Anyone got any idea how this bit of kit actually works.

I'm considereing that one may become necessary with an intake mod I'm currently developing, however somewhat sceptical of this unit.

I'm guessing it somehow modifies the lamda sensor output so the ecu always thinks things are a little leaner than they actually are - am I right??

 

it piggy backs onto one of the wires going into the ECU (oxygen sensor I think) and I imagine it either strengthens or weakens the signal thus raising or lowering the mixture

I have one and thats the best way I can think of describing its functionality

 

Thanks bud - as I suspected - I guess the limit of enrichemnt over standard would be down to Injector duty cycle - I'm hitting 83% max at present so looks like there is some scope for adjustment.

 

It taps into the MAF sensor signal and allows AFR adjustment by modifying the signal


Cheers

 

Most of these type of units work by changing the signal from the MAF sensor so that the ECU thinks there is more air flowing in than there really is and ups the fueling. Altering the signal from the lambda would be pointless since the ECU only reads from it under relatively low load conditions, on boost and full throttle running the ECU works in open loop mode and does the fueling by reading air flow, boost etc and then using a look up table to decide how much fuel is needed, the AFR device just changes what it looks up in the table to cause it to come out with more fuel. Altering the lambda signal would cause the car to run rich around town when it isn't needed and would murder your fuel consumption but it would still be lean when running WOT and high boost, so you would still be liable to engine failure.

Also be aware that the subaru ecu uses the MAF signal to adjust the timing too, so your AFR device isn't just altering the mixture.

 

Small changes go a long way also - a 10% change in MAF voltage on full load will adjust the airflow that the ECU reads by about 18%. There is a second effect - the ECU's lookup for AFR will also be different, typically by say 6%. Overall you are looking at about a 25% change in AFR for a 10% change in MAF voltage... so this could compensate for 550cc instead of 440cc injectors.

HOWEVER, a typical advance in timing on a UK 99/00 with an 18% change in load would be about 10 degrees.

10 degrees is the difference between running happily on a trackday on NUL and blowing up your engine from det by using Optimax and loads of NF just blasting down a dual carriageway.

I have tried to illustrate real life changes based on typical areas of ECU maps I am familiar with on MY99/00. These are examples only, should not be taken as read. Your mileage may vary etc etc

 

OK - now I see a bigger picture.

As I'm pretty sure that my induction mods will cause a general leaning of the mixture at high rpm here's my thinking.

From what you are saying John the AFR device will retard the timing as it enrichens the mixture and advance it as it leans it out (oooooooh nasty).

I'm currently pootling around in a v3 Sti JDM - standard ECU This of course means I'm mapped for 100 RON fuel and have somewhat over advanced timing - speaking generally here of course.

What I'm hoping is that I can kill two birds with one stone - I've been looking for a way to retard the timing a degree or so - it looks like (and of course I'd have to experiment a little here) that with a small increase in MAF voltage which'll get me my enrichenement I'll also get some retard - correct? the unknown seems to be how much but I sould be able to use my scoobymonitor to let me know.

Also it seems that this should only effect things at higher loads as the scoob ECU switches from lambda sensor readings to MAF readings - any ideas at what point this actually happens?

Ultimately I realise that the best solution is remappable ECU - unfortunately a remap just isn't an option on hte '97 JDM so it's bigger bugs replacement ECU from Link or (if I win the lottery) MOTEC.

 

Thinking about this myself, following the same sort of logic as dr_jones.

Has anyone fitted one of these - if so what result do they give, and what setting are you using for typical stage 1 mods (induction+ 'zorst)?

Cheers
Freshtripe

 

No one using one of these?