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BHP or Torque? Which is more important?


Flatcoat888
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BHP is key.

 

But as stated above BHP is torque x rpm.

 

So how much BHP you have at any point in the rev range is determined by the level of torque at that rpm point. 

 

But we also have to factor in gearing. Gearing determines the actual torque at the road wheels.

 

Best example I have is two Mk3 Mondeo's I used to tow with.

 

One a 2.0TDCi had 130PS  and 236ftlb @ 1750 rpm. The other a 3.0V6 with 204PS and 193lbft @4900rpm.

 

Gearing for the diesel in 6th 38mph/1000rpm and for the petrol 27mph/1000rpm

 

I can tell you the petrol was by far the better towcar, significantly more performance in every situation, far easier to get off the line and 6th perfectly usable where the diesel could only use 5th.

 

Obviously the diesel was better for economy but in every other area the petrol was a better towcar.

Edited by logiclee

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My other half asked this question once and the only way I could describe it was, bhp are race horses and torque are shire horses. Stick a turbo on a racehorse you get best of both worlds... She never asked again. 

 

I had a kia sportage 2 wheel drive with the petrol 180hp turbo and changed to the 180hp diesel 48v earlier this year. The diesel is easier to drive, less gear changes and being heavy makes it more stable. 

 

Diesel had bad press these days but it works for me. 

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In a real world, in my real budget I'd take diesel torque every day. Big fat wedge of torque from low down and broad spread. 

There is other factors, some of which have been made already. Quantity of forward gears, the gear ratios, ability to put down the power, short stroke/long stroke engine, flywheel weight etc.

 

Also personal choice too. 

 

I imagine a large capacity V8 is a wonderful device to tow with. I suspect something like a G63 is absolutely incredible tow car. 

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I have owned over 30 diesels since 1987 of many different makes and types probably covering 500,000 miles.  However I can also honestly say the Tucson petrol Hybrid i drove today is a pretty quick car and drove up the hills very impressively 

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I guess the passion for the diesel is a relict of the past. Really, the only justification nowadays for a modern diesel over a modern petrol is economy.

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8 minutes ago, Lutz said:

Really, the only justification nowadays for a modern diesel over a modern petrol is economy.

 

And intimately linked to that, the carbon footprint, a massive justification for our planet of the diesel over the petrol ICE.

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We all have to accept that diesels days are all but done in the UK.

 

Sales are expected to drop below 10% of new car sales by the end of this year, from the small to mid sized market diesel sales have just about disappeared.

 

Many manufacturers have dropped diesel already and more plan to before Euro7.

 

By 2030 any diesel will need to be hybrid and take up of diesel hybrid has been painfully slow and by 2035 would be dead anyway.

 

There's just not the market now for manufacturers to invest in diesel development.  Even the big diesel players like VAG have pulled the plug on diesel development. The EA288 units that are available now in most models will be the last.

 

Fortunately the turbo petrols and the hybrids are getting better and better and are a real alternative until we have a good enough infrastructure for EV.

 

2 hours ago, JTQ said:

 

And intimately linked to that, the carbon footprint, a massive justification for our planet of the diesel over the petrol ICE.

 

But although manufacturers have seen a massive swing from diesel to petrol/hybrid/EV they are still meeting their CO2 reduction targets.

Some of that will be down to the hybrid/EV models being sold more but also the market trend is for buyers to switch from 2.0/1.6TDi's to 1.5/1.0TSi's with the most common power ranges.

Yes not tow car relevant but that is the reality in todays market.

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11 hours ago, logiclee said:

 

Yes not tow car relevant but that is the reality in todays market.

 

And the market for vehicles capable of towing is a minuscule percentage of sales, so there is zero incentive for manufacturers to firstly develop “tow cars” and secondly to specifically produce them. The age of the touring caravan is coming to an end. I don’t think I will be buying another new one. 

Experience is something you acquire after you have an urgent need for it.

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1 minute ago, Mr Plodd said:

 

And the market for vehicles capable of towing is a minuscule percentage of sales, so there is zero incentive for manufacturers to firstly develop “tow cars” and secondly to specifically produce them. The age of the touring caravan is coming to an end. I don’t think I will be buying another new one. 

 

Agree, 

 

I usually swap caravans every five years or so but we've had this one over eight years.

 

I'll take early retirement in 2024 and considering a lakeside lodge. I've been caravaning since 1987, bought my first caravan at 18 years old. 

 

I just can't see caravanning in it's current state with large heavy caravans be taken to remote locations being compatible with EV. At least in the infancy of EV.

Yeti 2.0TDi EU6 150 DSG 4X4 L&K, Octavia TSi Manual, Fabia TSi DSG, Swift Challenger.

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Maybe the French are more in tune with the way things are going?

 

Every French campsite I have visited in the past 5-10 years has been busily investing in “Cabines” and reducing the number of touring pitches. Cabines of course increase the length of the ‘camping” season in addition to them being somewhat future proof.

 

Many of the “Flowers Camping”  sites have Cabines available out of the main season for €200 per week which, if you add up the cost of taking a caravan on a ferry, the additional fuel costs, the cost of a car capable of towing rather than a smaller car, site fees, the capital cost of a caravan, caravan insurance and, if necessary caravan storage fees.  Then using one if those Cabines for a holiday starts to look like pretty good value. All of the advantages and none of the disadvantages, of a caravan ! 

Edited by Mr Plodd

Experience is something you acquire after you have an urgent need for it.

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22 minutes ago, Mr Plodd said:

Maybe the French are more in tune with the way things are going?

 

Every French campsite I have visited in the past 5-10 years has been busily investing in “Cabines” and reducing the number of touring pitches. Cabines of course increase the length of the ‘camping” season in addition to them being somewhat future proof.

 

Many of the “Flowers Camping”  sites have Cabines available out of the main season for €200 per week which, if you add up the cost of taking a caravan on a ferry, the additional fuel costs, the cost of a car capable of towing rather than a smaller car, site fees, the capital cost of a caravan, caravan insurance and, if necessary caravan storage fees.  Then using one if those Cabines for a holiday starts to look like pretty good value. All of the advantages and none of the disadvantages, of a caravan ! 

 

I think there was a shift in the UK.

 

Three sites that we used to visit around Lincolnshire have switched from touring to fixed.  We've seen an increase in touring the last year due to Covid and staycations but the next few years will be interesting if foreign travel picks back up.

Yeti 2.0TDi EU6 150 DSG 4X4 L&K, Octavia TSi Manual, Fabia TSi DSG, Swift Challenger.

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2 hours ago, Mr Plodd said:

 

And the market for vehicles capable of towing is a minuscule percentage of sales, so there is zero incentive for manufacturers to firstly develop “tow cars” and secondly to specifically produce them. The age of the touring caravan is coming to an end. I don’t think I will be buying another new one. 

Got to agree with that, saw the writing on the wall when we bought our van 2 years ago thats one of the reasons that we got an older one, 9 grand is enough to lose we thought if it all goes belly up.

In my opinion all this emissions, carbon footprint, electric and hybrid stuff is all just lip service and a money spinner!

Big companies are interested in making money and governments are interested in votes. Just good old human nature.

After all nothing is created from nothing, where do we suppose all the power comes from to produce and run these vehicles. Is it just plucked from the ether?

The world is on an eco downward spiral but (again only my humble opinion) this is down to one thing alone

There are just too many of us

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3 minutes ago, robertB said:

 

The world is on an eco downward spiral but (again only my humble opinion) this is down to one thing alone

There are just too many of us

 

And nature is doing it’s very best to limit/control/decrease the number of humans on the planet, aids/Ebola/SARS/Covid  etc etc BUT modern medical science is able to defeat such illnesses these days before they have any appreciable effect. Look at the plague and how that reduced the population because there was no clever medical treatment/cure) Being totally brutal the planet needs another plague to reduce the number of humans infesting it! 

 

I often wonder what the world will be like when my grandchildren reach my age in 40-50 years time. I am none to sure I want to be around then (I’m currently only 67)  Fossil fuels? Gone! Global warming/climate change? A real issue by then! Food? Well climate change is going to influence that, and most important of all?? Access to fresh drinkable water. I have little doubt that water, and access to it, is going to result in serious conflict at some stage. And who is likely to win such a conflict?? China!!

 

To quote Bob Dylan “The times they are a-changing” and certainly not for the better. 

 

After all of that I now feel so miserable I simply have to have a glass (or two) of wine. 

Experience is something you acquire after you have an urgent need for it.

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I think you two have indeed been listening to and watching Iron Maiden's new track/video.   :blink:

 

 

Yeti 2.0TDi EU6 150 DSG 4X4 L&K, Octavia TSi Manual, Fabia TSi DSG, Swift Challenger.

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BHP gets you off the line, torque gets you up the hill.

 

 

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16 minutes ago, Whomer said:

BHP gets you off the line, torque gets you up the hill.

 

 

 

 

Ah but......

 

200Nm@2000rpm  vs 100Nm at 4000rpm.

 

Chose a gear where you are sat a maximum torque.

 

Result = Same performance up that hill because the BHP would be the same. Same torque at the wheels.

Yeti 2.0TDi EU6 150 DSG 4X4 L&K, Octavia TSi Manual, Fabia TSi DSG, Swift Challenger.

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1 hour ago, logiclee said:

 

 

Ah but......

 

200Nm@2000rpm  vs 100Nm at 4000rpm.

 

Chose a gear where you are sat a maximum torque.

 

Result = Same performance up that hill because the BHP would be the same. Same torque at the wheels.


 

ah, but if you bog or get balked at 4,000rpm and drop to 3,800rpm, you drop right off  the torque cliff and hilarity does not ensue.


My petrol CRV is fine towing as long as I keep the revs over 4,200, but under that, it dies under load. Now the Diesel CRV with a pretty much flat 350Nm torque  curve above 1,200rpm, now that’s a different matter.

 

 

Edited by Whomer
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I fir one would much rather have my (Diesel) engine running at 1000 - 2000 rpm than having to keep it revving at over 4K ! Quieter, better fuel economy, less stress on engine components, less gear changing (well the last is not a bother if you have a “proper” tow car that has a decent modern TC equipped automatic, rather than prehistoric manual, gearbox). 

 

Incoming!!!!!!! 

Experience is something you acquire after you have an urgent need for it.

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57 minutes ago, Whomer said:


 

ah, but if you bog or get balked at 4,000rpm and drop to 3,800rpm, you drop right off  the torque cliff and hilarity does not ensue.


My petrol CRV is fine towing as long as I keep the revs over 4,200, but under that, it dies under load. Now the Diesel CRV with a pretty much flat 350Nm torque  curve above 1,200rpm, now that’s a different matter.

 

 

 

And now you are comparing forced induction against normally aspirated.

 

The argument could equally be applied to the 200Nm @2000rpm engine dropping off boost as it would equally slow down on that hill as it's developing the same power as the 100Nm @4000rpm engine and has no more torque at the wheels.

 

And the newer 1.6D CRV at 1200rpm has nowhere near peak torque, only just above half.

image.png.5254bda55f3604255b01008bae295c6c.png

 

 

It's only a bit of fun and examples 

 

BHP will always win,  How much BHP you have at any given rpm is determined by the the torque.

 

How much of that reaches the road wheels is determined by the gearing.

 

Having a long flat torque curve is something turbo petrols are good at and the increased rev range gives access to more power and the shorter gearing provides more torque to the road wheels in any given gear. From a performance perspective power is king. Starting off and going up hills.

 

Lets have a look at two 2.0 BMW's both 4 cylinder turbos. One petrol one diesel

 

The green is diesel and blue is petrol.

 

image.png.01bfc457fbee0af49368b2846f087d71.png

 

Engine output wise the diesel has more torque and hence more power up to 3250rpm. After 3250rpm  the petrol has a massive performance advantage.

 

But that engine gap at lower rpm isn't as wide as it looks as the petrol has 25% shorter gearing. In each gear it's actually sending more torque to the wheels than the diesel even when the diesel is at it's peak.

 

I actually own a diesel as it suits my needs but can equally see that engine peak output torque at xrpm is not the be all and end all of towing performance and that most people ignore gearing.

Edited by logiclee

Yeti 2.0TDi EU6 150 DSG 4X4 L&K, Octavia TSi Manual, Fabia TSi DSG, Swift Challenger.

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13 minutes ago, Mr Plodd said:

I fir one would much rather have my (Diesel) engine running at 1000 - 2000 rpm than having to keep it revving at over 4K ! Quieter, better fuel economy, less stress on engine components, less gear changing (well the last is not a bother if you have a “proper” tow car that has a decent modern TC equipped automatic, rather than prehistoric manual, gearbox). 

 

Incoming!!!!!!! 

 

OK Devil's advocate.

 

But at 1500-2000rpm the only reason the diesel producing peak torque is it's on full boost.  Maybe 20psi of boost on some units and 2000 bar on the fuel rail.

Intake temps are rocketing and the turbo revving at 120k rpm is starting to glow.  The Oil is now being severally tested.

 

Maybe it's better to change down, multiply torque using the gearbox and have less torque demand on the engine. :D

 

 

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Light throttle, engine in the middle of its rev range. Job done!

Experience is something you acquire after you have an urgent need for it.

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1 minute ago, Mr Plodd said:

Light throttle, engine in the middle of its rev range. Job done!

 

Indeed,

 

And if you went for a high torque demand the auto box would choose a lower gear.

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To expand this slightly the rule of thumb for towing is a minimum of 40 horses/tonne. I am never entirely sure if that refers to actual train weight or MTPLM plus Kerb weight. However is torque/weight ratio now a better measure? 

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On 01/08/2021 at 08:33, Mr Plodd said:

 

And the market for vehicles capable of towing is a minuscule percentage of sales, so there is zero incentive for manufacturers to firstly develop “tow cars” and secondly to specifically produce them. The age of the touring caravan is coming to an end. I don’t think I will be buying another new one. 


that's the truth. 
sales if motorcaravans now outdo caravan by 2:1, and it’s increasing.

the inability  of e-cars to tow much more than a garden rubbish trailer  is the final nail in the conventional caravans coffin.

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12 minutes ago, Flatcoat888 said:

To expand this slightly the rule of thumb for towing is a minimum of 40 horses/tonne. I am never entirely sure if that refers to actual train weight or MTPLM plus Kerb weight. However is torque/weight ratio now a better measure? 

 

I think the very old 40hp recommendation dates back decades from the caravan club and was your total outfit weight loaded on the road.

 

 

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