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

flyeyes said:

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

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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

he 4-1 pipes tone down the sharp, barking exhaust note that I hear from the straight pipes?

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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

What made you switch to 4-1. (snip) Also, did you coat yours? I wonder what Aircraft Exhaust Tech thinks about coatings

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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

tx_jayhawk said:

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

Click to expand...

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

Heat Muffs

Is there room to put heat muffs on the 4-into-1 in the RVs?

Also, does placing a heat muff on less than all the exhaust pipes alter cylinder horsepower, and therefore smoothness or tuning, by cooling the exhaust pipes differently? I know that there are many non-tuned exhausts with this setup, and I'm guessing it would have an insignificant effect if any.

Is there room to put heat muffs on the 4-into-1 in the RVs?

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There's plenty of room, and I have one the left side, but it's almost perfectly worthless. I haven't yet flown the plane with an OAT under about 28F, but the heater just puts out copious amounts of lukearm to cool air. I haven't yet tried the doorsprings/stainless steel wool etc. because it isn't a real priority for me. It doesn't affect the balance of the cylinders as far as I can tell.

James Freeman

Floor Vibration

Flyeyes,

You may be getting vibes through the floor because the angle your tail pipe exits at is too shallow. I had that problem on my 6 and angled the tailpipes to make a 25 to 30 deg angle from the bottom of the fuse - much easier on my feet. Can Aircraft Exhausts change the tailpipe angle to point a little more down? You also have to be careful not to stick the tailpipe too far out from the bottom of the cowl, as well as increasing drag it loads up the ball joints in the exhaust causing them to wear alarmingly.

Pete

fodrv7 said:

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

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I was wondering the same thing, but I just looked at the Van's webstore, and the description says 4 pipe and crossover systems are available. When you look at the configurations available for purchase, you only see 4 pipe systems for the RV-3 and RV-4. Seems odd he would only make them for the -3 and -4.

I also tried to find a web page for Vetterman, and can't. Does he have a page, or is it phone only? I think I saw a phone number on one of the google hits.

James,

I should have asked this the other day, how much? Their website doesn't show exact price. Just wondering if it's at least competitive with Vetterman price wise.

Tobin

I should have asked this the other day, how much?

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I don't remember exactly, but it wasn't cheap. Around $1100 IIRC, definitely more than the Vetterman.

There is a lot more work in the collector though, and it shows. It appears, to my eye, to be much better constructed than the other 4-into-1 exhaust on an RV at my field.

I do remember it being cost competitive with the other 4-into-1 systems I priced, and I talked to a pleased customer who sent me photos of the exhaust on his RV-8 (Ray Parker? I can't remember his name off the top of my head)

James

Correct on the price. I was told $1099 when I asked about a system for the RV-8. I've sent another email with questions about the performance improvements. Mainly, I'd like to know if this system has been tested, and shown to be stronger, or if it's just theoretically better.

I had the Vetterman's crossover on my old RV-8, and the only complaint I had was the hangers that kept breaking. That's been a few years ago, so hopefully, they've fixed this by now. If not, I'd have to come up with something to use in place of those squashed stainless tubes.

If the 4 into 1 system doesn't use hangers, that's one less thing to worry about. Of course then you'd worry about cracks in the pipes themselves perhaps. 321 SS is pretty strong stuff, and Lycoming's don't really push the limit on temp for it, so probably not an issue.

I'm seriously thinking of trying one of these systems.

Answers Answers Answers

I do not want to speak for Larry's Vetterman but he posted on a Yahoo group he did not feel, in his opinion the 4-into-1 was much better. I don't share that feeling. The thing is he has the X-over system down and sells a boat load I am sure, so I don't think he is going to develop a new design. However the fact is people who have done a before and after, having a x-over and than later switching to the 4 in 1, notice the increased power, prop over revving and of course faster climb and higher speeds.

(Floor thumping)
ON the similar note, FLOOR THUMPING comments are few. I have only heard of one complaint of more floor vibration after installation of a 4 into 1 on a side by side model. First, any RV floor vibrates anyway. My RV-4 shook all the time. If you ask that person who says their floor vibrates more with the 4 into 1, they will say the performance gain was very apparent, so I think it is hard to complain with the gains and don't think its an issue. As was suggested pipe angle, collector length and floor insulation / damping all affect the situation. ON the RV-8 with the narrow floor I don't think it vibrates as much as the side-by-side anyway. The side-by-side has the large flat floor to move. I have a longer stinger (collector) on my custom 4 into 1 pipe. I know the stock off the shelf ones are a little shorter, but at a steaper angle from the belly. I think they did this for looks more than anything. The best collector length is 19.5-30 inches long, which most don't want, but I have a 19.5 collector at a shallow angle. The shorter collector looses a little performance but not much. Really to take advantage of a 4 into 1 you would use a custom CAM, and the breathing would really open up, but even without a custom CAM the 4 into 1 is like free HP.

(X-over, 4 into 1 and 4 into 4)
Larry does make a 4 into 4, 4 separate pipes. This is a cool system and works well, From the Cafe foundation the 4 into 4 separate pipes has some good characteristics, like even or balanced power, low back pressure with some but small savaging. In word it has no bad habits but is not a huge plus. You could do WAY worse, like Y-pipes, 2 into 1 on the same side, with odd pipe length.

(Heat muff)
I found on my exhaust technologies 4 into 1 pipe, making room for a long heat muff a little bit of a challenge. Remember "Tuned" pipe lengths or equal lengths requires some bends and curves. I had custom 4 into 1 exhaust made from a pattern I sent them, which is something they still do. So the way I designed my "Headers" was a little tight (see picture below). I only left room for one heat muff. This was before Exhaust Technologies had the stock off the shelf unit. Now they have off the shelf units and I am sure they allow pipe runs that are stright long enough to fit a heat muff or two. I am sure they have accounted a little better for the heat muff. THE COOL thing or should say the HOT thing is they can weld on studs as an option to the pipe to increase the heat muff efficiency by a huge margin. This is a process they use in aerospace heat exchangers. The impressive thing about this company is they do have high tech aerospace manufacture abilities with stainless steel stuff, for all kinds of certified aircraft applications.

I recommend Aircraft Exhaust Technologies, but I do think the installation is not as compact as the cross over. The cross over is NOT bad but it does suffer one physical draw back. If you measure the pipe lengths, primaries, collectors for every cylinder they very from jug to jug, so you don't have "Balanced pipes". What does that mean. It means the power from each cylinder will not have same "scavenging" and the power from the individual cylinders very. The savaging is there but not the to the extent or timing you get with the 4 into 1. Exhaust Technologies also makes a cross over system as well!! They also have a cool Heat muff/ Muffler (noise) combo. http://www.aircraftexhaust.net/

Click on pictures to enlarge, you can see the heat studs, the "cover" of the heat muff in not installed. I found plenty of room on #1 pipe. I did not really have room for more heat muffs the way I designed the pipes, but you can design them anyway you want. As I said the stock ones look like they used longer straight sections so heat muffs are not an issue.

Thanks guys, I'm learning a lot. Regards, Rudi

Yes, Virginia there is an RV-6A with a 4 into 1 system

You can have a "A" model RV with a 4 into 1 system if you are willing to engineer and build it. Big "if." This RV-6A has a Lycoming O-320 with a custom built four into one mild steel exhaust on it. It sounds real smooth too. The owner loves it. It was built by a gentleman in my local area who now has built four exhausts for RV's on my home airport alone. He does each one by hand and has no ideas to make plans or a jig to manufacture these. He did this just for fun. His newer design on his own RV-6 has the collector facing the other direction he says. It took me a long time to get these pictures. When I see his other system I will post those too.

Cool nice work

arffguy said:

You can have a "A" model RV with a 4 into 1 system if you are willing to engineer and build it. Big "if." This RV-6A has a Lycoming O-320 with a custom built four into one mild steel exhaust on it. It sounds real smooth too. The owner loves it.

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Cooool. I think Exhaust Technologies can make up a 4 into 1 for the "A" model. I think they may be working on an off the shelf version. You can mock up a system using some parts they send you with some PVC pipe and they will make a custom system.

Any way the guy who made these has a real eye and they look nice, please send the never version.

QUESTION on the PICTURES?
Could you tell me what the SUGER jar is with what looks like a scrub pad?
-and-
What the purpose of the metal strap is under the alternator pulley?

George

I used the Sky Dynamics 4 into 1 exhaust on the O-360 rv7

My only problem, which was considerable, is that the tube arrangement conflicted badly with the filtered airbox.

I didn't use vans donut filter and had to build a custom model with a panel filter.

That's only common to a carbed Lyc. Fuel injected may be totally different.

I really like the setup after I finally finished it. I think I just wanted something alittle different than the plain vanilla rv.

sound is fine. Its no louder than the crossover vetterman.

cary r

gmcjetpilot said:

QUESTION on the PICTURES?
Could you tell me what the SUGER jar is with what looks like a scrub pad?

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Looks like an "interesting" oil separator for the crankcase breather. Probably not the best location for a glass jar of that size...

gmcjetpilot said:

What the purpose of the metal strap is under the alternator pulley?

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I was initially thinking a heat shield, but after looking at the 1st and 3rd pics closer, I'm back to wondering about it, too.