LPG VP V8 - anyone have a spark table?

Circlotron · Post by **Circlotron** » Thu Mar 29, 2012 10:52 pm

My 5L VP had it's LPG conversion done in 1993 and they changed the spark table to presumably something more suitable. I am thinking two things - first that LPG composition might have changed somewhat since then. Second, since 808 hacking must have been in it's infancy there are probably more refined spark tables that have been done since then. Does anyone have one? My eprom data is attached for reference. MEMCAL ID says $5D VLV8 Manual OR VNV8 Automatic/Manual.

Circlotron · Post by **Circlotron** » Mon Jan 13, 2014 7:29 pm

Bump.

Post by **delcowizzid** » Mon Jan 13, 2014 8:40 pm

jesus 38 degrees total timing.generally lpg needs timing low in the rpm and less than stock up top

VX L67 Getrag · Post by **VX L67 Getrag** » Mon Jan 13, 2014 9:27 pm

Seeing GM never released a V8 factory LPG I copied the differences across from same released model V6 on the identical lines & cross interpolated!

Circlotron · Post by **Circlotron** » Mon Jan 13, 2014 9:32 pm

Yeah, it was warm today. Was doing about 80kph and had to scoot through an amber light so floored it and it dropped to second to 103kph and pinged quite a bit. Normally drive like grandpa so doesn't happen. Motor does feel a little gritty and harsh and that says too much advance to me. Ignition map was changed when gas conversion was done in 1993.

Circlotron · Post by **Circlotron** » Mon Jan 13, 2014 9:36 pm

VX L67 Getrag wrote:Seeing GM never released a V8 factory LPG I copied the differences across from same released model V6 on the identical lines & cross interpolated!

Okay...
I know what interpolated means. What do you mean by "cross interpolated"?
Do you mean for every data point make the new V8 LPG point halfway between the V8 petrol point and the V6 LPG point?

Circlotron · Post by **Circlotron** » Mon Jan 13, 2014 11:06 pm

Red is the curve currently in my car.
Blue is normal VP V8 BBPA petrol curve.
Yellow is VP V6 BBMM LPG curve.

These are all from the "100" MAP column so wide open throttle. (edit - incorrectly said "20")
I wonder how it actually managed to run all these years.

Post by **VL400** » Mon Jan 13, 2014 11:17 pm

I think VXgetrag did something along the lines of V8 LPG = current V8 petrol + (V6 Gas - V6 Petrol) for each cell in the spark table.

100kPa map column is generally WOT in most TP defs.

Circlotron · Post by **Circlotron** » Tue Jan 14, 2014 6:55 am

Aha! Getting all excited now!

VX L67 Getrag · Post by **VX L67 Getrag** » Tue Jan 14, 2014 8:05 am

Sorry yeah what VL400 said, use the stock petrol v6 timing compared to stock v6 LPG timing & copy the differences to the v8 & sort of smooth between.

LPG VP V8 - anyone have a spark table?

LPG VP V8 - anyone have a spark table?

Re: LPG VP V8 - anyone have a spark table?

Re: LPG VP V8 - anyone have a spark table?

Re: LPG VP V8 - anyone have a spark table?

Re: LPG VP V8 - anyone have a spark table?

Re: LPG VP V8 - anyone have a spark table?

Re: LPG VP V8 - anyone have a spark table?

Re: LPG VP V8 - anyone have a spark table?

Re: LPG VP V8 - anyone have a spark table?

Re: LPG VP V8 - anyone have a spark table?