Q about STUFFING VELOCITY STACKS

tony2ltr · Post by **tony2ltr** » Sun Jan 22, 2006 5:11 pm

Guys, I am planning on boosting through V-stacks, but The ones I have are carbon fiber, so the only place to attach them to a plate for a plenum is to sandwich the plate between where the aluminum stack flange bolts to the individual throttles, but this would leave 3.5 to 4 inch worth of the carbon fiber stack inside the plenum. Is this OK? I thought the ideal situation was to only have the tops on the stack inside the plenum. I would have more options if the stacks were aluminum or stainless, I could weld to those and it wouldn't be such an issue.
Secondly<<<I plan on shooting the secondary injectors directly down into the tops of the stacks. would I have to worry about fuel puddling in the plenum? This is MSII, first batch.
Does MSII even do secondary injection? I didn't even think about it until just now!

old-colt · Post by **old-colt** » Sun Jan 22, 2006 5:44 pm

Hi Tony,
If your stacks have a full radius they will have no problem pulling air from behind them. If they only flair out partially they would be best if the floor of the plenum was flush to there opening.
I have built both styles.
Spraying the secondaries down the throat should not be a problem since they will only be active at high airflow rates. You want to insure your design will have minimal crossflow over the top of the stacks to reduce blowing the fuel over to another cylinder. I am currently building an intake with individual water spray down each stack.

tony2ltr · Post by **tony2ltr** » Mon Jan 23, 2006 5:21 am

The stacks have half-radiused "donuts" on top, so they are not just funnels, but they dont have a full radiused "ring" on top.
I was also planning on water injectors at one point. Can you use regular fuel injectors for this? how about cold start injectors?
How does water spraying affect the fuel required for a given power level?
I have a set of 8 42lb/hour injectors I was planning on using, 4 for primary, four for secondary. If I get rid of the secondary set, and replace them with water injectors, what kind of power could I make? 300+ with a good setup on a 2 liter 4? I know the 4 42 pounders could make almost 300 Nat Asp, but how does water injection affect this?
Thanks for the reply, I have been mulling this over for months.
Tony

old-colt · Post by **old-colt** » Mon Jan 23, 2006 6:05 am

Your stacks should work fine for the way you need to build your plenum.
You may be best off changing to a set of 550s for the power level you are aiming for, they will get you into the mid to upper 300hp.
Fuel injectors for water spray are prone to be short lived since they are not really happy with either water or the alcohols in the mix. They are used in race conditions but are considered a consumable device and they do not intend them to work after sitting between events. I have heard rumors of injectors with stainless internals but have no honest knowledge of them. Maybe someone can chime in on the truth to that fact. There are also some regulators with water resistant internals out there.
I am using Misting nozzles for my setup. There are some other threads covering the affects on mixture and timing elsewhere on the forum. It is well documented of pushing boost up around 30psi on pump gas though.
Here are a few intakes I have done. Granted these are done in alloy so the build is a bit different than yours.

tony2ltr · Post by **tony2ltr** » Mon Jan 23, 2006 6:18 am

Very Cool stuff! How much space do I need between the plenum and the face of the stack? is 1" enough, or are 2+ inches necessary?

old-colt · Post by **old-colt** » Mon Jan 23, 2006 7:37 am

1 to 1 1/2 is fine when they can draw from behind. Try to get all you can though. The pic I have showing in the end of the plenum, the center stacks are under 1 1/4. That is on a Hayabusa powered car that runs 265HP at the wheels with a very broad powerband, 4200 to 11000 rpm that is.
The intake that has the flush floor is an ITB set for Mitsubishi 2 litre, it varys from 1 1/2 to 2 1/4 above the stacks, this one has the water spray in it.
And this pic with the full radius stacks are a set of Busa throttles going on a Starion, this one has about 1 1/2 above the stacks and the floor is at the seam of the stacks to there adaptors to the TBs. I am surprised I do not have a pic of this one with the plenum on it.
This one also has water spray nozzles over the stacks.
Hmm, the pic does not show, I must have exceeded a limit in posting.

tony2ltr · Post by **tony2ltr** » Mon Jan 23, 2006 10:56 am

Boy that's really cool!
Thanks for the help so far, I sent you a private message, so if you don't mind, I'd like to see some more of your work!

Tony

allen22 · Post by **allen22** » Tue Jan 24, 2006 8:52 am

Do you think there would be any problem with those stacks not being the exact same height? Wouldn't that make the runners a little longer on those cylindars?

I ask because on my 6 cylindar I don't really have room to keep the stacks far enough apart to keep them from hitting each other. So, I'd like to stagger them like you did if it won't cause a problem.

thanks
allen

old-colt · Post by **old-colt** » Tue Jan 24, 2006 9:17 am

Hi Allen,
There are a couple of ways to get around the spacing issue.
In the case of that photo the stagger was done to provide a broader power band. The original Hayabusa has a similar stagger as well as differant ignition timing between pairs of cylinders to work with this. This setup has 1&4 short and 2&3 tall.
If you download the pic from my second post with the full radius horns, those as well as the ones in the first pic have the top of the stacks ground to allow the spacing to be closed up.

allen22 · Post by **allen22** » Tue Jan 24, 2006 10:55 am

Wow, that's interesting about the different timing for the extra length horns. I guess I'll avoid staggering them then.

Unfortunately mine will be just simple flared pipe instead of actual nice radii, I'll work something out.

Thanks!
allen