Hey guys After not being able to sleep last night I was up and chatting with my friend Jon and we were talking about the two styles of AFM's and which was better but we both agreed that we hadn't seen any factual testing on which was better and less of a restriction. After some thought and a cold glass of milk I remembered that I still have the magnehelic hooked up to my Sport that we used to test the stock intake for restriction. This lead me to want to try out and see which AFM creats more of a restriction. All I have to do is use a cone filter for ease of swaping and we can test the two after I figure out the re-wire procedure. What do you guys think? I am mainly waiting for NZ and the other smart guys to come up to this thread and see what you think guys. Let me know if its been done before or not so I don't waste my time and gas.



Santiago


PS-Still need to test the damn CAI :-/

 

To get an accurate comparison, you'd need to test both AFM's on the same car, with no changes other than the AFM. Every engine is different (obviously S4 and S5 are), and a different airflow will give a different pressure drop. If you did one test on an S4 car and one on an S5 car you won't know if any difference in reading is because of the AFM or the engine.

 

Yeah the plan was to do it on my 87 N/a with both the S4 and S5 AFM. No other changes and use the same cone filter.

 

What would the results of this test be used for?

Not trying to rain on your parade, I just don't understand what the point would be.

If it was determined that one was better than the other (in terms of flow), you still couldn't use it unless by some amazing stroke of luck it read out the same voltage at the same airflow volume. Otherwise, you'd just be confusing your ECU. I suppose you could compensate with and SAFC, but otherwise you might actually lose horsepower even though you had a more free-flowing intake.


Hmmm....

You would have to test 3 confgurations:
1) Both meters in series. This would give you a good idea how closely the voltage output matched at different airflow volumes
2) S4 only
3) S5 only

The last two would give you an idea of the peak airflow each unit allowed. This would all have to be done on the same car, at the same temperature, etc.

 

Basically people already do the swaps now and the cars run fine. It doesn't confuse the ECU's. You only have to re-wire the damn thing. But basically it would just be information. The use could be whatever we come up with. Say your working on making the best flowing intake and you have only the stock ecu to work with but you have the S4 and S5 AFM and you can use either one. You can make an educated descission about which one to use. Or something else. I am taking the role of the scientist not the end user.

Santiago

 

I still would be interested to see the results of a test with both sensors in series.

This would tell you how close the sensor's outputs matched each other for a given set of conditions, and it would give you a metric to see which flowed better.

 

Yeah I will have to figure out how to run the signals into the cabin from both AFMs if I can get them both on there.

 

It doesn't have to be permenant, so you could run the extra set outside the car. Just have a passenger with two voltmeters taking data while you drive.

 

I have a place to route the wires. But I personally don't know how to re-wire the AFM's to be able to swap them so I will have to do research on that. Unless anyone wants to post up a link or a small "how-to"

Santiago

 

I found this posted in an old thread. Has anyone actually done this with success? It looks simple enough to do with some wire and spade connectors but I thought I would ask for more input.

Santiago

 

I still think the Zenki AFM is going to have better flow potential than a Kouki AFM, even though a LOT of people think otherwise.

WHY?  At least the Zenki AFM has a *hole in the center*, so airflow potential is most in the center, as dictated by laminar "fluid" dynamics.  The Kouki AFM is as big ***** in the center, so all air flow has to move around the center portion.

Go for it!



-Ted

 

This is basically what I want to prove to people and start making things be FACT and not just assumptions based on oppinion. With a magnehelic guage setup and only allowing the AFM to be the variable by retaining as little change or zero change if possible between the runs/tests.

I think the S4 will flow more air.


Santiago

PS-S5 my ***! edit** or should I say vida's ***

 

That looks sensible, just make sure you don't accidentally short out the 5V supply from your ECU. That would be bad.

I would also double check this "fuel pump shutoff" swtich comment, as the switch is supposedly off with the AFM closed and on will the AFM fully open (88 FSM page 4A-54). There is no description of the switch's behavior when partway open.


....I just looked at the wiring diagram. The statements about the purpose of that switch are correct. Looks like I'll be jumpering it when I do my MAF conversion.



...oh and you should check the intake temp senor resistances in each FSM to see if they match up.

 

Yea I am thinking about taking my spare AFM's male S4 plug out and trying to find a burnt up wire harness to get the female plug out of the S5 and make a plug and play dealy.


Santiago


PS- If anyone has a harness that is all burnt but the connector is still good then hit me up with a price.

 

yah i think the 89-91 afm will flow better when its not all the way open, but when they are all the way open the 86-88 one will be better. i get my kooky confused with my zenki

 

I think Zenki is the "early" and Kouki "later". S4 and S5 respectively.


Santiago

Although I would be wrong

 

Sweet to hear it......your gonna do testing and all. Dude, on the next post you need to not use Magnehelic as the subject line. Your gonna confuse people and all.

James

 

Let the uninformed be confused! :p
jk


Yeah I need to ask Icemark to spot me and change the tittle to "S4 Vs. S5 AFM"

 

*yawn*

I made that wiring diagram about 2 years ago. It works with no ill effects.

I HAVE DYNO PROOF the S5 is better:
Last year I ran my car on the dyno with the S4 AFM and S5 AFM back to back. Same car...same air filter. I ran the S5 AFM first, then the S4, and then back to the S5.

The graphs show that the S5 AFM nets you 1 RWHP. Yeah!

Case closed, next experiment.

 

Don't forget that the S5 AFM's inlet is smaller that the S4's.

S4: 63mm x 50mm = 3150mm²

S5: ~60mm ID (can someone confirm?) = 2827mm²

So the S4's inlet is 11% bigger, which is fairly significant. If you look at the cutaway of the S5 AFM in the FSM you'll see the internal airway isn't exactly huge either.

Personally I wouldn't want to swap to an S5 AFM purely because of losing the fuel pump safety switch. That puppy could save you from going up in flames, so I'd rather keep it.

 

As I've been trying to point out, if the s4 & s5 AFM's read out slightly different voltages for different airflow readings, it's not a fair comparison to just swap them out and measure horsepower, because you'll be running with different air/fuel ratios.
So if one could flow better, but results in a worse air fuel mixture, you'd think it's worse, when really you could do better with the other sensor and a SAFC.

At a minimum, there's a question of whether both sensors read out the same voltage for the same airflow.

 

Flow and HP are different animals though. :p case not closed!

 

theloudroom is absolutely correct. If swapping on the S5 AFM causes slightly more restriction (less power) but results in slightly leaner mixtures (more power), the result is negligible net change in power, as wozzom's testing showed.

wozzoom, did you compare A/F ratio's as well as power?

 

Title updated as per thread starter.

 

I would be VERY much interested in knowing the real voltage difference between the two styles AFM rather than the flow potential. By voltage difference I mean the curve of Voltage output vs Airflow. Anybody ever did that? Like mentionned before, if we applies aerodynamics basics, well the S4 has a better flow potential. Another interesting point also is the "adjustability" of the flapper style AFM, which the cone style does not offer.