legacycentral bbs

azn2nr wrote:

BAC5.2 wrote:That's my main concern: Having to re-map EVERY MAF voltage.

wont you have to do that if you use something like 800cc injectors??? whats a bigger maf? if anyting it makes it easier to tune.

No, almost every engine management out there can scale injectors.

For example, the UTEC for the WRX scales injectors by augmenting the injector pulse width. You punch in that stock is, say, 350cc's, and now you are running 700cc injectors, and it scales the pulse width to the injectors, and determines the new firing time required to flow the proper fuel for X MAF voltage.

Now, when you start adding boost and things like that, you have fuel clearance to be able to max out the maf.

The problem, is that with a MAF that flows more air, the ECU sees a lower voltage at the same air flow as stock, so it leans out based on this signal (thinking the engine is getting less air than it is). So to correct this, you need to program how much air is flowing at X voltage, and how much fuel to supply at that voltage, all for that particular MAF.

If you flow 200g of air at 5 volts on the stock MAF, and plug in a new maf that flows 400g of air at 5 volts, what do you think the car is going to do? Every voltage is going to register 1/2 of the actual air flowing, and the ECU is going to fuel for 1/2 of the acutal air. So at the rail of 5 volts on the new maf, your only going to be throwing enough fuel for the old MAF, and that'd be dangerously lean.

That's kind of how it works. It's 3:38 in the morning, and I haven't slept much in the past few days.

BAC5.2 wrote: I'd use a GM 3" MAF. They can be found in almost ANY GM vehicle, and I'd imagine they are all the same or similar. I got one out of a Lumina with the 3800 Series II engine (I think that was it).

DSM guys use these with GREAT success.

Interesting. That sounds like a widely-used sensor. Any idea of its range?

Before I go junkyard hunting or to the auto parts store looking for one of these... any GM vehicle = non-Saturns, at the very least.. I know they are MAP-based. You mentioned a Chevy Lumina van - any idea what model year range I could request a MAF sensor from the parts store with?

Edit: Rather pricey, but 900-1000CFM!
http://www.jegs.com/cgi-bin/ncommerce3/ ... rmenbr=361

I'm looking for a cheaper solution, and we don't need 900 CFM of range

And Nico - the airflow sensor is a heated wire in the intake tubing directly after the stock airbox, not in the throttle body. Pre-turbo, not post-turbo.

This one was from like a 98 or something.

They were also used in Camaro's, Vettes, basically most of the larger engined GM's. The van's used them too, I think.

As far as range, I know lots of DSM's make 500+ at the wheels with this sensor, so I'd imagine at least 600cfm?

Lots of them also run blow through style, with the turbo pre throttle body but post turbo.

Wouldn't it be just as difficult (or easy?) to convert to MAP based fueling, and ditch the hotwire all together?

Not sure yet. Could go either way, depends on which would turn out to be more feasible for a quick and accurate closed-loop wideband O2 autotuner. Sounds as though MAP-based fueling would require more calculations. But if I can't get a good MAF sensor for a reasonable price then it would be worth it. I'd rather add value to the product with my chip firmware, instead of with the addition of an expensive part.

So the GM sensor is the one I keep finding, that the LS1 motor uses? 900cfm... whew! Maybe there's a guide somewhere on the 'net to show me how to identify and scavenge one from a junkyard. $150 for a sensor is a bit much. If I can source 'em cheap from junkyards, though...

Somehow I get the feeling the WRX maf will not be an easy swap. The housing is connected to the airbox, whith uses the undermanifold design, and the sensor is made by Denso, so there's no telling if it will swap right in place of the Hitachi. I think you'd be better off trying to use a JECS sensor. a 300ZX sensor would be perfect methinks.

Hmm... those be good points, y'aar.

300ZX sensor. Thats a new search. Thanks!

could i have max out my maf, if i put on a bigger turbo an removed the factory air box and the middle piece

uhh. has anything new become of this yet??

^^ yes i am with you.

what car should i take the maf from that will be good for 400hp?

LoL. i think like they were saying in another thread, the GM MAF sensors would work pretty good. probably the ones with the V8's since they usually put out a lot of power stock.