Mountaineer

Nothing is wrong with the hrvp44. Its just a lot of money to spend for such little power increase, but then again your pretty well maxxed out on stick size there with that H.O pump. I personally would give a small shot, or throw a K31 in underneath it.

X2 , but I think he has a H.O pump on that O1

powermad

i dont know if this helps but i had the hy 35 before could those be matched with a certain pump

dieselfan

why? he's a auto, so SO for him.

Mountaineer

Good catch dieselfan. OK , so that even makes that pump swap worth ........
0 dollars and benefit almost zilch.

Diesel Doc

The bottom turbo will have alot to do with how big of sticks you plan on running. From personal experience you will need a larger primary for larger sticks. A 22cm ex housing will work for up to mach4's above that and your drive pressures get out of line. I am running a 26cm now and I have a 32cm that was on my turbo to start with. Once I retire this truck to pulling only I am planning on trying the 32 housing and a larger housing on the secondary to help get the egt's in line and let the secondary breathe a little better.

Turbodriven

Garrett now has the new GT88 unit out. Mid-frame unit that uses the GT47 comp wheel and is only 1200 bucks! Hard to beat....

Mike Holmen

The T-88 is a biggie, bring lots of fuel. If your running big sticks there is some value to the HRVP over a SO VP. There a bit more reserve volume for those WOT blasts. You might get more top even power as the SO pumps seem to defuel (can't keep-up) with the bigger sticks. My HRVP seems to idle ok, and has more fuel than my old SO. I haven't yet to put a decent run in yet or put it on the dyno it see how everything works together.

Don Wagner

I would use an S480 with no smaller than a 64/71mm secondary, why does everyone want such a large primary for their hp level?

powermad

if i was to keep the fueling i have what secondary would u prefer

powermad

if i was to keep the fueling i have what secondary would u prefer

HOHN

Not everyone, Don-- just me I'm not everyone, or even anyone .

I guess you didn't see the loooong twins thread of a few weeks back, but in it I surmised that keep the primary at a low PR was important for spoolup and power.

The 80lb/min I wanted from a GT4202 isn't available at the low PR of 2 or less-- it's off the map low and right. You have step up to an 80mm inducer size GT4508 to get a Garrett that can do 80lb/min at only PR 2.

Because we are running that primary at such a low PR, it takes a bigger size to deliver the goods.

jh

Don Wagner

I'm not necessarily picking you out of the crowd Justin, since the advent of the S480 is has for some reason become the standard option for a primary turbocharger. Borg Warner desinged both BD twin sets, one uses an S300 primary and the other a small wheel S400, wouldn't they have some experience in this area? If the primary used will support 1000hp as a single, it should be used in an application where it will support 80-90% of that number as a twin setup. My theory is; Why spin it if you don't need it?

HOHN

No doubt the BD twins are well packaged and proven.

Since you missed our long thread, I'll try to give you the Reader's Digest version from my perspective.

I think that it's best overall the bias PR balance towards the secondary, not the primary. For example, if you want a total PR of 6, you can either run a setup that is Primary at PR2 and Secondary at PR3, or you could run the Secondary at PR2, and the Primary at PR3. Both would yield a total PR of 6, if that's what you needed.

Why bias the PR workload to the secondary?
1) Less bypass on small turbine side means more enthalpy is extracted.
2) No concerns of high hotpipe pressures killing top charger flow.
3) Spoolup should be better because you have higher delta P across the small turbine.

So, I arrived at the theory that the primary should be operating at low PR to achieve these benefits. This means that a rather large primary will be needed if you want to make 600hp or so with only 15psi in the cold pipe. It means you will select the largest housing you can find for the particular primary turbo. That means drive pressures will be low and efficiency will be maximized by selecting the largest A/R possible.

Also, since a larger turbo has a map that's not just shifted to the right, but rather much broader overall, it will be far more versatile. If you want to make more power, you just go to a larger secondary turbo which will "drive" the primary harder as well as shift more workload to it.

So one primary turbo can either be a super-efficient but oversized turbo at the 500-600hp point, or it can have the wicked cranked up and support 700-800hp.

That's my latest theory anyway. Tune in tomorrow, as I may think of why I have it all wrong...

Justin

Turbodriven

Why not go with the GT4208R?? GT42 based unit and 80mm cold side. That should make the power you want and spool super fast as well.

Mike Holmen

Either turbo will work fine, its just on how hard you of top end power you want. you'll lose some drivablity with the larger turbo but the extra ponies and ball bearing should help that out.