Wastegate/Boost issues

[spark3542]

Background:

97 K2500 burb 6.5TD

I get code P0236 "Turbo Boost Sensor A"
I determine that vacuum pump is not working.
Since no EGR on the VIN "F" engine, vac pump is only there to supply vac to wastegate solenoid and actuator.

I fashion a homemade turbo master wastegate controller with bracket, threaded rod, and spring.

Not knowing what spring constant needs to be used, I decide to install a boost gauge.

I put in a tee on the intake plenum where the IAT sensor is (I read that this is not good for the sensor to move it out of airflow, but it's just a temporary solution). reinstall the sensor on one side of tee, and install aftermarket generic boost gauge on other side.

At idle, boost gauge reads maybe 1/2 of a PSI. goosing the throttle raises it to 1 psi or so.

I tighten the adjusting nut on my homemade turbomaster to the point where it is difficult to depress the wastegate actuator by hand (wastegate lever at full "up" position). Boost gauge reads maybe 1psi at idle. Goosing the throttle and holding at about 2500 rpm shows only minor increase in boost, reaching maybe 3psi max.

I confirm this using a different gauge directly at the tee at the plenum.

A road test under load gives same results on the gauge as goosing the throttle in Park.

I don't audibly hear the turbo spooling up significantly during any of these experiments.

My questions:

Did I do something wrong with my turbomaster install?

Is the boost, in fact, supposed to be greater than 3psi ?( I have to assume so).

Is there something wrong with my turbo?

Is there a setting for the turbomaster that will NOT throw a P0236 code? (I'm not looking to tune this beyond factory specs, just achieve factory performance without the vac pump).

Thanks

Mark in MA

[Shikaroka]

You normally won't achieve much boost with no load (in park or neutral). You can put in gear and hold the brake tight, while reving it to get a little more boost. But, you say it does the same thing while driving it?
I was surprised at how tight the spring needs to be to achieve very much boost. The pressure in the exhaust will "blow" open the wastegate if there is not enough tension to hold it open.

I would pull the air intake tube off the front of the turbo and try your tests while setting still. I wouldn't drive it like that and WATCH OUT for those blades (don't get near them)! You should be able to see if the turbo is spinning freely and that would get rid of any restrictions on the intake side.

[Dvldog8793]

Howdy
My 1999 has the turbomaster set up. Works great, I have the Heath ECM which keeps me throwing anycodes. Not sure if there is a way around a no codes situation without getting a flashed ECM or chip of some sort. I experienced the same thing when I put the turbo master on. I couldn't even get the boost gauge to move while sitting. Going down the road was a different story. I would expect that you do not have enough spring tension on the gate and it is blowing open with minimal boost. While you at it you take the vac pump completly out. If it is failed, then why have the extra drag and the possibilty of it locking up and shredding the belt.
Hope this helps...
L8r
Conley

[spark3542]

Thanks for the feedback.

I'll torque down the turbomaster and give it a more rigorous road test.

What should a good typical factory boost level be?

As far as removing the vac pump, what size belt fits with no pump?

Thanks

Mark in MA

[DennisG01]

What should a good typical factory boost level be?




8-9 psi max sustained while in 3rd gear, WOT, Converter locked, about 2500RPM.

[Dvldog8793]

Belt size depends on the year. Mine is a 1999, don't know right off the top but I can find out. If your compuker is throwing a hard code then it is also possible that it is running in limp mode....with factory boost control the highest PSI I ever saw was 8PSI.
L8r
Conley

The belt that I use is a Goodyear Gatorback No. 4060995 6PK2525 I think this means it is a 4ply 6groove 995mm serpbelt.

[big61fourby]

I would guess you might need a different spring. How did you pick the one you're using now? SWAG?

You have plumbed the boost gauge into the cab so you can watch it as you're going down the road, right? And if I read your post right, you're saying that you can hit 3 psi just stabbin' the skinny pedal in park, but you can't get over 3 psi on a WOT launch from 0-60 mph? Something doesn't sound right...

Have you double checked for leaks in the new plumbing? Hear any hissing noise while at 3 psi? And are you still throwing that code?

Could you post a pic of your wastegate setup?

[Hubert]

You'll have to set spring from boost reading under steady appreciable load. Once warm drive up a good long hill and apply heavy throttle smoothly and watch boost. Get some speed up for head wind load and try and hold rpms like posted above some where around 22-2400 RPMs w/o a down shift. It should build fairly quickly to a sustained ~10 psi max for a stock truck. As you get use to the boost gauge you'll see it dance around depending on load and fuel. Level ground light throttle it may only be 2-4 psi boost (depending on wind drag etc) hit a hill and it will go up crest the hill and down hill it will go back down it reacts pretty quick. You'll know if spring is too heavy as boost will go 10 psi plus. Too light of spring and low boost it will be blowing black smoke. Pull over and adjust. Heavy black smoke usually means high EGT's and is hard on the engine.

keep the boost gauge installed because the TM affords no overboost protection.

[spark3542]

Spring selection is absolutely swag.

I put in a heavier spring and torqued it down. The gauge read about 5 psi under road test conditions similar to described above. I did hear some hissing from the gauge at 5 psi, so I'll check the fittings on the back of the gauge. Right now it is piped with the cheesy polyethylene tubing that comes with the gauge. I'll work on making that more permanent.

Great feedback from this forum. I'll keep you updated.

Thanks

Mark