Here is the data log for my last run on Aug 27, Sunday.
30 inch ladderbar at 120 ,,% anti rise, 10.5 x 33 Hoosiers, 4.56 rear, 2.45 low TF trans. Car weight after run with driver, 2905 on BIR scale.
I am looking for input on shock settings,etc. The high rpm in low gear, up against the rev limiter for .4 seconds must have been caused by a too narrow throttle stop setting I use to limit the shifts. I use it to only provide a ground for a certain window so it never gets to shift a third time

Is that a RPM flair on the 2-3 shift?

I don't see any shock data there so you'll have to explain the different lines. What I assume is the RPM line shows you in the rev limiter on the 1-2 shift and then shows some sort of RPM flare on the 2-3 shift. Not sure if there is wheel spin on the driveshaft or if that is a transmission slipping problem.

Yes, I will call Chuck and ask about that

Andy, top line is engine rpm, the other blue line is driveshaft rpm, red is fuel pressure from constant flow methanol injection
Downward sloping is acceleration in G force.

I don't see much wheelspin, so my uneducated guess is the acceleration spikes are partly from a short wheel stand? The delayed 1/2 shift, which hit the rev limiter, is I believe due to a setting in my deadenbear cc1. Maybe a lockout affecting the rpm switch that fires the air shifter?

A good thing to do is blow up the DS RPM scale a LOT more. Then look at it in the time period of converter flash (say from 0 to 1 second). You'll be able to see wheel speed vs. g force really well there.

You can see the g-force spiked and then dipped slightly about 0.2 seconds. I can see a slight move in the DS RPM at that time too, but blowing it up will help see what happened.

If you overlay the wheel speed... you MIGHT see the wheel speed go up while the g-force goes down. That would indicate spin.

If the DS RPM didn't rise, but the g-force dropped, it was dead hooked, slight carb bog, etc...


There is no doubt there are gains to be made from that RPM limit hit. You can see the g-force dropped like a rock and went nuts in that area while it was on the limiter. Not sure what it's worth in ET, but there is some for sure.

Converter is WAY to tight, just curiius what the drive shaft RPM is at .5 into the run?

I agree that the converter is too tight since you are dropping well over 1000 rpm on the shift. Talk to a converter mfg and show them the graph and see what they say. They'll most likely want to loosen things up so you're only dropping a few hundred rpm on the shift.

You shift at 7600 or 8000? And trap at 7600?

I’ve never run up on the converter that much….. is that a big tire thing? Forgive me for loading your question post with more questions

Assuming that you're asking me about the spread between shift point and recovery? I'm not a converter expert by any means but based on what I see on the cars I tune the mfgs have been narrowing the RPM drop down to something in the 500 to 600 rpm range. The explanation is that they are trying to keep the engine near peak power all the way down the track. In the old days the rule of thumb was to drop the RPM from power peak back to torque peak but now it seems to be to loosen up the converter so the RPM stays almost flat going down the track. I've seen some data logs where the engine RPM is very flat. That is typically with a glide rather than a three speed.

I don't know the answer on this car which is why I suggested he talk to a converter mfg. I'm pretty sure they'll tell him that looser will be faster.

If I’m reading the graph correctly........looks like the DS is at about 1000rpm at .5 into the run.

0

Would just further confirm the converter is WAY to tight

Yep......

thanks guys. I assume a looser converter would actually mean a softer initial hit, as in the first five feet or so? Then is up in the higher part of the power and making the car faster overall?

The 1/2 shift was delayed due to a wrong setting. 7600 will be about where I want to set it.
And all questions welcome hear that shed light on making a car faster.

all questions are good. I may return to 15x33 tires

I like the idea of going back to the 15/33 tire and looser converter. As Al Aguirre has stated in the past. Loose is fast, facts.

Also, Greg have you ever considered a 2.28 1st gear?

I was actually wondering about what appears to be the 2000’ish two step rpm launching from with a 6300 stall. Our converters have similar stalls, I’d just always left at a much higher rpm.

I think RPM is the other line. Looks to me like the RPM is at 1500 then he takes it up to 4000 just before launch.