07 hogs rear cylinder

[BOWB4ME]

ok here goes... i was briefly reading on h-d net something about the rear cylinders cutting off combustion at cruising speeds to conserve fuel, but i can't find it anywhere. i don't remember the details. and no one i mentioned it
to recalls ever hearing about it. does anyone have any further info on this? it was similar to the newer cars that run on fewer cylinders to conserve fuel at cruising rpms. just curious if anyone knew anything.

thanks

I think you misheard. The heat management system will limit combustion if the engine overheats. This is not done as a fuel conservation technique.

Harris

[BOWB4ME]

that could be correct. like i said, i only glanced at it. and didn't get the details. i don't wanna misinform anyone and was trying to find out the specifics. thanks for responding.

[Road Glider]

Originally Posted by Harris

I think you misheard. The heat management system will limit combustion if the engine overheats. This is not done as a fuel conservation technique.

Harris

Agree with that.

[Krayven Sumhead]

The theory is that every other cycle (while 'skip' firing) the engine just pumps air thru the combustion chamber w/o the fuel being added, so on that stroke it's supposed to help cool down the engine. Hard to do with a carb. Wonder if it really works? I rented an Ultra in Las Vegas which went into 'skip firing' mode. My legs were already about medium rare and I couldn't tell any difference as far as the engine temp went, but I sure thought the sucker was gonna stall at any time. I ended up shutting it down and coasting for the next couple of miles. I went passed two other guys on EFI Harleys that said their's had been doing the same thing, only they didn't know about the 'heat management' system. We had all been stuck in heavy traffic around the Hoover Dam.

[angleflights]

Good info on your post, and I believe I will pass on that upgrade, wasn't gonna spend extra $$ any way cause seem like I reduced the heat on my 06 RG by replacing the exhaust with Bassanis 2-1 and SERT>SEAC. But the other day it was 100 degrees here, that temp was for the devil even with my set up.

[BOWB4ME]

yes. finally got the right info on it once i figured out what i was lookin for. the problem seems to be that when the rear cylinder isn't firing ( skip firing) it drops the idle too low, as a result the charging system isn't oprerating either so the ecm adjust the combustion to the rear cylinder to bring the idle back up. which in turn raises the temp again. novel idea i guess. but like everything else just needs to be perfected. apparently the company has been fooling around with it for awhile.

[sblair]

Krayven;
Shutting down the scooter and coasting for extended distances is not good for the bike!!! Why? I dont know but read it in the manual.

[killerbob]

To my knowledge the protection-system have been integrated on all EFI models since 99.

If cylinder-temperature goes above 300F the idle will drop from 1000 to 900
If cylinder-temperature goes above 320F the idle will drop from 900 to 800
If cylinder-temperature goes above 330F the engine will skip 2 out of 8 ignitions to take in cold air without setting it on fire
If cylinder-temperature goes above 340F the engine will shut down !

This will only happen at or near idle

I have tried the whole bunch at a very hot day and a one hour long traffic jam @ less than walking speed. Not very funny having engine shutting down in the midlle of a traffic jam - but the alternative - a destroyed engine is worse !

After that it took aprox 20 miles for the engine to become "normal" again. The HD guys have explained the besides the idle adjustment the EFI will adjust ignition timing and fuel mixtures - adjustmenst that takes time to get back to normal.

[nvsteve]

The 07 bikes do not have a heat management system. If you want it, there is a free download from the dealer. This info is on the pdf file somehere on this forum.