DOHC & SOHC Manifold switching

[thrash]

perhaps you should take them out onto the track with you sometime then

[thrash]

Has anyone here ever tuned with 4 bungs welded into your exhaust manifold for an O2 sensor? Like done 4 runs with the O2 sensor moved each time?
And then just tuned the car to the leanest cylinder?

Reviving an old thread.. but this interests me..

does anyone know if people have tuned with an oxy sensor per cylinder and whether it was effective in reliably extracting extra power from the motor?

I would think it would be.. but then you wouldn't want to keep the oxy sensors in there since they'd get destroyed? Do narrowband sensors get destroyed by the heat as well or would they survive do you reckon?

I've seen drag cars with thermocouples on each runner of the exhaust mani.. but haven't been able to find any info on if people put oxy sensors in the runners..

[fugazi]

4 EGT's will do the trick when tuning a motor... no need for more then 1 BBL.

[thrash]

how do you accurately tune using egts? from what i've read, egts actually go down a notch when detonation occurs?

[docile]

how do you accurately tune using egts? from what i've read, egts actually go down a notch when detonation occurs?

You use egts firstly to even out the cylinders afr, as most ecus nowdays allow you to do so. Secondly you ensure that egts don't get too close to 1000deg for std petrol turbos, otherwise kiss the turbo good by. Diesel turbos have a 600 or so degree limit, not sure about tiAl turbines.

You need a knock sensor setup to reliably measure detonation. Egts and afr won't tell you this.

[thrash]

so.. similar egts on each exhaust port = similar afrs in each cylinder? how accurate is that? there are a lot of things that affect egts aren't there?

[coop1er]

Firstly a narrowband oxygen sensor isn't going to give you much useful info, they are only accurate around an air/fuel ratio of 14.7:1. I think that fitting a wideband oxygen sensor for each cylinder is overkill on the sort of engines that most people build for the sake of a few percent improvement. Besides that, widebands are quite expensive and don't usually last a long time anyway.

Exhaust gas temperatures are affected by things other that just air fuel ratio, so I wouldn't be relying on them to fine tune an engine. For example, ignition timing has probably the biggest influence of EGT and different cylinders in the same engine often require slightly different timing to be at their most efficient. Also any difference in the effective compression between cylinders would alter the EGT's.

To sum up, on the sort of engine an enthusiast would build, use a single wideband and a safe air/fuel ratio. Use a thermocouple if you want to make sure everything is ok. Save your money for other easier ways to make more power, rather than tuning to within the last few percent.

[thrash]

thanks for the info. Not that i'm planning to do this, but learning this stuff is fun, and who knows, it might come in handy down the track.

So.. now that you've confirmed that egts aren't really an accurate way of measuring afrs in each cylinder, what about using narrowband sensors on each exhaust runner to even out the afrs on each cylinder? Even though they only measure accurately at 14.7, you could set your afr at this for low rpm and use the readings to confirm the percentage differences between each cylinder? I suppose you could just keep the sensors in there as well and and use them for closed loop operation for efficient offboost running? Will they survive the heat?

[fugazi]

BB & NB on each pipe is an overkill if yure not racing... according to me.
This is a Swedish guy's Camaro with 8 of everything... motorwise!