STOCK Corvette LS2 E40 Chevelle Swap - Bogging in Gear

Hey all, first post

I swapped an E40 LS2 into my 71 Chevelle and was able to get it running without much pain. The engine idles smooth and will rev thru the RPM range in Park/Neutral but has its struggles under load. There are no internal mods and the only changes from stock where ditching the vette manifolds for LS3 Camaro units. The factory MAF was reused with custom plumbing.

Under very light throttle, in gear, the engine runs well however with anything more than very light throttle (don't think i've been above half throttle in gear yet) the engine bogs down badly and does not want to rev above 2000 rpm or so. In the attached log, the 2 instances where I got the engine near 2000 rpm in gear, it shakes so bad, not wanting to continue to rev, that i back off the throttle versus trying to accelerate thru it.

I really could use some guidance to get me at least on the right track in trying to diagnose/correct the problem.

Attached is the current tune and a log from my last test drive. Below is some other background detail on my setup.

As far as the tune goes, I am very much so a rookie and have limited changes in HP Tuners to items such as: VATS, Fans, Fuel Pump settings, disabling DTCs, turning off rear O2s and disabling options under Traction Control.

Should I even have the expectation that i could swap the stock motor in and without modifying anything that the car would run reasonably well without the need to tune until performance mods are made?

Background on my swap:
*Donor was a wrecked 2005 Automatic Corvette LS2 with 20k miles
*Used 2010 Camaro exhaust manifolds with the Corvette upstream O2 sensors
*Custom Air Intake plumbing with the stock corvette MAF
*TH350 transmission with 2500 stall
*3.73 rear gears
*Aeromotive 340 in tank pump
*Bypass regulator under hood set to 58PSI (verified at OEM fuel rail at idle) Vacuum port on regulator not used and left open to atmosphere to maintain constant 58 psi
*System voltage (read by ECM) never dips below 13V

The attached log shed any light on the problem or should I test longer and under different conditions?

I would flip the switch from auto to manual. Max out the brake torque management table, and the max trans input and output. Raise the ETC max to 100 on all but the first row, change that to 1's across. Start there and take another log.

Thanks for the response!

There was no noticeable change in the bog under medium acceleration after making the mentioned changes. Log and tune attached.

I follow the train of thought in eliminating factors such as the tables/parameters that can reduce torque or are dependent on gear selection. With the TH350 trans, I am not sure what gear the ECM is defaulting to and its impact on engine performance.

I am also going to update the Torque Management>Engine>AC Torque>Torque Reduction table to all 0s. I need to get gas then take it for another test drive thru the neighborhood.

Drove it a few more miles thru the neighborhood while logging (attached) seems as if it is running rich......assuming I can use the composite O2 voltage reading from the scanner's histogram.... i see a lot of red blocks while trying to perform medium acceleration. Those red blocks correspond to values from 50mV up to 400mV.

You need a wideband to really know what fueling is doing. It's a must for full throttle tuning anyway.

Per the fuel trims they look normal-ish, if it was rich all the time the fuel trims would be way negative as it would be yanking out fuel to bring it back to stoich. That log shows slightly positive fuel trims meaning lean.

Looks to be quite lean when trying to moderate accelerate. Try adding a bunch from around 6000 hz on up on the maf table.

Hopefully i understood correctly and made the correct change (went down to 5kHz tho). I tried adding 3% above 5kHz on one test drive, then started with the original file and did a 10% increase on a 2nd pass but with similar results. The vehicle still boggs under moderate acceleration.

I pulled the plugs last night to check condition and gap (.040") and everything looks normal.

Check bank 1 injectors and plugs - add misfire data to your scanner and see if any cylinders on bank 1 are misfiring...

Misfires all over. I tracked them on cylinders 1,4,5,6 and 7. LOL

Will review wiring to the coil packs tonight. One area of focus will be testing on the grounds.

I looked at your logs. Short term Fuel trims look relatively ok - a little lean, but ok.

Look at what happens at 1400 rpm up. Many times, I see Fuel Cut Type = TqRed and the Fuel System Status #1 = OL - ACCEL. I also see your Throttle Position (SAE) goes up, but your Accelerator Position D doesn't move much. That makes me think the ECM is killing power for torque management. It goes into torque reduction and open loop by messing with the throttle... That's my guess.

Take a look under Torque Management > General > ETC Limits > ETC TPS MAX. I wonder if changing the values in the lower ranges would solve your problem for now. The definition says "[ECM] 12850 - ETC TPS Max vs. RPM vs. % Max Available Torque: This is the maximum allowed ETC throttle percent based on the current percentage of torque being delivered. The PCM uses this to limit the ETC opening rate to maintain traction."

Not sure what exactly transmission the Vette had in it, but it must have been a computer controlled 4L60E/4L65E/4L70E. You'll have to read up on using a Turbo 350 that is not controlled by the computer. You might end up changing the Trans > General > General > ECM Trans Type to Manual.

Finally, since the stock type engine tune is designed to work with an automatic with a low first gear and an overdrive fourth, you'll probably need to make many more changes to get max driveability and power.

Good catch. I need to slow down and study the scans more closely.

Reading the definition on the ETC TPS Max, seems like this entire table should maxed out at 100.

The next tune will have the following changes:
ETC TPS Max Table set to 100s (all ranges)
Traction Control System Enable Temp from -40F to 275F
AC Torque Reduction table all 0s

Heck after those changes, it would seem that I have the Torque Management tab effectively disabled in every aspect

Well those changes did not eliminate the Torque Reduction Fuel Cut....

The ETC Torque Management Type is set to Trans
I can see in the log at 1968 RPM (11:03:13.060) that the "Fuel Cut Torque Management Type" was Trans. Fuel Cut Type = TqRed.

I'll have to keep at it tomorrow..

There are a couple tables in the rev limiter tab that you could mess with, but it is likely hitting the max idle limit. Without a VSS signal, it does not know the vehicle is in gear and moving. Probably going to need to feed the ECM a proper VSS to get it to work. You can run a driveshaft sensor, and use the Dakota Digital translator to send the proper signal. E40 ECM's are a funky breed.

This just does not seem to make sense. Why do I still have Traction Control effects active? The attached scan shows the ETC Torque Management type to be Trans although under Engine>Torque Management>General>Traction Control System all of the features are disabled....Spark, Fuel Cut and ETC......it as if the changes are not taking or I am just missing something.

When I experience the bog under moderate acceleration, I see activity on the ETC, Spark and Fuel Torque Management Types.....it is as if there is a table or section ive missed in the editor

Ive adjusted every table I could find that limits the engine in Neutral......with TH350 trans.....the scanner shows Neutral as the current gear

Set min desired torque to 8192 too that way traction can't cut anything below that... Like Veee8 said though - your going to need a speed input...

Bogging Problem Resolved!

I read thru the following thread from another swap and talked with a member by user id PATOOYEE and found the problem to be triggered by misfires. I increased the table values under Engine Diag> Misfire> Tables 14014, 14005 & 14001 by 25%
https://www.hptuners.com/forum/showt...light=12598983

It seems that if the motor enters a reduced power mode when it records misfires.....although I did not hear or feel what I thought was a misfire. This is likely attributed to the difference in the drive train and exhaust. This was confusing as there were no DTCs related to the reduced power mode or what was going on.

I wrote the updated calibration to the ECM and tried disconnecting the battery for 15min however ETC Torque Management Type was still set to Trans.....I cycled the key about 4-5 times, reconnected with the scanner and this seemed to reset the reduced power mode as ETC Torque Management Type now showed None. The vehicle drove well without limiting power!