Building A Carbed Liquid Cooled Engine For Longevity

[nicholastanguma]

For reasons of simplicity and DIY user-friendliness I vastly prefer carbed, air cooled engines to their EFI, liquid cooled counterparts. I'll personally allow for a CDI with the carbed air cooled mill, but that's the extent of my tolerance for electronics.

The problem with carburetors and liquid cooling of course, is that carbs pour a little raw fuel down the cylinder walls upon each cold start, which allows for a tiny bit of wall wear that isn't present with an EFI system; as far as I know, this is the single biggest cause of cylinder wear being faster in carbed engines vs EFI engines.

EFI and liquid cooled lasts much longer than carbed and air cooled, however air cooled engines are, essentially, endlessly rebuildable. Just order new cylinders and bolt them in place of the old worn out ones--I think this is how carbed, air cooled engines stay not just viable but so massively popular in this modern age of electronically controlled engines...whereas a liquid engine block will probably be useless after a single over-bore rebuild.

So in these days of EFI, liquid cooled mills easily making 300K miles in automobiles and 80K-100K in motorcycles, does a carbureted liquid cooled engine engine even make sense?

Give the cylinder walls a silicon carbide plating, and give the piston skirts a molybdenum disulfide coating, and this will surely increase the life expectancy of a carbed engine, but still, wouldn't we be looking at a liquid cooled mill that has a much shorter life expectancy than that same mill with EFI?

Basically, is it even possible to build a carbureted liquid cooled engine for high mileage?

 

[spot]

What do you consider high mileage? I’ve built carbed engines that went well past 300000. I made sure they were serviced regularly and not abused.


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[Sleeping Dog]

How a vehicle is used and maintained is a greater factor in engine longevity than carbs v. EFI or liquid cooled v. air cooled.

 

[roving1]

This is over thinking on an epic scale. Yes modern CAN vehicles are a bit ridiculous but applying that logic to all EFI is silly. There are simple OEM and standalone systems that are reliable and easy to diagnose and fix If you have some sort of zombie apocalypse complex you can pack spares that swap out in seconds or no harder than fixing carbs. Or go the aviation route and just have 2 redundant systems wired in.

Part of my reliability metric is being able to drive and cold start my vehicle without having to rejet my carb or tweak my choke every time I drive up a mountain.

But arguing longevity when you are intentionally picking the highest maintenance most effort intensive path seems pointless to me.

 

[luthj]

A well set up efi system is vastly less stressful in a myriad of operating conditions than any carbed system. The electronic components can be very reliable, and for many reasons will require much less maintenance than a carbed system. They are less prone to human error during setup, and require no user input once configured.

EFI systems also have better fuel economy, and less oil contamination. There is no comparison in mixture control between a EFI system with O2 feedback and a carb.

Yes the latest generation of CANbus driven vehicles can be more complicated. Not because canbus itself is a bad protocol/application, but because consumers are demanding more automation and performance. A reliability oriented CANbus system is quite reliable, though not necessary for EFI.

Once you move into the higher performance per liter displacement, you basically must have EFI unless you are paying constant attention. Anything over 70hp per liter is putting a lot of stress on an engines fuel system. Any drift, knock, imbalance, etc due to altitude, fuel differences, ambient temps etc, can cause an engine meltdown pretty quick. EFI systems can take this in stride.

The reason many air cooled engines need to be "endlessly rebuild-able" is because the high cylinder and head temps cause accelerated wear. To be fair most well designed engines can rebuilt "endlessly". Assuming the crankcase/block is not holed. Cummins, CAT, etc all make allowances for many rebuilds with oversized parts, sleeves etc.

There are some great plug and play style EFI systems out there. They are simple to configure, and reliable. Most contain a MAF (or MAP sensor), O2 sensor, crank sensor, cam/dist sensor etc. With solid state ignition you also really improve reliability.