Engine/Transmission (1998.5 - 2002) 275's & comp.....how much boost to expect?

[Whitmore]

OK here's the deal, I have 275 injectors and a comp box with an hx35 and 14cm housing and only getting 24 lbs of boost. I can go under load with my 5er on and on a steep grade and the boost will hit 24psi and stop dead cold, I thought it would be an easy fix by adjusting my wastegate, checked it tonight and it opens at 28psi just like I requested when I ordered my turbo from Piers, my old hx35 with 12 cm housing and wastegate disabled could hit 32 psi... ... ... this is at elevation of 4000 to 5000 ft. OH and it doesnt matter if comp box is on 5x5, 2x2 or off all I can get is 24 psi.



My question is what should I expect to get?



Cheers, Kevin

 

[mgoncalves]

Kevin,



After our conversation the other night, I really think your comp may be suspect.





Matt

 

[juicedcummins]

On the 99 with the edge elbow and stock turbo I see 42-43lbs on 5/5. I run an adjustable elbow set @ 35lbs to try and save the stock turbo and head gasket. Fuel pres @ 13lbs on 5/5.

 

[RobbyRam]

With DD2's and a comp on 1X3 I get 30lbs boost. But for a while, I only got 10-15lbs. Turned out there was a pin-hole leak in the tube going to the gauge.

Bob in Sacramento

 

[Chris N5CWM]

More boost is not necessarily better. I read on this forum somewhere that more than 35 PSI from a stock turbo is asking for an oversped turbo and eventual damage. I'm hitting about 28 or so with the 275s and an early Edge 3-light fueling box, and adjustable brass boost elbow set to max.

All you need is enough boost to compensate for the added fuel so there is no major smoke show once on full boost. Air/fuel ratio stuff. That's the part I know about anyway. The only thing you will benefit from by increasing boost might be a little lower EGTs. I'd keep the boost under 35.

Do you have an adjustable boost elbow? Mine came with my fueling box from Edge. It's a brass 90 degree elbow with a hex set screw adjustable orifice.

 

[jrandol]

Mines an Auto but I do have an HX 35 w/ 12 cm housing on it. With 275's and the box off I can see about 22-23 psi at most. Now with the FMS cranked, I can get up to high 30's pretty quick no problem. I am thinking something must be wrong with your comp box or maybe with your gauge.

 

[plongson]

I have DDII's with a TTPM. I can get 32 psi sometimes but it usually levels out at about 28 when I have to get out of it. I also have a stock hx35 on the '99. See my sig...

When I passed your way last week and had a malt... (if you know what I mean)... These boost figures were the same. .

 

[Ramafid]

With my 275's and blue box on level one I can hit 34lbs with a 14cm non-wastegated housing and PDR 35. On the third setting I am sure I have hit 40-42 lbs. Just guessing because the guage stops at 35 lbs. Something doesn't seem right with your comp. Maybe the pump wires are not getting a good contact. Good luck with the fix.

 

[Whitmore]

OK, after reading these replys I think I will send my box into edge for a tuneup and then see what happens from there, I will keep you posted when I get it back with the results.



Cheers, Kevin