i dunno if this has been mentioned before or if im just too stupid but here comes a brainfart… i hear from numerous golf/audi owners that a mildly tuned 1.8tdi vag engine is far better than the 1.8t petrol. how would this engine fare in an exige? i know its a diesel and rev range would be very low but the torque would be outstanding
i dunno if this has been mentioned before or if im just too stupid but here comes a brainfart… i hear from numerous golf/audi owners that a mildly tuned 1.8tdi vag engine is far better than the 1.8t petrol. how would this engine fare in an exige? i know its a diesel and rev range would be very low but the > torque would be outstanding >
How do you figure that? Why would it be any better than the 1.8T?
People generally have a misconception that a diesel car has far more torque than an otto (gasoline).
They generally do have more torque because 99% of the times they are turbocharged. It’s the turbo that gives the increase of torque, not the fact that it is a diesel.
Torque is basically a function of displacement and whether or not it has forced induction (supercharged or turbocharged).
What would greatly increase with the use of TDi engines would be MPG, but who cares!
Currently the top 5 cars with more torque are Otto propelled.
I believe the 1st is the SL 65 AMG with over 1000NM
i know its a diesel and rev range would be very low…
Haven’t you just answered your own question?!
I bet it weighs a whole heap more too.
Torque is good for around town and out of slow bends but the S1 Exige (and Motorbikes come to think of it) whoop 'rse on track with next to none.
Ian
IIRC diesel blocks are smaller than the equilivant size in petrol as the increased displacement is from the extra compression…
It was my understanding that the increased compression is what gave diesels more torque, very very long stoke basically…
I don’t know if anyone remembers on 5th gear IIRC there was a diesel rally car, it absolutely flew along! Just at 4000revs
And the diesel entry into Le Mans and such like, as long as it has the power to weight then it doesn’t matter…
The block may be smaller but I thought there was loads of stuff on top (high up where you don’t want it) to feed the fuel (all very technical of me there ).
Now a rally car makes more sense to me, lots of slow bends where going up and down a long rev range doesn’t help a petrol car.
Ian
IIRC diesel blocks are smaller than the equilivant size in petrol as the increased displacement is from the extra compression…
Uhhhh ? What are you on about ? Displacement is purely a function of bore and stroke. Compression ratio has nothing to do with it.
Diesels are heavy mainly to cope with the higher compression and the more rapid rise in pressure when they fire. However the more modern diesels with common rail injection systems control this rate of pressure rise and so are getting lighter all the time.
Still wouldn’t fancy one in a sports car though, having said that my SEAT Ibiza Tdi doesn’t hang about and does over 50 mpg.
Bernard
Yeah, they normally have a mechanical fuel pump attached to the cams / crank pully… But they have no throttle to speak of, they alwasy take all the air they can and the throttle cable just adjust how much diesel is pumped into the cylinders…
But diesel tech is coming along in leaps and bounds! You’ll never get a high revving diesel but it’s getting there…
Personally I agree, a diesel Exige would be like… well, a diesel exige really
Bernard,
sorry it was my understanding (I’m often wrong) that the block could be smaller on a diesel because of the extra compression…
So a 1.9 petrol is of x size at a comp ratio of 10:1 or whatever…
Now a 1.9D can be smaller (remember I could be speaking crap here, it was something told to me by a work collegue who’s “into” his diesels) because if you’re compressing to 30:1 then the stroke must be that much longer to do that… surely?
Surely stoke and bore have some meaning on compression ratio?
Bernard,
sorry it was my understanding (I’m often wrong) that the block could be smaller on a diesel because of the extra compression…
So a 1.9 petrol is of x size at a comp ratio of 10:1 or whatever…
Now a 1.9D can be smaller (remember I could be speaking crap here, it was something told to me by a work collegue who’s “into” his diesels) because if you’re compressing to 30:1 then the stroke must be that much longer to do that… surely?
Surely stoke and bore have some meaning on compression ratio?
Well you are right to an extent, if you had a massively long stroke you could achieve a given displacement by using a smaller bore and hence a shorter block. But using real world numbers you would only save 20 to 30 mm in block length.
You don’t need long stokes to get high compression ratio’s, it just depends on how you design the heads and pistons.
Bernard
My understanding is that you can’t get a high revving diesel engine cos you can’t adjust the ignition timing…
Cheers Bernard, I’ll give him a slap now…
slap
Mike, diesels have no ignition… So there’s no ignition to change The compression is so high that it causes the diesel to combust user pressure rather than a spark…
Please can we not discuss diesal engines
They are loud, rough and dont rev, so have no place in an exige …
Oh Sh*t … maybe they do
Please can we not discuss diesal engines
We should. The only reason that diesels don’t work in peformance cars is that the development hasn’t been done. It’s started (VW Golf GT(D)I, BMW 3 and 5 series variants etc) but not yet finished…
Have you all forgotten the VX 220 based diesel-engined coupe that broke all sorts of records and featured in THIS TV ad? The engine in the Vauxhall was a 1.4 litre (Lotus developed)and it did over 60mpg and almost 200mph (probably in different states of tune and at different times but there is a good compromise in there somewhere…)
And what about the JUDD Le Mans engine, HERE
The people who usually have problems with diesels are those who cannot adjust their driving style to take account of a narrower rev band and therefore destroy the power delivery (like Clarkson, but even he is coming round to appreciate the benfits of diesel and he did (eventually) manage sub 10 mins round the 'Ring in that diesel Jag - if you recall the girl did a 9.13 in it first time out)
I don’t know enough to get into highly technical engineering/power arguments but there is no doubt that a modern diesel delivers good power, excellent torque, amazing economy and longevity.
Lotus have done an awful lot of work on diesel engines (for other people one assumes) but all that expertise will probably not be wasted. Me - I want one.
Regards
And have a read of this:
http://www.pistonheads.com/roadtests/bmw/BMW535d.htm
Very very high praise for the oil burner here
so i wasnt entirely thick to have pondered this idea?
so i wasnt entirely thick to have pondered this idea?
No, not entirely thick - more like 10w / 40
poor effort!!!
My understanding is that you can’t get a high revving diesel engine cos you can’t adjust the ignition timing…
Used to be the case Mike. Not any more, with common rail or Pump Deuse injection systems its all electronically controlled. You can inject the fuel in the quantity you want, at the rate you want and the time you want. That’s why modern diesels are so much better than the old asthmatic smoke belchers. There is a lot more to come apparently, Mercedes are working on an engine with a Magnesium block, might have a Mag head not sure. Anyway it’s going to be pretty light for a diesel.
And no I’m not putting one in your Exige !!
Bernard
poor effort!!!
You’ve not known mike long then, that was good! I laughed!
Ian