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The mkiv Supra Owners Club

Hesitaion when getting into positive boost (only in 1st?)


veilsideTT

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Every since i had my MAP ECU tuned, now and again i had a very slight hesitation in first gear (auto). Its something i never got round to getting sorted.

 

Yesterday i installed a PI3800 and the hesitation problem is worse. If i stomp on the gas from a stand, then as soon as i get to around 2750rpm and get to 0.0bar boost the car hesitates/jolts a couple of times and then manages to get past the problem area and boost normally.

 

This only happens in 1st and i have to be on at least 3/4 throttle for it to happen.

 

Ive searched the board/SF and tried changing the TPS% values on my MAP-ECU but it has not changed anything.

 

Anyone know what the problem could be?

 

PHR stage 1

Stock fuel (upgraded pump and reg)

Stock ECU (MAP-ECU piggy)

AVC-R

 

My wideband reads major lean at the point of power cut. Only for a split second though as the power comes back on quickly.

 

Scott

 

PS, i wouldnt rule out the fact that this might not be a MAP ECU problem and possibly could be something else.

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Mine's doing the exact same thing i think dude (on AEM though). My AFRs are off the scale lean wise just before the turbo starts spinning, car does a little judder. Richens as soon as it's online, just waiting to get the software on and have a look. Emailed Pete@Thor about it too as the wierd thing is that nothing's been altered since he mapped it a month ago, just started doing it intermittently now :shrug:

 

EDIT: Just re-read your post, the only slight differance is mine tends to do it more on light throttle e.g. gentle acceleration from a standstill

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Ro, Sounds to me like the acceleration pump part of the map isn't setup well enough.

 

Would make sense..... will see what Pete says when he's free.... or might get the software on and have a tinker..... :innocent: (maybe not!)

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ive read the threads on SF regarding the TPS%.

 

Have remaped and changed the values this morning to see if this was the problem but no change.

 

It couldnt be something simple like plugs could it? I run IK24's but am due a change!

 

Surely this would happen more often than just in 1st gear if it were the plugs???

 

Dodgy coil pack?

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Going lean when you crack the throttle is due to more air than fuel...if your plugs work the rest of the time it's not them.

 

Either the MAP ECU isn't getting a good enough signal from the TPS to respond to cracking open the throttle or the MAP ECU isn't responding accordingly...because the MAP ECU like the EMB doesn't have an acceleration pump map I'd guess this was the problem...the only way to combat it to my mind would be to run slightly rich and see if it smoothes over the issue.

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No luck with any TPS% changes.

 

I found this on SF and it seems like it could be the same problem im having

Here's something strange... I've got a 3000 stall Level 10 converter (and trans) in my car and noticed when the rpms exceed 2700 (stock stall), below 10mph and above 3.5v throttle angle, my ECM will actually try to bring in the second turbo. This causes the boost to dip a moment and the car will hiccup and drive through it. Kinda crazy. I can design a logic gate to get it to stop because it bugs me when it does it.

Anyone know anything about this?

 

Scott

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