Boost Fluctuations
 

Having a problem with boost fluctuations after turbo transition at about 5000 rpm and up. It will fluctuate +/- 1 psi of the target boost. It does not happen when the PFC duty cycles are turned down all the way and the WG spring limits boost at around 7-8psi.

Does any one have any clue what this could be??? Anyone ever experience anything similar with the stock boost control and a PFC??

Datalogit logs show the WG% fluctuating with the boost, what in the hell is causing this???

Searched already and found nothing, already ran all of the factory trouble shooting on the WG actuator, solenoid, and the vacuum lines.

Any help would be greatly appreciated, as running around at 8psi SUCKS!

Jon
'93 SSM base

Jon,

Any help with this? Isn't there another thread with the exact same problem?

Tim

No thanks to either the Forum or the Datalogit list I was able to fix this problem.

Turns out that the program that came as the default "reset all" in this particular version of the PFC was messed up from Japan. As soon as I loaded a default set from another PFC version with the datalogit it stopped completely.

Who knows? Goofball Japanese programers need to run debug type like stuff before they ship out their magic boxes :)

Jon
'93 SSM base

That is very odd. Your conclusion implies the pfc program does more than can be observed/changed with the datalogit. I would like to determine what this unseen 'error' is. What version did you start with and what did you replace it with?

Hey FitzRX7, does my dyno graph from this post look like what your car feels like. https://www.rx7club.com/showthread.p...hreadid=273699 From what you describe I swear that we are having the same problem. My boost fluctuates about 2 psi under target and then back and forth. Let me know how you fixed it if you find out how too. I am stumped. It could be something to do with the dataloggit because my mechanic got on there to change the temp in which the fans came on to keep heat down in the summer. I don't have the dataloggit yet personally but if I find out that it will help me correct this problem then I would purchase it.

^^

Thougth Id resurrect this old thread as I have just experienced this same problem the last couple days.Started search and found this. Whats weird is I dont think its the PFC but the datalogit. everything was fine until I had to reload my saved settings after initilizng PFC then boost started fluctuating between .80 and .90
at WOT. file was exactly the same settings as before I reinitialised nothing different just saved and reloaded and boost goes crap!!

I have done a little tuning on a car with the same exact problems.

The owner had a shop install a boost gauge. After AFR tuning was finished, I checked it and found no pill in the line for it. Later after he check the manual, it was suppose to have a pill in the line to reduce fluctuations. But this was not the cause of the problem.

Since we were only logging AFRs, they did not show what was happening in the PFC. The last log on the way home was BASIC and ADVANCE functions from 0mph to 100mph.

This is what I found: only in first gear was the TPS voltages constant at about 4.9 volts. The rest of the gears showed the TPS voltages jumping around.

Boost and other values are expected to change, but with the throttle floored, the TPS voltages should be constant! Either the guy suffers from shacky leg syndrome or something is loose in the throttle linkage or TPS.

The owner has not come back for me to trouble shoot and fix the problem with either the gauge or TPS.

I think its really the datalogit, but I cant understand why it does it. as we are only playing around with numbers and I thought numbers are numbers but If I make changes to the settings using d/l car just doesnt run right, feels flat and boost fluctuates as described above.....I have confirmed this today after initialising PFC using the commander only,entered exactly the same numbers on my saved files but using only the commander, went out for a drive and everythings back to normal, no boost fluctuations,pulls hard and car run beautiful.

Can anyone with the same problem try re-inialising PFC using commander only and see if its fixes the boost fluctuation problem or is mine just a one-off wierd situation.

Chuck, Ive posted on the d/l group and hoping steve or Glenn will notice.
your input would be appreciated as you have more experience with d/l than
most of us here.