I've got a 02 Raptor with a Sparks X6 with stainless head pipe, spark arrestor, Pro Design adaptor with K&N & Outerwears, 5~1 inch Uni Vents in air box lid, Dynojet 146~148, Dynojet needle 4th groove from top, air screws 3 turns out.

When the temp is in the upper 70's to upper 80's I run consistant 6.18's on 100 yard sand drags. At night when the temp drops to the 60's I start running consistant 6.30's.

.12 seconds doesn't sound like a lot but in sand drags consistant ET's win races.

So what do you think? Why am I dropping more than a tenth when the only change is tempature??

 

Jetting. You must be optimal for the warmer temps. When it cools down you are lean. But the difference must be just a fraction. Or you are slowing down as you get cold. lol So you must be a reptile?[img]i/expressions/face-icon-small-shocked.gif[/img] Hey if Scooby Doo can ride a Raptor, why not.[img]i/expressions/face-icon-small-happy.gif[/img]

 

That sounds correct since cooler air is more dense. On your next test day try taping up some of your vents when it gets cool.

 

Yes you probley need to jet up just a little more if such a slight change in temperature can make it run like that.It is doing the opposite of what it should. Ususally colder temperature equals quicker times. When my Mustang is at the track I gain/lose up to 2-3 tenths in the 1/4 from the temperture .But im talking from like 90 degrees hot to 50 degree cold difference. But mine slow's down when its hot and speeds up when its cold. What is the stock jet size for a Raptor any way? Heyone more question THEMOOSE. Do your timed runs in that 100 yard drag get your trap speed at the end of 100yards as well? If so does you mph slow down as well as the E.T when it cools down?

 

MOOSE, Thanks for all your help in the past. Here is a link that helped me understand why the power lose in cold temps, etc..

go to http://www.atvriders.net/

Click - How To
Click - Jetting Correction Factor.

Hope this helps bud!

 

The dense air will cause it to lean, but going lean should give you slightly more power instead of less.

Is everyone else's time a tick slower at night as well??

This happens at the local car drags as well, but the temprature factor is more a problem with the track surface than with the engines. They warm the engines longer and heat the tires longer, but seldom do I see guys making altercations to the engine to compensate for it.

Same applies here. If you do any tuning to get more power in the cold.....what do you do for the day time runs when it is warm??? You will be left constantly tuning your quad.

I can do a pre-race day check up, but the last thing I want to do is wrench at the track all the time. I don't drag race, so none of this probally makes sense to any of you guys. Sorry. I'll stay in the jumps and woods.

Hope you get it figured out soon MOOSE and tear 'em up at the track.

 

before the sun went down i was running 5.51, after the sun went down i couldn't run any better than 5.65 100 yds. the air temp. was round 15-20 degrees cooler after sunset. there was a significant wait between my day and night runs. i was jetted at 180-190 and was way too RICH after the temp. dropped. while it's a very short time, when your running brackets, you just gave your comp. a 1 1/2 second head start that you won't make up.

 

RichieRoadRash that makes no sense? If you were to rich when the temp went down you must have been super rich in the heat of the day. Cold air is dense (more) and requires more fuel, warm air is thin (less)and requires less fuel. The proper mix for air to fuel is about 14:1. Air can change just by getting warmer or colder, thus changing the ratio. The only way to match this change is by rejetting. So you could not have been to rich you must have been lean.

 

heck, i never said it made sense. it may have been "super" rich that day. i'm no meteorologist, but i do have race results on paper to show what i mean. my raptor was faster when it was warmer and slower when it got colder. but like knowsalot said, moose should have gotten faster. i should have as well. i know it was very rich that day, but quicker. go figure. good luck moose. may be some more E.T. racers will share their findings.

 

I'm glad to see I'm not the only one having this drop in power. I was almost afraid to post this. I thought every one would think I was crazy to worry about a tenth of a second. I guess their is a lot more index racers here than I thought.

So far I'm thinking of taping my Uni Vents up when the temp drops. It's not a big change but it's not that big of a power loss either. Mabey that will cancel out the drop off.

Thanks for all the help, Any more ideas? I'm still open for suggestions.