How does Toyota offer non-interference engines and seemingly no other manufacturer does? Contemporary Toyota 4-bangers don't even have a timing belt service interval for normal duty. I think it's 90K miles for severe duty, whatever that is for a timing belt. So you putter along, the engine quits, the car is towed to any shop, $300 later you're on your way with a new belt. Same thing you'd pay to have it replaced before it snaps. If the belt snaps on any other car you're out a cylinder head and possibly an engine.

It's only geometry - why hasn't this caught on throughout the industry? Does Toyota have a patent?

Sixto
87 300D

hmmm. I think they want to motor to be trashed so you can buy a new one or buy a replacement engine at mucho markup.

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

don't know. but i love the A series engine in my Tercel. I've never had the belt break. because i change it like every 3-5 years. but before i got the car my mom had one break on her. we towed it home and my dad changed it. very easy.

takes me about an hour to change the belt if i have to remove the radiator, 30 min if i don't have to remove it. the engine it the tercel is not transversely mounted, so it all depends on what puller i have for the harmonic balancer. my dad made one that i now have that is just the right size to take off the balancer without taking out the radiator.

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Volvo's are the same way.

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-1983 VW Rabbit LS Diesel (5speed, VNT/Giles build)

Not *all* of them. Some of the turbo motors aren't.

But my old VW Rabbit was non-interference, and my Miata is non-interference as well. Both of those have been tested.

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1972 280SE "Babe"
1968 250S 4spd

I had a Dodge Omni some years back. Surprisingly fast and fun to drive. I guess 2.2 liter is halfway big for a car that small.

Anyway, I busted a belt and came out smelling like a rose. Good thing too, cuz that car would have been instant junk with an interference engine.

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Te futueo et caballum tuum

1986 300SDL, 362K
1984 300D, 138K

Lately Toyota has been using chains. Don't know when they went that way but I do know the 07 and newer are all chains.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

That confirms the replacement engine theory

Sixto
87 300D

Well a chain shouldn't break or ever need replacing. So when the car gets old junk it, its just a cheap Toyota.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

My is300(toyota altezza) has an interferance engine. Timing belt was fairly easy to replace though, much much much easier than on my audi a4 2.8 thats for damn sure....

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83 300SD.......sold
96 integra SE....sold
99 a4 quattro....sold
2001 IS300.......sold
2002 330i.........current.
2004 highlander limited....current.

pretty sure the rabbits not.

I have a piston with some nice valves marks in it here...

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-1983 VW Rabbit LS Diesel (5speed, VNT/Giles build)

My VW air-cooled motor was even better! The horizontally-opposed configuration used two large gears for the cams and crank...no chain, no belts, no anything!

Just tweak the carb every other week, adjust valves every other month, and finally a weekend overhaul at 80K...including the replacement of that burnt third piston...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

To answer the OP - my impression is that any manuf. can build a non-interference engine...up until recently.
Obviously, if toyota did it, then its not an engineering impossibility, I figured that its more a design/cost thing than than anything else. The Toyota engineers were told to design an engine that is non-interference. The designers of the Altezza motors were not.

I get the impression that you give up a few things in a non-interference engine. First off would be a 4v/cyl valvetrain - to stuff all those valves in you must put them at an angle, and then open them as far as you can (to optimize breathing) and unless you give up a stack of compression ratio (ie- make the combustion chamber really big or the stroke really small) the valves will hit the piston when fully open at TDC. I'd be curious if any of these non-interference motors are 4v per cylinder.
I mentioned valve lift - no matter how many valves you have, or what your bore x stroke is, the farther you open your valves (to a point) the better the engine breathes, which means more power, better fuel economy, or some combination of both. Engine makers are always looking for these and probably have no problem opening a valve so far that an otherwise non-interference motor becomes an interference motor when you 'tune' it so far.

I say "up until recently" because the bar has been raised so high for engines as of late, that its probably tough to build an engine efficient enough for modern power/emissions standards that is not non-interference. Okay, Toyota can do it for bread-and-butter 4cyls, can they do it for 300hp truck V8's ? (I don't know)
From what I remember - back in 1990, the 2.0l 16v VW 4cyl made 130hp- it got 30mpg if you didnt beat it too hard. My wives 1997 neon had a 2.0l 4cyl, 16v, better emissions (OBDII), made 130hp and got 36mpg with an automatic transmission. This isnt a good apples to apples comparison, but I think we can agree that engines have come a long way in the last 5 or 10 years, and if someone tried to stuff that 16v 2.0l vw motor in a car today, it'd never sell. (not that I don't love old VW 16v's....)

As to the maintenance requirements - I don't think that manufacturers care as long as the engine will make it to 100k (the req'd US emissions warranty) with no trouble. After 100k, the manufacturer gains nothing from having a long lasting-chain vs. a belt that needs replacing.


-John

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2009 Kia Sedona
2009 Honda Odyssey EX-L
12006 Jetta Pumpe Duse
(insert Mercedes here)

Husband, Father, sometimes friend =)

I've heard that Toyota's 16-valve fours ARE interference engies. In any case, Toyota (like most other Aisian makes) have used 4 valves-per-cylinder on their fours since the late '80s. However, the Corolla (and Chevy Prisim) switched to timing-chains for '98, and the 4-cylinder Camry (as well as the 4-cylinder Honda Accord) switched for '02.

Happy Motoring, Mark

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DrDKW

Even though its been quite awhile I'm pretty sure my old 93 Camry was an interference engine. I think when I changed the T belt I spun the cam around to see.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200