Always wanted to post this but keep on forgetting, so now I finally am. I have a 01 road King with the Magnetti Marelli EFI system. I have built a pretty stout 95" that has awesome power. I noticed that when the bike is started up, at cold idle/not warmed up all the way, the bike seems noticeably faster/quicker/better acceleration etc. I know, it sounds wierd...

Dont get me wrong, I don't start the bike up and immediately pin it or anything, I let her warm up but taking off in first gear and so on. When "cold" the bike deffintely seems quicker, when the bike "knows" when it's up to operating temp, it's still fast, but not as fast then when it was "cold."

Maybe it's in my head? But I deffintely don't think so. Maybe on the cold idle circuit more fuel is being added? I have a power commander and know some stuff about tuning.

So the question is, what can I do to make my bike feel the same when "cold" as well as up to temp? I have the accelerator pump feature to where I like it and I truly don't believe it's just my butt dyno. It's not a night a day difference, but deffintely enough to complain about it on here. Any input is appreciated! Thanks

 

You might be onto something. My other passion is boats. I don't know about Harleys but I know for a fact boats, especially fuel injected boats, run faster in cold air because cold air atomizes the fuel more efficiently than hot air does. You notice a lot more with a boat since you're running WOT most of the time and you can account for every mile per hour on GPS. I expect the same principle applies to a bike or a car, which is why high performance motors run cold air intakes.

 

I think the OP is actually referring to engine temp not ambient temp. I've sometimes wondered the same with my bike and put it down to extra fuel during warm up. But mine is Delphi FI, I'm not familiar with the mm system at all. And I've also wondered if timing is affected during warm up. Again, not sure. Hopefully one of the pro's chime in!!

 

While the engine is cold all metal did not expand yet due to low running temperatures. Therefore the tolerances are at minimal creating tighter sealings with between cylinder housings and worn pistons. Also the cost could compression will be momentarily slightly higher until the engine is at running temperature. All this together results in the feeling of having more torque with a cold engine. It's not recommend to push it to the edge while the engine is cold as the engine is not in the running tolerances. Though I used it when I had to short races with a 2 stroke engine on my small bike when I was 16 years old. 😀 The difference is even more noticeable with a 2-stroke. You can use this to your advantage.

 

That deffintely makes sense about the metals expanding and what not. Anyone have any other theories? I knew I wasn't the only one who thought this! Haha