Silver_TransAm

iTrader: (2)

I have an sts kit w/67mm turbo no intercooler( should be here tomorrow) on a stock bottom end ls1. It also has a cam with 232/236 .5**/.6** lift on a 112 with comp cams valve springs, a 90/90 fast intake with headers. The problem I have is that when the boost goes above 4psi it seems like it runs out of steam. I know that an intercooler would help but wanted to see if the problem is tune related or do I need an intercooler that bad. I have a 2 bar SD tune on it already. With the wide band I am seeing about 10-11 to 1 under boost. Is my cam hurting it that bad or tune? Also what cam would you guys recommed for my set up? My horsepower goal is about 600-650whp once I get a forged short block.

Silver_TransAm

iTrader: (2)

Also for reference I raced my buddys 00' ws6 with heads and cam and got smoked?! He pulled pretty good and continued to pull away. I know I should be beating him, or at least I thought I should. His car has about 450-465whp. Hope this helps. If you guys need more info let me know Thanks.

gametech

iTrader: (1)

Which Comp springs? Your symptoms sound like valve float or fuel starvation. Also check for exhaust and boost pressure leaks. A leak on the hot OR cold side either one can skew your backpressure ratio into the realm of no more power.

NYSS Guy

iTrader: (1)

Any idea on IAT's? Also, in my experience, if a turbo car is making the same peak #'s ad an all motor car, the all motor car will pull away. They tend to have a more broad torque curve.

Also, you mention that it runs out of steam when you go ABOVE 4 psi.....how much boost are you running?

Silver_TransAm

iTrader: (2)

I am running about 6 but seen as high as 7psi. Dont think I am running out of fuel because my afr stays rich all the way through the boost even up to 155mph.

Silver_TransAm

iTrader: (2)

Not sure on the springs, but I do hear a wee little exhaust leak. I have taken care of all the boost side leaks already.

02 hawk

iTrader: (11)

mine did the same thing.....around 4500 rpm it would just flatline would not make more power....if u changed ur valvesprings,check ur fuel, but first check those plugs.......i melted the #5 piston.....AND DONT DRIVE IT HARD OR YOU BLOW YOUR MOTOR LIKE I DID

Silver_TransAm

iTrader: (2)

Just put TR6's in not to long ago, but will check that too. It's not falling off at a certain rpm but rather once it goes above 4 psi.

02 hawk

iTrader: (11)

mine was only making around 4-5 psi also....and hp was like barely 300....check the color on all the plugs....

Silver_TransAm

iTrader: (2)

cool I will check the plugs tomorrow. So what about the cam can I do better with a diff one?

gametech

iTrader: (1)

The only possible problem your cam could be causing is overtaxing the valvesprings under boost. While it may or may not be ideal for your combo, the cam is NOT the current problem.

Silver_TransAm

iTrader: (2)

Thanks. I will check the plugs and give an update.

Blackbird

valve springs.

mine does the same thing. my springs are tired, it's done by 4500 or so.

slap some duals in and make power til redline.

RW99

Check your BOV and make sure it's not opening prematurely; a reference line disconnect will put you in the "some but not enough" boost space. What's the wastegate spring, and are you using a boost controller?

Silver_TransAm

iTrader: (2)

I do not have a BOV yet (came with the intercooler today) The wastegate spring is a 8# and no boost controller yet. I did pull the plugs and they did look like they got really hot. They had a real rusty dry look to them, so I put some new tr6 plugs in till I can order some colder plugs since no auto parts store has anything colder. After the plug change it did feel a little better but still feels sluggish. 100% throttle feels the same as 50% throttle. I hope the intercooler will be the fix to this.

02 hawk

iTrader: (11)

+1 for the valvesprings get some duals and harden pushrods..use ur stock manifolds..dont think the intercooler is the problem for the amount of boost your runnin,what are ur plugs gapped at????

Silver_TransAm

iTrader: (2)

Think the valve springs could be holding me back, so I am trying to find a good set of valve springs( already have hardend pushrods). What brand of dual spring should I go with; dont want to buy them for a third time? The plugs are gapped at .04.

RW99

I used Patriot Dual Golds on mine to solve a bit of power fluctuation at the top end... but this was minor compared to your problem. Anyway, they performed better than the "upgraded" springs that came with my AFR 225s. Scroll to the last posts: https://ls1tech.com/forums/showthrea...403&highlight=

Can't hurt to replace yours now, although your current springs would have to be pretty hosed to give you the results you're seeing. By the way, at what rpm are you reaching your 8 psi of boost? Is boost steady from there all the way to redline?

Lastly, have you done a compression/leakdown on all cylinders? My original LS1 was fine as a 400 rwhp/rwtq NA car, but just couldn't hold when I went turbo... too much blow-by.

autosay97

iTrader: (72)

There is a reason for you not hitting 8 psi, re check all your hot side piping. You should be seeing 8 psi period, I bet you have a big hotside leak somewhere. Check your wastegate valve to seat, may need to be lapped in. Also, what a/r on the turbo?

SP Motorsports

iTrader: (2)

check intake air temps,but ore importantly check how much timing you have in it when it goes deep in the 10s ,might just be blowing out the spark to rich to little timing