VEMS Community Forum

VEMS => Software => Topic started by: mads b (dk) on July 22, 2013, 04:58:40 PM

Title: lambda delay ?
Post by: mads b (dk) on July 22, 2013, 04:58:40 PM
Do vems have a feature like this ?

http://www.shoptalkforums.com/viewtopic.php?f=66&t=142706&p=1165015&hilit=veal#p1165015

Regards Mads
Title: Re: lambda delay ?
Post by: Denmark on July 22, 2013, 05:57:42 PM
What do you need it for?
Title: Re: lambda delay ?
Post by: mads b (dk) on July 22, 2013, 06:25:09 PM
Im not sure that i need it?

how do vems compensat for exhaust gasspeed 1000rpm vs 6000rpm ?

Regards Mads
Title: Re: lambda delay ?
Post by: Denmark on July 22, 2013, 07:48:02 PM
It dosent other then the delay engine cycles you tell it to,

I must say that its not something i would need to get a perfect running engine , but i also og the old School so i disable ego corection above 0.8bar and wot,
Above that i run openloop :)
Title: Re: lambda delay ?
Post by: Mads Lund on July 22, 2013, 08:04:27 PM
Hi Mads

I don't think it needs compensation, at 1000 rpm (500 ignitions/60 sek) = 8,3 ign/sec, pressure 0,4 kpa, expansion ~4x =1,6 * 0,5 l (cylinder volume = 6,7 liter exhaust /second

My primary tubes is 70cm ø40mm =0,9 l before the lambda = 0,135 sek from exhaust to lambda, with 0,120 sek between pulses

So not really an issue, your will anyway mean the feedback regulation over a number of engine cycles in order to have a stable reading. thus using a pid regulation loop.

Br Mads (from denmark) 
Title: Re: lambda delay ?
Post by: mads b (dk) on July 23, 2013, 06:16:45 AM
If you look at the megasquit lambda delay table you see that there is a big differense  30kpa vs 96kpa..... but what you all saying is that its not to worry about. :-)

Regards Mads
Title: Re: lambda delay ?
Post by: fphil on July 23, 2013, 08:40:41 PM
This is not easy to make a compensation when information is delayed. To compensate for a delay one can try to set a prediction filter (Kalman or whatever) on lambda measurement
But in this case, apart the fact that the timelag is not constant which makes the thing more complicated, the ego correction has to change the VE  table value in the case the engine does not run as it should, that is in an unpredicable case.
I guess that what is made is to put less weight on the ego correction when the delay increase.
Indeed this is a nice feature which can be added. Enough to have this weight as a function of RPM.
Is it not already the case but with only 2 values: 1 and 0?