bhp question..

[Django x2]

Exactly, so it's not replicated every day. The diesel will pull away given two drivers who drive appropriately, the diesel will always be in the right gear to pull away until the speeds reach sillyness. At what point do drivers stop dropping down gears to get in the power band?

For a more interesting scenario, you can advise me on the following. My 235bhp E60 530d consistently pulls away from my friends E46 330ci Coupe from around 25/35mph onwards. Sure, it never leaves it, but the coupe never catches it. I'm sure it would evetually, if speeds allowed but we don't go there In full acceleration you wouldn't drop down gears (in a sprint), you can only hold them longer in a petrol

And for anyone considering his driving ability, he's a rapid response driver. (They use diesels too btw, put probably from a tax point of view!)

 

[Dogbreath]

Exactly, so it's not replicated every day. The diesel will pull away given two drivers who drive appropriately, the diesel will always be in the right gear to pull away until the speeds reach sillyness. At what point do drivers stop dropping down gears to get in the power band?

I don't understand this...why would the diesel always be in the right gear but the petrol wouldn't? This would only be the case if the driver didn't put the petrol in the right gear. The two engine types require a different driving style to get the best performance from them...you can hardly point to the petrol and say it's slow if you drive it like a diesel. You might as well say the diesel is crap because if you take it up to the red line in each gear it's slow.

As for your friend 330i...being a rapid response driver is no guarantee of being able to extract the best performance from a car. They are trained to drive as safely as possible at higher speeds, not how to get the best 0-60 time. Suggest you swap cars and see if the results are the same

 

[Dr Who]

As for your friend 330i...being a rapid response driver is no guarantee of being able to extract the best performance from a car. They are trained to drive as safely as possible at higher speeds, not how to get the best 0-60 time. Suggest you swap cars and see if the results are the same

This is true, my fathers job was training rapid response drivers and they were trained to drive at safest possible fast speed rather than fastest possible speed.

 

[Django x2]

I don't understand this...why would the diesel always be in the right gear but the petrol wouldn't? This would only be the case if the driver didn't put the petrol in the right gear. The two engine types require a different driving style to get the best performance from them...you can hardly point to the petrol and say it's slow if you drive it like a diesel. You might as well say the diesel is crap because if you take it up to the red line in each gear it's slow.

As for your friend 330i...being a rapid response driver is no guarantee of being able to extract the best performance from a car. They are trained to drive as safely as possible at higher speeds, not how to get the best 0-60 time. Suggest you swap cars and see if the results are the same

It's simple. In a 0-60 or 0-100 sprint, you both have to start from 0. Therefore, 1st gear. There is no other gear to suit the cars power for maximum acceleration at this point. You both swing round your rev ranges (limited for some ) and then change to 2nd. There is no better gear to be in for maximum acceleration at this speed point, etc, etc, etc. Both cars, during a sprint, will always be in their best suited gear.

We have swapped cars before now too. Result was the same.

 

[PMKeates]

Lucero... I'm not quite sure what you're trying to argue.

You have a 530d and an E46 330i, and they have equal performance. This is no surprise, as they have similar weights and power outputs, with the extra weight of the 5 is offset by the extra torque. Therefore, this is what one would expect, and supports almost exactly the point I made with the Focus. Same power output diesel and petrol, will almost always have the same performance as the weight the diesel engine brings almost always offsets the torque benefit.

E60 530d - 235 PS - 1655 Kg - 500 Nm - 142 HP/ton, 302 Nm/ton
E46 330i - 231 PS - 1505 Kg - 300 Nm - 153 HP/ton, 199 Nm/ton.

So the car with more than 50% extra torque per ton, barely accelerates any harder?

 

[Dr Who]

And the diesel will have a different final drive ratio to ensure it makes more use of its increased torque and less reliant on rpm.

 

[Dogbreath]

It's simple. In a 0-60 or 0-100 sprint, you both have to start from 0. Therefore, 1st gear. There is no other gear to suit the cars power for maximum acceleration at this point. You both swing round your rev ranges (limited for some ) and then change to 2nd. There is no better gear to be in for maximum acceleration at this speed point, etc, etc, etc. Both cars, during a sprint, will always be in their best suited gear.

We weren't talking about a sprint, we were talking about a petrol and diesel Focus being driven in an everyday manner between 50-75mph. Your argument was that the diesel would always be in the right gear to do this as quickly as possible...my argument is a good driver will make sure any vehicle, diesel or petrol, is in the optimum gear if they need the best acceleration.

 

[atpbx]

Lucero... I'm not quite sure what you're trying to argue.

You have a 530d and an E46 330i, and they have equal performance. This is no surprise, as they have similar weights and power outputs, with the extra weight of the 5 is offset by the extra torque. Therefore, this is what one would expect, and supports almost exactly the point I made with the Focus. Same power output diesel and petrol, will almost always have the same performance as the weight the diesel engine brings almost always offsets the torque benefit.

E60 530d - 235 PS - 1655 Kg - 500 Nm - 142 HP/ton, 302 Nm/ton
E46 330i - 231 PS - 1505 Kg - 300 Nm - 153 HP/ton, 199 Nm/ton.

So the car with more than 50% extra torque per ton, barely accelerates any harder?

No, but at a given road speed, it is doing less work, because it is able to pull a higher gear at a lower RPM.
Performance isnt just out right speed and 0-60, the engine with the most torque will be able to work less to pull a given weight, across a given distance.

(Work being defined as RPM)

 

[The Running Man]

We weren't talking about a sprint, we were talking about a petrol and diesel Focus being driven in an everyday manner between 50-75mph. Your argument was that the diesel would always be in the right gear to do this as quickly as possible...my argument is a good driver will make sure any vehicle, diesel or petrol, is in the optimum gear if they need the best acceleration.

well not really, i mean, do you drive at 6k rpm on the motorway in your 1.6 focus @ 50mph just incase you need to 'take a derv?

most ppl will drop to 4-5th gear on the motorway in petrol which will be 3-4k rpm...so well out of what is peak power. the lag time for you to reach peak power is higher than if you were already sat at 2k rpm in a diesel waiting to nail it...all the way to 4k rpm! thats why petrol need to drop a gear to get closer to the powerband faster..

but really last page i was making this 'too complicated' and now everyone is comparing petrol to dervs when that was not the question asked!!

 

[[TW]Fox]

well not really, i mean, do you drive at 6k rpm on the motorway in your 1.6 focus @ 50mph just incase you need to 'take a derv?

most ppl will drop to 4-5th gear on the motorway in petrol which will be 3-4k rpm...so well out of what is peak power. the lag time for you to reach peak power is higher than if you were already sat at 2k rpm in a diesel waiting to nail it...all the way to 4k rpm! thats why petrol need to drop a gear to get closer to the powerband faster..

Why would you ever need maximum attack on a MOTORWAY? You maintain a set speed for hours on end unless there is a big queue in which case you cant rocket off from 30-70 in 3 seconds unless you wish to drive into the person in front.

I never need to use anything but 5th to accelerate from anything above 40mph on the Motorway in my car because there just isn't the need to accelerate really fast unless you are joining on a slioroad in which case hello gearbox surely?

Typical diesel owners arguement, just comparing utterly meaningless made up situations.

 

[The Running Man]

okay...?

fox ppl are saying that a petrol will never keep up with a diesel on a 50-75 pull.. im saying that in many situations this appears to be true because in real life on the motorway ppl dont drive their petrols at peak rpm at 50mph..they tend to cruise as you say... therefore if you drop the accellerator its going to take you more time to hit peak rpm than it does to hit peak torque in a diesel, giving the impression that a diesel is faster. but thats just a perception because most drivers in petrols arent ready to go! (in teir 1.6 focus).

if i sit at 6000rpm in my 1,8 petrol ready to boot it when the time comes even with its 130 torque, i will be faster than most 2.0 tdi at 2-3k rpm even if they have 180-200lb torque... but that all comes down to gearing and the relative characteristics of a turdo diesel.

 

[PMKeates]

No, but at a given road speed, it is doing less work, because it is able to pull a higher gear at a lower RPM.
Performance isnt just out right speed and 0-60, the engine with the most torque will be able to work less to pull a given weight, across a given distance.

I was talking maximum possible performance.

Either way, this is all irrelevant to the original question, which has been answered by myself and others probably a dozen times

 

[[TW]Fox]

okay...?

fox ppl are saying that a petrol will never keep up with a diesel on a 50-75 pull.. im saying that in many situations this appears to be true because in real life on the motorway ppl dont drive their petrols at peak rpm at 50mph..they tend to cruise as you say... therefore if you drop the accellerator its going to take you more time to hit peak rpm than it does to hit peak torque in a diesel, giving the impression that a diesel is faster. but thats just a perception because most drivers in petrols arent ready to go! (in teir 1.6 focus).

But its an entirely irrelevent situation, when would you find yourself casually drag racing a diesel on the Motorway?

It's as retarded as those ridiculous 'A Skoda Fabia does 60-61 in 6th quicker than an Audi RS4!11111111' stats.

 

[Howard]

Quite, I've never dropped a cog at motorway speeds. All of my cars have had enough power in 5th at these speeds to overtake fine.

I'm also not going to dispute that a decent diesel will do it faster

 

[Demon]

All this rollocks over torque is all hypothetical stuff, would-a, could-a, should-a

What we need are simple Thrust Curves for the cars, like the used to do with bikes..

This takes gearing etc into account, you can see when/where to change gear in one easy graph, and you have a much clearer understanding of exactly how much accelerative force you have at any speed for each gear, and all arguments can be put into perspective..

e.g.
http://www.bikegraph.co.uk/TorqueGraphs.php

click 'add' on at least one bike, go down the bottom and click "Draw Graphs" for an example..

All you need is the torque curve and gear ratios for a car and you can work it all out..

 

[The Running Man]

But its an entirely irrelevent situation, when would you find yourself casually drag racing a diesel on the Motorway?

dont know, some days you do, some days u dont i guess...but the question was not WHEN you do this but IF you were to do this. you could replace the word, motorway with drag strip if you so choose.

we are extrapolating hypothetical situation and putting into a real world application. the rhyme and reason for not doing it in real life are not required.

 

[[TW]Fox]

dont know, some days you do, some days u dont i guess...but the question was not WHEN you do this but IF you were to do this. you could replace the word, motorway with drag strip if you so choose.

Yea but if the answer to 'when' is 'never' whats the point?

Petrol is better because the petrol is faster in 5th than a diesel in 5th if the diesel car is towing a horsebox filled with wallabies.

we are extrapolating hypothetical situation and putting into a real world application. the rhyme and reason for not doing it in real life are not required.

They are because if its not something that happens in real life why do we care how capable the diesel is at it?

 

[Dandle]

Lucero... I'm not quite sure what you're trying to argue.

You have a 530d and an E46 330i, and they have equal performance. This is no surprise, as they have similar weights and power outputs, with the extra weight of the 5 is offset by the extra torque. Therefore, this is what one would expect, and supports almost exactly the point I made with the Focus. Same power output diesel and petrol, will almost always have the same performance as the weight the diesel engine brings almost always offsets the torque benefit.

E60 530d - 235 PS - 1655 Kg - 500 Nm - 142 HP/ton, 302 Nm/ton
E46 330i - 231 PS - 1505 Kg - 300 Nm - 153 HP/ton, 199 Nm/ton.

So the car with more than 50% extra torque per ton, barely accelerates any harder?

I cant really comment to much on the above but one thing to consider is that the 530d is torque limited in first and second. Which are the main gears on the drag you are talking about.

 

[The Running Man]

Yea but if the answer to 'when' is 'never' whats the point?

No. your answer is never, that does not mean that everyone has the same answer as you...im sure some ppl in vtecs have raced fabia VRS and such like.. if even 1 person has ever done (which i *may* have) then your entire argument is completely invalidated. so why continue to harrass with this "it never happens" when it could and most probably happens daily. just not for you. once you realise that you will see that your last 3 posts have in effect been meaningless and have not contributed to anything but your postcount.

Petrol is better because the petrol is faster in 5th than a diesel in 5th if the diesel car is towing a horsebox filled with wallabies.

/ of course because that is a realistic situation unlike someone in *shock* a petrol car racing a diesel!?!

 

[[TW]Fox]

No. your answer is never, that does not mean that everyone has the same answer as you...im sure some ppl in vtecs have raced fabia VRS and such like..

/ of course because that is a realistic situation unlike someone in *shock* a petrol car racing a diesel!?!

But we are not talking about actively 'racing' are we - if you are actually going to race the car beside you why on earth wouldn't you pick the right gear first!?

The point being made is that a diesel could 'have' a petrol on the Motorway if nobody changed gear. To which I say when would that ever be a valid situation!? Are we suggesting that sometimes you might accidently find your gear linkage broken just when you need to pwnzor an A4 2.0 TDI?

If you are just 'on a cruise' in 5th in your petrol car you are not racing Skoda Fabia diesels. If you ARE in the mood for racing Skoda fabia diesels, you pick the right gear. Why is this so difficult to comprehend?