ITB and adj runner lengths

crzyone · Post by **crzyone** » Wed Jan 30, 2008 5:29 pm

Might be better off installing a 2004+ VVT N* and using the cams to achieve your goals. Would be wicked to have VVT and variable ITBs, but it would cost a couple grand in dyno tuning.

Series8217 · Post by **Series8217** » Wed Jan 30, 2008 5:57 pm

whipped wrote: I forget the kind of dyno, I think it's a mustang, but one of them lets you set the load speed. Imagine being able to hold the RPM @ 3000 and varying the intake runner length for the best torque. Hold it at 3500, etc etc.... Now I don't think they'll let you stand behind a car on a dyno (nor would you want to) so some kind of automatic dial-a-matic deal would be necessary.

I had my car dynoed on a dynapack. They let me stand behind it (though it was pretty loud). They can vary the load to make runs long or even keep it at one RPM under a lot of load so you can work on tuning certain RPMs under WOT without having to do repeated runs past that RPM. The shop here only charges $100/hr for use of the dyno. You should be able to find something similar locally..

In other news, I finally scored the last set of ITB to 2-bolt flange adapters I needed for my ITB setup. I'll start a build thread sometime in the next few months. These are going on my 3.4 DOHC.

Aaron · Post by **Aaron** » Wed Jan 30, 2008 6:08 pm

Pyrthian wrote:
nfswift wrote:Hahah, as cool as a VGI would be imagine those Yamaha style ITBs adapted to a V6... it would be like the new air grabber/shaker hood, they "pop up" when you get on the gas :love10: I'd rock that...

yes - BUT - they actually go DOWN as the RPM's shoot up

On the R6 the trumpets go up at a certain RPM. Between the trumpet and the new end of the runner is now a gap, about 1-2", for the new trumpet to breathe from. When the RPM's go down, the long runner lowers back onto the short runner. Look at the animated pic linked above.

This also really demonstrates how weight conscious the sportbikes are today. If it doesn't absolutely have to be aluminum, it's plastic.

Series8217 · Post by **Series8217** » Wed Jan 30, 2008 6:19 pm

It's just a clever way of doing a dual runner length intake then. So all those trumpets are in a big box with a filter to the outside?

Fastback86 · Post by **Fastback86** » Wed Jan 30, 2008 7:23 pm

Series8217 wrote:It's just a clever way of doing a dual runner length intake then. So all those trumpets are in a big box with a filter to the outside?

Exactly.

nfswift · Post by **nfswift** » Wed Jan 30, 2008 7:39 pm

Aaron wrote:
Pyrthian wrote: yes - BUT - they actually go DOWN as the RPM's shoot up
On the R6 the trumpets go up at a certain RPM. Between the trumpet and the new end of the runner is now a gap, about 1-2", for the new trumpet to breathe from. When the RPM's go down, the long runner lowers back onto the short runner. Look at the animated pic linked above.

As Aaron pointed out, they do not go down for high RPMS, they lift off at high RPMs as intake tract tuning functions as follows:
Longer tract length reduces the RPM of peak torque, while shorter tract length raises RPM of peak torque.

Pyrthian · Post by **Pyrthian** » Thu Jan 31, 2008 9:32 am

Aaron wrote:
Pyrthian wrote:
nfswift wrote:Hahah, as cool as a VGI would be imagine those Yamaha style ITBs adapted to a V6... it would be like the new air grabber/shaker hood, they "pop up" when you get on the gas :love10: I'd rock that...

yes - BUT - they actually go DOWN as the RPM's shoot up
On the R6 the trumpets go up at a certain RPM. Between the trumpet and the new end of the runner is now a gap, about 1-2", for the new trumpet to breathe from. When the RPM's go down, the long runner lowers back onto the short runner. Look at the animated pic linked above.

This also really demonstrates how weight conscious the sportbikes are today. If it doesn't absolutely have to be aluminum, it's plastic.

right - I see - you want shorter for higher RPM - and, to go shorter - they seperate - yup

Pyrthian · Post by **Pyrthian** » Thu Jan 31, 2008 9:41 am

crzyone wrote:Well, I understand why would would want a variable length trumpet but its just not needed.

With a good exhaust, cams and ITBs you are looking to make 400+hp and 330+ torque. Why does a fiero need any more power down low to begin with? 1st gear is going to be traction limited and everything after that is going to be in the power band anyways.

Why not make a good set of trumpets that are tuned for upper rpm power and leave it at that.

I agree you will need a variety of trumpet lengths for tuning purposes to see how much power they make but a variable length trumpet would be hell to tune.

yes, we were discussing a fully variable system, not a this/that system. which is tuned to the RPM the engine is currently operating at, for maximum power at all RPMs.

throw in some variable valve timing

maybe just make the whole intake out of "balloons" of specific design, which inflate as the RPM's drop. all the way to the valve bowl.

because thats the one thing about most variable intake designs - once in the heads - your back to full spaciouisness, tuned to high RPMs. a bladder you insert could in fact go into the heads also, to keep the velocity all the way to the valve.