bouncedcheque

Tom: Do I understand your post to mean that if you have already run with your hatch 2 or 3 inches open, to increase air-flow, and see no rpm difference, that your design would not improve performance? That's the case with my 496 and my boat is very reponsive to changes in HP. Thanks.

bcarpman

Any sources for well designed side vents? Something that wouldn't look tacked on?
thanks

tomcat

bouncedcheque:

If your engine compartment is really well ventilated already then I wouldn't expect raising the hatch to reduce MAT much. A cold air intake may still help since it delivers unmixed ambient air, not warmer mixed engine compartment air, but the effect cannot be as great.

You're making me think about the raised hatch test, and there is one potential complication with it. We can't assume that air flow increases. As was mentioned by a few people on the minimum air vent thread, if there is no positive pressure pushing air into the raised hatch then you haven't changed anything and you could get a negative result. Still a simple thing to do and good tests have to be simple.

Best answer is to measure the MAT with a scanner as you change one thing at a time. If you lower MAT you will increase HP, that is not in question.

ECeptor

When I do any significant work on my engine, I take the top of the back seat out. For sure, that insures ambient temperature air goes into the engine. I think I've noticed a performance increase due to this, but haven't done a same day before/after experiment to prove it. I have raised my hatch to about a 6" gap and it made no difference.

I have been seriously considering adding some flex tubing like is used on my blowers along with some small side scoops to push ambient air into my intake (carb'd 454). Not sure how much it will help, but it might get done this winter if I get really bored.

Here's a question for the group - what's the power difference between:
1) bone stock 496HO w/ dinasuar based engine oil
2) same 496HO with:
a. exhaust manifold turbulators removed
b. synthetic engine oil
c. cold air intake

Any guesses? Consider it to be a 90°F day when the comparison is made.

Cattitude

Does the the 496 have an IAT probe? (intake air temp) if it did, I presume you could check with a scan tool temps at idle cruise and WFO?

It's only a gain if you have high intake temps- 150 seems really high with all the air flowing thru the comparment, but then again I have not shot the deal with infrared so i don't know.

Why not put a small spray bar in the tube with tiny orifices fed with fresh seawater on say a 1/8 line- how much would this cool the intake charge? Evaporation causes cooling right?

I dunno- just thinking out loud.....

tomcat

In my first post I refer to checking the MAT or IAT with a scanner and 150F is a real number from a twin engine boat with limited engine compartment ventilation. Engines radiate around 8% of fuel energy to the engine compartment. I did the calculations and was dismayed to find out the huge volume of air required to hold the temp rise to 15F. That's the attraction of the cold air intake, take a relatively small amount of ambient air directly to the intake. It's simpler than trying to cool engine compartment air.

CrazyCat57

Do you think something like this routed to a outside air vent would be worth doing? It's a 5" dia tube, 454 carb engine 330 hp. E Bay #330045024636.

bcarpman

Argh, I wish I hadn't missed that! Yes, that would probably work very well, depending on how big it actually is and what it looks like inside.

bcarpman

It's relatively easy to fit an IAT to just about any engine. all it is is a resistive element that changes with temperature. Just buy one at an autoparts store, find out what the resitances are at various temps in an oven, then secure it temporarily in front of the flame arrestor and wire an electronic ohm meter to it.

bcarpman

If done PROPERLY, water injection CAN work on a naturaly aspirated engine. The problem is, if you spray just a little too much water you'll lose power. It's hard to get it tuned right without an electronic controler. The temps are not high enough to really vaporize much of the injected water.

Also, just as with a supercharged motor (with much more to gain from water injection), your calibration ends up messed up if the system fails (as most of them do).

On an NA motor, you're better off just getting the cold air intake right.