Pat-Man

iTrader: (3)

Very disappointed...

Was wondering if anybody had any ideas what might be wrong by looking at my graph.



Here's the vid:


The vid was the first run that he had some trouble with it trying to downshift into second when going WOT. Also, the popping is just my crappy camera mic. getting maxed out.

I'm really thinking its either my transmission fixing to die, or the TC slipping. Its a stock 4L60E with a stock stall. I watched the boost gauge and it never got past 2.5 lbs even though its set for 4. Also, second gear will hold 4 PSI no problem.

- Patrick

ACLR8R

iTrader: (2)

I'd put my money on either the trans or stall. My buddy had a convetor go out on him and he made 360ish rwhp on motor and 300ish on a 200 shot, just couldnt hold the additional power.

Pat-Man

iTrader: (3)

Yeah, that's what I'm thinking. Looking at the graph it looks like a dog...but damn in 1st and second it feels really strong on the street.

phildo

iTrader: (7)

Was it a load dyno?

Jimmy P

iTrader: (177)

I would get a built trans and a converter thats ment to be used in a turbo car. Who was doing the tuning on it and what did he have to say?

Lrry93

iTrader: (2)

Why are you only running 4lbs of boost on a 408? What is you C/R? Do you have any boost leaks. They will kill power quick and is probably your issue. You could should put down 100+ rwhp on motor alone Even with a crap trans you should have put down alot more then that. List your full set up to include motor specs and some one may be able to help you more.

theblur98ss

iTrader: (71)

What was your target boost? Bad WG, BOV, boost leak, fouled plugs?

Pat-Man

iTrader: (3)

I guess I should list more of my mods. Sorry about that.

Built LQ9 408 cid, forged rotating assembly, stock crap 98 heads (with stock valve train), stock cam, LS6 Intake, 60# Motron Injectors, stock 4L60E, 3.73 gears, TTi Street Kit with the T76, switched over to Speed Density (2 BAR).

I got this car from a friend with a blown transmission, but all the engine work and turbo was already on the car. Basically he got the forged short block then the shop just took the heads, cam, and intake from his old motor. I put in another 4L60E to get it running, but reused the TC from the old transmission. Only thing I've done to the car was put in the 60# Injectors, switch over the the 2 BAR OS, and the LS6 intake.

Currently only running 4 lbs to save parts (transmission mainly). Would like to bump it up to 10 lbs soons, but need to upgrade the valve train first. The car has no leaks that I can tell that maybe bleeding off boost. Also, this was just our car clubs dyno day (inertia dyno). No tuning was being done at the time.

V-seriesTech

iTrader: (5)

"but reused the TC from the old transmission."

Denali08

Why did he build a 408ci to put back stock cam? What's CR?

It should put out more power NA!

I think your stock valve train is the big problem. You need stronger springs to hold the valves from floating with boost.

Jimmy P

iTrader: (177)

There are so many mismatched parts on this build, plus without being tuned it will be real hard for anyone on here to try to "diagnose" what the issues may be.

rufretic

iTrader: (37)

I bet your converters shot. Have you had it tuned at all? You can tell alot with the tuning. I would put in a converter made for a turbo set-up, have the tranny refreshed or even better built and then get it back on the dyno with a good tuner. There is no way your set-up makes that low of power, even though you used a lot of stock parts, there is something seriously wrong to be that low. Good luck.

lifeisgood

iTrader: (4)

I think your stock valve train is the big problem. You need stronger springs to hold the valves from floating with boost.[/QUOTE]

my car made like 480 on stock valve train.
after the valvesprings were upgraded the car came alive....had alot of valve float.
and my car is a lower milage engine....only 54k on it

elias_799

iTrader: (8)

with that turbo kit and the 408 there will be allot of back pressure, but it is not just that, as said before you have allot of misplaced parts.

bboyferal

iTrader: (9)

A 76 on a 408? I don't know about that... In addition to the other things mentioned.

Exactly what kind of 76?

theblur98ss

iTrader: (71)

I was thinking a 76 on a 408 was part of the problem. After looking at the parts list that is the least of the problems. Not to be a jerk but you just wasted alot of time and money throwing the build together. I'd start with the stock top end, 60lb injectors and the junk stock tranny.

black98ws6ta

iTrader: (77)

Holy mis-matched parts combination. I'd put a set of valvesprings and go from there, the combination should atleast make decent power at low boost, I'm suprised the thing even holds that low boost. Try locking the converter on the dyno, if the rpm's flare up or anything of that sort you will know youve got something transmission related going on.

cablebandit

iTrader: (37)

that turbo and kit would do MUCH better on a 5.7...5.3 or 4.8. You will have lots of backpressure but it should make killer torque down low before it chokes and you arent doing that. Wastegate stuck open....blowoff valve....weak valvesprings. After all the issues are fixed I would suggest a forged 346 or a different turbo kit for the 408.

Pat-Man

iTrader: (3)

Thanks again for all the suggestions. Like I said before...I got the car from my friend that no longer had any interest in it, especially after the transmission crapped out. He had the motor and turbo kit put together by a shop in Houston probably six years ago that is no longer in business. There are a lot of unknowns at this point.

The car is tuned. Switched over to Speed Density just about a month ago. There are some tweaks that need to be done, but for the most part it runs great on the street. Before the injectors I was seeing about 90% duty cycle on the stock 28# before 4100 RPMs. So, that was the first big MUST have. Normal street driving I never really do WOT in 3rd gear, so I guess that's why it felt so strong to me before.

I eventually want to go with an 88 once I get the valve train and transmission squared away. I'm really thinking I'm seeing a transmission issue by looking at that graph. Never seen a HP curve just flatline like that.

elias_799

iTrader: (8)

i dont think you where listening when people where telling you that the type of turbo kit you have will make allot of back pressure even more with an 88. but don't worry i have a solution for you. you know the logger manifold you have on the left side where the alternator used to be, get a shop to fab you another one, but for the right side. sell the 76mm turbo and get two smaller ones, depending on what you power goals are. and your back pressure issue will be solved to a point. but your ac will be gone