Boost/Drive Pressure numbers with 74+mm turbo's

Charles · Jun 2, 2011

It's too bad you live so far away...

I would love to help fab up a compound setup on a truck that everything else actually functions on as opposed to my junk.

You and Brian both could really get some sh*t going on with a good compound setup. I have no idea what my drive pressure is right now, but I used to run ~70:80 before and had no problem controlling boost, but now with the gate at 100% on the 38R and the 55 only making ~25lbs I'm at 80 on the manifold. The drive has no option but to be dramatically low for that to be happening. Well, that and the fact that I picked up an honest 80 to 90rwhp from basically reducing drive.

I love that GT55 turbine.

Marty · Jun 2, 2011

Your not toooo far away lol.....

CSIPSD · Jun 2, 2011

Marty... Might throw on a Isspro EV2 Exhaust Back Pressure gauge...

Electric T'ed into the factory EBP Sensor location, in 4 years I have had to replace one sensor (about 140,000 miles)...

a_moore · Jun 2, 2011

Charles said:
It's too bad you live so far away...

I would love to help fab up a compound setup on a truck that everything else actually functions on as opposed to my junk.

You and Brian both could really get some sh*t going on with a good compound setup. I have no idea what my drive pressure is right now, but I used to run ~70:80 before and had no problem controlling boost, but now with the gate at 100% on the 38R and the 55 only making ~25lbs I'm at 80 on the manifold. The drive has no option but to be dramatically low for that to be happening. Well, that and the fact that I picked up an honest 80 to 90rwhp from basically reducing drive.

I love that GT55 turbine.

I have been tripping to say that for two years.....BIG TURBINE = LOWER BP = LOWER PARASITIC LOSS = more happy power.

I am suprised that the reduction of bp on second stage turbine was that noticable. I thought you needed to start on the first stage.....seems to be working nicely......38r/GT55 FTW!

I still want to try GT45/GT55 as an all out comp only setup.....like Marty's or Brian's, a little pulling, then a little racing....a lot of fun.

a_moore · Jun 2, 2011

Marty said:
Yup. I went ahead and took it to 55 in the newest 4500 tune. Pedal didn't do anything but put the fire out. Enough smoke to cover 4 lanes at wot.

I went through Maryland again yesterday and did not have time to stop. I will make time on the next trip in July, I want a ride now after hearing all these details...

Charles · Jun 3, 2011

a_moore said:
I have been tripping to say that for two years.....BIG TURBINE = LOWER BP = LOWER PARASITIC LOSS = more happy power.

I am suprised that the reduction of bp on second stage turbine was that noticable. I thought you needed to start on the first stage.....seems to be working nicely......38r/GT55 FTW!

I still want to try GT45/GT55 as an all out comp only setup.....like Marty's or Brian's, a little pulling, then a little racing....a lot of fun.

It used to make no sense to me that opening up the gate around the 38R and letting the 47 work harder produced worse boost:drive ratios. I thought maybe all the devious plumbing angles I was forced to use in routing that gate was causing a lot of drag or something. Even though I still didn't quite buy it. I never dreamed that 88mm charger with a 1.32 turbine housing would have been the problem. But after talking to some guys in the gasser world I realized the turbine in the 47 becomes a bottleneck in big displacement applications. And with a second stage charger pumping up the dispalcement, that's exactly what was happening, which is why I decided to up the first stage and leave the 38R with the gate alone.

In fact, If you look at it by the numbers, I picked up exactly 89.5rwhp, best gain at 3000rpm. Which is obvioiusly crap, because it should have picked up a bunch on the top, but with the crap my truck is pulling lately it just can't make anything up top, yet that big ass charger still picked up right at 90 wheel at 3000 rpm, where it was barely loafing. And that was starting at a dismally low 538.49rwhp, and pulling it all the way up to 628.

In terms of percentage gain, that represents 16.6%. Assuming I had swapped to the 55 back when my truck still worked, and I pulled 644 on the 47 with the 300% nozzles, that same gain would have put me at 751rwhp.

Point being..... something like this 55 under the hood of a truck that actually works... would make some hellacious power for a Heui 7.3 on fuel. These 400's, by the numbers should make 689 on fuel on my old setup, when my truck used to work, and Brian proved it by pulling 687 IIRC on dunbars running them. You slap that 55 on that, and you might be looking at 803rwhp on fuel.... again, by the numbers.

Needless to say, it's killing me to have to see such potential being squandered by some bs problem that keeps plaguing my truck, and I would love to see some of you guys running similar setups on some of these engines that actually function properly in all other areas.

Dieselboy. · Jun 9, 2011

What and where are you guys getting BP gauges ?

Dieselfever · Jun 9, 2011

0-200 psi liquid filled tattle tail gauge from the local Hydraulic shop. Doesn't have to be 200psi, 0-100 would probably work best really if you can find it.

-Michael

Big Bore · Jun 9, 2011

Dieselfever said:
0-200 psi liquid filled tattle tail gauge from the local Hydraulic shop. Doesn't have to be 200psi, 0-100 would probably work best really if you can find it.

-Michael

Can you use the EBPV tube port in the passenger manifold to take a reading? My tube has been gone and manifold capped for a long time now.

Dieselfever · Jun 9, 2011

Yes, that is where mine are. 1/4" npt to 1/4" compression fitting and 1/4" copper tube coiled up about 10 times then ran over to the gauge.

-Michael

Suns_PSD · Jun 9, 2011

I just unscrew my Pyro and use that fitting to read BPs. Your gauge needs to be on a coil of copper tubing to dissipate heat otherwise your gauge might get damaged.

Big Bore · Jun 9, 2011

Dieselfever said:
1/4" copper tube coiled up about 10 times then ran over to the gauge.

For cooling?

Dieselfever · Jun 9, 2011

Yes to dissipate heat, as Suns said also. The copper from the fitting in the manifold is discolored up until about the 2nd or 3rd coil on mine

-Michael