Engine question

[dhasdell]

Here's something that just occurred to me: why do radials have an odd number of cylinders, while inlines have an even number?

 

[bazzar]

Firing order. Every other piston has to fire in sequence to provide an even smooth run. It's more balanced because it doesn't need two cylinders to be at TDC or BDC at the same time. Interestingly, of course, a 9 cylinder becomes an even number when two rows are used - 18. Remember the old Audi 5 cylinder? that used to run smoother than 4s and 6s.

 

[dhasdell]

Thank you. Some modern small cars have three cylinders, I think.

 

[huub vink]

Thank you. Some modern small cars have three cylinders, I think.

Yes, my wife's Volkswagen has one, like most small cars currently have. But like Bazz already said, line engines with an odd number of cilinders are not really uncommon. Audi, Volkswagen, Volvo, Fiat and General Motors all have or had 5 icilinder engines. For motorcycles a 3 cilinder line engine was not uncommon as well. I can remember the fast 2 stroke Kawasakis and the Suzuki watercooled 2-stroke GT750 and the Lavervea 1000cc four stroke engines. The Honda 125cc RC149 racer from 1966 even had a tiny 5 cilinder engine!

Nevertheless I think it was an interesting question as it got me thinking for a while .

Cheers,
Huub

 

[bazzar]

My car occasionally has three cyinders. Sometimes four other days maybe five...

Before the war it was quite common for speed records to be attempted using the same engine but with plugs removed. MG used to do it quite regularly going from six through four to three cylinder records with the same car.

 

[lliaghll]

Speed Records

Not just before the war. I've seen recent videos about Bonneville where they disable cylinders in a V-8 to go after other records.

 

[Bjoern]

Thank you. Some modern small cars have three cylinders, I think.

A lot of modern cars actually do.

Imagine my shock that, after ten years of usage, I found out that my mother's car actually only has three cylinders instead of four. And I always wondered why the engine ran a bit rough for a four cylinder engine...

Then I go my own car (same model, larger engine with actual four cylinders) and on a cold day, I am unsure if it isn't a diesel because it does run a tad rough.

 

[Blackbird686]

I had an old 1965 (or there abouts) Saab 2 door, little front wheel drive egg of a car and it had a 3 cylinder, 2 stroke engine. Had to mix the oil in the gas. Didn't have much top end but man, was it quick! It had a 4 speed shifter on the steering column and it could be set up to freewheel when you took your foot off the gas, or have the clutch hold the transmission like a regular manual set up. Still had to use the clutch when shifting tho... something about the gearing.

BB686