dog off the line?

L

ladman

Registered Member
Joined
17 July 2000
Messages
16
Location
CA
Is this car a dog off of the line? Since most
stop light drags are determined within the first few seconds unless you want to get crazy, how well does this car do from the line? Does it have to be revved up high and POPED to get a good launch? Will the trans modes help it any? Or does it have to play CATCH-UP to v8's till the v-tech kicks in before it makes the pass? No flame, just honest answers please. Thank you.
 
I have a 98 coupe that I currently drag race. The car is excellent off the line, mostly because of its weight transfer. However, because of its high torque multiplication (transmission & differential) it does not require hig revs. My best results off the line are achieved when I dump the clutch at about 3000 RPM. Best 60' times to date are 1.90 seconds. This compares favorably to my low 12 second corvette which produced 2.0 second 60' times. In fact, if I rev too high off the line I will produce 2.4 second 60' times. If I bog (by coming out at say 2000 RPM) I will produce 2.0 second 60' times. The bottom line is don't spin the tires, you'll just waste time.
 
I drag raced my NSX two weeks ago. I got SEVERE wheel hop off the line (the suspension is a very stiff RM Racing 1.5 inch drop) and ran 14.1 at 104 mph. Even with the wheel hop, that's inexcusable, considering the mods I have (see signature).

I love my NSX, but it's not a good straight-line car. Sure, the magazines have timed the NSX from 13.2 to 13.9 seconds. But do they mention that they drop the clutch at 6000 rpm? That's not a fair measurement of real-world performance.

I love the driving feel and livability of this car, but sometimes I really miss the off-the-line performance of a V8. I thought the supercharger would compensate for the NSX's lack of torque. Looks like I'll be making a trip to Comptech next Spring.





------------------
Red/Red '91. Comptech Supercharger. RM headers. Comptech exhaust. Short ratio gears. Ring and Pinion swap. RM racing suspension. 18/17 wheels/tires.
 
Yes. I ran 14.1 with everything in my signature. I shifted at 7700 RPM in each gear. Very disappointing...

------------------
Red/Red '91. Comptech Supercharger. RM headers. Comptech exhaust. Short ratio gears. Ring and Pinion swap. RM racing suspension. 18/17 wheels/tires.
 
My 98 coupe exhibits no wheel hop at all. If I came off the line at 6000 RPM I would spin the tires all the way through first gear! By the way, mine is normally aspirated and I come off the line at 3000 RPM. I ran 12.84 @ 110 mph last Sunday at the NIRA Fall Nationals at Raceway Park in Englishtown, New Jersey. In fact 3 of my runs were 12.84, 12.84, and 12.86. I think its an excellent drag car.
 
There is a real problem if you are in the 14s with a supercharger.

Your trap speed indicates that you have some good power but the time shows that there was a really bad launch. But even with the stiff suspension you should be able to avoid that kind of wheel hop. There is enough weight over the rear end.

Even if you launch softly the SC should give you enough power to run in the 13s. Your trap speed supports this.

The magazines don't drop at 6k - that would give a slower time because it would spin the tires too much.
 
Originally posted by Lud:
There is a real problem if you are in the 14s with a supercharger.

Your trap speed indicates that you have some good power.
Click to expand...

I definitely agree that 104 is plenty good mph to run 13's, but it's too low given his mods. His trap speed may indicate he has a real problem... A supercharged NSX with short gears/R&P etc should have traps at or beyond 110mph I'd think. Doesn't a 97+ NSX run traps of 104 stock? Dswartz is at 110 with normal aspiration.

multisync23 - I would pay close attention to how your car is acting. Does the engine feel like it's "holding back", have small hesitations, etc? Do you think you could be running lean and hitting some detonation? I don't know that much about NSX ECU's at this point, but perhaps the ECU is sensing problems and is retarding your timing?

You could try to hook up with an experienced driver to see if it's the driver or the car.. Or perhaps invest in some good tuning tools, like an EGT gauge so you can see how you're running. EGT's are an invaluable tool for determining how a car with forced-induction is performing. A small test you can try is to run race gas and see how the car responds, sometimes a borderline lean situation will be compensated for by higher octane.

A bad launch can kill your 1/4 mile time. Shifting that isn't fast enough will do that too. (Imagine, if you waste just 2 tenths of a second per shift, that's potentially .6 right there). But neither of those things are likely to cause MPH's to be that low compared to where they should be..

dswartz- That's a very nice 60-foot time, congrats.

Marc
97 NSX-T
 
Actually, the engine--though weak--is very smooth and hitch free. SpeedDemon, I agree with your point that my mph should be at least 110, good launch or not.

The ECU is a Dinan unit. It should have been swapped for a stock ECU when the S/C was installed. I'm looking into getting ahold of a stock one. Most aftermarket ECU's advance the timing. In my experience with domestic V8's, you want to retard the timing on a supercharged engine, not advance it.

Still, the car is a shadow of what it should be, and there's only a handful of mechanics that can very specifically diagnose this setup (all of them out of state).

------------------
Red/Red '91. Comptech Supercharger. RM headers. Comptech exhaust. Short ratio gears. Ring and Pinion swap. RM racing suspension. 18/17 wheels/tires.
 
A stock 3.0 will be in the 90s so I was thinking maybe if he had a bad launch and first couple seconds (i.e. lots of wheel hop) the number he got would be reasonable. It's certainly 15+ MPH higher than a 14 second car would get with a good launch.

I'd probably dyno the car - you shouldn't have to go out of state for that. If you see it's not putting out enough power, you know at least one problem to start working on. Who did the original supercharger install? Also, who did your suspension install?
 
The s/c was done by Comptech in Sacramento. The suspension was done by NSX Modified in LA.



------------------
Red/Red '91. Comptech Supercharger. RM headers. Comptech exhaust. Short ratio gears. Ring and Pinion swap. RM racing suspension. 18/17 wheels/tires.
 
Originally posted by multisync23:
The ECU is a Dinan unit. It should have been swapped for a stock ECU when the S/C was installed.
Click to expand...

That makes sense, and could be the source of your problems. I suggest getting a stock program in quickly and staying away from the boost until you do, you don't want to risk possible detonation.

If you have the money, it's never a bad idea to invest in an EGT (Exhaust Gas Temperature) gauge. An EGT gauge is a pretty fool-proof indicator of how you are running (more so than an A/F meter). If your timing is being retarded, or you are running too lean, that will quickly show up on an EGT gauge as excessively high temperatures. (It also lets you know when you're running too *rich* in a 1/4 mile pass). If you want to go this route let me know and I'm happy to give you tips on EGT installation and use. My personal choice is the Greddy electronic unit, it's a little over $200, is fully electronic, has peak-hold memory, and you can also set it to warn you if your temps exceed the limit you choose on the guage.

Trying race gas might also give you an indicator, though it's not an iron-clad test. If you suddenly found your car running way stronger after increasing your octane, that could point to you having too much timing or otherwise running a little lean. When I run race gas for a 1/4 mile run, I have to adjust my fuel settings typically 10% leaner for most of my RPM range even though I RAISE my boost for the track.

What fuel system mods do you have? When was your fuel filter replaced?

By the way, I'm not trying to alarm you or anything, whatever's holding you back could be simple and it could be something that's not really harmful to your engine. But, better safe than sorry, right? Get ye to some EGT's readings, and a dyno!
smile.gif


Good luck,
Marc
97 NSXT
95 Eclipse GSX, 11.81 @ 119mph full weight


[This message has been edited by SpeedDemon (edited 14 October 2000).]

[This message has been edited by SpeedDemon (edited 14 October 2000).]
 
SpeedDemon-
The Dinan chip and S/C have coexisted fine for 7200 miles; it's a safe, though slow, setup. What I need to do is find a local owner who'll swap ECU's with me. I went to an exotic car dealer today to propose that I swap my Dinan for a stock ECU in one of their NSXs and they darned near kicked me out of the place (I _hate_ car dealers).

An EGT guage would be a good idea, but first I'd like to put a boost guage on the car.

I haven't thought about replacing the fuel filter. I'll go through the receipts of the previous owner. The fuel system is stock. That didn't seem right to me, so I contacted Comptech and they said the supercharger was designed to work with the stock fuel system. The guy I bought the car from has another supercharged NSX. It felt significantly faster when I drove it.

The only difference between his and mine was larger injectors from a Prelude and an inline pump. Still, Comptech insists the fuel system is not a bottleneck.



------------------
Red/Red '91. Comptech Supercharger. RM headers. Comptech exhaust. Short ratio gears. Ring and Pinion swap. RM racing suspension. 18/17 wheels/tires.
 
Originally posted by multisync23:
I haven't thought about replacing the fuel filter. The guy I bought the car from has another supercharged NSX. It felt significantly faster when I drove it.

The only difference between his and mine was larger injectors from a Prelude and an inline pump. Still, Comptech insists the fuel system is not a bottleneck.
Click to expand...

In general I'm sure their package must work fine given the number of sales they've had. But of course that doesn't mean there couldn't be an issue with your car specifically with regards to fuel. If your fuel filter was clogged, you wouldn't get the fuel you needed. Perhaps your fuel pump isn't quite getting the electrical juice it needs and isn't putting out as much pressure/flow as it should.

As you pointed out, the guy who had the car before you has put a more robust fuel setup on his car, and, his car pulls stronger. And there's no difference between his car and yours except fuel.. Seems to point to fuel.

Do you know what size injectors the Prelude injectors are? Is the in-line pump a replacement for or in addition to the factory pump? I guess the factory ECU is compensating for the extra fuel when not under boost via closed loop/learning.. ?

Hope all works out for you. When you find the problem, would love to know what it was.

Best,
Marc
97 NSXT
95 Eclipse GSX, 11.81 @ 119mph
 
He said he _thought_ they were Prelude injectors. He didn't know what kind of pump was installed. He just told me to call Comptech, but Comptech said they'd never sell him a pump and injectors. Weird.

I'm going to dyno the car soon. Hopefully, Scott in Hillsboro (another NSXprime poster) can bring his car too, so we can swap ECU's to prove:

1. The standard ECU improves performance in my supercharged car.
2. The Dinan chip improves performance in a stock car.

The results should be helpful for anyone here considering an ECU swap.

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Red/Red '91. Comptech Supercharger. RM headers. Comptech exhaust. Short ratio gears. Ring and Pinion swap. RM racing suspension. 18/17 wheels/tires.
 
DON'T OVERLOOK THE INJECTORS!!! I have another car that ran terrible for 3 years. Everyone tried every possible tuning trick. Luckily, it only took me three years to find someone who said "your injectors are the wrong resistance for your computer!" As a result, I put back the stock injectors and the car now runs fine.
 
Multisync23,
I'm a member of the Florida Chapter and we have a couple of S/C equipped cars in the club. We've held a couple of "Dyno Day" events during the year. Both of these S/C cars were "below expectations" prior to some diagonostics. Turns out the fuel pumps were the culprit. You may want to have your pump checked to make sure you're getting adequate fuel pressure. We had another car that was NOS equipped and "below par"...same story. A new fuel pump and follow up dyno numbers confirmed this diagnosis. Best of luck to you...I'm sure some lower ET's are in your near future!
 

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