Question for our super techs on individual cylinder AFR's

[FNBADAZ06]

Below is a picture of a LS7 motor on Katech's engine dyno following the installation of their "Street Attack" package, featuring the Torquer 110 camshaft...the same cam I purchased for my car.

620 HP /580 Tq STD

In the picture, the engine is equiped with dyno headers which has an O2 sensor per cylinder, and I'm assuming the other sensors to be EGT's ? Having these installed for each individual cylinder allows the monitoring and fine tuning of the AFR's of each , but in the OEM ECM, can you control injector pulse width's per injector ? If not, then the only way to control each cylinder's AFR would be to use different injector's (different flow rates) for specific cylinders to control a lean or rich condition, correct ?

[Desertdawg]

Unless you could control individual injectors, any discrepency from one cylinder to the next would be better controlled with airflow. right????

[FNBADAZ06]

Unless you could control individual injectors, any discrepency from one cylinder to the next would be better controlled with airflow. right????

Yeah....but you can't control airflow with a single throttlebody, common plenum intake or a single fixed duration/lift camshaft. I don't know if the individual runners in a FAST could control this either, as that's usually velocity, correct ?

[Desertdawg]

Velocity yes but also just as important is runner or pleneum volume. My point/thought was I don't think injector size would be feasible, at least not in a controable way your thinking. Individual injector pulse width would be your best solution for tuning.

[Two Fangs]

Each header primary looks to have a pyrometer and a wideband (UEGO). If the engine suffers a rich or lean condition, the data will tell which cylinder is the culprit, faster than with two UEGOs (one in each header collector), where you really only know which bank took a shit. As far as the other discussion points; by far, the easiest way to change the AFR from cylinder to cylinder is to change INJ PW to each individual cylinder. Easily accomplished on a MOTEC, but not on the factory PCM. So, without fixed injector control, and with a fixed camshaft, what are we to do? I guess the easiest thing to do would be to invest in a MOTEC. But, you could also grind the cam lobes for each individual cylinder, or change to runner design for each runner to compensate (easier and less expensive). The only time I have seen UEGOs in each individual cylinder like this explicitly for tuning purposes and not for data collection was on a carbureted application to ensure the jetting was right. As always, your mileage may vary.

[FNBADAZ06]

Makes sense It just seems that when something goes to shit with a piston or valve issue, the back cylinders (#7 appears rather frequently) are the cylinders that let loose......or is it my imagination ? I've also heard of people using different rocker arm ratios to affect camshaft lift and duration on particular cylinders. I was just mainly interested in what, if any, AFR adjustments Katech would have been able to apply with an OEM ECU if they DID detect a significant rich/lean condition in a cylinder that would adversly affect power production or reliability.

[Two Fangs]

Makes sense

It just seems that when something goes to shit with a piston or valve issue, the back cylinders (#7 appears rather frequently) are the cylinders that let loose......or is it my imagination ?

I've also heard of people using different rocker arm ratios to affect camshaft lift and duration on particular cylinders. I was just mainly interested in what, if any, AFR adjustments Katech would have been able to apply with an OEM ECU if they DID detect a significant rich/lean condition in a cylinder that would adversly affect power production or reliability.

Nope, the back ones seem to be the ones that get eaten. Farthest from the radiator and hottest? Possibly.

Different rocker ratios can be used on the corners, but usually that is when the engine intake has a central fuel source, like a carb, and the air and fuel has to travel a greater distance. It may work oin other applications as well, but it is much more rare.

[FNBADAZ06]

Makes sense

It just seems that when something goes to shit with a piston or valve issue, the back cylinders (#7 appears rather frequently) are the cylinders that let loose......or is it my imagination ?

I've also heard of people using different rocker arm ratios to affect camshaft lift and duration on particular cylinders. I was just mainly interested in what, if any, AFR adjustments Katech would have been able to apply with an OEM ECU if they DID detect a significant rich/lean condition in a cylinder that would adversly affect power production or reliability.

Nope, the back ones seem to be the ones that get eaten. Farthest from the radiator and hottest? Possibly.

Different rocker ratios can be used on the corners, but usually that is when the engine intake has a central fuel source, like a carb, and the air and fuel has to travel a greater distance. It may work oin other applications as well, but it is much more rare.

I'm guessing that might be it, but thought it might have had something to do with the combustion tempature...and maybe the reason why they measure EGT's. If you did see higher combustion temps, could you cool the offending chamber by richening up the AFR ?

[Two Fangs]

Sure, that would be a very effective way to do it, but the stock box doesn't offer that kind of flexibility (richening only one cylinder), but you certainly could do that with a MOTEC.

[Guest Sidewinder]

They may be doing this to save an expensive motor during the test. Like snails said you would get a faster reading from each cylinder rather than a collective reading, thus saving a $$$ motor before boom. One would need an indivudual "everthing" to tune each cylinder separate. Or, now get this, you could call and ask

[Jon]

The newer motors only have coolant vents on the front of the heads. Not on the rear anymore. That doesn't help those back cylinders with those vents blocked off. GM changed from having front and rear to front only after the LS1. You can buy a setup from Kurt Urban or just make your own stuff. You can also just run EGT/AFR in those back cylinders to tune off the historically "worst" cylinders if you are keeping the stock computer.

[NicD]

I am a fan of flowing the injectors and putting the higher flowing ones in the rear two cylinders to help out but even that is very minimal. The rear two cylinders are definitely the hottest running and since nothing is identical per cylinder anyways the easiest thing is to find the limits and just back it down a bit to keep it all safe unless you really just like working on cars that much.