I live very near Road Atlanta and various self proclaimed spec miata experts. One was telling me that I sholdn't upgrade to the bigger rx maf because, in his opinion, drivability suffered (in favor of a few extra hp). I know several of you guys run the rx maf, are there any issues to speak of?

 

that guy must not know that you can adjust the AFM to run perfectly. I have used mine for 4 years now and it only took me 5 minutes to get it dialed in for a perfect idle. Then I took it out on the road and adjusted it a little more for what felt best to my butt dyno. SPEC miata experts dont use turbo's they use stock engines and so for them it might not be worth it, for us it is

 

He told me he knew to adjust it... But I thought the same thing you wrote.

Thanks

 

I haven't noticed much difference between the two. I just went back to the OEM AFM after years with the rx7 unit. I can handle the 305s perfectly fine without the larger unit. I'll get back to a dyno one of these days but untill then I don't see any gains, and it makes no difference in AFR curve.

 

Ben, assuming my clutch install goes off without a hitch, I'll be throwing in my 305's and tuning later this week. I'll be able to hot swap both the stock AFM and the RX7 for back to back to back to back runs so get some real dyno-data for all of us. Assuming flat A/F's I can't see how the RX7 would be any worse... but we may find out is also doesn't provide a significant gain either.

Brain, are you still recommending 4clicks looser w/RX7 and 305's? Then w/stock AFM, should I just adjust the idle screw a little to get me to 14.7?

 

i went 3-4 clicks softer with the RX7, i can actually go back out and look at it tomorrow and count and Ijust backed the idle screw back one complete turn on an unmolested oem afm. but if you're on a dyno, then you should be able to tune on that while idling.

 

I still think since the RX7 AFM is flowing more CFM that youll see gains in the upper rpms. It might not be much ( 10whp) but thats enough for me to actually use it. At low boost it might not matter as much. But when I am running 17psi and the turbo can pull more air from the RX7 unit than the stock unit I expect that there would be a gain there. I am looking forward to Sam's dyno day so we can put this to rest once and for all

 

Randy Stocker has shown the RX7 AFM is good for about 5hp (NA) over 6K (I think). Not sure what that would mean with a turbo.

As for the original question ... what sort of drivability issues was your spec guru referring too? I've got one on my car, it didn't make things better or worse.

 

Next time I'm on the dyno I'll be doing the same. However I think at my boost level (12psi) I might not see much in gains. CFMs are most likely the key, however if the oem unit doesn't provide as much as restriction as everyone thinks, then it may show no gains, dunno. But untill then, I don't feel like putting the Rx7 unit back on.

Jayc72, you are correct, I've seen the plots. However, it lost major mid range power and peak torque. And I think it made up for it in peak HP by the effects on the fuel curve.

 

Bumping an old thread.. ^^ever get those results on the dyno braineack? I just installed a Greddy (I know) and my AFRs are way lean (16-18). I've got the RX7 AFM, thinking about swapping in the stock unit today just to see what happens.

 

unless you have some bogger injectors it wont help you. The major benefit of this is you can effectivly control larger injectors and have more air flow. If you did this with stock injectors you would be leaner still than stock.