14 replies to this topic

[chipster196]

Just fitted a duplex chain and pulleys for an a series engine onto a 998 a+ do I have to run the tensioner as the chain seems nice and tight?

[sledgehammer]

http://www.theminifo...rea/?hl= duplex

 

IMO it's your car - run it & see how it sounds after a while - you can always add one later (with some mods)

 

Those in the know - say yes - you should run a tensioner

Edited by sledgehammer, 04 May 2014 - 04:17 PM.

[Vipernoir]

I'm running tensioners on mine.

 

You will need to hammer the dent in the timing cover next to the oil seal flat to get it to clear the duplex crank gear.

[KernowCooper]

AC fits a tensioner to his builds, I'm running one on mine.

[minilee94]

You can run one but you ain't Gota

I havnt got one on my 1380 but I will fit one soon

[KernowCooper]

Benefit is you get more accurate valve/ignition timing as well as the obvious quiter chain noise

[Dusky]

Do you need loctite on the bolts of the tensioner? Think I forgot that on mine... Engien sounds tappety, but that hasnt to do with the tensioner I think

[Cooperman]

There are mixed feelings on the tensioner with the duplex chain.

They do hold the chain in better constant tension and improve the cam timing accuracy as the chain wears.

However, in a high-revving engine, because the chain bears only on the centre of the tensioner pad at a single point instead of on two points as with the single chain, I have had one case of a tensioner pad breaking up and another, admittedly in a higher mileage unit, which was starting to fail.

The original Cooper 'S' did not have a tensioner with the Duplex.

So it's personal choice.

On my 'S' I don't run a tensioner, but I do use a lot of revs.

[chipster196]

thanks guys, i ended up putting it on, all back together and runs lovely :)

[Guess-Works.com]

Simple answer is, if you are going to use one, fit a new one rather than an already worn one. ;)

[Vipernoir]

For normal road use and the odd spirited thrash round a trackday, I see no reason not to fit one.
Having built up a few engine over the last week using different chains and duplex kits, it is abundantly obvious that some chains are either already pre-stretched or are not quiiiite the right length to start with.  Baggy is the best description of some of them, so not using a tensioner would be silly.

 

While high rpm may well break a tensioner pad, the sort of engine that is going to see sustained high rpm on a regular basis is almost certainly a competition engine and they should be rebuilt far more frequently than a road engine.  Indeed, for a serious competitor where noise isn't an issue,  a gear driven cam drive would seem more appropriate.

[Cooperman]

For normal road use and the odd spirited thrash round a trackday, I see no reason not to fit one.
Having built up a few engine over the last week using different chains and duplex kits, it is abundantly obvious that some chains are either already pre-stretched or are not quiiiite the right length to start with.  Baggy is the best description of some of them, so not using a tensioner would be silly.

 

While high rpm may well break a tensioner pad, the sort of engine that is going to see sustained high rpm on a regular basis is almost certainly a competition engine and they should be rebuilt far more frequently than a road engine.  Indeed, for a serious competitor where noise isn't an issue,  a gear driven cam drive would seem more appropriate.

+1 on this.

[sledgehammer]

Pity a spring loaded sprocket couldn't be fitted - but sadly no room

 

although I've never seen one in use anyway - I suppose it would be more weight / inertia

[tiger99]

I suspect that a spring loaded sprocket could be fitted, if it was essential, because both the timing cover and backplate can be changed, so space could be made. But if it is a small sprocket, it will be spinning at a horrendous speed, and if large, as you say, inertia rears its ugly head, and although it will hardly affect performance (a very light skim of the flywheel would easily compensate), it will stress the chain during fast acceleration or deceleration, not driving with clutch engaged, but blipping the throttle while stationary.

 

But if you are clever enough to make a sprocket tensioner, you are clever enough to make a complete gear drive, which as already suggested has certain advantages. I don't know if I am clever enough, certainly I would need to buy the gears from an expert manufacturer, but I lack the other vital ingredients, a machine shop, and the motivation to do it. I am far more interested in getting rid of the drop gears, the advantage is potentially much greater, as has been discussed before.

 

Or. fit a timing belt conversion..... (only kidding, I HATE those pesky belts on modern cars, and welcome the swing back to chains that is happening, but not as a certain German manufacturer has done, by intentionally making the chain completely inaccessible in the car....)

 

I remain convinced that the standard tensioner pad is completely unsuitable for a duplex chain,and will have a depressingly short life. It really needs a wider pad, running on all three webs.

 

Note how the aftermarket bodgers, with their amateurishly designed "enhancements", have found this one too difficult! It should not be all that hard to source a tensioner which is suitable, or have one made in one of their back street factories in China, with no quality control or respect for the workers welfare either.

 

Better if one of us forum members happens to find one from a modern engine that is the correct width and can be fitted reasonably easily. The problem will then be solved, properly. If you have any old engine lying about in your garage, it may be worth a quick look at its tensioners.

[Captain Mainwaring]

Hahahaha....off again.

 

Anyone interested could make a tensioner out of a bit of UHMWP alias "umph", same stuff as used on span boxes ( http://www.kana-chai...er/spannbox.htm )

 

Inertia? Hmm....Ya, perhaps people who use terms like inertia should understand what they mean first  (think first before you call me stupid  ) - you'r worried about the effect that a bit of inertia from a sprung tensioner might have on cam chain wear? Think about the power a duplex chain is capable of transmitting.

What kills chains (and they don't stretch in normal use, they wear their pins) is not power transmission, it's radians/sec

 

 

As for gears - think about why gears may be more difficult to us, and remember the old Ford Essex V6 3000cc.

Edited by Captain Mainwaring, 06 May 2014 - 04:19 AM.