Bumpin' Yota

what?

My 3vze VAFM flow meter starts out near zero at idle and as the flapper opens the voltage increases to a max of 5v.

It was the 3vz-fe's who have the inverted Vs voltage...

Crymson

That's strange my vafm starts out around -4V and tops out at about -0.3V when the door is wide open. This is from an '88 3vze, I do have a spare vafm from a 91 3vze, suppose i'll check that one out right now.

suprathepeg

And Supras IIRC.

Crymson

Tested both vafms and they operate in the same manner, with the vehicle off and the ignition on both supply a voltage of 4 and approach 0 when being opened. With the vehicle running, the voltage reads out at 1.5 and approaches 0 with increasing throttle. Now you're saying that your vafm starts at 0 and goes to 5 with increasing throttle?

Somewhat of a sidenote: Supra AFMs do run on the same logic, I have one off a 5mge and those also run from 4.5 to 0V when approaching full range.

Back to the heart of the issue, so assuming you are correct that 3vze vafms run from 0 to 5 volts, then the majority of maf and map sensors run on a scale of 5 to 0 volts or else this statement from Panhead would be untrue.

But knowing what we do about the hotwire type maf sensors: "A hot wire is maintained at a constant temperature in relation to the thermistor by the electronic control circuit. An increase in air flow will cause the hot wire to lose heat faster and the electronic control circuitry will compensate by sending more current through the wire. The electronic control circuit simultaneously measures the current flow and puts out a voltage signal in proportion to current flow" (http://www.autoshop101.com/forms/h34.pdf). This denotes that most afms do use a higher voltage to indicate an increase in airflow.

At the end of the day, you are truly lucky if you have a vafm that goes from 0-5v, as any sensor conversion would be easily done with some sort of piggyback system (apexi, splitsec, etc...) In my case though the 5-0 volts is an obstacle in my conversion to another type of air metering system.

Weasy2k

Im going to look into it more once i get the engine running again...voltage flip is not a huge problem..

Bumpin' Yota

Ohhh split second! That was the controller Gadget was recommending I get for the MAF swap! I do have a BIG tax refund...hmmmmm

I dunno, on mine ('90 3vze auto and demo model at the lot) it started out low and went up as I opened the VAFM... I also have a VAFM supposedly from a 7mge bought on ebay and it had the same range. But I shall double check both tomorrow for ya in a study break. (ANP1 lab practical #2 on tuesday...lol - gotta keep this 100% roll going! 3 99%s or better and 4 to go!)

Weasy2k

when dealing with a maf swap you should also look into things like timing control...as far as i know yous till cannot ADVANCE timing...which renders this entire swap pointless.

I will be working with this AFM to MAF conversion over the next mth or so in my test 4runner using the smt6's ability to fully control timing as you can push the timing limits when you got the airflow coming in. This plus a cam swap could be some nice power gains...cant wait to get this engine running!

hokiruu

Why would this be pointless without advancing the timing? The stupid flapper is a restriction. Getting rid of it should eliminate or reduce this restriction. Restriction= inefficient. Get rid of restriction= increased efficiency.

Yes playing with the timing could yield more power but does not dictate whether or not getting rid of the flapper is worthwhile.

hokiruu

Bumpin Yota I also recommend the A'pexi SAFC or Greddy eManage.
Having a visual interface > ambiguous little black box. In the case of theeManage, it can do a hell of a lot more without even costing a ton more. SAFC can control fuel as well.

Weasy2k

Time and money spent you will not see "yields" that you expect from just removing the AFM....UNLESS you do other things like FI...or other head work...

What efficiency you talking about? the ability to FLOW more air? yes but if the engine wont TAKE IN more air...what is going to occur?

hokiruu

lol i see what you mean. yeah, dollar per wheel horsepower, these damn engines are screwed compared to others. that being said, i know it would not produce any REALLY significant gains at all, but in theory, even with the current timing, I'm sure it would help. Would I spend $500-600 on it? Probably not. As far as the timing goes, what would you propose?

Weasy2k

That is why i am doing it in conjunction with the cam install. These cams will be able to flow more air through the head and increase the VE of the engine...so the effect of having a MAF will help it out a bit more then just stock for stock.
Taking it a step furthur with timing control could yield some VERY decent gains!
IE: Switching to higher octane fuel and advancing the timing by 5-6 degrees would yield 10-15whp (depending on the engine of course). People have argued with me in the past that you could just turn the distributor, but that effect aint to smart as it will advance the timing across the band vs on certain spots that you want to. Like i would not want to advance the timing 5-6deg near redline for the threat of detonation, but a bit lower yes. You can also flick a switch on the smt6 and go back to stock timing settings and 87 octane when needed

What i am working on now is a little "upgrade" kit that will help give the 3vz-e more guts. How much? I dont know yet...will see in a mth or so's time.

Bumpin' Yota

I will not buy harbour freight multi-meters!
I will not buy harbour freight multi-meters!
I will not buy harbour freight multi-meters!
I will not buy harbour freight multi-meters!
I will not buy harbour freight multi-meters!
I will not buy harbour freight multi-meters!

Either someone tagged me with the retard stick several months ago or my 4.99$ Habour Freight DMM was screwing up...grrr!

Got a nice craftsman DMM (that will measure duty cycle ) and now im getting 3.98vdc flapper dead shut, and 0.485 flapper wide open...

suprathepeg

So this was for the larger supra afm right?

Weasy2k

supra afm?

didnt htey run with karmen vortex

Bumpin' Yota

No this was for the stock 3vz-e VAFM. I still have to check out the 7mge's VAFM that I have sitting at home....lol

Crymson

So I finally got my car to be California smog compliant again, but once I take it to the station its going back under the knife. I picked up a Split Second ARC2-NE and a 3.5 MAS off ebay for 100 bucks brand new, and will be fabricating a ram air setup for the pickup. So I have the option of using the 5MGE Supra VAFM or this 3.5 MAS from Split Second, to use the split sec unit I will have to make a seperate fuel pump switch and relocate the intake air temp sensor, but here is the dillema. Should I bother with the hassle of using the MAS or should I just use the 5MGE as the flow should be more than adequate. And IF I do choose to use the MAS theres that little "voltage flip," issue that I don't know how to tackle. If i find my camara, I could take pics... this MAS is absolutely huge

enutter

ummmm.......???????????????

Crymson

Great question, what happend to this?

agusgus3

Split second has these two options:
PSC1-004 Programmable Sig. Cal. AFM to MAF-$339
PSC1-005 Prog. Sig. Cal. AFM to MAF w/Inv. Output-$339

this would solve the issue of voltage inversion, accomodate the maf, potential of FI or NA, as well as choice of which maf you want to use.

personally, im going to research some GM 3" maf's or mitsubishi turbo maf's, the psc1-005, or Apexi SAFC and my old solid state book on voltage inversion. see what i can come up with.

just found the FTC1, Fuel/Timing Calibrator, fully programmable. perfect for me, strapping on the the turbo this summer once the old V6 is rebuilt. little pricey at $529, though.