how and what are the differances between maf and speed density and which is better for milage and power
thanks

 

S/D has 2 large diameter air hoses leading from the airbox to the throttle body; MAF has 1 hose with a bifurcated adaptor at the T/B end.
There's no real difference in speed or ecomnomy until you start making significant modifications. Then the MAF system wins out because of it's inherent flexibility.

 

MAF on '94+ 302's



also '95+ 351's, but I'm not sure on the 300 or 460.

Adrianspeeder

 

Weren't there variances in the EFI controls on the 302s based on AT vs. MT versions? The 300 went MAF in 96 although there is some debate as to whether the 95 CA models were MAF or S/D; the answer is probably that they were both.

AFAIK the 460 never went to MAF although I'm completely in the dark about the 97 F250/350.

 

In what I've read looking into the MAF conversion, SD utilizes bank firing of the injectors, which I understand to mean that all injectors fire at the same time regardless of what stroke the cyclinder is and with MAF they fire sequentially, meaning each injector only fires on the intake stroke.

At least that's what I've read, if this is the case then I would think you would at least see a bit better mileage.

Performance wise, the hot rod mail lists talk about SD potential being limited because of the way the computer uses tables based on set parameters and alteration of the system beyong 10% of the stock breathing ability can screw things up, where as MAF compensates for the actual air flow through the engine.

 

The bank type firing arangement fires to the left, and then the right side cylinders, so not quite all at once. I don't remember for sure but I thougt that the mass air trucks had the same setup.

As for overall performance, I tend to think that SD systems may require tuning earlier on in the modification process, but really at the point you are doing a lot of mods both require custom tuning regardless.

There are some 1st Gen Lightnings making very impressive numbers and they are still speed density setups.

 

That's what I meant by bank firing.

From what I've read in terms of the conversion, they fire sequentially, you either alter the stock harness to accomodate it or replace the harness.

Speed/density adjust mixture based on preset preset mixture maps according to throttle position and vacuum, you need to rewrite the maps for pretty much any mod.

Mass airflow systems adapt to actual conditions and are more or less infinitely variable.

Pretty much everyone with SD is usually advised to do the conversion for any serious mods.

The Lightnings put up decent numbers from the factory because maps were optimized at the factory, altering them after market is rather cost prohibitive compared to MAS ease of mods.