Questions about timing on VP Commodore V6

[immortality]

I thought the myth of the bellmouth was to improve air distribution.

They changed the cam in the later models to tone down the low end throttle response.

People tend to forget that most average drivers don't daily drive at WOT and as such that number is almost of no consequence.

[Charlescrown]

Is the bellmouth the plastic deflector fitted between the throttle body and the manifold?

[immortality]

Yes it is (sits between the TB elbow and the manifold).

[silentshout]

Looking at the VE tables for fueling for both the VP and the $12p it seems apart from the wild size difference, they are very similar.

Ill give the VP timing a go and monitor for knock. Another thing i noticed was the ADX for the 12p firmware seemed to have a few things out. like road speed never went above 30kmph, Coolant and Intake temps seemed way higher than normal.

Intake temp reaching 68 - 70 degrees im not sure thats right, the calculated charge temp was measuring in the 100s

Also coolant would be low 100s as well, but on the gauge it was reading fine and no boiling, nothing to show it was getting that hot.

[Knackersjewels]

Looking at the VE tables for fueling for both the VP and the $12p it seems apart from the wild size difference, they are very similar.

Ill give the VP timing a go and monitor for knock. Another thing i noticed was the ADX for the 12p firmware seemed to have a few things out. like road speed never went above 30kmph, Coolant and Intake temps seemed way higher than normal.

Intake temp reaching 68 - 70 degrees im not sure thats right, the calculated charge temp was measuring in the 100s

Also coolant would be low 100s as well, but on the gauge it was reading fine and no boiling, nothing to show it was getting that hot.

That's all normal stuff.
Road speed is based on speedo pulses, so you'll need to change that to suit the vehicle. Different transmission/diff ratio = different speed ppk.

Intake temp in the buick is manifold temp, not intake temp. It suffers from heatsoak, so does read much higher than a later model with a maf.
Calculated charge is a ratio of manifold temp, and coolant temp, which can be changed in the calibration.

Most coolant temps I see are 85-95, and the gauge is at the lowest mark above cold.

[Charlescrown]

I remember that little piece of curved plastic and the local dealer at the time called it a rough idle corrector. I had one for years in my bag of tricks when teaching.

[vlad01]

Looking at the VE tables for fueling for both the VP and the $12p it seems apart from the wild size difference, they are very similar.

Ill give the VP timing a go and monitor for knock. Another thing i noticed was the ADX for the 12p firmware seemed to have a few things out. like road speed never went above 30kmph, Coolant and Intake temps seemed way higher than normal.

Intake temp reaching 68 - 70 degrees im not sure thats right, the calculated charge temp was measuring in the 100s

Also coolant would be low 100s as well, but on the gauge it was reading fine and no boiling, nothing to show it was getting that hot.

That's all normal stuff.
Road speed is based on speedo pulses, so you'll need to change that to suit the vehicle. Different transmission/diff ratio = different speed ppk.

Intake temp in the buick is manifold temp, not intake temp. It suffers from heatsoak, so does read much higher than a later model with a maf.
Calculated charge is a ratio of manifold temp, and coolant temp, which can be changed in the calibration.

Most coolant temps I see are 85-95, and the gauge is at the lowest mark above cold.

This is the charge temp thing I was talking about, I found knock at the edge cases is not tied to charge temp or even coolant for the mater of fact, at least in the condition that can coax knock out of hiding, it was highly linked to air temp and the co-factor of atmospheric pressure. Very annoying they don't have a Spark offset vs MAT table. This is why I would like to try at one point to setup a flex table to do the tably thing and force the spark offset via a map switch. This will also be preventative to knock and not reactive, which if it works would be a big plus over the traditional knock retard, prevention is better than cure as they say.

[vlad01]

I remember that little piece of curved plastic and the local dealer at the time called it a rough idle corrector. I had one for years in my bag of tricks when teaching.

I didn't really notice the idle thing with or without personally, I think all of these engines idle rough, even brand new, eg, super low K or a reco engine, still idle with that erratic random jidder. You can only tune that out so far, the engine is designed in such a way they are rougher than the average, but we don't care do we!

[delcowizzid]

The plastic bellmouth helps distribution for your normal daily driver at part throttle where the oldies buying a brandnew vn drove lol but for full throttle stuff it gets in the way.we used to mod them 27+ years ago some people cut them on an angle some drilled holes lots of things were tried .can probably find some posts on justcommodores.com.au on how they were cut. Early vn had a different plenum and runner design vp up the floor moved and it made fuel distribution change due to how the air flowed past the runner entries.all my vp tunes back then were based on the BAAM bin as I bought a vp to use as a test car and my mate had the vn test car lol .my vp had hundreds of tune revisions using an eprom burner and uv eraser and logging with winaldl and using a gtech for 1/4 mile testing for gains .got into the 13s with unopened engine just a trick cai and pacemaker headers with twin 2.25" custom exhaust

[silentshout]

Hey all long time no see. The modified 808 ECU is up and running, and big thank you to all the contributors for the wealth of info on here.

I figured id continue this thread as we have come across something timing related, We put about 75% of the vp timing into the spark advance table to ensure it was all working and down low everything feels strong however around 3900 - 4000rpm it tapers off alot.
Looking at logs it seems the Knock retard kicks in around 4krpm and above and it starts detecting knock events.

Power around 4000rpm or later is very very flat as well. A thing to note is we removed the bellmouth insert however the car was exhibiting the same issues even with the bellmouth installed.

We have an AEM wideband to throw in (I believe the analog 0-5v output goes into Pin D8) so cant see what fueling is doing at the moment outside of what the ECU is commanding.

I have some questions from our findings:

"Current VE"
Is this a calculated VE value based on sensor input math?, or is it whatever is listed in the active cell for the VE table (and thus changing it in the table changes it in the data list)

Calculated VE.jpg

"Events that may occur around the 4000rpm mark"
Are there any events that may happen around the 4000rpm mark that would change fueling in a VP series 2?
it seems pretty repeatable over about 70% throttle where knock retard kicks in (until its only running around 8 degrees of timing) and then it starts detecting some knock events

Injector duty cycle seems fine (tops out around 73%) Injector BPW topped out at 17.68, nothing seemed out of the ordinary.

Is it possible old injectors can struggle over certain thresholds?
The car feels very strong down low and all looks healthy its just that pesky 4k rpm wall.

As a test we slapped on the base OSE12P timing that comes with the NVRAM out of the box for this car and it was still pulling timing at that 4k mark and registering knock events if we pushed it past.

Just in case I have attached the Log as well as the bin from this particular log.
Any information on the commodore behavior is greatly appreciated, if you need more information let me know.

Many thanks in advance,

EDIT: a snapshot of the dashboard at around 4200rpm where the knock retard kicks in full force

Dashboard snapshot.jpg