Turbo-Geist

Yesterday at the track, it went into REP mode on 3 out of 10 passes. It happens during launch when trying to get more aggressive than a 1.5x 60 foot. The car has the potential to go low 9s with the 6 speed transmission if I could launch it more aggressively, but getting aggressive with the boost controller and trying to apply the throttle quickly results in an aborted pass and spending your time going down the track at 25 mph. It's not very fun when the event is being broadcast online and it looks like the car can't get out of its own way. I told people I was trying to tune around it with HPTuners and they just scratched their head.

The tune is scaled 50% and I've maxed out all of the tables that I know of to change. The combo spools very quickly. There is no 2-step, but it is at 19.2 psi by 18 mph and 44 lb/min at 24 mph.

Has anyone experienced this before? What did you do to solve it?

*Important Info*
This is the code I am getting:

DTC P1515 Control Module Throttle Actuator Position Performance

Circuit Description
The commanded throttle position (based on accelerator pedal position and possibly other limiting factors) is compared to the Actual throttle position. The 2 values should be within a calibrated range of each other. Both the PCM and the TAC module redundantly monitor the Commanded and Actual throttle position. This DTC sets if the PCM detects the problem.

Turbo-Geist

Here's a picture from the 1st of 3 times that it happened yesterday. You can see the sharp rise in manifold pressure and airflow. 19psi at 18mph and 44lb/min at 24mph.

ysb02

Did it throw any codes?

Turbo-Geist

It's thrown 1514, 1515, and P0101. I wasn't able to check this time because I had to reset them to get the car down the track.

Pekka_Perkeles

NW102mm?

ysb02

https://www.corvetteforum.com/forums/c5-scan-and-tune/2910355-recieved-the-infamous-reduced-engine-power-message.html#post1578706323

Its not that?

Pekka_Perkeles

I doubt. That table is already modified in all basic supercharger setups. It's probably maxed out already.

It's not the dynamic cylair either, as it seems to be well below the max value (2.23 g/cyl)

wesam

Try to cut down your IFR and VE ( if SD ) or MAF by 10% this should solve the problem
you are exceeding the limit of the LS1B ECM
but put an eye on your spark tables as this could offset it to the left

Turbo-Geist

Correct, the table related to the 1514 code is maxed out. The dyn cylair is not real because the IFR and everything related is scaled 50%.

IFR is scaled 50% and VE has been adjusted appropriately. Without any scaling it hits the limit at 4,000 rpm. Car makes over 1000 rwtq at 4200 rpm.

Smoove

Just for the hell of it, are you sure the car doesn't have a failing part?

Turbo-Geist

Which part?

Smoove

I dunno but one of those codes might point you in the right direction. In my 10 years working as a tech for GM I have never seen a phantom reduced engine power message pop up, and not require a replacement part. Throttle pedal/throttle body/tac module/ecm/etc. Sucks, I know but, I would look into a code or two. I'll scroll up and see what codes you have, and see if I can see anything obvious(research them) with them first chance I get.

Turbo-Geist

Thanks, I'm going to set all of the relevant codes back to "report" for the next track visit just to see if I can get info on what is causing it. I thought setting them to no error reported would turn them off but of course they still happen. Things would be much easier if HP Tuners would just give you the ability to disable REP completely.

JDS99

I think it's just scared of all that boost so quick

Turbo-Geist

Lol, maybe so, Jon. This combo with a two-step would be even more outrageous. I'm really impressed with the spool-up at the track. I had to turn the launch psi and CO2 pressure down in 1st gear to get it to not go into REP mode every time. I also had to be easier with the throttle. I'm hoping the changes you suggested work.

Smoove

Do you have a stock throttle body to try? JUST for the hell of it? Dirty or damaged MAF? Bad MAP? Small vacuum leak at intake/TB? MAP/MAF voltage good? PCM failure? Just some ideas to what would cause some of those codes.

Turbo-Geist

I'm running an LS7 intake and stock LS2 throttle body so I can't try an LS1 throttle body. No MAF, the MAP sensor is new and according to the logs is reading fine. No apparent boost or vacuum leaks except for when it blew the brake booster line off. It is now secured with a hose clamp.

Smoove

I thought you had an aftermarket TB. Just looking at your codes, and the flow charts for them, point in those directions.

StealthFRC

mine used to do the same thing, wouldn't go over 16psi without going into REP. now its good for 19ish and tuner claims its good up to 21psi but if it spikes over that it will go into REP again. im not sure what my tuner changed to stop it but i can ask him for you. mine is tuned with efi live.

Turbo-Geist

Good info. I think the tables are basically the same whether using efi live or hptuners. It sure would be nice to know which ones were changed and where the values are set.

Did he mention why it is still going to do it above 21 psi?