4 Into 1 Exhaust
 

Anyone have direct experience with the RV exhaust offered by the following:

http://www.aircraftexhaust.net/

They claim the 4 into 1 offers higher horsepower, and I would be interested in talking with anyone that might have experience with it. Also curious if there are any fit issues with the 4 to 1 vs. crossover system (I have the Sam James cowl).

Thanks,
Scott

I have one of their 4-into-1 systems on an RV-8 with an IO-360 C1D6.

I am very pleased with it. I have no way to quantify any power increase, since this is the only exhaust I have flown on the airplane.

It is very easy to install, and is self-supporting (no hangers). Many of my friends have had trouble with other systems having to weld cracks, and continually fiddle with or replace exhaust hangers.

Subjectively, it looks and sounds great, and may be worth it for that alone :-)

James Freeman

I've been contemplating the 4-into-1 myself, but wonder about the sound/noise level. I'm trying to avoid straight pipes because they're just too loud for me... Either the 4-1 pipes or the muffler system from Aircraft Exhaust should do the trick I think.

So, do the 4-1 pipes tone down the sharp, barking exhaust note that I hear from the straight pipes? And, since I have a carbureted O-360, will carb heat and cabin heat muffs fit in there somewhere? I like the idea of the of the crossover system with mufflers, but then it starts looking too crowded under there for attaching the heat muffs...

What'cha think?

John
RV-8

I haven't measured it directly, but overall noise levels seem about the same as two other RV-8's I have spent a fair amount of time in. Both of these airplanes have 0-360s and Vettermman crossover exhaust. I think there might me more vibration through the floor than the shorter, smaller tips on the crossover.

The pitch of the noise is definitely lower, and attracts a fair number of positive comments from the airport bums.


I do seem to have a power advantage over other local RVs, although only one other airplane has the angle-valve engine.

I would do it again in a heartbeat.

If you are anywhere near Memphis, I'd be happy to give you a ride and let you listen.

James Freeman

James,

What made you switch to 4-1. I've been flying my -7 for two yrs with crossovers and have thought about switching but don't have a good reason to yet. Also, did you coat yours? I wonder what Aircraft Exhaust Tech thinks about coatings. I know Vetterman discourages it on his pipes.

Thanks,
Tobin

I had several reasons, although my reasoning may be flawed.

My first priority was an airplane that had high dispatch reliability and didn't need to be "babied." I like to fiddle with things, but sometimes I just want to get in, light the fires, and go.

I live in Memphis, and heat is an issue in the summer. Angle-valved engines in particular seem to have a problem on RV-8s, and a real problem with oil temps (c.f. Greg Hale's beatiful RV-8). I reasoned that the 4-into-1 would get the heat out from under the cowl quicker, and didn't have pipes close to the fuel servo. I also used an oversized oil cooler, fed by a 4-inch SCAT from the baffle behind cylinder #3.

This seems to have worked, as my temps are excellent. The worst case I have seen is climbing out from El Paso on July 5, with an OAT on the ground of about 105. The airplane was heat soaked (quick fuel turnaround) and the oil temp was 220 before takeoff. I cruise-climbed directly to 15,500 at 120KIAS, and the oil temp peaked at 227 before easing back down. The hottest cylinder never got over 400. On normal departures, I can climb at Vy to normal cruising altitudes of 8-10K without overheating anything.

I had initially planned to coat the exhaust and considered an augmentor tube. Chris Stepp was receptive to both ideas, and was in fact planning to start offering ceramic coating himself. He didn't get in in place before I was ready for the exhaust, so I hung it without coating. I may send it off to be coated when I take the airplane down for paint.

Many of my friends have had trouble with the exhaust hangers, and have downtime for repairs/upgrades. So far (100 hours) this system has been completely trouble free. It doesn't require hangers.

A relatively minor consideration (for me) was the CAFE foundation report that indicated a slight advantage in power & efficiency for the four-into one setup. Chris claims a small horsepower advantage, but I tend to discount these kinds of claims as they are rampant in the industry and rarely accurate.

James

James
Thanks for your input/info. What you said about the heat is exactly how I've been feeling for two years. I hate all that heat in there during the summer and running those tubes across the front of the engine just doesn't seem good to me. Lots of radiated heat near the starter, alternator, and like you said, fuel servo. I feel the same with respect to coatings although not sure how to make heat muff work if coated inside and out.

Tobin

Huge fan of the products, company and folks that run it, nuff said. 4 into 1 tuned exhaust is a known science and shown to produce the most "scavaging", which means free power. It is also by the very nature of equal length tubes for every jug the most even power produced. There is really nothing NOT to love except it does not fit model A's, due to the nose gear.

They are ok with ceramic coatings, I asked. George

True Believers.
 

As George says, the Four into one has a lot going for it.
Does anyone know why Mr. Vettermann doesn't make one.
Pete.

Well there you have it Bird Dog. Cant use it on your 280mph RV-7A. Maybe you can convert to tail scrapper and go even faster! :)

-Jeff