Technical > Matt Shaff's Engine Shop
Run Chart Analysis
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:
--- Quote from: coupemerc on May 25, 2017, 08:05:15 AM ---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?
--- End quote ---
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
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version