I have been trying to find the cause of this problem for quite a while now. I can not get my boost pressure over 15 lbs. While under pull with egt's at 1200* at wot pulling my 11k fifth wheel I can not get enough booth to clear the smoke out of the exhaust. I have checked all the connections from the pump to the manifold. Everything is tight. I can't get enough boost to clear the smoke while under power. This isn't as much of a problem as I can't use the power gained from the pump mods because I can't get enough air into the mixture. Has anyone ever heard of a blockage in the intercooler from the factory? I have always had this problem from when I bought the truck new. Or at least from the point when I did the pump mods and installed the gauges.

What kind of boost are you guys getting with a 16cm turbo housing? I was thinking about measuring the boost before the intercooler and seeing what the difference was at the manifold. How much drop should I expect or how much pret intercooler pressure should I be producing?

Thanks for the help

 

Did you check all the piping and boots between the turbo and intake horn? Any noises of air escaping or anything?

 

It is possibly you have a hole in the AFC diaphragm (yes it is spelled correctly)

This would not let the diaphragm move the fuel rod to maximum. This would also
keep your mods from showing the expected improvements.


my $.02

59

 

Yes. I pressurized the system from the air cleaner through the system. There are no noises and the system holds air. I put soapy water on all the joints with not signs of leakes. No sounds of leaks nothin.


I definatly have more power since the mods. There is no question about the improvement. She runs much stronger aand pulls much better but my boost is not what I expected and the smoke doesn't clear until I lift the throttle. The problem is the egt's are goin up because there isn't enough air in the mixture. I would be able to use the mods to a greater advantage if I could get more boost. I just had the diaphragm out yesterday and it looked fine.

I just can't figure this out. Only thing I can figure is a blockage in the intercooler but that is remote but not impossible.

Do you guy's have any idea as to the boost I should be getting before and after the intercooler?

 

BTW guys, I'm baffled too. I was the guy spraying soapy water all over everything yesterday. Could not see or hear any leakage, but the truck runs hot and smoky like it's not getting enough air. Filter is a drop-in K&N, so there should be no restriction there.

The only thing I could think of was a restricted intercooler, so hopefully Gary will rig up a boost gauge to the turbo outlet. Gary, you don't want to see more than 3 or 4 psi difference between the gauges. It will drop that much due to the temperature change across the intercooler.

 

did the turbo spin freely? any signs of it being a bit grindy? did you count your shop rags after working on the motor? might have stuffed a pipe with a rag and left one or thought there was one and there were two//// check the top of the heater grid thats where half of them would make it to...... how bout a mouse house in the filter box?

 

Turbo is good. One of the things I wanted to check was whether or not the turbo came from Holset with too small a compressor wheel for the housing. Not the case. Good thought to pull the air horn off, never know what you might find in there.

 

Hey I can do that in the morning. The boost has been down for as long as I can remember. As soon as I put the gauges on it, about 2 years ago is when I noticed it. That is when I bumped the pump up. The truck is garage kept so it is unlikely but not impossible to get a squirrel nest in there. LOL I will check.

Dave I am planning on checkin the boost before the intercooler this week. I'll let ya know what I find out. I am also callin for the springs in the morning.

What the heck else can it be?

 

leaky wastegate? bit o carbon chunk wedged in there.....

 

Good idea but no. There is no wastegate on the turbo.

 

I'm stuck at 26psi max. When you find the problem let us know.

 

26 psi !!!!!!!!! I'd vote for Hilery for that. Well maybe not.

 

--> OFF TOPIC <--


If you're running an absolute stock PDR HX35/14 WG turbo, the wastegate actuator's set to start dumping at 25psig.

I've got the wastegate's actuator's reference hose pinched off till I can figure out a working controller. 37psig max currently after the IC.

 

No I don't have a wastegate that I know of. This is a stock 92 with the exception of a 16cm turbo housing and pump mods. I don't have any restriction in the intake horn but the AFC filter was dirtier than I expected. I am cleaning it now but don't expect it was that dirty to make a difference. This is goin to sound bumb but I am grasping at straws here. I there a way to turn up the boost? Can't see that there is but thought I would ask. Like I said I am up against the gov at 2600 rpm and 1150 to 1200* egt pullin a load and can't get over 15 psi boost. I would think something is wrong here. Maybe that is all she will do but I thought others are doin much better with the same setup.

 

I have just about the same set up as you, and I get 18 psi maxed out. I do haze alot when I have the loud pedal buried, but not smoke. I don't know how far the fuel screw is turned in, but it is as far as I can, while keeping me from exceeding 1250F on EGTs. That was done on purpose.

John