petrol or diesel

[Developer]

but that film was made in the day when you could use the word "Queen" with impunity! :?

Yes Alex,

Mention Queen nowaday's and people come over all queer...

 

[prwales]

so we are now more or less conceding that diesel is much more economical and with appropriate turbo's, elecrtonics and gearing can be as quick in terms of acceleration and top speed? Which leaves as the final issue its greater weight and the effect this has on handling. I would suggest this is more of an issue for front wheel drive cars than rwd but an issue none the less. Excess weight up front has a tendency to promote understeer, not a bad thing in moderation but too much is way too much as any Audi driver ought admit

 

[dieselman]

On a car of any size it's insignificant and stiffer springs an anti-roll bars remove the disadvantage anyway, but even if cornering is 'slightly' slower the in gear acceleration will soon more than make up any lost ground.

[YOUTUBE]w8rPhOApnSA[/YOUTUBE]

 

[prwales]

I have not driven the Skoda but have its sister SEAT in diesel form and its handling compared to its other sister the VW Polo in petrol form was awful, with very noticable understeer. Less of an issue in rwd cars though

 

[Alex M Grieve]

I have not driven the Skoda but have its sister SEAT in diesel form and its handling compared to its other sister the VW Polo in petrol form was awful, with very noticeable understeer. Less of an issue in rwd cars though

in the earlier diesel minis, the understeer was compounded by a lack of power steering. All very character building though - and it did teach one the merits of being on the move, forwards or backwards, be it ever so slight, when trying to steer at slow speeds.

 

[Tackleberry]

If I had to drive every day then a diesel would win hands down, but as I don't then I can justify my snort thruster V8 petrol.

On a slightly different note, now Fiat have introduced the Multi Air petrol engines this opens the door for what could be the perfect set up.

Fiat use a conventional camshaft for the exhaust valves, but the inlets are operated by solenoids.

This means they can control exactly when and where and by how much each valve is opened.

What you get is a super efficient engine when pottering around, but when you need to give some beans it completely changes character and produces more power than a conventional engine of the same type can muster.

I believe the idea was devloped by Lotus many years ago (if I'm wrong I do appologise).

The concept then was to operate all valves by solenoids.

Imagine this. At one end of the scale you could have an engine that would idle at 500rpm and be as efficient as is physically possible, and at the other could rev past 20,000 rpm and produce as much power and torque as the type of fuel will allow.

This was of course banned instantly as god forbid it should ever reach a Grand Prix car.

Now with modern electronic control systems you'd simply have a switch to choose how much power and performance you required.............all from one engine.....!

 

[dieselman]

I thought F1 cars used air operated valves for just this reason.

I think Renault are trialling electric solenoid operated valves for road cars. make sense.

 

[Tackleberry]

I thought F1 cars used air operated valves for just this reason.

I think Renault are trialling electric solenoid operated valves for road cars. make sense.

No. The valves have to be operated by camshafts. They also cannot have variable valve timing. This why they idle at 6000rpm....!

The air part relates to the springs, or lack of them. The valves are held shut by extremely high air preassure. This is so there is no chance of valve bounce which is what occures with conventional springs.

Infact the strength of spring required to opperate at those speeds would create huge internal power loses and massive rates of wear.

Simply put the air valve can opperate and massive engine speeds with minimal wear.

 

[Xtractorfan]

Doesnt make sense if their solenoids are made like their coil packs......

 

[Tackleberry]

doesnt make sense if their solenoids are made like their coil packs......

lmao......!

 

[dieselman]

The air part relates to the springs, or lack of them. The valves are held shut by extremely high air preassure. This is so there is no chance of valve bounce which is what occures with conventional springs.

I had never thought about that aspect but it makes sense as a compressed gas can only expand back to it's original volume and doesn't have harmonic frequencies of oscillation, thus no valve bounce.
This is why cars with gas springs don't need such stiff dampers, as the spring can't have resonant frequency oscillation.

 

[prwales]

do you mean gas dampers and softer springs?

 

[Rappey69]

a friend of mine has the fabia blue or green line ?? 1.4 diesel.
Nice to drive, was surprised how nippy it was but best of all short journey into town and its already in the 65+ mpg range..
Very easy to do 100mpg if driven econimically.

 

[dieselman]

do you mean gas dampers and softer springs?

No. Cars that ride on Gas can use less stiff dampers as the 'spring' can't setup a harmonic frequency, so there is no need to control it as much.
Examples of cars on gas springs would be Range Rover, S-Class, Rolls Royce and of course Citroen.