Porting AFM (air flow meter)
 

Has anyone done this?
I know you can install the 86-88 RX7 AFM and you can tune it put rotating the flap arm, but I've heard many complaning that the engine runs too rich and fuel consumption has gone up.

I noticed that I can increase the entry/exit area of the BP AFM by about 6-7%. Basically that can represent to about 10-12% increase in airflow and maybe even more with an AFM adapter that has clean air flow lines. This mod will not affect the fuel consumption but it will increase power above 5800rpms.

OK, I ported and polished the AFM, eveything went smoothly, I was able to increase the area by 0.080"x 1.95"= 0.156"" (about 5%). The engine still runs fine without any problems as for performance gains it will be hard to say since I still haven't installed my cold air intake, I still use the stock air box.

i dont know if is gona make a big diff like the rx7 becose the size betwen both is big. the door inside the rx7 vaf is bigger then the stock one. i got a rx7 in mine and my idle is good, it play at little bit but is someting i can live with it :D

I know that the RX7 VAF is 0.5" bigger but you also need to look at the construction of it as well, all stock VAF (Protege and RX7) have a step that creates a pressure loss, therefore a reduction in airflow.

I eliminated those steps and also added some material to make it smooth on the exit of the VAF. I'm certain I gained about 8-12% in airflow.

ok, with that but if you plan to go for the RX7 AFM you would have to find a BP09 ecu for best results with the BP09 the redline is going to be 7500RPM and the RX7 AFM works real hard from 6200rpm up to redline.

I'm planning on having a 150whp by April 04. So far I have the heads ported, 3 angle valve job, regrinded cams, ported/polished and knife edged intake manifold. I just need to install the Genie headers, JUN adjustable cam gears, and the exhaust system and CAI and I'm ready.

On the dyno I'll be comparing my ported BP AFM with the RX7 AFM to see if there's any significant difference. I'll hit the dyno in April or May 04.

I think you are (waisting) money doing all that. if you had made your car turbo you would have more hp than 150whp and you could keep going up in hp easier than a normaly aspirated engine. but if you like the hard way I with you good luck.

Turbocharging the BP would of costed me a good $2000-3000Cdn more over prepping the engine for natural aspiration mode.

BTW installing and purchasing the DOHC BP engine in my 323 and prepping the engine so far has costed less than $1000Cdn.

Mike where do you live, i'm from repentigny just outside montreal

I live in Laval, maybe we can meet up one day.

Would be cool but i'm working on my car every loose time i have, but i may try if the car is finish by then to go with you on the dyno i'm wondering how much hp i'm going to it next summer. Are you on club protege quebec forum it's a great forum also. Where did you get your adjustable cam gear and how much did they cost?

I got my JUN cam gears from EBAY at $150US + shipping.

If you want a set of adjustable cam gears I can have some made from the shop that I deal with. Since you're turbocharged adj. cam gears is a must for better efficiency and more power.

I can have some made by using the stock gears, that's how the JUN cam gears are made. Let me show the cam gears to my shop and I'll take it from there. BTW I have two set of stock cam gears.

AFM, stock...
 

I (personal opinion) prefer using the stock AFM and play with the resistance of the door flap of the AFM. From factory is kind of rigid making it kind of slow to open up. By making it just a little bit easier to open I tend to get quicker acceleration. Just be careful not to make it to easy to open or else idling will be affected.

Re: AFM, stock...
 

The spring tension on my unit was pretty good. Not too much force was required to open it, similar amount of force like the KL Vaf.

Re: AFM, stock...
 

Haha, you don't realize how much of a misconception that is. You're running rich, and probably down on power. I just installed my RX7 airflow meter, and dyno tuned it. It was a little loose to start, but it turned out it liked it lean. The stock system is pretty good, so unless you've done a lot of mods, you're running way to rich and down on power.

It may seem like you have better throttle response because the fuel's always there when you need it, but your car is actually slower. When I first installed mine, it FELT like it was a bit faster. But it turned out, I was down 7hp over my stock AFM, because I was running too rich. WE leaned it out, and now we're up 2.5hp at peak, and 4hp at 7000rpm.