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Lycoming YO-360-A1A vs YIO-360-M1B, differences?

Dan 57

Dan 57

Well Known Member
Mmmh, looking at Van's engine order page in the store, the 180HP variants are of the TB Lycoming are either the YO-360-A1A, or the YIO-360-M1B.
I realize one has a vertical, the other one a horizontal induction... any other difference justifying the $2887 price difference?variants.png
 
The M1B has a different sump style for the plenum chamber your intake pipes will draw air from. It will take the Fiberglass snorkel that Van's produces with the filter housing right in front of your #1 Cylinder. IT will have an alternate air valve up there on the side of the snorkel that you have to have a cable to operate. You can only use a certain starter as the Snorkel conforms around that location, thus limiting access. Any starter issues, you will be removing the snorkel to work on it. You have to get some brackets and a arm that mount under the cylinders (2&4 side) to route your cable through that controls the mixture. That cable will need to highly insulated so it doesn't get cooked by the engine heat. Lots of other items in there to scrap your knuckles on in installation :)
The sump on the M1B has a sniffle valve that lets out fuel that accumulates in the bottom after engine shutdown. This prevents an explosion in case of a backfire on startup, as you have a lot of air volume and some fuel there.
The M1B has an o-ring on the bottom of the intake tubes that seal up the tube going into the plenum. Kinda tricky getting that in there. So you will want to have some extra just in case you push it in to far and have to pull it out and pinch or bite some rubber off the seal.
Throttle locations are different.
Exhaust systems are different as you can't have the crossover exhaust running right over your M1B servo that is mounted horizontally.
You will have a sexy, sleeker looking cowling and lines on your airplane. Marginal difference, if any in performance. You look faster so it must be faster with the scoopless cowling :)
Baffling has some slight differences because of the filter location in front of the cylinders.
Fuel line routing is different to main fuel inlet, again, adding extra insulation due to the proximity to the exhaust system.
Cabin heat shroud is routed differently

I've done both installations and I would say the updraft is a little easier to install as you don't have all these tight accesses to your fuel servo and less over-insulating cables and lines to stave off heat.
However, if I had to do it again, I would still install a M1B. To me, the looks off the updraft scoop ruins the lines on RV's. That is just my opinion. I am sure others would disagree.

 
Aden gave a great explanation.

To add, the biggest difference (including price) is that the M1B is fuel injected. Fuel injected engines have their own quarks but I would not even consider a carbureted one for a new build; just my opinion.
 
Dan - I looked at the screen capture in your original post again. At the top it says “…. With no ignition or fuel system*“. Hmm, yes, I think I understand your question now - if neither the “O“ or “IO” version do not include the injection system, why the cost difference? Interesting.
I see Aden gave us the answer.
 
tthrew said:
Dan - I looked at the screen capture in your original post again. At the top it says “…. With no ignition or fuel system*“. Hmm, yes, I think I understand your question now - if neither the “O“ or “IO” version do not include the injection system, why the cost difference? Interesting.
I see Aden gave us the answer.
Click to expand...
Well observed Tim (y)
And thanks very much for that (fat) extensive answer Aden, learned a few things. Again ;)
I should have stated that it is not a new build, and that I have ordered a YO-360-A1A, vertical induction, as it gives me the possibility of installing either a carb, or to "upgrade" to a FI, or a EFI.

Thanks guys :cool:
 
An excellent resource for Info on "Y" build CONFIGURATIONS (ONLY) within Lycoming is Chris Gayman 570-327-7231, Please do NOT abuse this point-out for any other issues.
 
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