loss of power.....

[RFox]

i have lost my power at top end when towing. . i have my timing set at 17 degrees. . my question is should i turn the fuel screw up more, it is in about 11/2 turns. . or should in back off on the timing some ??. . truck runs great, egt's are down and no diesel smell... any help would be apprecated... will be towing trailer soon and would like some power back... . thanks in advance. .

 

[Philip]

Power loose at road speed could be a sign of fuel filter getting stoped up. Have you changed it yet?

 

[RFox]

power loss is when i'm pulling a grade... at highway speed it runs fine... i put new injectors in awhile back so i had timing advanced and truck runs great. . but now pulling a mtn. pass i loss power pulling the grade... was better before i did work... .

 

[Stomp]

Is there more smoke, now? What is your boost gauge telling you. Do you have a leak. Need more info.



Stomp

 

[dpuckett]

Yes, we need more info. Though from personal experience, I will say too much advance will bring power down across the band, but more so on the bottom end. What injectors did you install, and what are they set to pop at? If you dont know, find out from wherever you got 'em.



ALso, if you will, define "pulling a grade" and "highway speeds. " I thought they were about the same, unless curves on the grade dictated otherwise.

Daniel

 

[RFox]

injectors are bosch 190's , i bought them thru PDR... . don't know what the pop off is... . grade is what i call i 8000ft mountain... . highway is flat open road..... i'm leaning towards bring the timing back to around 15 degrees and seeing what happens... no leaks that i know of... smoke only when i put my foot into it... boost is at 15 to 20 psi when pulling up hill... . check sig for info on truck... .

 

[dpuckett]

15-20psi is all you're making NOW? With the 14cm housing and Bosch 190s, I'd expect a minimum 25psi peak. My last IC truck made 18psi bone stock- 93 D350, 3. 54, 5spd. How old is the fuel filter? What is your fuel pressure out of the lift pump? Where are your diaphragm spring & AFC cone set to?



If your truck did better a a lesser timing, I'd say move it back and try it there. Sounds like 15-16deg is about the max without sacrificing performance. But that is about 3-4 deg above stock. 2 deg can make a world of difference, to the good or bad, depending on where you started.



-DP

 

[SteveMiller]

I've heard that timing will affect low end torque. That might be part of the problem. Not really sure, since I'm just passing along the info without experience.



However, my 91 has a max boost of 12 so I decided that shouldn't be right and I checked for leaks and it won't hold pressure when I plug off the turbo and pressurize it with my air compressor. I've got to be loosing pressure somewhere and I think its the intercooler. You might have something similar going on.



Good luck

Steve

 

[RFox]

20psi is where banks sets the wastegate... but i have had the fuel turned up more then now and got 25psi of boost alot of smoke and bad mileage... so i don't know what to do first, maybe try turning fuel up some or back off on the timing... quess i will have to play around alittle bit and see what happens... .

 

[dpuckett]

Turning up the fuel will only get you more smoke, and less MPGs. Too far of an advance on the timing will bring the smoke back, though not quite as thick as with retarded timing. After timing back to 15deg, try tightening the AFC srping pressure (Starwheel upwards). If you are smoking badly, you are getting too much fuel anyway. I have mine about 2 turns down from the top, and it will still get up and move. Might turn your cone to about the halfway mark, as that will cut your zero boost fuel some. You're on the right track, though- just have to mess around till you get it where you can live with it.



-DP

 

[Philip]

What are your egt's going up that hill at 20 PSi of boost?

 

[RFox]

egt's running any where from 1000' to around 1200'... . thats with my foot in it.....

 

[Philip]

Raise the setting on the wastegate. With the temps your showing I would not do much on the fuel setting. So raise the boost some and see what that does.

 

[RFox]

doesn't opening up the wastegate raise the egt's ???... more boost and more heat ???

 

[Philip]

You need more air to lower temps. By readjusting the wastegate to allow for higher PSI of boost. You are putting more air into the engine. More air with your current temps will most likely mean more power.



If you have a H1C on the truck. Hold it to 30 PSI max. Anything above that is above the range of the turbo. It might cause damage.

 

[dpuckett]

Philip is right, more boost & fuel equals more power up to a point. At 20psi, you havent gotten to that point. I have seen 30psi with an H1C, and been ok. You run into backpressure/ EGT issues once you get out of the efficiency range of the turbo, which is about 25-30psi on the H1C, dedending on who you talk to. Hence, the wastegate, to lower drive pressures, or keep them from topping a set limit, and to keep the turbo in the Earth's gravitational pull.



-DP

 

[RFox]

how do you go about adjusting the wastegate ???. . do you have to remove anything, tryed to adjust the nut and it will loosen only... do you need to disconnect something to get wastegate to adjust in for more psi ???... hope you don't have to remove in order to adjust it... .

 

[dpuckett]

I know you have to unhook one end or another to lengthen or shorten the rod. Not sure which way to go to up the gate opening limit, but I seem to remember that lengthening it raises the pressure. Or you could unhook it for a few days or to make a bonzai run and see what it is making. Just go easy backing out of it to avoid barking it. I have had a few 12cm housings on a couple trucks, and never got around to hooking up the gate.



-DP

 

[RFox]

i turned the starwheel back 1/2 turn and i picked up 2psi in boost, should this happen ???... i haven't turned the timing back yet. . does the starwheel have anything to do with boost pressure ???...

 

[JMariotti]

I would test the lift pump. Sounds like a weak lift pump to me.