Some test and tune results with my 850DP

Not a bad night considering the 3000FT DA and 95% humidity. First two runs had 80%pump/20%av gas mix on the fuel. First run with 82/92 jets with air 4" air filter, 13psi in the slicks and shocks set on 4 (all night), the driver screwed up and committed an over shift to neutral - 11.61 at 115.43mph with a 1.67 60ft (.471rt), next run with 83/93 jets, air filter and 13psi, 11.08 at 120.71 with a 1.58 60ft, (.552rt). Getting better. Next run 11psi, 83/95 jets, no air cleaner, 60%pump/40%av gas and a longer burn out - 10.914 @ 122.72mph with a 1.53 60ft. (.603rt) - cooled her down, right back out and is and ran 10.911 @ 122.88mph with a 1.56 60ft and a .507 reaction time on the foot brake....What a time to waste such a good light....LOL.....Probably have to mess with the jetting some more on a better air day but she can stay in S/Pro at a 3000ft DA with 95% humidity so I'm happy with that. The 850 carb worked good from the first run and it only got better as we tweeked it. More left it her yet I think.

Good deal,always a fun nite when you make progress,and load it up in 1 piece. 

I say that every time we leave for the track, all I want is to have it drive itself back on to the trailer at the end of the day... 

Nice to see things working out for you.  As you tune that thing, you may want to think about changing one thing at a time. That way you'll know which changes helped...and which didn't. If you make 3 or 4 changes to the car and it picks up...which one or ones caused the improvement? Carry on and have a blast.

The last two runs had the same jetting, shock setting and tire psi. The only change was removing the air cleaner to try it out without one. I have a 4" K/N filter on there with a metal top, I should get a breathable top too.

Just last week I made two passes back to back...one with the cotton gauze air filter with breathable top, next pass with no filter. I saw no real difference. I'll keep the filter on mine. I think scoop size/style and airpan combo will determine if you run better with or without filter. Be sure to let us know how that turns out.

I prefer a filter myself considering what it costs to make horsepower. I just took it off so I could hear " I told you so" by two buddy's who race....LOL...my sponsor said he might be at the track tomorrow and he said he would bring down a breathable top for me to try

Good luck!  

very cool keep us updated  

Same everything as the last two runs Friday night, just went 10.98 at 121.95 with a 3000ft DA.

I ended up taking out a 8.90 rail in round one, I had a .558 light, 10.96 on a 10.90 dial and he beat me to the stripe by .008 but he went 8.958 on an 8.96 dial. He won the 8.90 PRO-TREE series race yesterday. Round two I went red (.485) but I figured I might as well see what she will do and I had my hands full...There was an oil down about 6 cars before me. Here is the video link to those two rounds. I'm happy with how the 850 performed in the 3400FT DA and 95% humidity so the 750 is for sale...LOL..

https://www.youtube.com/watch?v=cCOgf7ADM8s

https://www.youtube.com/watch?v=nv929XeZF4E

think the 850 improved you should try 1050

The air was so bad it was hard to see the gains but I doubt the car would have run 10.90's with the 750 as we had barely stayed under 10.99 with a 2300ft DA last race with much less humidity and we had a DA over 3000ft all day with 90% or higher humidity.

did you try that air filter deal?

No, he showed up and forgot to bring it, next race it will have one. 

Should have made another good pass on the 82/92 jets, so you woould have a better comparison, but sounds like it running pretty good. I assume the back power valve blocked off?

It still has the 83/95 with a PV block in the back. Decent jetting for all the weather conditions we see here. I was talking with a well known builder and racer here yesterday. He dyno'd my engine, he suggested I take some rear gear out. I ordered some 3.89's yesterday to try it at the next race. I'm running. 1000rpm over my peak HP at the stripe. Peaked at 5600, trapping at 6600.

BigRigTech wrote:It still has the 83/95 with a PV block in the back. Decent jetting for all the weather conditions we see here. I was talking with a well known builder and racer here yesterday. He dyno'd my engine, he suggested I take some rear gear out. I ordered some 3.89's yesterday to try it at the next race. I'm running. 1000rpm over my peak HP at the stripe. Peaked at 5600, trapping at 6600.

Wow. What gear are you running now? Sounds like you should pick up quite a bit with the gear change. It is amazing how fast these BBF's go at so little RPM, gotta love'm. The only reason I asked about the PV, is I was trying to see how far from stock you had to go to be right. 80/80 with two PV's is stock ,in a #4781 850, so you did not have to fatten up too much. Have you ever tried it with the jetting more square, say 88/90, just as a test? Are you still running the 50cc pump on the back?

Just reading the plugs and so far this has been good. The air is getting much better here now so it might need to be fattened up more. I'll know in about 3 weeks. I don't want to constantly mess with jets, it's easier to change the dial on the window.

That is very true about the dial in change. I am waiting for the gear change resuilts, that will be interesting.

I just took 70lbs out of the car and I'm hooking up a two step now to leave off the brake pedal at WOT. It has a switch on the shifter too do the lower rev limiter only works in first gear so I can pile the brakes on at the stripe with no worries.