Fourth gear pull done today on Dynojet 250i. No tune yet (little rich on the bottom).

Build details here:

https://www.hdforums.com/forum/engin...ine-build.html

 

Nice numbers but pull should have been in 5th gear for the 1:1 ratio; that's where most tuners tune/chart WOT dyno numbers for a five speed. The numbers will come down a bit but will still be respectable numbers for a 95" motor.

 

Always read and heard that numbers go up on higher gear pull vs lower.

Both dyno operators that I have used over the years insisted that fourth gear pulls were the standard?

Anyway, I am pleased with both the numbers and the area under the torque curve.

 

You are correct; my bad, typing faster than I was thinking. Although, not true in every situation, it is generally true that fifth gear numbers will be a bit higher than fourth gear numbers. 4th gear pulls were the standard years back but in about '06 or so most tuners have changed over to 5th gear pulls. The use of 5th gear is to obtain longer sample times. Dynojet recommends, or used to recommend, the use of 4th gear to keep drum speed low and run times short to help speed up the tuning process and reduce wear and tear on the dyno. The 5th gear drum speeds are not nearly as high as those routinely seen by shops tuning import bikes. The shorter spin-up/spin-down (run) would save time but many tuners believe that a longer sample time gives more accurate tuning information and resolution. Pulls are made from the lowest RPM the bike will allow without bog, buck or stall.

In fifth gear, the input and output shafts are simply locked together, giving a 1:1 ratio and minimal power loss. 5th gear is the direct drive gear. So you will not have the mechanical power robbing disadvantage of sending power through the other shafts in the gearbox. Subsequently you are going to see higher numbers in fifth than in fourth because of that advantage.

Those are impressive numbers for a 95" motor, in fourth or fifth gear.

 

Thanks djl.

Twelve years ago, right after I installed the Edelbrock kit, the numbers were 100.6/98.5. That's with the same cams (chain-driven then), same carb, and same pipes. I'd say that a 14% increase in HP and a 10% increase in twist is a big tribute to the head work done by AMS (no porting).

How should I tune out the rich midrange? Smaller pilot jet or bigger needle or ????? Could this improve on its own as the outside temps warm up?

 

Man that's a strong 95" !...If the idle air screw is around 2 turns out, leave the pilot alone. I would start by dropping the needle down 1 slot. It will only get worse when the weather warms up.

 

Thanks jetmech. Idle screw is indeed exactly two turns out. I will heed your advice and drop the needle down one slot. I see that you broke the secret code on pipes too

 

That Crane 296(no longer available now)was always a good 'un.
Scott

 

Have to give credit to Dale Pulde who developed that cam during his time with Edelbrock. Based on the charts I have seen, it works great with smaller and bigger motors alike. Shame that Crane went belly-up and S&S (new owner) seems to have no interest in resurrecting it (maybe too much competition for their existing in-house-designed products). As I'm sure you already know, the R&R 615 is pretty similar. Same specs on the intake side with a slightly lower lift, higher duration & lobe center on the exhaust side. Perhaps even better.

 

Remember that the dyno chart is showing A/F at WOT; pilot and needle are not in play at WOT, only the main and it appears that you need to drop the main one size. If you are coming to Lozano's on 3/14 you can tune the carb then. I would leave everything as is except for the main and I would drop one size on the main before putting the bike on the dyno at Lozano's. Once the bike is on the dyno and before Mike does a WOT pull, have him check AFR at partial throttle so you will know if you need to make an adjustment there; not likely but the AFR could be lean at partial throttle and rich at WOT. So, after the first pull, you will know if you need to drop the needle and/or drop the main; make the adjustments if any are required and get back on the dyno for another run.