Engine Starving for air?
07-25-2016, 09:16 PM
#41
Registered
iTrader: (1)
Laugh all you want but I actually built a hood around the flame arrestor on one of my boats and ran a 4 inch rigid hose to it and ran it to open air at the side of the rear bench seat. Worked great untill it sucked up a pop can. I then installed two 4 inch pipes to it and ran well with 100% outside air without being preheated. I work with a lot more than ductwork.. Did I log into Yellowbullit?
07-25-2016, 09:45 PM
#45
Registered
Join Date: Jun 2014
Posts: 13
Likes: 0
Received 0 Likes
on
0 Posts
The amount of air flow you need to remove heat given off by the engine is much higher than the amount of air needed for combustion. You can get a feel for this by looking at performance data from marine engine builders like Cummins.
In this case the answer is 2493 CFM. Add the 1140 CFM you need for combustion air and you are at 3633 CFM per engine. Getting over 7,000 CFM into and out of an engine compartment isn't easy, which is why you can see air temps under the hatch much higher than 120F.
I agree with the posters above advising air temp measurements in the engine compartment. When you can keep the temp rise at a max of 30F you are doing well.
In this case the answer is 2493 CFM. Add the 1140 CFM you need for combustion air and you are at 3633 CFM per engine. Getting over 7,000 CFM into and out of an engine compartment isn't easy, which is why you can see air temps under the hatch much higher than 120F.
I agree with the posters above advising air temp measurements in the engine compartment. When you can keep the temp rise at a max of 30F you are doing well.
07-25-2016, 09:45 PM
#46
Registered
iTrader: (1)
07-25-2016, 10:00 PM
#48
Registered
iTrader: (1)
07-26-2016, 11:44 AM
#49
Platinum Member
Platinum Member
iTrader: (1)
I will be documenting what I do and what the results are, including air temp at the air cleaner. However I think it's way more than a temp issue. It would take a little time to have a temp issue cause a problem, but when the hatch would bounce open and closed the engine would instantly react to the change. It was change you would really feel, and at WOT you need a lot of power to feel any difference. I certainly wasn't creating a 15 hp difference.
07-26-2016, 12:42 PM
#50
Many V boats with a windshield I've been in, the air moves backwards (towards the frt) at the rear seat/ hatch.
The shorter peoples hair blows towards the windshield, the taller people may have their hair go towards the rear.
If you sit on the very corners of the rear seat and stick your head out, your hair will go backwards.
And Yeh, I got geaky enough once on a certain boat (and a few cowl hooded cars) to use those air flow direction ribbons .
The shorter peoples hair blows towards the windshield, the taller people may have their hair go towards the rear.
If you sit on the very corners of the rear seat and stick your head out, your hair will go backwards.
And Yeh, I got geaky enough once on a certain boat (and a few cowl hooded cars) to use those air flow direction ribbons .
a sleeve of dixie cups in the cockpit and the go pro pointed as to record what they do might aid in placement and direction
