Tested out the Fresh Air Exhaust and ......WOW

I recently installed the Fresh Air Exhaust system in my '02 Malibu VLX and tried it out for the first time last night. All I can say is WOW.

It sounds like I have a stern drive now. I can hear the tower speakers a LOT better while riding.

Anyone familiar with the loud rumble from the engine when you're cruising really slow but just fast enough that the exhaust is out of the water? Well, I can cruise slow now and carry on a conversation.

If you don't know what the Fresh Air Exhaust is all about, go to www.freshairexhaust.com

Good deal...How much do they typically cost?

I don't see the need for that, CO is a gas, when a gas is in the water, it rises up and bubbles out, it might smell a whole lot better but i think the co is still there. plus the power loss, that thing has to put out so much back pressure on the engine

elias, you may be right about your chemistry facts, but you're missing the point. With the FAE, when the gas rises up and bubbles out of the water, it's 60+ yards behind you, instead of in your face poisoning you. And strictly speaking it's not "necessary", but it sounds like a really nice option to have on your boat to me

I can't understand how you will get power loss. Please explain. The pipe is not that small.

Power loss will happen. And, power loss will cause a loss in gas economy.

not sure, but I'm thinking that turning 2 pipes into one at the end, probably effects power.. even if the one is big, it's probably not as big as 2 seperate pipes.

The nautiques only have one pipe out the back and I don't think that really causes any power loss. The only thing I can see is the extra drag.

Power loss totally depends on the system. I have built and tuned several exhaust systems on a dyno for all sorts of things from, motorcycles, sand rails, dwarf cars, pro modifieds, diesels, turbos etc. and everyone is different. The shortest, biggest exhaust system is not always the greatest. On a lot of engines the more back pressure at the right rpm equals more horsepower or torque. Tube length also makes a huge difference. On a typical boat engine, it would most likely not make that much change in power/torque or economy.

It's not like we are running the 1/4 mile in our Nautiques either!

Compare the size of your boat exhausts to your truck. They are both probably V8 engines.

The fresh air exhaust is not small enough to cause any appreciable restriction in flow of air.

I don't think it is a issue of back pressure. It is an issue of exhaust gas temperatures. If the exhaust gas cools too much before leaving the exhaust, it will slow down. That is why my car for instance will perform better with a 2.5 inch exhaust vs. going to a full 3 inch system. The 3 inch system allows too much cooling for the amount of exhaust I am pushing. Remember your engine is just an air pump. It does not matter how much gas you give it, because you air limited in your air fuel ratio and the limit is usually your ability to get air flow through the engine.

A cooler gas is denser and as a result can flow faster as a whole since it's a dense body instead of a loose body. Either way the only real concern about how cool the exhaust gas is, is to keep the exhaust valves at a good operating temperature. If they get to cold they will eventually seize and burn up from friction heat. This is why you still run some type of exhaust manifold or header on an demo derby car engine, so the valves don't suck cold air.

Cooler exhaust gas is not the reason why your car runs better with a 2.5 vs. 3 inch system it's most likely a result of back pressure or lack thereof and a cam with lots of overlap in it. If you don't have enough back pressure to keep the unburned gas and oxygen in the cylinder it just goes right by exhaust valve. You have to have some back pressure built into the system to slow everything down long enough burn the good gas and air in the chamber. On a high performance motor you can shut down the exhaust valve sooner and therefore run a bigger exhaust (very simplified). Change the cam and that baby will run very nicely with a 3 inch system if it runs now with a 2.5 inch system.

I have often heard of the old "your engine is just an air pump" and it's not just an air pump! It involves thermodynamics and combustion while "just an air pump does not". True your engine is only as good or efficient as the amount of oxygen it can get in the combustion chamber and then co2 out of the combustion chamber but it's much more than an air pump. Jeez, I guess I did learn something getting the Mechanical Engineering Degree from ASU after all.

I don't know if you guys have been the FAE site. Larry Mann has some really good data on the web site. The claim is that you lose 1/2 to 1 1/2 mph off the top-end, I don’t think that I’d miss it. I surf a lot and think reducing the CO level would be worth it.

Above Elias says that CO “..might smell a lot”, but I think he really is talking about the smell of the other emissions, CO is odorless. At atmospheric pressures there is some air “dissolved” in water about 5 ml of O2 per liter of water. Fish tanks have aerators to keep the O2 level up in the tank, otherwise the fish would suffocate. Some fraction of the CO might also dissolve in water with the FAE, but I do think SeaDawg has it right, most of the CO shows up 60 yards back.

While you’re underway the down pipe gets dragged through the water. If there wasn’t exhaust gas coming out of the down pipe a vacuum would develop behind the down pipe. I suspect that the vacuum helps you engine exhale and offset the loss of power from dragging the down pipe – just my WAG.

See the report on the effectiveness on CO reduction, pretty impressive work.
http://safetynet.smis.doi.gov/fae.pdf

So can you teak surf if you have one of these things? (assuming it was not illegal)

So lets see, an engine pulls in air and mixes it with fuel, it burns the mixture and then the air and spent gases are pushed out. Basically, It's an AIR PUMP!

Man, you guys are getting waaaay to technical! I'm a Mechanical Engineer and have looked pretty extensively into Fresh Air Exhaust because I wanted to make sure it wasn't going to harm my boat in any way.

Well, I bought one. And it works, period. I will probably lose 1 mph at top speed, but I board at 22mph, so who cares? I also wakesurf and want to breath fresh air. And the most important aspect for me is that it makes the exhaust quiet, resulting in better conversations and less power to drive my tower speakers.

I had two friends with me, when I tested it for the first time, and they are now set on getting one for their boats.

Tuneman, do you have a wakeplate on your VLX? How about some pictures of the setup? I want to get one for my boat as well and I am willing to lose 1-2 miles an hour on the top end as well.

Yeah, I was wondering if it physically interferes with the wedge?

I think is a cool Idea. I was wondering how does the thing not get ripped off. It dosent look like its attached with a whole bunch of hardwear. The guy at FAE said that the water behind the rudder (where the FAE mounts) the water pressure there is much less than in front of the rudder & that the water behind the rudder is airated and thats how the FAE can pass threw the water easy. He said that the water back there also works in a way that it sucks the exhaust from the pipe kind of making up for the reduction in tail pipe size.
FAE told me they had no information as far as exhaust gas temp's with a FAE installed for my and other boat's. My mechanic is very consertieve when it come's to this subject and when I told or asked him about it, he about shat him self and told me it was no good dont do it bla bla bla, so that sort of discouraged me in doing anything. I would like to check one out

My friend put one on a 94 sn with the single 4' exhaust and he said it was worth the money. He had no noticeable loss of power. It did reduce the noise level in side the boat a bunch.

im getting one for a 06 xlv, this week

Real men want loud tunes AND a loud motor!

Mark do have the wedge? I have been waiting for the ability to use the wedge and have FAE at the same time. Mike}

im picking out a boat today at atlanta marine, and should be on lake sinclair in a week. yes it will have the plate

The FAE can be mounted on boats with trim plates, but they haven't made one that fits around the Wedge yet. I don't have the Wedge on my 'Bu.

my fae will be in thursday to install on the new xlv for this weekend