| Author | Message | ||
     Axl_rose |
hey all. I talked with my guy from liberty harley the other day and he was giving me some bs about how wrapping the exhaust would be "counter productive" and that it would make the engine hotter. I thought that wrapping the exhaust would force MORE HOT AIR out the END of the pipe instead of giving off more radiant heat near the jugs. Whose right here?? oh and did anyone get HD to pay for the header wrap?? what about frame insulation?? if so, how?? thanks always, axl | ||
| Howworkclutch |
yeah they're right. wrap exhaust causes the pipe to hold its heat. header wrap is meant to increase exhaust temps and therefore raise velocity of the outgoing air. | ||
| Dman |
Howwork is right in what he says, but they are wrong in how they are saying it. Header wrap won't make the engine hotter, not in my experience or from guidance I've gotten from engine builders. It benefits the 1125r directly by keeping heat in the tubes so it doesn't radiate as much to the cylinders or frame, none of that makes anything "hotter" except gas in the tubes which is a good thing for performance. Here's a good explanation, not my words - The header wrap keeps the exhaust heat INSIDE the exhaust system and not in the engine bay. Thus reducing underhood temperatures, which in turn does not heat the incoming air charge as much. Cooler denser air = more power. An added benefit is that the hotter the exhaust gases are, the faster they move out the exhaust system - since the same volume of exhaust gas takes up more space when it is hot then if it were cooler. This increases the air velocity and thus the scavenging effect on the cylinders, which means the fast moving exhaust gases actually create a vacuum in your exhaust system, drawing spent exhaust gases out of your cylinders and increasing the efficiency by reducing the pumping losses. So there are two ways header wrap helps make power. | ||
| Dbolemiss |
I have a HMF still in the box that i've been thinking about sending the Y-pipe off to Jet-Hot and get it coated,just not sure if it will mess with the sliding of the header pipe during install. I have the headers on my truck coated by them,very happy with the look and function. | ||
| Puddlepirate |
Coating looks better, but it doesn't reduce temps nearly as much as header wrap, and is more expensive. Header wrap is a pain in the ass on the 1125 if you intend to cover the entire header, and is not as durable as the coating. I have yet to see proof that the header wrap will increase horsepower. Theoretically yes it should, but how much are we talking here, .5hp? Depends on what you're looking for as the end result. (Message edited by puddlepirate on May 07, 2010) | ||
| Ratsmc |
There are a couple problems with this explanation. The first is that it is in reference to cars. Since there is no engine compartment on a bike, the header wrap does little to keep hot air out of the intake tract. Also, while the wrap will keep heat from radiating from the header to the head, it will also store more heat in the header itself which will bleed back into the head through metal-tometal contact - more efficient heat transfer than air. The other important thing to consider is that, while the exhaust gases may travel faster, the scavenging effect mention only works in a specific RPM range and without very precise tuning, that RPM range may not be within the usable powerband. Taking advantage of exhaust gas scavenging requires matching primary, collector and exhaust length to exhaust gas speed. Basically, any gain from wrapping the headers is likely to be negligible if any without spending a lot more time, money and expertise. There are easier ways to get HP gains. Basically, the only reason to do it is for looks. | ||
| Syonyk |
Or heat. Keeping the heat out of the fairings and the frame and my legs is valid. | ||
| 01xjbuell |
I don't post often, but I have done Headerwrap on both of my 1125 exhaust systems I built. The first was just the stock headers, the second I did the stock headers all the way down past the collector and downpipe... Yes, I can "feel" a difference in the heat on my legs, and oddly enough the frame even feels like it never really gets as hot as it used to. It's not difficult just keep the wrap wet as you go and make sure you pull it very tight. Then when you start the bike it will shrink fit on nice and leave no gaps. Nick Oh, first time starting it after it will smoke like the bikes on fire... kinda funny to watch looks of people on the road as you "smoke" past. | ||
| Da_fraemda |
I don't post often, but... dito  An added benefit is that the hotter the exhaust gases are, the faster they move out the exhaust system - since the same volume of exhaust gas takes up more space when it is hot then if it were cooler. I do not understand this. All I know is, that the flowability of fluids will raise with temperature and the flowability of gases will reduce with temperature. Therefore the removal of the off-gas should be better without wrapping. The density should only change, if you have allways the same compression. In a nearly closed system only the pressure will change with temperature. So I agree to: Basically, the only reason to do it is for looks. and Or heat. Keeping the heat out of the fairings and the frame and my legs is valid. (Message edited by da_fraemda on May 12, 2010) | ||
| Dman |
Yea I can't imagine doing it for HP, or for looks. I'm not a fan of how header tape looks, compared to a smooth finish. But for a reduced temp on the legs & crotch, it'd be worth it. I'll be trying it, but when I do it I'm also doing some heat shielding from a kit I got from American Sport Bike, so it won't be a good test, as I'm sure I'll get a cooler feeling on the bike but how much from what will be in question. | ||
| 2r_300 |
I just had the recall wiring on stator done. I added some insulation around gas tank in engine compartment and under gas tank above where the pipe comes out from under gas tank. Then when I was warming up the engine to check oil (less than 5 minutes) the pipe where they come out of the head was turning red. Is this normal? Has anyone else noticed the pipe turning red? I had put the wrap on my bike about 100 miles, and I had the fuel boil in tank. So I removed the wrap. This was before adding the insulation to the tank area. |
