Help w/understanding EGT readings

[RckyMntnKng]

01 800 Gen II RMK.
Installed Koso dual egt's, water temp, tach on her before the last wknd ride.

There are too many mods on this sled to use a jetting chart, so have always done the standard tuning - Look at the plugs and piston wash. Visual checking showed me wash a tiny bit to the rich side rather than lean. Plugs are cardboard brown etc.

Well my egt readings are throwing me for a loop ?!? They are installed correctly, 6" exactly from the skirt, both sides on the twin CPI's. The ride was kinda on the low end of the elevation range I usually ride.

Long story short - babying the throttle I was at around 1000 deg, in the midrange I was consistantly over 1300 deg and even up over 1400 deg. As i got to the real riding and opened her up at some elevation I was looking good at around 1250-1300.

WTF is the deal in the midrange readings? Seems like you could burn down just cruising up the road to the mtn....

Thanks in advance! - RMK

 

[Jkinzer]

your mid range readings... were they just cruising down the trail mid range, or on and off the throttle in the trees, up a climb mid range? cruising down the trail if a guy holds the throttle in the mid range on any heavilly mod'd sled you will see 1300+. as long as you are in the 1250-1300 range while in a real climb or real riding situation, not just going down the trail than you should be good. just make sure you vary your throttle positions going down the road and try to keep it under 1300

 

[RckyMntnKng]

Well there was about a 8-10 mile trail ride up to the base of where you really start to climb up. There was about 4 of us just cruising up there nicely to get everything warmed up.

I was holding her at one speed mostly about 25-30 mph when I saw the temps. If I gave it a little more throttle it was too fast for the corners and went up to 1400deg, when I let off to get it under 1300 deg I was too slow to keep up. It was kinda annoying and just wished I didnt have gauges at that point lol. We were fighting some lack of snow down low as well, having to run the scratchers

 

[RckyMntnKng]

I forgot to mention, this sled is new to me so Im not completely up to date yet on what exactly she should sound and feel like when running perfect. Have to spend some time getting to know her and what she does and doesnt appreciate.

I came off a modded 03 rmk so Im familiar with what they run like....barring the chassis difference between the 2.

This 01 is incredible though...man the front ski's never touch the ground on a climb. Could wheely over backwards if you wanted. Made it kinda interesting in the dodging trees type of climbs, would need to slow down to be able to steer.

 

[Daggerboat]

X2 what Jkinzer said and I like to watch the water temp when cruising in the mid range....If I'm getting proper cooling and cruising under light load (25 MPH) I don't worry about holding my '02 800 at EGT's above 1300....Not likely to transfer any aluminum under those conditions....But an '01 Mod may be different ?

 

[polarblu]

wow you guys run hot!! i personaly like 1000-1100 degrees on my 900 cat.
it is nice and crisp and nice and safe. Plugs are a little darker but gas is cheaper than pistons!!

Aluminum melts at 1340!!!

 

[polarblu]

If its happy over 1300 degrees there is a good chance you are actually burning feul in the pipe!!

 

[Daggerboat]

I can hold my '07 600 for miles at 1450...Just because the exhuast gas temp is above 1340 that doesn't mean the piston is that hot....Like I said in the earlier post , coolant temp and engine load need to be considered when watching EGT's

 

[F-Bomb]

Temps mean nothing until you associate that read out to an RPM duration and at a given load. ONCE AGAIN THE NUMBERS THAT YOU ARE SEEING MEAN ABSOLUTELY NOTHING UNTIL YOU'VE ESTABLISHED A BASELINE FOR YOUR ENGINE AND YOUR ENGINE ALONE. Also note the overall color condition of a plug means nothing as well. There is extensive information on a two stroke plug but you need to know what to look for and it requires a magnifier and a light for all of the details. Go to www.f-bombracing.com and look at the DIGATRON TECH PAGE for the exact information that you need to continue.

Also note: You will lean seize that 800 motor in a short time running it overlean at mid range for extended periods at consistant RPM. Be busy on the throttle irregardless of your temps and at all loads (except full throttle obviously).

 

[RckyMntnKng]

Thank you for all the advice and things to consider, it really helps!

This is the first time Ive ever ran a gauge on a sled, and I havn't burnt one down since I was 12 years old on a 340 Txl when i was too lazy to clean the carbs after it sat out all summer.

Ive been reading plugs for at least 20 years on Sleds, Dirtbikes and Jet-skies.
I have always preferred to jet rich and trade the slight performance difference for the piece of mind. I ride the same 2 mtns/elevations all year and only have to dial it in once usually for the life of the sled.

This sled has only 4 rides on it by me personally, and It was already jetted for my elevation/temp. Irregardless I verify that its correct out in the field by checking plugs and wash. I normally associate a ring of clean silver all the way around a pistion, where the top is black - to mean she is conservatively rich.

This one looks pretty dialed in on the wash with silver trails up from the ports, and the plugs themselves I checked multiple times with 1/4 mile bursts/kill switch. I was scared to try it down low because of the temps readings I was getting there.

What can I do to give the midrange some more fuel/oil if anything?

I think i overlooked the part about my water temp intermingling with the egt. Since I had to install a temp probe and drain the coolant, I think i may have not got all the bubbles out completely and she was a little hotter than normal. I will have to do a better job to make sure she is fully Burped.

The sled is incredible though. Only thing thats actually from 01 is the bulkhead lol. Elkholm tunnel and it has a 4" drop and 2" setback, series IV 159, Fabcraft front end with Fox's all the way around, carbs bored, ported polished, delta's, CPI's, VES top, Boss Noss, SlP box, Mtn Fit hood, 8" big inside kit, Team secondary with reverse, Powder Pros Etc Etc.

I cant beleive how nice the approach angle and in the deep pow. I was easily running with a new M8 and Ski-Doo in the deep this year. Wonder how much lighter she is than stock. Feels like 50lbs less than my 03. And yes its still deep, look at the Yellow doo from 2 wkends ago

 

[RckyMntnKng]

f-bomb - Thank you im going to take in all the info for your digitron page.

I agree I could be burning fuel in the pipe...what does that mean or what should it tell me?

And yes....busy on the throttle as much as possible. There does usually come a point when I get to tired and the sled forgets how to turn that I end up cruising on the way home

 

[Spaarky]

I agree I could be burning fuel in the pipe...what does that mean or what should it tell me?

It means that the extra fuel from being rich is being dumped into your pipes and burning there. This gives you a false(hotter) reading.

Trying adding some fuel to your midrange and see if that helps bring the temps down. If not you may be a little rich there too. Just be careful. ALL sleds run hot in the mid range and typically lean. Also remember any fuel you add in the bottom/mid... will be added on the top end too.

 

[RckyMntnKng]

Thank you very much everyone. Wish there was more time this year to play and report on the findings.

 

[Spaarky]

Now is perfect time to be testing ... pow is not the best, so you dont have to waste the over the hood days. I have sure had a lot of good times testing and tuning in the spring.

 

[F-Bomb]

Everyone kind of assumes one set figure is a perfect state of tune across the board but it doesn't work like that. For example: 1300* at 6200 RPM for 10 seconds might be dead on while 1300* for 10 seconds at 8200 might be a disaster. That is why you have to test and read your plugs to associate what these reports mean. Nobody has invented an "automatic plug reader" yet so we have to do this manually and across the board to gain this knowledge. The instrument is simply a gauge to give you something to go from and will save you a lot of time in the learning process. You also have to use your ears, eyes, and the seat of the pants dyno as well. Once you have this experience and knowledge then it's much easier to tune when you need to or also note potential mechanical issues prior to a catastrophic event.

Now once you have it setup and have a really strong idea of what the reports are meaning within your engine you will then see wild reports at certain finite RPM levels. These variations appear to be do to the mechanics of fuel and spark in a carb'd device. It's a circuit of pressurized fuel with the volume controlled mechanically by stacking opening and closing nozels. At some levels in those areas there isn't enough fuel for correct lamda and you encounter a seriously lean condition. Not a thing you can do because adjusting fuel at that point by one of the circuits may negatively effect performance at other RPM's. The answer is finding a nice overall setup and then being busy on the throttle so that you don't stumble on that rare lean position in your circuit and have a failure.

Once again EGT's in the hands of a knowledgable person are an invaluable tool. Applicated correctly you can get a lot of super useful information from it and save yourself hours and hours of field testing. Might also alert you to a potential mechanical problem early enough to keep you from a major issue as well. We've seen problems with h2o leaks show up on EGT reports prior to the total failure and it was nice to know that it was coming.