Boost Spike

[PMJ]

Originally Posted by Supercharged SS

Try pm'in Ayousef. That guy knows quite a bit of stuff. He may have an idea.

Thanks. I pm'd him.

[ayousef]

Originally Posted by Supercharged SS

Try pm'in Ayousef. That guy knows quite a bit of stuff. He may have an idea.

Thanks!

Originally Posted by PMJ

Thanks. I pm'd him.

Well I have an idea in mind already based on the print screens but cant be too sure, can you send me the log and the file by email? I want the log from where you got the initial printscreen from.

Also, to get correct boost readings always make sure you subtract the Barometric pressure in PSI from MAP PSI, this is the only correct way to do it.

Using a static number such as 14.7 or 14.5 to estimate barometric pressure may only be accurate 10% of the time.

But thats not the problem. Ill send you my email address as a PM

[carlos@redline-motorsport]

Originally Posted by PMJ

Are you saying I got on the gas before letting off the clutch? Or the clutch slipped after I engaged it and hit the gas? It is a mcleod RXT, so I wouldn't expect slip. I think I see a little tire spin as well.

I'm going to post another example prior to my engine mods and new clutch when I get home tonight.

Yeah, looking at it again looks like tire spin.

Would be nice to see throttle blade position and pedal position to see what you are actually telling it to do vs what it's doing.

What happens if you go WOT in say 3rd or 4th gear, let off completely around the top of the gear and stab it again without shifting really quick? Also, what happens if you stab it from a high 3rd or 4th (somewhere that you get traction) gear roll? Also, rescale the speed and rpm in order to show more drastic changes in the graph.

Also, does this car have cats or cutouts?

[ayousef]

Originally Posted by carlos@redline-motorsport

Yeah, looking at it again looks like tire spin.

Would be nice to see throttle blade position and pedal position to see what you are actually telling it to do vs what it's doing.

What happens if you go WOT in say 3rd or 4th gear, let off completely around the top of the gear and stab it again without shifting really quick? Also, what happens if you stab it from a high 3rd or 4th (somewhere that you get traction) gear roll? Also, rescale the speed and rpm in order to show more drastic changes in the graph.

Also, does this car have cats or cutouts?

Carlos, clutch slip or tire spin could not possibly cause a boost spike at all on a blower car, there is absolutely nothing that should cause boost to go up unless you're spinning the blower much quicker at a given RPM and even thats not possible unless the blower's carrying momentum from being spun at a high speed and over boosting at a lower rpm, even this doesnt make sense.

I do have some weird ideas however especially since MAF frequency isnt as high as it should be when the spike occurs.

[PMJ]

Originally Posted by ayousef

Well I have an idea in mind already based on the print screens but cant be too sure, can you send me the log and the file by email? I want the log from where you got the initial printscreen from.

Also, to get correct boost readings always make sure you subtract the Barometric pressure in PSI from MAP PSI, this is the only correct way to do it.

Using a static number such as 14.7 or 14.5 to estimate barometric pressure may only be accurate 10% of the time.

But thats not the problem. Ill send you my email address as a PM

Fantastic! I'll get that e-mail sent out ASAP.

Originally Posted by carlos@redline-motorsport

Yeah, looking at it again looks like tire spin.

Would be nice to see throttle blade position and pedal position to see what you are actually telling it to do vs what it's doing.

What happens if you go WOT in say 3rd or 4th gear, let off completely around the top of the gear and stab it again without shifting really quick? Also, what happens if you stab it from a high 3rd or 4th (somewhere that you get traction) gear roll? Also, rescale the speed and rpm in order to show more drastic changes in the graph.

Also, does this car have cats or cutouts?

The car has OBX Hi-Flow Cats...I have considered that as one possibility, but i would think it would occur all the time, not just some of the time.

I am hopefully Ayousef finds something, but i like some of your suggestions...I'll see if getting off the throttle and punching it will reproduce it. I'll also see if i can add logging for throttle and pedal positions.

Thanks,
Pat

[yonson]

Has this calibration been scaled? You might have missed something during scaling...

[carlos@redline-motorsport]

Originally Posted by ayousef

Carlos, clutch slip or tire spin could not possibly cause a boost spike at all on a blower car, there is absolutely nothing that should cause boost to go up unless you're spinning the blower much quicker at a given RPM and even thats not possible unless the blower's carrying momentum from being spun at a high speed and over boosting at a lower rpm, even this doesnt make sense.

I do have some weird ideas however especially since MAF frequency isnt as high as it should be when the spike occurs.

I wasn't implying that was the cause, just pointing it out.

Like I said, hard to figure out what's going on without seeing what position the throttle blade is at. This is why I was asking him about quickly interrupting a pull pre-gear shift. Also, because the PD blowers make instant boost and it's not really dependent on RPM, the only thing that would cause boost to legitimately go up would be a restriction down stream. That is, if it's not the MAP showing pressure backed up behind the throttle blade and the bypass isn't reacting fast enough, as the MAF doesn't seem to be on the same page, like you just mentioned.

[Mike TexaSS]

Ive seen boost spike on CTS-V's when you hit a lean spot.

Id bet your tune is off. If you look at your logs the 02 voltage is extremely lean when the boost spike occurs!

[Mike TexaSS]

Also are you 2.5 bar SD? Or OL MAF? CLMAF.. Details buddy details!

[ayousef]

Originally Posted by Mike TexaSS

Ive seen boost spike on CTS-V's when you hit a lean spot.

Id bet your tune is off. If you look at your logs the 02 voltage is extremely lean when the boost spike occurs!

You're saying the lean spike is causing the boost spike, hes saying the boost spike is causing the lean spike

hes running a MAF closed loop tune

[PMJ]

Originally Posted by Mike TexaSS

Also are you 2.5 bar SD? Or OL MAF? CLMAF.. Details buddy details!

3 bar ZR1 MAP. Stock MAF.

[PMJ]

Originally Posted by Mike TexaSS

Ive seen boost spike on CTS-V's when you hit a lean spot.

Id bet your tune is off. If you look at your logs the 02 voltage is extremely lean when the boost spike occurs!

My O2 voltage is really lean of every gear shift (w/or w/o boost spike)...is that not normal?

[Mike TexaSS]

Im not a fan of closed loop maf tunes.

If you must tune maf (ugh!) open loop is the way to go.

Id take advantage of the ZR1 map and go SD!

[PMJ]

Originally Posted by Mike TexaSS

Im not a fan of closed loop maf tunes.

If you must tune maf (ugh!) open loop is the way to go.

Id take advantage of the ZR1 map and go SD!

Already discussing that w my tune, just haven't made the time to convert it yet. Likely in the near future.