Exhaust system

I’ve got an exhaust for you, Cory. I’m still in the Czech Republic at the moment. Flying back tomorrow...

I’ve got a Vintage Speed exhaust sitting in my garage. The link you sent isn’t the “Speedster” replica version (they are different) - at least I think so...

I don’t have pics to post on my iphone, but if you go through my first Speedster build thread you can see it and hear it.

I’ll post more when I get back

Cory,

1-1/2” tubes on a 2,110 should work just fine unless you want to rev to 6 grand when you shift - Somehow, I don’t think that’s you.

I have a 2,110 that I’ve carefully matched the flow rates through the engine with 40mm carbs, match-ported intake manifolds and heads, and Engle 120 cam and a Berg 1-1/2” exhaust header.  I went with the 1-1/2” exhaust tubes to push the power band a bit lower for more mid-range torque, rather than max power on the top end, so it starts to run out of poop around 5,800 RPM, but has gobs of power from 2k up to 5,500 and that’s were I drive it.

Remember, VW boxers like a certain amount of exhaust back pressure to make mid-range power, so that Aircooled system should be fine - and quieter than my Berg system!    (always good around all those Geriatrics out in Phoenix)! 

Gordon is right- unless the engine is designed to go to more than 6,000 rpm with power (which starts to make it a little high strung the further up the rpm scale you go) 1 1/2" primary tubes are a good fit for a 2110. 1 5/8 will give a little more power to the last 1,000 rpm or so but there is always a trade- more top end- less bottom end. Now, a 2110 is a pretty stout engine and has great inherent torque (because if it's size, long stroke and shorter rod ratio with VW length rods), but (as Gordon said) for "gobs of power from 2k up to 5,500" and that’s where we drive these things 99% of the time.

I'm not an expert by any means. If experience is the best teacher, and experience is gained by making mistakes, I'd be on my way to a doctorate.

However, this just isn't the case.

I sometimes delude myself by thinking I'm on my way to being as smart as the guys who've done their actual doctorate work on this stuff because I bump my way around the garage. They've worked out the physics of this stuff, and any conclusions I eventually arrive at through tons of mistakes generally end up lining up with the actual math. I've found (way too late) that it's probably more productive to read what they have to say before I spend a bunch of money and time on (yet another) failed experiment.

Al's chart is pretty accurate, but it presupposes an extractor-type exhaust. Before your eyes glaze over, hear me out. An equal-length 4 into 1 header (like Gordon's merge) is almost magical. It works by actually drawing a vacuum on the exhaust port of each cylinder, because the other three cylinders are creating a venturi at the collector (the "1" part of 4 into 1). The length and diameter of the tubes coming from each individual cylinder and the size of the collector "tune" the exhaust to create a more powerful vacuum in certain RPM ranges.

The vacuum on the exhaust port really helps with getting the spent gases out of the cylinder, and actually helps suck the intake gases into the cylinder. The effect of the vacuum on the exhaust port is actually many times stronger than the vacuum of the piston falling in the cylinder. That's the magical part.

A 2110 with a 1-1/2" equal-length 4 into 1 header is a really sweet little engine. A 2110 with a 1-5/8" equal-length 4 into 1 header is sweet as well, but it moves the "sweet-spot" up in the RPM register. It'll be soggier down low, but scream harder on the top. On the street, I like the feel of the 1-1/2” equal-length 4 into 1 header better.

The thing is- the Vintage Speed exhaust you're looking at (as well as the Tri-Mill, the Monza, and others of this ilk) are not extractor-type headers, so they don't work the same way. There is still something of the vacuum effect, but it is not really tuned in any meaningful way. As an aside- the A1 sidewinder we all swoon over IS a 4-1 design, but the tubes are nowhere near equal-length, so the effect is nowhere near as good as it is with a merge exhaust. Look at any dyno-day monster pull, and it'll be through a true equal-length 4-1 merge header.

Also, it's a misconception that ANY engine "likes back-pressure". What they like is extraction, and an engine with an exhaust will always run better than one without-- not because there is back-pressure, but because the tubes of the exhaust keep a steam of hot gases moving in the right direction and create a vacuum on the exhaust port. This is extraction, and all exhausts do this to one degree or another, but some much more effectively. Back-pressure without any extraction would effectively stuff the exhaust gases back into the cylinder and kill it.

The way the Vintage Speed set-up extracts exhaust gasses (reasonably) well is by means of that big-'ol muffler looking thing (the can, if you will). On the Vintage Speed set-up, that can is actually an expansion chamber, which creates a vacuum by means of being a (comparative) low-pressure zone. It works because there isn't much in there, and it's big. A Tri-Mil doesn't work as well because the can is much smaller. A Monza is probably the worst of all.

What does all this mean? It means that Gordon's equal-length 1-1/2" merge 4 into1 header is probably perfect for the average street 2110. If that exhaust was an A1 sidewinder unequal-length 4 into 1, I'd still probably pick a 1-1/2" header. But if I wanted an expansion-chamber exhaust like the Vintage Speed, I'd probably step up to a 1-5/8" set-up.

Nothing is perfect. The Sidewinder came about because the 4 into 1 merge header points the collector straight back, and ends up with a goofy-looking U-tube to get the exhaust back under the car. By rolling the collector sideways, the entire thing could tuck up and (mostly) out of sight. The Vintage Speed exhaust gives up the powerful extraction of a 4 into 1 header for a much more compact and pretty package.

What compromises you want to make should determine what exhaust to run.

FINALLY!  Stan and I said (almost) the same thing but THIS time, HE used more words!!!

Sorry, Stan - had to do that.  And you’re right, the Berg extractor has a goofy-looking basket of snakes under the rear valence that always looked a little weird to me and other drivers - until Pearl leaves them in the dust.....Except for that damn Fiat 500 Turbo Scorpion that night.  I asked a local hot rod builder and really decent exhaust guy about what it would take to move the collector up a bit and angle it so the mufflers were higher and all that.  He looked at it for about 20 seconds and said, “Forget it, kid.  I would probably set the body on fire and I don’t have a VW engine to use as a jig”

And the whole concept of an exhaust expansion chamber has been around since before the 60’s when my friends and I were running them on our 2-stroke motorcycles.  And I think that John Penton was one of those PHD’s who preferred to apply his knowledge to motorcycles to make them racing machines to behold.  One of his local disciples, a guy named Randy, I once asked about swapping out my basket of snakes for a quieter, “can-like” muffler on Pearl and he told me, “Don’t be a f-ing Putz.  Do that and you’ll wish you hadn’t.”   Pretty much good enough for me.....   What I don’t know about I trust others to know.

 I had a stock VW exhaust (muffler) on my first dune buggy.  Drove way out to the forearm of Cape Cod (hold your arm up to the side in a mirror - you’ll see where I mean) to run the dunes out there.  Got hung up on something and literally tore the muffler off.  Decided to drive home, thinking no one would notice the noise other than me.  Big mistake.  Not only did every car around me give me the finger all the way home, but the engine was totally gutless, like maybe half of the original, robust 36 HP, and it was SO LOUD I couldn’t hear much of anything for a couple of days after getting home, taking over 4 hours for the usual 3-hour trip. 

Upkeep of the extractor is easy, too.  All I do is shoot my pipes and mufflers with hi-temp BBQ paint every spring and rave on.

Stan is right, of course. I hadn't considered the fact that the can type muffler would act differently, so ignore what I said and carry on!

Gordon Nichols posted:

FINALLY!  Stan and I said (almost) the same thing but THIS time, HE used more words!!!

Gordon Nichols posted:

Remember, VW boxers like a certain amount of exhaust back pressure to make mid-range power, so that Aircooled system should be fine - and quieter than my Berg system!    (always good around all those Geriatrics out in Phoenix)! 

 You know how I respect you, Gordon, and this will probably seem pedantic.

But... the reason I rambled on to such an extent is that there is one thing we don't agree on, and it's the statement that, "VW boxers like a certain amount of exhaust back pressure".

I know that what you are saying is that sometimes (like in the case of the VW canister muffler) an engine with a restrictive exhaust will perform better than one without any exhaust at all, but this is not because of "back pressure". This is because of the flow characteristics of the exhaust down the pipes. Generally, even a poorly designed exhaust system will provide enough scavenging effect on the exhaust port to make it seem like the restriction is the thing working the magic, but it's not.

If the exhaust has been well designed, with the proper primary tube diameter and length, and with the proper sized collector, a more restrictive exhaust will not improve performance. Ever.

However, there is no "perfect" exhaust design with a flat-4 in the back end of a stubby car. Your merge with about an 18" stinger comes the closest. A CSP Python (which is laid out like an A1 Sidewinder, but which has true equal-length tubes and variable sized collector cones) would probably be the next best, but the primaries are longer than ideal. The A1 sidewinder with unequal-length primaries and the nicest collector on the market would probably be third. The Vintage Speed "Sebring" would probably be fourth because there is no real collector (in the technical sense of the term), and the primaries are longer than they should be.

The Vintage Speed "pea-shooter" is in a completely different class, and isn't really "tuned" like any of the others. But it works, and it's still a very nice exhaust for a <130 hp street engine.

But, regardless, it isn't the "back pressure" that builds mid-range. If this were the case, we'd all just put flow restrictions in our exhausts and run around with super-performance.

I think I know what you mean, but others may not. Back pressure is not your friend.

Stan Galat posted:

I'm not an expert by any means. If experience is the best teacher, and experience is gained by making mistakes, I'd be on my way to a doctorate.

However, this just isn't the case.

I sometimes delude myself by thinking I'm on my way to being as smart as the guys who've done their actual doctorate work on this stuff because I bump my way around the garage. They've worked out the physics of this stuff, and any conclusions I eventually arrive at through tons of mistakes generally end up lining up with the actual math. I've found (way too late) that it's probably more productive to read what they have to say before I spend a bunch of money and time on (yet another) failed experiment.

Al's chart is pretty accurate, but it presupposes an extractor-type exhaust. Before your eyes glaze over, hear me out. An equal-length 4 into 1 header (like Gordon's merge) is almost magical. It works by actually drawing a vacuum on the exhaust port of each cylinder, because the other three cylinders are creating a venturi at the collector (the "1" part of 4 into 1). The length and diameter of the tubes coming from each individual cylinder and the size of the collector "tune" the exhaust to create a more powerful vacuum in certain RPM ranges.

The vacuum on the exhaust port really helps with getting the spent gases out of the cylinder, and actually helps suck the intake gases into the cylinder. The effect of the vacuum on the exhaust port is actually many times stronger than the vacuum of the piston falling in the cylinder. That's the magical part.

A 2110 with a 1-1/2" equal-length 4 into 1 header is a really sweet little engine. A 2110 with a 1-5/8" equal-length 4 into 1 header is sweet as well, but it moves the "sweet-spot" up in the RPM register. It'll be soggier down low, but scream harder on the top. On the street, I like the feel of the 1-1/2” equal-length 4 into 1 header better.

The thing is- the Vintage Speed exhaust you're looking at (as well as the Tri-Mill, the Monza, and others of this ilk) are not extractor-type headers, so they don't work the same way. There is still something of the vacuum effect, but it is not really tuned in any meaningful way. As an aside- the A1 sidewinder we all swoon over IS a 4-1 design, but the tubes are nowhere near equal-length, so the effect is nowhere near as good as it is with a merge exhaust. Look at any dyno-day monster pull, and it'll be through a true equal-length 4-1 merge header.

Also, it's a misconception that ANY engine "likes back-pressure". What they like is extraction, and an engine with an exhaust will always run better than one without-- not because there is back-pressure, but because the tubes of the exhaust keep a steam of hot gases moving in the right direction and create a vacuum on the exhaust port. This is extraction, and all exhausts do this to one degree or another, but some much more effectively. Back-pressure without any extraction would effectively stuff the exhaust gases back into the cylinder and kill it.

The way the Vintage Speed set-up extracts exhaust gasses (reasonably) well is by means of that big-'ol muffler looking thing (the can, if you will). On the Vintage Speed set-up, that can is actually an expansion chamber, which creates a vacuum by means of being a (comparative) low-pressure zone. It works because there isn't much in there, and it's big. A Tri-Mil doesn't work as well because the can is much smaller. A Monza is probably the worst of all.

What does all this mean? It means that Gordon's equal-length 1-1/2" merge 4 into1 header is probably perfect for the average street 2110. If that exhaust was an A1 sidewinder unequal-length 4 into 1, I'd still probably pick a 1-1/2" header. But if I wanted an expansion-chamber exhaust like the Vintage Speed, I'd probably step up to a 1-5/8" set-up.

Nothing is perfect. The Sidewinder came about because the 4 into 1 merge header points the collector straight back, and ends up with a goofy-looking U-tube to get the exhaust back under the car. By rolling the collector sideways, the entire thing could tuck up and (mostly) out of sight. The Vintage Speed exhaust gives up the powerful extraction of a 4 into 1 header for a much more compact and pretty package.

What compromises you want to make should determine what exhaust to run.

Stan, thank you for the information, I have a sidewinder on a 2332 motor. have thought about removing the can and making a merge straight pipe exit on the car.  good? bad ? otherwise or suggestions including replacement? Custom 4 in to one pipe exhaust?

thanks!

@Ndpendant wrote- "I have a sidewinder on a 2332 motor. have thought about removing the can and making a merge straight pipe exit on the car.  good? bad ? otherwise or suggestions including replacement? Custom 4 in to one pipe exhaust?"

Are you talking about no muffler at all? It will certainly be loud- have you ever heard an unmuffled VW engine? I can't imagine that's street legal.

It's not 100% true all the time, but generally speaking: assuming the exhaust system isn’t stupid-restrictive (yours is not) anything that happens after the header collector doesn't matter. If you want to run a straight-pipe, it won't hurt your performance, but it likely will not help it either.

I've got an exhaust cut-out which bypasses the muffler(s). It's loud (ask anybody who was on the Smoky get-together last year) and I love it. It makes zero difference in performance. Its only advantage is that it is obnoxious.

Thanks for all of your replies, guys!

I learn something every time I open one...  I'm thin on knowledge, but you're all helping me, little by little.

I admit that I just want a nearly-bulletproof car that will get me to places where I can shoot cool photos... LOL

Funny, we're having the same discussion on Rennlist right now...

Corey, good luck with your build, again!

Rennlist.......   Meh.

I’m still waiting for a photo of Cory doing a pose like “Vanilla Ice”

Ice........Ice".......Baby!”

close ---- U want a piece of me?

No, not THAT Cory.....    

The other Cory.  The one out in "The Land of the Kachinas" or Kokopelli or Century Temperatures or something.  

At least HE has enough hair to look similar to Vanilla Ice!

Oh, and I should also say that, having now read Stan's excellent description of what's going on in my exhaust system, that he was/is absolutely right, and I was looking at what was going on from 90º out.  His post makes so much sense.  I've copied it and included it in my Service Manual for Pearl's next owner to reference.  I think it's that good.

Don’t ever challenge me, Gordon.

Ever.

Vanilla Ice stole my look about two years after this photo was shot. His attorneys ignored me.

WHAT!?!?!?!

And do you do uninspired house renovations TOO???

Gordon Nichols posted:

WHAT!?!?!?!

And do you do uninspired house renovations TOO???

😆😂🤣

@Cory McCloskey

Twins:

The resemblance is uncanny.

Anybody ever notice that Cory McCloskey and Vanilla Ice are never in the news room at the same time? Coincidence? I think not! 

I'll just leave this right here

Just showing my age, here, but does anyone else think Vanilla Ice was the original model for “Max Headroom“?

Here’ Vanilla Ice:

Here’s Max:

Gordon Nichols posted:

Just showing my age, here, but does anyone else think Vanilla Ice was the original model for “Max Headroom“?

Au contraríe my dear Gordon but Max Headroom came before Vanilla Ice. Max Headroom came in 1984 and Mr van Winkle hit the market in 1985 even though his first album did not debut until 1989. VI copied either Max Headroom or our very own Cory McCloskey. 

Max Headroom was cool.

Vanilla Ice? Ummmmm....

Ummmm, ah....Cory:

Did we ever answer your exhaust question?  Sorry about the drift.

Stan’s “exhaust 201” posts are about the best I’ve seen here or on the Shop talk forums.  

Hope they helped ya, Mr. Ice.

Gordon,

Thanks, but most of what I know is from A. Graham Bell's "Four Stroke Performance Tuning", and from a series of PMs with the brightest guy on TheSamba (Glen Urban, aka: Modok). I'd love to know half of what that guy has forgotten.

The book is an amazing resource, and the chapter on exhaust systems is brilliant. Check it out.

Started reading "Four Stroke Performance Tuning". Great primer! My non-engineer mind can only take the information about a chapter at a time, but I'm learning.

Stan: re: thesamba, Modok, Gears(Paul), and Glenn Ring. All three usually right on time!

So... One more bit of pontification on extraction before I leave this for future searchers:

Did you ever wonder how valve overlap works? Simply stated, overlap is when both the intake and exhaust valves are open at the same time. This is a function of cam profile, and even the most tame camshafts have some overlap. As a cam gets more aggressive, the overlap increases.

I always wondered how this worked, until the principle of extraction was explained so that I could understand it. In short-- because the suction on the exhaust port is so strong, keeping the exhaust valve open at the same time as the intake actually helps fill the cylinder with a fresh air/fuel charge.

As I said above, the length and diameter of the primary tubes in a 4/1 extractor header "tune" the exhaust to create a more powerful vacuum within a certain RPM range. Likewise, the valve overlap (defined by the cam profile) ideally matches the "tune" of the exhaust. That's why some combos are so sweet (a W120 and 1-1/2" merge header come to mind), and some that you think would work well just fall on their face.

In addition, there's another fun fact: most header collectors bring the primaries into the collector in a pattern that matches the firing order. In other words, on a VW Type 1 with a firing order of 1,4,3,2, cylinder 1 is at 2:00 on the collector, cylinder 4 is at 5:00, cylinder 3 is at 8:00, and cylinder 2 is at 11:00. This creates a "swirl" through the collector as each cylinder fires in turn, which is thought to create a better vacuum on the exhaust port. 

Again: I could have looked at a header every day for a year and probably never noticed that. All of this proving that there is real science behind a lot of stuff we take for granted.

Stan detailed why the perfect tune is elusive and can't be held for long.  The variables are daunting and probably why a lot of us keep chasing it.