Chris Cooper
Member
What ratio are you trying to achieve ?
Length of exhaust manifold
- Thread starter spincycle
- Start date
spincycle
Member
How small ya thinking for a 1/8mi with tight corners to get 14000ish rpms? Ive got a belt drive set up on the primary side with a 57/21 combination, simply because of lack of experience, i ran it this past season with 18/19 on the clutch on the jackshaft and 63 to 68 rear sprockets and never got more than right at 13000rpm (thats with a RLV L4 pipe/exhaust manifold)...sorry for the long response, lacking knowledge, needing lots of help...
Last edited:
Chris Cooper
Member
How small ya thinking for a 1/8mi with tight corners to get 14000ish rpms? Ive got a belt drive set up on the primary side with a 57/21 combination, simply because of lack of experience, i ran it this past season with 18/19 on the clutch on the jackshaft and 63 to 68 rear sprockets and never got more than right at 13000rpm (thats with a RLV L4 pipe/exhaust manifold)...sorry for the long response, lacking knowledge, needing lots of help...
Your primary ratio is 2.714, your secondary ratio is in the range of 3.5 to 3.77. Final ratio is 9.499 to 10.231 ish... I don't think ratio is the issue. I think you have enough range. If you can find an L2 or a torque pipe from Buller (I think you mentioned you have one from him), I think you'll have better results for a tight 1/8" mile.
I'm sure others will chime in and give some advice on this, but we've always started with a set-up as close as we can guess to be correct, then worked on the kart handling (tires) and then worked gear. The better the kart handles, the more gear you'll be able to pull (meaning take teeth off and still turn higher RPM). Plus, as Al has mentioned many times before (and it is true), engage just before peak torque and watch your exhaust temps.
don, if you didn't get the matching swivel header with the KBDM that could be part of your problem. if you did and still can't get the clearance then kermit will build you an angled swivel for your pipe and it will end all your issues. i have a new standard swivel for the KBDM you can try, just give me a call. pm'd my number.
spincycle
Member
Kt100 wb3a carb on gas, jackshaft has belt drive on primary, 3 disc clutch on jackshaft on secondary, got a kbdm pipe/matching exhaust manifold, flex at 9 1/2"...been running 4 cycles for about 15 years, last season was first with 2 strokes and made lots of mistakes trying to get it tuned up...
Taft Racing
Member
There's allot of math involved in lengths tuning the sonic pos wave as well as the neg wave, they all need to be considered for where you want your power.
The timing of the header for example will determine when the first neg ( low pressure) wave returns assisting the transfers.
Depending on how many diffuser cones are used timing these low pressure waves correctly for your rpm range is critical.
Using a longer or shorter flex alone changes the pos pressure wave timing as well which can through the whole design off its intended range
The timing of the header for example will determine when the first neg ( low pressure) wave returns assisting the transfers.
Depending on how many diffuser cones are used timing these low pressure waves correctly for your rpm range is critical.
Using a longer or shorter flex alone changes the pos pressure wave timing as well which can through the whole design off its intended range
alvin l nunley
Site Supporter
I'm not quite sure what you're saying. "Put a 19 driver on it"? Are you saying a smaller driver, or a larger driver, compared to what? What tooth count are we talking about for all four gears?
alvin l nunley
Site Supporter
For any given pipe, we measured from the piston to the end of the pipe. If you keep the same pipe, you can measure from the piston to the start of the first cone. What I did was first established the distance from the piston to the fin over the top of the header pipe. Add that measurement to the distance from the fin to the first cone.
It's been my experience that a change of +/– 1/4" (+ equals more low in, - equals more top end) from ideal and the pipe loses performance everywhere.
The fact that you're changing pipes and header lengths, from what I can understand, complicates the situation even more. It would be so much easier to find the proper length if you had a dyno. Track testing being the other alternative. It's really important to find the proper late, give it your best try!!
