Bad2ndgen

I was wondering if anyone knows of a cost effective (cheap) way to get rid of the flapper style M.A.S., like a hotwire setup or changing it to a map sensor without going full stand alone???????

Roy James

Man, this has been reviewed and pondered on many times. And, there really isnt any way, that i can think of, that is any easier or cheaper than a stand alone. But i, too, would like to know the answer. I hear of people trying to use Mustang MAF bc they are bigger or some ****, but i dont think anyone has really suceeded with it due to the wireing is totally different.

Bad2ndgen

There is a company called pro-m that was willing to build me a hot wire setup w/ idel and w.o.t. fuel adjustments. They would also make it any dia. i wanted but they wanted like $700.

Bad2ndgen

Oh yeah, my car is a 88' T2 and I have a 62-1 turbo that i want to install, but the intake opening on it is 4" and it would be stupid to have it neck down to the stock flapper.

bcty

should be fine

Evil Aviator

Please do not forget that even if you do find a way to replace the AFM with a better one, you are still stuck with the old, slow, nasty, non-programmable stock computer.

Bad2ndgen

The reason I haven't gone with a stand alone is I want to do a three rotor in the near future and would hate to buy stand alone twice...What do you know about the E.M.S or Electromotive setups. If I could find something that was upgradable to a three rotor I might get it.

Evil Aviator

Any EMS which can run a 6-cylinder engine can run a 3-rotor. If you are concerned about emissions and want to run split timing, then the new Electromotive and Microtech units claim to do this, but so far there has been no proof. A separate ignition system is also another option.

If you are on a tight budget, then you can forget about the 3-rotor. Sorry.

Bad2ndgen

I am very aware of the costs associated with doing a three rotor conversion, I just dont want to spend money on things that will become obsolete when I do the swap....It will be about a year before I start this project and I want to enjoy my two rotor without spending too much more than I already have. I was under the impression that AEM has discontinued the EMS race version untill a later date, so that idea is out for now. I talked to Ray Lockhead last weekend and he said that the Electromotive Tec3 would be upgradable from two to three rotors but I didn't get to talk to him at lenght about the details. Anyway back to the topic of this thread Im still looking for a (cheap) fix for my M.A.S. My current motor will be going into an R100 if I can find one, as soon as I do I will start the 3rotor project. If you want to know Im not full of **** just check out my car at www.kennewickimports.vista.com

rx7_ragtop

You could get a Haltech now... it would work with the 3-rotor. You could then add a second IGNITION ONLY computer to run the trailiing. (Haltech also makes one of those... not too expensive.) Just a thought.

Brad

Bad2ndgen

do you have more info on the haltech setup? like what extra parts i would need and how would this work on a three rotor?

DaleClark

iTrader: (55)

One thing I'm fixin' to experiment with is moving the AFM to the intercooler piping. It's much less of a restriction than before the turbo, and it's a really popular mod in Japan - there are countless FC's making 400-500 hp with the stock AFM in the IC piping - gotta be something to it .

You can upgrade to the '89-91 airflow meter - all you need is the airflow meter and the plug. I put it on my '88 Turbo and had NO problems - it started and ran just fine, made great power, you name it, with no tuning to the AFM signal or anything.

I really wish there was a "good" AFM solution for the RX-7. AFM's have a big advantage in that they calculate the volume of air directly. With a MAP based system, it estimates air volume by manifold pressure, throttle position, and RPM, with a set volumetric efficiency for the motor. When you alter the motor's volumetric efficiency, the whole map goes outta wack. That's why the FD guys have much trouble when upgrading their cars and need a computer early in the game. Same goes for a Haltech - you have to redo the maps when you make changes to the VE of the car, although it isn't as radical, since you're usually starting with a free-flowing system, not a choked-up factory system.

Anyhow, some food for thought.

Dale

rx7_ragtop

What about adapting a Mustang hot-wire AFM? Just a thought...

Brad

DaleClark

iTrader: (55)

The AFM's output would have to be tailored for what the ECU expects, which is a certain voltage that correlates with a certain airflow. This may not even be possible, since the way a sliding cone or flapper door reacts to airflow is different than a hotwire. I know of many people who have tried, but none to my knowledge have been successful.

Regardless, I think the '89-91 AFM isn't as bad as one would think - going back to my example of the many Japanese cars with the AFM in the intercooler piping.

Dale

Bad2ndgen

thanks for the info.....do you know what it takes to move the afm to the piping, I heared it takes some kind of modification. Do you know anything about this?

DaleClark

iTrader: (55)

Really, all you would need is some silicon reducers to clamp it into the piping and probably extending the wire - that's it. I plan on experimenting with it soon, if I can ever get the damn car in one piece again...

Dale

David88vert

It's not easy. Yes, it's doable, but for the effort and cost of doing it, you are better off to get a MegaSquirt and go with a MAP. If you want to try the Mustang MAF, there is a lot of documentation on it, and I have a new Mustang MAF here that I was experimenting with.

The Megasquirt just made it not worth finishing, because you get a standalone fuel computer.

rx7_ragtop

What documentation? I'm very interested in finding out more. I know the "curve" is probably different, but if we can get close (and there are a LOT of different mustang units for different injector sizes) and tune it with an S-AFC we might be on to something. I know the Mustang AFM is sized by different size venturis where the wire is... that makes it read differently for cars with different injectors.

Brad

David88vert

http://www.corral.net/tech/powerplant/maf_tech_2.html
http://www.corral.net/tech/powerplant/mafrelocate.html
The above references tell you about the wires off the MAF. You will need the RX7 FSM and the Mustang FSM for all of the exact values and computer measurements.

Oh yeah, I was using a 2000 4.6 MAF

http://www.corral.net/tech/

RexRyder

iTrader: (10)

I remember someone taking off the AFM and taping the little flapper thing so the ECU thinks its at WOT and just leaving the AFM there and put the filter over the turbo, but the engine blew. If you taped the flapper thing all the way to WOT and used a SAFC to lean/richen fuel mixture. Or hook up the flapper thing to the throttle linkage somehow and use a SAFC. might be a stupid idea tho.

RETed

No.


-Ted

von

yes stupid idea. Someone already tried it on an N/A and blew his engine on the first run from running to lean. The AFC does 50percent plus or minus.

RexRyder

iTrader: (10)

explain??? it could work if it was hooked up via throttle linkage (flapper on AFM). get a air/fuel mixture meter to see where ur leaning/richening then adjust it with the SAFC.

tweaked

iTrader: (4)

It does work, I hvae done ( sortof). the hard part is to get it to open at the same rate it does if it wer moving air. Meaning it need to be in the same position at 50% trottle as it would at 50% useing it the right way. then when youy get that figured out you simply run a throttle cable to where the AFM sits normaly and you are done. I am almost to that point, but I had to move and now we are painting the house and stuff. everything has been put on hold. A better idea is to reverse ingineer a manifold pressure sensor to work with our computer.

Evil Aviator

Yes, there is something to it. The stock FC sensors calculate ambient air density, and the ECU calculates the manifold air density based on the estimated turbo and intercooler efficiencies. With the sensors mounted after the turbo and intercooler, the actual air density may be calculated very close to the manifold, which makes for a more accurate reading. However, I highly doubt that the Japanese are using stock RX-7 AFM's, as they would probably get damaged in that location, especially from off-throttle reversions. The stock ECU would also be worthless in this configuration if you wanted to tune accurately. I would imagine that they are using some type of aftermarket performance EMS. Do you have any pictures?

Although the temperature sensors are the same, the S4 and S5 AFMs have different signals on some of the other outputs. Using the TII AFM as an example, compare page 4B-60 of the S4 FSM to page F2-80 of the S5 FSM.
http://fc3s.org/

S4 AFM Fully Closed = 200-600 Ohms
S5 AFM Fully Closed = 200-1000 Ohms

S4 AFM Fully Open = 20-1000 Ohms
S5 AFM Fully Open = 20-800 Ohms

Yes, it may work, but it will obviously not work correctly until the resistances are corrected with the appropriate homebuilt circuit. Even then you will still have the same non-programmable slow S4 ECU (half the processor speed of the S5) running your engine. Not worth the trouble IMO.

No, you have it backwards. The stock FC systems ESTIMATE mass airflow based on expected turbo and intercooler output, while MAP-based systems (called Speed Density systems) CALCULATE the mass airflow if the sensors are properly positioned. Speed Density systems only require RPM and manifold pressure inputs. Throttle position is used by both Speed Density and Mass Airflow systems for secondary functions like acceleration enrichment. Any type of open-loop EMS (including carbs and mechanical fuel injection) will go "outta wack" when the VE changes. Someday there will be a fast-acting closed-loop EMS which will answer all our prayers, but not today.

There IS a good AFM solution - aftermarket EMS units from Electromotive, Haltech, Microtech, Motec, Wolf, etc. Maybe they can't run closed-loop in any condition other than cruise, but they DO allow for a Speed Density or Alpha-N setup which is basically the same concept as putting the AFM after the intercooler, except that they have much better processors than the ancient stock S4 and S5 ECU.

Not possible with the stock RX-7 ECU. A hot-wire AFM requires the ECU to maintain the temperature of the wire as the intake air cools it - this is how a hot-wire ECU calculates the mass airflow. The RX-7 ECU has no hot-wire calculation function or hot-wire output lead to heat the wire.

Oh boy. Try this - look under the hood of a stock RX-7 while the engine is running. Have a friend floor it up to 5000rpm or so, and then let off. Notice how the throttle linkage always moves before the airflow changes the angle of the AFM. The two move independently.

I don't see how the pressure sensor would work with an ECU which is looking for an air volume signal. Maybe you can explain that one?

A better idea is to spend your time painting someone else's house, make some money, and buy an aftermarket standalone EMS.