neat

I can't get my 91 to sixty foot worth a damn. The car is basically a stock 1991 6 speed, with nitrous, a McLeod twin disk clutch, and ET street radials. On the bottle the car is making ~330 RWHP and ~450 RWTQ.

Even the higher HP (475 RWHP/620 RWTQ) 1992 ZF6 vette in my signature never never cut a sub 1.8 sixty. I could launch that car at 6,000 RPMs with ET Drags on the back, and still only cut low 1.8's. I am obviously doing something wrong, so here I come, seeking knowledge.

Prior to the nitrous (250 RWHP/340 RWTQ) and without the ET street radials, my best time was a 13.9 @ 101, with a 2.2 sixty. I have been as low as 1.9 on the street rubber, but 2.0-2.2 is my average. When I do manage the occasional 1.9 the ET never seems to come with it for some reason.

With nitrous, on the street rubber, I ran a 13.5 @ 107, with another 2.2 sixty. I had to activate the nitrous in second gear because a first gear activation just blew the tires off. I was expecting to pick up close to .1 for every 10 RWHP added via nitrous, so I was kinda let down when I only picked up .4, but I did pick up 6 MPH.

I thought for sure the car would go low 13's with the nitrous and ET street radials, so I bought a pair 275/40-17's and had them mounted on the stock wheels. I went to the track and made a couple passes on motor to get used to the tires. I started with 35 PSI in the radials. Anything less than a 3500 RPM clutch release resulted in the car bogging down pretty badly, giving sixty foot times in the 2.1-2.2 range. 3500+ RPM clutch releases spun the tires to the point where I tried to peddle the throttle a bit to get them to hook. This did net a bit better average 60 foot time of 2.0-2.1. I aired the ET radials down in 5 PSI increments all the way to 20 PSI with no change in 60 foot time or perceived hook. My best NA pass of the day was 14.1 @ 99, it was hot with high humidity though so I think I am pretty much on par with my previous best time of 13.9 @ 101. Again though, I was slightly dis-heartened that with the new tires I didn't manage a new best 60' time, or new best overall NA ET.

I opened the bottle, dropped the PSI to 18 and made another half a dozen passes. Launching on the juice at about 3,000 RPM's seemed to yield the best results with an average 60 of 2.0 and a single 1.9 pass. The ET was no better, the same 13.5 that I ran with street tires, and the MPH actually went down to 105 from the 107 I ran on street tires.

I was able to use the nitrous in first gear, where I wasn't on street tires, so I thought for sure I would see an ET improvement. The way it sits right now, the radials were a waste of money. I am cutting the same sixty foot times with them as I was on street tires, only it's immensely harder on the drive train. I have tried regular, non-radial ET streets on other cars and they always dead hook, even on cars making almost twice the HP I am. Maybe I should of just bought some 16 inch wheels and went with those?

I don't have a line lock, so I am only able to do a short burnout.

Any advice would be appreciated.

EDIT: This post is in the drag racing section too, but there aren't too many C4 guys in there. The C5 guys are trying, but they don't seem to understand that I can't rev my TPI 350 to 6000+ RPM's so I'm not 100% sure their advice is my best route.

rocco16

Maybe it's the track??

Larry
code5coupe

neat

My ego loves that idea, but I really doubt that's the problem. There are a couple 6 speed C5 guys there that cut pretty consistent 1.6's with BFG drag radials. Their cars are making a lot more power than mine though.

ALLT4

It doesn't make sense. The only thing I can think of is you're still spinning even with slicks. Might be time to get out the shoe polish and paint a line on your slicks, have someone do a video of your launch. Watch it slowed down and see if there's spinage.

Hard to believe you wouldn't feel it though. Anything is possible. You said you have a new clutch so that slipping almost can be ruled out. I say almost because things just don't add up.

Alvin

This is a very clear indication that you need a steeper gear. A low (numerically) gear ratio will make it real picky on launch.. Put a little higher gear (numerically again) and the car will be much easier and much more consistant to launch. This happend to two of personal cars.. a 93 LT1 and a 00 Z28. . They would get to the point where you spun or bogged.. Thru in the next up gearset and the 93 picked up a solid .3 in the 60'. the Z28 picked up a solid .2


BTW.. are you using the MT Drag radials? they are freaking awesome.. I have two local customers pulling 1.50's and 1.48's with them in 17'. Both are nitrous cars.

Alvin

Thats another clue.. Sounds like you have too much clutch, too much tire, not enough torque.. So get it back with a little more gear.

88BlackZ-51

Josh I was in the exact same situation as you last time at the track. I am pushing around the 345rwtq as well. One would think that is plenty of torque of the line. I either spun my tires up, or bogged them out. It's not easy, Keep trying. I wouldnt say the tires were a waste! Give it time!


Now the 13.5@107 with the NOS is mind boggling. I am running 13.7@101 as you know. I thought foresure 12's. Hmm.....

creoleman

What's your rear-end gear ratio? Just wondering,as I didn't see it mentioned.

neat

I don't have the cash to swap out the 3:45's that are in my car now, but I do eventually plan to go to the 4.09 gear set. That will kill my L98 at the big end of the track, but I have a converted LT1 intake in the garage waiting to be installed.

The McLeod twin is way over the top for my power level, but there really are no other options for a drag strip abused C4. Of all the decent clutch set-ups out there, the twin is the only one that you can slip some to ease the hit. The other single disk set-ups all seemed to be kind of digital, or very on/off in nature. I'm not very good at slipping the McLeod, but I can tell it's possible when I try to do it.

Yes, those are the tires I am using. I know it's possible to cut those kind of 60 foot times, but I can't seem to get under 1.9 to save my life. Are those cars you mentioned running automatics? I can spin the ET radials at least for the first 15-20 feet if I leave on the bottle, and the car is making less than 500 RWTQ.

I'm going to go back to the track this coming Sunday. Maybe I'll unhook the swaybar, lower the pressure to 16 PSI, and heat **** out of the tires one time and see what happens.

ANTI VENOM

You say that you only do a short burn out. Are you using your brake at all? I can use my left foot on the brake right after I pop the clutch, or I can heal-toe it and sit there all day. That might help with your high rpm launch traction. I do agree that some numerically higher gears will make it much easier to get a consistant launch too.

neat

I am going to get some more practice in for sure. The track is open all year round down here.

I don't know about mind boggling, but it is odd. This was my first time out with the bottle and the tires, hopefully my ET's start to come around as I get some more practice. It would be nice to race on a day that wasn't 85+ degrees with 90% humidity too.

ANTI VENOM

There has to be more in it, my l98 ran 12.8's with street tires and NOS. The best part is that practicing is fun.

neat

Yeah, I haven't tried heating them at all. Just a short 1 or 2 spin to clean them off. With some heat, and the swaybar disconnected hopefully the car will hook better on the nitrous.

On my 92 Corvette, I picked up .7 just by going to a slick VS a street tire. While I didn't expect that kind of gain on this car, I was thinking .3 was in the bag, no problem. Then almost a full second from the 100 shot of nitrous (it's not NOS, NOS is brand name, lol) should of put me in the high 12's pretty easy.

Oh well, back to the track for me. You're right, the practice is fun!

MTVette

Neat,

After racing my 92 A4 for over 4 seasons on street tires, I just put on a pair of MT ET street radials. They made a big difference. Not so much on 60' times, but mainly on consistency. My best 60' time ever on the street tires was 1.79, and I had only a few runs under 1.8 sec. My 60' times were quite inconsistent, with lots of runs over 2.0.

Change to July 1: I've now had three days at the track with the MT ET's. My best 60' is now 1.76, but nearly all of them are below 1.82. In competition, I had 4 runs that were within .04 seconds of my dial-in. In short, it is impossible to have consistent quarter mile times without having consistent 60' times. To get those, you need much more traction than the car actually needs, so that even the most aggressive launches generate no wheelspin, just better times. YMMV

Mike

nelson84

Boy that is strange l98 ran 12.8 with same mods as LT1s

500hp

I agree with Alvin...MORE rear gear. Somewhere between 3.73 and 4.10, depending on where (what RPM) you feel the power is dropping off and what gear (and RPM) you are in at the finish line.
We all know the 6 speed cars are a handful to launch whenever you increase power and/or traction. 1.8-1.9 is certainly not 'sucking' for a combo like yours.

JD'S WHITE 93

Nobody here is talking about an LT1 the 91 in question is a L98 car.

Alvin

If I was you I would think about putting your street tires back on.. I really feel that you can have too much tire in situations like this..

Case and point..

My girlfriends car was pulling solid 1.8's and a few high 1.77's on a 17 inch BFG. We took those off and used a 16 MT DR and the car was alot harder for her to drive and she couldn't break out of the 1.9's. We rented the track out for a whole sunday so she (and a few other people) could practice all they want without being too crowded.

steve40th

Another thing to remember is oour Vettes are IRS and the tires top will tilt inward creating allot of camber, so your tires dont hook like a solid axle.
Jeb talked of getting a proper alignment and it looks like its 1-2 degrees positive camber and zero toe to get a good launch and lower your 60 foot times.

kopbet89c4

I know I could cut nice 1.8 60 foot times on my 275/40R17 Nittos, but I am running some schitty Falken tires for the sake of my D36. 2.2-2.4 60s are good enough for now since I'm not hardcore drag racing. Oh yeah, my Falkens are 255s, no wonder my ETs still suck for the new found hp I now have...

Maybe I'll race on them once, but then just that one time could be the last time for the D36.

This baby is my DD and when the dough starts coming in, I might get the fatter D44.