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Just when I thought that I was completely satisfied with my tune, I bought a Infrared Thermometer gun yesterday and discovered that my rear cylinder is running about 50 degrees hotter than my front cylinder. It's obvious that it should be hotter, but is this much normal?

I've advanced my timing quite a bit in the cruise ranges and my cruise AFR is 13.8. The bike runs great and is getting fuel mileage in the 40's....and it feels like it's cooler than before.

I'm running the rear timing at the same levels as the front cylinder. Should I tweak on the rear timing? Higher or Lower than the Front?

Or leave it along and be happy with the way it runs?
 

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It is normal , as it is an air cooled engine , the rear gets less air flow. The MoCo has a flash download that can shut down the rear at idle to keep it cool
 

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I don't know what's normal but I check mine the same way from time to time and my rear is usually not more than 15 degrees over my front.
 

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kdietz

kdietz said:
Just when I thought that I was completely satisfied with my tune, I bought a Infrared Thermometer gun yesterday and discovered that my rear cylinder is running about 50 degrees hotter than my front cylinder. It's obvious that it should be hotter, but is this much normal?

I've advanced my timing quite a bit in the cruise ranges and my cruise AFR is 13.8. The bike runs great and is getting fuel mileage in the 40's....and it feels like it's cooler than before.

I'm running the rear timing at the same levels as the front cylinder. Should I tweak on the rear timing? Higher or Lower than the Front?

Or leave it along and be happy with the way it runs?

Are you talking 50 degrees (C or F)?

You could offset your rear cyl timing a couple of degrees (if you have the capability) and remeasure the temperature. However, I am not positive which direction you should go (advance or retard). Maybe one of the onsite tuners here could help us out. I have to run the AFR in the build on my bike at 13:5 and am still managing over 40 MPG. What octane fuel are you able to get out there?
-2$en#e-
 

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Discussion Starter #5
50 degrees F

93 octane

Yes, I am able to change my rear cylinder timing....retard or advance?....the TMax forum members recommend -2 timing for the rear, but I understand that advancing timing will remove heat

I'm trying to schedule a little dyno session this weekend...maybe this will help
 

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It is generally considered normal to retard timing in the rear cylinder a couple of degrees behind the front in order to make it run cooler. Now that you have the infrared gun, just set the rear cylinder 2 degrees behind the front across the board and see how it effects it. I think you will find that it cooled it down some.

I have set my rear cylinder 2 degrees behind the front in the cruise range, then 1 degree behind the front in mild acceleration TPS settings and then I'm running them the same in hard accelleration TPS setting. I do that mostly because I want the rear cylinder doing everything it can in WOT situations because they don't tend to last very long in street riding. Most of the time I ride in the cruise areas, so that is where I need the most control over temps.

I have not purchased an infrared heat gun, probably should. How much did it set you back?
 

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Discussion Starter #7
bigbluff said:
I have not purchased an infrared heat gun, probably should. How much did it set you back?
On Sale at Sears right now...last day I think.... for $57.
 

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interesting thread.
im new to the board..sorry to chine in.

i wonder if an egt on each cylinder would help decide if it is cooling air flow or tuning raising the cylinder temp ?
 

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Karl ~ I have played a bit with this on mine & ended up @ -2 on the rear as well. This could help temps a little, but I don;t think yours to radically outa whack.

It will be interesting to see that happens on the dyno & testing the rear cyl retard. I'd get it good & hot, make a baseline run, set to -3, re-run, set to -5, re-run and based on those results make a determination as to where it;s best. If -3 is better, try -2.

Are you gonna so see Jim this weekend, so you can compare to previous phases of build?

One other thought for Saturday is the Police Rodeo is in town. After our practices, these cats are quite humbling!
 

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Discussion Starter #10
Phil, I'm actually going to Piper Performance in North Richland Hills....he has the TMax advanced software and another forum friend...Sniper...is going to be there too....together they have done a lot of dyno work on Sniper's bike with impressive results

It should be interesting to see if my timing is close to what the bike wants
 

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nsw said:
interesting thread.
im new to the board..sorry to chine in.

i wonder if an egt on each cylinder would help decide if it is cooling air flow or tuning raising the cylinder temp ?
Don't you have to tap a hole in your pipe for the probe?:huh: WELCOME TO THE FORUM!!!NSW
 

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kdietz

I would think that 50 deg F is not that much on a single pin crank engine. 93 octane, eh? must be nice.

Just like the others said.. I was thinking it was in the negative direction but wasn't 100% sure. Thanks for reminding me bigbluff. Many people like -2 degrees in the rear cylinder from what I hear. I agree with what the others said, change the rear cyl timing and then check it with the infared gun. Don't forget to let us know what you find out.
 

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kdietz said:
Phil, I'm actually going to Piper Performance in North Richland Hills....he has the TMax advanced software and another forum friend...Sniper...is going to be there too....together they have done a lot of dyno work on Sniper's bike with impressive results

It should be interesting to see if my timing is close to what the bike wants
Be sure and let us know how it goes. I looked at your timing curves and you do have a lot of advance. I'll be real interested in where you end up...given that our builds are similar except for the exhaust. Our cams are not too far apart and we are running the same jugs.
 

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hugie03flhr said:
Don't you have to tap a hole in your pipe for the probe?:huh: WELCOME TO THE FORUM!!!NSW
He's running the TMax with Autotune that already is a closed loop system with O2 sensors mounted in the pipes just a few inches from the exhaust ports of the heads.
 

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I took a week class in thermal cameras. They didn't think much of the hand held guns. I was surprised how hard it was to get a god reading with a camera. Thiought it would point and click. No, need to know emissitivy of the object, black body.

Wrapping black tape on a copper conductor would give your a differant reading.

I have no idea the accuracy of the camera.

But how does it feel? Does it feel real hot to you? And is this your first HD?

Also you say 50 degrees cooler, cooler then what?
 

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Discussion Starter #16
berserker said:
I took a week class in thermal cameras. They didn't think much of the hand held guns. I was surprised how hard it was to get a god reading with a camera. Thiought it would point and click. No, need to know emissitivy of the object, black body.

Wrapping black tape on a copper conductor would give your a differant reading.

I have no idea the accuracy of the camera.

But how does it feel? Does it feel real hot to you? And is this your first HD?

Also you say 50 degrees cooler, cooler then what?
The gun has a laser spot that makes aiming at a specific spot very easy. When hooked up to the TMax software, the gun registers the same temp as the TMax engine temp when I aim next to the spark plug. That's where I aim for my comparisons.

The bike doesn't really feel that hot to me and this isn't my first Harley....I put 84,000 miles on my '95 FLHT and I've put 33,000 miles on my '06.

The rear cylinder is 50 degrees hotter than the front cylinder...measured next to the spark plug....the rear runs 340 and the front runs 290 F
 

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bigbluff said:
He's running the TMax with Autotune that already is a closed loop system with O2 sensors mounted in the pipes just a few inches from the exhaust ports of the heads.
bUT, WHEN YOU TAKE THE O2 SENSOR OUT FOR YOUR EGT PROBE WILL THE TMax STILL OPERATE CORRECTLY??? (closed loop)
 

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I wish mine ran 50 degrees hotter. Mine is closer to 100 degrees. A little better now since I installed thundermax. Havent touched the timing. My 2000 FLH runs about 15 degrees hotter on rear and its stroked high comp. I wanted to keep my 07 stock but the heat was unbearable. I now have supertrapp slipons and thundermax with auto tune. I have tried removing lowers which did nothring. I sure would like to know why they 07's run hot on the rear cyl. There HAS to be a reason.
 

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MarkCrain said:
I wish mine ran 50 degrees hotter. Mine is closer to 100 degrees. A little better now since I installed thundermax. Havent touched the timing. My 2000 FLH runs about 15 degrees hotter on rear and its stroked high comp. I wanted to keep my 07 stock but the heat was unbearable. I now have supertrapp slipons and thundermax with auto tune. I have tried removing lowers which did nothring. I sure would like to know why they 07's run hot on the rear cyl. There HAS to be a reason.
You might try going to the page that allows you to adjust the rear cylinder ignition timing in relation to the front cylinder's timing. Try retarding it 2 degrees and see what happens. I'll bet that rear cylinder runs closer to the same temp as the front if you do.
 

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hugie03flhr said:
bUT, WHEN YOU TAKE THE O2 SENSOR OUT FOR YOUR EGT PROBE WILL THE TMax STILL OPERATE CORRECTLY??? (closed loop)
The TMax will run open loop with the O2 probes removed. Just have to tell it to. When you do that, it will simply run on the most recent map trimming it had already done. It just won't autotune it any more until you put the probes back in and select autotune again.
 
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