BlueCollarGuy

My A4 hits the rev limit at 7000 rpms and hangs/sticks there for about 1 sec before it shifts. This occurs at full throttle.

Part throttle normally shifts properly; though intermitantly there is a slight hestiation here and there. But it does not go to the max rpms, it just shifts at a higher rpm than it normally does on part throttle.

Any advice, experience, or suggestions for diagnosing and testing the issue?

Thanks

jimmyblue

iTrader: (11)

If your rev limit is 7000RPM then somebody's been messing
with the tune already. Which makes bad judgment as much
of a possibility as anything mechanical.

I'd be hooking up a scan tool that will log the transmission
commanded gear and the usual stuff like RPM, line pressure
and such. Then you can see if it's a problem where it was
told, and didn't get with it, or the command comes too late.

mrvedit

At WOT both RPM and MPH must be reached.
As jimmyblue states, someone has already changed the tune.
Reduce the WOT shift MPH by a few mph and it will likely work just fine.
Personally I set my WOT shift MPH to correspond to about 6300 rpm, and at the track change the desired shift RPM (e.g. 6900); it then shifts reliably at that RPM.
If that doesn't fix it, you will have to log the trans parameters as jimmyblue stated.

BlueCollarGuy

Over the past few days its become clear that it would be optimal if I had a method for tuning the car myself, as well as having the knowlege to tune it myself. I did read the sticky for the HP tuning program.

I have a laptop. Is it as simple as downloading a program and buying some sort of physical interface between the laptop and the car? Then I could just follow the instrution in the stick and see if I can get a good result? I fugure try doing it myself first then if it fails just take it and have the experts do it.

Are there any easy to use free tunning programs available?

Thanks for the help.

mrvedit

Unfortunately HP Tuners is very high priced at $650 which includes the laptop (USB) interface and licenses to modify four different PCM (or TCM). Even if you find someone with HP Tuners, they would likely charge you $100 because it will cost them that much for the license to modify another PCM. The pro tuners buy an unlimited license ($3000+) and therefore only charge you for their service/time.

There is also EFI Live, which I believe has similar pricing and conditions.

I am not aware of any free tuners.

Due to my frequent engine mods and experimentation, I have changed my tune well over 200 times. I change it after every run at the track to try out different A/F ratios and advance curves.

RonSSNova

iTrader: (3)

I believe I sent this gentleman here. He hadn't stated 7000rpm on the vette site...I don't think.

It would be free for someone with HPT to read the tune in his car and see what has been messed with. I don't know it any of the hand helds let you mess with shift points???

My HPT cable won't reach to Texas.

BlueCollarGuy

Yeah I was the one asking about this issue on CorvetteForum. I took your advice to come here. Lol I figure its best to listen when others give you advice. Thanks for that btw.

Been doing a lot of reading. Trying to save the cost of a diagnostic. Plus I like doing things myself.

Still working on it. I think I am going to see if I can find someone in the Dallas Tx area that has tuning equip or some type of tool that can tell me where im at programming wise. Hopefully they will let me take a peek for free.

mrvedit

As Ron says, anyone with HP Tuners (or EFI Live?) could read you tune, examine it or even post it here for others to examine. However they could not change the tune and save it into your PCM unless they pay for a license or have an unlimited license.

This problem of hitting redline before the trans shifts often results after a higher stall torque converted is installed. Higher stall converter are generally a bit looser and require a tune to fix precisely this problem.

RonSSNova

iTrader: (3)

You are welcome!
BTW....someone over on the vette forum also said tuning is easy.....it isn't.
It is a fun learning process. Especially if you like a challenge.

I'm almost wondering if maybe someone changed the rear gear ratio in your car. If the gears are lowered, the engine would need to go higher rpm for the same mph and it would over rev before shifting. How much do you know about the car? All stock?