Kaneman

iTrader: (5)

I am not sure if everyone reads every forum so since I have a boosted car I thought I would post this here to get some additonal opinions.

I have a 2000 Camaro 408, Comp 220/224 581 581 114, Crane duel springs, Yellow Terra rockers non adjustable, T76 .96 housing modified STS, 3 Bar map.

The issue I am having is no matter what gear so first gear maybe about 5-6 psi boost at around 5500 rpm the car just falls on its face. I can be at full boost 18 psi 4th gear but once it hits 5500 rpm it falls on its face. It is almost like there is governor on the car. I have checked all the areas where to ensure that the rev limiters are set to 6500 but this does not feel like I am hitting the rev limiter. We all know what it feels like to hit the limiter.

We thought back pressure when I had the .81 housing on so I switched to .96 no change. Thought it might be the fuel injectors so I changed from a 57 to a 79.

I have people telling me different things so I would like you alls opinions too. Some say the cam may be a tooth advanced so the valve timing is messed up so there is a fuel brining issue and others say it is the PCM.

Unless someone tells me different I am going to try the PCM tomorrow.

Thanks in advance for the help,

Kane

'Trust'

iTrader: (24)

Which plugs and gapping do you have? Could be blowing the spark out. What is your A/F at 5500+?

Kaneman

iTrader: (5)

TR6 with .25 gap. I think now looking at all my graphs with different setups but the same cam in every setup I am seeing a consisten power issue. What is a good tame turbo cam these days with like a 116 lsa? Would a Z06 cam work with a 408 our would that cam be limited too?

Here is a link to the other thread.

https://ls1tech.com/forums/generatio...rev-issue.html

Thanks,

Kane

frtupchevy

iTrader: (6)

Low fuel pressure?? Run it with a guage at that rpm when is falls flat see if the pressure decreases at all.

crashly

ok,
firstly we know that 6 psi = 1.40 p2/p1 ratio
and 18 psi = 2.22 p2/p1 ratio

rough calculations here:
408 cubes x 5500 rpm / 3456 = 649.3 cfm
(cfm x pressure ratio ) 649.3 x 1.4 = 909.02 "turbocharged cfm"
( cfm > lbs' per minute) 909.02 x 0.0691 = 62.8 lb/min of air..

now go and look at the graph provided....
along the p2/p1 vertical axis , get to 1.4 ....
now go to the right until you get to 62-63 lb's per minute

what do you see ????
way, way off the flow chart



now the same with 18 psi... ( 2.22 p2/p2)

408 x 5500 / 3456 = 649.3
649.2 x 2.22 = 1441.2
1441.2 x 0.0691 = 99.58 lb's /min

no way the 76mm turbo will flow 99-100 lbs /min

you have your answer...

cheers
ash



claimer;
no air temperature increase included in maths
100% volumetric eff assumed for ease of example.

transamfreak01

iTrader: (8)

well id first talk to your tuner but with the 408 and that 76 im sure its running out of steam. i would think that turbo is to small for a 408 and thats why at 5500 in every gears its dying. thats just a thought but i could be wrong.

Kaneman

iTrader: (5)

But it only makes 5 or 6 psi in 1st gear would it not be able to rev past 5000-5500 and make power? The car feels and spools amaizing but no matter the gear or boost psi it is done. I think I am going to run it N/A and see how the car reacts with no boost.

Kane

crashly

not enough load on the engine in first gear,,,,,

if you put the car on a dyno, i bet the engine would be 'all over' a couple hundred rpm sooner than 5500 rpm...
right where the torque falls off....

hawk584

iTrader: (1)

call Garth @ Leading Edge Performance

transamfreak01

iTrader: (8)

Yeah the spool would be amazing because of the size of the motor and size of the turbo. It could also be a load issue. I would just contact the tuner and see what they say

Kaneman

iTrader: (5)

Garth built the last revision of this motor.

Kane

hawk584

iTrader: (1)

never hurts to call

1320

iTrader: (6)

The problem is that, he dynoed, 540 corrected which was a real world 490 hp....so about 50 lbs a minute at the peak. And its a speed desity car so he ran NA (testing this) with the same problem........

The other problem is that zombie made 700 on his 76 on a 370 with the same heads. I made 656 on a 346 with a .82 housing 76. Both of those run zo6 cams. Even when they run out....the power doesnt fall off a cliff like kanes. The 370 was running 6000 at the peak and would even tapper much till 6600 or higher.

Same heads, similar cams, same exact exhuast (manifolds, y pipes etc) , same intakes, same exact intercoolers,same cold pipes, similar turbos , same afr, but this thing falls off a cliff......at 4700. It doesnt seem like 30 more cubes will decrease the peak hp over 1000 rpm and reduce peak power by 200 hp.

Kane I have an idea......ill post on the other board.....I think I might have a way for you to check the cam timing without pulling it apart. Or atleast close enough, to know weather its worth pulling apart.

crashly

i wonder if the turbo is out of balance?

the reason i used this as an example , is
I've dynoed a "few" engines, and when the torque falls off, the turbo is usally done, finished.
If there is more to the story here , it would be good to hear it...

It's got to be something easy, if these other cars make more power . ??

Is it a new engine ? camshaft not degreed correctly ?
the fall off in power has to be either llack of air or lack of fuel ??? correct ??

i wonder if there is a air leak somewhere ??

points to ponder....

kikass_z28

I have had similar issues because of a clogged fuel filter. Drove perfect until wot and it would fall on its face around 5000rpm.
just my .02

longrange4u

iTrader: (2)

Fuel Fuel Fuel... that is the same symptoms I ran into with my first STS setup when I hit the max of my injector's.

1320

iTrader: (6)

Maybe it could be fuel, but if I recall correctly, it has a "fuel system" that includes, a reg, rails, #6 cross over....and knowing Kane probably duel pumps already.

I d bet he already monitored fp under operating conditions too ? Is that fp reg boost compensated?

Did you Kane?

Is it possible one side is being starved maybe? Have you compared plugs from one side to the other after a pull?

Kaneman

iTrader: (5)

Dual in tank walbros, high flow rails, -8 AN braided hose feed, -6 AN braided hose return, Adjustable fuel regulator. Fuel is rock solid AFR is right on. I did not think both threads were going to take off like this so please look at all the data on

https://ls1tech.com/forums/generatio...rev-issue.html

Picture of fuel.

http://members.***.net/kane-forum/STS%20Kit.htm

Kane

longrange4u

iTrader: (2)

I stand corrected... Looks like he has that accounted for unless its choked at some point. It dosent look like it.

longrange4u

iTrader: (2)

Have you measured your backpressure? I am just throwing ideas out... Big engine.. smaller turbo. Could 5krpm be where you are exceeding your backpressure limit? Whats your hot and cold side piping? I see that you thought of this and went to a .96... but maybe the limit is your pipes not your turbo?