timing chains or belts in purported supercars

[tshih]

Recently I've seen postings on this board about lusting after those Italian exoticas like Ferraris 360 Modena and others. Just wondering who knows the truth about these high priced and acknowledged weaker designs (than a 911).

I see that the new Cayenne has chain driven timing gears as do the new 996 and 986. Must have learned their lessons on timing belts and other poor reliability systems found in their earlier 924-944-928 engines.

Anyone knows what the various supercars timing gears are driven by chains or belts? Example Lotus Esprit, Lamborghini Countach, Diablo, Murcielago, Ferrari 355, 360, Enzo, Viper, Corvette, Saleen S7?

Tom

[CarreraS2]

I don't know about all of those cars you mention, but it seems to me that "high end" high performance engines can use either a chain or a belt.

A 911 uses a chain. A Ferrari Testarossa, 308/328,348, 355 etc. uses belts.

Various BMW engines use chains, and other BMW engines use belts.

I also don't think that one is necessarily more reliable than the other (although a chain is generally lower maintenance, most chains being a "life of the car" part, while belts have changing intervals). The MB V-8 single chain system from the early 80's was not very reliable, while the BMW belt system from that same time was very reliable (as most belt systems are).

I prefer a chain because replacing belts is generally a pain. But, I could live with either one. I wouldn't hesitate to buy a car that I liked (like a Ferrari) simply because it has a belt system.

[tmctguer]

one thing i've always heard about ferarri's (including from their owners) is that the rubber belts must be changed at periodic intervals to ensure they do not fail and cause catastrophic engine damage.

for a car like a testarossa, the engine must be dropped in order to change the belts. this service alone could cost $2K - $4K, which is why testarossa's are not that expensive ($60K - $90K).

[tshih]

I've always been impatient with poorly designed cars...which is why I love the 911 above all else. The Ferraris with the need for 15K miles belt check and adjustments (labor costs for that is $5K) is absurd even though most owners rarely drive them that far before selling them used (ever wondered why so many used Ferrari's have close to 15K miles on the clock?). I think that chains with the proper tensioners are definitely what I'd want in any car I consider. The part about chains being only as reliable as their application is like saying aluminum engines are not as reliable as the old cast iron ones because someone misapplied them (as in GM Vegas) and they developed a bad rep. I 've lived with those damn timing belts (in my Honda Civic and sister's Accord) always threatening to break on me when I neglect to do their replacement (a royal pain in the ass for some cars) in the back of my mind.

IMHO exotics are like finicky mistresses- not worth the effort to be involved with when a good wife is available.

[Bill Verburg]

Audi has just gone back to chains from belts on its V8s

[HawgRyder]

I prefer gear drives myself...maybe a little more noise...but the confidence of solid gears is nice.
I was wondering if it has been tried with the flat six engine?
Might be worth a look when I get mine apart.
Bob

[cab83_750]

I have owned Japanese cars and I am most definite that they initially used chain, then to belts, and finally back to chain.

I was told by the head mechanic that the belt was a bad idea both in maintenance and reliability, thus the switch back to chain. Heck, if Japanese manufacturers did the switch, they must know something that some don't.


P.S.

He also said that chains almost always last as long as the engine, whereas belts MUST be replaced at factory-specified...else say goodbye to warranty.

[john_colasante]

Originally posted by HawgRyder
I prefer gear drives myself...maybe a little more noise...but the confidence of solid gears is nice.
I was wondering if it has been tried with the flat six engine?
Might be worth a look when I get mine apart.
Bob

I think this has been done in some Porsche racing engines. However it is not a little louder, it is excessively louder making it even impossible for normal street use - or so I've heard.

[A Quiet Boom]

One advantage of belts over chains in a true racing atmosphere is that they distribute less crankshaft harmonics to the valvetrain which is why they are sometimes retrofitted onto previously chain driven V8 engines. I'm with HawgRyder though on the geardrive, I used one on my drag car and while yes it's noisy it sure is reliable, mine used straight cut gears and was therefore very noisy, it is possible to use helical cut gears for less noise but you'll still have that "blower whine" sound to some degree. The idea of gears in a 911 is certainly worth investigating I would think.

[tshih]

Gears were used on the 911 airplane (Mooney) engine which were required by the FDA to have dual alternators ignition backup systems since you don't want engine failure in mid- flight That project was done in the late 1980's and was featured in Christoforus.

Unfortunately, the Porsche Mooney was not a commercial success so not many parts are available. But I agree that that represents the ultimate in reliability for cam timing. Down with those belts and noise concerns. True 911 aficionados love the mechanical noises of our cars anyway!!!

Tom