Hello all, i've been reading through several threads regarding AFR settings and the use of wideband devises to check them. Could use a bit of definative info regarding what the AFR should be for my new ABF engine, i've just ordered a AFR guage & wideband sensor (Same as NigeP is using, PS great thread) I'll list my engine spec below, hoping Toyotec, Brookster & Mike H might help out... Std capacity 2.0ltr ABF Lightened & balanced stock crank, front pully, flywheel & VR6 clutch Stock ABF head with Newman 288 cams (Cams from Sambo) Integrated engineering H Beam Rods Wossner 12.4:1 Comp pistons Ashley 4 branch header & system Dellorto twin 45's KR Ignition & dizzy, 6-8 deg BTDC Thanks, hope you can help. PAB
I`m sure the experts will be along soon. But in the meantime... If you can get the AFR to be around 12.5, thats your goal as far as I`m aware you don`t want to be over 13.5 if you can help it. I`ve got mine down to 12.5 up to 6k, then it starts to rise, thats just the K-Jet but you don`t have that. That setup is really useful, its very easy to read at a glance and reacts very quickly, you blip the throttle and there is very little delay in it reacting. If you are on a set throttle for a few seconds, it settle down very quickly. I think you`ll be impressed and hopefully it will help you ensure everything is running sweetly.
Thanks Nige , it should be here tomorrow, so fitting on the weekend. How far back down the exhaust did you mount the sender, it will be easier for me to put it in the centre section just after joint from my 4 branch header. That would put it directly under where the shifter used to be, I have my shifter inside like yours. PAB
Nige, isnt 12.5 a bit rich for NA engine? On FI engines high 12-s low 13s is about perfect, i always thought NA needs to be around 13.5-14?
Really depends on the type of engine. This is where some sort of dyno is beneficial to determine what is your best LBT (lean best torque). Without doing any data sweep I would say for N/A between 13.5-12.5.
Nice spec - as already said, at wide open throttle, start at about 13:1, give or take. Assume this is going in a Mk1/2 Golf? If you can find the money, getting the head worked could make a big difference in there. I think it'll be the bottleneck in that setup. At the very least, get the valve throats bored, and the seats 3-angled. Hope you've got a full vernier setup for those cams. While the full throttle ratio is important, you need to keep an eye on tickover, light load, and overrun settings too. From testing on my Kjet Scirocco Mk2, I've been taking baseline data to work from. What I've found on this, and on other standard Kjet and Ljet cars from the same era (no catalysts), is that generally they run at about Tickover - 17 or 18:1 Light Throttle Openings - about 15:1 Overrun - 22-23:1 On a high performance engine, I'd go a bit richer than those, especially if you're not going to do lots of miles in it, but those are decent settings to work from. All the measurements I took were with an Innovate LM-1 handheld.
Thanks all for your great info thats why I love this forum! Fitted the Wideband sensor and guage this morning, AEM kit seems good quality and has all you need, along with NigeP i'd defo reccomend one. I'll get some figures off it soon. Mike its gone into my Mk2 Jetta track car, so the engines not really gonna see any "road" miles. The head is next on my list, as you can appriciate got to have the budget to do it properly, i'll put it on ITBs when the headwork is done. Thanks all again. PAB See you all soon at Curby.
Tickover measurement is far too lean (past misfire on a PFI engine). You may find that there is not a good sample quality at idle ( flow and velocity), to provide an accurate reading when you use a STD Innovate exhaust clamp. If you weld and extension to this from A/C pipe the probe sample point can be moved higher in the exhaust piping and access a more concentrated sample that would correlate closer to combustion lambda. Had to resort to this, when having to set up some Jap cars with 4 inch exhaust tips @ idle VW 16v engines run at 15 to 14.0 with tweaks on MBT spark to increase smoothness. Part load 15.5 to 14.7. Again spark settings do matter here if drivablity and mpgs are to be delivered as expected. Fuel shut off ( EFI) = engine as air pump AFR > 16 to full scale defection on the gauge approx 20.7.
