SpooledupRacing

I am taking this from my days with Datsuns and I have seen that using a turbo mass air meter will actually give more gain on a n/a car then using the n/a mass air.. I was curious if the t2 mass air on a n/a car would lean it out a bit or richen it out or anything at all?

if u have any info to pass on please let me know I searched and found nothign in the FAQ

SpooledupRacing

anyone?!?!

J-Rat

iTrader: (2)

There has not been any documentation that I know of showing any gains by swapping the AFMs between TIIs and N/As. Most gains are realized by using an SAFC or some other form of translator.

SpooledupRacing

ah ok... if anyone else has any conflicting info please post!

Dave

HAILERS

Yeah, I've run a turbo afm on a non turbo. Did it again this morning just for fun. The mixture is leaner. I have a wideband on the car and can see it's leaner. NOT too lean. I have no idea how this effects the timing. The car runs just fine like that.

In my opinion it runs a bit crisper. Sorry, the wideband on that car is an older wideband from OZ and does not log. Maybe someday I'll get another Zeitronix and log with non turbo vs turbo afm's. That is not a near future thing if I ever do it at all.

RotaryResurrection

iTrader: (8)

The guys who swap AFM's on other cars generally do so because the turbo AFM is larger in some way. Our NA/turbo afm's are identical in size, but they are calibrated differently so that the turbo meter can measure more air. This is accomplished by a stiffer spring on the turbo model, which requires more force to open. Therefore, if the NA engine requires X amount of air, and the NA meter would be open halfway at X airflow...then the turbo meter will not be open as far at X airflow on the NA engine. SO, the ecu sees a lower AFM opening, and injects less fuel. So it should run leaner across the board.

Many people do not know this, but your AFM can be adjusted to run richer or leaner as well. There is a bypass adjustment on the AFM that acts as a fine adjustment for the flapper. ON the series 4 afm, you can also adjust the spring tension a few clicks to obtain a richer or leaner mix. Before the days of fuel computers, these used to be old school AFR hacks.

SpooledupRacing

EXACTLY what I wanted to hear.. this was the entire concept I was going for..

leaner conditions in safe aspects would increase hp (maybe not by much) and crisper throttle response and better pull.. so this is whay I asked..

I knew u could adjust them HOWEVER doing so on yoru only AFM is not a good diea ESPECIALLY if u dont have a wideband because if u break it the car wont run or atleast not worth a crap!!!

Thx guys u have been ALOT OF HELP... now to find a T2 mass air

fastrotaries

N/A's tend to run too rich up top anyway. Leaning it out there, would yield you a little more power, if anything much better throttle response.

classicauto

iTrader: (3)

I ran a TII afm on my old DD. Couldn't tell any difference in driveability or power. Meaning it really wasn't noticable, Im sure it affected something to some percentage of a percent, but nothing noticeable.

I did it out of necessity because my N/A afm went for a **** and the TII was down at that time. But I had people telling me it would blow the car up and all this other crazy B.S. lol it works just fine. Im sure it probably runs a little leaner due to the different calibrations, but nothings going to ***-plode on ya.

SpooledupRacing

do u know if there is any difference in using a S4 or S5 my car is a S4 n/a I know the T2 mass have different part numbers for S4/S5 however I dont know if they wire up differently or one is larger then the other etc?

classicauto

iTrader: (3)

I know you *can* go to a different series AFM, I'd PM sureshot, he had a write up on how to use a 929 AFM on an S5 TII, Im sure he'll have the particulars you're looking for to go with a different series AFM.

j9fd3s

iTrader: (3)

all the s4 meters are wired up the same and the same physical size, except the european s4 (look for a distributor) which has the same sized afm, but its wired differently.

the s5 afms are also identical in size and wiring. you can plug a 929 or 626/mx6/probe v6 afm in, its wired the same, but larger physically

SpooledupRacing

I wonder if a Datsun AFM will work it is bigger and has the same plug in as the RX7 and I have a few of those around here...

anywho I wanted a T2 because in theroy a T2 mass on a n/a would lean it out a touch which may give better throttle response and better top end..

Dave

Valkyrie

A weakened spring (developed after 15+ years of driving I would imagine) could easily throw off the calibration of the AFM, right?

According to one of my Japanese RX-7 tuning books (my ONE japanese RX-7 tuning book that is... I'll make sure to get more next time I'm there :p), it says one of the most important things you need to check on an FC before tuning it (besides injectors) is the AFM, because if it's off, it could cause engine blows due to incorrect AFRs.

I would imagine that the actual reported air flow would be approximately the same given any AFM of a similar type, maker, etc, even if they had different flow capacities (ie, stiffer springs)? Or would the resistances for each level of fuel flow be dependant on the ECU's settings?

It seems to me that a weak, old AFM spring is probably one of the reasons that FCs (especially NAs) tend to run so rich (hurting gas mileage as well)... since a weaker spring tends to lose it's memory faster than a strong one, I think.

The FSM says not to adjust the AFM, though... and the cone-type doesn't seem like it would be very easy to take apart.


BTW, I can hear my AFM's spring slinking around inside of it. This sort of screams "too weak/loose" to me.

seventh_rx

I'm looking into doing a GM 3" conversion. The vein airflow is extremely restrictive.

HAILERS

1. I wouldn't adjust the internal spring unless you really, really carefully mark where the *dog* was prior to moving anything. I've waddled down that road before on a couple of afm and really don't recommend it (just advice, you did not mention doing this, that I know).

2. A better investment would be a USED SAFC. Been there and done that with success on a non turbo (present 86 na car). The only requirement would be at LEAST using a narrow band 02 gauge or volt meter tapped into the 02 sensor output to the ECU.

3. The USED SAFC would be much better than the T2 afm and better than fiddling around with the internal spring.

4. I say USED SAFC because they cost a bit too much new, but then you take a chance the original owner botched up the SAFC.

SpooledupRacing

Well I am going to go with the used SAFC route sine I was offered one at a great price...

however should I still add the T2 afm or not will the SAFC just give me the same adjsutability with either afm?

HAILERS

No. Just the SAFC is all you need. There's a sub forum on this site at here: https://www.rx7club.com/forum/forumd...ysprune=&f=123

HAILERS

Also look at the following site. It gives you an idea of how to do the install. http://www.1300cc.com/howto/how2/safc.htm

About the manual: Out of all the pages, only about four have squat to do with the RX-7 so don't be intimidated by the number of pages.

Frankly I used crimp connections. Male and female terminations and to crimp them, used a ratcheting crimp tool I bought from AutoZone and I saw one at PePBoys the other day.

Those work much better than the non ratcheting ones, and that ain't just MY opinion. There's no need to solder them if you use a good crimping tool.

HAILERS

There's other ways of leaning the mixture out. On (in) your car there is a Atmospheric Pressure sensor. It's used to gauge altitude (who'd a thought) so that when you climb into higher altitudes it lets the ECU know and the ECU in turn leans the FUEL mixute out because of less air being up there in Denver. It's located inside the series four cars and on the passengers side, way above and to the right of the passengers feet. Looks SIMILAR to the pressure sensor in the engine bay.

Soooooo, if you varied the signal from the atmospheric pressure sensor to the ECU, you could lean the mixtue out. OR if you wanted RICH instead, just disconnect the plug off it and the ECU will default to a sea level atltitude. So if you did that in Denver, that sucker ought to really be rich through the whole range of rpms.

I never go around to doing that on the 1986 na. But, I've a RTEK 2.0 on the turbo car and I've inputted a 2500 ft altitude as the default altitude and sure enough..........it leand out the fuel through the full range.

The SAFC will do the above without that kind of trickery.

Or just at idle and only at idle, there is that Variable Resistor up near the afm/pressure sensor area. It has a screw that will turn about 3/4 of a turn from end to end of its pot. Don't worry about messing with it. Just look at where it is prior to messing with it and when your though just put it back where it was. But you'll find that if your car has sort of little miss while idling fully warmed up, that by turning the screw clockwise, it richer, that that little miss will go away.

That variable resistor mostly only works with idle rpms around 750 and below. Above 1100 rpm it won't do squat. Just never try to make the screw go past it's *stops*. If you bust it, it will go to a default value in the ECU. I forget or never knew what that value is. Probably the halfway voltage of the pot. Just works for IDLE in case you missed that.

My5ABaby

iTrader: (7)

Interesting. How would I vary the signal from the APS? And... would it be considered safe for an N/A at something like 1000 ft. above sea level?