 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Car Forum / Driving, Maintenance, Tuning / General Car Topics / May 2005Two Technical Questions
I know they make non-interference engines should a timing belt fail. But, what is the reasoning for why anyone would design anything other than a non-interference engine. There must be some advantage??? What makes it desirable to have a timing belt vs. a timing chain? I would always think a chain would be the way to go, but some engines use belts...that have to be replaced. What advantage would make someone choose a belt??? >I know they make non-interference engines should a timing belt fail. But, >what is the reasoning for why anyone would design anything other than a >non-interference engine. There must be some advantage??? Easier to design and make. Slighty cheaper perhaps? In order for the valves to be non-interference they have to clear the piston no matter where the piston is--that is, if the valves stop full open, when the pistion comes up to TDC, there must be some place for the valve to go (dishes in the pistion face...) non-inteference also limits valve lift, so that larger valves are needed (cost...) and with the clearance for valves the compression ratio won't be as high. >What makes it desirable to have a timing belt vs. a timing chain? I would >always think a chain would be the way to go, but some engines use >belts...that have to be replaced. What advantage would make someone choose >a belt??? Cost. Noise. Reliability. A timing chain the length of the timing belt in a modern OHC engine would be horrible. Even slight wear would throw off valve timing. The chain would tend to slap around, and be really nosiy. A chain that long presents reliabity issues... Let me guess, you broke a timing belt on an interference engine and trashed it? <g> >>What makes it desirable to have a timing belt vs. a timing chain? I would >>always think a chain would be the way to go, but some engines use [quoted text clipped - 6 lines] > off valve timing. The chain would tend to slap around, and be really > nosiy. A chain that long presents reliabity issues... I question your reliability assertion. A chain will last the life of the engine as it is running in an oil bath. A belt will need replacing around 60,000 miles, maybe sooner, from the dirt and abrasion running dry and wearing it out. However, a chain will also take more horespower from the engine due to mechanical/friction drag as well as the oil induced drag on the chain. Many chains have chain tensioners as well as guides to keep slap minimized as well (again, more Hp robbing drag) -- if they are working right and have the correct tensioning (damhik!). > Let me guess, you broke a timing belt on an interference engine and > trashed it? <g> Again, belt reliability? But it does make the mechanics happy and it is cheaper in production costs. B~ >I question your reliability assertion. A chain will last the life of the >engine as it is running in an oil bath. A belt will need replacing around [quoted text clipped - 7 lines] >Again, belt reliability? But it does make the mechanics happy and it is >cheaper in production costs. Sure, under ideal conditions a chain is better. But the real world is far from ideal! <g> People don't do oil changes, chains wear out, and that is what counts. It is not uncommon to find chains with 60 to 90K miles that are sufficient worn that the timeing is compromised, and that is with the short chain found in a regular, non-OHC engine. With the longer chain in an OHC engine, that wear isi much more a factor. Additionally, chains do increase the costs a lot. The big complaint is noise, and chain slap. Benz learned that chains are expensive (but feasible...) alternatives to belts. Anyone who does good enough maintenance to keep a chain from wearing excessively would have no problems replacing a belt. Problem is that most people don't do proper oil changes, use crappy oil, and skimp on maintenance on the whole. That's life. Me, I'd love to have chains on my engines! Agreed they can be much better... >I know they make non-interference engines should a timing belt fail. But, >what is the reasoning for why anyone would design anything other than a >non-interference engine. There must be some advantage??? None that I can think of... >What makes it desirable to have a timing belt vs. a timing chain? I would >always think a chain would be the way to go, but some engines use >belts...that have to be replaced. What advantage would make someone choose >a belt??? Timing chains, in theory, are noisier. They are also heavier. With engine makers actually looking to save ounces, a belt makes sense. Engineers, you must remember, do not repair or replace parts. That's the job of Mechanics. If a Mechanic were to design an automobile, it would be the size of a locomotive and require only one size/type of screwdriver and one size/type of wrench to completely disassemble and reassemble.. Raymond Sirois KU2S SysOp: The Lost Chord BBS 607-733-5745 telnet://thelostchord.dns2go.com:6000 |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.