MT Supra overboosting/throttle closure with catless dp

[Skybanana]

Hey everyone I just wanted to let any 23 supra MT owners that me and some other manual supras are getting overboosting and throttle closure issues with catless downpipes. I was running an armytrix catless dp with a catsim and was having power issues with throttle closures after shifts. Not really sure the reason but seems that some of the 23 mt supras don’t enjoy running catless on stock tune. If you have ideas feel free to send them my way or if you’ve also had the same issues. I’ve swapped back to the OEM dp and will be going with a catback incase anyone is wondering.

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[Turcktech]

Hey, I am new modifying cars. I installed aa catted, awe nonresonated exhaust and mst intake. I drove half a day and the sound is insane. Wasn’t expecting this much sound from a catted dp.
My question is “how am I supposed to feel overboosting or throttle closure issue in my manual?” Can you give an example? Again I am new in this and want to know if I have the same issue

 

[Skybanana]

Sure I can send a video. It’s a little hard to tell in it but basically after shifting into third gear the rpm drops and holds for a second or two before building again. Ignore the power gauges they don’t mean anything. Just listen to engine rpm. The same thing happened into 4th gear too

 

[tub54500]

I have an a91 mt with the Armytrix catless and Hks exhaust. I’m not experiencing this problem. If anything I feel the turbo might be spooling quicker and me hitting boost quicker with no apparent throttle issue

 

[Skybanana]

Here’s a video of the issue. Ik it’s hard to hear but the rpm’s do not steadily increase after the shift and actually drop even with the gas to the floor. This would happen in every hear after 2nd. There is another manual supra near me with the same issue. It seems to be hit or miss with the manuals

 

[Crypto79]

That sounds like traction control

 

[Skybanana]

Trust me it’s not traction control. It happens in fourth gear too and even in third it never kicks in unless it’s raining. now that I’m back to the stock dp it doesn’t do that in third or fourth anymore.

 

[razorlab]

That sounds like traction control

Which is also throttle closing.

Getting an actual log of the car would be 1000% more valuable.

 

[Skybanana]

I’d love to get a log but I don’t have anything to log the car with and I’m not gonna pay hundreds of dollars for that. Plus I’m already back to stock dp. I ran catless for over a month and it continued to do the same issue.

 

[i3igpete]

Here’s a video of the issue. Ik it’s hard to hear but the rpm’s do not steadily increase after the shift and actually drop even with the gas to the floor.

This sounds like the clutch is partially slipping, and then rpms drop as the clutch fully grabs.

Were you able to reproduce this behavior when fully in gear from a roll, or was it only during shifts? I'm leaning towards clutch delay valve.

 

[Skybanana]

This sounds like the clutch is partially slipping, and then rpms drop as the clutch fully grabs.

Were you able to reproduce this behavior when fully in gear from a roll, or was it only during shifts? I'm leaning towards clutch delay valve.

It would only happen during shifts not if I stayed in gear so I also thought it could be the clutch but when I switched back to the stock dp the issue went away. I talked to some other supra guys and apparently jesse da bears thinks he knows what’s going on but I haven’t spoken to him directly about it but apparently some of the manual attempt to adjust fueling to account for the extra flow but the car can’t keep up so it ends up overboosting and the car closes the throttle to prevent damage.

 

[ColonelAdama]

Yes, I have documented this quite a bit on my thread. I had no issue running JB+/JB4 on my MT and as soon as i went catless it became a mess...

Stock tune still seems smooth but my JB4 logs (in passthru mode) indicate significant throttle closures under 5k rpm.

This is a stock map log. Orange line is throttle. Sorry to say I don't have a comparison log with OEM DP

 

[ColonelAdama]

Just to add about your weird shifting behavior....

The MT supra intentionally pressurizes the charge pipe between shifts so that it's more responsive in the next gear. Being catless is going to cause it to overboost between shifts, as you said. And overboost is throttle closure.

 

[noogie]

when you change the air flow that much such as removing the cat, the ECU probably isn't going to be able to compensate. this goes for any turbo cars.

you should have this properly tuned or put the stock cat back.

 

[concept]

when you change the air flow that much such as removing the cat, the ECU probably isn't going to be able to compensate. this goes for any turbo cars.

you should have this properly tuned or put the stock cat back.

Wouldn't an option be a catted downpipe? There are gains to be had with that, correct?

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