powermad

i have a edge jammer bb turbo and wanted to do a twin set up, my question is can i wastegate a k31 and run that or do i have to get another non wastgated turbo and customize a wastegate???

HOHN

I'm under the impression that the K31 is already wastegated..

The K31 is a little small as primaries go, but it should work nicely if you are interested more in towing and low end response.

A lot of guys have used it with good results.

Wastegating on a primary is only necessary when using a smaller primary at higher pressure ratios.

My opinion is that it's generally better to run a larger primary at lower pressure, thus a wastgate would not be needed in this kind of arrangement.

But if you prefer to run a smaller primary at higher pressure, a wastegate might be a good idea to prevent the large turbo from overboosting and taking exhaust pressures up too high.

JH

Mike Holmen

I'm with Hohn, the K-31 is too small for the edge BB turbo, IMO. A S480 or BTH-3B would be a better fit and it might even be cheaper than the K-31. My K-31 has a wastegate on it and it was set at 40psi and was rated for 500hp.

Mountaineer

I havent seen one that wasn't gated. I think it would be a great setup.
I am running this turbo also and thinking about a Gt4202r for a primary.
Although a K31 would be great and half the cost.
My opinion is different. I think a smaller primary at a higher pressure would be a better setup to get that fuel/air queched a little better and be able to bring it online alot more often in a DD application.

HOHN

Well, I've beat this dead horse before, but I'll try to give the reader's digest version of my reasoning.

The irony is the earlier you try to bring in the primary, the more you delay the small charger, which has a bigger effect on spoolup.

The primary needs to be as unrestrictive as possible-- the biggest housing and so forth. This ensures that it will "get out of the way" and let the small charger freely get things rolling.

The best way to spool the big charger is get the small charger going. The irony is that going to a larger housing on the big charger might actually make for FASTER spoolup.

I know, it seems completely counterintuitive, like there's no way it could be true. But after thinking a LOT about this, and turning it inside and out on paper, I'm convinced it's the case.

But that doesn't mean I can convince anyone else, or even that I'm right.

jh

Mountaineer

Hohn, this very well might be the case. It would be nice for someone to do a right up on Primary ex. housing swaps and their effects.
I can say, and would like to hear from anyone that has had a differing experience, that when going to a larger housing on the primary seems to always result in slower spoolup. This seems to be the case with a 3B in going from a 22 to a 26 to a 32cm housing.

HOHN

I guess I'd have to define "spool" before a comparison would be meaningful.

I'm afraid I've been pretty careless with my words.

A larger housing on the primary will definitely delay the point where it makes boost against the small turbo. So if that's how you define "spool", then no doubt a larger primary housing will cause "lag".

But if you define spool as the total system response, then it's possible that the larger housing on the big turbo lets the small one breath better and response faster. (remember, this is just my theory-- no proof other than a couple anecdotal reports)

Under my theory, you wouldn't notice any improvement boost threshold-- the point where the small charger starts responding. But once you have 10psi or so, you'd see better response in the power delivery (even of boost is slower) because the engine isn't laboring as much to pump air.


My experience with my small stock charger influenced my thinking. I've noticed that the engine doesn't pull any harder at 38psi than it does at 32psi. (ignoring EGT) If anything, the engine feels "tight". If I roll into it on the hwy, the boost guage comes up really fast, but the acceleration doesn't come up nearly as fast. The turbine housing is simply too small and it causes overboosting.

But this "overboost" can be useful in transitions to help get a larger turbo going.


We had a big long thread on this a fee weeks back-- search on my name and you'll see the novels I wrote on the "bit primary" theory.

Justin

Mountaineer

Well here is the dealeo. Your " small stock charger " as you put it, isnt that bad of charger as you might think. I say this because after riding in different trucks with different turbo's and combos ,there is nothing worse than lag " to me ", in a DD truck. I would be willing to bet if you just went to a 62-65-14single your perspective would change just a bit.

* Key note : Everything in turbo selection should revolve around application.

For the most part with a few exceptions , when you go larger your going to ask yourself, What happened to the bottom end ?
For a DD truck I think I would want my primary well lit up before the speed limit.

HOHN

I agree. IMO, even a stock charger is too laggy for what I look for in a package.

My ideal would be to have a truck that *felt* like a giant non turbo engine, but revved faster like a small engine.

I like power as much as the next guy (maybe more), but I don't understand giving up 300-400 rpm of useful power for another couple of hp.

I actually like my stocker pretty well for DD driving, and it's a little laggy for what I want in that regard. That's why I favor the larger big charger to let the small turbo operate freely.

jh

powermad

so with my set up and if i add a hotrod vp44 and i little more water meth what setup would you two recommend for daily driving?

Tate

Don't waste your money on the HRVP. Been there, done that, won't ever do it again. For what you get for what you pay, its not worth it. IMO, of course.

Mountaineer

I will repeat this. In helping out your primary selection, it will help out to know exactly what you looking for,

How you use your truck,
What terrain is your truck being used in,
Mostly Interstate driving ?
Do you tow ?
plan on pulling , racing ect. ect.

Oh how I hate to beat the S400 drum, its so hard to beat for the money.
I would also not waste any money on an injection pump.

powermad

the truck is my daily driver/hot rod i am at sea level and do mostly driving through curvy roads and freeways. i have a jet ski that weighs about 2500lbs and i plan on racing when i build the tranny up more. whats wrong with the hrvp44 and what do you guys suggest for more fueling???

HOHN

I'm also kinda sick of hearing about B-W turbos. But I agree that the S400 sure is tough to beat--great value. I'd go S480 with a 1.32 housing.

Ditto on the pump.

dieselfan

just not worth the extra $$$$. you can make the same power with a SO pump like you have.

get a smarty or bigger sticks for more fuel.