Is diesel dead?

JHMEG

zilog_jones wrote: »

The Honda Accord 2.2 i-DTEC diesel would like to have a word with you. I'm not taking any particular side on this argument though...

Actually, the i-DTEC engine is not on sale yet. And secondly Warranty Direct only cover cars that are out of manufacturers' warranties. That means 2005 or older Accords. The diesel was only introduced in 2005.

JHMEG

Matt Simis wrote: »

Please educate me on how torque means nothing thanks to the magic of gears. As of today I drive a car with 605ft/lbs of torque

At the end of the day: ALL power/torque comes from burning fuel. Burn more, get more. We agree so far.

A BMW M3 at 8000rpm is burning fuel *far* faster than a W10 at 3250rpm (you can see where gearboxes are useful). We still agree?

Thanks to gear reduction at any given practical speed the M3 would be putting more torque on the road.

A Phaeton W12 TDI at 3250rpm, at 30mph, is putting 550 foot pounds on the road.
An M3 at 8000rpm, at 30mph, is putting down somewhere in the region 850 foot pounds, (340 x 2.5, torque figure at 8000rpm not available, but I'm assuming slightly off max of 367 at 340), thanks to gear reduction.

Bottom line, a petrol M3 at 8000rpm puts down more torque on the road than a 6.0L W12 TDI Phaeton can.

Matt Simis

JHMEG wrote: »

An M3 at 8000rpm, at 30mph, is putting down somewhere in the region 850 foot pounds, (340 x 2.5, torque figure at 8000rpm not available, but I'm assuming slightly off max of 367 at 340), thanks to gear reduction.

Bottom line, a petrol M3 at 8000rpm puts down more torque on the road than a 6.0L W12 TDI Phaeton can.

Thats entirely incorrect. And for the record comparing a brand new sports compact to a 5 year old big saloon is bizarre. And you are mixing up the V10 (not W) TDI and W12 Petrol (there is no V12 TDI in VW cars, the Audi V12 TDI is much, much faster and not covered here). But since you choose the cars..
Apart from the fact 8000RPM at 30mph would have to be in 1st gear (where the gear ratio is optimised even more on diesels than the petrol anyway) which is simply moronic from a driving perspective, you are completely ignoring that gear ratios drop dramatically from 1st to 6th and the reality that a diesel can drop gears just as easy.


The correct way to determine power to the floor between cars is axle torque. This is expressed as such:
Axle TQ = Fly Wheel TQ * Trans Gear Ratio GR * Final Drive Gear Ratio

I admit this complete bull**** about gears (from you and several others) annoyed me so much that I worked out the Axle torque in Excel for both a M3 V8 and V10 TDI (Touareg version) for each relevant RPM in several gears. For the sake of simplicity I left out friction and transmission losses, this is pure and simple performance.


In the above I even put the Touareg in 4th, to artificially reduce the gear torque multipling effect and put the BMW in 3rd to maximise it (and balance vs speed target). The M3 still puts less torque to the ground, in every situation than a big fat diesel.
Putting them both in 1st (as you seem to imply) only makes the diesel look better as it has higher Gearing Ratio, and yes obviously, a V10 TDI can reach 30mph in 1st.
Im not saying a Touareg V10 is "faster" than an M3, but it does, by the numbers, put more torque to the ground. Incidentially the E92 M3 and V10 TDI Phaeton (not Touareg) have similar top speed (verified) at 300 to 310kph.


Data, go check it yourself:

V8 M3 Gear Ratios:
1st: 4.06
2nd: 2.37 (same as V10 TDI)
3rd: 1.58
4th: 1.19
5th: 1
6th: 0.87
Final Drive: 3.85
http://www.m3post.com/forums/showthread.php?t=102454&page=2


V10 Touareg Gear Ratios (note how similar the diesel and petrol cars ratios actually are)
1st: 4.15
2nd: 2.37 (same as V8 M3)
3rd: 1.56
4th: 1.16
5th: 0.86
6th: 0.69
Final Drive 3.27
http://cars.rte.ie/newcars/index.cfm?fuseaction=Details&vehicle_id=75910320071022&strSpecs=SSCIRL2002

Actual, tested and verified Performance Charts for both cars, used above in formula:
http://www.rri.se/popup/performancegraphs.php?ChartsID=675
http://www.rri.se/popup/performancegraphs.php?ChartsID=793

Torque vs HP
http://www.mustangsandmore.com/ubb/DanJonesTorqueVsHP.html

Calculate MPH for given gear:
http://www.jekylhyderacing.com/spg.htm
ie M3 should hit 108MPH in 3rd

JHMEG

Are you seriously telling us that an M3 at 2500rpm in 2nd is putting down more torque than it is at 7800rpm?

Where are wheel sizes in your calculations?

From here:
In just about every vehicle on the road, gears are used to increase or decrease rotational speeds and torque. If the input gear is smaller, the output torque is higher.

Matt Simis

JHMEG wrote: »

Are you seriously telling us that an M3 at 2500rpm in 2nd is putting down more torque than it is at 7800rpm?

Where are wheel sizes in your calculations?

From here:
In just about every vehicle on the road, gears are used to increase or decrease rotational speeds and torque. If the input gear is smaller, the output torque is higher.

Look at the Swedish lab results (its linked), everyone (i thought) knows that peak torque and peak BHP are not at the same time (virtually impossible). Tire size is only needed to determine speed and RPM at speed calculations. Axle torque is simply that, torque at the axle.
No one is disputing lower gear = higher torque, the figures above actually prove that?

I fully disclose my data, now why dont you go explain how the M3 is putting down 850ft/lbs and the TDI 550ft/lbs in the same scenarios.


EDIT: Just to clarify, Im not "debating" this with you, I just think you are flat out wrong. The cancer angle you used to take with your diesel bashing likely has more legs on it than this.

zilog_jones

JHMEG wrote: »

Actually, the i-DTEC engine is not on sale yet. And secondly Warranty Direct only cover cars that are out of manufacturers' warranties. That means 2005 or older Accords. The diesel was only introduced in 2005.

I stand corrected. I should have known you wouldn't be wrong with something like that

On closer inspection of that list, it is quite apparent that all the high ranking cars are not well known for their diesels or are not available with a diesel at all (most Hondas, Mazdas, all Subarus, RAV-4, IS200). But then we get to the Land Cruiser at 14 - I don't know about back then but there's no petrol models currently sold in the UK, 120 (Prado) or 200 series.

Maybe only big diesels are reliable? :pac:

Stevie Dakota

This is good, JHMEG against the ropes, ding ding, round 2.

Biro

Matt Simis wrote: »

Look at the Swedish lab results (its linked), everyone (i thought) knows that peak torque and peak BHP are not at the same time (virtually impossible).

Scania R560 manages it!

Zube

JHMEG wrote: »

Are you seriously telling us that an M3 at 2500rpm in 2nd is putting down more torque than it is at 7800rpm?

Of course. In any particular gear (in this case 2nd) the torque at the axle will mirror the engines torque curve.

Your whole "gears make torque irrelevant" argument requires that you change gears to multiply axle torque.

Presumably you drive around in first gear a lot.

JHMEG

Matt Simis wrote: »

No one is disputing lower gear = higher torque, the figures above actually prove that

???

That's what I've been saying all along??

Matt Simis

JHMEG wrote: »

???

That's what I've been saying all along??

Youre a troll.

Everyone else, see above, its pretty bloody clear that "gears" dont make up for lack of torque when comparing petrol to diesels as diesels (shockingly) have gears too and have more torque at everypoint and sometimes even in higher gears. E92 and Anan1 should know better too.

End of discussion, you were way wrong.

JHMEG

Matt Simis wrote: »

Youre a troll.
End of discussion, you were way wrong.

With statements like that Matt you must be right.:rolleyes: Sorry to have ever doubted your authority:rolleyes:

Simple example of gears and torque. The lad on the 10 speed racer. He can't go up hill in any gear apart from 1st. Why is this? Because the torque has been multiplied via gearing (gearbox). He's peddling like fcuk in 1st gear too (engine speed).

EDIT: someone did the maths here a while back (which made me see the light) and showed that a Civic Type-R at high rpms in a low gear is putting down more torque thanks to gearing than a Transit that nominally has about 3 times the torque.

moleyC

I'm not against diesel, they are definitely more flexible(with turbocharging) for daily driving, even though I have a petrol, but that is mainly because I get the bus to work and keep the car for mostly pleasure.

But Matt I see your reasoning but just taking your figures for lets say the 2nd gears becsause the ratios are the same, do you not have to take into account time.

I mean the diesel engine has 442lb/ft @ 3409 rpm but the petrol has 238lb/ft @ 7821

over a certain ammount of time the petrol will have a 2.29 advantage, from 7821/3409

therefore 238 * 2.29 = 546

and thats where the petrol takes it's advantage.

It is better to make torque at high rpm than at low rpm

Matt Simis

moleyC wrote: »

I'm not against diesel, they are definitely more flexible(with turbocharging) for daily driving, even though I have a petrol, but that is mainly because I get the bus to work and keep the car for mostly pleasure.

But Matt I see your reasoning but just taking your figures for lets say the 2nd gears becsause the ratios are the same, do you not have to take into account time.

I mean the diesel engine has 442lb/ft @ 3409 rpm but the petrol has 238lb/ft @ 7821

Thats starting to get complicated without exact figures (ie cars, distance etc) unless we start quoting random numbers. But generally the time it takes a diesel to redline is roughly similar to a petrol, the numbers (RPM) are different. The diesel (and that petrol e92 M3 almost does it too interestingly) has good torque across the rpm range, obviously decreasing but from a much stronger start.

So no, unless you can provide some very specific figures and scenarios I dont think "time" itself has to be placed into the equation when working out axle torque per gear (and neither did the guys who wrote the articles I linked to, read them!).

Stevie Dakota

Lads, get a room.

In answer to the OP's question - no.

Marcus.Aurelius

zilog_jones wrote: »

Marcus.Aurelius: I thought the Carina E diesels were naturally aspirated?

If you check this link you can see that both normally aspirated and turbo diesels were used.

We were both right!!! :D:D

Incidentally, that site is very good for comparing different engine combinations in different wagons.

R.O.R

JHMEG wrote: »

That means 2005 or older Accords. The diesel was only introduced in 2005.

Very surprised at the mis-information from JHMEG regarding any Honda's. The Accord was available, pre facelift, in 2004 with the Diesel Engine. I can be positive of this as an 04 Accord Executive was delivered back to me today with a distinctive Diesel rumble when I drove it around the back (not to mention the I-CDTi badging on the back).

130,000km on the clock and running sweet as a nut.

JHMEG

R.O.R wrote: »

Very surprised at the mis-information from JHMEG regarding any Honda's.

Hardly mis-information being out by a year. Big swing.