[1pcbr]

I hope this isn't a stupid question...

If I make several runs at the drag strip, how do I know when and how long to stop and let things cool off? Sometimes, I can make a run every 3 minutes. I guess the clutch needs to cool off after 3-4 runs.

I'm not sure how much it helps to shut the engine off because then the oil and water aren't circulating.

[Getsome]

Personally at the strip here we usually have a minimum of 5-10 minutes between runs. If you get there right at the start of the night you might get 2-3 right after each other but once people start showing up there's a wait.

Most of us usually shut the bike down when we get to the staging area unless the heat is up and the cooling fan is on in which case i shut the motor down and let the fan cool the radiator for a minute or two then shut it down. Once you start back up the temp will drop a bit to normal range....

Just keep an eye on your temp and keep the bike off till ready to run is how most everyone does it here.

Never had any clutch problems so I have no real comment on the clutch needing to cool down....

[Smitty929RR]

Here it seems like we have to wait 45 mins. between runs. I usually start it up early to make sure it's back up to temp and the clutch is warmed back up. Other than that I just try to lean it to the right to make sure the clutch gets well oiled, before we go out to the staging line.

[SilverBullet]

Depends on where I am at. I normally dont like to make more than a couple passes in a row before I let the bike cool down. This weekend we had a big event, I would run Pro Et class then have to come right back around to run Street Et class....I lost 1.5-2.5 tenths between those runs so I couldn't get a consistant dial in. I will run within .05 of my last run if I let the bike cool down to 140 or less. I also have 3 fans on the bike between runs to help it cool down.

[saf]

Cool down has two distinct definitions in a modern sport bike engine, 1) Water jacket temps , 2) Engine oil temps.

Water temps recover a lot quicker than oil. A while after you have rolled off the throttle , the exhaust valves, guides, shims and buckets on the hot side, along with the cam that transfers heat, are all still really warm, and the oil does 2 things, lubricates and actually cools. Engine coolant temps however are based on how much power and what EGT (exhaust gas temp) temps your running at that particular time. If your on WOT and making 180hp at the crank for eg, (BHP) you have 180hp of heat getting absorbed into the cooling jacket. As you cross the line, the engine shuts off, and the cooling system can recover as the tems are now 1/10th of what they were in he top of 3rd for eg.

Having said that, the worst thing you can do right after a run is shut it down, thinking that it will cool off sooner. The hot head can promote localised boiling and dump coolant, while oil can sit above the exhaust valves and "coke" where the oil burns and cakes up. Riding it back down the return chute (? , the access road to get back to start line) in 1st gear just above idle is a good way of getting a little air in, and having little to no load on the engine to recover, both oil and water. By having low EGT the oil system recovers, and if there isnt enuf air, the water system will fire up the thermofan (s).

As far as clutch cooling, its a wet clutch and only temp related to the direct oil temps as its a shared oil between the clutch and the engine. Giving it a 20 second idle, switching it off for a few mins and then giving it another 10 second idle to start up the waterpump, and flow the water in the head away from now the cooled water in the rad, to stop localised boiling and cool off quicker goes a long way. On my VTR it can jump as high as 9deg in one hit, when the bike is started after a few mins, it will go from 99c to 90c in that first 5 seconds , at what point thereafter you shut it off.

Hope that helps. Im a tad paranoid, its the years we have worked with turbos and dislike what happens to them when they arent cooled off .... you can however apply that to high perf bike engines too .

[1pcbr]

Thanks everyone.

[cbr929_son]

Originally Posted by saf

Cool down has two distinct definitions in a modern sport bike engine, 1) Water jacket temps , 2) Engine oil temps.

Water temps recover a lot quicker than oil. A while after you have rolled off the throttle , the exhaust valves, guides, shims and buckets on the hot side, along with the cam that transfers heat, are all still really warm, and the oil does 2 things, lubricates and actually cools. Engine coolant temps however are based on how much power and what EGT (exhaust gas temp) temps your running at that particular time. If your on WOT and making 180hp at the crank for eg, (BHP) you have 180hp of heat getting absorbed into the cooling jacket. As you cross the line, the engine shuts off, and the cooling system can recover as the tems are now 1/10th of what they were in he top of 3rd for eg.

Having said that, the worst thing you can do right after a run is shut it down, thinking that it will cool off sooner. The hot head can promote localised boiling and dump coolant, while oil can sit above the exhaust valves and "coke" where the oil burns and cakes up. Riding it back down the return chute (? , the access road to get back to start line) in 1st gear just above idle is a good way of getting a little air in, and having little to no load on the engine to recover, both oil and water. By having low EGT the oil system recovers, and if there isnt enuf air, the water system will fire up the thermofan (s).

As far as clutch cooling, its a wet clutch and only temp related to the direct oil temps as its a shared oil between the clutch and the engine. Giving it a 20 second idle, switching it off for a few mins and then giving it another 10 second idle to start up the waterpump, and flow the water in the head away from now the cooled water in the rad, to stop localised boiling and cool off quicker goes a long way. On my VTR it can jump as high as 9deg in one hit, when the bike is started after a few mins, it will go from 99c to 90c in that first 5 seconds , at what point thereafter you shut it off.

Hope that helps. Im a tad paranoid, its the years we have worked with turbos and dislike what happens to them when they arent cooled off .... you can however apply that to high perf bike engines too .

Very informative!