mapload multiplication

[Denmark]

Hi All.

Under engine setup,
there is "map(load)multiplication

and it says under the help text that its is enabled for engines running speed density, but i have always run with it disabled,
and have not had a problem with it,
If i turn it on, the reg fuel needs to be upped a fair bit, to get the car idling,

What does it do, and is it supposed to be enabled for speed density ?

Thanks,
Skassa

[GintsK]

Nothing wrong with your cars. But better is to switch multiplication ON.
In this case VE table represents VE against pressure in manifold after the throttle. As result all VE map becomes more flat values at small loads are close to WOT values.
Without multiplication VE table represent VE against atmosphere. VE table becomes sloppy, you lose resolution for tuning at small loads and handy shape of map.

Gints

[Denmark]

Okay , thanks

i have always wondered as the manual says to half the regfuel from the calculated number, but used the full scale from 15-220 with All the injector setup i have used, so this Will give me more reselution

i Will give it a go tomorrow evening, i just need to remove the exhaustmanifold again to weld t in the collecter, that's the thanks for using wrap :)

thanks,
skassa

[gunni]

your not really gaining resolution with having 15-220 and not using map multiplication.

With MM it would go

105%VE*(140kpa/100) = 1.05(req fuel) * 1.4 = 1.47 * req fuel

yours would similarly be
147%VE * req fuel = 1.47 * req fuel

Neither is really better. But it´s easier to predict with MM.

[GintsK]

Okay , thanks

i have always wondered as the manual says to half the regfuel from the calculated number, but used the full scale from 15-220 with All the injector setup i have used, so this Will give me more reselution

i Will give it a go tomorrow evening, i just need to remove the exhaustmanifold again to weld t in the collecter, that's the thanks for using wrap :)

thanks,
skassa

With multiplication instead of 15 something like 100-150 expected.

[Denmark]

Jep, this will also make mé able to lower the reg fuel to gain more resulution right, as i Will not need to go that High at full boost too

/skassa

[BigD]

105%VE*(140kpa/100) = 1.05(req fuel) * 1.4 = 1.47 * req fuel

Can someone please tell me how come it's kpa/100? I've read this elsewhere and tried it, seemed to work. But I didn't see this in the docs (in the development where the feature was first proposed it just said VE * load).

Thanks!

[gunni]

It´s just a way to get a multiplier referenced to KPA.

200 is twice 100 , where 100 is the baseline so all KPA values must be divided against the baseline 100kpa.

Anything could have been the baseline but this makes nice easy to understand mathematical sense.

[BigD]

It´s just a way to get a multiplier referenced to KPA.

200 is twice 100 , where 100 is the baseline so all KPA values must be divided against the baseline 100kpa.

Anything could have been the baseline but this makes nice easy to understand mathematical sense.

Thanks gunni! So it's basically just an arbitrary constant the VEMS (or MS?) developers used so the factor wasn't too large?

[GintsK]

Thanks gunni! So it's basically just an arbitrary constant the VEMS (or MS?) developers used so the factor wasn't too large?

Or too small. It gives handy shape of map. It is much easier to work with such map than with old school sloppy maps!

[BigD]

Or too small. It gives handy shape of map. It is much easier to work with such map than with old school sloppy maps!

Yeah I could definitely see that when I made the conversion. I just couldn't find any definitive word from VEMS that it's 100, just people saying it on the net. And I didn't know if this was MS specific, if they're just rounding for simplicity and it's actually a barometric factor (ie 99 or 101.3 or whatever it happens to be when the engine's off. Thanks guys.

[GintsK]

Sorry, what 100, 101.3 ...?

MAP multiplication works with actual MAP reading like this:
PW= ReqF*[VE/100]*[kPa/100]*GammaE+Additives

At low loads [kPa/100] value lowering final PW, at high loads - rises. As result VE table becomes flat.

It is not MS idea. It comes from bigger names.

[BigD]

Sorry all I'm saying is that I couldn't find proof that VEMS uses kpa/100 and not just kpa, or that it's always 100 and not, for example, the atm pressure before the engine starts or something. Since there's no documentation for VEMS, there was always the fear that this was either not applicable for VEMS or a rough approximation. Now I know. :)