More 1/4 mile stuff

M

McAttack

Experienced Member
Joined
15 May 2002
Messages
321
Location
Boston, Mass
Up until this month, I haven't run more than 1 consecutive 1/4 mile since I was 19. AND IT SHOWS! Went to the strip in NH yesterday. The best I got was 12.79 at 112 mph. Yuck. 60' was 1.9 Just can't seem to get my launches down. I don't recall it being this difficult. Must be getting old.

I thought I saw an earlier post that said if the tires are DOT, go with closer to OEM. Any thoughts? I have 2 sets at the moment. Both are S03's 285/30/18(R) and 245/40/17(F)
And another set 245/40/17 and 225/45/16 Tire pressure was 20 psi yesterday.

I've gotten some good advice in archives ie. "power shifting" and lightening the car. Can anyone chime in on tires?

Recent dyno #'s showed 332lbs of torque at 4000 rpm and 408.1 hp at the wheels. I was hoping to run sub 12 sec. Realistic?
 
Originally posted by 8000RPM:
I am kind of puzzled that you are only getting 112 mph considering that you have over 408 rwhp...

Something doesn't add up here.
Click to expand...

Well, is the Avatar of the car in question? All those "aero" parts are nothing but air brakes in a drag race. If it was running the larger wheels/tires mentioned that certainly didn't help. And the rest may be a lack of area under the power curve. After all, you're only at peak HP for a blink of an eye. What's it got from 5k-8k?
 
Originally posted by 8000RPM:
I am kind of puzzled that you are only getting 112 mph considering that you have over 408 rwhp...

Something doesn't add up here.
Click to expand...

Something definitely isn't adding up. He should be closer to 118-120mph.

And that 1.9 60-foot time is nothing to complain about either. A 1.9 and with the power you say the car has, you should be knocking on 11-second quarter mile times.

Are you dragging a boat anchor when you race?
smile.gif
 
Originally posted by 8000RPM:I am kind of puzzled that you are only getting 112 mph considering that you have over 408 rwhp... Something doesn't add up here.
Click to expand...

Peak power is meaningless. "Power under the curve" is what matters. Lets see the dyno plot, then we can have a better discussion.
 
Here is the dyno chart w/50 shot NOS. Given the temp that day, etc. I was told adjusted RWHP would be 423.
http://www.ipsboston.com/staff_archives/dynorun1_ACS_Racing.jpg

The temp at the dragway last Wed was cool, about 65 degrees. Final note, I did about a dozen runs, most at about 13 flat so it wasn't a fluke. I'm not ruling out driver error but if the car should be at about 11.2, it can't be ALL me.

I am going to try one more time with the 245/40/17's instead of the 285/30/18's (although the diameters are virtually identical). I'm also going to work on power shifting, a better launch and lightening the car a bit more (Anyone know the best flavor SlimFast?)

At this point, I'd be happy if I broke 12.

Final question: Am I chancing significant damage doing so many runs at once? Primarily engine wear probs? Thanks
 
Hey, nice looking power curves! The NOS sure boosts the low end. At what RPM does the NOS stop?

But that still leaves the mystery of the 112 mph trap speed, which is way low for the chart you have. Driver technique doesn’t have a big influence on trap speed unless you do something like shift too early. Are you using all 8k? Did you forget to turn off the TCS? As was said by others earlier, something doesn’t add up here, and I’m not sure my prior comments about wheels/tires & aero can account for it either. Then again, if you have that bei wing and it’s adjusted wrong it could be quite significant.
 
Well, the area under the curve seems quite large to me. Very nice curve, btw.

You should definitely be getting closer to 120mph than 110mph.

I also agree that a 1.9sec 60' time is quite good for a street car, which only adds to the mystery.
 
The avatar is what the car WILL BE in the Spring. It's from Marga Hills and I liked it because it's the same color as mine. Right now, all stock body. TCS was off for my best run(although I tried it on too).

RE: Technique, I am using all 8k. Had to use 5th if that matters. Stock gears. Some runs I messed up the launch. Others I hit the rev limiter or shifted too soon. My best run 12.79, was as close to perfect as I could get. Did everything well. Which is why I'm stumped. If power shifting doesn't knock a second off my time, I'm clueless.

FYI....one last resort I almost did was ask one of the pros to run it once or twice to rule out the driver. (At NE Dragway on Wednesdays between 1 - 5 p.m. you can run as much as you want. Given they only let 20 cars run during this time it was pretty funny. One NSX and 19 dragsters! One car actually did a 4.7 1/4 mile!!!!! For a moment, I almost parked my car and sat in the stands!) Anyway, I don't think I could have gotten anyone as those guys were working and this was their job. One man's work........

Any thoughts or advice let me know. Thanks.
 
Wait a minute, 5th gear at 112? That's 3rd gear with a stock 5-spd and low in 4th with a 6-speed. Even with a .455 and the close gears the 5-spd should do 120 in 4th, and the 6-spd w/.455 should be good for ~116 in 4th. (all above assuming stock overall diameter rear tires, and yours are very close) So the only way it should even be close is a 6-spd w/.455 final drive but even then I doubt 5th is required. Hmm..., are you just messing with us?
smile.gif
 
Originally posted by sjs:
Wait a minute, 5th gear at 112? That's 3rd gear with a stock 5-spd and low in 4th with a 6-speed. Even with a .455 and the close gears the 5-spd should do 120 in 4th, and the 6-spd w/.455 should be good for ~116 in 4th. (all above assuming stock overall diameter rear tires, and yours are very close) So the only way it should even be close is a 6-spd w/.455 final drive but even then I doubt 5th is required. Hmm..., are you just messing with us?
smile.gif
Click to expand...

NO!!!!!!

EVERYTHING I have said has been accurate!!!
I am the 3rd owner of the car and it had 14k miles when I got it but there was no mentrion that anyone did anything to it. As far as my experience, it IS as I have said. I'm lost. I obviously have to go again. This time I will ask Nimbus to join me. Maybe he can enlighten the situation if he's available. I know he has a lot of experience in different types of driving.
 
Maybe you can list us the mph at the point of your shifts? Even ballpark numbers would work. On a stock 5-spd tranny, you should be shifting around 40 mph to 2nd and 80 mph to 3rd. You should be able to hit 110, you will be very close to the redline.
 
Originally posted by Ag NSX:
Maybe you can list us the mph at the point of your shifts? Even ballpark numbers would work. On a stock 5-spd tranny, you should be shifting around 40 mph to 2nd and 80 mph to 3rd. You should be able to hit 110, you will be very close to the redline.
Click to expand...

Honestly I can't recall. But I will post the numbers from the slip later. That I did keep.
 
hey mcattack is that the back end of your car in your avatar?
eek.gif
looks awesome any more pics?
 
I know this thread is getting a bit tired even for my attention span but any thoughts are welcome and appreciated.

My numbers for my best run so far are as follows:

R/T: .535
60': 1.910
330 : 5.433
1/8 : 8.320
MPH : 87.07
1000: 10.754
1/4 : 12.790
MPH : 112.54
 
Originally posted by McAttack:
I know this thread is getting a bit tired even for my attention span but any thoughts are welcome and appreciated.

My numbers for my best run so far are as follows:

R/T: .535
60': 1.910
330 : 5.433
1/8 : 8.320
MPH : 87.07
1000: 10.754
1/4 : 12.790
MPH : 112.54
Click to expand...
mac,next time you go out to the track relax and approach it as a fun gig.but heres the point I want to make. forget about your hp, torque, body lines and concentrate on the tree.forget about the other car.gut reaction to me is your whole shot.the tree comes down in .5 increments.if you wait until you see the green to launch you have already lost.reaction time for driver and car is about .5, see where im going? try launching just after the last yellow.just after.you will see a big differance.due to reation of you and car launching off the last yellow leaves the line on the green just as it hits. if you are already launching before the green pay no attention to the post.if not give it a try.lastly dont get to quick off the last yellow or you will disqualify.this WILL shave a half a second off your time
david
 
BadCarma, not bad advice for getting those times down, but the real issue here is trap speed. No amount of skill at the lights will translate into more MPH, and that's the main clue to a problem. I still can't figure the gearing thing either unless it was really 4th. (hey, it's pretty busy out there, a guy could lose track).
 
Drive into your lane, do a slight wheel spin to clean the dirt off the tire's, "not a burn out" unless you are running brackets don't worry about your reaction time concentrate on leaving the line. Reaction time has nothing to do with the ET and MPH, you can sit their as long as you don't break the beam for as long as you like.
 
OK, I ran this through a simulator. Making assumptions of a stock 6-spd and a gross weight of 3020 without driver, 400 hp and 330 lb-ft. Your mix of boost & NOS makes it impossible to match your power curves with this tool but I got as close as I could. That produced a trap speed of 117.1 mph, which seems a bit more reasonable. Switch to a .455 R&P and it drops all the way to 114.2 because there is a shift just short of the finish.

But weight is a big factor. What do you weigh? Have you tossed out the spare tire & tools? How heavy are those wheels & tires compared to stock? Just add 200 pounds on top of that .455 R&P and it spits out a 112.72. The lousy help on this thing explicitly says that car weight is less driver & fuel but I can’t find what their assumptions are about those items or how to set them.

My guess is that you have the .455 R&P and your car is a bit overweight. It’s the only thing that fits.


Hey Gerry, do you have some good numbers I can run through this simulator to see how close it gets?
 
SJS, judging by his reaction time and 1.9 60foot time, i dont think his driving skill is an issue.

he may be able to slightly decrease his et, but his mph will be the same, within 1-2 mph.his driving skill is definately not causing him to lose 5 mph somewhere in the quarter.

btw, .500 is a perfect r/t time. id be very happy with a .535.

i'd say judging by his timeslip, he's pretty much at the top
 
Originally posted by ALLAN:
SJS, judging by his reaction time and 1.9 60foot time, i dont think his driving skill is an issue.

he may be able to slightly decrease his et, but his mph will be the same, within 1-2 mph.his driving skill is definately not causing him to lose 5 mph somewhere in the quarter.
Click to expand...

That's been my point from the beginning. Did I start typing in Swahili again?
wink.gif
 

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