Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Crossover for M3W

I've always wondered why the M3W doesn't have a crossover like almost all V2 engines. So I had one custom-made. Visually, I think it turned out really well, and the results are phenomenal: better torque in the low and mid-range RPMs, smoother engine operation, a fuller, more refined sound, and lower fuel consumption. Some pics:

Looks pretty but please explain the theory to me if you can.

On a V-twin with separate exhaust systems, the two cylinders do not operate evenly. Each cylinder generates pressure waves that propagate through the exhaust. A crossover connects both exhaust headers, allowing these pressure waves to support each other.

The main advantages are:

More torque in the low and mid-range RPM band: Thanks to improved use of the pressure waves, the cylinders are scavenged more effectively. This often makes the engine more responsive and flexible.

Smoother engine operation: The pressure pulses balance each other out to some extent, resulting in a smoother-running engine.

Slightly more peak power: Usually only around 1–3%, provided the rest of the exhaust system is also tuned accordingly.

Reduced heat buildup: Depending on the design, the exhaust gas flow is distributed more efficiently.

Changed exhaust note: A matter of personal preference. Sound often becomes fuller and deeper, though sometimes slightly less "harsh."

Lower fuel consumption – an expected reduction of about 1 L/100 km.

Thank you so much for going to the trouble of explaining this, the benefits seem to make this necessary really.

Is the Siamese exhaust system on parallel twins a sort of halfway house answer to the problem.

Congrats and nice welding!

In essence the exhaust pulses of one cylinder aid scavenging of the other. Moto Guzzi V twins had a crossover on the front pipes or via an H section under engine or both.

Looks very nicely thought out for layout and well engineered joints, looks much neater than the KH version

What I however need is a new air filter cover. The standard one has its scoop only between 5 and 7pm on teh clock and breathes warm air just on the top from the balancing pipe. So better would be one which is wider open. Any suggestions?

Great idea and nicely executed!
What exhausts are you running? Just wondering if the crossover pipe would have more effect on a car with standard (i.e. restricted) exhausts than it would on a straight-through system.
Also, can the crossover pipe be removed without disturbing the headers?
What diameter is the crossover tubing?
Thanks,
Bunny

Hi Andy,

Both manifolds are stock. The pipes and tailpipes had been upgraded to Stage 3 by the previous owner and were completely open along their entire length (massively oversized). They were very loud, with a whip-like noise on the overrun—very unpleasant. With the crossover this negative effect is almost gone. Crossover makes sense for both stock and straight-through pipe system. This crossover can be easily removed for engine maintenance. Crossover diameter is 38 mm.

Cheers Klaus

Something like this one?:

It's on off the shelf custom unit from S&S for the X-Wedge. I've since had mine powder coated black.

Thank you Steve, this looks terrific! Where did you buy this?

It was on the car when I purchased it. At one time these were fairly easy to find in the U.S. but I just did a quick search and can't seem to find one. It might be worth checking with the larger Harley component suppliers or one of custom bike builders that previously used the X-Wedge like Big Dog Cycle or Combat Motors to see what they may have.

The three hole pattern on the throttle body is the same as some of the Harley Davidson models with the same throttle body diameter, and I see many similar air cleaners for H-D but the two mounting points on the cylinder heads for the air cleaner backing plate are wider on the X-Wedge engine. Summary: H-D filter elements and various top covers are readily available, it's the backplate that is unique to the X-Wedge. Note that the correct backplate is needed as said backplate is part of the mounting for the throttle body.

Apologies for getting you excited about something that may be unobtainable

An edit: After looking at my car, I was reminded that the air cleaner has two metal mounting ears or extenders, that fasten to what is highly likely to be a H-D spec filter assembly thereby adapting it to the X-Wedge motor. The air cleaner assembly is known as an S&S Steath air cleaner, and they separately sell decorative covers to suit your preferred style.

Here is a detail photo of the mounting ear:

Maybe this is interesting for you and available in de EU

A lot of choices and brackets to fit

Zodiac

A lot of choices of brackets and backplates but none of them listed for the X-Wedge as far as I can see. Probably not too difficult to adapt another engine bracket to fit though but a shame you can no longer get an "off the shelf" X-Wedge filter now.

Kudos on that X-exhaust—it’s perfectly integrated into the engine design; it’s a brilliant idea
It makes me want to buy an MTW to go along with my Plus Four for new three-wheeled adventures
As for the air filter, I had this one custom-made, based on the original filter :

Amazing how X-wedge accessories have just disappeared!
There is always the Garage 56 filter cover which presumably one could paint to taste?

This is the S&S Stealth air filter with the Muscle Cover. The Stealth Air filter can still be purchased at the S&S webpage, but the Muscle Cover, which is the chromed dish with the SS cables and lockpins is not available anymore. And for a few years now, which makes it really difficult to find a "forgotten" one on the shelves of any shop....

https://www.speedymarmots.com/hangar-works-9-change-of-air-intake-kit/

Great tip Marmota

A google search

https://fortnine.ca/en/s-s-cycle-stealth-air-filter-for-stealth-air-cleaner-kit-standard-170-0193

https://fortnine.ca/en/s-s-cycle-stealth-air-filter-for-stealth-air-cleaner-kit-1in-tall-170-0197



I do not know which fits

Those links are for the air filter element only, not for the entire air filter kit.

Why not sending a request to Fortnine.ca, with those pictures .
They show the cover and they seem to have a lot.
And questions are free.

Interesting to know their answer from Canada.
Also for us EU citizens, because the US is impossible to trade with for us for the coming two years.

Actually, by the looks of it, they are pre-filters - not even the main air filter elements.

Correct - also known as rain socks(?)

FYI - there is only one Stealth base plate that fits the m3w (with modified brackets) and only one type of cover that fits that is still available, which is either black or chrome domed type.

I have one left available.

Yes, that is a rain sock I have one on my filter not only stops rain but helps prevent dust and other bits getting into the filter.

The rain sock must be a commercial invention, because I have never encountered any problems during very heavy thunderstorms.
An old technique for removing heavy carbon deposits from intake valves involved running the engine until hot at 4,000 rpm and pouring in a large glass of water—doing so gradually to avoid stalling the engine—as the cold water droplets caused the thick carbon buildup to shatter.