Run Chart Analysis

[jspell]

Are the driveshaft (blue line) spikes at end of run wheel hop?

[dreracecar]

wouldnt you have matching spikes in RPM??? my first thought would be trans/ converter slipage

[JrFuel Hayden]

when i have those bumps in the driveshaft curve, it's track bumps.

[wideopen231]

Looks like local track that's rough as crap on top end.Agree its track bumps

[jspell]

Thanks guys...

[coupemerc]

Yes, I would say bumps in the track too. When the rear of the car moves up and down going over the bumps, the drive shaft rpm changes as the rolling radius of the tire changes. The engine rpm does not "spike" because the tires are not leaving the ground. Some of that resolution will depend on your data rate too. Is that Maple Grove?

[ricardo1967]

Yes, I would say bumps in the track too. When the rear of the car moves up and down going over the bumps, the drive shaft rpm changes as the rolling radius of the tire changes. The engine rpm does not "spike" because the tires are not leaving the ground. Some of that resolution will depend on your data rate too. Is that Maple Grove?

This and being a fluid coupling, the torque converter absorbs spikes like that.

[dreracecar]

bumps start 3.5 sec in to 5 sec at peak, was this 1/8 mile???

[JrFuel Hayden]

OK J you got me looking at your RPM Data chart, and at 1'st I thought your tires might be too big and they pulled the engine down below good HP range because the RPM curve took about 1 1/2 seconds to gain RPM on your 6 second 1/8 mile run.  But then because I don't look at any thottle stop, delay box data curves I thought you may be running a "Stop-n-Go" Super Comp style FED.
It looks like you might be at 4000 rpm launch, and your converter is stalling at 7050 or 7100 rpm, and shifting about 7800. Going thru the 1/8 about 7700.
So is that what you are doing ?  If you are not running a "stop-n-go" bracket car, you may want to take a look at your 1'st 1 1/2 to 2 second performance.
Our 7.0 JF car has the engine reving up to close to stall at the hit, where we get 1.00 to 1.04 sixty foot times on 31x12" tires.
I'll try to post one of my Race Pak runs.

Jon

[JrFuel Hayden]

Here is one of our last runs 2017 Heritage jrfuel in Sacramento.
7.03 1.04 sixty foot, 186mph, 1/8 is 4.46 @ 155mph, with all iron 400ci SBC injected pure alky, with 7" A-1 converter, 12" rims, 31x12x15 GY, 4.88 gear, and 1.68 first gear PG.
Jon

[JrFuel Hayden]

Glenn, HELP

[32bantam]

Click on the bottom left picture name....it will open in new window that should allow you to rotate for viewing.
I have a question......at the very beginning....the wheel speed spikes...explanation?
Thanks

[dreracecar]

Maybe the graph is from when you took the car to Austraila 

[GlennLever]

Here is one of our last runs 2017 Heritage jrfuel in Sacramento.
7.03 1.04 sixty foot, 186mph, 1/8 is 4.46 @ 155mph, with all iron 400ci SBC injected pure alky, with 7" A-1 converter, 12" rims, 31x12x15 GY, 4.88 gear, and 1.68 first gear PG.
Jon

Is that better?

Just for the grinds of it here is one from GoodGuys

Red is engine RPM, Green is drive shaft, Blue is g force, yes I am spinning on the launch

[JrFuel Hayden]

Glenn, try raising the tire pressure, it may give you more bite. Or a looser converter, it will hit the tires softer.
Jon