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6.5L Diesel Engine Discuss the 6.5 GM diesel engine & associated components. Automatic transmission questions & problems belong in the 4L80/85 - 4L60E - 6L90 Transmission Forum

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Old 11-28-2019, 11:37 AM   #1 (permalink)
mfoster442
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Boost question

Hi Everyone,

I'm running a stock setup on my 1994 K1500 6.5TD (except have the K-47).

Boost is maxing out at 7psi (from what I've read seems normal I think). But it hits 7psi then immediately drops to 5psi without any change in RPM or throttle input. Tried attaching a video but isn't appearing...will keep trying.

Is this the computer/solenoid immediately backing off the boost? Is there any way to keep it from the sudden drop? Is there a way to safely increase the boost with the stock setup?

Thanks!

__________________
1994 6.5L TD K1500
Ex Cab-short bed
Stock engine
160K or so miles
K-47
6" Lift
35" X12.5"X15" Tires

Last edited by mfoster442; 11-28-2019 at 11:39 AM.
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Old 11-28-2019, 11:56 AM   #2 (permalink)
OkDually
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Quote:
Originally Posted by mfoster442 View Post
Hi Everyone,

I'm running a stock setup on my 1994 K1500 6.5TD (except have the K-47).

Boost is maxing out at 7psi (from what I've read seems normal I think). But it hits 7psi then immediately drops to 5psi without any change in RPM or throttle input. Tried attaching a video but isn't appearing...will keep trying.

Is this the computer/solenoid immediately backing off the boost? Is there any way to keep it from the sudden drop? Is there a way to safely increase the boost with the stock setup?

Thanks!
The best way to post a video is to upload it to Youtube first then copy the video link from the address bar and post it here in the forum.
As far as boost goes it is commanded by the ECM based on load and will not be constant.

The drop is normal.

__________________
1996 K3500 6.5L,( "F" Eng #141 cast block) 5 speed manual, crewcab, dually longbed: 208,000mi.
Diamond Eye 4" Turbo Back Exhaust w/2.5" Flo-Pro Crossover
AirDog II DF165 w/ tank sock delete - XDP
TD-Max boost controller - Kennedy Diesel
OPS extension hose - Leroy Diesel
Glow Plug Harness- PT Wiring Solutions
Glowshift Maxtow EGT,Boost, Fuel gauges
Boost & Fuel Pressure Bolts - Leroy Diesel
2/0 Battery Cable Upgrade - PT Wiring Solutions
PMD w/#9 resistor and Re-Location Kit, mounted to bumper - Leroy Diesel
GM-5 Turbocharger
4.10 gear ratio
OptiLube Winter Formula


Proud member #1039 of The 3500 Dually Club


Last edited by OkDually; 11-28-2019 at 11:56 AM.
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Old 11-28-2019, 12:46 PM   #3 (permalink)
mfoster442
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Happy Thanksgiving OkDually!

Thanks...yeah, I figured it was normal. Not that it probably makes a huge difference, but would be nice if it stayed a constant 7psi rather than the sudden drop to 5psi.

Is there a safe and easy way to raise the boost with the stock setup? It's really just a want rather than need. The K-47 I put in recently made a difference, so i'm pretty happy with it all the way it is now. Just don't want to leave any performance on the table if there's something simple.

Thanks!
__________________
1994 6.5L TD K1500
Ex Cab-short bed
Stock engine
160K or so miles
K-47
6" Lift
35" X12.5"X15" Tires
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Old 11-28-2019, 12:55 PM   #4 (permalink)
Tommygunner
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What you are describing sounds pretty normal to me.
If you want more boost. The best way is with a tuned PROM chip for your truck.
You can make more boost manually with a turbo master. But you don't get the fuel to match with the stock tune. But you usually can set it to maintain around 7 PSI, without issues.
If boost is set too high. The PCM will see too much boost, de fuel the engine, and set trouble codes= Loss of power.
A good 4" exhaust system will help a lot if you are changing boost pressures or run a better performance tune.
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If Americans ever allow banks to control their currency. First by deflation then inflation. The banks will deprive the people of all property. Until their children wake up homeless.
1998 GMC K1500 WT, 6.5 TD. 80,000 miles. Auto, 3.73 gears. Remote PMD mounted on the radiator support. KOJO tune WOW! Carter HD lift pump. Feed the beast, GM8 turbo with Hurricane impeller. K&N filter. Ported, gasket matched upper intake. Leroy's braded stainless steel oil lines.
New Bosch injectors. Flow matched 2200 lbs pop
3 1/2" custom Aero turbine exhaust. Nutered Cat
2" Lift RS5000 Shocks. 285 X 17 Bridgestone AT summer tires. 12.50 x 33 x 15 Procomp MTs winter. Powertrax No slip locker in rear.

Last edited by Tommygunner; 11-28-2019 at 12:57 PM.
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Old 11-28-2019, 01:06 PM   #5 (permalink)
OkDually
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Quote:
Originally Posted by mfoster442 View Post
Happy Thanksgiving OkDually!

Thanks...yeah, I figured it was normal. Not that it probably makes a huge difference, but would be nice if it stayed a constant 7psi rather than the sudden drop to 5psi.

Is there a safe and easy way to raise the boost with the stock setup? It's really just a want rather than need. The K-47 I put in recently made a difference, so i'm pretty happy with it all the way it is now. Just don't want to leave any performance on the table if there's something simple.

Thanks!
As member Tommygunner mentions you can get a tune to enhance boost performance.
Install a manual wastegate controller for some boost performance.
Or you can install a Boost Fooler (aka 10kpot) in your stock setup like I did to enhance the boost.
__________________
1996 K3500 6.5L,( "F" Eng #141 cast block) 5 speed manual, crewcab, dually longbed: 208,000mi.
Diamond Eye 4" Turbo Back Exhaust w/2.5" Flo-Pro Crossover
AirDog II DF165 w/ tank sock delete - XDP
TD-Max boost controller - Kennedy Diesel
OPS extension hose - Leroy Diesel
Glow Plug Harness- PT Wiring Solutions
Glowshift Maxtow EGT,Boost, Fuel gauges
Boost & Fuel Pressure Bolts - Leroy Diesel
2/0 Battery Cable Upgrade - PT Wiring Solutions
PMD w/#9 resistor and Re-Location Kit, mounted to bumper - Leroy Diesel
GM-5 Turbocharger
4.10 gear ratio
OptiLube Winter Formula


Proud member #1039 of The 3500 Dually Club

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Old 11-28-2019, 01:12 PM   #6 (permalink)
OkDually
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With your lift and tire combo I would opt for a GM-8 Turbo upgrade, 4" turbo back exhaust and a Tune ( if you can still find one available).
If no tune is available then I would go for a Boost Fooler or manual wastegate controller
__________________
1996 K3500 6.5L,( "F" Eng #141 cast block) 5 speed manual, crewcab, dually longbed: 208,000mi.
Diamond Eye 4" Turbo Back Exhaust w/2.5" Flo-Pro Crossover
AirDog II DF165 w/ tank sock delete - XDP
TD-Max boost controller - Kennedy Diesel
OPS extension hose - Leroy Diesel
Glow Plug Harness- PT Wiring Solutions
Glowshift Maxtow EGT,Boost, Fuel gauges
Boost & Fuel Pressure Bolts - Leroy Diesel
2/0 Battery Cable Upgrade - PT Wiring Solutions
PMD w/#9 resistor and Re-Location Kit, mounted to bumper - Leroy Diesel
GM-5 Turbocharger
4.10 gear ratio
OptiLube Winter Formula


Proud member #1039 of The 3500 Dually Club


Last edited by OkDually; 11-28-2019 at 02:08 PM.
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Old 11-28-2019, 02:06 PM   #7 (permalink)
mfoster442
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Thanks guys. Really appreciate the input. Like I said, more of a want than need. Mine takes a chip and I did see one available from SS diesel. I kind of like the idea of the ECM controlling the turbo, and given I just had the heads replaced i'm not looking to get crazy with the boost LOL. Maybe i'll start with the 4" exhaust being as that's probably just good do to all around for a number of reasons.
__________________
1994 6.5L TD K1500
Ex Cab-short bed
Stock engine
160K or so miles
K-47
6" Lift
35" X12.5"X15" Tires
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Old 11-28-2019, 02:37 PM   #8 (permalink)
DieselPro
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You have removed the soot trap right?

Do the boost fooler and the optic bump to enhance the amount of fuel. Make sure you have fuel pressure at wide open also. The sock in the tank is notorious for cutting back fuel flow under high demand.

I prefer the stock type boost control . You can fabricate an assist spring to help it hold boost. Fooling the computer with boost fooler lets the computer think the boost is low for any given speed and gives the signal for more fuel which equals more boost

If you read this stuff anywhere on the net you probably read it here first.

Last edited by DieselPro; 11-28-2019 at 02:40 PM.
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Old 11-28-2019, 04:50 PM   #9 (permalink)
mfoster442
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All things I need to do...I have not removed my soot trap...i'll check that.

It seems to be running really well, so it's not like I think anything is clogged up...just wouldn't mind getting the reasonable max boost.

I'll do the search function to look for the boost fooler...not sure what that is.

Thanks!
__________________
1994 6.5L TD K1500
Ex Cab-short bed
Stock engine
160K or so miles
K-47
6" Lift
35" X12.5"X15" Tires
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Old 11-28-2019, 10:29 PM   #10 (permalink)
DieselPro
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Laughs and giggles > I had one truck that was low on power. Took hose off turbo to inspect fins. I revved the engine up and killed the engine. The turbo stopped turning and quickly started turning backwards with exhaust coming out. The back pressure was unbelievable. Soot trap plugged slap up!

You got a truck that's 24 years old > soot trap is shot.

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