Peak EGT Temperatures

[coaster]

Yes, I'm begining to think that a CHT as well is pretty essential for setting up purposes, neither on it's own is sufficient it would seem

[iang]

I run a cht gauge on mine and works spot on..It's an American gauge made by a company called Dakota and they specialise in gauges for harleys.. In a word you get what you pay for, in that i've tried cheaper gauges and they work ok , but not perfectly in the fact they don't respond quick enough and you can't trust the readings..My Dakota gauge works as it should ,ie inclines,declines, full throttle, and even showed a sudden shoot up when having some pinking issues!!..I've even tested and compared it to a proper infra-red digital hand held tester.. It's that good that if you leave the probe stood so it reaches room temperature and then just grab and squeeze the probe with your fingers it responds immediately to the temp of your fingers. In a word well worth the money..
http://www.dakotadigital.com/index.cfm/ ... prd276.htm

[sideout]

...One thing that doesnt happen on my scooter though that it says in that article above is when i'm ridding and i richen up by putting the choke on my EGT goes down not up

Eden, that's just what I would expect to happen. Richer mixture cools the burn, lowers the EGT reading. I've had a couple of drinks so I could be missing something here :fb: :fb:
Personally, I rely on EGTs a lot when trying to avoid holing my Mugello pistons I find they're good for setting your jetting (for those of us who find it difficult to get to a Lambretta friendly dyno)

[sideout]

Sideout, there's an article posted on the previous page, have a read of that, maybe when your sober though, it would be hard going with a few drinks in ya lol

Point taken Eden
I've re-read the article and have come to the conclusion that the difference I've experienced between a Clubman and a JL3 (same carb with Mugello kits fitted) are due to the effects of the pipes. The Clubman EGT runs significantly lower temperatures than that of the JL3 for the reasons stated in the article. The expansion chamber is basically a tuned pipe which creates a standing pressure wave at a given rpm, this can result in the "after-burn" effect of mixture getting burnt in the pipe on a lightly loaded engine. However, having seen this I've still managed to overcome it by richening the mixture temporarily by flicking the choke on.
You've obviously seen the opposite effect, which is disconcerting in any state of sobriety

[sideout]

The expansion chamber is basically a tuned pipe which creates a standing pressure wave at a given rpm, this can result in the "after-burn" effect of mixture getting burnt in the pipe on a lightly loaded engine. However, having seen this I've still managed to overcome it by richening the mixture temporarily by flicking the choke on.
You've obviously seen the opposite effect, which is disconcerting in any state of sobriety

no, i see the same effect as you, the egt goes down with the choke on your just pissed up you jammy fooka

lol... jammy fooka, luv it! :fb:

[nelson pk]

I found, with a richer mixture your egt's will go down all the time especially when you put the choke on.
What i've found though is that advancing timing will cool egt temps and retarding makes them higher. Yow would think it would be the other way round but i read somewhere that when you retard the timing the gas is hotter when it goes down the pipe as the combustion happens later when you retard the timing. I should imagine if you retard the timing, head temp will go down though, so it is actually making the bike run cooler even though egt temps are higher.

[JINX]

Am I wrong in thinking that the time it takes for the cylinder head temp to rise is alot slower than the change in temperature of the exhaust gases?
I have always used an egt to check on proper jetting at various throttle and speed settings, the reponse rate is very quick, even blipping the throttle while decelerating causes a dip in gas temps.
My thinking is that, while it is nice to know the temperature of the cylinder head at any given time, that by the time that huge chunk of metal heats up and gives off a reading, could it be too late for the piston, rings and bore?
And, with that delay, can you get good readings of say, an uphill run in third at full throttle, to ensure that the main jst is properly sized?

[nelson pk]

Not sure on that one Eden. What EGT are you running. If you still have power to the EGT i'd say its got to be a sensor issue. When my sensor packed up it just read zero. Hope that doesn't mean your sensor's dodgy! Do you run a battery with your EGT? They dont seem to run well off these regulators that advertise running dc without a battery.
Cheap sensors fail quite regularly from what i heard. I bought a quality one for my koso EGT after the standard one failed after a few months and its now been in there for about 3 years and i've had the exhaust on and off a few times and its never let me down.

[Adam_Winstone]

I spent my time watching my EGT from home to Brittany and Belgium, then back home, and loving the feedback that it was giving me. I was thinking how it was very reliable and then all of a sudden it started giving extremely low readings, almost not reading on the scale. Then it occurred to me that it was raining heavily and that this might be the cause, even though I struggled to get me head around the temp of the gasses leaving the cylinder being cooled that rapidly. Sure enough, as soon as the rain stopped it went back to giving the normal running temps.

My EGT temp shows sub 500 when around town (probably even sub 450), shows around 600 under normal running conditions, but will nudge 700 if I cruise for long distance at 1/3 throttle with slower bikes. Open up to half, or vary the throttle range/position and I can get the running temp to quickly drop back down to the 600 mark.

Adam

[nelson pk]

Totally agree with the 1/3 throttle high temps Adam. This is why the EGT is excellent as it shows the danger areas and i have always found on Lammbrettas that the danger area when cruising is between 1/4 and 1/2 throttle.
I think this is why a lot more tuners are using the largest atomiser they can get away with and then reducing the main jet size to get less splutter at low revs (as long as its safe to do so of course). This is where power jets help significantly but they can be a minefield to set up properly.