I just dug this out of my records. The guy at thor said it was a little lean but was not detting. Does anyone know if these values are ok for the zed engine, am I running close to the limmit? Bearing in mind this was taken on a cold January day, would a hot summer day make it more lean? I understand what AFR means but have no idea what the numbers mean.

Thanks.

Ideally the AFR curve should be a flat ~12.0 from about 4000rpm, dropping from the lean area at 3000. ~12.8 gives the maximum power, but you don't really want to run that close to the line.

The lean ish bit between about 4500 and 5000rpm is seen on most Z's and is what I'm trying to get rid of on mine at the minute.

A hot day won't lean it out, as you'll be getting less air in, but the charge temp, and so cyl temps will be higher, which will put you closer to detting. A richer mixture will hep to combat this.

I'd start by checking your fuel pressure is OK, because unless that's a GMS chip it's unusual to run that lean

this is my graph from last week

this is my graph from last week

 

That's good. Still got that little lean spot though it's narrowed right down.

John, is the leaning out anything to do with the vtc shift point?

Yeah what effect does the vtc shift point have on it? IIRC we moved mine up to 5,900 from 4,900rpm.

 

Must get to Thor soon :cool:

Shifting the VTC release is only a good idea if you have better breathing on the exhaust side of the engine. IE bigger tubs, decat, better flowing exhaust. The only major one of those is the tubs tho as they present the immediate back pressure. Bigger tubs, move the VTC shift, more torque :dance:

Don't think so, as on mine it's at 5900 and the lean spot is still there. Must get this damn map trace working ...

It could well be some kind of turbulance in the intake not suspending the charge properly. In which case you'll have to add a fair amount of fuel to overcome it. Just had a thought re VTC release. I wonder if changing the boost will affect it. Depends on the relationship between boost pressure and back pressure I suppose. So many things to think about lol

On mine, i just adjusted it while monitering MAF voltage to get the best 'Area under the curve' which I took as meaning that's when the breathing is most efficient.

Ideally the AFR curve should be a flat ~12.0 from about 4000rpm, dropping from the lean area at 3000. ~12.8 gives the maximum power, but you don't really want to run that close to the line.

The lean ish bit between about 4500 and 5000rpm is seen on most Z's and is what I'm trying to get rid of on mine at the minute.

A hot day won't lean it out, as you'll be getting less air in, but the charge temp, and so cyl temps will be higher, which will put you closer to detting. A richer mixture will hep to combat this.

I'd start by checking your fuel pressure is OK, because unless that's a GMS chip it's unusual to run that lean

 

Thanks m8 for the info. I have a JWT chip. So I take it i'm running close to the limit, is it possible to adjust the fuel pressure with standard regulator and pump or is there another way of doing it? Can anyone explain what the two numbers represent in the graph?

Thanks

JWT should be way richer than that, usually about 10.5:1! Get the pressure checked. You can't adjust it with stock reg, but a working stock reg is fine anyway.

Looks like the 2 numbers are just the max recorded AFR on each run, pretty meaningless.

JWT should be way richer than that, usually about 10.5:1! Get the pressure checked. You can't adjust it with stock reg, but a working stock reg is fine anyway.

Looks like the 2 numbers are just the max recorded AFR on each run, pretty meaningless.

 

Ok thanks, I will ask my trusty machanic to check it for me, hope its a easy job to do. Do you know what the fuel pressure is set at and would it be worth increasing it a bit from standard?

It should be 3bar (or actually 2.9something) with the vac line pulled off, engine idling, ~2.5bar with it back on. You really need to check it under load, so it will be 3bar + boost pressure and make sure it holds that up to max revs.