Finally fitted my AFR (Autometer) and it seems to fluctuate a lot, i.e. if I'm flat out it reads a little rich, as I'd expect, if I back off then it reads very lean and goes of the gauge, but most of the time it seems to be up and down like a yoyo, from what I understand it reads .05V to 1V, dependant on the amout of o2 in the exhaust manifold, how does to scooby work i.e should you get 0v when you back off as NO fuel is present, bit puzzled.

Any help

 

my scoobymania leds read rich ie one green light when accel/most of the time up and down like a yoyo and nolights when i take foot off gas pedal

 

Matt,

Sound perfectly normal. Read the John Banks Thread on how to build your own AFR. It explains exactly what you should be seeing & how the ECU controls the fuelling etc.

But as a brief overview (coz I can't find the link myself).

When not under load (ie cruising & idling) the AFR pulses up and down - this is called stoich & is normal for emmisions & fuel economy - also often colloqually referred to as the "Night Rider Effect".

The speed of the pulses & ratio of fuel are dependent on throttle possition, load & RPM. When cruisimg at motorway speeds the bottom three LEDs on my home-made AFR 720,740,760mv dimly pulse.

Hope that helps.

Chris.

 

Cheers for that, I did speak to Scooby Sport and a few other people and they have told me much the same, at full chat it runs not rich but on the rich side, which I also inderstand it about right for an STi V3, was thinking of getting a boost controller and running around 1.3 maybee 1.4 bar what do you think, It seems the fueling will be OK as its runs 1.2 now just wondering about the timming, will this be a problem?

Chees in advance

Matt

 

With Boost Controllers & Jap imports you need to be careful, as these are designed to run on 100RON minimum.

I'm not an expert, I'm just recalling what I've read.

You may not be running lean at WOT in third under low load - but how is the fuelling in 5th part-throttle full load - I think almost every scooby (even my UK running Optimax ie +3RON) runs lean here - therefore for Jap import it is more crucial.

Would recommend Boost Guage + AFR + Knocklink (& if really paranoid EGT too).

I'd take all the precautions - ask an expert - best of all get the fuelling professionally checked out on a Rolling Road.

Would also recommend reading all the Dawes Posts on here for starters.

Regards,

Chris

 

Already got the boost and AFR, boost is just getting upto 1.2KG/cm2 so around 1.2bar which is about right for an STi as when I called Scooby sport about it they told me it would be running 1.2bar before I had chance to say anything, EGT will be going in as soon as I can sort out somewhere to fit it as I've got the earlier dash, I'll be having a triple A-pillar commisioned soon so will have some room for it. At full chat it is still running a bit on the ritch side which scooby sport also said is the case however they also said that they have more engine rebild on STi's due to boost controller that anything else, my question is realy, is this down to people running stupid amounts of boost and can I run 1.3/1.4 bar, I appreciate that I shound realy go for an ECU upgrade, but they are big cash and I've spent most of my cash on my Supra (www.supra.fsworld.co.uk if your interested) so really looking to just give it the edge, 320bhp, which would also leave second gear in tact, as it seem that the gear box is a bit weak and anything upto 350 is going to lead to problems, going to stick with the standard clutch as I'd rather have the clutch slip than kill the box.

Matt