MPG optimised header ideas

[Ecky]

I would include a waterjacket on your header to speed up warmup. Not too much area or you'll have to upgrade your radiator, but it'll probably help economy more than anything else you can do.

Also, as was mentioned before, take a look at Mazda's design. They were advertising that a carefully designed header was crucial in letting them use extremely high compression.

[undeRGRound]

Originally Posted by Ecky

I would include a waterjacket on your header to speed up warmup. Not too much area or you'll have to upgrade your radiator, but it'll probably help economy more than anything else you can do.

Also, as was mentioned before, take a look at Mazda's design. They were advertising that a carefully designed header was crucial in letting them use extremely high compression.

I'd say you would need a "thermos bottle" coolant heat retention system in addition to that water jacket. It would have the reverse effect (cooling headers) until the coolant warmed up. Header Wrap would work all the time.

[Madact]

Originally Posted by Ecky

I would include a waterjacket on your header to speed up warmup. Not too much area or you'll have to upgrade your radiator, but it'll probably help economy more than anything else you can do.

Well... I live in Australia, the temperature rarely hits less than 10 degrees C (50F) overnight (and almost never below 3-4C), and summer temps can get quite high, we've seen temps in the 45C (113F) range a few times in recent years. Plus I'm planning grille blocks, so improving exhaust insulation is likely to contribute to everything else under the hood being happier

Plus, I feel that keeping the exhaust velocity high at low RPMs (through good insulation) probably trumps savings on the warmup cycle for a 30m drive, particularly with a modern engine - as I understand it, with newer engines the cylinders and valve train come up to temp in 30s to a minute, and modern oils (especially the thin stuff that Hondas apparently like) don't stay sticky very long. This is just gut feeling though - I should look at what improvements people with electric block heaters get. Of course even then, gains from an electric block heater would be larger than a water-jacket setup so it wouldn't be exactly equivalent.

[undeRGRound]

Oh, I see. We are speaking of Engine Warmup, not header warmup

[undeRGRound]

I would think that undersized cast iron "log" manifolds would benefit the most from cooler exhaust. Plenty of velocity already. The water jacketed manifolds would have their greatest benefit on a totally thermally managed ICE. There was a university that did an experimental "throttle-less engine" which basically used warmer air for lower RPMs, with less fuel to maintain the targeted AF ratios. Cooler Air Temps = Higher RPM and more fuel. Needless to say, FE (is that how they say Fuel Economy 'round here?) went up as well, due to greater thermal efficiency from the preheated air!

[Madact]

Originally Posted by Old Tele man

FYI, exhaust gases, like motor oil, gets "thicker" the colder it is, so *keeping* the temperature as stably-hot will minimize velocity "slow-down" as it traverses through the header pipes. Won't be MUCH, but it will help you maintain the MASS-velocity-flow.

Originally Posted by undeRGRound

I would think that undersized cast iron "log" manifolds would benefit the most from cooler exhaust. Plenty of velocity already. The water jacketed manifolds would have their greatest benefit on a totally thermally managed ICE. There was a university that did an experimental "throttle-less engine" which basically used warmer air for lower RPMs, with less fuel to maintain the targeted AF ratios. Cooler Air Temps = Higher RPM and more fuel. Needless to say, FE (is that how they say Fuel Economy 'round here?) went up as well, due to greater thermal efficiency from the preheated air!

Everything I've read agrees "cold exhaust gas" = bad, especially at low RPMs. A few examples I've found of people implementing WAI (vs. stock intake) on Honda D-series engines also reported neutral or negative impact on FE, so I think it depends a lot on what the ECU is doing too.

If I did want hot air, I'd probably take it from a small jacket on or just after the cat. Plenty of waste heat to be had there.

Interesting about the 'throttle-less' engine - you could probably get a similar effect by running EGR at WOT... could be a good way to set up an efficient cruise control, for example, just open the throttle and use a big fat EGR valve to control power

[Madact]

Originally Posted by undeRGRound

Don't think I had any input here, but splitting a 4-2-1 into two 2-1 headers and then running them into an X-Pipe would achieve the ASC design.

I saw the X-pipe thing - both as a better alternative to an H-pipe for bank balancing on V-shaped engines, and the whole "Acoustic SuperCharger" / "The Amazing Campbell X-Pipe" thing... while I think it may have some merit in certain situations, I think it might complicate the design a bit in this case. One thing I was considering was having a an X at about 55-60" and then merging back to a Y at 80"-ish but I'm not convinced it would be worth it.

I'll say straight up that I think a lot of the wilder ASC claims on x-pipe.com can be attributed at least in part to the fact that the Campbell pipes don't have mufflers (and by the photos I could find, cats either - though they say "legal"... but elsewhere on the page they say "pleasure license only" so whatevs). Now the X-Pipe itself is a decent scavenging system, but with those advantages (removing muffler and possibly cat), you give any basically well-designed and built system a chance to really shine

There are some really interesting aspects to X-Pipes though. Consider that in a Y merge, you effectively double the excitation frequency in the pipe after the merge compared with before the merge (as you're adding two sets of pulses 180 degrees out of phase). This will affect any resonance that happens after that point. However, if an X-pipe (mainly) flows across the 'X' between opposite pipes, then each downstream tube will be effectively experiencing the same excitation frequency as the input, which would mean a wider resonance bandwidth (& less sensitivity to downstream pipe length) while still getting the scavenging effect. This could be very useful for high-revving engines, I would expect it to be especially handy on a motorbike.

And of course the flow isn't restricted by changing direction or going down a pipe size, so positive pressure pulse reflection should be lower compared to a basic (i.e. cheaply fabricated) Y merge. And of course the output tone will be much more meaty, as you avoid the frequency doubling effect mentioned... if I was building a big burbly V8 hot-rod, it would be a candidate for sure...

So plenty of interesting aspects, but not necessarily huge gains for a 'street' car with cats, mufflers and low RPMs (unless you believe all the hype ) and quite a bit of added complexity.

If I had a good 1D simulation package I'd plug it in and see how it might go anyway, of course...

[user removed]

I'm amazed that no header manufacturer has not built or mass produced a tubing header for the VX. I'm not sure but think I read here that the CX uses the same manifold design. With the onset of cracking issues and the cost of factory replacements, close to $500, it would seem that there would be a market for a tubing header type aftermarket replacement.

The only rational reason for not producing one is that there just aren't that many of them (original CXs and VXs left to justify the start up costs, but even that makes little sense when all you need to do is get the intial setup for the computer to bend the components and weld them together.

Is there something I'm missing here?

regards
mech

[Madact]

Originally Posted by Old Mechanic

I'm amazed that no header manufacturer has not built or mass produced a tubing header for the VX. I'm not sure but think I read here that the CX uses the same manifold design. With the onset of cracking issues and the cost of factory replacements, close to $500, it would seem that there would be a market for a tubing header type aftermarket replacement.

Yikes... $500? Pretty sure I could put together a basic tubing header (exhaust ports to cat. flange) for the "cat in front of the motor" configuration in my shed for $400 and still turn a profit on the 'hand crafted' item... and that's including $150 for pre-made header flanges and sensor bungs. And in Australian dollars. Shipping could be an issue though, if most of the customers are in the US. As you say, the size of the market is probably the issue though - there's probably enough of them going through wreckers to soak up most of the market for them.

[serialk11r]

Originally Posted by Madact

Interesting about the 'throttle-less' engine - you could probably get a similar effect by running EGR at WOT... could be a good way to set up an efficient cruise control, for example, just open the throttle and use a big fat EGR valve to control power

The reason you can't do this is because once the exhaust gas fraction is over 20% (less on some engines) it'll start to stumble. Plus, warm air is not as great as people here think, it increases the heat ratio and decreases thermodynamic efficiency. Running WOT with exhaust gas (even cooled) will probably induce knock.