if your going to do a water meth kit to lower egts use just water. have you thought about a bigger exhaust? I just looked and you had a 4" which shouldnt be too bad at getting heat out. also a bigger or more efficient intercooler would work too

 

Yep...
I can show you a reason why your GT3788R surges......

If you used the included Garrett "Power Elbow" that allows you to use the 2 bolt exhaust(factory style)flange then your having drive pressure issues which is causing it.See that elbow when bolted up on the charger has a 1/8" lip that disrupts the exhaust flow along the walls of the exhaust housing as it tries to exit and then creates turbulence inside driving up the drive pressures.In my case when I had mine,it cost me a headgasket before we got it to a flow bench and found out what was wrong and fixed it.

What I ended up doing was working with my machinest and making a HX40 style flange to bolt on the back of the GT37 and then building a HX40 style downpipe as the Garrett charger and the new flange were a a tad longer thus throwing off the angles of a standard HX40 style downpipe.

Once we got the restriction fixed and the adapter made the charger would fly to 50psi where the gate was set to open on my 12v.At 50psi in the intake side I only had 57psi of drive pressure and it ran like that until I sold it a few years ago when I bought my HTT 66/71/13ss.The Garrett GT37R stage 3 was a great daily driver on my 12v once we fixed the flow in the exhaust side.It would lite instantly and plant your azz in the seat and ran strong up to almost 500hp on my truck but it would not cross that plane and was sold for what I run now.

I'll throw some photos of what I was telling you in regards to the flow issues I had.....Andy

P.S.-The first two photos show the restriction found caused due to the "Power Elbow".When you look at this photo you can clearly see the 1/8 lip the exhaust was hitting and causing the restriction.

 

That flange was the only thing that I didnt like about this turbo when I went to buy it cause it is a smaller housing that bolts right up to stock exhaust, I was curious if it was part of my problem. So are you saying my best bet would be to build an HX 40 style downpipe to bolt to it and have that 1/8" edge machined out?

 

Here in these photos you see the flange and a small shot of the downpipe we made.

Photo-013 shows a small shot of the downpipe at the exhaust housing and some of the needed angle change to make it fit due to the different length of the Garrett.

Photo's 017-018 show the flange itself that we made from the outside.It was made and then taken to the flow bench where we made sure the exhaust flow was optimized thus the reason for its shape.We started with a straight wall flange for the first one and then tried a couple of different variations of shapes to find the best flowing adapter.The finished one you see here is made and shaped to help scavenge out the exhaust gasses faster and it really flowed well on the bench.When we were done it was a smooth transition from the exhaust wheel and wastegate right to the downpipe with no disruptions at all and how well it worked was evident in how it performed.

I wish I would have never sold that charger now as I would have LOVED to put it on top of a bigger GT for a set of twins.The way it spooled when I was done with it I could only imagine the fun in a set of twins but alas I had my head buried in the wrong place and sold it.I do wish that I would have foiund the flow issue earlier as it would have saved me 1 headgasket job.

Hope this helps you out some...................Andy

 

You COULD machine out that elbow since you have driven it some and now will be able to see the restriction due to the soot pattern.That will help your problem out somewhat but you should think about having a flange made and a downpipe to convert it to HX40 style and it will end most all of your problems.........Andy

P.S.-I will see if we still have the CAD program we made to do that flange on mine.I will call my machinest Monday when I get up and see if we can make another one and a downpipe for you if you want me to.

 

Thanks alot Andy. That looks like a well done job. I think I will get me a downpipe bought and see if I can't get something built similar to what you have done there. I'm guessing thats just a regular HX40 downpipe?? If you could check on gettin a flange made for me like you did that would be great!

 

I will check Monday with him after the storm and clean-up is done here.

It is not a standard HX40 downpipe as with the extra length of the Garrett charger and then the flange it throws off the angles of the downpipe.We actaully had to cut one apart and piece it back together so we could get the proper angles and correct placement under the truck.

 

Well dont have much goin today with the weather like it is Might go see if I can come up with anything and will let ya know.

 

Well being bored last nite got the best of me and temporarily set up a hood stack The outlet on the turbo is 3 inch and so I ran a 3inch pipe right out of it, I also made the flange bigger that bolts to the turbo, I seen what you were talkin about Andy on the old flange where it only like a 2.5" diameter so I built a full 3 inch flange that bolts up to it. Runs great sounds great I love it!! Just not sure if its legal? My EGT's are the same or maybe just a little bit cooler. Will try to get some pics up. Oh and a big thanks to Mr. Rendel for all the help and support

 

HECK YES BUDDY!!! ! life was good yesterday. got your hood stack set up and my air horns. heck yes... we gotta start being bored more often!!