boost usually climbs to 10+ #'s...drops to 5-6 #'s @ 1-2 shift...then climbs back to 10+ #'s...(TB converter)

last night:
boost climbs to 10+ #'s...
1-2 shift...drops to 5-6 #'s...
boost then only climbs back to around 8 #'s...???

changes from last tuning session...

smaller tires...30" street tires to 26" MTDR...have always run these though...when tuned last w/ street tires, tune was changed to shift by rpm instead of mph...which should have eliminated the need to change tune to run the smaller tires, correct?

93 octane to 110...if too much octane, it could decrease power but not boost level, correct?

changed tires back to 30" street tires...filled up w/ 93 on the way home...SAME TUNE...stopped...went WOT...boost climbed to 10+...1-2 shift dropped boost to 5-6...then it climbed right back up to 10+ before letting out...???

 

is your bov working correctly?

 

I did have a issues w/ it a few months ago, but it seemed to be working last night...
before, it would not let me boost beyond 7-8 #'s at all...I assume because it wasn't closing...removed it, cleaned it, reinstalled it...no more issues...
this time, I reached normal boost level, just never returned to that level after shifting...until on the way home w/ the taller tires and 93 octane again

It is odd though that the level of boost after shifting was the same as when the by-pass valve was malfunctioning...that's why we checked it first...

 

well the taller tires could be creating more load which = more boost. but the bov could not be flowing enough not letting enough air escape to get the blower spooled , they arent exactly like turbos but the centrfigals are very similar.

 

that was another thing I did before putting it back on last time was a MUCH larger K&N filter on the by-pass rather than the little Summit filter I had on it...

 

also...these are the same MTDR's that I have always run...my best ET is on these...and prior to last night they have always performed similar to the taller ones with the exception of when we had it shifting by mph, we would change the tune prior to running the smaller ones...elimating the need to do this by setting it to rpm's is really the only thing we changed other than the higher octane fuel...

 

Are you positive it was shifting at the same rpm's with the 26 in tires versus the 30 in tires?

 

sorry for the delay in replying...been at my 2nd job all day...
no, I'm not sure...Jerry had the laptop in his car until my last pass and then we logged a run but he didn't think that I had hit the space bar to stop the logging and I had...so when he hit it again, the log was deleted...

my only question would be, why would it NOT shift at the same RPM?

 

Could be that it was shifting at MPH or RPM's depending on what it reached first? Thats all that make sense to me, since the blower is RPM dependant it should make the same boost at the same RPM regardless of tire size,fuel.

 

Obviously the blower gets boost from rpm.So during the shift the rpm goes down which makes the boost go down.You should only be getting the 10lbs at a certain rpm,any rpm under that should be a lower boost level.

The only other problem if the boost isn't the same at the rpm is that the belt is probly slipping.