MPI Twin Owners, Come in!

[McRat]

I got my MPI kit with tunes from Rob today. I'll be installing them tomorrow and have a stupid question. I got the GM battery tray to mount on the frame. The question is......WHERE???? There isn't much room on the inside. Does it go behind the torsionbar crossmember? Thanks in advance, John

Is it the military mount? I think it goes under the bed, passenger side front, IIRC.

 

[BLACKLBZ]

I think so. It's GM part# 15041310 if that helps. Nobody around here that I know has a set up like this, so I don't have anything to go by.

 

[JoshH]

I put mine under the front passenger's seat on the outside of the frame. Just cut that bottom tab off and drill 4 holes in the frame.

 

[McRat]

I think so. It's GM part# 15041310 if that helps. Nobody around here that I know has a set up like this, so I don't have anything to go by.

I'm wrong. It's passenger side, right below the door on the frame about 1' south of the wheelwell.

 

[SIKDMAX]

Are two batteries really necessary, at least for us californians? How are you guys extending the battery wiring?

 

[JoshH]

I put mine under the front passenger's seat on the outside of the frame. Just cut that bottom tab off and drill 4 holes in the frame.

Forgot to mention. When you mark the holes to drill, make sure you put the tray somewhere that you will be able to get nuts on the back side of the frame (the front two where I put mine are inside the boxed part of the frame, but you can get to them with a wrench) and make sure there aren't any body bracing in the way (keep in mind where the battery will be when it's in the tray).

Are two batteries really necessary, at least for us californians? How are you guys extending the battery wiring?

Two batteries aren't required. I ran without a second battery for a while this summer, but I had an issue with the hour meter resetting. Other than that is started and ran just fine. For the wiring, I cut and extended my cable, but I think on LMMs you can build a new cable to go to the firewall mounted junction block or something like that.

 

[TrentNell]

what do you guys think about relocating both batteries to the back of the bed for weight transfer , i dont know if 4wd trucks like weight to be transfered to the bed or not i know 2wd's do i would run 2 battery boxes bolted to the floor of the bed . figured i have to relocate 1 for the twins any way why not do a good setup to maximize the weight ratio of the truck , clean up the engine bay and maybe get some traction too .

 

[Kat]

Two batteries aren't required. I ran without a second battery for a while this summer, but I had an issue with the hour meter resetting. Other than that is started and ran just fine.

:doh: Looks like I owe my turner an apology When I had Wendy's 2nd battery out briefly it would do this. Sorry Pat :hug:

Sorry for the OT

 

[BLACKLBZ]

Thanks for the info everyone. I'm off to start my project!!!

 

[Idaho CTD]

Be sure to hold the tray with the battery up on the frame to make sure it clears the two cab support braces running across the cab. The other thing you need to do is make sure it is high enough for the cables to run right on top of the frame.

 

[Idaho CTD]

From what I can tell so far, a GT42mag will go well past 800rwhp all by itself on pump fuel on stock sticks, and carry you past 4500 before fading.

I'll have the PPE twins (GT4202+GT55) on the dyno next Wednesday, but it's unlikely I will try and dynorace it. Goal is to get 900+ HP from 3000-4500 with controllable EGT's. Biggest concern is to avoid overspeeding the little charger. So far, it's only 60,000rpm at 40psi boost on 2400msec, but target boost is 75psi.

The 42 is doing 60k already at 40psi total boost? What is the 55 making?

 

[McRat]

The 42 is doing 60k already at 40psi total boost? What is the 55 making?

Just have a sensor on the little one. That means it's running at about 1.7 PR and in the center island of it's map, or most efficient area.

 

[Idaho CTD]

I meant what is the 55 making for boost? If it's only 1.7PR on the 42 that's only 10-12psi. That would mean at 40psi the 55 is making about 2.2PR or roughly 17-18psi. Without wastegates that seems way off.

 

[McRat]

I'll know alot more next Wednesday when I get a chance to tune it. It feels as fast at 40psig as it did at 50+psig with the big single.

The real proof-of-concept is what the numbers are at 4500 rpm.

My main concern with twins is that I will lose the ability to make power up high, which has been my dream since I first drove the truck home from the dealer. With a single peak HP occurred at 4400rwhp, but I wanted more air up there. Lots of Dmaxes are spinning faster than 4000, but very few if any are making peak power up there.

 

[NJ_LLY]

So with a 68mm bottom charger what would I need for a top?

 

[McRat]

It depends on what you are after. Before selecting any turbocharger, you need to know your RPM and boost you are looking for.

 

[racinmike77]

Just have a sensor on the little one. That means it's running at about 1.7 PR and in the center island of it's map, or most efficient area.

A GT42 with a larger A/R might help you out if you have one.

 

[BIG DIPPER]

A GT42 with a larger A/R might help you out if you have one.

What?

 

[Turbo Buick 6]

A GT42 with a larger A/R might help you out if you have one.

Not really. A larger aspect ratio would be useful if he were starting to run it off the map.

 

[McRat]

Right now, information about A/R's on the PPE twin kits is not advertised.

They are building high flow riser pipes, high flow Y-bridges, stronger intercoolers, and some other goodies unique to PPE twins.

After collecting enough data from Casper, adjustments might be made to the chargers, but it looks very promising as is. It spools on staging easy, something that is sometimes missing in big twins.