Hope this is in the right section for this.

In the process of building my Tech Edge wideband 2Y1 kit and would like to gather peoples thoughts on what AFR I should be aiming for at the various points ie:

Idle
Low cruise
Low acceleration - moderate cruise
High cruise
High acceleration

My preference is for economy at cruise, but power at high acceleration. TIA

Jim

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'68 Morris Mini 1310 A+ (Now Sold!)

Hi there,

I also have a techedge wideband (2J1) and have found it a handy little tool. I also have a GM MAP sensor hooked up. I log MAP, AFR and RPM using Winlog, from that I can get a bit of a picture if I'm heading in the right direction (or the complete wrong one!)

As for AFR's, it's hard to say what will work best for your engine without access to a dyno. You'll find all sorts of numerically crazy AFR's will give you car that still seems to run ok. It's also difficult to ascertain what AFR under load is giving you the most power by the "seat of your pants" technique!

On cruise with low load (say 80kmh cruise in 4th) I've tried to get it as lean as possble without causing surging. I've got it down to a 15.2 AFR

On load (pulling up a hill, flat to the floor) i've found around the low 13's seems to be ok, but I can't really qualify this without any dyno time.

I've found since having the wideband, I've got the car feeling more responsive and with significant improvements in fuel economy (after trying many SU needles!)

Good luck with it!
Andrew

Thanks Andrew for the info. I will have to pull my finger out and finish the WBO2 kit. My USB to Serial cable just arrived via post, but having much trouble getting Windows 7 to start the driver!

I haven't got a MAP sensor yet, what one did you use, or would recommend?

Cheers, Jim

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'68 Morris Mini 1310 A+ (Now Sold!)

Hi Jim,

I'm not 100% certain of the origin of my MAP sensor, it came out of my vast collection of old EFI car crap! I believe the same sensor is used in many applications (JE camira, N13 pulsar, VN-VR commo, some daiwoos) Its generically known as the GM 1 bar MAP sensor. It only has 3 pins/wires, ones +5v (I use an LM voltage regulator to supply this), a ground, and a signal out (which goes to the techedge) You could
use any MAP sensor, but there is a lot of info for GM ones available via google.

I'd suggest just getting one from pick-a-part or similar, probably be quite cheap (or free... ) make sure you get the plug with it too.

Andrew [/b]

For Max Power AFR should be 12.7:1 and for criuse you should be able to get it to run satisfactorily at around 16 or 17:1, although your ignition system will need to be right up to scratch for the leaner mixtures.

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Hi GT,

Would that 12.7:1 be near enough to correct for all NA A series applications? I was under the impression (from my limited knowledge on the subject) that this is something that varies from engine to engine.

Thanks,
Andrew

Hi there Andrew,

It is the theoretical ratio for all NA Engines and is about spot on for the A series. Some variation from that would be a good idea to try with most engines to reach optimum, however you would need to do it on an egine dyno and under the exact same conditions on every run to try to accuratly measure any changes as it it would be small.

To give an example, if maximum power is reached at 12.7:1, then making it richer to say 11:1 would make around 97% of the max power and likewise leaning it to say 14:1 would make around 95% of max power. Not a good idea to go any leaner than 13.2:1 if your trying to make power though, could be nasty to the engine.

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