Thoughts and opinions wanted on twins.
 

Posted this on another forum, but either no one really knows, or is afraid to speculate.



It all started as bench racing madness in my head, and is now turning into a reality.

I have a bone stock 93 12v as the platform. Was originally going to just be a simple man, and get a super40 and a set of 5x.014's, do the pump mods, and use a lplp.

Well I got the lplp, started sourcing other pieces......then started reading more. (damn forums)

Now I have a He351 on the way....so at first, I was like "Hey I'll just use it instead of the super40". But then, laying in bed, thinking of it all....ideas started popping in my head of twins.

Now yes, I have seen lots of guys use the 351 with s400's, and ht3b's etc.....but they have all been ppumpers. So I have dived into research about using it in a twin on the ve.....there is nothing.

Now here is where we get into the options and needed opinions. Keep in mind only the 12mm pump no 14mm here. Fuel system will be adequate to provide 15 psi all the time.

Obviously keeping and utilizing the wastegate on the 351 (be boring it to 1.1", plugging solenoid, running adj boost elbow).

First thing will be picking the bottom charger.

Options:

A - 1.28 a/r K31 (wastegated)
B - 1.32 a/r s475
C - 1.32 a/r s480
D - 1.10 a/r s475
E - 1.10 a/r s480

Now seeing as we want to be all in, said and done before say 3500 rpm, would the 1.32's be laggy? Would the 1.10's cause too much drive pressure? Would the 1.28 be about right with the option of adjustability of the wastegate?

To keep the rest of the equation simple...ish, Intercooler will be a 2nd gen unit (probably a bd/spearco unit but possible stocker for now)

Injectors will be based off westons advice for whichever chargers are picked. (most likely a 5x.018 or so) Want to keep it pretty clean through the entire range.

So for a daily driven, street/4x4 that might tow a car trailer every once in a blue moon, track 2 times a year.....which bottom would you run and why? Remember....this may go from ramblings to reality. (Truck is a getrag with a kenny's pullin parts twin disc clutch)

with what you want id recommend a p pump swap. my phatshaft turbo sucked on my ve pump and i went to the p pump and its much more driveable. the ve pumps make good power down low but when your wanting to light up big charges pretty good and get going to higher rpms i wouldnt have to say if it were me i would do the p pump swap again. it was probbaly one of the better upgrades ive done to my truck

I do understand the rationality of the p-pump swap, but there is just something about making the ve work, and doing it in a way that I havn't seen yet. If I ever wanted to strive for more power than the ve could handle, then yes p-pump is the logical choice.

I think one of these setups could make the most of the ve all the way through the ve's usable rpm range. (which is where it will spend 99% if its life)

I would do a tighter A/R on the big charger then gate it as needed. That will give you the best chance for spool up with the ability to get rid of excess drive pressure if there is any. You're not going for all out performance, so I would sacrifice some top end for better spool up and drivability. Just my thoughts.

Yeah, that was kind of my thoughts, to get power down low where the ve likes it, and where I will be spending most of my time. Thats why I tossed the k31 in there with the inbetween turbine, and it is wastegated. Or I could use the 1.10 with an external gate. Wasn't really sure where in the rpm range each housing would light....

Not only are most VE's all said and done by 3500 but they make all there power low, real low compared to a p-pump. As said above you want a real fast spooling set-up that will light down low then gate as necessary.

So are we thinking the 1.10, 1.28, and 1.32 a/r's in a t-6 is gonna be too big?

There is an option for a 75/74/1.10 or 1.25 in a t-4 footprint (still at reasonable prices), with a 4" dp, but I don't want to get too restrictive. I would think this would spool like a damn....pop in a nice 60mm gate between the turbos....hmmmm. Whatcha guys think?

After some hunting, seems some of the p-pump gus use the 1.10 t-4 as a single, and get it to light around 2800 or so with mods and tuning....so it may work well as a lower. Have to check into this more,

GT4202 with the 1.15AR wastegated turbine.

Looks like a viable option. Seems a lot of the cr and p-pump guys use it as a single. Compressor map is similar to a s472.

The turbine pitch is more aggressive than that of the 74/83mm BW, and the GT42 turbine is also clipped, good choice to be used as a primary.