OK, best pass of the night was a 12.3 @115. Here's the slip:

Video:

 

gearing sounds good
clutch might be slipping on the 1-2, sounds like it but not anywhere else might slow in the left foot getting it back out. not a bad thing you want a clutch you can slip, somthing like a unspung iron disc can be a pain to get to work on limited tire.
also dont wnat to back up staggging, pull forward. dump/fast slip is not "good" for the drive train. But ding it from backing is even worse. Your slamming all the play in the parts (backlash)

what was the shock setting? loose the front up, get it to put some weight on the back tires. might be wrong not used to seeing the camera on the car, kinda changes what your looking at.
114-115 is kinda low for a full weight car 415whp, when did you dyno it last?

you have a front sway bar still?

 

Front shocks are one off full comp, full loose rebound rears are one or two off full comp, 5 or 6 off full loose on rebound. The front swaybar was still on on that pass. Probably ready to remove or unhook one of the endlinks.

The car was on the dyno 2 weeks ago, and Im hoping the mph will come up with seat time, that was maybe my 8th pass ever at the track so Im still pretty green when it comes to racing. Im thinking the clutch slip is probably me not letting the clutch in fast enough. Im curious about the not backing up while staging thing, does that allow the tires to pick up more track debris or something?

Thanks again for the advice!

 

on the back up thing, and back lash. you have lash or play in alot of parts in the driveline, its not a lot of play, but it adds up......
between the disc splins on the input shaft splines - inputshaft to the counter cluster gear lash- and back to the tail shaft (forgot that gears name?)- tail shaft splines to the slip yoke splines -Ujoints- pinion to ring gear lash- diff to axle splines...

check it out sometime. Block the front wheels, put the car in 1st gear,engine off. Jack up the back end a little get the tires off the ground. If you dont have a spool and the other tire turns, just jack up one side of the rear end, leave the other rear tire on the ground. Turn the tire back and forth till it "hit" and want to turn the crank, might be 1' or 3inchs if the parts are warn. When you dump the cluch in a forward gear after you backed up, your slamming all that play with a running start.
Just back up farther and roll forward next time, thats all dont worry about this to much. Your never gona get all the play out dumping the clutch at high rpms, all nice without a staging brake or somthing to preload the drive train. The car shouldn't roll backward at all on the track you creep up into stage and sit there. But doing it forward it still way better then from backing up.

http://en.wikipedia.org/wiki/Backlash_%28engineering%29

I watched the vid again. I donno on the car gopro is weird, try to get it form behind and the side to see the both tires, and the car. Looks like it not transferring weight, front shocks on zero extension is alot it should be super loose. looks like something in binding? but its probably just the front sway. You driving the car with it off? you know hoe loose it should be and the front end pops up. dose it feel all stiff currently?


LCA, with the car on flat ground how much angle do they have? It dosnt really matter what "hole" you have them in, thats not a setting that means anything like people talk about. that relative to the tire size and how low you have the car

 

Yeah it's got a strano 32mm hollow swaybar up front right now. I left it on because i was scared it'd be excessively loose feeling on the drive there but now that I'm used to the feel of the slicks I'll try without it. I'll have to get a pic of the lca angle as the car sits now.

 

with the car on flat ground put a angle finder on them.

or you can measure to the ground to the center of the front and rear bolt, and do some math. but I'm dumb, just google it and get the angle. I think its trig?

 

Bringing this theead back up, im gonna throw an angle finder on the lca's and see where its at. Did some reading and it looks like there may be too much angle currently. I read about -2 degrees is good? Im assuming the 0 degree reference would be along the frame rails? Im also gonna take the frot swaybar off and see how it does Im sure that was hurting weight transfer.

 

The lca's are at 5.8 degrees sloping down towards the rear end. Should I try going up a hole, assuming this would help keep the tires planted better during shifts?

 

Yes move it up a hole - that's way much anti squat imo.

 

Took an endlink off the swaybar and test drove it and the front end comes up much easier, didnt spin between shifts on the street with drs so hopefully that helps too.

 

Ok I'll try moving them up one hole and see where its at. What about the torque arm, should I experiment moving it up or down on the mount? Its onthe second hole from the bottom now, dunno what angle that is though, any ideas what works best there? I read about 2 degrees sloping down towards the front?

 

The less HP the car has the more anti squat it needs to plant the tires into the track and be consistent.

I'd shoot for 3-4 degrees at your hp level.

Having adjustable shocks where you can adjust extension and use the shock as a progressive for separation helps to slow down the separation of the suspension.

 

Ok thanks for the info Martin! Another question, why is it that cars with less hp need more anti squat? Id imagine higher hp would need more force pushing the tires down to hook?

 

A lower HP car does not hit the tires nearly as hard as a higher hp car.

The car's HP level will determine how hard the tire hits in conjunction with the anti-squat and instant center. This is why a lower hp car needs more separation to drive the tire into the track whereas a higher hp car does not.

 

So to clarify, "hitting" the tires and "shocking" the tires are two separate concepts?

 

I would have to say no. I have always referred to it as "hitting the tires" though.

Tomato

Tomotto

 

So for an example, an m6 car hits the tires harder than an a4 car. Why does an a4 car tend to hook better with less "hit". This has been a very informative thread!

 

With all else being equal aside from the difference between a M6 and a A4 yes the M6 hits the tires harder.

The problem that I see is with the M6 hitting the tires harder, the launch becomes harder to control and less consistent. I wouldn't say the A4 is any easier, it's just more consistent.

The front end is going to come up a lot quicker on a M6 car. What goes up must come down and if the weight doesn't stay transferred for a number of reasons, it's going to un load the rear tires.

The tires hitting harder on a M6 without double adjustable shocks also do what is called "basketballing" the tires. This is where when the suspension initially separates and plants allowing the shocks to extend and tire to drive into the track, the tire wants to bounce upwards because the shock doesn't have enough compression to hold it to the track when it hits the track initially. This in itself can cause the front end to unload and/or spin all by itself.

An A4 will do this also, but not nearly as bad at the same HP level and all else being equal.

There are tons of things that come into play to getting a car down the track as fast as it's capable of. It would be impossible for me to sit here and line them all out and explain them.

Hope this helps though.

 

Thanks that clarifies things much better, you are a huge asset to the community Martin!

 

just do one thing at a time, but 5.8 is alot.
I ran about that once when my car wasn't that low (tried the lowerest hole) and it would slam and unload.

If you had zero LCA angle you probally dont have a IC ( or its WAYYYY in front of the car) and the cars not gona work for you.
the swaybar should be big help, the car was not working before it was bound up.