After I installed just a full exhaust with 2" baffles my bike ran like crap. Got a Stage 1 air cleaner and tuner and now the bike runs great and is cooler to boot. The factory tune may be able handle an air cleaner or slip on exhaust. But it won't handle many full exhaust systems or Air cleaner/ slip on combo.

 

One is an 06 Dyna, and the other is an 08 Softail. The Softail is the one that was checked on the dyno.

"Cruise" averaged around 14.6, and full acceleration was around 13.

There are cooling benefits to spraying more fuel (latent heat of vaporization), but also some downsides, like fuel dilution of the oil film on the cylinder walls. Our modern lean-running engines are some of the most long-lasting ever.

Sometimes, cooling with excess fuel is necessary, like with some supercharged or turbocharged engines, where we might run as pig-rich as 10.5:1 under full power to suppress detonation. Wouldn't recommend it on a normally aspirated engine, if one cares about engine life.

A little misinformed. Modern engines are designed to run hotter and leaner. Heat isn't necessarily an enemy. It's also a friend of power and efficiency. Heat is what produces the expansion in the cylinder, which pushes the piston down.

And opening up the intake and exhaust doesn't necessarily make a computer-controlled engine run leaner/hotter.

 

Certainly, modern engines. The HD Twin Cam is based on a design from the 1940's though. Plus, it's air cooled where the only way to regulate the temperature is via A/F ratio and an oil cooler.

 

Again, a little misinformed. The HD Twin Cam is a modern design, with some compromises based on emulating the appearance and sound of earlier engines.

One example:
The combustion chamber on the Twin Cam is a totally different design from the Shovelhead and Evo. Not only is it capable of making more power, but it's also cleaner and more fuel efficient.

Temperature regulation is in no way limited to A/F ratios and oil coolers. The Twin Cam has more cooling fin area, and also has rather sophisticated heat management strategies, including limiting oil flow to the heads (which tend to heat the oil on an air cooled engine) and rear cylinder shutdown during extended low-speed operation.

 

Damn Skippy, this is some funny ****.

 

Ok, so I am going to step in on that comment. You are completely and utterly wrong.

One, modern engines as you call them, run hotter to burn off excess hydrocarbons due to EPA emissions.

Two, heat does NOT expand the cylinder, dumbest thing I have read by the way, nor does it push the piston down. What pushed the piston down is called combustion there genius.

Why would a cylinder expand? So you could have blow-by in the cylinder? Jeez.....

Also, you said elsewhere that a richer mixture would get into the oil and cut the lubricstion on the cylinder walls? You are a complete moron. RINGS scrape the cylinder wall of oil on the downstroke so it does not interfere with combustion.

I don't usually get into pissing matches on here, but Warp Factor, you are perhaps the dumbest person I have ever met. That is really saying something.

 

LOL, reading comprehension can sometimes be useful. Note that I didn't say heat expands the cylinder (although it does), but that heat is what produces the expansion in the cylinder, pushing the piston down.

LOL again. The reason combustion pushes the piston down is that it produces heat, expanding the gases in the cylinder and raising the pressure. If there was no increase in temperature, there would be no increase in pressure. Combustion doesn't insert magic-force pixie dust or anything. It pretty much conforms to basic gas theories, where pressure or volume increase with temperature.


The rest of your post is even less worthy of comment. But if you want to come back and make your other contentions, one per post, I'll try to do a decent job of addressing them one by one.

 

Darn I didn't mean to start a war. I do have Vieds that I am installing, I was just wondering what everyone thoughts where by what the mechanic said.

 

You have gotten all kinds of advice...dunno if it is more or less confusing for you now.

Once you have your free flow intake and exhaust installed, you should be able to tell if it is running well, or if it is surging/not running smoothly due to being too lean.

From the responses, you can see that some do not run poorly when a free flowing intake and exhaust are installed, and others do.

If you do experience it running poorly, here's a link to a thread with an overview of popular options-

https://www.hdforums.com/forum/ignit...uning-etc.html




Thanks for the hard numbers. Without them it is not possible to have a productive conversation.

Can't comment on the 06 since the AFR is unknown. On your 08 I hesitatingly agree with you that 14.6 in cruise and 13.0 in full throttle is borderline acceptable...It is higher than I would want to see, and higher than what, in my experience, produces the best power, smoothest running, engine.

I prefer to see it down around 13.8-14.0 in cruise and 12.5-12.9 in WOT.

In the years since 07, HD has been creeping the AFR higher and higher...so some of the conflict in some of the responses is probably from guys with newer bikes, that have a stock calibration where in cruise they are seeing 15.0 - 15.3 or even higher. That is TOO lean, I think you would agree to that.

My bone stock 2012 Softail came from the factory with a tune that put the AFR as high as 15.5:1 in cruise, but it did drop all the want down to 12.7:1 in WOT.

Simply by getting the closed loop AFR to 14.0:1 made a very noticeable improvement in performance.

I agree, going overly rich is a poor way to cool the Twin Cams.

 

So many make this mistake. You can get away without a tuner but your bike will NOT run at it's peak performance. I agree, $100.00 an hour on a Dyno is a small price to pay for many years of riding and at peak performance.