7 replies to this topic

[WilsonSteele]

I am about to put on the adjustable FP system from weekend racer (shameless sponsor plug), and i'm headed out to put on the innovate EGR sensor system.
The inqusitive engineer in me wonders, why, on gasoline motors, do we measure EGR? Why do we not measure EGT like they do on diesels?
I always thought that it would be knocking, or early detonation, that rocks the piston before TDC over from the compression side of the cylinder wall to the expansion side and can damage rings.
But isn't that lean condition that raises in-cylinder temps and can damage rings, also going to result in high EGTs?
Just thinking thru things here, and trying to learn, does the knock, that can bend a con-rod, happen so quick as an engine leans out that EGT can't follow it? Why can EGR follow it, then?
I certianly don't think an engine has ever been damaged by highly acidic or sooty exhaust, so it's not really ratio we want to monitor, but that indication of iminent engine damage.

I look forward to the reasoned and comical responses...

[Bench Racer]

Many people do measure EGT on their race motors. Would you like to measure an average temperature like we measure the average AFR or would you like to measure for each cylinder. I have a dual WesTech EGT unit that was used in an  RX7 rotor motor that is available.

[Danny Steyn]

David 

 

yes there are some very knowledgeable guys in this class that measure EGT, and adjust accordingly. Unfortunately I am not one of these really smart guys! 

[Rob Burgoon]

I am about to put on the adjustable FP system from weekend racer (shameless sponsor plug), and i'm headed out to put on the innovate EGR sensor system.
The inqusitive engineer in me wonders, why, on gasoline motors, do we measure EGR? Why do we not measure EGT like they do on diesels?
I always thought that it would be knocking, or early detonation, that rocks the piston before TDC over from the compression side of the cylinder wall to the expansion side and can damage rings.
But isn't that lean condition that raises in-cylinder temps and can damage rings, also going to result in high EGTs?
Just thinking thru things here, and trying to learn, does the knock, that can bend a con-rod, happen so quick as an engine leans out that EGT can't follow it? Why can EGR follow it, then?
I certianly don't think an engine has ever been damaged by highly acidic or sooty exhaust, so it's not really ratio we want to monitor, but that indication of iminent engine damage.

I look forward to the reasoned and comical responses...

 

By EGR you mean AFR or wideband o2 right?

 

EGT is something that you use when wideband o2 isn't practical due to leaded gas or alcohol or when you want reliability rather than a wear item. (airplanes)

 

EGT is a little less useful than AFR since I think it peaks and goes back down in temp as you go leaner.  I don't think anyone is using EGT or AFR primarily to avoid engine damage, I think it's used as a tuning tool to help you find peak power once you know where that is from dyno testing.  It's also a sanity check to make sure all is working well.  (Going down the straight.. is my AFR XX like it's supposed to be?  Good)

[Rob Burgoon]

Also, the mixture in a miata wanders all over the place as you change rpm.  In an airplane you're likely to be at a constant rpm and have the time to stare at the EGT gauge while you slowly adjust mixture from the cockpit to tune for cruise or power or whatever.

[Jim Drago]

Many people do measure EGT on their race motors. Would you like to measure an average temperature like we measure the average AFR or would you like to measure for each cylinder. I have a dual WesTech EGT unit that was used in an  RX7 rotor motor that is available.

 

It is best to monitor each cylinder. My goal was to match the injectors with the cylinders. I have matched the injectors to the cylinders in the past( best flowing injector with hottest cyl) and put back together. Little to no effect.  I even swapped temp sensors from hole to hole, still same thing. # 4 was always the warmest. 

I don't monitor EGT any more unless I have a problem I can't find. 

[Bench Racer]

It is best to monitor each cylinder. My goal was to match the injectors with the cylinders. I have matched the injectors to the cylinders in the past( best flowing injector with hottest cyl) and put back together. Little to no effect.  I even swapped temp sensors from hole to hole, still same thing. # 4 was always the warmest. 

I don't monitor EGT any more unless I have a problem I can't find. 

10-4 on monitor each cylinder.

 

Don't know about the cooling system on the new (99 plus) cars, but the hot #4 cylinder on the 1.6 and 1.8 cars is the limited water flow from the rear of the head. Might there be value in writting a letter to the CRB to request a rule that the water from the rear of the head may be re-routed?

 

Then again hoses are free, maybe there is a work around that might be only slightly in the gray area.

[Rob Burgoon]

10-4 on monitor each cylinder.

 

Don't know about the cooling system on the new (99 plus) cars, but the hot #4 cylinder on the 1.6 and 1.8 cars is the limited water flow from the rear of the head. Might there be value in writting a letter to the CRB to request a rule that the water from the rear of the head may be re-routed?

 

Then again hoses are free, maybe there is a work around that might be only slightly in the gray area.

 

I think it's been suggested and shot down pretty hard since the racing is good, cars aren't bowing up, it's a $350 kit, and it would harm the SM aftermarket radiator business.  Oh and "inconsistent with class philosophy" which can kiss my ass.

 

I don't agree with the reasoning, but that's the impression I had.

 

Now that was a fast hijack!