Tuning for PD Blowers... Transient Fuel Manifold Volume

[STL_G8GT]

Guys this has been rehashed in a few different places, so there wasn't a logical place to drop it, so here goes...

When tuning for PD blowers... Maggies, LSAs, etc, under what circumstances do you adjust Manifold Volume under Transient Fuel?

I ask because if you look at V2s and LSA cars, you'll see their Manifold Volume is set to 13487 for the 1900(1.9l) series blower. But when you look at ZR1 (2300(2.3l) series blower) factory tunes, the volume is actually 10,038, slightly lower than the stock G8 figure, which is 10,040.

A while back Hartigan85 and a few others were having some open loop lean tip in issues. I solved mine by just richening up OL tables below a certain ECT threshold, but if I blip the throttle while driving, even in closed loop, I do get a lean spike for a split second before it comes around. I don't know that I've paid enough attention to notice if there is hesitation as well, but I'd like to see if I can smooth that transition.

My current Manifold Volume is the stock G8 value, at 10,040.


Edit: Part of me thinks that if I go fooling with this, that the Manifold Volume figure will impact other areas of drivability that have already been tuned for/compensated for with other areas.

[norm8332]

I get this too never did figure it out..Subscribed

[Phil@PnP Tech]

I'm experiencing this as well. It will go into PE, be tracking on target for roughly 10 frames... then all of the sudden IPW will start to fall off for a few frames. It will dip about 0.5msec causing a lean spike.

Airflow climbs steady so it has lead me to believe it's a transient fuel issue. I must have came across the same information as you did about the manifold volume. I'll flash it tomorrow and take it for a spin.

[STL_G8GT]

I'm experiencing this as well. It will go into PE, be tracking on target for roughly 10 frames... then all of the sudden IPW will start to fall off for a few frames. It will dip about 0.5msec causing a lean spike.

Airflow climbs steady so it has lead me to believe it's a transient fuel issue. I must have came across the same information as you did about the manifold volume. I'll flash it tomorrow and take it for a spin.

Supposed to rain here tomorrow afternoon so no testing it for me. Let us know how it goes. Otherwise I might be able to get it out Saturday.

Seeing the zr1 values so low caught me off guard... They must tune around it another way... But of course I've got no idea how.

[Niemer]

I'm experiencing this as well. It will go into PE, be tracking on target for roughly 10 frames... then all of the sudden IPW will start to fall off for a few frames. It will dip about 0.5msec causing a lean spike.

Airflow climbs steady so it has lead me to believe it's a transient fuel issue. I must have came across the same information as you did about the manifold volume. I'll flash it tomorrow and take it for a spin.

This sounds like the 2.1 second lean spike issue. Make sure you have desoot mode turned off.

[Phil@PnP Tech]

This sounds like the 2.1 second lean spike issue. Make sure you have desoot mode turned off.

I think it wasnt too long after this post I stumbled upon the desoot over on HPT. The lean PE spike has been haunting guys for years it seems.


Sent from my SM-G930P using Tapatalk

[Niemer]

Tell me about it, I think I started the first thread over there about it in 2013 and it finally got solved 4 years later.

[norm8332]

This is good to know, I updated my software and will be trying this in the spring, but this only affects PE tip-in correct? I have a non-PE from a stop tip-in issue with a lean spike also.

[norm8332]

I think it wasnt too long after this post I stumbled upon the desoot over on HPT. The lean PE spike has been haunting guys for years it seems.


Sent from my SM-G930P using Tapatalk

This did a great job at stabilizing the PE mode through the RPM range, but I'm still trying to locate the cause of non-PE tip-in knock I get. Light throttle lean tip-in without engaging the blower, and lean tip-in knock prior to PE mode. Anyone know if this is something addressed by the manifold volume settings?

I also never tracked down why I get a large lean spike when shifting from reverse to drive when trying to go. After backing up and putting into drive, the first tip-in is a huge lean spike and it actually bogs for a second.

[Phil@PnP Tech]

Is it burst knock?

Sent from my SM-G930P using Tapatalk