Engine/Transmission (1994 - 1998) Jacobs exhaust brake, Low power.

[wildmanben]

would an exhaust brake cause low power?

Buddy bought a 98 12v 5sp and it has the exhaust brake on it. He has the same setup and tuning I do, minus the timing and injectors. It seems to spool way slow until about 1800rpm, then it takes off. It doesnt smoke a whole lot either like mine. Was wondering if the brake was restricting the flow to reduce spoolup or whats the deal. Oh his has a Banks twin ram intake and compressor wheel also? Would that make a difference? Thinking about switching AFC housing and see it the problem lies in there. Any suggestions?

 

[wildmanben]

I also have a GSK3 thats coming this week, hope that helps out some.

 

[WDixon27]

could be afc adjustment, could be a airleak to the afc, could be fuel related, my 96 will get the boost gauge moving when i load it down by putting it in 5th at just under 1k rpm, i have my afc almost all the way loose and if i stomp it i get a nice cloud on take off

 

[Vaughn MacKenzie]

Hopefully the brake isn't hanging up and seriously restricting exhaust flow. That'll make EGTs go mighty high! Does he have gauges?

 

[Erniek]

I have a 97 12 valve with a plate, boost elbow, and 4" exhaust, and guages. After I installed the plate It took some adjusting of the AFC star wheel to get the best performance. If I had the star wheel turned too far forward, I got gobs of smoke, high egt's, and fast spool up, the boost guage would peg at 30 psi in just a second or so, then smoke would clear up. (more fuel will get the turbo spinning up quicker). If I had the star wheel too far back (towards the cab) I didn't get any smoke, very slow spool up, the boost guage would rise slowly and not make it to 30 psi, and no power until about 1800 or 1900 rpm. (The afc starwheel adjustment affects the pre-boost fueling. ) I would try adjusting it by giving it a few turns forward (towards the radiator). The adjustment is done by pulling the plug off the top of the AFC housing then just take a flat tipped screwdriver and use it to turn the starwheel (top of wheel towards the engine). a few turns. (The starwheel adjuster is similar to the adjuster for the rear drum brakes on your truck) It took me a few adjustments back and forth to find the best performance without too much smoke and egt's, but still a puff, then quick spool up and enough power at well below 1800 rpm's to slip my stock clutch if I am not carefull!!!



Maybe that will help??

 

[wildmanben]

From what I can tell, the brake isnt partially closed, Egts are normal to low. Takes a bit of effort to hit 1500. Will pull 35 psi once it spools. It just seems to spool way slow, hardly any smoke. I dunno, just acts doggy. The starwheel is all the way forward along with the afc and the plate, also has the medium TST spring in the afc. Could the spring be doing it? I have the light spring in my 98 and it spools instantly with a bunch of smoke. I will try messing with the AFC after work and see if anything is goofy there.

 

[Erniek]

It seems to me that with the star wheel turned all the way forward, it should be smokin like a train!!!, and the turbo should be spoolin up quickly with all the fuel and heat. Though I am certainly no expert, it sounds like you're definitely having a "fueling problem". Just a thought, has the fuel filter been changed lately? Any chance of putting a fuel pressure guage on and checking the lift pump press? I am not sure what the press is supposed to be, but I am sure someone on here does. I may be way off, but the fuel filter is simple and relatively cheap. Just throwin ideas out there.



Erik

 

[FDavid]

also has the medium TST spring in the afc. Could the spring be doing it? I have the light spring in my 98 and it spools instantly with a bunch of smoke.

I think thats your problem right there. I had the same exact slow spool up problem after installing the tst afc spring kit. A lighter spring would help considerably and if you want to totally eliminate the problem, take the foot lever out of the afc.



edit:



Something else I thought of that also has similar symptoms is if your gov lever is hitting below the plate http://www.piersdiesel.com/TechLeverAdj.htm

 

[wildmanben]

I checked the lever when I moved the plate and it seemed to be fine. I have heard a lot of guys running the 215 spring and having better results than the TST when adjusted right?

 

[wildmanben]

ok, changes fuel filter and cleaned the pre-cleaner. Also removed the AFC arm. Power picked up a lot and spools way faster. So the medium TST spring is a joke. Better put the 215 spring in. Or is running without the AFC arm ok?