quote:

Originally posted by ski_dwn_it:

quote:

Originally posted by moparacer:
What's with the spin at about .5 on those runs. Looks like it dead hooks the tire and drives into a spin. When my car does that I am slow too. And there is a difference in trans pressure that shows up on the RPM too from what I see.

The car does that every time. It is the bias ply "getting up on the tire". They wrinkle up (first spike) and then spin about 3/4 of the turn (second hump). If you are not monitoring driveshaft or have a good video you would never catch it. Also there are two curves there overlayed if you look close. The problem does not effect the driveshaft which means the trans is not the problem. The chassis is doing the same thing - its a power issue. Hence the reason the rpms differ.

Another clue I found last night when again going thru the grid. I have an alert for a low crank sensor. But grid does not show when or how many times. I am rarely in the grid so if could be 6months old.

Right now I have a new crank sensor, and cable. Also ordered a new coil but not putting that in unless it is still acting up.

You ever try to take that out? When my car dead hooks, and doesn't do that its way quicker overall. My wheel speed looks like a nice smooth rainbow. When everything is right I can lay 2 or 3 runs over each other and they are identical.

Mines 2 oe 3 slower on 60 ft when I get that hump.

Do the slower runs typically happen when the car is warmer/more heat soaked, or when you are hot lapping it?

quote:

Originally posted by team:
Do the slower runs typically happen when the car is warmer/more heat soaked, or when you are hot lapping it?

Car is always at the same exact temp - trans, water, etc. I heat soak it first startup to 195* to ensure the water is out of the oil, drain it, and catch can stays water free the entire day. Maybe a tsp of oil.

I did change the crank trigger and cable to - grounding the cable inside the grid as that is something I did not originally do.

I also had a very good conversation with Peter Biondo over the weekend when he called to discuss various items. In the nutshell he feels the car is tripping the beams with the wheels sometimes and other times the stripe taker. His transam is built similar. Also the car is way to consistent up front and at 330 to be gaining and loosing that much ET/MPH. The only odd thing is the rpms difference otherwise I would have been looking here to start with.

I have the track getting me some measurements to verify the beams at the end. Which most are around 5.5inches. I may also rig up a camera and scale system to see where my front shocks are at the end of the strip to very stripe taker and beam measurements.

I did also rephase the rotor, which was not off much but did require a little adjustment because I used to run more launch retard. But again can not see what being the issue.

I will be at $20k event this weekend at same track as prior anomalies, so we will see.

Appreciate the suggestions and will let you know. Hopefully with big check as verification.

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Originally posted by ski_dwn_it: The only odd thing is the rpms difference .

I have the track getting me some measurements to verify the beams at the end. Which most are around 5.5inches. I may also rig up a camera and scale system to see where my front shocks are at the end of the strip to very stripe taker and beam measurements.

What’s the difference in rpm between the two graphs at 1 second into the run of this pic?

Consider just removing the stripe taker and leave the front wheels break the beams…. most consistent if front bodywork is taller than beams.

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In the nutshell he feels the car is tripping the beams with the wheels sometimes and other times the stripe taker.

I had to remove the factory air dam under my front bumper. I'd stab the brakes and be .02 under and a couple of MPH off when I know I killed at least 5.

Cost me $10K at Beech Bend.....that's my story and I'm sticking to it. Everything was rolling my way that day.

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Originally posted by Goob:
I had to remove the factory air dam under my front bumper. I'd stab the brakes and be .02 under and a couple of MPH off when I know I killed at least 5.

Cost me $10K at Beech Bend.....that's my story and I'm sticking to it. Everything was rolling my way that day.

I rip the throttle instead of using the brakes!

I have a 2nd Gen Camaro & it has approximately 31" of beak/bill. While I did have a stripe taker & used it/not used it very well. It was an added advantage when used properly or maybe it was luck.

2BKING