EGT Readings... What are you getting ?
#31
Rennlist Member
Thanks Wayne, that's pretty much what I came to as well. What effect does say the size of your headers have, or if they're coated / wrapped. Would going up in size of intercooler / pipes have an effect? If this is the case then what about opening up all your breathing, or is that too much in front of detonation if you know what I mean?
#33
Addict
Rennlist Member
Rennlist Small
Business Sponsor
Rennlist Member
Rennlist Small
Business Sponsor
that’s right - richening the mixture won't help. The only thing that will help is to advance the timing (this will also get you a little more power). But to do this you will either have to run less boost or better fuel.
#34
Addict
Rennlist Member
Rennlist Member
Join Date: May 2001
Location: A suburb of Silicon Valley, CA
Posts: 2,099
Likes: 0
Received 7 Likes
on
3 Posts
I use the Zetronix data logger to measure my egt. Number 4 cylinder. City driving at around 2500 rpm the egt is usually around 1250. Freeway at 2500 rpm is usually around 1450. Constant crusing at 4500 rpm on the freeway, it has crept as high as 1650. 1650 worries me.
I do not remember where....but I read an article that Porsche put out on the 944 engine that used the term "thermally optimized combustion". It was in reference to the DME strategy for fuel efficiency. I do not know all the engineering behind "thermally optimized combustion" but the higher the cumbustion temps, the more complete burn you will have, and thus the better the fuel economy. I believe this "thermally optimized combustion" is the culprit behind all the smog failures. High combustion temps also create NOX. High NOX seems to occur on all our cars.
Most articles that I have read on egt seem to recomend temps around 1200. With such high egt levels, its no wonder that Porsche used expensive sodium filled valves, ceramic lined ports and stainless steel headers.
The article also noted the "fuel shut off at closed throttle" strategy.
I do not remember where....but I read an article that Porsche put out on the 944 engine that used the term "thermally optimized combustion". It was in reference to the DME strategy for fuel efficiency. I do not know all the engineering behind "thermally optimized combustion" but the higher the cumbustion temps, the more complete burn you will have, and thus the better the fuel economy. I believe this "thermally optimized combustion" is the culprit behind all the smog failures. High combustion temps also create NOX. High NOX seems to occur on all our cars.
Most articles that I have read on egt seem to recomend temps around 1200. With such high egt levels, its no wonder that Porsche used expensive sodium filled valves, ceramic lined ports and stainless steel headers.
The article also noted the "fuel shut off at closed throttle" strategy.
#35
Drive-by provocation guy
Rennlist Member
Rennlist Member
Join Date: Apr 2002
Location: NAS PAX River, by way of Orlando
Posts: 10,439
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Bill
I use the Zetronix data logger to measure my egt. Number 4 cylinder. City driving at around 2500 rpm the egt is usually around 1250. Freeway at 2500 rpm is usually around 1450. Constant crusing at 4500 rpm on the freeway, it has crept as high as 1650. 1650 worries me.
I do not remember where....but I read an article that Porsche put out on the 944 engine that used the term "thermally optimized combustion". It was in reference to the DME strategy for fuel efficiency. I do not know all the engineering behind "thermally optimized combustion" but the higher the cumbustion temps, the more complete burn you will have, and thus the better the fuel economy. I believe this "thermally optimized combustion" is the culprit behind all the smog failures. High combustion temps also create NOX. High NOX seems to occur on all our cars.
Most articles that I have read on egt seem to recomend temps around 1200. With such high egt levels, its no wonder that Porsche used expensive sodium filled valves, ceramic lined ports and stainless steel headers.
The article also noted the "fuel shut off at closed throttle" strategy.
I do not remember where....but I read an article that Porsche put out on the 944 engine that used the term "thermally optimized combustion". It was in reference to the DME strategy for fuel efficiency. I do not know all the engineering behind "thermally optimized combustion" but the higher the cumbustion temps, the more complete burn you will have, and thus the better the fuel economy. I believe this "thermally optimized combustion" is the culprit behind all the smog failures. High combustion temps also create NOX. High NOX seems to occur on all our cars.
Most articles that I have read on egt seem to recomend temps around 1200. With such high egt levels, its no wonder that Porsche used expensive sodium filled valves, ceramic lined ports and stainless steel headers.
The article also noted the "fuel shut off at closed throttle" strategy.
Thanks to people like ST and Laust and others that have really pushed the boost limits we are seeing it is no longer theory that pressure does not blow HG or motors.....HEAT/KNOCK blows them. If your a/f & timing (EGT's) are spot on, you can run a LOT of boost.
#36
Drive-by provocation guy
Rennlist Member
Rennlist Member
Join Date: Apr 2002
Location: NAS PAX River, by way of Orlando
Posts: 10,439
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Duke
Excessive richness will raise the EGT. Measuring in the crossover I would say you don't have to worry if you stay below 1750.
I can't remember how much drop in EGT there is from the headers at the block to the crossover, but 1750 at the crossover would be MUCH hotter at the chamber.
The crossover is where you mount your wideband not EGT.
#37
Addict
Rennlist Member
Rennlist
Small Business Partner
Rennlist Member
Rennlist
Small Business Partner
Originally Posted by toddk911
but 1750 at the crossover would be MUCH hotter at the chamber.
Rogue
#38
Drive-by provocation guy
Rennlist Member
Rennlist Member
Join Date: Apr 2002
Location: NAS PAX River, by way of Orlando
Posts: 10,439
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Rogue_Ant
Maybe, maybe not. Retarded ignition timing and a rich mixture can burn well into the exhaust stroke, causing a high EGT.
Rogue
Rogue
#41
Addict
Rennlist Member
Rennlist
Small Business Partner
Rennlist Member
Rennlist
Small Business Partner
Originally Posted by mikjel
Well, my egt dropped 50-70 fahrenheit when richening from 12,7:1 to 11,5-8:1.
Rogue
#42
Rennlist Member
Man this tuning caper is so involved. So many things impact upon something else. I can see going around in circles is a distinct possibility!
#43
Addict
Rennlist Member
Rennlist Member
Originally Posted by toddk911
Correct. But my point was in regards to readings at different points. The most accurate is at the header. The reading at the crossover, regardless of what the number is, will be lower than at the header. If you are tuning based on your EGT reading at the crossover, you are in for trouble.
If you have a rich mixture or retarded timing, the fuel will not completly burn in the chamber, and also not likely at the port, it will burn in the availible space in the header, crossover, or the rest of the exhaust. This is evident when you see flames during shift points. The temps during off throttle shifts at the ports is much lower than that in the pipe simply because the fuel is buring in the pipe and not in the chamber.
I use my EGT numbers as a baseline for my car. Each adjustment for fuel or timing will change the reading. Being able to identify peaks and valleys, and know why they happen, is key, not the raw number itself.
#44
Originally Posted by hp18racer
Advancing WOT spark timing 4 degrees in my car dropped the peak EGT I see at the track about 100F. I measure it 1" into the exhaust.
#45
I hooked up a digital counter to KLR pin 15. At 17psi, 100 octane I see almost no knock events. If I go down to about 50% 91, 50% 100 octane at the same boost level, I see dozens of events on every hard acceleration. Watching the knock counter I can figure out what octane I need for any given boost level to be knock safe. If the a/f and knock are behaving, then I'm looking to keep EGT in line with stock number (1650 or less) to not burn up valves.