| Author |
Message |
John Rigby (24.174.234.56)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 19, 2002 - 10:47 pm: | |
I have just installed a air box drain package on my 4104. What was interseting to me was the factory rep said DDA had conveyed to them the following.
During start up and idle the pressure in the air box was possitive,this does not allow all the fuel going to the pistons to be completley fired and exhausted.therfore it ( an oil looking solution ) which actually is burnt fuel.Gets pushed into the air box and down the air box drains.Once you are underway and the rpm is built up the pressure becomes negative in the air box and all the fuel is burnt and exausted.
I always thought it was oil coming through the air box drains.I also see now why lots of idle is not good for a two stroke.
I thought this was very interesting as with this system they supply two one way valves ( one for each air box drain ) so that when the pressure goes negative nothing is sucked back into the air box.
Has anyone else come across this type of info?
John Rigby |
Geoff (Geoff) (64.1.0.222)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 20, 2002 - 11:01 am: | |
When your Detroit idles it does not burn all the fuel so yes, the excess goes into the the air box and AND the exhaust. I have never heard of "negative" pressure in the air box-- in fact, part of the engine diagnostic procedure is to put a manometer on the air box drain while running it on a dyno to see if the engine is operating correctly--i.e. 8V71-- 7.6 inches of mercury at 1800 rpm full load with allowable exhaust back pressure. The check valves on the air box drains are only open when idleing, when the engine is running harder they close under pressure. Whether this is a good idea or not I'm not too sure. It seems to me it is better to have open air box drains so your air box doesn't build up excess oil and fuel deposits while driving. Anyway, you will never "suck anything back into the airbox" like they told you.
--Geoff
'82 RTS CA |
califbob (199.174.218.99)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 20, 2002 - 10:54 pm: | |
Am I screwing up?
I don't have any drains at all just plates over the air boxes.
Been running that way for a long time, but that dosn't make it right!
Should I change it to drains? Oh, it's a 671T
Bob |
Geoff (Geoff) (64.1.0.50)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 21, 2002 - 10:25 am: | |
Bob-- we are not talking about the "plates" (which are actually refered to as "covers"), but two 5/16" steel tubes that attach to the side of the block using 90 degree brass fittings. These air box drain tubes are mounted slightly lower than the air box covers. Perhaps you don't notice yours because they are plugged up(?)-- everyone reading this should check their air box drains and if nothing is coming out of them (like only air, and not oil, while the engine is running), you need to get a rubber tip air gun and blow the tubes out. I just put the air to the end of the drain tube and blow the crap back into the engine-- this unplugs the air box drain. If you have check valves then you need to remove them before you blow the tubes out and also inspect the check valves to see if they are plugged. |