I installed a DC Sports header and Taitec GT Lightweight exhaust on my '91 and visited the local dragstrip tonight to test the new mods. Much to my dismay, the car was actually slower than it was before. My previous best was 13.0x @ 107 with the stock H/E. My best run with the new parts was 13.2 @ 104. The lower trap speeds somewhat demonstrates a horsepower decrease. I've read somewhere that I should reset the ECU to "learn" the new parts. Is this true? Or is there just something else wrong with this picture? Any input would be greatly appreciated. Thanks --Paul
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Car slower after header & exhaust install
- Thread starter RedlineRex
- Start date
Paul,
I cannot say anything about your drag-results because the circumstances might have been different than before.
You should not have to reset the car to have the CPU to learn the new hardware.
The only way to know if you have lost power or not is/was to dyno the car before the install and then again after. Actually, even if the HP would stay the same the car would have lost some weight with the headers and exhaust so it should have been faster.
I cannot say anything about your drag-results because the circumstances might have been different than before.
You should not have to reset the car to have the CPU to learn the new hardware.
The only way to know if you have lost power or not is/was to dyno the car before the install and then again after. Actually, even if the HP would stay the same the car would have lost some weight with the headers and exhaust so it should have been faster.
MvM, I agree the the conditions may have been a little different, but not much. Same track, air temp within 5* F of previous outtings. Same 60' times (2.0xx).
The only other difference is weight of the car, the 13.0xx run was with the passenger seat removed. The runs last night were with it in, but the weight reduction of the new header and exhaust should have nearly offset the weight of the seat. Although the conditions weren't exact, they were close enough to have expected a better performance.
I'm wondering if anything else could possibly be going on.
The only other difference is weight of the car, the 13.0xx run was with the passenger seat removed. The runs last night were with it in, but the weight reduction of the new header and exhaust should have nearly offset the weight of the seat. Although the conditions weren't exact, they were close enough to have expected a better performance.
I'm wondering if anything else could possibly be going on.
Do you have other mods? Were you consistently running 13.0x before? A 13.0x seems very quick for a stock 91 NSX.
RedlineRex said:
Yeah you should reset your ECU anytime you change something, as it will re-learn your drive habits as well as other characteristists of sensors etc....
Do you Dyno before and after? That would yield the changes? I would say runing 1/4mile isn't really going to be acurate because of various track and enviormental changes.
dlongo,
I was able to hit the 13.04X only once, but I did manage to pull a couple 13.10X's to somewhat back it up. My setup at the time was 5sp tranny w/ CT R&P, CT PG2 clutch, Nitto drag radials and a cheapo cone filter intake. I removed the spare tire, jack, engine cover and passenger's seat for weight reduction.
RudeBoy_baby_NSX,
I will go ahead and reset my ECU tonight and hopefully it relearns the new setup. Unfortunately, I did not dyno the car before. I just figured that I should have gained the 15-20hp increase that everybody else did. My very accurate butt-dyno didn't seem to feel much of an increase in anything other than sound level. I'll try to visit the track next Wed nite to see if resetting the ECU helps at all. Any other suggestions?
I was able to hit the 13.04X only once, but I did manage to pull a couple 13.10X's to somewhat back it up. My setup at the time was 5sp tranny w/ CT R&P, CT PG2 clutch, Nitto drag radials and a cheapo cone filter intake. I removed the spare tire, jack, engine cover and passenger's seat for weight reduction.
RudeBoy_baby_NSX,
I will go ahead and reset my ECU tonight and hopefully it relearns the new setup. Unfortunately, I did not dyno the car before. I just figured that I should have gained the 15-20hp increase that everybody else did. My very accurate butt-dyno didn't seem to feel much of an increase in anything other than sound level. I'll try to visit the track next Wed nite to see if resetting the ECU helps at all. Any other suggestions?
I'm not Drag Strip Expert, nor I've been one since I don't really care for drag racing, anyway, there's some of the reason you have a slower car after the exhaust/ header installation.
The Reset ECU thing could have been a reason, but since you are driving in 60 degrees, I wouldn't think it would matter much.
Now I suspect the best time you obtained before your H/E installation would probably couple months ago, right?
The tires could have been worn a little, thus not gripping as good as before... In same theory, the pavement could have been different ie, some guy who ran before you put some tacky tire compound on the pavement thus increase your traction of the tire which gave you a better time... It could be the other way around, like I said I'm no expert on the 1340 ft...
Now talking about the removing seat, I would say the seat at least weight more than 50 lbs... which your exhaust weight saving is not even close to that, thus you have a lighter weight to get a better accelaration.
Also, when you remove the seat, you were taking weight off from the center of the front and rear wheels... while the Exhaust removing weight "behind" the rear wheels. I believed more weight you carried at the rear gives you better traction/acceleration. (That's what the Porsche guys said.)
just my opinion.
The Reset ECU thing could have been a reason, but since you are driving in 60 degrees, I wouldn't think it would matter much.
Now I suspect the best time you obtained before your H/E installation would probably couple months ago, right?
The tires could have been worn a little, thus not gripping as good as before... In same theory, the pavement could have been different ie, some guy who ran before you put some tacky tire compound on the pavement thus increase your traction of the tire which gave you a better time... It could be the other way around, like I said I'm no expert on the 1340 ft...
Now talking about the removing seat, I would say the seat at least weight more than 50 lbs... which your exhaust weight saving is not even close to that, thus you have a lighter weight to get a better accelaration.
Also, when you remove the seat, you were taking weight off from the center of the front and rear wheels... while the Exhaust removing weight "behind" the rear wheels. I believed more weight you carried at the rear gives you better traction/acceleration. (That's what the Porsche guys said.)
just my opinion.
RedlineRex said:
Having raced at the drag strip with my civic shows that weather and track conditions can have a HUGE impact on car times. From driving a 12 sec. civic, on some days I'm lucky if I crack a 13.5....
How were the track conditions?
Weather?
Just curious.
-x-
I'd check at least a few things:RedlineRex said:
a) first the obvious -- any leaks in the plumbing ?
b) is the combo of DC Sports (old Comptech) header and the Taitec GT-LTW exhaust a good one? Headers make things more free-flowing; whether the exhaust combo gives you enough back-pressure to not sacrifice low-end torque?
c) were you using the same launch and shift points in the before/after 1/4 mile runs?
Thanks for all the responses gentlemen. Track conditions certainly do play a big part in drag racing as it would in all forms of motor sports. Lack of traction was not issue as I was running drag radials and there was no excessive wheel spin. The first run of last night was in low 90's weather and the last run was somewhere in the mid-to-low 80's. The 13.0-13.1 runs I am comparing to were with the same drag radials in low 80 degree weather. The 60' times were nearly identical showing that the launches are fairly consistent. The only variables that were different are the passenger seat in the car (+50lbs), the new exhaust (-20lbs?, free flowing) and the new header (hp gain, and maybe a bit lighter).
cojones,
- I have not seen/heard any exhaust leaks of any kind, I'll climb under the car to make sure.
- I'm not sure if this H/E combo is proven to work great together, but I figured that the lack of low end torque would have been noticed only in the launch as the rest of the run would be in the mid to upper rpm band (5k+ rpm's).
- exact same launching and shift points.
cojones,
- I have not seen/heard any exhaust leaks of any kind, I'll climb under the car to make sure.
- I'm not sure if this H/E combo is proven to work great together, but I figured that the lack of low end torque would have been noticed only in the launch as the rest of the run would be in the mid to upper rpm band (5k+ rpm's).
- exact same launching and shift points.
I think the seat is ~42lbs, not 50+. The headers do save a good few ponds over the cast manifolds. Some exhausts save a bunch, others not much, not sure about yours.
I've been consistently skeptical about most claimed power gains from these mods. The closest thing I've seen to real tests were those done by SoS which were quite good, but I continue to beleive that most people underestimate the tuning that goes into a properly designed exhaust system.
And once again I'll note that the best way to document results is with a decent logging accelerometer such as the G-Cube because it records actual rate of acceleration at all speeds in any gear. It truly tells the story where the rubber meets the road, in many ways even better than a chassis dyno, and you don’t need to wait for Friday nights at the strip or abuse the hardware to take measurements.
I've been consistently skeptical about most claimed power gains from these mods. The closest thing I've seen to real tests were those done by SoS which were quite good, but I continue to beleive that most people underestimate the tuning that goes into a properly designed exhaust system.
And once again I'll note that the best way to document results is with a decent logging accelerometer such as the G-Cube because it records actual rate of acceleration at all speeds in any gear. It truly tells the story where the rubber meets the road, in many ways even better than a chassis dyno, and you don’t need to wait for Friday nights at the strip or abuse the hardware to take measurements.
Weather keeps on getting mentioned, but answer only comes back that temp was close and track was dry. Humidity and barometric pressure will have significant impacts on horsepower. And was there a slight breeze either time. Head wind one day, tail wind the other. I think your times are close enough, it's hard to determine the true cause of the differences. Too many unknowns.
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