Jetting, Sprint Vs. Long Track?

Curtis Bosarge · Joined: 18 Jul 2001 Posts: 28 Location: Des Allemands, La.

We're running our first long track (1.7 mi.)tomorrow and I would like to know if / how I should adjust the jetting? Maybe a little more main jet? I'm told the main straight is 1900' long. The kart has been jetted to run autocross. We run almost flat-out for ~20 seconds. Plug color is nice and toasty (BR9EV).

TIA,

Curtis

Chris Wehrheim · Posted: Sun Sep 23, 2001 2:58 am Post subject: Jetting, Sprint Vs. Long Track?

Obviously the air quality will make a difference, but first I would run at least a 10 or 10.5 plug, otherwise chances are you will stick it. Second, to play it safe, start rich on the main, then work down from there.

Charlie Tackett · Posted: Sun Sep 23, 2001 1:26 pm Post subject: Jetting, Sprint Vs. Long Track?

I here this all the time...rchen it up for the long tracks! Truthfully, I hope people do just that. Better for us!

Whether it is S. Bend or Road America, I jet the engine according to what the RAD gauge indicates it should have. The engine doesn't know or care where it is running, it just wants the right about of fuel when that plug fires. The thing some may have to watch on a long track is not the richness of their main jet, but the adequacy of their fuel supply set-up.

Bill Kassy · Posted: Mon Sep 24, 2001 7:28 am Post subject: Jetting, Sprint Vs. Long Track?

quote:
Originally posted by Charlie Tackett:
. The engine doesn't know or care where it is running, it just wants the right about of fuel when that plug fires. The thing some may have to watch on a long track is not the richness of their main jet, but the adequacy of their fuel supply set-up.

Charlie,
I concur 100%. We found that on the long tracks vs the sprint tracks that we end up a little leaner on top but a little fatter with the off throttle needle. Nothing like stickin' a motor when it first comes off the r's at the end of the straight.

Saro Marcarian · Posted: Mon Sep 24, 2001 12:29 pm Post subject: Jetting, Sprint Vs. Long Track?

Maybe this idea comes from sprinters jetting too lean to begin with...

A sprinter never really is on it for a great length of time... Take this sprinter's lean-ish setup and put it on a course where you're at WOT for great lengths of time and maybe you'll see why people ask this question.

I believe the answer to be YES, if you're jetted too lean for sprint, you'd better fatten up for a long track...

-Saro

Curtis Bosarge · Joined: 18 Jul 2001 Posts: 28 Location: Des Allemands, La.

Thanks for the input. We run a little rich regardless of where we run. Two top-ends in our first 6 months of shifters will help you see the light.

Anyway, we stayed with the same jetting and followed the advice of an earlier reply on the plug, 10 Vs 9, and it didn't miss a beat all day long.

Thanks again.

Curtis Bosarge

Charlie Tackett · Posted: Tue Sep 25, 2001 4:12 am Post subject: Jetting, Sprint Vs. Long Track?

I think you're right, Saro. The margin of error is less on a long track than a sprint. What you can get away with as far as being slightly off on a sprint track can get you in trouble on a long track. But if jetted properly, it should be fine in either venue.

Also, speaking in generalities, sprint tends to be more off/on with the throttle. Many long tracks have long sweeping curves where one maybe at partial throttle for a period of time. That's were tuning with the needle is extremely important. Also at the end of some of those long long straights after sustained flatout running, when you do suddenly lift that throttle, you want to be sure their is going to be enough fuel there to keep things lubricated. Depending on how much you lift that's either the needle again or the pilot.

Charlie Tackett · Posted: Tue Sep 25, 2001 11:52 am Post subject: Jetting, Sprint Vs. Long Track?

Well, in *your* case, Frankie,....

Hey, you going to jar up some of that famous white lightening of yours and ship it out to Vegas for the GD SuperNats???

John Denman · Posted: Tue Sep 25, 2001 1:34 pm Post subject: Jetting, Sprint Vs. Long Track?

quote:
Originally posted by Charlie Tackett:
Well, in *your* case, Frankie,....

Hey, you going to jar up some of that famous white lightening of yours and ship it out to Vegas for the GD SuperNats???

Distilled in Chunder Valley no doubt.

Frankie Schaffier · Posted: Tue Sep 25, 2001 10:51 pm Post subject: Jetting, Sprint Vs. Long Track?

Hey Charlie,

Lift at the end of the straight ? I didn't know I was suppose to do that..

Charlie Tackett · Posted: Wed Sep 26, 2001 3:32 am Post subject: Jetting, Sprint Vs. Long Track?

quote:
Originally posted by John Denman:

Distilled in Chunder Valley no doubt.

...and bottled by Mason!