Following on from the thread about Honda Jazz tappets needing the inlet manifold removing.
What are peoples views, in general, on design related service costs regarding tappets and their adjustment?
I thought Hydraulic tappets were the accepted way to save on servicing costs.
If so, how does Honda compete on service costs and is their non hydraulic tappet design on the Jazz, typical of the other Oriental marques?
If so, why?
Regards
Edited by oilrag on 30/11/2007 at 08:10
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I don't think the impact on service costs is that great in fairness. Certainly of the cars I've owned with solid tappets (both Fords), the check/adjustment interval is 100,000 miles, and on the Mondeo they were still within tolerance, even at a belated 135k. On these engines however, it is possible to extract the shim by compressing the valve spring with a service tool, or careful use of a flat blade screwdriver, and flicking it out with a watchmakers screwdriver. Literally the only part that needs removing during the whole operation is the rocker cover itself.
I've noticed a lot of engines in recent years seem to have reverted to solid tappets. It's been the norm in the bike world for decades due to the silly revs involved, but car engines don't generally rev any higher than a decade ago. Unless there is some inherent weakness in hydraulic tappets, and I've run two Vauxhalls thus equipped up to 150k+ with no problems, I can't see why things have changed.
Cheers
DP
--
04 Grand Scenic 1.9 dCi Dynamique
00 Mondeo 1.8TD LX
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I've noticed a lot of engines in recent years seem to have reverted to solid tappets. It's been the norm in the bike world for decades due to the silly revs involved but car engines don't generally rev any higher than a decade ago. Unless there is some inherent weakness in hydraulic tappets and I've run two Vauxhalls thus equipped up to 150k+ with no problems I can't see why things have changed.
Emissions!
Solid tappets with modern manufacturing techniques provide more consistent valve timing.
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>> I've noticed a lot of engines in recent years seem to have reverted to solid
I'd say engine construction cost was another factor besides the valve timing factor someone else mentioned. Hydraulic tappets are machined to very high tolerances, and must be quite a costly component part. The car makers these days are looking to save 10p on any tiny part of a car if they can.
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"inherent weakness in hydraulic tappets"
I can't see one (both our Mazdas have them, and rev happily past their 7k redlines) but I wonder if they suffer when extended service intervals are used? Another reason for more frequent oil changes in my book...
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The Jazz is a little unusual in that the inlet air is taken over the top of the engine from the filter, then turns through 90 degrees, to feed down into the ports. Access to the tappets and spark-plugs (at the rear) is obstructed by the inlet assembly. Presume this is done to reduce the width of the engine/ provide a longer inlet tract. Other Honda engines valve adjusters are easy to get at. On VWs we have had intermittent problems with the hydraulic tappets not being fully charged with oil: C15 noises are the result!
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Oil's better than it was, components are better than they were, valves are harder, tolerances are finer and hence wear rate is less.
All the reason you need not to have hydraulic tappets.
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Mike Farrow
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