GT750 Powered Race Car (D-Sports Racer)

[2steve]

Well, cool dad 
Maybe you can change the mains without throwing off the carb synch.
Hope it works noticeably better for you!

[sav0r (CL MotoTech)]

Parallel thinking? Is that the term?

We struggle with fuel economy with the car. The 5 gallon fuel cell is barely enough to finish a half hour session. I think we calculated like 7mpg. So larger jets could be a problem there.

[teazer]

On the dyno, we removed the red sox and gained a hp or so.  Then we removed the filters completely and added another 1.

So I fitted the short rounded intakes 9 Too short to call them bell mouths and added another 2 HP at the top end.

I don't think I scanned the dyno chart, so I will have to look for them to see the effect on AFR of the changes.

[sav0r (CL MotoTech)]

Well dudes, load in is tomorrow.

We actually loaded up the trailer on Monday. The car prep was done.

Since last running we replaced the copper radiators with new aluminum ones. From a material perspective, the aluminum ones should be worse, but we suspect the copper ones were full of junk.

Will it cool better? It's not clear yet. It is however obvious that we are getting a good flush on the system, no airlocks to be found. The new rads have caps whereas the old ones didn't have a means for release air at the tanks.


The water pump developed the classic trans oil drip. We pulled it down and installed a new mechanical seal and new shaft seal.

To run the car lower we added some extra fender cooling. I.e. the wheels were rubbing inside the top of the fenders. We removed that material and added louvers to cover the holes. This should let us get to the 40mm ride height I want to see with the car.

Otherwise, we fattened up the needle jet and hope for better mid range response.

No other changes were made.

I got the RD350 back out and it will be at the track too. I haven't ridden it much in at least a year and it was a little shabby. I ultrasonic dipped the carbs and added fresh fuel and it fired right up. The brakes felt good. The lithium ion battery was sitting at 14v no issues. It stopped dripping trans fluid, so it's probably low.

Tomorrow is load in, have to do all the bullshit with the bureaucrats, then we will ride the car down to the visitors center in the parade. I will get some video to post.

[teazer]

How did the car run with the new head design?

[sav0r (CL MotoTech)]

I'd say the head was a success for sure. We ended up one fatter on the needle jet, but on the leanest position with the needle. The power is what you'd expect while on the pipe but I found we were with more mid range. I was able to run a gear higher in the slow corners and it still pulled off corner. One session was in the wet and I felt downright comfortable in the car, and in fact, I would have been the fastest car overall by a long ways in that session if it weren't for the session getting cut short. That speaks to the reasonable drivability of the engine.

There is some electric issue that temporarily knocks out the left side cylinder spark. We rearranged wires and spark returned. Asides from our typical overheating (pretty well narrowed down to low airflow volume) and the intermittent lack of spark on the left cylinder, the engine was a monster. Even with overheating we finished our sessions this year.

I lead the race after starting fifth. A guy unfortunately tagged me and spun me. I recovered and finished 12th of 20 or so cars. Since I do not have reverse, I had to wait for corner worker powered reverse, and I fell to dead last on the circuit. So I made a decent recovery. We were good for second or third this year. I do not think we could have kept full pace due to the overheating.

We had a really nice time though. The brakes were great. Overall the car was pretty pleasant and drama free. I saw over 2g's peak lateral and sustained 1.8g. This is very good for a non aero car. The van worked great and got a ton of attention. I got a few unsolicited offers on my RD350 that I turned down.

Overall a very fun weekend!

[Simmons1]

That was a cool update. Sounds like a great weekend at the track.

[85RZwade]

Man, that first pic! Looks like a beautiful venue.