94- 6.5L Desial Turbo Boost

[probuilder]

I have a 94 Chevy 4x4 Automatic Desiel 6.5L.
What is the boost amount from the turbo?
Can this be changed? or increased without harm to the motor.
The motor seams to be doggy, lately, and only running 2 lbs of boost max to the intake. Someone suggested wiing the waste gate ans EGR valve shut, at that point I can get 4 lbs of boost from it. But, I am afraid of ruining something running it that way.
Opinions please.
Thanks in advance for all your help.

[Pamsdad]

In STOCK form, you will see 7psi of boost.

This can be changed 3 different ways. Electronic boost controller, Mechanical boost controller, or Computer 'Chip'.

Do not wire your wastegate shut. This is sometimes done for test purposes. Don't even try it without a boost gauge.

If your not getting boost(more than 2psi), sounds like you have a problem with either the vacuum pump, vacuum lines, wastegate solenoid, or actuator.

You have removed the catalytic converter, haven't you...

[probuilder]

No, I haven't removed the Catalytic converter yet. I just got the truck and wanted to see what it was doing before I started swapping parts.

[Pamsdad]

You don't have to remove it completely. You can take it off the truck, hollow it out, and reinstall on truck. No one will know that the guts have been removed. That's if your worried about State inspections.

A lot of troubles on high mileage 6.5's can be traced to a clogged 'cat'.

Their is no place for one on a diesel. Once cat is gutted, a noticeable improvement in power should be felt. After that is completed, you'll be ready for a Hi-Flow exhaust.

[probuilder]

I am already running a Straight pipe (No muffler) from the Cat back to the tail pipe.

[Pamsdad]

Having a straight pipe is fine. The muffler is not the restriction though.

The CAT is...

Let's get back to your no boost problem. Do you have a boost gauge? Do you have a vacuum gauge? Check vacuum at idle at the waste gate actuator. You should see near 20in.

Wanna learn a lot with some reading? Go to www.thedieselpage.com.

[probuilder]

thanks for all the info.
I have a boost/vaccumn gauge on the truck, hooked into the intake. I also have a vaccumn gauge that I can use to check the wastegate with. I will read the article that you linked to and do some piliminary tests and get back to you.
Thanks again.

[probuilder]

Ok, I have removed the Cat and am now running a complete straight pipe in 3". I am getting a max boost of 4 PSI with the Wastegate wired shut, and a max boost of 2.5 with everything hooked up the way it is supposed to be.
I am not getting any vaccumn from the pump. Is there a rebuild kit for this or do I just need to buy a new Vaccumn pump for this truck?

Also, the AC and Vents are working the way they are supposed to inside the truck. Is there a separate vaccumn pump that runs the interior vaccumn goodies?

Thanks again for all your help.

[Pamsdad]

The vents are not controlled by vacuum IIRC.

It sounds like you may have 2 different problems pertaining to low boost levels. Provided your gauges are accurate, 4psi of boost with the wastegate wired shut doesn't make sense. Check the wastegate lever, it should have roughly 90 degrees of travel. Maybe what you thought was wired shut really wasn't. Doing this usually gets max(8psi+) boost. If lever is not traveling fully, free it up until it does.

The second problem is no vacuum at wastegate actuator. 15-18in should be on gauge at this point. A little higher at pump itself. Pump might be bad. Very common. No rebuild kit as far as I know. $75-125 depending on where you buy it. One thing to look for that is common is the vacuum lines coming from wastegate solenoid on rear of drivers valve cover to the actuator get very brittle and brake.

If you've checked vacuum reading at pump and have nothing, you have found your vacuum problem. Replacing pump without getting a fully closed wastegate will not solve your problem though.

Did you pull any codes?

[probuilder]

I don't have a code reader for the desiel engines. Is there a way to check them with a paper clip and the service engine soon light?
Do they make a cheap code reader?

[Pamsdad]

Your truck is Pre-OBDII(96+). Yes, a paperclip will pull codes with the SES light. The 2 terminals at the far right of the ALDL connector right under the steering column. The top right & the bottom right ports.

Count the flashes...

[probuilder]

Ok, here is the new wrinkle.
I fixed the vaccumn pump and now I am getting a max of 9 psi of boost. But I am heating when I run that much boost, a temp of about 230 all the time and will climb fast if I pull anything.
Any Ideas?
Thanks, Troy

[Rbraczyk]

If you put an intercooler on it it may bring the temp down. Just a suggestion if your forcing that much hot gas into the engine.

[Pamsdad]

Glad to hear you fixed the boost problem. Vacuum pumps are very common on these trucks.

Now onto your new problem. I'm assuming when you say 230*, you're referring to coolant temperature. Intake Air Temperature is another problem. I don't know how much weight you are towing but here's what could be wrong:

Unfortunately, GM didn't put the Hi-Flow water pump and Dual thermostat that increases flow tremendously on their trucks until '97. You have the single stat, lower volume pump on yours.

Thermostats are good, right?

The most common problem, and maybe yours, is a blocked radiator. There is a lot of junk that accumulates over the years between the radiator and A/C condensor.

Maybe a Fan Clutch. Did you hear it kick in while you were towing at about 210*. You should DEFINATELY have heard it.

Oh yea. What about coolant level. Is it full? Has the system been bled? Maybe an air pocket?

Check it out. Don't rule out the simple/obvious.

[Rbraczyk]

I know what he meant, i just suggested it if he didn't have a coolant issue. I realize that. Maybe a high velocity electric water pump would work well.