Bike Lambda readings...

Paul Thompson 'Hooligan' · 01-29-08, 06:12 PM

Hi all -
As some of you are aware I purchased a GSX1400 last May, my first bike for some 25 yrs and having done the running in, I've added a couple of bits. Firstly, I've fitted a PowerCommander III USB to enable the fuelling to be tweeked and have just fitted an 8-channel data logger under the seat. This records RPM, Speed, Throttle posn and G forces.

Now I know that the standard link pipe to the exhaust can (Yoshimura) is restrictive, so I've fitted a derestricted link pipe that a friend made and have had a lambda boss tigged to it's side.

This enables me to log the mixture of the motor via the output of a Motec PLM.

It was clearly lean initially but now with a modified map in the PC, it seems to go well, but possibly too rich. I will get it on a dyno in the near future for some custom mapping, but as I've no experience of modern bike motors, do any of you know what is an acceptable target AFR for such a motor?.. I'm happy to run it leanish for cruising, say 13.8/14:1 and the logger has shown that less than 20% throttle is required for most road riding, BUT what about wide open throttle?

The image below was logged recently and had the throttle mostly wide open for about 11 seconds. It gives a steady AFR of 12.1:1 - too rich in my opinion.. Any knowledged comments / thoughts would be most welcome.

Big-Foot · 01-29-08, 07:00 PM

On the bikes I've tuned / worked on - Around 12.5:1 is good - maybe up to 12.7:1

Only problem is that the only way you're going to get a good and true reading is with a Wideband (heated) sensor.. The other sensors just don't get hot enough to give a good and true reading that is repeatable..

That's my $.02 worth on it...

I've fiddled with the Power Commander on EFI systems where I did not have access to altering the programming directly in the ECU. The PC is not a bad system when it's the only tool you have to use..

Paul Thompson 'Hooligan' · 01-30-08, 01:01 PM

Thanks Randy - the Motec meter is wideband and heated, so gives accurate readings between about AFR 10:1 and AFR 480:1

I'll lean it a little I think for the moment and get it on a dyno in the near future too.

I think 13.8:1 - 14.5:1 will be ok for light throttle cruising too, so will target that area too.

When you say 'having access to altering the programming directly in ECU' - have you cracked the mfrs code? - if so, which makes and did you have any software aids you'd recommend to make it easier?.. I know there is a 'Yoshi box' available that enables you to tweek the mfr settings but as I understand, it is not very tunable and operates over broad areas of the fuelling map..

Anyone else 'been there - done that' too?

Big-Foot · 01-30-08, 01:21 PM

Make sure you are monitoring the EGT when leaning it out. If she goes over 1350f for any duration, it may well lead to detonation as well..

I have broken some ECU's but that's in a previous life and time - it is exceptionally tedious although very rewarding when you burn your first PROM that actually works..

The last one I worked on was that of the early Victory motorcycles (99-01) before they switched to the Delphi system.

You need to find a way to capture the binary from the ECU and then use a decompiler that is meant for the PROM/EPROM of the ECU. Sometimes these decompilers are expensive and hard to come by. Sometimes you can find free ones. Sometimes they don't exist at all..

The aftermarket ECU's like the TEC systems are coming down in price and could be a good alternative. Like I said just be careful of the EGT and Detonation. Also - set your rev limiter no higher than the mfgr's spec until you have your programming well under control..