2 X A.f.m. And 2 X T.b.

[NA_R33]

its not 50% more fuel rather its modfying the signal by 50% of a value... Exactly what that value is a dont know...

Eug Gtrs have to imputs into the standard computer 1 for each afm...

Rather then a y pipe i would be option for either a custom box fed cold air with large area panel filters or twin ram forced setup pods... no point doing all that and having the same amount of intake restriction with a single filter..

[NA_R33]

its not 50% more fuel rather its modfying the signal by 50% of a value... Exactly what that value is a dont know...

Eug Gtrs have to imputs into the standard computer 1 for each afm...

Rather then a y pipe i would be option for either a custom box fed cold air with large area panel filters or twin ram forced setup pods... no point doing all that and having the same amount of intake restriction with a single filter..

[xRHETTx]

Firstly, hi to all in NA land, this is my first ever time in this section of the forums (got sucked in by the thread title).

Before you give up on the 2 AFM idea (and I think its an awesome idea), ditch the SAFC and get a Jaycar Digital Fuel Adjuster (DFA).

It will definately be able to do what you want, in fact it even mentions in the Performance Electronics for Cars book (from Jaycar) that they used it to fit 2 AFMs to a maxima or something.

Basically, as long as you can solder and follow instructions, for about $140, (DFA kit, handcontroller kit and cable) you get a digital AFR adjuster that works better than the SAFC. How many load points does an SAFC have? The DFA has 128 not 8 or whatever...

Think about it...

[Nosmo]

The SAFC is only for fine adjustment of the signal going to the ECU and I dare say that the DFA would be the same. To be able to run twin AFM you would need to either adjust the entire fuel table for the smaller values, or find / make some sort of circuitry that adds two voltages together. This is not overly difficult in principle, however finding part will be the key.

The other option is to run the AFM circuitry in parallel. This will give half the resistance for a given airflow and as such twice the voltage. Then you may be able to use an SAFC or similar device to correct the signal back to near original.

However, seeing that the AFM has current limiting circuitry within it, I dont know if the above would work at all... The only thing to do is set up 2 AFM on a bench and measure the output signal...

Although, if your going to the effort of twin throttle bodies why not get rid of the AFM altogether and use an aftermarket ECU with either MAP sensor or throttle position sensor?

[Eug]

i'm guessing a gtr can run a safc - and that the problem is more ecu based in don's case.

is it as easy as splicing the wires from the 2 afm's together? (that sounds really stupid to me, meh)

although the Y pipe will actually be a backwards step in terms of the twin throttle bodies.

maybe something such as this is an option? ie. with the same volume as 2 afm's?

ecu upgrade sounds like the easy solution, however not the cheapest.

keep it up don, good to see someone doing something different.

eug

[Kor'axis]

Why not just use a Small Signal Voltage Amplifier circuit set to double?

[dondesoto]

Firstly, hi to all in NA land, this is my first ever time in this section of the forums (got sucked in by the thread title).

Before you give up on the 2 AFM idea (and I think its an awesome idea), ditch the SAFC and get a Jaycar Digital Fuel Adjuster (DFA).

It will definately be able to do what you want, in fact it even mentions in the Performance Electronics for Cars book (from Jaycar) that they used it to fit 2 AFMs to a maxima or something.

Basically, as long as you can solder and follow instructions, for about $140, (DFA kit, handcontroller kit and cable) you get a digital AFR adjuster that works better than the SAFC. How many load points does an SAFC have? The DFA has 128 not 8 or whatever...

Think about it...

<{POST_SNAPBACK}>

thanks for the ideas , yes i got that book around here somewhere , must read it and get the brain into gear again

[dondesoto]

THANKS FOR ALL THE INPUTS SO FAR .

SORRY HAVEN,T BEEN HERE FOR A FEW DAYS TO RESPOND .

I figure the simplest way is to run a single AFM . The apexi is switchable between most nissan afm inputs including z32 and infinity 90 mm . i,m now making a Y piece and will just hook up a rb25 afm until i can get something bigger . This year when i ran at the salt lake speed trials the afm didnt max out , it went to a max of high 60 %s , was reving up to 7000 rpm . heres some figures of areas of t/b and afm .

2 x rb25 t/b ( 60mm dia ) 56 sq cm

1 x rb 25 afm ( 75 mm dia ) 44 sq cm

1 x z32 afm ( 80 mm dia ) 50 sq cm

1 x q 45 ( 90 mm dia ) 63 sq cm

Edited November 3, 2005 by dondesoto

[Kor'axis]

sorry but i still fail to see how this woudl lead to more power... theres no more air getting through. You still only have 1 inlet?!

[Kor'axis]

I don't mean what your doing is bad... in fact i think its great. I'm just a noob who doesn't really understand

[Br4nchi3]

Excuse the crap 2 minute drawing in paint.

The first pic is what a normal setup looks like.

The second setup is what dondesoto is going to do (as far as i know), the throttle body has 2 intakes now but the Y piece will restrict the air to the 2 intakes because only limited air can go through the AFM.

The third setup is what we wanted to do, but the ECU cant read signals from 2 AFMs, only 1. This setup allows twice the amount of air which is what we are aiming for.

But untill we can get the 2 AFMs to send 1 signal to the ECU to get proper air/fuel mixtures it aint gonna happen. I'm not an expert so correct me if im wrong.

[Eug]

ryan is pretty much on the money.

however kor'axis, the Y inlet would infact "bottleneck" the air flow to both throttle bodies, thus making the whole twin throttle body idea useless...

but don has done some calculations and if you look at his last post above, you will see that the area of 1 rb25 throttle body is 60mm in diameter this means it has an area of roughly 28 square centimeters, and since he has two throttle bodies - that will total to 56 sq(uare) centimeters.

now, in order to overcome this Y bottleneck, the afm must flow at least equal to or more area than the two throttle bodies combined - thus making the q45 afm the best option. the rb25 afm is too small by 12 sq cm, and the z32 afm is just under by 6 sq cm.

however! don has also mentioned that the last time he ran the single rb25 afm he didn't max it out - thus making the z32 afm a possible option as well.

to put it simply, don will theoretically have twice as much air flowing.

rb25 afm "may" restrict the 2 throttle bodies, the only way to know is to put it on and see if it maxes out.

z32 afm is theoretically just under the area don needs, but will see in future if he decides to use one - and if it maxes out.

q45 afm is theoretically the most appropiate for the job, capable of flowing much more than what don requires - will see how he goes.

keep us posted don!

on another interesting note:

Has a dyno proven 198.5rwhp (148rwkw) and a best time of 13.98 at 97mph

Also in an R31, and also NA - but this runs an RB30E

[dondesoto]

Thanks again for the inputs .

Now i,m going to try 2 things.

You see i have just replaced the fuel press gauge on the fuel reg . The old gauge was reading way too high . In reality i was only running 20 psi , its now reset to 36 psi . Now thats messed up all my air fuel ratios and have had to reset by pulling back around 25 % with the apexi safc . SOOO i am going to put on the 2 x rb25 afms and see if i can adjust it up to what i need . i now have around 70 % scope to play with . At present the apexi safc it set around minus 20 % , and you can adjust them to 50 % plus .

Ya with me .

Now if that dont work i will finish off the Y piece which is 2 x 75 mm tubes running to 1 x 90 mm tube ( when i can find a bit ) then to an infinity Q45 90 mm afm

[PHATR32]

oi, you checked out these articles? they show you how to add 2 afms to one ecu

http://autospeed.drive.com.au/cms/A_2424/article.html

http://autospeed.drive.com.au/cms/A_2449/article.html

steve

[xRHETTx]

Yeah I still think 2 afms is the onlyoption worth considering.

Remember, even with using the one 90mm AFM, the biggest restriction with the Y-setup is going to be in the Y where the 2 flows hits each other - heaps of turbulence (not good).

[dondesoto]

oi, you checked out these articles? they show you how to add 2 afms to one ecu

http://autospeed.drive.com.au/cms/A_2424/article.html

http://autospeed.drive.com.au/cms/A_2449/article.html

steve

<{POST_SNAPBACK}>

AHA Just read those articles and it seems i was heading in much the same direction , except i will have the 2 x afm , not 1 x afm and a secondary bypass . i will fit it and see what happens . i could probably just wire up 1 afm and be able to adjust the air fuel ratio to what i need

[Deano]

on another interesting note:

Also in an R31, and also NA - but this runs an RB30E

<{POST_SNAPBACK}>

oi whats my engine bay doing on here Looking a bit dirty though

Btw. It's up for sale guys, you to can own Australia's fastest & quickest Naturally Aspirated Skyline

http://forum.r31skylineclub.com/index.php?topic=31702.0

[NA_R33]

Don i have a Q45 AFM, call me if ur interested. 0417 608 538

[dondesoto]

Don i have a Q45 AFM, call me if ur interested. 0417 608 538

<{POST_SNAPBACK}>

THANKS FOR THE OFFER .

1ST I,M PUTTING THE MANIFOLD ON THIS WEEKEND WITH THE 2 X RB25 AFMS AND TRY AND ADJUST THE APEXI SAFC UP TO GIVE ME THE FUEL I WANT .

IF THAT DOESNT WORK I WILL THEN GO FOR THE SINGLE Q45 AFM .

WILL KEEP YOU IN TOUCH AS TO HOW IT ALL GOES .

THANKS AGAIN

[Br4nchi3]

GOOD LUCK DUDE, LOOKING FORWARD TO SEEING HOW IT GOES!

Ohh damn that felt good.