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Discussion Starter #1
Hello all,
Just installed bully dog gauges on A pillar which reveled what seems to be low boost.
65mph, 2000 rpm, 550 EGT pre turbo, and 2 psi boost. 6psi max boost.
Tested vacuum at pump 23" and at turbo 13".
Tried a run with waste gate wire tied closed and could only get up to 7psi boost at WOT.
ALso been getting code 36 intermit. when engine is very cold in the morning. She starts but runs rough with large cloud of white smoke. IP replaced @ 90k now have 198K
What do you guys think? It seems from my limited experience that the IP is going and that is the reason for the code 36 and the smokey start up.
Why do you think the low boost values? Turbo going or could it be the old cat blocking up the works.
What should I check next or am I getting the most boost alowed by ECM?
All in all she runs strong but doesn't have the guts I want.
I am considering going the the home made turbo master route with 10k pot boost fooler.
Help need more power. I think the next trick will be new exhaust. Who carries one for the 2 door Yukon?
 

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before i modded my truck the most boost i could get was 7-8 psi, i use autometer gauges and the boost fiting is just behing the turbo to intake sleeve. i first used a boost fooler to gain it to 12 psi but now its chipped and i dont need to run the fooler, dont know about the exhaust for the yukon, i got mine from walt at ssdiesel, id go stainless if you can afford it, i woulda got it but they didnt offer it before i bought mine
 

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my truck is still pretty much stock except for a 3" exhaust (which will become a 4" once i mod my truck some more) with the cat gone. i normally get about 4 psi cruisin at 70 mph. i get boost spikes of about 12 psi, but it comes back down to around 7 or 8 psi. if i take off slower and get on the throttle gradually, the most i get is around 7 psi. i have my vacuum hose for my gauge in the boost sensor location, just got a tee and rigged it up
 

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The boost figures you give seem within the normal range for a stock 6.5 The turbo will give low boost at cruising rpm, typically 1-2 psi. Max stock boost is around 5-7 psi to maintain reliability. The turbo is capable of producing 15 psi (nominally).

I haven't seen a blocked cat yet, but it could happen. Opening up your exhaust with a 4" cat back system will help quite a bit, as well as adding a 3"downpipe.

Your smokey start-up may just be a bad glow plug. Check all of them first, before looking at the IP.

The boost foolers do work. The increased air flow will actually decrease your EGT, to a point. Too much boost on the stock motor can be a bad thing.

Jake
 

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i have my vacuum hose for my gauge in the boost sensor location, just got a tee and rigged it up
maybe it's just me but i thought doing it that way was a bad way. something about barometric pressure or something having an effect on wastegate solenoid. i set my gauge up by drilling and tapping a new hole altogether for that reason. i also did a home made tm and when i did the 1st run it hit 16 lbs real quick. since lowered it to run 10 lbs max. and holds at 3-4 on a flat highway. i'll have to adjust it for varying engine loads. ie. camper and or boat. also got 4 inch exhaust.
 

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Discussion Starter #6
i guess it could be boost guage

Lots of good info here.
I tapped my intake for the boost guage on the side nearest the driver on the fuel filter side could this be the reason for the lower numbers I'm getting. I also have a 50 psi guage. I realised too late that this was the wrong scale. I think a 0 to 25 psi gauge would be better for this application.
The thing I couldn't understand was that whith the waste gate wired closed it would not develope more than 7 psi boost. I figured that with the waste gate held closed I would get at least 15 psi boost at WOT.
Any thoughts?
I included pictures of my boost gauge tap location and my EGT gauge tap location. The EGT was done with the engine running. Drilling the hole was easy but had to use a ratchet exension on the tap. No room to work.
Its been to cold outside to paint the guage pod. Not sure I will paint it I like the contrast of the black on grey.
 

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A "Turbo Master" is the way to go for maintaining the boost. Being an "S" engine along with OBD I computer controls is easy to upgrade with a good ECM chip.
This chip will allow more boost, more fuel at WOT and contol transmission line pressure when called for. For anyone who hasn't upgraded the exhaust system yet crawl under the truck and look at the turbo down pipe. Every pipe from the factory will look like yours, some might be worse.
Part of this upgrade MUST include a new mandral bent down pipe. The Tahoes are challenging to work on, everyone else is easier. When I did mine I dropped 100* on the pyro and picked up 2lbs of boost.
 

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Discussion Starter #8
Which exhaust kit did you use?

Charlie,
WHich exhaust kit did you go with with your tahoe and is yours a 2 door or a 4 door? I have a 2 door and am not sure if this makes a difference when ordering the exhaust kit.
 

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I have the exact same truck as yours except it's a Chevy. My exhaust system was from John Kennedy. Unfortuneately GM never put the 6.5TD in a four door except on the Subs.
 

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most of the kits will make/send you the kit for your truck/suv that you have. eBay prob be your best bet, they will send you what you need!
 

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exhaust just purchased

I just purchased a 4" aluminized with a 3" downpipe and the X-over from Warpspeedperformance.com. With shipping was under 400 bucks. Haven't received it yet.

teamjnz


Charlie,
WHich exhaust kit did you go with with your tahoe and is yours a 2 door or a 4 door? I have a 2 door and am not sure if this makes a difference when ordering the exhaust kit.
 

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Looking at your pics, plug in EGR actuator alone doesnt stop flow/power loss, only way to stop it is to blank off under the valve itself, or better yet is freeze plug in center of lower intake. But at you own peril there "off road mod only" tampering with emissions stuff can carry stiff penaltys.

Boost is in normal range for stock program, what gears you running (check RPO codes in FAQ & glovebox), more fuel = more boost, also need to know what IAT is you may be limiting fuel from high IAT since you are bypassing ability for PCM to control boost, any codes???.

What is lift pump pressure when "getting on it" low lift pressure <1 psi will hold you back.

Lastly a silver gasket between upper & lower intake on S trucks, this is a 1 time use gasket, if leaking by will rob you of ability to make max power. PMD is in a bad spot get it off the intake and onto a longer harness so it can be mounted in grille area for max airflow
 

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Discussion Starter #13
Thanx turbine doc.

Turbine doc,
THere is a thin aluminum plate under the EGR that blocks it off for off road use only.
I have had the upper intake plenum off about six times using the same gasket. I will get a new one and replace it soon.
I hear you with the PMD as well. I will relocate it soon.
I have 3.73 gearing.
I am not presently using the boost master or the boost fooler yet. THink its a bad Idea. Should I go with a chip?
How about my vacuum readings: 23psi at the vacuum pump and 12 at the turbo at idle? Seems a bit low.
I am getting a code 36 at cold temps which goes away when the truck warms up. Could this be a failing IP?

Regards
 
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