4 pipe vs. 2 pipe Vetterman exhaust

Hi all,
I am about to purchase the exhaust system for my -4, and I am wondering what the advantages/disadvantages of the 4 pipe vs. 2 pipe system are.
I am thinking of buying the 4 pipe for a couple reasons,
1. It seems there would be more places to recoup heat for cockpit, carb, etc.
2. Although Van's claims negligible performance differences, the pipes are all pretty close to equal length, which can't hurt.

The only disadvantage I can see with the 4 pipe is more "stuff" in an already tight engine compartment.
Anybody want to weigh in with opinions, i.e. personal experience, with one or the other?

rvbldr3170 said:

Hi all,
I am about to purchase the exhaust system for my -4, and I am wondering what the advantages/disadvantages of the 4 pipe vs. 2 pipe system are.
I am thinking of buying the 4 pipe for a couple reasons,
1. It seems there would be more places to recoup heat for cockpit, carb, etc.
2. Although Van's claims negligible performance differences, the pipes are all pretty close to equal length, which can't hurt.

The only disadvantage I can see with the 4 pipe is more "stuff" in an already tight engine compartment.
Anybody want to weigh in with opinions, i.e. personal experience, with one or the other?

Click to expand...

I spoke with Larry about this very subject when I was choosing. In the end I went with the 4-pipe and have about 20hrs flying so far. Here's my pro/con list:

- definitely more room under the sump (XP-360 Horiz-Induction, FI) for stuff like SCEET/SCAT tubing, throttle/mixture cables
- fairly loud for those outside, although inside it's not bad. Mine have turn-downs on the pipe tips that probably help this. I must add that it was appreciably quieter withOUT the gear fairings/wheelpants, for some reason... (I'd like some feedback from those that have an opinion on that one)

Here are the Vetterman claims that tipped me to a 4-pipe, but I haven't flown enough specific tests to confirm...yet:
- 4-pipe straight -vs- 4-into-1 pipe configured RV appears faster in non-scientific Vetterman testing (actual race RV, compared to itself)
- if I didn't like it, he would exchange it for crossover or 4-into-1 (tugs at my 'experimental' heartstrings)

So - after only 20hrs of flying I like it so far. The ease of installation and installation of the stuff around it is enough for me, for now. The speed stuff is yet to come... I'm still scratching my head on the now increased noise after fairings.

Hope this helps.

4 pipes

I have the 4 pipe system with about 400 hours on it. No problems so far. For what its worth, my 4 pipe stock 0-320 holds Sport Air Race League speed records in its class.

The reason I chose the 4 pipe system was simple. Less expensive and if it did crack it would be easier to remove for repair.

Unless you just want to list all the fancy expensive stuff on your airplane that has little effect on performance you will get the most bang for the buck with the 4 pipe syst. in my opinion. If you have a souped up engine and want every last bit of performance at any cost go for the "tuned" exhaust.

Chris Murphy
RACE 34

I started out with the 4-pipe mild steel system on my -6 simply because at that time that's all Larry offered. When I rebuilt the engine in '95, I converted to the crossover tuned SS system. I sold the 4-pipe system and as far as I know. it's still working today.

Merle - I rang Larry V from the UK wrt that decision, and ended with a 4 -pipe.

His position was with the -4 (unlike the 6,7,9) there was not enough room inside the cowls to make a cross over as he would like it, and therefore it slightly reduces power. I was concerned about the noise, but in fact everyone is telling my -4 has a distictive noise, but is not noticeably noisy.

I also like the simplicity of the 4 pipe and would not hesitate to go that way again.

Cheers,

Crossover to 4 pipe conversion on O-320

Thread revival for a first post question...

Due to a recent in flight failure, a second pipe cracking at the flange, and poor fit around the oil pan (it's literally melting to the exhaust pipe), I'm planning to replace the crossover exhaust on my -4 with a Vetterman 4 pipe. Mr. Vetterman recommended that I go with the 4 pipe setup for the reasons mentioned in this thread, though it will require modifying the cowling. The cowl is currently well fit for two pipes and I'm worried that this will create more problems than it's worth, as I will have to make some fiberglass mods for the four pipes to exit.

The aircraft was completed in 1994 and has 400 hours, but it appears that the current exhaust was never really quite right. I'm still debating whether or not changing the current configuration is a good idea, and if so, what's the best way to go about modifying the cowl?

Thanks!

RV-Four Pipe

Hi Merle,

I bought one of Larry's first 4-pipe systems way back in the early 90's when I was building "The Bandit." (my RV4) He was still living in Denver and making them in his spare time while holding down another job. At that time, Van's stocked the Alan Tolle system which was a crossover system notorious for cracking. Larry was a word of mouth recommendation from a friend. My how times have changed!
When I received my RV4-pipe from Larry in 94' it was a marvel to behold with it's precision welds and slip joints. Roll the clock forward 15 years and it is still bolted to my RV4 flying in VA with a new F-18 pilot owner, 1400 hours later. I had absolutely no issues and I believe it is very efficient compared to 2 pipe systems if you believe in exhaust scavenging. Steve Wittman believed exhaust scavenging could add as much as 15% more power. Automotive headers follow the same principle. I believe the 4 pipe is better.
Recently I purchased a new system (2 very big pipes) from Larry for my Harmon Rocket. It too is a Marvel to behold and of the highest quality, fitting perfectly. I again broke his cardinal rule and had it ceramic coated. I immediately noted an increase in power at high settings and more full throttle rpm.

Questions?

Smokey
HR2

PS: Ryan, trim 2" off the bottom lip of your cowl and the 4-pipe should fit fine. Go with it, you won't regret it.

I have the 4 pipe system and like it, have about 40 hours on it.

It is the only way to go with a horizontal sump, leaves plenty of room to bring the throttle and mixture cables forward.

Performance is on the plus side. I can get the thing to go faster than Van's numbers on a good day for a 180 hp RV-7A.

Cabin heater works great off #4 pipe, better than the Subby hot water heater.

There's something primal and fundamental about 4 stacks off a 4 banger, I like 'em.

ryan said:

... and I'm worried that this will create more problems than it's worth....

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Ryan, not sure about the question. I have the -4 pipe. No regrets. I have pictures of the outlets. If you want them give me an email address. Not a lot of work to install.

Vetterman's Four Pipe

Merle and Ryan,,,after twenty years with Alan Tolle's crossover exhaust on my Four and much repair to the cracks that developed, I went with Vetterman's 4 pipe...upon inspection as Smokey stated, a marvel to behold indeed...there were no issues with installation, and this is under the ol' fixed pitch cowl...as to cabin heat, I just had to shorten the heatmuff to get her to fit...said heatmuff wraps around both pipes on the right side and provides more heat than before...and as to performance, there was a noticeable increase in low-end power as the engine developed the rpms more quickly upon roll-out...and the sound, the sound always draws positive reviews from those on the ground when given demonstrations of the Four's performance...
Chris
kit#26
21+ years of grinnin
Jackson, CA

smokyray said:

trim 2" off the bottom lip of your cowl and the 4-pipe should fit fine.

Click to expand...

That's what I'm hoping to do. There are already two faired outlets there for the old pipes but they will mostly disappear with a 2" cut.

Steve Sampson said:

Ryan, not sure about the question. I have the -4 pipe.

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I was just wondering whether anyone had made the switch from the crossover to a 4 pipe and whether they ran into problems x, y, z, etc trying to get it to fit correctly under the cowl. It sounds like Steve had no issues with the same project which is inspiring.

Buzz said:

...as to cabin heat, I just had to shorten the heatmuff to get her to fit...said heatmuff wraps around both pipes on the right side and provides more heat than before...

Click to expand...

I'm glad to hear that the heat muff fit over the two pipes, that will save a few bucks. It will be a good rainy day (if it ever rains again) project in the distant future, as I doubt I'll find an immediate need for cabin heat here in South Texas.

I appreciate all the input. I'm looking forward to installing the shiny new system. It appears that the flange nuts will be more accessible on the new pipes and I can't wait to hear what it sounds like behind the Q-tip prop.