I'm going thru this now too. I just had Big Boyz street ported heads put on my 95" with andrews 26 cams that were previoulsy installed. Big Boyz did the install and new tune. My dyno numbers were down about 5 ft lbs., hp was about the same compared to the original dynojet tune, but my bike runs much smoother and shifts easier. My seat of the pants tells me it is about the same or maybe a little more torque. We were shooting for 9.6:1 cr but he said it ended up closer to 9.8:1. The 26's like to be at 9.6:1. Would 9.8:1 hurt performance?

 

9.8 should help pump up the torque.
Scott

 

Thanks Scott.

 

Your welcome.
Scott

 

So Scott what is your take on factory pro dyno vs dyno jet for accurate hp torq #s? You are saying that my #s are way down and my butt dyno agrees. Just curious if there is that much difference between the two dynos. Maybe the factory pro reads too low? Would a DJ 250i read close to the same as a factory pro? Or maybe particular dynos to stay away from if you want accurate measurements? I do realize that the guy running the dyno has to do it the right way to get real measurements and after all. Isn't that what we're all after, real measurements. Just trying to educate myself a little.

 

When you use a 4 degree advance key you move the whole range ahead and if you have a free flowing exhaust you may be going backwards on the exhaust side while slightly helping the low end torque by sacrificing top end power. We did a 107" build with the stage 3 R&R cnc ported heads with the 54 cam with 1.725 intake rocker arms and on Bob Thoma's dyno got 125/125 torque and horse with 10.6 to 1 compression.

 

Folks are happy with their tunes,(BB's) but the side/side comparision is something I do not know the answer to.
Yes indeed, dyno's are all about fact finding.
Scott