Fooling Air Flow meter

[EnricoPalazzo]

Currently my car is having lots of problems, this could be related to my AFM maxing out. I am running a unichip ecu, and we think that at over 5500rpm, the afm maxes out, and hence pulls shitloads of timing. Therefore im gettin a power curve which looks like a zig zag loosing +- 20-30 rwkws.

So my quesiton, is there any way to fool the afm so that the ecu reads a lower voltage. Is it possible to put some resisitors in the circuit or anything like that?

I will be searchin for an answer. It seems everyone just upgrades to a z32, but im not entirely sure a z32 will work with the standard ecu and unichip. If i cant resolve this problem, i wil have to purchase another ecu, and all my hard earned $$ will go down the drain

[EnricoPalazzo]

from what ive been reading, units like the safc trick the ecu by modifying the voltage of the afm signal. Since the Unichip has pre programmed units set for ign and fuel, why cant i just put a few resitors in the voltage signal wire so that the ecu will always only see a few volts less then what is actually happeing. Even thou the afm is still maxing out, the preset figures will not be over ridden by the ecu.

anyway i will post some dyno graphs so u can see what i mean.

[Penfold]

The trouble with a resistor is the whole voltage signal will be reduced (ie say at idle when it should be say 0.9 itll read as 0.7) so it'll still be getting incorrect readings. So you would still need some form of ECU calibration.

[fresh]

you could insert a throttle position controled variable resistor, so the resistance only kicks in once you hit a certain rpm, or throttle opening, depends on how good ur tech skills of course....

alternately have a manual controller, though it would be a bitch

[boj01]

Get a Z32 AFM meter. It will be a good upgrade anyways as it is bigger in diameter. A SAFC could solve the problem by tuning it out.

[the phantom]

I sounds as though you just need to find a decent Unichip programmer. Isn't there two in Adelaide- the one you dont like and another-blackwood dyno and service? I dont really know anything about the Unichip but considering the hype and marketing, cant it be configured to read TPS and RPM? I think having this and then adding resistors (you would need two in a voltage divider configuration, with large values so as to not load the AFM output) is a bit of a band aid....Either way you would still have the voltage clipped, albeit at a lower value when the AFM runs out of resolution.

[EnricoPalazzo]

Well i will speal to blackwood auto and dyno and also speak to unichip. Basically i know of another r33 similar mods and power that also ran into a brick wall like i did at this power.

It seems that even thou the unichip is an intercepter, somehow the ecu can still override the settings on it.

boj01: z32 and r33 afm are both same size in diameter. Also im not sure if the z32 can be compatible with standard ecu. Also why would i want a safc when i have sometihn that both tunes fuel and ign with shitload more resolution then what a safc has. The only beneift of the safc would be that it is compatible with the z32 afm.

I was thinking the same thing about adding a resistor, it would obviously effect the whole rpm range, so during closed loop, the car would not run well i assume. can u explain to me how to setup a variable rate resistor, as i have done basic elec eng, but as im a mech eng, we only did basic elec shit.

thanks guys

[Jay95R33]

What your looking for is a boost cut defencer (I think that's what their called).

Say your AFM max's out at 5.1v, what this thing does is it clamps the voltage at say 5.0v so it never max's out. Under this voltage it runs as normal.

But this is really a band-aid fix.

When you start maxing out the AFM the stock ECU will always pull timing, and you won't be able to over ride this totally with the unichip as it doesn't always happen.... If it did it ALL the time, then you could tune the unichip to override it, but it doesn't

By the sounds of it, you have just about reached the limit of the unichip/stock ECU combo....

I'm pretty sure Matt (whatisname) had the same problems.

J

[EnricoPalazzo]

yeh i was talking about matt having the same problems. SO basically there is nothing i can really do to fix this except get a z32 afm? FARK.

[EnricoPalazzo]

also a boost cut defender wont do shit.

I dont get why u cant just try to fool the ecu that the voltage is less. Sydneykid? ANyone know this answer?

How come the Emangae doesnt have this problem when they are almost the same thing?

[the phantom]

I dont think there is any cheap/simple/nasty way to implement a sophisticated enough programmable 'variable rate resistor' without ending up with a microcontroller circuit. By this stage you will have re-invented the wheel and created an interceptor like the Unichip itself.

[geraldjohn]

hey enrico,, i have a "field hyper R" fuel controller that intercepts the voltage fron the afm maybe you could try to get one,, they are not that expensive

[Sydneykid]

Hi Enrico, how much power is your car making?

[Cubes]

Enrico,

From memory the Unichip can only alter the signal by say +- 10degree igntion or similiar for the afm.. Hence why the afm most probably still hits a brick wall and why the z32 afm wont work with it as there isn't enough adjustment..

Don't quote but from memory when I looked in to a piggy back when I first bought my car that is what I was told.

[Robo]

Hi Enrico,

I had the same problem as you....

My r33 had a big loss of power around 5000 rpm, took me about a month to work it out (soo annoying).

All I did to fix my problem was find a friends AFM (which happened to be re-conditioned unit) and swap it with mine.. what a difference it made (I could feel it on the road).

I have attached my dyno graph to show you. The lower of the two lines is with my old AFM.

From what I remember it costs about $150 for a re-conditioned AFM.

Regards

Rob

ps. not saying this will fix your problem, but for the price......

[Busky2k]

I would be suprised the RB25 AFM would be maxxed out at 200rwkw?

Cos with my SR20 AFM, its not even close to getting maxed out at 183rwkw. IIRC, last time i checked, it was about 4.6V at peak power, and this is for an AFM for a smaller motor?

And the unichip would obviously reduce the voltage at certian rev ranges to get the right AFR, just like any other interceptor would, so you can get the Unichip ppl to do so accordingly, to banaid around the maxed AFM, if it really is.

[EnricoPalazzo]

im currently making somewhere between 210-220rwkws @ 13 psi.

if i can post a dyno graph hopefully it will help explain some things.

[Sydneykid]

Hi Enricho, time to stop guessing, can I strongly suggest you connect a multimeter up to the AFM and go for a drive, have your passenger read off the voltage. This will answer the question as to whether or not your AFM is reading max voltage (5 volts) in less time than it took me to write this post.

I can tell you I have seen cars with 250 rwkw without any AFM problems and someone else will say they have seen cars that do it at 180 rwkw. The truth is, every car is different, the only way to know for sure is to measure it.

If you don't have a multimeter, then borrow one or buy one from Dick Smith, they cost $10 for one that will do this job and thousands of others around the car. Cheap, usefull tool.

Hope that helps

[EnricoPalazzo]

Hey gary, thanks, i was going to do this today, yet it was pissin down and basically not the best weather to give it a go, however i will def tomorow.

[EnricoPalazzo]

well today, i got my gf to read out values to me when i was drivin the car. At around 5500rpm, the car is reading 5.05v.

the voltage does not get any higher. Is this maxed out?