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Manifold barometric/pressure compensation

Posted: Fri Feb 16, 2018 11:44 am
by fast944
On boost application, let say around 25 psi, is it better to use the compensation table or use the main map to reduce the timing advance and some one have some number in mind to start
Thanks
Alain

Re: Manifold barometric/pressure compensation

Posted: Fri Feb 16, 2018 12:52 pm
by stevieturbo
Entirely personal choice.

IMO, unless you have a reason to use TPS with MAP compensation, do not. It just makes things more complicated for no good reason.

Of course there will be those who say it makes it easier.

Re: Manifold barometric/pressure compensation

Posted: Fri Feb 16, 2018 1:11 pm
by fast944
No reasons, but right now I use TPS with MAP compensation, what will be your suggestion ?

Re: Manifold barometric/pressure compensation

Posted: Fri Feb 16, 2018 3:07 pm
by stevieturbo
Well as I said above...unless there is a good reason to use TPS vs MAP.....do not...which implies I would not and pretty much have never used that method unless I had no other choice. ( which was the case with the P8 when I first used it back in 2002 or so )

Re: Manifold barometric/pressure compensation

Posted: Fri Feb 16, 2018 3:18 pm
by fast944
No good reason, I start using DTA before P8, just bad habit ? do you have a basic map for fuel and timing to start with I am using a GM 3bar sensor, 3000 cc 4 cylinders Porsche, Garret ball bearing.
Thanks
Alain

Re: Manifold barometric/pressure compensation

Posted: Sat Feb 17, 2018 6:36 am
by stevieturbo
If it's working for you and you're happy with it, then probably no reason to change.

I just find it much easier with MAP vs RPM, and the numbers you see on those tables more closely resemble what is happening at the engine without even more compensations going on in the background to change them.

You can select the GM 3 bar from dropdown menus, and you'd need to sort your own tables for your engine, spec, injectors, crank/cam triggers etc etc.

Re: Manifold barometric/pressure compensation

Posted: Sat Feb 17, 2018 7:49 am
by fast944
Oups, no tables to look at :)
Alain

Re: Manifold barometric/pressure compensation

Posted: Thu May 31, 2018 5:10 pm
by iceman_n
thats a map that came to me today

i dont understand why to reduce fuel with map compensation (either cold - hot engine) and at the same time to add fuel using water compensations when engine is cold...

i am missing something here or its pointless ??

Re: Manifold barometric/pressure compensation

Posted: Fri Jun 01, 2018 3:05 am
by Alex DTA
If you're mapping using speed density, all MAP compensations should be zeroed. They make no sense.
However, it won't cause any problems, it's just flattens out the fuel map.

Water temp compensations were used before the start fueling was available, so this is probably just an old map.

There will always be conflicting compensations. If the engine is cold, it needs more fuel. MAP is irrelevant to temperature.
If the throttle is closed, it needs less fuel. Temperature is irrelevant manifold pressure (ish).
However, they all end up working together.

Re: Manifold barometric/pressure compensation

Posted: Fri Jun 01, 2018 3:16 am
by iceman_n
thanks Alex...i agree with you

thats why i ask about it...thats not an old map is the map that the car uses right now, it works ok but it is a bit odd the way the mapper do it