Ok guys, I have an old adjustable boost controller I used to use on my stealth before I upgraded to AEM and electronic controlled boost. I am thinking about installing it, I am wondering is there a certain boost level I will throw a code at? or is it different for each truck. I have seen some guys don't throw codes some do, wondering is this is just a toss of the dice. I will get a boost fooler if I need it, but wanted to try a few things first.

What is the max safe boost a 03 turbo should be exposed to. 30psi?? Dont have a flow chart on the stock turbo so not sure.

2nd question is about exhaust, in a recent article I read that a duramax picked up over 100 lbs of torque in the 1800 ish range, by going with a 4 inch cat back. I was wondering if anyone has ever seen that kind of power increase going from 3.5 to 4 inch on our truck.

I guess my question is, does upgrading the exhaust on a 03 make a big difference in the mid range. Hp is not my thing, usable torque is I want lots of it and I want it in the 1800-2200 range.

Thanks guys, everyone knows the 03 guys are the coolest

 

Im hitting just below 40 with an adjustable boost elbow on the stock turbo and not throwing a code. No boost fooler needed.

The main reason I got a larger exhaust was egt's. Im sure it freed up some hp, but the cooling effect was what I was after.

 

Is it possible to "make " your own boost elbow? It looks very simple

 

Yup! ^ I made one with a 90 degree 1/8th inch NPT and a 1/4" hose barb. Drilled and tapped the fitting for a 5/16" allen head set screw and bingo! I coulnd't find a fitting that was all one piece however, so I bought a 90 degree union and the hose bark was separate. I had to put the union in the turbo first and the screw the hose barb in though, because with it all assembled it was too long to screw in. No biggie though! Took all of about 15 minutes to make and install. Cost was free. I had all the parts at work. (uhuhmm) Shouldn't cost more than 3 bucks at most hardware stores. Maybe more if you have to buy drill bits and tap, but I already had them. Wish I had been thinking and I would have taken pictures for a writeup!

 

So is it critical where the hole goes for the allen screw. Are you trying to close the hole completely?

 

That is the goal, yes. To block of the wastegate. You can just unhook the hose, but this way it is adjustable. I used the hole in the fitting to center it. I found a drill bit that was very snug in that hole, and drilled it that way. Then turned it around and drilled it for the tap size and tapped it from the opposite end.

 

My overboost code hits at ~32psi so I got a Quad BF. I've read the stock turbo isn't good past ~24psi. After that it's mostly superheated/expanded air instead of more/denser air. The stock muffler is terrible - it's choked down to 3" down inside and I could hear mine hissing when towing. I now have 4" from the downpipe, back. After the muffler and turbo change my egt was down to ~1000. Pred 100 gets it to ~1200 and Extreme gets it to ~1350. The 3.5" DP doesn't seem to be a problem with those egts. Craig

 

Craig- do you still have the 3.5" downpipe? I was interested in making a total 4" system. I know I need the newer downpipe and elbow off of the turbo to do that. Just curious if your temps are with the 3.5" or 4"? Also....what muffler did you ise?

 

was that 24 psi or 34 psi for the limit on boost?? I can belive 34 would be max, I was thinking 30-32 would be the limit for me.

 

I top out 37psi with the smarty, but 35psi is about the max efficiency level. 24psi is about what a stock turbo puts out alone.

 

Those egts are with the 3.5" DP. I have the stuff to build 4" but I don't expect much improvement for my hp so that isn't high priority. I have the 4"id x 51" Nelsen. The experts say if you go more than ~24psi with an elbow, blocked WG or whatever, it's not really productive. They say it's just overheated/super expanded air and it's time for a bigger turbo. Craig

 

Strange I have read a few places that say 32 psi is good on the 03 hmm. Wish I had a flow map, would love to see where the happy zone is.

 

Pretty much anything above 32-35 psi on the '03-04 turbo produces nothing but more heat which will decrease the life of the turbo.

MikeyB

 

I just bought a "boost elbow" from the local diesel shop here, basically my stock elbow was a 90* peice with the center bored wide open. This new elbow is 90* also but the center hole in much much smaller, smaller hole means more boost correct? Right now if I run my BDTD on Extreme I can't see past 22-24psi. Will this elbow realy make a difference? Now correct me if im wrong but more boost means more power right? Hypotheticaly(sp) if I now see 30-32psi will I gain any HP from that?

I just hope I don't see a CEL for overboost, a while back I was running Extreme and went to pass a car and I don't exactly recall what boost I hit but a overboost code was thrown. Hopefully i'll find out tommorow, i'm waiting for a new rubber coupler from AFE I was dumb and ripped mine when pulling it off the turbo flange.

Will running a elbow like this kill the longjevity of the turbo?

 

I push 32 with the quad. Don't really see the ned to go more on the stock turbo