ej25 throttle body on ej22t?

[Sir Yach-o]

I hate the MAF with a passion, and I'd love to get rid of it.

So, where did it go on the '99's+?

I think that they have airflow sensors on the TB itself, but I'm not sure. Does anyone know if a swap can be accomplished? Or would whatever sensor differences involved in the swap not be compatible with our ECU's.

-mike

[DLC]

2000+ uses a MAP sensor that's nearly on top of the throttle body, and uses some different logic and methods to get airflow readings. RS-T owners had to trick this, or the ECU, into letting them run more than 3-5PSI, as it got confused somehow.

It's not at all compatible with our ECUs, but might be with replacement standalone unit.

Dave

[Sir Yach-o]

Dah well, looks like we're stuck with the MAF then.



-mike

[Legacy777]

What do you have against the MAF's?

They are a better measuring tool. Plus.....on turbo cars....you pretty much have to have them.

Turbo cars essentially have both a MAF & MAP. The MAP is essentially the boost solenoid circuit.

[Sir Yach-o]

right,

I just hate working around them from a custom intake standpoint.
I've also been reading about constrictive to airflow they can be on my friend's Trans Am forum for theier cars.

Plus, i'm probably gonna blow it and it'll cost me $300 to replace.

-mike

[Sir Yach-o]

So what system are they using on the WRX?

I don't know anyone who's got one, so I've never really studied them.

[DLC]

The WRX uses both...

[Adambc5]

The stock MAF/MAS used on the early model Subarus (up to and including 1998) are actually quite good, and can flow a very healthy amount of air...much more than you are likely to ever injest.

The problems came on the '99 units, of which many were prone to failure, and eventually prompted a recall IIRC 9long after I replaced mine just after the first turbo kit we installed on my car).

MAF/MAS are far more accurit than MAP/speed density units, though far more likely to fail. They also represent a restriction in the intkae system, as the intake is forced to be a certain diamter in order for the sensor to operate properly (thus limiting tubro inducer diamter, intake pipe diamter, etc. On most of our subies, it won't matter much, as I doubt many of us will surpass the roughly 350-400 HP the stock MAF can read before it miscounts air. Howver on other cars (DSM's are a perfect example, Supras are anotehr), the stock MAF/MAS becomes a HUGE restriction, and all serious power contenders switch to a MAP based system, wich reacts instantaneously (as it is pressure driven not volume driven) and rarely fail. if they do happen to fail, MAP sensors are easy to come by, and very very inexpensive. The problem mainly lies in the fact that the conversion parts themselves are pricey, as it is a lot of R&D time figuring out the software side of things (hence a piece like the HKS VOC retails at around $1100.00). Other universal units like the LINK SFR are next to impossible to ge running, and require so much fiddling, they simply are not worth the effort...best to simply covnert to full MAP based standalone like an Electromotive, MOTEC, etc. if you ar that serious about it. It will be interesting to see if Turbo XS can adapt a UTEC for us Legacy folks...by bet is they can, and can do so quite easily, as the LEgacy ecu's are very similar (schematically) to early WRX units 'to '96 from what I ahve so far). Basically on a MAP based setu, you are using manifold pressure and IAT 9inlet air temperature) to allow the ecu how much fuel it needs to supply. A bit crude when compared to a volume based system like the MAF/MAS, but, so long as you ahve a sensor that can read a sufficient amount of positive manifold pressure (assuming a turbo car), the rest is cream cheese. bet part is that unlike fitting a larger MAF/MAS (which requires reprogramming the ecu to recognize the larger dia,ter anmd different calibrations), all you nee to do should you want to run more bosot than your MAp sensor can read is fit the next size up sensor (they go one bar, two bar, etc.)...four bar is the highest I have seen so far, from Motec.

Since we are one of their distributors, I'll trya nd work with them over the next few months and see what we can come up with...it would be nice to ahve a sub $1000 ecu that can program ignition, fuel and boost with something as simple as a Palm, and has the ability to convert you to full MAP based engine control.

Adam
www.z1auto.com

[Sir Yach-o]

Thanks for the write-up, Adam!
Very informative.

This leads me to another issue I've got questions about... Since the MAP systems check pressure AFTER the turbo, it would allow you to let your BOV release to atmo without any adverse fuel effects, right? For example, on my MAF setup with BOV to atmo, I get crappy fuel economy because I'm no doubt running rich since the MAF has measured air that the engine's not using (escaping to atmo through BOV). With a MAP, I could avoid this.
Is this thinking correct?
(I might just open another thread adressing the BOV to atmo issue)

-mike

[Aaron's ej22t]

sir yacho, yes you are right. map based cars can run external bov w/o any problems.

[mile hi]

The MAF sensors on our cars are very reliable and will flow a considerably more air than is needed for these engines in almost all cases. The bad news did come with the '99 units and they are not a MAF sensor they are a MAP sensor in a MAF case and were a lot of trouble as the pressure sensing unit was directly exposed to a sample of air and were a very poor design. The present MAP sensors while being more somewhat more reliable than the '99s are really no better than the MAF sensor. Getting a MAF type ECU to except the signal from a MAP sensor can be done but it is not practical to do so because the MAP sensor output is close to being linear and the MAF is exponential.
AL(CO)