Velocity stacks from Schnitz racing: are they worth the cash? Any noticeable performance gain?
I'm setting the bike up for dragracing next year - Full system, PCIII, 30 shot of N20. Would these be a good addition to my setup - and I am assuming these need to be on there before I get it mapped - right?
Thanks
Good question -
As
nobody has sorted the STACK questions on this forum....
There are:
1.
Stock Suzuki type stacks, you can use:
2 stock Suzuki "shorter" and 2 "longer" Suzuki stacks = that's how she runs...
or use....
4 stock Busa 48mm ID (inner diameter) "short" stacks = lose about 2 in low and mid and gain about 2 HP on top.
4 stock Busa 48mm "long" Suzuki stacks = gain about 2-4 at low and mid and lose about 2 HP on top and the power drops off a bit at redline.
2. There's some
"other" brand billet stacks that flow more than stock "on a flowbench" and are 50mm ID and have a huge "elliptical" inlet radius... with references to an article called "Best Bell" by Gordon Blair (who I do talk to)
In about I'd call a "60mm" length, they make roughly the same power as the stock set of 2 short and 2 long Suzuki rubber stacks. Schnitz sells them and so do a few other places.
When people say that "aftermarket stacks don't make any difference", this is what they are talking about.
3. Then there's the Factory Pro "60mm" billet stacks.
They boost up the lowend power somewhat and make the part throttle response better.
Upper midrange is significantly boosted - I usually see 4 to 8 HP boost at one rpm or another (keep in mind that 4 to 8 True HP is a 2.5% to 5% increase - so it's not too extreme of an improvement!)
If the bike is dyno tested under load (advanced methodology over 4th gear wack), you'd commonly see an equal to stock or very slightly higher than stock peak HP number.
Generally, the HP would about equal stock hp at around the bike's tach redline - and at the rev limiter, I'd expect about a 1-3 HP loss.
So -
No loss lowend, probably a slight hp gain
Def. better midrange
Def. def. better upper midrange
Equal to or slightly better peak hp
less hp at the rev limiter
Of course, any "potential" stack HP improvement can be destroyed by improperly directed testing and tuning - and that's why you sometimes see on this forum the results of that, like that dyno chart from a shop in San Diego.
I couldn't ever duplicate their results unless I didn't tune properly.
NOW....... as far as "power at the rev limiter".......
Factory Pro DOES make their quickchange billet stacks in lengths from "15mm" to "80mm" in 5-10mm steps .
If you were focused on not losing HP at the rev limiter
(anybody ever tell anybody else that the rest of the engine's tuning doesn't really want to run strong at the rev limit??? :-)
With 35's or 45's or similar, you CAN make power at the rev limit - BUT!!! you'll lose the big upper midrange gains - all in an effort to not lose power at the rev limit.
So - if you are driving your Busa around and shifting at the rev limit all the time, use the short Suzuki stacks or order the Factory Pro ones with a 35mm-45mm length - BUT - you'll get very little power improvement in the low and mid with the 45's and you'll actually lose a slight amount of lowend with the "short" Suzuki stacks.
And "equal length" FP stackset is still better than equal length "4 short Suzuki stacks", because the intake air velocity is much better with the FP stacks -
Of course, any "potential" stack HP improvement can be missed by improperly directed testing and tuning - and that's why you sometimes see on this forum, the results of that, like that dyno chart from a San Diego shop.
I couldn't ever duplicate their results unless I didn't tune properly. As I've said, properly tuned, 4 "short" Suzuki stacks are only trading about +2 on top with about -2 in the midrange.
But I've only been tuning for 35 years........ so... waddue-eye-no??
So -
Assuming that the bike is tuned to Best Power at all throttle positions for each of the stacks:
The FP Superflare stacks will give you more usable power for most riding, without the NOS.
The "other billet stacks" will give you very little gain in day to day driving and 4 short Suzuki stacks will lose a couple hp of low and mid, and gain 2ish on top.
<wink!>
Marc
ps: Schnitz is one of our larger Superflare dealers and has both the other brand and the Factory Prop Superflares - do a search for "Factory Pro Hayabusa stacks" as their site (as of 10/07) isn't linked right on the Hayabusa parts - Thanks - M
