Engine Reliabilty Survey | Motoring discussion | Back Room Forum

Tue 22 Jan 2013 16:46

Engine Reliabilty Survey - Sulphur Man

Interesting figures release by Warranty Direct, although, as ever, not to be taken as absolute gospel, due to the different products manufacturers make.

Good result for Fiat, although the only make fairly conventional 4-cyl and smaller engines up to 2.0 in size, so perhaps they should do well.

The jump in figures from Pos 3 (Merc) to Pos 2 (Toyota) to Pos 1(Honda) fairly jumps off the page. Makes me wonder if Warranty Direct simply dont have many Toyota's or Honda's on their books, as the owners probably dont feel the need to buy a 3rd party warranty for cars that have such renowned relability.

At the other end of the scale. Audi is in the doghouse. Now this is more damning, because whether Warranty Direct have only a few Audis on their books, or thousands, the ratio of engine failures is terrible. Seems to back up the VAG horror stories posted all over the web these past few years

www.telegraph.co.uk/motoring/news/9815860/German-c...l

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Tue 22 Jan 2013 16:56

Engine Reliabilty Survey - unthrottled

At the other end of the scale. Audi is in the doghouse. Now this is more damning, because whether Warranty Direct have only a few Audis on their books, or thousands, the ratio of engine failures is terrible

Er, no. Ratios only become meaningful when you have a statistically large set. Otherwise one faiilure can be the difference between "infinite" reliability (zero failures) and 50% (one out of two engines).

Quite how Audi can fare so differently from Volkswagen, Skoda, and Seat (which all use the same engines) is beyond me. Lots of other manufascturers share engines (Nissan and Renault for example). The Mini's engines are designed built by a consortium including BMW, PSA and Ford,

Peugeot and Citroen certainly use the same engines, but aren't juxtaposed in the league table. Sounds like WD carp to me.

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Wed 23 Jan 2013 17:34

Engine Reliabilty Survey - SteveLee

At the other end of the scale. Audi is in the doghouse. Now this is more damning, because whether Warranty Direct have only a few Audis on their books, or thousands, the ratio of engine failures is terrible

Er, no. Ratios only become meaningful when you have a statistically large set. Otherwise one faiilure can be the difference between "infinite" reliability (zero failures) and 50% (one out of two engines).

Quite how Audi can fare so differently from Volkswagen, Skoda, and Seat (which all use the same engines) is beyond me. Lots of other manufascturers share engines (Nissan and Renault for example). The Mini's engines are designed built by a consortium including BMW, PSA and Ford,

Peugeot and Citroen certainly use the same engines, but aren't juxtaposed in the league table. Sounds like WD carp to me.

A significant source of Audi engine failure (oil pump drive) only affects the longitudinally mounted 2.0 diesel engines primarily used in certain Audi models. This means that the stats would be much worse for Audi which have more of the type of engine which are known to failure – add to that the cam failure issue experienced in the Audi-specific V8s and there’s your answer. Of course more expensive Audis will also generally have high specific variants of any particular engine which will be less reliable by default.

As for Peugeot vs Citroën, the former are much heavier users of the group's most unreliable engine, the BMW MINI 1.6 turbo that snaps cam chains. Peugeot sold this engine over a year before it was fitted to any Citroën model and had many more cars in the range using this engine.

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Tue 22 Jan 2013 21:09

Engine Reliabilty Survey - Cyd

For me, the most glaring ommision from this article (and there isn't even any reference or link to it) is any kind of description of the type of failures that occured. The description "engine failure" is extremely vague. What does this mean? What counts as engine failure? Is a failed coil pack an engine failure?

It's obvious why MG languish down at the bottom of the list - it's all those K series head failures. Our Rover 25 suffered burned out exhaust valves. It cost about £800 to get fixed, but this included new water pump and all fluids and it was due a belt change anyway. The point here is that although inconvenient (and we could have done without the bill) this was not a terminal engine failure. Perfectly repairable and now the car is running like new 2 years later.

Did all those Audis suffer terminal engine failure, a thrown rod for example. I doubt it.

For me, this table should be showing average repair cost. That would be more useful information if they are only gonna use a single parmetric. Would give at least some indication of the severity of the typical failures.

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Wed 23 Jan 2013 09:19

Engine Reliabilty Survey - thunderbird

For me, the most glaring ommision from this article (and there isn't even any reference or link to it) is any kind of description of the type of failures that occured. The description "engine failure" is extremely vague. What does this mean? What counts as engine failure? Is a failed coil pack an engine failure?

For me, this table should be showing average repair cost. That would be more useful information if they are only gonna use a single parmetric. Would give at least some indication of the severity of the typical failures.

Just using the word "engine failure is nonsense".

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Wed 23 Jan 2013 01:40

Engine Reliabilty Survey - SteveLee

Good result for Fiat, although the only make fairly conventional 4-cyl and smaller engines up to 2.0 in size, so perhaps they should do well.

Couldn't be further from the truth, FIAT's multiair system gives you variable lift, cam profile and duration on the inlet valves - individually mapped too. By far the most advanced system of its kind fitted to production passenger vehicles. Multiair makes Honda's VTEC and BMWs valvetronic look prehistoric.

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Wed 23 Jan 2013 07:43

Engine Reliabilty Survey - Happy Blue!

The mulitair may do all that, but according to all reports, it needs to have its head revved off to get any performance and it is not that economical in the real world.

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Wed 23 Jan 2013 08:48

Engine Reliabilty Survey - TeeCee

The mulitair may do all that, but according to all reports, it needs to have its head revved off to get any performance and it is not that economical in the real world.

Actually the best system ever for variable induction timing was the VVC system on the Rover 1.8 "K" series. Shame about that engine's other issues.

I drove an MGTF 160 once while helping a mate buy. While the additional power was there and noticable, what was really impressive were the bootfulls of "grunt" all the way through the rev band. It'd pull like a train in any gear from nothing on the clock right up to the red line. Hardly surprising, if you look at the dyno plots on those things, the power and torque bands are astonishingly wide.

Uniquely this means that the performance version is actually a far more pleasant drive when merely footling around than the 135 variant in "cooking" tune.

Silly SOB still bought a 135. It was a tidier car and cheaper, but I'd still have bought the 160 for the free grin that comes with that fantastic engine.

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Wed 23 Jan 2013 10:22

Engine Reliabilty Survey - Collos25

Would believe anything WD said.

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Wed 23 Jan 2013 15:42

Engine Reliabilty Survey - SteveLee

The mulitair may do all that, but according to all reports, it needs to have its head revved off to get any performance and it is not that economical in the real world.

Actually the best system ever for variable induction timing was the VVC system on the Rover 1.8 "K" series. Shame about that engine's other issues.

The Rover VVC system was very good and was continuously variable unlike many other single or two phased cam timing systems, the only downfall was the complexity of the system reduced potential rev ceilings compared to inferior systems such as Honda's VTEC. The 143ish PS Rover VVC engines were gems before they ruined them chasing headline horsepower figures. If you think the 160 MGF was great, drive a 143ps VVC in a Rover 25 - in gear (real world) accelaration was stunning - any gear any revs - gone before the VTEC Civic R driver has found the "right" gear.

However, multiair isn't just a cam phasing system, it changes duration, ramp up and ramp down of the inlet valve timing along with (effective) phasing. For example at low revs the inlet valve is opened late, closed before too much overlap occurs and has a much faster ramp up "snapping" the valve open in tune with predicted inlet pulses to encourage pulse tuning improving inlet velocity. Pulse-tuning can cause a useful ram air effect. Similarly unwanted pulses can disturb induction and can be “mapped out” with multiair (to some degree) at particular load/throttle combinations where they occur most. So inlet valve timing ramp up/down and duration can be influenced in real time mapped to engine load - more primitive systems such as VVC and VTEC just phase cam timing based on rpm alone. Multiair is more about reducing emissions rather than chasing power, ie keeping the inlet mixture clean and untainted by waste gases which are always a compromise with "normal" cam timing systems. As sufficiently powerful solenoid valves are still too slow (and require too much power) for passenger car engines (to give truly variable and mappable valve-timing through camless engines) FIAT's system is a clever compromise utilizing today's technology to good effect.

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Wed 23 Jan 2013 15:56

Engine Reliabilty Survey - unthrottled

However, multiair isn't just a cam phasing system, it changes duration, ramp up and ramp down of the inlet valve timing along with (effective) phasing

Valvetronic did pretty much the same thing. It's basically a two piece rocker system with a moveable fulcrum. BMW used a stepper motor, Fiat use hydraulics. No real difference in the end result. The ability to vary the valve timing is limited, not by the valvetrain mechanism, but by the geometry of the system. Very early inlet valve opening or very late exhaust valve closing are nonsensical even though a cam phaser may permit such events. piston-valve clearances are also a problem in high compression engines late exhaust closing or early inlet opening.

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Wed 23 Jan 2013 17:22

Engine Reliabilty Survey - SteveLee

Valvetronic did pretty much the same thing. It's basically a two piece rocker system with a moveable fulcrum. BMW used a stepper motor, Fiat use hydraulics. No real difference in the end result. The ability to vary the valve timing is limited, not by the valvetrain mechanism, but by the geometry of the system. Very early inlet valve opening or very late exhaust valve closing are nonsensical even though a cam phaser may permit such events. piston-valve clearances are also a problem in high compression engines late exhaust closing or early inlet opening.

Valvetronic is much simpler system to control lift of the entire inlet camshaft, it cannot be mapped to individual cylinders and it cannot react anywhere nearly fast enough to be employed in the same manner as multiair, Valvetronic can be used to employ the inlet valves as the primary throttle which is excellent, combined with altered phasing of the camshafts an effect can be made on duration but nowhere near to the same precision or speed of multiair. As I have been involved in the software surrounding the very valve opening and closing you claim to be nonsensical - I'll take the point with the pinch of salt it deserves. Multiair can reduce lift to minimal amounts to circumvent clearance issues when required. Valvetronic does have its advantages but multiair offers significant improvements in capability thanks to the massively quicker reaction speed and the ability to control individual valves. The kind of stuff multiair is being used for in the development lab could only be dreamed of by a valvetronic equipped development engineer. Watch this space, FIAT are being very conservative with early implementations.

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