Fooling the MAP sensor - Diesel Forum

wwalkersd · 12-26-2006, 09:43 PM

I've got either a very dumb or very esoteric question regarding "fooling" the Manifold Air Pressure sensor (with a Boost Annihilator or the like) so you can run higher boost without causing de-fueling due to overboost.

I'm under the impression that the MAP sensor is used, at least in part, to determine how much fuel to feed to the engine. Is that wrong? If it's not, then why aren't you under-fueling at boost levels that are higher than what you're showing to the MAP sensor? It seems to me like the system is running open-loop instead of closed-loop at that point.

strokin_early_99 · 12-26-2006, 10:07 PM

The map sensor is designed as a feedback device to adjust fuel to keep boost within the Ford design parameters. If it sees 22psi(my regulator is set at 22psi) it thinks it is doing its job perfectly and maintains the fuel at that flow rate. If it sees over boost(24psi in my truck) it defuels around 20%(so I have been told). After boost drops into normal range it will reset in about 30seconds or less on my truck.

The old way to bypass the MAP from throwing a code is to ground out the green wire on the map. That is no longer used as far as I know.

I never liked the blow-off valves. To me, it defeated the purpose of building higher boost if it was going to be blown off under the hood.

Anywho, this is my "redneck reckoning" of how it works,

Keep Strokin'

spdiesel · 12-26-2006, 10:55 PM

this is correct. our overboost eliminator will solve this issue with out any side-effects...30 second install.

http://www.spdiesel.com

then click on other products.

or alternatively you can find it easily on ebay.

Tough_Guy · 12-26-2006, 11:21 PM

Nice...Thanks SP.

I just bought the overboost eliminator doo hicky....

This site is like heroin for a junkie... [img]/ubbthreads/images/graemlins/biggrin.gif[/img]

Chris

DZLJIM · 12-27-2006, 05:58 AM

If it's only a problem with the '99-up trucks, then why not run a '94-'97 map sensor?
Just curious...

Boonman · 12-27-2006, 08:05 AM

It has to do with the programming of the '99-up PCM's I believe. Self protecting in overboosted conditions. Kind of like it cutting back on a 1211 code as well. For overboost, I use a 20PSI non-adjustable regulator on the MAP line. Works beautifully. I check with my Banks 6 gun, because that reads the PSI that the MAP sees. It has NEVER gone over 20#'s. I run right around 30 PSI max. I also used to run SPDiesel's EBP "fooler". Although, it never worked. I always got the backpressure code. Mabe I got a bad one? I dunno. I now run the EBP sensor in line with the MAP line feeding my regulator, so it basically sees boost pressure. And not drive pressure. It is that way because I have my drive pressure guage plumbed into the spot for the EBP.