The O.D. on the turbo is 2.5 inch, which makes custom projects pretty easy as this is the standard size for turbo applications on foriegn sport cars and there is a good amount of plumbing available. I have built a custom upper intake as a foundation for an intercooler setup.
I used 3" ID on the one I have made so far. 3" will fit right over the stock pieces (turbo outlet, intake snorkel).
I've noticed a direct relationship between the turbo whine and removal of factory restrictions. An intercooler is the ooposite of a restriction, it's an expansion chamber coupled with surface area for heat transfer. The turbo must compress a greater volume of air to make the same psi in the intake Plus, it's a longer intake now which means turbo lag. I can see how all this could be heard as whine.
I have plans for making a water to air intercooler for under $100 in parts. I want to show step by step on the build to help other people who might want ideas for their own.
There is something of a restriction built into the exhaust-side turbo housing that is sapposed to dampen the turbo whine (baffle). If you like turbo whine, as I do, remove it.Edited by: quantum mechanic
Yes on the IC install, turbo whine diminished from stock, disagree on turbo lag , or if it's there can't tell by seat of pants test, but I also have boost control maybe that's the difference. with round filter and air box top off you can hear turbo spool up thought about installing a microphone & speaker to hear it all the time, inside the cab.
Tim, I run with the cover off the air box as well. I use the large Wix air filter and the cover would not fit so off went the cover. It sounds nice like a big rig. It is also a consistant tenth of a second off the 1/4 mile time in a 95 degree humid night.
Quantum Have you you removed this restriction? If so is it in the discharge portion? What am I looking for. I have rebuilt many holset turbos, and have not seen any type of noise muffler incorperated. I am a cummins tech, and have not had the oppertunity to tear into a 6.5 turbo.
Go to my IC install link above you can see where I removed the turbo muffler and plugged with a freeze plug, also another trick on the hose coming from the CDR to the turbo small flex line from "tuna can' in valve cover rtv the hose joint it can let dirt to the turbo/engine.
The CDR is required to maintain proper scavenging air thru the crankcase.
The turbine housing has no "baffle" to quieten whine. The exhaust system does the rest.
When the turbo sings, it's the hi-rpm intake and compression you're hearing.
The '96-up has a plastic resonator chamber, or "muffler", attached to the compressor intake inlet elbow for 'passenger considerations', as TurbineDoc states.
The '95 GM-5 turbo was modified for improved compressor and turbine efficiency - the exhaust elbow was radically different than the early '92 - '94 turbos, allowing more exhaust flow with less back-pressure.
The '97-up GM-8 had minor upgrade in the wastegate shaft bushing due to early failure in the GM-5's.
To hear them sing, open up the intake shrouding.
But, remember, the engine likes cool, dense air. Open up the air box, and the compressor pulls in engine bay temp air at 200 to 800 degrees.
The 800deg comes from exhaust gas temperature, just inside the exhaust manifolds and turbine housing. Cast-iron mass retains and radiates heat. Heat rises.
Based on measurments I took when I installed the thing see my site located in above thread 25" x 4.5" x 7" closest core I see at their site is pn 2-175 rated for 615 Hp & 920 cfm, I don't think I'm encroaching on flow restriction problem with the IC which is why I worked so hard to fit the bigger IC in a 1/2 T truck.
gmctd, my 93 has the GM-4 turbo. Which of the GM lineup will bolt on without issues? As you stated, the other turbos are significantly more efficient? I'm running a boost controller and like the adjustability, but the turbo has about 180,000 miles on it and wouldnt like it to blow on me at 18lbs boost!
To the left is the rotating assembly, wastegate/exhaust turbine housing middle and the transition for the downpipe right. The rotating assembly wears its' bearings out occasionaly, but if you catch it in time, you can replace them for about $75. Let it eat the shaft and it's $250.
I can see where I need to grind these edges down to a smother transition.
Has anyone tried to powerflow (ExtrudeHone) the exhaust turbine housing in an attempt to increase flow? Would this be similar to clipping the turbine wheels? In other words, gaining flow in the upper range while sacrificing response down low?
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