Vehicle & Technical > Discovery
poor engine
Evilgoat:
--- Quote from: muddyjames on January 19, 2008, 14:51:04 ---sorry to kind of hijack the thread but it seems the main purpose of the thread is over so.........
Why do engines have timing belts / chains? Why cant engine manufactures design something that is maybe cog realted or by a physical link that wont snap and destroy an engine?
Can you spot the guy who knows nothing about engines ;)
--- End quote ---
All three are done.
Chains are used and are normally more reliable, but they are noisier and more expensive.
There are a few cars that used gears for overhead cams, these were expensive over complicated and again noisy, have a book that goes into this in detail written when dlets started to apear in engines.
Gears for in-block camshafts are used and are common place on small deisels and petrol engines like the little suffolks and petters. Again, it hink its down to noise and maintainance. A belt is easier to change then a chain or gears.
The idea is to keep weight in the valvetrain to an absolute minimum, this means more accurate valve timing and better response to engine speeds, this is why there are to my knowledge no modern pushrod engines. If you think od a 200tdi, the mass of the valve train includes the pushrod, tappets, rockers and the whole valve assembly. In a more modern engine, say the Suzuki theres no pushrods (them things arent light). And more modern still, the Audi uses two camshafts and act directly on the valves, no rockers.
Evilgoat:
Just Remebered, the 2,8TDI Mitsi engine in the Paj uses gears, I remeber this because timing it up was a royal pain.
Range Rover Blues:
As do the Essex Ford V6s. Originally they used a fibre gear to keep noise down, but these are infamous for stipping teeth so modern rebuilders use an aluminium gear. Af evilgoat says though, lots of weight in the valvetrain, which makes the engine harder to rev up.
Chains are more reliable up to a point, but they stretch, rattle and occasionaly snap. Ford I4 anybody :'(
Belts are generally quieter, lighter and if serviced properly one of the best options (though the Ford Zeta has now gone to chain, called the Duratec). Ford Sigma engines have a 100,000 mile belt on them.
Disco Matt:
Has anyone tried the Zeus gear kit for the TDI? Just thinking I read about them some time ago but haven't heard of many people using them. Mind you, the price might have something to do with that - they were asking about £800 IIRC!
Buzz:
--- Quote from: Disco Matt on January 23, 2008, 15:48:22 ---Has anyone tried the Zeus gear kit for the TDI? Just thinking I read about them some time ago but haven't heard of many people using them. Mind you, the price might have something to do with that - they were asking about £800 IIRC!
--- End quote ---
I have the zeus gears fitted to the 200 tdi in my 90, they've been fitted for two and a half years.
At first there was hardly any noise difference between them and the belt, but after two years, and less than 10,000 miles they'd became quite noisy. So noisy in fact that when I left the 90 with the local LR garage, the first time the mechanic started it up, he switched it off straight away and had a look under the bonnet to see what all the racket was!
When people hear it they think its got a clapped out old diesel under the bonnet, so it has the advantage of sounding like a shed as well as looking like one, therefore not attracting too attention of the wrong sort. Although it does suprise people when it does them away from the lights! The rest of the time, when the engines idling, the gear noise gets a bit annoying.
The main reason for fitting them was due to a four thousand mile cambelt, less than a year old, failing just after cresting a big climb on a welsh byway! The belt failed due to drawing some muddy water into the timing casing via the crankshaft / timing case seal, which caused the tensioner bearing to fail two months later. The 90 had been stuck with the engine partially underwater for 20 mins, very cold water.
Wanting to try and avoid history repeating its self, i decided to give the gears a go hoping that they would be a fit and forget solution. Well they're doing their job, but i certainly can't forget their there everytime i let the engine idle!
Would I make the same decision a second time? No. Taking the cost of the zeus gears into account, I'd make sure the front seal is in good condition, make sure the timing case is well sealed, fit a breather to the timing case, and replace the cambelt regularly.
Buzz.
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