Why the Delay (Bogging) of Engine During Shifting?

[NSXY]

I have a toubling observation on my 95 NSX-T that bothers the #@%! out of me, and maybe someone knows want it's about.

When I am pushing the rpms up around 6-7K rpm during an acceleration (but no where near the 8K rpm limit), and I shift rapidly to the next gear, the engine bogs down, rather than powering forward. This bogging is very noticable, a delay of about 1-2 seconds with my foot on the accelerator, after which normal power resumes and the car powers forward.

This never happens when the rate of acceleration is medium to low, i.e. under normal driving conditions of slower shifting. It feels like temporary fuel starvation, but I don't see why that would happen. What is going on? What would cause this? Is the rev limiter out of wack and kicking in too early? Are the fuel injectors crudded up, so that I only notice the problem under high-demand conditions? Am I expecting too much of this car? RSVP Thanks!

 

[Joel Zoldessy MD]

Originally posted by NSXY:
I have a toubling observation on my 95 NSX-T that bothers the #@%! out of me, and maybe someone knows want it's about.

When I am pushing the rpms up around 6-7K rpm during an acceleration (but no where near the 8K rpm limit), and I shift rapidly to the next gear, the engine bogs down, rather than powering forward. This bogging is very noticable, a delay of about 1-2 seconds with my foot on the accelerator, after which normal power resumes and the car powers forward.

This never happens when the rate of acceleration is medium to low, i.e. under normal driving conditions of slower shifting. It feels like temporary fuel starvation, but I don't see why that would happen. What is going on? What would cause this? Is the rev limiter out of wack and kicking in too early? Are the fuel injectors crudded up, so that I only notice the problem under high-demand conditions? Am I expecting too much of this car? RSVP Thanks!

My 95 NSX-T has also exhibited this on occasion. It seems to happen on days when the overall performance seems sluggish. It does not seem to correlate with fuel-quality or status of injectors or fuel filter.
As new resident of Carlsbad, can you suggest where I might service my car?

 

[Edo]

A clutch that is slipping *might* exhibit the same problem. Your car spinning that many RPM's and then being subjected to a shift may not be able to keep the tranny connected to the rest of the driveline...I dont know how many miles you guys have on your car but someone who has 30K miles on a '95 could very well have that problem. Then again..I could be totally and utterly wrong.

 

[Lud]

Sounds like it may be TCS...? Try turning off TCS and doing the same acceleration run.

If the clutch were slipping the engine wouldn't bog. The symptom would be just the opposite - the revs would climb but the car wouldn't accelerate as fast as the RPM climbed.

 

[Tetsuo]

The rev will climb however the car will not move forward...rather it will feel like it is bogging.

At least this is what is like in my 93. Dali clutch and flywheel will be in tomrrow

Originally posted by Lud:
Sounds like it may be TCS...? Try turning off TCS and doing the same acceleration run.

If the clutch were slipping the engine wouldn't bog. The symptom would be just the opposite - the revs would climb but the car wouldn't accelerate as fast as the RPM climbed.

 

[Lud]

Originally posted by Tetsuo:
The rev will climb however the car will not move forward...rather it will feel like it is bogging.

That is true, but the original message said the engine was "bogging." That's not what happens with a bad clutch, where the engine actually revs faster as you noted.

 

[PAUL M]

I've noticed the same thing from my 95-t! I thought I was causing rear wheel spin from shifting hard and activating the tcs. Thats what it feels like so i never tried it w/out the tcs on. I'll check it out and let you know.I also went up a size on my rear tires i thought that may have been helping to cause it!

 

[NSXY]

Guys, Thanks for the ideas, but here are some clarifications:

1) Edo, Tetsuo and Lud: the car has 5,500 original miles, so it's probably not a dead clutch: the car has never been abused (I have never dropped the clutch to spin tires, and I probably never will).
2) Edo, Tetsuo and Lud: when I shift at high rpms, and the bogging occurs, the rpms do not increase, so it couldn't be related to a slipping clutch.
3) Edo, Tetsuo and Lud: the car did this with old OEM Yokos and also with new Dunlap SP9000s, so if it's related to the TCS, then it's not caused by a tire size or specific brand.
4) Edo, Tetsuo and Lud: I have not tried to duplicate the symptom with and without the TCS activated, so I'll try that next and report back ASAP.
5) Paul: it seems impossible that I could be activating the TCS by spinning the rear wheels at 80 mph! This car has torque, but not enough to spin tires at high speeds.
6) Joel, I have not yet looked for a best place to service my car in this area, because it has not yet needed service, but I have heard horror stories about Hoehn Acura in Carlsbad, so that people near the coast drive all the way to Escondido Acura to get better service. I have an open mind on this though. I suggest that you ask the same question by starting a new thread in this General Discussion section of NSX Prime. That way all of us in San Diego county can learn the best place.

 

[dswartz]

nsxy, I drag race and autocross my 98. I have absolutely no problem with bogging. Whether I speed shift or power shift (shift without lifting off the throttle) the car never bogs unless I hit the rev limiter. As you have already figured out, your symptom is not a sliping clutch, however, the tcs can do wierd things. Let us know your results without tcs. good luck.

 

[nsxtasy]

As new resident of Carlsbad, can you suggest where I might service my car?

No, but I can suggest two places where you might find the answer to that question:

1. The nsxca-southwest e-mail list. For more information, check out http://www.nsxprime.com/FAQ/Resources/emaillist.htm

2. Join the NSX Club of America (http://www.nsxca.org) and go to one of the monthly dinner meetings of the San Diego Chapter. For more info, contact Mark Allan at [email protected]

 

[hgunnerz]

I had the same experience on my 91 two days ago. I went to pass someone, downshifted and the engine bogged down at 5-6K RPM. Later I tried to reproduce it and noticed a brief flicker of the TCS light. Turned off TCS and the problem went away. I can't believe I am spinning the tires either, the TCS must be really sensitive.

 

[NSXY]

TCS Testing Conclusion:

The engine bogging does not occur when the traction control system is turned off (dash light on). Apparently, the traction control is super sensitive to changes in front/rear wheel speeds and even engages during the relatively minor twitchy wheel spin that may occur during speed shifting. Problem solved...

Thanks all.

NSXY