| Author | Message | ||
     Littlebuggles |
Well the manifold is off, and like any other part I remove from the bike I am considering polishing it. A search only turned up four actual references, none were definitive in any way. Just the intake tract, mind you. Is there any point to it? Will it net an improvement to power or fuell mileage or shall I just put in the new seals and be done with it? Stock carb, re-jetted, stock airbox with K & N filter, race ignition module and V & H pipe. Some day, if the engine needs a rebuild it will probably become a 88". Thanks, Mike | ||
| Bluelightning |
If you have the intake off, you might be better of getting the Screamin Eagle big bore intake for Sportsters. It will allow you to upgrade later on to a bigger carb, and will net you better results than just polishing the inside of your stock style intake. The big bore intake comes with 2 different gaskets so you can run the stock 40mm carb or go up to the bigger CV-44 carb. Coast at the Harley Stealer is around $75, so not too bad on the wallet. | ||
| Ara |
Polish the outside if you like, but do not be tempted to polish the inside to a mirror finish. If you do you'll ruin the part. Just remove the casting flash and smooth any rough places you find on the inside with medium-fine grit. If you actually polish the inside, the surface will attract beads of liquid fuel - a bad, bad thing. | ||
| Littlebuggles |
Thank you. I wonder if the Buell race manifold is the same as the Screamin Eagle part? There was a ring of carbon on the front intake port where the manifold meets the head. Is this fairly normal or indicative of anything in particular? The rest of the intake track (tract?) was pretty clean, valves are looking dirty with carbon, 'bout 15K on the bike now. -Mike | ||
| Bluelightning |
Not sure about the Buell part. Sorry about my last, I didn't mean to polish the inside completely smooth, you need some roughness to grab the airflow and keep the fuel suspended. The carbon on the inside of the intake and valves is probably from oil puke that is fed back into the engine through the stock breather setup. Best way to prevent that is to route the breather setup to a catch can and keep your intake system for just fuel and air. | ||
| Djkaplan |
I'm wondering if a polished outside surface would lower the intake temperature? The smooth finish would minimize surface area and could reduce heat transfer from the cylinders (convection and radiation). | ||
| Ara |
DJ, that's an interesting question. I wonder if insulating the manifold increase intake charge. I've insulated the fuel line because it runs between the cylinders, but I hadn't thought of insulating the manifold. Has anyone some wisdom on this? | ||
| M1combat |
Four wheel drag racers typically polish the bottom of the intake manifold... | ||
| Samickguy15 |
Polishing the outside of the manifold would effectively increases the heat held in the intake due to less surface area for disipation. Most of your heat will come from the head and into the intake. Looking at my TB from a '99 S3, I can't see any reason to not polish the outside. It's pretty much smooth as is. I can't really see much benefit either way since you don't see much of the intake anyways... | ||
| Djkaplan |
"Polishing the outside of the manifold would effectively increases the heat held in the intake due to less surface area for disipation" Sorry for the late response... but this is incorrect. If everything around the manifold is hotter than the manifold, increased surface area will just make the manifold hotter, not cooler. Polishing the manifold will decrease the amount of heat transferred to the manifold by convection from the hotter surroundings. You also have to take into affect that the manifold is further cooled by the incoming fuel mixture. The manifold is always cooler than the cylinder heads; heat will only flow one way. I'll wait for the response. | ||
| Ridrx |
Makes me wonder if all the polished frame guys are gettin' a cooler fuel charge? If the tank/frame is reflecting away most of the heat, the the fuel should be cooler, no? | ||
| Kilroy |
I'm pretty sure that the heat transferred to the intake via conduction frm the intake ports on the head is the main pathway of heat into the manifold. I would guess that the air surrounding the intake would always be cooler than the manifold, not hotter, meaning that heat would always be flowing away from the manifold to the surrounding air. If the manifold were receiving heat from the surrounding air, it would have to be cooler than the air, and it would feel cool to the touch. I don't think that is the case, but I have never touched my manifold while the bike is running. Seems to me, not polishing or insulating the outside would be the best bet from a heat reduction standpoint. | ||
| Djkaplan |
The air surrounding the cylinder heads is pretty hot. Buell used to market an auxillary fan to draw cooler air to the backside of FI units to keep them working in extremely hot, low-speed conditions. The surrounding air wasn't cooling the manifold enough with the bike stopped, or barely moving. I suggest you touch the manifold after a long run on the highway, or better yet, hit it with temp sensor. Everyone always neglects the cooling effect of the atomized fuel that's constantly cooling the manifold from the inside. As far as conduction from the intake side of the heads, the intake gaskets act as thermal breaks, which further slows heat flow. Convective cooling from the inside of the manifold will always make it cooler than the ambient air unless the bike is stopped with engine running and letting the engine heat soak. |
