DIESOTTO

[pgarner]

Has anybody else seen this engine. merc has been trialing

basically its a 1.8 twin turbo petrol that can produe238bhp and 291lbft whist getting near diesel economy

it works by using diesel injection setup which is just really getting into petrol cars just now. rather than injecting an air fuel mix it just injects fuel straight into the cylinder. but thats not the clever bit it uses varlible valve timing, once again already available, and variable compression, the clever bit.

the crank sits on its own bearing but the bearing sits on an adjustable one so when cruising at speed the compression is much higher, i cant find actual figs but lets say 8.5: when accelerating to around 15:1 when cruising, but not quite as high as a diesel. the petrol is injected at the exactly correct time so it lows under the pressure rather than needing a spark, same as knocking, but it forced. the engine also uses exhaust gases but rather than being added to the intake the exhaust valves shut before the cylinder is fully empty. meaning there is less o2 in the cylinder and therefore less fuel being added as well as keeping temperatures down and emissions.
the only problem i can see with this engine so far is that merc and GM (owns vauxhall opel for those that dont know) are both saying that this engine is around 8 years away. when you look at how far diesel engines have came in the last 10, common rail anybody, think what they could be like in another 8

merc say the problems they are having with it just now is that the pressure transducer is extremely expensive just know but is required in all 4 cylinders very expensive then. and that the ecu needs to understand physics and that a standard map just isnt good enough

[HDi fun]

They're nice numbers for a 1.8 litre unit.

It's kind of like converging technology. Let's face it common rail diesel injection principles are borrowed from multipoint petrol injection systems. The difference is that diesel is diectly injected and the pressures are very high, something 1300bar or more.

Taking that back to petrol and injecting directly into the combustion chamber is novel, and allows the ECU to inject the fuel in stages, thereby minimising the combustion noise and maxxing out power and economy.

Borrowing technology is looking like a good way for things to really improve across the board. Combine this with a Lexus type hybrid drive and you could well find big cars, with big power and torque numbers from small capacity (therefore lightweight) engines that can deliver 50 plus MPG day in day out.

[pgarner]

dont think merc were even looking at making a hybrid version. but they must be happy with the figures as the are saying it could power the s class with ease

the direct injection is starting to filter through to petrol and showing great results over 40 mpg from 2.0 engines on combined

was reading up on the new A4 the base engine is now the 1.8t rather than a 1.6. my 1.8 averages 32mpg going by govt figures the new unit gain 10 ponies to 160bhp but economy climbs by quite a lot to 40.2mpg, think the old 150 unit was around 33mpg.

just goes to show that car manufactures are noticing that people want better economy, shown by the sharp rise in diesel units, now make up over 40% of all new car sales. but at the same time most people want a car that can be reved to stupidly high limits and this just cant be done with diesels

[waynne]

Didnt Saab play around with dynamically variable cylinder capacity engines? It's clever stuff and the legislation is forcing manufacturers to make greener cars as well as public demand for them.

[pgarner]

dunno bout saab but there part of GM so could be the same engine that they've been playing around with

i stand corrected top gear mag says that merc have looked into coupling it to a hybrid system as well

found some more figs for it .
CO2 output will be similar to the A class diesel
0-62 7.5 in the F700 basically the future long wheelbase s

nice fig for such a large car think what it could do when put in something smaller like the C class

[HDi fun]

Mitsubishi had a 2.4 GDi (gasoline direct injection) engine back in 1999/2000. It was a bit makeshift and was known for problems with burnt piston crowns etc. 7 years is a long time tho.

Mercedes Benz makes probably the world's finest petrol engines bar none.

I agree, the diesel uptake is strong but I'm not so sure that economy in whole life terms is better. You pay more for it, the fuel costs more and the servicing is more frequent and costlier.

I happen to like the stupid high torque figures that good diesels can sling out, but totally agree that they are horrid when revved hard. Mine is red-lined unusually high at 5200 In practice, you don't need to go much over 3000 with it to get very very strong performance indeed. And it's totally hushed at 3000rpm. Also it's long legged, 3000rpm is about 96mph in fifth gear. Which means that 4000rpm is 128 but it sounds horrible, basically.

At the red line tho it sounds like a bag of very smooth nails being shaken very very violently. ie no vibration, and not much noise, but what noise there is is purely nasty!

But there's something so satisfying about silky upchanges at 8000 rpm without a hint of strain or harshness. Diesels will never catch up on that front. Petrol technology is avdancing too, perhaps assisted by the diesel uptake.