Mysterious return of power

[Dhalsim]

Last month I replaced my Topspeed headers with a Comptech set and installed a new center exit exhaust.

After the install was done I of course took the car for a drive and the first thing I noticed of course was the crazy loud exhaust. I love it and it sounds friggin mean but it took some getting used to. However in the back of mind I kept thinking the car felt slower but that didn't make any sense so what I thought was happening was that since the exhaust was so loud I was not pushing the car as hard because it was screaming at high revs and I kept having the idea that the engine was gonna blow up. Just a psychological issue really since I never really liked pushing the car beyond 7k. So I thought everything was good.

However on Saturday I installed some new coilovers and took the car for a long drive to see how it felt. I parked the car for a couple hours and then when I got back in I proceeded out of the parking lot and down the street and just cruising at about 40 I suddenly felt a slight surge in power (the car kinda slightly lurched forward) and then immediately after that the car felt so much faster. I suddenly realized that the car WAS actually slower after the header/exhaust install. And now suddenly the car felt fast again. It was like I was felling the CTSC for the first time again.

So what happened?

Is it all in my head? I don't think so. The car felt so much better all the way home.

I discussed this with a friend and could only come up with a few possibilities as follows:

1. Stuck caliper. Could it "un-stick" itself?
2. Hand brake not releasing completely?
3. Clogged injector that suddenly became unclogged. Possible??
4. O2 sensor bad and car was in limp mode this whole time and somehow went back to normal. hmmmmm....is that even possible? There would be a code right?

Thinking back I remembered that I was making a left turn onto the street the other day and the TCS light came on. I thought this was strange cause I am running the OEM wheels. So i stopped the car....turned it off and back on again. TCS light was off and everything back to normal and never gave it another thought. Could this be a clue to the regain in power?

I also did not change the O2 sensors when I did the header install. Not sure if this matters but I assume a bad O2 sensor could effect the engine power.

Tonight I checked for codes but there were none.

So I would like to hear what Primers think could have happened and whether or not I should be concerned or what to check.

 

[biscuits]

Since you changed your exhaust maybe your ecu needed time to recalibrate And adjust fuel mix to compensate for the additional exhaust flow?

 

[docjohn]

could your ctsc belt be slipping?

 

[Honcho]

Maybe you were running on 5 instead of 6? A cylinder coming back online would explain the instant increase. But, I'm pretty sure a cylinder misfire would throw a code...

 

[02#154]

If it was a sensor that somehow got back into spec, the code(s), if any, could have cleared themselves if you drove sufficiently long enough.

I say enjoy the return of power and if it happens again you'll have an easier time diagnosing the trouble at that time than you probably will now, in it's current state, trying to guess what happened in the past.

J

 

[RYU]

I've recently installed my new two-stage exhaust that has a "loud/free-flow" mode. I'm always a bit cautious to express what my butt dyno feels because the increase in volume does throw off the experience.

I did reset my ECU so that the STFT and the LTFT resets to 0. I've been driving it for 300 miles so far and I think the ECU is finally starting to settle down and fwiw it does feel faster. Though, not sure if the change was as dramatic as your situation. I can't say for sure until it's dynoed and since we have OBD1 cars it's not possible to read the STFT & LTFT to see what they're really doing in closed loop. Keep in mind a more free-flowing exhaust could cause your setup to run just a few tenths leaner at the onset.

This thread is a bit of a witch hunt though. Needle in a haystack until you can decipher more information.

 

[Dhalsim]

Since you changed your exhaust maybe your ecu needed time to recalibrate And adjust fuel mix to compensate for the additional exhaust flow?

I didn't think about that. I suppose that's possible (can anyone confirm this?). How long or far would you normally have to drive until the ECU "re-learned" things?

could your ctsc belt be slipping?

I suppose but what would suddenly cause it to not slip anymore? But I will check the tension later JIC.

Maybe you were running on 5 instead of 6? A cylinder coming back online would explain the instant increase. But, I'm pretty sure a cylinder misfire would throw a code...

Yeah I would expect some kind of code. Just wondering....... if a cylinder did stop working would the injector still be spraying fuel?

If it was a sensor that somehow got back into spec, the code(s), if any, could have cleared themselves if you drove sufficiently long enough.

I say enjoy the return of power and if it happens again you'll have an easier time diagnosing the trouble at that time than you probably will now, in it's current state, trying to guess what happened in the past.

J

I think this is similar to what Biscuits said and I hope that's what it is. Can anyone confirm that a code would automatically clear on its own?

I've recently installed my new two-stage exhaust that has a "loud/free-flow" mode. I'm always a bit cautious to express what my butt dyno feels because the increase in volume does throw off the experience.

I did reset my ECU so that the STFT and the LTFT resets to 0. I've been driving it for 300 miles so far and I think the ECU is finally starting to settle down and fwiw it does feel faster. Though, not sure if the change was as dramatic as your situation. I can't say for sure until it's dynoed and since we have OBD1 cars it's not possible to read the STFT & LTFT to see what they're really doing in closed loop. Keep in mind a more free-flowing exhaust could cause your setup to run just a few tenths leaner at the onset.

This thread is a bit of a witch hunt though. Needle in a haystack until you can decipher more information.

OK.....so you say about 300 miles till the ECU settled down. I have probably just about driven 300 miles since changing the headers and exhaust.

But my situation is that I thought the car felt slower after the header/exhaust install and in fact I was right...........



Thanks everyone for your ideas so far. If anyone else wants to chime in I'm willing to hear your thoughts.



The header/exhaust change was pretty significant I think. I went from Topspeed headers to Comptech, which the Comptech are said to be much better. And I went from a somewhat restrictive exhaust set up (was never ideal for a CTSC car) to a very free flowing exhaust with no cats.

 

[socold57]

how do you reset an ecu btw

 

[BD]

how do you reset an ecu btw

unplug and replug the clock fuse.

 

[MvM]

You mentioned that you installed a new exhaust on your car.

I remember that when I put the Taitec GTLW exhaust on my car, the first two weeks of driving (and even perhaps longer), I would have a very fine coat of fibers on my rear bumper after a drive. These seemed to be loose fibres from the inside fibre packing of the Taitec being blown out of the exhaust.
I had to wash these away every two days or so and at the time as I was worried they would damage the paint on the car.

If you are runnning a CT your exhaust pressure might even be higher and somehow something got stuck in the tubing, holding your car back. After it was finally freed, you car felt better again.
Perhaps a bit of a strange story, but the only thing I got think of.

The ECU story could be it too, but I would think that the ECU is learning over time, making small increments. not just switch over from one second to the other.

 

[RYU]

Did a bit of testing last night... I manually forced my bypass valves closed in my exhaust. I drove around in quiet mode for a few miles while still boosting all over the place.

It definitely felt faster but I know i'm putting out less power. The psychological effect of a louder exhaust is a strong one me thinks!!

I know this sounds crazy and totally unscientific but I needed to drive to the gym anyway

 

[Dhalsim]

Did a bit of testing last night... I manually forced my bypass valves closed in my exhaust. I drove around in quiet mode for a few miles while still boosting all over the place.

It definitely felt faster but I know i'm putting out less power. The psychological effect of a louder exhaust is a strong one me thinks!!

I know this sounds crazy and totally unscientific but I needed to drive to the gym anyway

That's cool but like I already said the loud exhaust didn't make me think I was going any faster as I already said I felt like I was going slower and it turns out I actually was.

 

[RYU]

No, I agree with you and perhaps you misread what I wrote. My loud exhaust makes me feel like i'm going slower. When I quieted it down it felt more torquey and faster. I hate making observations w/o presenting hard facts so I can't tell you what really going on. A few folks have expressed this same observations when they put on their stock exhaust back on. Logically it doesn't make sense. Any exhaust backpressure is no good.

To me it's psychological.

Your issue may be different since you're saying the change was abrupt and obvious. Mine isn't so much.

 

[Dhalsim]

No, I agree with you and perhaps you misread what I wrote. My loud exhaust makes me feel like i'm going slower. When I quieted it down it felt more torquey and faster. I hate making observations w/o presenting hard facts so I can't tell you what really going on. A few folks have expressed this same observations when they put on their stock exhaust back on. Logically it doesn't make sense. Any exhaust backpressure is no good.

To me it's psychological.

Your issue may be different since you're saying the change was abrupt and obvious. Mine isn't so much.

I hear ya

 

[Vega$ NSX]

Perhaps the dead hooker you had stashed in your trunk fell out and reduced your vehicle weight?

 

[Dhalsim]

Perhaps the dead hooker you had stashed in your trunk fell out and reduced your vehicle weight?

That only happens in Vegas.

 

[LoveNSXs]

Yeah I would expect some kind of code. Just wondering....... if a cylinder did stop working would the injector still be spraying fuel?

Yes, if a cylinder is not firing, it will still spray fuel in there. It happened to m for the longest, though for different reasons. I had a bad/clogged up sparkplug/coil pack from water leakage. I smelled raw fuel everywhere. When it dries out or got cleaned out, the cylinder would be firing again and burn the fuel.