PDA

View Full Version : What is heat soak/vp


kycat2007
07-12-2006, 01:43 AM
I saw a rumor that Malibu was changing to all catalytic converter for their 2007 models and it was mentioned that they may have more problems with heat soak/vp worse than what it is currently.

What is it and what does it do? Is this something we should worry about with our boats?:confused:

JLeuck64
07-12-2006, 03:53 AM
Cat convertors are going to be mandatory for boats manufactured in 07, not sure if that will be California only or the entire U.S.

If your boat was legal when it was manufactured then it won't need a cat convertor installed. The tighter emmission standards are not backwards compliant.

It will be interesting to see if the engineers get any heat soak issues figured out before these models are released for sale. The first few model years with cat convertors will be interesting to watch for sure!

Heat soak is simply fuel being vaporized in the fuel line, which causes gas bubbles to form. Since our engines need liquid fuel to be pumped up to the engine, they do not run very well, if at all when there is an air bubble trapped in the line. To my knowledge this was more of an issure with older carb engines and not engines that use EFI.

TMCNo1
07-12-2006, 09:45 AM
Heat soak is simply fuel being vaporized in the fuel line, which causes gas bubbles to form. Since our engines need liquid fuel to be pumped up to the engine, they do not run very well, if at all when there is an air bubble trapped in the line. To my knowledge this was more of an issure with older carb engines and not engines that use EFI.

Vapor lock in the fuel lines is a result of heat soak. It can happen with carbs and EFI, but with EFI is is not quite as bad.
Heat soak is when the engine has been running and being cooled by water taken into the engine by the waterpumps. When the engine is shut off there is no cooling taking place and extremely hot parts of the engine then transfer their heat into the cooler parts of the engine and increase the overall engine temperature and heat is also trapped inside the motor cover with no air circulation other than the blower, unless you leave the blower on. When you cut the engine off you may notice your engine temp may be at 150 deg, yet when you crank it after it has set for a period the engine temp. upon startup may be as high as 200 deg. or more and your temp. busser may even sound. Then upon startup you will notice the temp. gauge will the drop to the normal range due to the cool water being pumped in and circulated throughout the entire engine.
You may notice in real hot weather, on cars with electric fans coolong the radiator, that the fans may cut on several minutes after the engine has been shut off and this is due to heat soak of the engine, radiator and trapped heat under the hood and the heat sending units sense a rise in temp. above normal and cut on the fans to cool it all down.

JimN
07-12-2006, 10:12 AM
I assume vp was supposed to stand for vapor lock, which can still be a problem for injected motors if the pump is drawing fuel to the motor from the tank instead of pushing it from the tank, like MC does. Eliminating vapor lock is the reason MC went to pump-in-tank in the first place.

kycat- look for a post here about the new MC motor with cat/o2 sensor and the discussion in that thread.

Leroy
07-12-2006, 10:21 AM
I guess this is more of a problem since cat converters get so hot?

I wonder in actual ski (start/stop) conditions if they get hot enough to actually help things or if it is only "on the bench" improvement in emissions?

JimN
07-12-2006, 10:31 AM
It shouldn't be an issue if they send instructions about running the blower or add some vents in the motor box. It's also possible that it will be encapsulated by a water jacket or wrapped with insulation so contact won't be a problem.

As far as the "on the bench" improvement, I think the biggest improvement will be on long runs under load, especially during acceleration and while going out to the course or just out running around.

M-Funf
07-12-2006, 07:45 PM
It shouldn't be an issue if they send instructions about running the blower or add some vents in the motor box. It's also possible that it will be encapsulated by a water jacket or wrapped with insulation so contact won't be a problem.

Jim,
I was thinking about this as well. Cars have lots of air moving across the engine while boats don't. Additional fans or vents may help, but if the boat is shut off, there will be no air moving through unless the fans keep blowing.

It IS possible to put a heat exchanger around the outside of the cat, but it too would have to be cooled when the engine is not running to prevent heat soak. It also seems counter-intuitive to put a cooling jacket on a part that was designed to get hot to be more efficient...

I think it will be very interesting to see how the engineers deal with this new required catalytic issue...I'll be watchin' :cool:

JimN
07-12-2006, 09:33 PM
They've been developing it for years so I'm pretty sure it'll work. They wouldn't go to market with something like this without a lot of testing. They had a motor on the dyno when I was in Indiana for training classes in 2000 and we talked about convertors in class a bit. At that point, it was still a future thing but Alan was working on it for a while before classes, too.