Ram air with MAP?

[Johnny]

Given that standard atmospheric pressure is 29.92inHg. and given also that
you would be at WOT, without the ram air, you might see 28inHg. manifold
pressure, 29inHg. if you had a really big air door and not much restriction
in filter etc. If you did get an additional 1psi, or really, 2inHg.
increase in manifold pressure, you would be seeing 30inHg. total. Most
stock non turbo MAP sensors are 1 bar sensors, meaning that they go up to 1
atmosphere or 14.7psi or 29.92inHg. They may or may not be able to respond
to anything over that. You could go to a 2 bar sensor, but I don't think
the extra 2inHg. is going to make that much difference, especially at WOT
full power. It might, but you will just have to test it out. The other
question would be what will your ECU do with the possibly off the scale
output from the 2 bar sensor.

As far as the IAT goes, it shouldn't make any difference that the cooler
air is the result of "fresh" air intake. It will simply report the temp and
the ECU will compensate accordingly. The same as if you were driving on a
colder day. IMO, the colder the better.

This does raise another question though, and it may have already been
discussed here; what happens when you chill the fuel? There isn't a sensor
for that on any of the systems I have played with. Theoretically, if you
get the fuel way down there like, -50 or so, there would have to be more
molecules per squirt than there would be at +80, is it not enough to make a
difference, or is there some self equalizing factor there that I am over
looking?

-j-

----------
> From: Frank/G.speed <fmlin at ccnet3.ccnet.com>
> To: diy <diy_efi at coulomb.eng.ohio-state.edu>
> Subject: Ram air with MAP?
> Date: Saturday, March 01, 1997 12:39 PM
> 
> If I ram air an engine with MAP sensor, will the change in pressure
> and mess up the MAP output?  I know that there won't be any kind of
> pressure until high speed (maybe 0.5 psi at 100 MPH or more?)...  but
> assume I get 1 psi @ 130 MPH.
> 
> On ram air (or cold air) systems, the IAT sensor will pick up the
> cooler air and modifiy fuel accordingly right?  Does everyone
> here agree with this rule of thumb - every 11 F degree or reduction
> in IAT you gain 1% of HP?
> 
> -- 
> Frank M. Lin	  | G.speed - Z.Speed Trust HKS DC-Sports Razo/Carmate Soei
> fmlin at ccnet.com   | Web page - http://www.ccnet.com/~fmlin/gspeed.html
> EG2, 2:0x @ Sears | Info sheet - "finger fmlin at ccnet.com > gspeed.info"
> 
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