Hey everyone.

My problem is that with the 99 twins, and boost controlled by the PFC I was tuned to run about .83 to .89 bar. Recetly i can't boost past .79 bar being the max -- most of the time its .69 bar. im not sure what this is due to.

Ive checked and rechecked the IC couplers and I have on order a new set of check valves. When I do a graph on the PFC of boost and RPM the boost graph looks fine just lower than normal.

What is causing this?

could it be bad compression? - bad check valve? - boost leak? - bad boost selinoid? - warmer weather?

I alrealdy searched the threads about this but you all know as well as i do there are thousands of threads containing the words that i need to look up a simmilar problem.

 

Not a compression problem, and you've checked for boost leaks. Probably not the solenoids or check valves, since that usually affects things below or above 4500rpm.

The warmer weather can often swing boost by a psi. When was the boost tuned? Does adjusting the PFC restore the .83bar level?

Dave

 

The only things I can think of that would limit the boost to some lower level at ALL RPM's are:

1. Controller setting (boost sensor?)
2. Boost leak
3. Leaky WG or WG actuator stuck partially open

Everything else (clogged cat, collapsing intake hose, leaky check valves, etc.) have more effect in one RPM range than another.

 

Does it happen in all gears? I have a similar problem mostly in lower gears intermittently on the secondary turbo. Also on part throttle acceleration just past transition boost jump all over the place. It makes for a very unrefined experience. Leads me to believe its wastegate.

At sea level in FL the 99' will hold .90 all the way to red line on a hot day in 3rd.
All of these bugs have made me strongly consider going non-sequential low-end lag is pretty by modern standards. Even though I can reach .90 boost by 2500 in higher gears it doesn't really have the much down that low.

 

With the pfc I have tried to adjust the boost back up to normal but its not seaming to work. on the percents at the far right of the boost settings screen I raised them all about 6 or 8 percent. And I also raised the middle number on all four lines by one click (or i think 5)

at most this has helped about about .05 bar maybe from .74 to .79 bar

should i adjust this more?

 

how would i be able to tell if the actuator was stuck? The turbo's are new 99 spec with only 10 thousand miles on them....

Hopefully i will be one of the first testers of boost leak kits on FD's

 

Yeah Ive also been thinking about the non sequential mod. I haven't tried this in 4th for any long period of time but in second and third the boost patern is great its just the humps spike at less then .79 bar. Im at sea level and have tepuratures between 70 and 80 degrees F. but i was tunned in 40 degree weather..... about 7 or 8 months ago.

 

bump

 

Is there any chance your cat(s) are clogging?

 

I was kind of wondering the same thing. I have a down pipe to remove the pre cat but the mid pipe is original.... with 101k. Also I noticed that when Steve Kan last tuned my car it was insanely rich because i maxed out my stock injectors at 6500 rpm.

Isn't a cause for clogged cats runing too rich?

I guess Ill have to break out the thermometer and see..... but I did notice that when i start the car it spits black specks from the exhaust pipe and its not oil so I dont know if that means your cats clogged or not ... just a thought.

 

Well if you're running abnormally rich then a cleaned set of injectors would also make a lot of sense.

Dave

 

This is true... I may have to go with the 1300 and get my new tune to see if that helps things