Throttle hang in between shifts, engine hesitant to decel (L83 in RX-8)

Well, I recently swapped an 2016 L83 into an 05 RX-8 with a T56 trans. It's a stock engine with Camaro intake/exhaust manifolds for fitment. The car has been tuned and idles, runs, and pulls pretty good at WOT for a stock truck engine but the everyday driveability (or lack thereof) is what's killing me.

For whatever reason, I'm having a lot of rev hang in between shifts. I either have to drive like an 80 year old and let off the pedal completely until the engine starts to decel before pushing in the clutch in order for the revs to actually drop once the clutch is pressed in. Also if I shift hard and quickly enough it also isn't noticeable. Not being able to drive this any way in between without pretty noticeable rev hanging is super annoying. Depending on gear and RPM the car is more or less hesitant to decel and sometimes it takes 3-4 seconds before it'll start to decel. The tuner still hasn't been able to figure out this issue.

I originally had a 2016 silverado ECU that came with my swap, rev hang in neutral was atrocious. I heard that reflashing to corvette manual OS would fix the problem so I did, but it only improved slightly and I thought the ECM's OS might have been corrupted or not completely overwritten. Then I decided to get a fresh ECU with a 2014 Corvette manual tune and it's still there. Long story short, I now have 3 HPtuners licenses at this point for this car and I still haven't figured out the rev hang issue.

When logging, when I lift off the pedal the pedal value bottoms out, but commanded throttle doesn't follow, it lingers in the 15% range before dropping.

It almost seems like something with driver demand torque, but i started with the values for a stock corvette which wouldn't have rev hang issues so I would assume those settings should be fine. Has anyone else run into this issue or a similar issue with a manual Gen 5 swapped car? At this point i'm starting to think my car is haunted.

I bet a 2014 5.3 OS would work much better. Just change the trans setting from auto to manual. 2016 is no good to use for swaps. I have had best luck using the truck OS. I might have a spare ECU I can program if you want to test it out

Curious to see if you had found a solution to this, been fighting the same issue on a LT4/T56 Swap. I've run both the crate control OS from GM performance and a 15 Corvette OS with no change. Would you be willing to share insights and/or some datalogs?

I have been thru this so many times. It is the 2016 OS. It will not make power. Look at the tps opening versus pedal. I bet the tps never goes over 50 percent and no tuning can fix it. There is something odd with the os. I will help you fix it for free. PM me if you have hptuners

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Originally Posted by 78bronzechariot

Curious to see if you had found a solution to this, been fighting the same issue on a LT4/T56 Swap. I've run both the crate control OS from GM performance and a 15 Corvette OS with no change. Would you be willing to share insights and/or some datalogs?

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I have a Chevy Performance LT4 crate engine and T56 with the same issue! They supply 2 wires for a top of clutch switch that is suppose to cut fuel when you depress the clutch. I wired it in but I can't seem to get it to activate. Is there anywhere in the HP datalogs to see if it is enabled or not?

I like to disable CFCO and Spark Smoothing so I don't think that's the problem.

In the process of installing a Borg Warner S366 on the car (rear mount) and I'm wondering if anything else has happened in the few months I've been busy/dead. I'm hoping the turbo won't make my problems even more pronounced otherwise I'm going to hate the car.

It looks like some people who replied blamed the 2016 OS, but the car is currently running a 2014 Manual Corvette OS with the same exact problems so I don't think that is the problem.

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Originally Posted by Trackman101

I have a Chevy Performance LT4 crate engine and T56 with the same issue! They supply 2 wires for a top of clutch switch that is suppose to cut fuel when you depress the clutch. I wired it in but I can't seem to get it to activate. Is there anywhere in the HP datalogs to see if it is enabled or not?

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Hi, Could you solve this issue? I've the same problem with two LT4+T56. I really appreciatte your help. Thanks!

Still looking for help on this. I am more than willing to pay .

Have you tried lowering the driver demand table in the 0% row?

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Originally Posted by PaceAutomotiveLTD

Are you using a clutch position sensor? If so i found a little work on the CFCO helped lots

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I am.

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Originally Posted by 32vape

Have you tried lowering the driver demand table in the 0% row?

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I am not good with HP Tuners so I have left the tune alone and learned to put up with it. :(

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Originally Posted by Trackman101

I am not good with HP Tuners so I have left the tune alone and learned to put up with it. :(

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Can you post your file.

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Originally Posted by Jeff7577

Can you post your file.

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Still looking for help. Pointless to have a 6 sp when your throttle hangs on the shift.
Willing to pay.

I?ll message you!

Attachment 109472
You need to max out your decreasing rate limits. I modified your file and attempted to upload. Hope this helps.

would love to know if this was the fix, or got fixed?

Any updates to this? I have a GMPP LT4 with a a TKO and my throttle hangs. I did the torque demands for decel and it didn?t make a difference. Also my CFCO table isn?t available in HP-tubers for my OS?

Any advice would be greatly appreciated.

Stan

Sub'd for answers. have a '14 M7 Corvette that has the hang issue on occasion. Sometimes you can tell the throttle closed because you can hear the exhaust note change, and it actually shifts into the next gear nicely. Other times the rev's hang and your syncro's get a workout. I've max'd out the ramp rates as far as I can tell, however this didn't fix the shifting issue.