Shouldn't my car be quicker?

[WVracer]

Something definitely seems off. Log the car at the track one day and send it to PCM of NC and have them look it over. They have been doing my email tuning since January and we are still getting it dialed in. Also go through the car and check everything over: rockers, valvesprings, spark plugs, plug wires, etc. Another possible issue is heat soak of the MAF which also measures our IAT. My IATs will get up to 150F at idle which pulls a good bit of timing. Once the car starts pulling fresh air the temperature goes back down to about 8F above ambient but it takes a few seconds. A few seconds of high IAT, and low timing is enough to make the car slow in the 1/4

[LS1Formulation]

DA was 2458' that day, so there's definitely a tenth or two in better weather. I'm running 3.91 gears, 315/30/20 Nitto 555 R2s. My limiter is set at 7100 RPM. I also have a Rotofab CAI , so I don't think heat soak is an issue, and I typically have my hood open and the car shut off in the lanes. I'm also planning on having my car dynoed with HP tuners logs to send to PCM of NC as soon as my new diff is in the car, hopefully it will provide some insight.

[LS1Formulation]

Took my car to the track Friday, on the first pass I tried to feather the clutch out of the hole and just smoked it. It slipped badly when I shifted, so I got out of it and coasted through. Waited 3 hours to let it cool, made another pass and ran a 12.52@111 with a 1.78 60'. My clutch is definitely toast, even on that pass I could smell it after I hit the return road.

[bottletalk]

Originally Posted by acammer

So, we're missing some key information to really understand your ETs - what is the density altitude? A 12.6 at 8,000' of DA might not be that bad, at sea level it would be very suspicious. Post up your best slip, and lets dissect it a little bit. My gut reaction is that it looks pretty slow, I would expect a health cam/gear setup to gain nearly a second over what it was capable with as a bolt on car, but that can vary some.

I suspect there are some issues with your mail order tune as well. Your launch sounds suspiciously like it's probably riding the RPM vs. MPH limiter - from the factory these cars have a table that limits the RPM to 5000rpm until the vehicle is moving over 10mph. This can make launching a stick car on a good track with a good tire tricky - you need more RPM than that unless you're coming off a two-step. I have a good quick video about this on my YouTube that might apply here.



I also have a lengthy video on launch techniques for these heavy M6 cars. You might find this valuable as well.

great info here!

[sr530]

Originally Posted by LS1Formulation

Took my car to the track Friday, on the first pass I tried to feather the clutch out of the hole and just smoked it. It slipped badly when I shifted, so I got out of it and coasted through. Waited 3 hours to let it cool, made another pass and ran a 12.52@111 with a 1.78 60'. My clutch is definitely toast, even on that pass I could smell it after I hit the return road.

My Hitmaster clutch hit controller allows you to incrementally loosen up clutch engagement until you find your sweet spot. Far safer for your clutch vs occasionally blowing past the sweet spot while trying to find it with your foot.

Grant

[acammer]

Originally Posted by sr530

My Hitmaster clutch hit controller allows you to incrementally loosen up clutch engagement until you find your sweet spot. Far safer for your clutch vs occasionally blowing past the sweet spot while trying to find it with your foot.

Grant

This is why a pedal stop is so great, you consistently are right at the end of the friction zone at "full" travel.

[sr530]

Hitmaster is a positive displacement device that momentarily limits throwout bearing return travel, converting your clutch into a 2-stage unit. 1st stage of limited TOB travel allows you to consistently hit the clutch's sweet spot for launch slip without blowing past it, a timer then controls dwell time in that sweet spot before allowing the transition to the 2nd stage of full clutch clamp pressure. The clutch only slips as long as you want it to.



Far better than a pedal stop alone, and far more precise than modulating clutch engagement with your foot. Just dump the clutch and let the Hitmaster control slip rate.

Grant

[acammer]

Originally Posted by sr530

Hitmaster is a positive displacement device that momentarily limits throwout bearing return travel, converting your clutch into a 2-stage unit. 1st stage of limited TOB travel allows you to consistently hit the clutch's sweet spot for launch slip without blowing past it, a timer then controls dwell time in that sweet spot before allowing the transition to the 2nd stage of full clutch clamp pressure. The clutch only slips as long as you want it to.



Far better than a pedal stop alone, and far more precise than modulating clutch engagement with your foot. Just dump the clutch and let the Hitmaster control slip rate.

Grant

I agree, definitely a better, more automated way to do it. I'm in it for the challenge, and the enjoyment of doing something well most people struggle with.

[sr530]

Originally Posted by acammer

I agree, definitely a better, more automated way to do it. I'm in it for the challenge, and the enjoyment of doing something well most people struggle with.

Nothing wrong with that, much the same reason I make my clutch hit controllers.

Grant

[LS1Formulation]

Update: So, I definitely had a destroyed factory clutch. Probably had been going bad since before I bought the car. Pulled it out and the pressure plate and flywheel were blued, along with some of the metal actually looking smeared. I'm surprised the car even drove. So I installed a Spec 3 clutch, did a proper break in, and went back to the track last week. First pass, immediate wheel hop and broke my driver's side axle on the line. Awesome. Got towed, replaced the axle and installed BMR trailing arms and toe rods. ( Yes, I should have did those first. ) Plan on going back to the track Friday. In the meantime, I had it dynoed two days ago at a local cruise event and I think there's gotta be more in the tune. It made 450 RWHP @ 6430 RPM, and 413 torque @ 4620. I was expecting closer to 470-480 with the BTR Stage 4 cam. Next step is to get some HP Tuners logs to see where it can be adjusted. All in all, it's not bad for a mail order tune.

[joshnmn]

That's right where I would expect your numbers to be on a factory intake and heads.

[acammer]

Originally Posted by LS1Formulation

Update: So, I definitely had a destroyed factory clutch. Probably had been going bad since before I bought the car. Pulled it out and the pressure plate and flywheel were blued, along with some of the metal actually looking smeared. I'm surprised the car even drove. So I installed a Spec 3 clutch, did a proper break in, and went back to the track last week. First pass, immediate wheel hop and broke my driver's side axle on the line. Awesome. Got towed, replaced the axle and installed BMR trailing arms and toe rods. ( Yes, I should have did those first. ) Plan on going back to the track Friday. In the meantime, I had it dynoed two days ago at a local cruise event and I think there's gotta be more in the tune. It made 450 RWHP @ 6430 RPM, and 413 torque @ 4620. I was expecting closer to 470-480 with the BTR Stage 4 cam. Next step is to get some HP Tuners logs to see where it can be adjusted. All in all, it's not bad for a mail order tune.

It's amazing what the stock clutch will take. Mine looked HAMMERED after a few years of drag strip duty, but it was still performing just fine. How does the pedal effort and engagement on the spec feel compared to stock? What sort of material and construction is it? (ie. organic full face, ceramic segmented, etc).

That sucks about the axle. Drag racing stick shift IRS cars can be an expensive under-taking, they are very easy to break with abuse. The BMR parts will help, but a huge piece of managing wheelhop is controlling the movement of the rear cradle. Consider that the trailing and toe rods are both bolted to the cradle, which is still on fairly soft OEM rubber bushings, and you'll quickly realize that without first firmly locating the rear cradle with a poly or solid bushing that you're going to continue to have massive deflection and spring in the entire rear assembly. Truthfully, once the rear crade is positively attached to the car, the stock pieces don't seem near as bad. Differential bushings are another key place to look to in reducing wheel hop - as those are again rubber pieces in key high load areas in the driveline.

Power and torque seems about right. Dyno's are like measuring distance with a rubber band, each one stretches a little different. If you had another similarly built car that made 25whp more, then maybe I'd look a little harder for an opportunity to refine the tune or other potential limiting factor - but without other data points to compare to, you really just have a number. once you lay down some better 60' times we can get a good feel for how the trap speed is, and make some inferences about the power your making.

Sounds like progress in the right direction! I love seeing other guys out there doing the stick shift drag race thing - it's a dying art.

[LS1Formulation]

Right now, I'm at my wit's end with this car. I replaced the broken axle with a parts store special, and it blew apart at the inner CV on a 1-2 shift on the street, 3 days after installing it. After talking to an axle company about upgrading it, I feel that the effort is futile. The car is lowered and I don't want to raise it back up, and offset diff bushings can only do so much. I already have a '98 Firebird Formula M6 that's getting a turbo Gen IV aluminum block 5.3 and that has a Strange S60 with a spool. I could dump the clutch at 6K and dead hook and wouldn't hurt that axle. My SS wasn't meant to be a full on drag car, just something fun to play with and take to the track occasionally. But breaking axles on the street just grabbing gears is ridiculous. Going to the track would just mean another expensive tow bill, because there's no way it wouldn't break on a prepped surface. The clutch might actually be the culprit here, because it bites hard as hell. It's a 6 puck ceramic with a sprung hub. Pedal effort isn't noticeably different than stock, and I have to really be slow releasing it to have any sort of chatter. I'd read and watched numerous reviews on the clutch and people complaining of chatter during the break in had me ready to experience it, but I had absolutely zero chatter during break in. As I said, this thing grips like crazy, every time I shift I can feel it shock the driveline. Not healthy, I'm sure, but the window of engagement on this thing is damn near non-existent. I should have went with something less aggressive, but I figured I'd get something better in case I did decide to add some power down the road. But if I can't stop breaking axles, there's no point in increasing power. Obviously, the cheap parts store axle didn't help, but I figured it would be at least as strong as OE. Apparently not. As an aside, I already have BMR diff bushings, a Eaton Truetrac, and an LPW cover, so the center section won't be a problem. Should I buy another factory axle instead of a parts store one? The axle company kinda steered me away from buying their axles (shocking, a lot of places wouldn't care, they'd just sell you whatever ), just because with how my car is set up, I'd experience too much wear in the joints and I'd have more problems. Not something I'd want to deal with after shelling out $2K.

[sr530]

Clutch engagement rate is key to getting the most power possible thru a manual drivetrain in a drag race setting without breaking parts. It also happens to be the key to being quick. Hard for some to believe, but the weakest clutch that you can get away with is also the one that will give you the best ET.

You want a clutch that barely holds after a wot shift into high gear, that same setup will also inflict the least impact after the 1/2 and 2/3 shifts. For your best launch though, clutch engagement rate needs to be even softer than what's needed after the shifts. The easiest way to consistently achieve a clutch with two different engagement rates is to add an external clutch hit controller. Lots of Drag Week type builds using my ClutchTamer and Hitmaster products to soften the hit and widen the sweet spot of diaphragm clutches with ceramic and iron discs.

Grant