the .96 A/R.. just need to get all the bugs worked out

ninetres

iTrader: (35)

I'm not sure I understand why you can't build more than 10 psi at all times. I have a T76gts and am running an 8.7psi WG spring and I can't keep it under 10-11psi.

When my car was getting tuned I had the WG reference line hooked up wrong and the boost shot to 14psi by about 4k rpms before the tuner realized it wasn't stopping...and let off!

hellbents10

iTrader: (10)

I know put the turbo up front.

Sorry Zombie I am just being a smart a$$ lol.

RealQuick

iTrader: (14)

interesting...

Toonz

iTrader: (6)

This kind of goes back to another conversation on here. You're running the same times/et's (or very close to it) with less boost. Meaning the car/engine isn't working quite as hard, and "should" last a "little" longer.

Personally I would stick with the .96 as well, but that's just me.

engineermike

Subscribing.

cablebandit

iTrader: (37)

i dont get this...Quicksilverados truck has the same boost all the time...no matter the temp. If you havent wrapped the pipes and are still on headers...you are just pissing in the wind.....gotta save all the heat you can and then see what does/does not work.

stevieturbo

I assume you are talking ambient temps here ???

If you are having boost issues, IMO it sure aint down to ambient temperature.

You have boost issues !!!! Whether thats due to bad heat management withing the exhaust or turbocharger system itself, or down to poor boost control....you need to sort that out.

JD_Z28

iTrader: (19)

I'm running the .96 AR on a stock 60-1 and I noticed that I don't see full boost untill 3500-3600 rpm's. I talked to STS and they said that it would be better to run the .96 in Cali?

I would think you would have more top end with the bigger housing but spool time on the .96 sucks.

Zombie

iTrader: (2)

I put it on a mustang dyno last night (the same dyno i've been using for quite a while now), made 470 rwhp SAE and 455 uncorrected at 10psi of boost. Dyno pull lasted 9 seconds and I was unable to complete the pull. The car would not go over 5500 rpms on the dyno so I stopped the pull. We logged boost with the run too, didn't reach 10psi until 5500 rpms. Very laggy.

My previous dyno at 10psi with the .81 housing was 470 rwhp SAE and 430 uncorrected at 10psi of boost. Dyno pull lasted 3.5 seconds and took the car to 6500 rpms. The logged boost showed 10psi at 4000 rpms, pretty decent.

The way the car spools is very dependent on the weather. When our DA is 5000+ it's a very noticable difference compared to our 1000-2500 DA days.

I think i'm going to eventually have my whole exhaust system remade and ceramic coated, mainly because my y-pipe hangs really low and it's annoying.

I'm just sharing the data I've gathered with everyone, the good and the bad.

Before the dyno we pressurized all the intake pumbing through the turbo inlet to 10psi and there were no leaks. No audible or visible exhaust leaks either. Stock manifolds, y-pipe to over axle exhaust is insulated, but the overaxle piece to the turbo itself is not insulated yet.

I just don't have the exhaust energy to spool the turbo very well. One of my friends has a rear mounted .81 a/r t76 p-trim and he can get 15-16 psi of boost very fast on a stock motor. Car has gone 10.2 @ 133 and is 3600lbs. The DA was below 1000 that night though.

I'm out of money for a while, but I'd really really like to try a tc76 to see how it spools.

cablebandit

iTrader: (37)

hmmm...weird....what happens when you add lots of timing down low? until you are in a few lbs of boost, i would run a lot of timing and lean it out.

kidcamaro98

iTrader: (8)

sound like you have a exhaust leak someone thats limiting your boost. Once the exhaust pressure get to a certain pressure inside the piping and you have a leak, it will begin to leak more which will cause a limited boost level and a late spool. And your noticing a difference in temps because whens its colder, the air is denser so the exhaust leak wont be as bad as if its warmer out. How much psi are you set to run?? 12??

the easiest way to find out if you have a exhaust leak is to grab a friend, and start your car at idle. When its idling you or your friend take a rag and plug up your tail pipes and stick your head under the car untill you can hear the leak...

DrTurbo

iTrader: (3)

First problem is listening to STS and any of their claims and advice. Next run the .81 if you want quick spool, but your going to give up some on power, though a 60-1 is a bit small for these engines anyhow.

ninetres

iTrader: (35)

So strange. Mr_president has the .96 t76gts and he sees full spool (9psi) almost instantly when he stabs it. He has a TH400 like you do but with 3.50 gears........so your turbo should be even more loaded. His is a FM, but I seem to recall several rear mounts doing just fine.

Zombie

iTrader: (2)

I have lot's of timing in it. I run a 12.5:1 a/f util 3-4psi then it goes to 11.5 until 7-8psi then 11.0 at 10-15psi.

The timing does help spool it by pushing the converter higher. I've actually found the point where more timing is causing a reduction in HP. I have my timing set to 15 degrees at tq peak and 21 by 6500 rpms, this is for 91 octane. When I added 100 octane and bumped the timing 5 degrees it lost 20 hp. Put the timing back to where it was and it gained the 20hp back.

I really wish I could run the PT88, but I just can't spool it. The .96 a/r T76 R trim exhaust wheel is better than the 88, but not a whole lot. The .81 drives really nice and i'm able to get 15-16psi out of it, but thats it.

BTW, for these tests, the wastegate was plumbed shut, i.e. the turbo was going to what ever it could make. This same .96 a/r setup got me a 10.6 @ 129, but it was cold that night and I was seeing closer to 12psi I think.

Zombie

iTrader: (2)

yes, a front mount has a lot more exhaust energy than a rear mount, it's going to spool faster. I think several of the rear mount guys are lacking a good point of reference when talking about spool characteristics. Several of the dyno graphs I have seen show the spool differences.

A turbo mounted close to the energy source will always spool faster and have a higher overall power potential.

No one wants my setup to work good better than me, but i've been doing a ton of experiments with this and I think i'm finding some of the limits. Not many people share their failures. A failure is still a result and worth posting.

If anyone would like to send me a turbo to experiment with i'd be all for it
I still have a PT88 sitting in my garage that I need to get rid of

Nickn20

They have to be small, becuase there is 15 feet of exhuast pipe between the turbo and the engine, in order to make real power you need a decent sized turbo, and that just wont do in the rear of the car.... I know you know this, just saying it for others.... I tuned a STS vette the other day, car spooled around 3200 on my dyno, and then on the street in first and second it spooled at 4k rpm extreme lag, and those turbos are tiny!

engineermike

Can you describe exactly how you did this?

99Z28LS1

iTrader: (4)

im sorry to hear that you're running into limits with your set-up Zombie. i think you have a car and would love to see you go faster and faster

goodluck and i hope you cause people to when you run a 9.99 or lower at the track