HHTurboVert

Here is a question of all of you electrical inclined rotary guru's,
I stopped by a local rx7 shop and was checking out this done up turbo vert.
When I popped this guys hood, I noticed that he had a 5 series AFM installed on this 88 vert with an S4 13b-t. I took a closer look and found that he had made a simple electrical adaptor that made the 5 series AFM plug and play. How is this possible? I looked into this before and was told that it couldn't be done because the resistances are different between the 4 and 5 series AFM's?
I offered to buy the adaptor off of him, or to pay him to make me one, but he declined saying that the design was his secret. Did any of you know this could be done? If so, could somebody explain how to do it or post some sort of diagram. I know just about every S4 turbo owner on this site with a stock AFM would rather use the 5 series AFM since it is much less restrictive. I bet changing the AFM alone would be good for a good amount of extra ponies!
Ok, this is the part where you guys impress me with your infinite knowledge about the workings of the rotary engine.

ilike2eatricers

If you searched you would have found this thread about the topic.
https://www.rx7club.com/showthread.p...wiring+diagram

and this wiring diagram inside that thread *note I do not know if this works or not so read the thread yourself and find out*

SonicRaT

iTrader: (6)

Uh... the S5 AFM is MORE restrictive than the s4's. How is an open square tube more restrictive than a 2" cone ALWAYS in the path of the air?

HHTurboVert

Sorry for not searching. Really!
So are you saying that there really is no point in doing this? I always though that the flapper on the S4's was alot more restrictive than the S5 design.

WAYNE88N/A

But if the S5 block made more horsies, then it must have been able to ingest more air, right? Which means the S5 AFM is in theory able to pass more air...Whereabouts in Texas are you hiding, Rat?

SonicRaT

iTrader: (6)

I'll be in Houston soon! Just because it ingests more air doesn't mean it flows more, I mean you can see people turning the boost up on a s4 and getting more power. Quite simply, the S4 flows better, because once it's full open, it's a nice clear path (relatively), where'as the S5 always has that damn cone in the way all the time.

WAYNE88N/A

You'd think someone would have performed flow tests on them by now for comparison...

Houston's pretty big- what part? How long?

SonicRaT

iTrader: (6)

Yeah, they should've...

And no damn idea, probably be there for about 5 months, fiance's got a job at Air Liquie(sp?) or something like that, so wherever they stick us!

WAYNE88N/A

Air Liquie- is that an airline? Something aircraft related? That's about as far south as I go into Houston- Bush Intercontinental Airport is in the extreme northern part...I don't speak the language to go much further south than that, lol...

I've noticed when watching the ECU inputs that the AFM gets nowhere close to full open on my car (just intake/ exhaust mods), which is a good thing. A little room to play with when the porting comes

SonicRaT

iTrader: (6)

I hit 100% with the turbo on the car, lol.

I'm afraid to go to Houston, I can't speak spanish! It's some sort of Chemical Engineering job, what she does I have no idea. Oh, and I forgot a Q, it's Air Liquide, I guess they're big into gases (hydrogen/etc), I have no idea. She tries to tell me and I look at her like she looks at me when I explain the rotary engine.

J-Rat

iTrader: (2)

Its Air Liquide.. Pronounced Air Likeede

They supply LOX and other gasses to most aviation companies.

WAYNE88N/A

Lol, yeah a good woman that gets into cars like guys do is a rare find indeed...

I don't know exactly where that place is, but PM me if you need to figure out where you want to rent/ buy a house or whatever. Born and raised here, so I know the "town" pretty well...

Hope you like humidity

WAYNE88N/A

Never heard of them, and I deal with probably 50 different aircraft vendors a day it seems...

Of course, civilian aircraft use gaseous O2 and O2 generators. Haven't played with the LOX since my Navy days on the A-6's...

SonicRaT

iTrader: (6)

I seem to have a habit of getting you old-timers off-topic!

J-Rat

iTrader: (2)

Dunno what to tell ya skippy! They supply most of our goodies.. LOX, GOX, LIN, etc..

vice

i would like an s5 afm. not because it flows more air, but because i hate the look of the flaper type afms. everytime i look into my enginebay and see the monster i just think "ghetto azz old skool shyt" i like my engine bay to be kleen.

SonicRaT

iTrader: (6)

Go standalone and get rid of ALL of that old school shiat!

rotarygod

iTrader: (1)

That's the best advice right there!

You don't need to speak spanish to live in Houston. I don't. You only need to speak spanish to tell your lawn guys how you want the yard done!

NZConvertible

I don't remember anyone saying it couldn't be done, but I'll say that it shouldn't be done unless you have some way of verifying that they mixtures aren't adversely affected. I'm surprised anyone would be so keen to perform a mod that will have a totally unknown effect on mixtures due to the differences between the two AFM's.

So secret that it's been posted on this sites dozens of times...

That's where you'd be very, very wrong. For starters the 60dia intake of the S5 AFM is 10% smaller in area than the 63x50 intake of the S4 one. And a fully open flap represents no flow restriction compared to the S5's sliding cone which is always obstructing airflow.

Actually this has nothing to do with workings of the rotary engine. Both flap and cone AFM's were fitted to millions of EFI piston engines until hot-wire AFM's became the norm.

Correct.

Why? Just curious.

Dude, that's terrible logic!

Ottoman

any way to convert to hot wire? or is that just WAY to off the wall for our poor little S4 ecu's?

a nice big 3.5" LS1 maf would be a nice mod

in the DSM world, we convert the car to LS1 maf and put it in the intercooler pipe before the TB, making it a blowthrough setup... works great and much less restriction

too bad we can't do it for the rexy

pengarufoo

You guys seem to be imagining that suddenly once the flap is 100% open the spring force disappears making it no restriction? Obviously this is not true, lose the airflow and the door closes, the flow has to keep the door open - not free.

Has anyone here compared the spring force of the s5 vs s4?

It would not surprise me if the s5 posed less restriction than s4, but it is true that the s4 is easier to tweak and probably has a broader range it can be used to measure. Operating within the s5 limits though, my bet is on the s5 being less restrictive.

did santiago ever get results up?

NZConvertible

You're right, I should've said less restriction. Plus if the flap (or cone) is fully open, you have other things to worry about...

It would surpise me a lot. Even if both AFM's were completely hollow inside, you still can't ignore this significant difference in inlet area. But if someone posts some meaningful comparison data obtained in a reasonably scientific manner that proves otherwise I'll stand corrected.

Tofuball

You raise a very good set of points.

And one thing I _THINK_ (warning: opinion) is that the S5 AFM would cause signifigantly less turbulence, and probably gets the air up to a much higher velocity. (Thus, though the area is less, it will still probably encourage the flow of more air)

Anyway, given only the decided lack of actual scientific information on the topic, I'd still put my bet on the S5 to flow better.


Either one's restriction shouldnt be a major factor untill you're producing enough power to want to go standalone anyway.

I will mesure the total 'final' airflow of both (I havfe both sitting around, and a perfect testing bench) should anyone actually care enough for me to try it.

NZConvertible

Why? There's nothing in the S4 AFM that would cause any more turbulence than the S5 one. Being square rather than round has no effect on turbulence, if that's what you're thinking.

That's fundementally flawed thinking. Pressure drop (a very good indicator of restriction) increases to the square of velocity. Double the velocity = quadruple the pressure drop. Or in this case, for the same airflow, 10% higher velocity = 21% greater pressure drop. You have to suck harder to get the same airflow through a smaller area. This is a basic rule of fluids. Higher velocity does not encourage greater airflow, it does the exact opposite.

An area measurement is quite scientific...

Please do. What are you going to use to test them?

Tofuball

Interesting, perhaps I was wrong (The reason I put "Warning, opinion" on it) :P

Your acutual numbers and formula > my random guesswork and hatred of squares


This is my plan for testing it:

I have my car currently set up to inject a very exact amount of fuel at a given speed. Even opening up a vac tube part way will change my final AFR as detected by the O2 sensor by making it run just that much leaner.

If I swap on either AFM, then mesure how much leaner or richer I'm running across a full map, making notes of the VE (Volumetric Efficiency) Table, I can tell if one is letting in more air at a given RPM.

My ECU will then try to compensate by correcting the AFR using the wideband output, but it will record how much it is correcting by and where, giving me a nice comparitive graph.

Needless to say, several back to back runs will be nessisary given changing conditions, and they must all be done in a relitively short time of eachother. . . so it will probably take me a good two hours to collect the data.

Currently the S5 MAF is on the car and hooked up to nothing (My ECU does not use the MAF, it's just on there to hold the cone in place for right now). So I will do some logging runs with that on first, then swap on this S4 one I have sitting around, then I will do some more logging runs, then swap the S5 MAF back on to test for consistency.

Does that test sound appropriate?