Fooling the MAP

nursecosmo · **Posted:** Sun Oct 07, 2007 12:40 am

check out this link. It might be an alternative to a chip tune. :twisted:

DarbyWalters · **Posted:** Sun Oct 07, 2007 2:04 am

and the link is.....drum roll....

nursecosmo · **Posted:** Mon Oct 08, 2007 8:29 am

Whoops.
http://flashoffroad.com/Diesel/boost_fo ... ooler.html
:oops:

gmctd · **Posted:** Mon Oct 08, 2007 10:49 am

Note the (edited) quote -

"This is applicable only to (actually 1994) 1996 to 2003 trucks with the standard 6.5L TD engine. This is not applicable to the 2004 (DMAX) models due to it's (sic) emissions package."

Same goes here - that is a primitive method which offsets MAP output, which skews ECU pressure scale - it was a 'freeware' experiment from the DieselPage back around the turn of the century and has been widely copied, as it is effective on the primitive '94-'03 6.5 EFI system, which has a max oem 7.5psi Boost limit and no charge-air cooler
It does not effect an increase in fuel rate - only increases the available Boost range.

Note, and just FYI - this is where the odd notion of 'you can turn up the Boost, but if you don't add fuel, you won't get any power' comes from - read it all over the Diesel forums - not even true - fuel makes Boost, not the other way around.

The 6.5 system has no charge-air cooler, so max Boost was limited to maintain intake air temps within a safe range, producing ECT's and EGT's within a safe range for that configuration.
Stock 6.5 oem full-throttle fuel rate will produce 20psi Boost, though PCM limits that to only 7.5psi - remove the limit, and Boost will match the fuel rate.

The simple proof of this, for those with adjustable wastegate actuators, is , note the Boost pressure with engine idling, which is 0psi, then pop the hood, crank down on the Boost control spring until the control rod is jammed against the stop, which is absolute max Boost position, while noting how much Boost increases - zip, nada, wala, zero, nil, squat - the Boost control spring is cranked all the way to max Boost position, but no increase in Boost Pressure because fuel rate is minimal at idle - no fuel = no Boost - crank up the fuel and Boost will follow suit.

nursecosmo · **Posted:** Tue Oct 09, 2007 9:16 am

My thought about this was to fool the map in the opposite direction. If the engine is putting out ten# of boost @ say 2000 rpm but you fool the map into thinking that it is only putting out 5#s wont the ecm add fuel to try to bring the level up to it thinks it should be according to the fuel map in the programing? when more fuel is added more boost is generated which equals more horseys.

gmctd · **Posted:** Tue Oct 09, 2007 10:00 am

Good thought, but - this is a modern engine with a state-of-the-art intelligent emissions system (oxymoron!) - to prevent black smoke, ECM reduces fuel when Boost is less than expected - prolly also reduces EGR, butcha still got less power - plus, you prolly will get a CEL with DTC

That is a big problem with the GM 6.5 system - PCM does not reduce fuel as Boost fails in that primitive system - resultant complaint is always 'black smoke and no power' or 'no power and black smoke', not even good in an increasingly forced emissions-conscious society.

Even in the even-primitiver Dodge system, the AFC lowered fuel rates if Boost dropped.

Anyway, don't know how you'd handle that, as the VVT\VNT Garrett is prolly on PWM control, nothing like a mechanical wastegate system.

Fooling the MAP

Who is online