Fuel distribution through the cylinders

I am after any evidence (or indications even) in the event that some of the cylinders run richer than others, using the standard inlet manifold ofcourse.

Doing a search on this site, I've found conficting views on the subject of EGT variations from cyl to cyl.

Some say #6 runs hottest, others #1 runs hottest, someone else that they all run the same.

I understand that there are differences among US/UK/Jap spec that could affect the EGT spread. EGTs aren't even the ultimate goal, just an easily measured byproduct. Separate AFR probes would be ideal.

Any ideas on the subject would be welcome, because I'd like to be prepared for the maximum variation of AFRs among the cylinders (I will be running very lean -by most people's standards - and any variation over 5% might send me into the dark side, yet I want to be as close to stoich as possible)

Thanks guys.

This may interest you, its the fuel trims per cyl on an AEM tuned car, you can see that 1, 5 and 6 have more fuel added as RPMs increase.

Note: this was not tuned by me.

Wez, would you know what are those injectors 7,8,9?

Are they extra ones fitted on the rail?

Why, one wonders, do they have the rpm load sites going up to 11,200rpm

I also wonder if that's 5% more overall duty or 5% more of the current duty...? Seems like a lot to add either way...

-Ian

John,

It's because the AEM can control them, and the default setting for that view template shows them.

Ian,

The RPM loadsites are fully customisable. I would hazard a guess that Wes hasn't adjusted his yet. As there is a fixed number of loadsites, having redundant ones at the top of the map, means you're losing resolution within the parts of the map that you're actually using.... that is unless Wes hasn't told us something very interesting!

The other question is:

This extra injector percentage --- how did it come to be?

On what basis was it deemed necessary?

My trouble with the AFR gauge is that it reflects an average of all cylinders.

But if one or two tend to flow a lot more air, then an indicated AFR of 14:1 might translate to 15:1 for some cylinders and 13:1 for others. That is something I'd like to avoid if I can (not lethal under my setup, but hairy...)

There is only one way to trully get past this and know .. an O2 sensor on each cylinder...very costly .... broadbrushing % and then doing it to say your own engine is just way out as no 2 engines will behave the same, It will be as close as the average wallet will be able to get going by Broadrated settings or other users known settings ..but not perfect. Unless you want to pull the plugs every five minutes ...but without fuel control how are you going to address this ?

What fuel control?

If you mean *individual* injector control, then that's not what I'm after.

I just want to know how good the stock manifold is with air distribution.

Being Toyota I'd expect it to be pretty damn good, but then again you never know. They do run these cars abysmally rich --- even with the turbos pushing 19psi (way off the stock settings) and the MAP sensor fooled to show 15psi, it still runs 10:1.

That *might* be a way to hide a distribution issue (apart from the fuel shower for cooling purposes). I don't know for sure, that's why I'm asking.

I've seen pictures of supra exh manifolds having an EGT sensor in each runner. Maybe someone did intake pressure/vacuum readings on each runner too?!

I remember reading a thread on Supraforums that did comparitive flow testing of the OEM and aftermarket intake manifolds, which was very interesting read. It was at least a couple of years ago though.