Discussion
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Great reading!
Haha, you don't need to tell me not all Mercedes engines are quiet... I have to drive a four-cylinder one
!!
Does the timing chain not contribute a fair amount of this noise, to be fair? Some days I'd rather have a damned near unbreakable timing chain than a quiet engine and cambelt to go 'pop', but that's just because I've studied too many belt-gone engines.
The noisy 16v version of a 190E's engine (ie with cosworth's heads) does somewhat highlight a noise/valvetrain tradeoff though.
Russ
'86 190E noisy engine, '62 Elan loud exhaust
Marquis_Rex said:
As for NVH? Have you ever put a microphone up to a Mercedes engine and recorded it- while comparing it’s NVH waterfall plot to its contemporaries? (Ok…well I don’t suppose you would have
Haha, you don't need to tell me not all Mercedes engines are quiet... I have to drive a four-cylinder one
!! Does the timing chain not contribute a fair amount of this noise, to be fair? Some days I'd rather have a damned near unbreakable timing chain than a quiet engine and cambelt to go 'pop', but that's just because I've studied too many belt-gone engines.
The noisy 16v version of a 190E's engine (ie with cosworth's heads) does somewhat highlight a noise/valvetrain tradeoff though.
Russ
'86 190E noisy engine, '62 Elan loud exhaust
pentoman said:
Great reading!
Marquis_Rex said:
As for NVH? Have you ever put a microphone up to a Mercedes engine and recorded it- while comparing it’s NVH waterfall plot to its contemporaries? (Ok…well I don’t suppose you would have
Haha, you don't need to tell me not all Mercedes engines are quiet... I have to drive a four-cylinder one
Does the timing chain not contribute a fair amount of this noise, to be fair? Some days I'd rather have a damned near unbreakable timing chain than a quiet engine and cambelt to go 'pop', but that's just because I've studied too many belt-gone engines.
The noisy 16v version of a 190E's engine (ie with cosworth's heads) does somewhat highlight a noise/valvetrain tradeoff though.
Russ
'86 190E noisy engine, '62 Elan loud exhaust
Hi ya Pento, chain- assuming they're tight and well tensioned tends to make a whining noise in general.
You can get quiet chains (called 'silent chains')- that have a specially shapped links- smaller profiled- if memory serves- however there is a compromise- I think the chain life isn't as long. Me? I don't mind the noise chains make- I drive a whiney 911-whiney as hell- as are all Porsches- even the water cars- so I'd rather have the durability of chains over belts or double duplex chains over silent chains any day!
I don't know why quite alot of Mercs are whiney - probably PAS pump and FEAD (Front End Accesory Drive) noise.
ok, so i'm getting the picture that SOHC is cheaper to produce an maintain.
an if the mclaren-merc SLR is SOHC then getting good performance cant be a big problem i assume?
but i also assume that as it has fewer parts than a DOHC engine, wouldnt that make it more robust an durable from knocks etc, an simpler to repair?
in fact wouldnt they best be used for armoured cars an tanks which need a tough powerplant.
how about a new military vehicle then - with SOHC engine, mechanaical diffs, an electric aids other than headlamps...?
an if the mclaren-merc SLR is SOHC then getting good performance cant be a big problem i assume?
but i also assume that as it has fewer parts than a DOHC engine, wouldnt that make it more robust an durable from knocks etc, an simpler to repair?
in fact wouldnt they best be used for armoured cars an tanks which need a tough powerplant.
how about a new military vehicle then - with SOHC engine, mechanaical diffs, an electric aids other than headlamps...?
vlc said:
ok, so i'm getting the picture that SOHC is cheaper to produce an maintain.
an if the mclaren-merc SLR is SOHC then getting good performance cant be a big problem i assume?
but i also assume that as it has fewer parts than a DOHC engine, wouldnt that make it more robust an durable from knocks etc, an simpler to repair?
in fact wouldnt they best be used for armoured cars an tanks which need a tough powerplant.
how about a new military vehicle then - with SOHC engine, mechanaical diffs, an electric aids other than headlamps...?
It IS cheaper to produce, if well designed can produce lower friction (if, say using roller rockers and small bearing sizes).
The Merc SLR is a different case, it is a boosted engine- so in order to get more power/torque- it simply is boosted higher. A DOHC engine that is 2 VALVE has allegedly got more freedom in the port design area- hence can get more performance- in practice there are bigger fish to fry- and the difference is minimal (this is when comparing to a cross flow SOHC 2 valve Hemi). Better flowing heads- if Boosted- like the SLR Merc- allow more performance for a given level of boost. On a boosted engine- how much boost the engine can accomodate could be down to something structural- such as the strength of the con rods or what cylinder pressure the pistons can take.
SOHC engines that are 4 valve are rare, the Triumph Dolomite sprint is one example- but it has poor specific out put and torque - even for it's era. The new Mini with it's Brazillian made powerplant with cost as a major priority.
A DOHC engine which is EITHER a 4 valve or a 2 valve with direct acting cams-on top of the valve buckets will be more durable then a 2 valve SOHC hemi engine with rocker arms. Direct acting valve train mechanisms if made with decent materials- rarely need valve clearance adjustment. Witness how good the Jaguar AJV8 engine is.
A SOHC engine with, say a Flat head, NON cross flow design- such as Mk1 and Mk2 VW Golfs or the VR6 Corrado engine is ALSO durable because it is direct acting- but won't give as much performance as a 2 valve SOHC hemi.
I'm sorry for not giving a clear cut, "Yes or no" answer- but it's quite a complex subject!
Marquis_Rex said:
SOHC engines that are 4 valve are rare, the Triumph Dolomite Sprint is one example- but it has poor specific out put and torque - even for it's era.
127 bhp @5750 rpm and 122 ftlbs torque at 4500 rpm is hardly bad for 2003 let alone 1973.
The Sprint was never supposed to be called the Sprint, but the 135, because it made 135 bhp. But BL couldn't manage to guarantee it on every engine (quality control, points & SUs would hardly help). Engines were making 150 bhp on the dyno during development.
Having owned a fair number of these cars I am very aware of their limitations, and I would say the key flaw is the ignition system followed by the cam then the offset bores. With the jackshaft and 90 degree distributor drive arrangement you get a lot of timing variation and so you can never run the engine at the limit reliably.
The offset bored block was a scheme to limit piston slap and a fairly stupid idea. Better to do it with piston offset.
The cam arrangement limits ultimate power because you can't control overlap in the way you need with wild profiles.
The manifold is a dual path log (1+4), 2+3 and not unrestrictive enough for ultimate power.
However with all of those handicaps the engine can still make 240 bhp RELIABLY on standard rods, pistons, crank, flywheel, a fettled manifold, twin 48 DCOEs, hot cam, porting and new valves to a 1975 specification.
Today's engines deliver their advantages not through inherently good design but mostly by electronics made available and improved in the past 20 years.
If you want to see how much technology HASN'T advanced, take a look at this. All from the 30s and 40s.
www.spitfiresociety.demon.co.uk/engines.htm
Interesting insight into the Dolomite Sprint and interesting link as always Gavin . I really didn't know about the "135" aspect. I did read something about angled cylinder head bolts or something. .Don't get me wrong I like the Dolomite Sprint a lot , I like the way they look and their characterful dash layout. It wouldn't be too bad if it was left at that- but when something is overhyped….What I don't like is the way that just because Triumphs are British they are hailed as being incredible land mark in engineering in it's day.
In terms of the 127 Bhp output being good for a 4 valve
In its day-almost 64 Bhp/litre and barely 10.4 bar BMEP.
1973 BMW 2002 tii achieved 130 Bhp and 177 Nm of torque from a 2 litre engine (over 65 Bhp./litre and 11.1 bar BMEP!) that was only a TWO valve hemi (This engine had a lot more in hand too- with other modded ones making a lot more).
1974 Alfa Romeo Alfetta achieved 123.7 Bhp and 167 Nm from a 1.8 litre TWO valve hemi long stroke (69.5 BHP/litre and 11.8 bar BMEP)
Original 1976 VW Gold GTI achieved 110 Bhp and 137 Nm from a 1.6 litre 2 valve- not even a hemi head- a flat head.(69 Bhp/litre and 10.8 bar BMEP)
A performance two valver should be producing 60 plus BHP per litre and over 10 bar BMEP even in the 1970s while a 4 valver should be up there at over 70 Bhp/litre and over 11 bar BMEP to make it worth having all the complexity of this arrangement. In this case it was used to bolster the output figures of a venerable design.
If the Triumph was hailed on character and classic charm alone- I can TOTALLY understand this. But
I've never been a fan in adding technology for technologies sake- where there is very little benefit in having it-compared to a well honed design without the complexity, cost or friction. Nevertheless the Triumph will be hailed as an engineering feat of technology, probably just because it's British. It's this kind of blinkered – "we make better stuff then any of this foreign crap" that was contributory to a lot of BL stuff being non competitive in the 1970s. I think subsequently- it was our acknowledgement of the competence of competitors from the continent and Japan that subsequently improved products like Jaguars.
Back to the Dolomite- these will continue to fetch very high prices second hand, while the others mentioned above (with possible exception of the VW Golf) will be left to rot and fetch bargain basement prices. The parallel of this is engineers themselves not getting recognised or technical merit for their achievements.
PS: I talked to D Zukerman recently and he told me he visited you in Mi and about your garage clearout!
In terms of the 127 Bhp output being good for a 4 valve
In its day-almost 64 Bhp/litre and barely 10.4 bar BMEP.
1973 BMW 2002 tii achieved 130 Bhp and 177 Nm of torque from a 2 litre engine (over 65 Bhp./litre and 11.1 bar BMEP!) that was only a TWO valve hemi (This engine had a lot more in hand too- with other modded ones making a lot more).
1974 Alfa Romeo Alfetta achieved 123.7 Bhp and 167 Nm from a 1.8 litre TWO valve hemi long stroke (69.5 BHP/litre and 11.8 bar BMEP)
Original 1976 VW Gold GTI achieved 110 Bhp and 137 Nm from a 1.6 litre 2 valve- not even a hemi head- a flat head.(69 Bhp/litre and 10.8 bar BMEP)
A performance two valver should be producing 60 plus BHP per litre and over 10 bar BMEP even in the 1970s while a 4 valver should be up there at over 70 Bhp/litre and over 11 bar BMEP to make it worth having all the complexity of this arrangement. In this case it was used to bolster the output figures of a venerable design.
If the Triumph was hailed on character and classic charm alone- I can TOTALLY understand this. But
I've never been a fan in adding technology for technologies sake- where there is very little benefit in having it-compared to a well honed design without the complexity, cost or friction. Nevertheless the Triumph will be hailed as an engineering feat of technology, probably just because it's British. It's this kind of blinkered – "we make better stuff then any of this foreign crap" that was contributory to a lot of BL stuff being non competitive in the 1970s. I think subsequently- it was our acknowledgement of the competence of competitors from the continent and Japan that subsequently improved products like Jaguars.
Back to the Dolomite- these will continue to fetch very high prices second hand, while the others mentioned above (with possible exception of the VW Golf) will be left to rot and fetch bargain basement prices. The parallel of this is engineers themselves not getting recognised or technical merit for their achievements.
PS: I talked to D Zukerman recently and he told me he visited you in Mi and about your garage clearout!
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