Nordicflame

Intake manifold...

tomcat

I am amazed by the effect of intake manifold heat being reported. My theory says there is very little time and limited surface area for this heat transfer to take place but I am willing to accept the facts as borne out by your experience. Thanks everybody, now I have to change my theory.

On the subject of cold air intakes, Dave and I have been bouncing this around for a while. Yes, there can be a big increase in air density if you do it right, but you have to be careful that you don't lose most of that gain by restricting air flow into the engine with the piping.

One reason air intake kits work on cars is that car engines have restrictive piping. Do a better job of designing the pipe and you "should" see a gain. But on your boat's EFI engine there is no pipe and no restriction. No matter what you do, a cold air intake on a boat is going to add restriction. Design and testing is the way to reduce this restriction to a minimum. I'm thinking here about boats with no hood scoops. If you have scoops, it is a great idea to seal them to the flame arrester somehow as mentioned above.

This is the design that I am testing on the flow bench next week. Baseline will be the bare throttle body, then throttle body with stock flame arrester, then this layout. I will also test with a water resistant filter wrap.

This is the minimum amount of piping and elbows needed to get the air filter under the gunnels where you can get the first stab at the ambient air entering the vents. I am hoping that Dave will be the guinea pig!

bcarpman

Kind of getting a bit off topic here, but I thought I'd add a bit of experience to the EFI vs. Carb discussion.

Since I worked for GM for 17 years, and had access to all the best equipment available, I always ran EFI in all of my home projects as well. I've put EFI on race cars, motorcycles, street robs, supercharged, turbo, NA, nitrous, etc. I've worked on speed density, mass flow, open loop, closed loop, and even some mechnical FI (no electrons You get the point.

Yes, a properly mapped out EFI system can do things no carb could ever do. Weather and altitude correction, cold start, etc.. EFI is also generally less of a compromise if engineered properly. Since the walls of the manifold are "dry" (TBI or a carb is"wet") you don't have to worry about fuel puddling, and hence can design the manifold purely for airflow without worrying about what it does to the air/fuel mixture. This is HUGE, and cannot be underestimated.

EFI is also essential when working with turbo's or blow through superchargers. I wouldn't even think of trying to do a turbo/carb setup. I tried that once...never again!!

HOWEVER.....It's very easy to get lost in an EFI calibration. yes, you have control over everything, and sometimes it's next to impossible to figure out what part of the calibration is giving you headaches. Yes Merc EFI is tremendously simpler than automotive EFI, but they still have many engineers working many months to produce a good cal.

Also, many people have spent many years developing carbs and their respective intakes to the point where they work pretty darn well. Amazingly well actually. I'll be the first to admit that although some of my home based efi manifolds have done everything I wanted them to, and made more power in a more civilized package than a carb ever could, I've built a couple that couldn't be saved regardless of how much dyno time I spent on them.

Yes, if I was going to build my ultimate "spare no expense" boat motor it'd have EFI, but even with all my experience, after rebuilding my "454/330 on roids" this winter, I'll toss on a dual plane manifold and carb...Just too easy, and I know bunch of crazy electrons won't keep me off the lake in June 07.

Kidnova

I didn't mean to throw the thread OT, or hijack it with my efi/carb post. It is definitely a subject for another thread.

Air ventilation is the topic here, and I find it very interesting and informative.

Nordicflame

I'm in

(I'll be measuring my exact front clearance this weekend)

SB

Tomcat - I believe a huge potential source for figuring out piping to your inlet could be Doug from BG ie: Rumrunner.

They deal with this in drag racing applications all the time. What makes 'sense' sometimes can make you fall behind and vice versa.

Biggest things I can add is:

1) Do not put outside opening in a low psi area. Use some small dry pieces/straps of paper / ribbons or etc that will move with airflow. A good example as many that sit in the back seat of a boat can attest to - their hair usually blows forward towards the driver. Many vortices, and air flow reversals going on.

2) What may not be restrictive in a 10 second 'pull' may be restrictive ocer 30 seconds, a minute, 10 minutes, etc,etc. A vacuum guage tapped in different places will give you the headsup here. A temp guage will also help - some intake pipes can transmit heat pretty well also.

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BTW: This subject of heat may or may not make a decided difference in everyon'es applications. Not one engine compartment / engine build is likely to be like the next persons. A lot of variables here.

But, the more heat you are subjected to, the bigger the difference will be when reducing it.

I'm glad to see all the interest with this subject.

I hope we can have more discussions like this one on other topics as time goes on.

It's a lot of fun.

SB

Outerwears ? They work pretty good in 4x4's and snowmobiles - I'll attest to that ! Blurp, blurp.

Just make sure it does have the water resistant treating - I believe they carry different materials.

tomcat

Yes, this is the best part of the tech section, thrashing a good topic.

Thanks for the suggestions. It seems to me that a lot of new boats have the engines squeezed in pretty tight and vents are part of the styling and may not move enough air. The design so far just gets the filter to the gunnels; how well the vents work in that area is still a question. Ask Dave what he may have to do on his boat.

One thing that EFI does is allow data logging. Anybody with a 496 should be able to check their MAT by borrowing a Mercury scan tool.