speed shift, boost spike

[jscott]

I looked around for anything that would help me with this but didn't find anything....I speed shifted my car for the first time a couple days ago...I'm only running 5 pounds of boost until I can afford to go forged, well I speed shifted 3rd to 4th and it pulled super hard so I did it again and watched my boost gauge and noticed it spiked up to 10 pounds....I speed shifted all gears and found it will only do it from 2nd to 3rd and then all the other gears....and I can "trick it" to spike if I build boost to 5 and then let off the gas then nail it and it will spike to 10.....whats going on with that? Is this something normal? is my wastegate sticking closed when I speed shift or something? any help with this would be greatly appreciated....I always drive aggressivly and now I know I can spike my boost, I will be doing it, even though I want to keep my engine in one piece if I know it's there I will use it so if someone can help me fix this I would appreciate it.

 

[BOOSTR]

While you're waiting for the funds for pistons & rods make plans for a new transaxle too. You either have a malfunctioning wastegate, larger diameter mid pipe, boost controller or something else going on as its not normal to spike 5psi at all. MSP is not a 60s era muscle car with a gearbox built for abuse. But its your car so knock yourself out whomping on it!

 

[jscott]

While you're waiting for the funds for pistons & rods make plans for a new transaxle too. You either have a malfunctioning wastegate, larger diameter mid pipe, boost controller or something else going on as its not normal to spike 5psi at all. MSP is not a 60s era muscle car with a gearbox built for abuse. But its your car so knock yourself out whomping on it!

I got rods just wating on pistons....I know how weak these gearboxes are, but an agressive shift is differant than abusing it....i'm not dumping the clutchat a dead stop or "slamming" gears.....but thanks for the advise....midpipe is out of the equation because it's not larger....i'm not sure how old the boost controler is though...is there a way to test it??

 

[Spiced MSP]

what turbo are you using boosting 5 psi with a boost controller? If it's a manual boost controller, it can cause a spike. Just remember t25 and t28's spool pretty quickly so add that along with that boost controller

 

[BOOSTR]

Well the MBC might be overadjusted. If its a TurboXS turn it clockwise to turn it down, couter clockwise on most other brands. Its normally to see a spike of 1-2 psi when being aggressive. Your cold weather may account for even more. Where does the boost settle in 3rd gear after an agressive romp.

 

[jscott]

turbo is the stock t25 with blox MBC turned all the way down....SSAFC read 5 PSI when I first set it, I haven't hooked my comp up to the car since seeing the spike......it won't happen every time into 3rd, when shifting if I let the BOV do it's job the pressure won't spike but if I speed shift it will hold 10 psi till I shift or left off the gas all the way to let the BOV blow off.....if I feather the gas but not let the BOV blow off it will just up to 10 if I step on the gas again.....but to "trick it" and get 10 psi I can built the pressure to 5 PSI, then snap off the gas (to let the BOV start to blow off) and then nail the gas again the boost will jump to 10 PSI

 

[tweety2300]

If you're only runing 5 psi why even run a boost controller? They can get really weird in cold weather mine sometimes fluctuates 3-6 psi

 

[jscott]

If you're only runing 5 psi why even run a boost controller? They can get really weird in cold weather mine sometimes fluctuates 3-6 psi

I bought the car with boost controller...i'm new to forced induction and don't want to mess anything up....stock boost is 7 PSI correct? And i'm running such low boost to save the life of my internals....they have been through alot and don't want to risk bending a rod or worse blowing a hole through another block....not until I get everything to forge