Help tuning 05 Corvette- car bug down after 5000 RPM

[HA-KSA]

Hi, please take a look at the scan and note that O2 readings are STRANGE.

The car has the stock tune, the problem is the car bug down very badly after 5000 RPM.

I have seen this for the first time in my life.

I have checked the air box that is maybe something is sticking on it but i found it OK.

Are there any way to check the fuel pump pressure with scanner?????????

It seems that it is not getting proper fuel to continue accelerating after 5000 RPM.

Also the O2 reading shows very low numbers?????????? i tried to richen the car from 4000 RPM all the way to 8000 RPM but still getting the same problem.

The stock tune seems OK compared to another C6's except the gear ratio it has 2.73 on it.

Your great help with this matter.

[EC_Tune]

What mods do you have?

BTW: You will need a fuel pressure gauge as GM doesn't measure fuel pressure, just assumed... LOL

[HA-KSA]

The car is 100% stock.

[EC_Tune]

Not sure what's going on but your o2's went dead during the run. Your IPW went up so I don't think there is anything wrong there and COT is active. Just wierd. I've only seen this one other time (and it didn't make sense that time either! )

Time for a wideband...
BTW: As typical of the LS2's the knock sensitivity is too high. Where is KSA?

[HA-KSA]

KSA-Kingdom of Saudi Arabia

[HA-KSA]

Is it normal that torque management shows active all the time with stock tune even at part throttle????

I will hook up my wide band and see what it will give me.

For examble if the car is too lean : I have tried to richen the PE tables several time but same thing is happening.

If the car is too rich : and i have try it before the performance will be different but it will not bug down even at 10:1 AFR.

What would you suggest?

[EC_Tune]

You want to modify the MAF table and put the PE value to what AFR you want. IE 1.151 for a 12.75 AFR commanded. Turn COT off while tuning so that you don't get ultra rich AFR while you are dialing in the engine.

[BBA]

I have seen weak and worn out valve springs that would not allow the valves to seat at high RPM cause this. The way to tell is adjust the rockers, if you can not adjust more than 1/2 turn preload without the car idling like crap, the springs are too weak. Basically if the best rocker adjustment you can get is right at the point of zero lash with almost no lifter preload, replace the springs.

[5_Liter_Eater]

There is no rocker adjustment on the LSx motors.

[BBA]

Ahhh...haven't pulled the covers on one to check yet, thanks.

The other way to tell is to pull the covers and see if you can depress the valve stem by hand, if you can, the spring is too weak.

[EC_Tune]

You won't ever be able to depress a spring that's not broken by hand. LOL

[BBA]

You won't ever be able to depress a spring that's not broken by hand. LOL

Talk to the hand man (figuratively, really)

Thats the easiest way to find weak springs. I have done it myself numerous times. Then again, I have surprisingly strong hands, but if you're not quite the manly man, I can see your point.

[EC_Tune]

Eh, most aftermarket springs have a minimum of 120+# seat pressure. No I don't have thumbs of iron. lOl But *manliness" has nothing to do with it. Use a spring checker...

[9secZO6]

BTW, u will never get past a half-turn w. the healthier cams w/o the idle and idle vac going to crap....mine are right at 1/4 turn on adjustable set-up. 150lbs on the seat

[BBA]

On my triple spring 383 SBC with hyd roller cam, I always set to 3/4 preload. Any less and I got valvetrain noise when hot. That still idled smooth (pulled 215-200 PSI cranking pressure on all cylinders with 10.4:1 CR static.)

I can tell you on my 87 stock L98 C4, I had the same high rpm power loss, couldn;t adjust lash without noise without getting a crummy valves not seating idle, so I replaced springs and cured the whole problem, adjusted to 1/2 turn preload with no problems. And the new springs were definitely stiffer and not able to be pushed open by hand (the worn out ones could).

Anyway, to make a long argument short, check springs. If you have an on the car seat pressure gage, yes, thats the best way, but common sense and replacing worn parts still prevails here.

To the OP...Check the springs.