Okay, as noted in my last post the car does need sorting (as most any newly constructed car may). Areas such as engine tune, converter stall speed, rear axle gearing, etc, need to be adjusted in order to make it go quicker and faster down the track. Based on the runs made at this outing, we have deduced the following:
- The engine tune remains rich as hell on the methanol fuel. Before the last pass seen in these videos, we literally increased the fuel return jet size by a whopping 15 numbers, and still there is absolutely no heat in the plugs. And so the engine remains in a detuned state for injected alcohol (we are not concerned, we intend to dial in a nitro tune).
- The stall convertor speed is about 5500 rpm with the current engine power. 5500 rpm is way too high as the car cannot take advantage of the 533 stroker's flat torque curve which starts about 2500 rpm lower than the rpm at whch the car hooks up and goes. Therefore we are installing a brand new converter with different stall characteristics.
- The TH400 transmission is not shifting correctly. It jumps from 1st gear to 3rd gear. The reason for skipping 2nd gear has been pin-pointed to the shift gate. Fortunately, this is a simple fix and not a tranny problem.
- The 4.11 rear axle ratio is too low in conjuction with the 5500 rpm stall speed. The rear gear will be swapped out to a 3.54 final ratio. Given the light weight of the car, the torque that this engine produces, and the trans now giving us 2nd gear, we feel this is a step in the right direction.
Below are two videos from the last License Pass of the day. As most of you know, 6 passes minimum are required for general licensing, and the last two required passes are to be full-length passes. Both of the videos posted below are of the final License Pass which is 8.67 @ 151 mph. One view is from the burnout box, and the other view is from about 3/4-track.
As you watch these videos, you will notice that the engine "flat lines" down the track, meaning there is no rpm increase as the car accelerates. That is mostly due to the high stall converter. The changes we are making to the car (bulleted above in this post) should correct this. Also, in the top video ("View from Launch"), you can even see Van gesture entusiastically for the car's expected shift to 3rd gear--which doesn't occur because the car is already
in 3rd gear (shifted from 1st straight to 3rd).
I would think that all the changes should get us closer to the 8.00's, but this assumes we tune the engine. Frankly we have no intention of dialing in an alcohol tune since going that direction is pointless as we intend to run nitromethane.
In the mean time, here's the first day of full License Passes down the track at Famoso:
Last Pass, View From Launch:
Last Pass, View From 3/4 Track:
We plan to return to Famoso on Jul 12 & 13 for the next "Saturday Night Nitro" event. And assuming the car's driveline is better sorted, we intend to start dialing in a nitro tune for the engine. I think that the plan is to step in at about 40%. We need to break 7.50 in the quarter in order to be properly licensed for the classes in which we intend to run the car.