Barometric timing correction?

This is a forum for discussing the development and testing of alpha MS2/Extra code. Documentation
(Runs on MS2 and Microsquirt)

Moderators: jsmcortina, muythaibxr

Token
Helpful MS/Extra'er
Posts: 71
Joined: Mon Nov 12, 2007 9:49 am
Location: Los Angeles

Re: Barometric timing correction?

Post by Token »

If this is done soon the 4age will be ready to test it within a few months at most.
I'm an Alpha junkie!!

Old: MSII batch fuel, wasted spark. New: MS3x, sequential fuel, wasted spark, VVTi
Thanks to all who contributed to MSextra and MS3 code and thanks to DIY Tuning!
Philip Lochner
Super MS/Extra'er
Posts: 1004
Joined: Thu Feb 16, 2006 6:18 am
Location: George, South Africa

Re: Barometric timing correction?

Post by Philip Lochner »

muythaibxr wrote:It shouldn't be too hard to do an offset.

Ken
Does that mean it might be in a code release any time soon, Ken?
Kind regards
Philip
'74 Jensen Interceptor 440ci (EFI'ed with MS2 and wasted spark + GM 4L60e GPIO controlled - both on Extra FW)
Philip Lochner
Super MS/Extra'er
Posts: 1004
Joined: Thu Feb 16, 2006 6:18 am
Location: George, South Africa

Re: Barometric timing correction?

Post by Philip Lochner »

muythaibxr wrote:It shouldn't be too hard to do an offset.

Ken
Has this been done? If not will it be done? Please, with a cherry on top?

To me this is just as important as barometric correction for fuel. Every time I travel to lower altitudes my car starts pinging forcing me to stop, pull out the pc, and retard timing by about 3 - 4 degrees.
Kind regards
Philip
'74 Jensen Interceptor 440ci (EFI'ed with MS2 and wasted spark + GM 4L60e GPIO controlled - both on Extra FW)
.boB
Experienced MS/Extra'er
Posts: 217
Joined: Sat Nov 19, 2011 9:12 am

Re: Barometric timing correction?

Post by .boB »

I live at 6,400' ASL. I often drive down to 4,000' and up to 11,000'. I wanted to do the same thing. Fortunatly, it turned out to be pretty easy. I have the MapDaddy installed for real time barometric control of the fuel.

For timing, altitude doesn't really matter. The second sensor that measures barometric pressure won't help you with ignition, but is vital for fuel correction. For ignition, what really matters is cylinder pressure. Barometric pressure plays a major role in that, but is not the only factor. Cam timing, temperature, engine load, etc, are also important factors.

My engine is pretty radical. Lots of compression, huge cam, and a somewhat poor vacuum signal.

I set the basic timing map to be very conservative, and that seems to work pretty well. Both timing and fuel maps are alpha-N. Then I used a secondary ignition map to be MAP and RPM based. As the kPa goes down (increased vacuum), I get more timing. As the kPa goes up there is less (or no) timing advance. This way, I get vacuum advance during light throttle cruise at high altitudes, and vacuum "retard" under heavy loads and low altitude.
----------------------
.boB
LS6 Track Car
Mostly stock. Sort of.
MS3X- Built by DIY AT
Post Reply