Second gear goes to 129 actual, with a 13,100 rev limit
At Heartland Park, on the short "back straight" (after turn 7), I was pulling little powerwheelies down a long section of it, just for fun. I'm not a wheelie guy at all, but I was pulling the front up about 6 inches.... accelerating....
At about 10k, in 2nd gear, anything past maybe 60% throttle brings the front up, just rolling into the throttle (this is coming off a corner that is a bit of a sweeper). The front just comes up, and if you slowly roll into it more it keeps it up. I think i kept the front up for a good 200 feet on a few occasions, basically 100 to 130 mph, and still not even hitting full throttle
The bike just has "dial a wheelie" power. 3rd gear, which goes to 147 actual (13.1 rev), is reaaaaallly dicey to hit full throttle and keep the front down. I think I pulled it off a few times, but still 3rd gear is "a gear to be respected". Basically 3rd gear, even with the tall gearing, is a "wheelie / wheelspin gear"
And thats with the LONG stacks
With the OEM short stacks in, fuck me...... i couldn't believe the difference. I expected to lose some low end, kill a little midrange, and add top end rev's (with the long stacks, it revved out early.... a little below 12K peak.... the power didn't fall off after that, it just stayed flat... but it made me feel like i should be short shifting)
But.... with those short stacks.... I didn't feel like it lost power ANYWHERE. The slow corners (40 to 50 mph), it was the same feeling - anything above 1/2 throttle was wheelspin / wheelie. But above that, esp above 9k, the bike just completely FUCKED OFF
I really have to dyno the bike with the short & long stacks, back to back, to see what the dyno says. The old "butt dyno" isn't that accurate. maybe I DID lose some midrange, put a hole in the powerband, and then had a spike afterwards - and that will always seem like a big increase in power... the "butt dyno" seems to be good at sensing transitions in power...
But the bike just seemed to LOVE those short stacks. Seemed like a way bigger gain than I expected. BUT.... I will say that I did some measurements before I put the short stacks in. The effective stack height went from 50mm to about 15mm (these are the short stacks that barely intrude into the airbox). OK, that will make a difference, but.... you have to remember that while the velocity stack length was 70% shorter than the earlier amount, the velocity stacks are just part of the intake tract, and if the intake tract (from entry of the Vstack to the back of the intake valve) was say 8 inches (200mm), a 35mm difference in vstacks would be a 15% difference give or take in overall intake tract length. Which should definitely move the power band around some (biasing towards top, away from low end)
But.... The one thing that I saw when I measured the Vstacks, which really caught my attention wasn't the LENGTH... it was the INSIDE DIAMETER. The FP stacks were 50mm inside, while the OEM shorts were 54mm.
Oh, my, now THERE we have something. 8% bigger ID = 16% bigger area. All else being equal of course (which it never is). That bigger ID just might equal a higher % of flow increase as well, because you will have some "boundary layer" effects at the surface... ie, there is probably a 1 or 2mm section around the edge that doesn't flow much because the air is effectively "stuck" to the walls. Now, with a decreasing taper to the bore (above 1.5 degrees, inclusive), the boundary layer should probably get washed away by the high speed air as it narrows down through the taper... but this stuff is already way over my head, and I dont have the tools / knowledge to be able to predict / understand that.
Either way though, before I put the short stacks in, that big increase in ID & therefore intake area told me that it was -possible- that the short stacks could show a huge pickup in power. IE, the long FP stacks with their small inside diameter could, maybe, be somewhat choking off the flow..... So going to the short stacks would not only change WHERE the power occurred (ie, moving the power side to side on a dyno chart, but could also change the overall AREA / HEIGHT of the power)
And that might be right, because the bike just seemed to EXPLODE with the short stacks.
It seemed like the power "moved up a gear". IE, the bike started spinning the tire & pulling wheelies iin one gear taller at the same rpm, same throttle position, with same tires
Seemed like with the short stacks, the bike wanted to aggressively spin the tire and wheelie in 4th gear... and that goes to 167 actual!!
If Big Foxie is a dragon, then those short stacks woke up that dragon... and that dragon was pissed!!
Honestly, I'm gonna go back to the long stacks, for a while at least. The short stack power was just too much for me. And that takes a LOT for me to admit!!
PS. Tim Radley sort of predicted this. He told me he thought the FP long stacks would make the bike "not want to rev worth a shit".... and might not even give me any more midrange.... He told me to put the short stacks in, i'd make more power everywhere
Oh yeah, I'm still very impressed with Tim's headwork. Maybe more impressed than ever. If I had to guess.... I'd say that I bet .... 60% of the power gain that I got is from his headwork, esp ifyou talk about part throttle power. The other 40% is from the bore increase (to 1070) and cams....
So, I'm DEFINITELY a believer in Tim's headwork. I highly recommend it!! in all honesty, I bet I could have done his headwork, the 1070 kit, and kept stock cams (but retiming those cams of course), and been VERY happy with the power
One last thing, the HP figures I discussed before, were with 91 octane pump gas, stock air filter, a big, brand new 530 chain...... Think what this sucker would make with oxygenated race gas, a race only filter, a worn out lightweight chain, etc............hahahaha