my 3.5 v8 drives similarly to my 1.9 diesel…but has 165bhp and does 4-15mpg

wowsers – what engine has 3500ml of displacement, yet only eeks 165bhp from it??

Gotta love modern tech – 200bhp from a N/A 2L petrol is easily within reach!

DrP

I put it down to the turbo lag, the engine is gutless until it spools up

We’ve also done this before. Turbo lag all but disappears above a certain engine speed – about 1500rpm in my car. Below about 1200 rpm (where you shouldn’t be driving much anyway) there’s not enough exhaust gas flow to even turn the turbo effectively. A turbo is something you have to know how to work with if you want to drive a certain way – it’s the same for petrol and diesel.

If I am driving normally and gently at low revs there’s only half a second delay before I get all the power I need in any gear. I do not have to shift. However it is different in different engines, which is why I asked what model Mondeo you had.

well, assuming the ECU doesn’t overfuel until the turbo spools up and starts delivering more air)

Some do, to varying extents. That’s why you see a puff of brown smoke when they pull away sometimes. They are trying to get the turbo going as quickly as possible.

To be fair I’d like to drive a Prius to see what they’re like.
What sort of MPG do you get? I’m assuming its free VED too?

Mine’s a MkII so I’m band B £15/year. The new ones are A and much better cars to be honest. Faster, bigger, plusher and more economical.

As a car to drive I find it refreshingly easy. Light steering, the powertrain is always super smooth, you don’t have to make any effort to drive smoothly.

They are quite sensitive to driving style, which is why some people report 45mpg and others get 60mpg easily. All the usual economy tricks like reading ahead etc seem to make more difference in the Prius.

When I was driving to Aldershot, between leaving the M4 and the Wellington Monument via Fleet I could only maintain average mpg in the Passat, but I could get it up by 3 mpg in the Prius.

wowsers – what engine has 3500ml of displacement, yet only eeks 165bhp from it??

I presume that’s the old Rover V8 (as fitted slightly more recently to various Land Rovers). IIRC it only gave 150bhp in the standard SD1.

They are quite sensitive to driving style, which is why some people report 45mpg and others get 60mpg easily. All the usual economy tricks like reading ahead etc seem to make more difference in the Prius.

When you pull off or just drive slowly, do they just use the electric motor or does the electric just assist the petrol?

And what’s the boot like? Could you put a bike in with the front wheel off, for instance? Or is it taken up by batteries?

wowsers – what engine has 3500ml of displacement, yet only eeks 165bhp from it??

Original Rover V8, ok in its day – Ford Granada’s and the like only got 150bhp from their 3.0i and sub 20mpg.

But you could easily get away with a 3-speed gearbox 🙂

If you pull away normally, it’s electric to start with then the engine kicks in depending on how much torque you’ve requested, and how much charge there is in the battery. If you are just creeping forward in traffic, or closing a gap in a traffic light queue or something, you’ll stay electric. You can be in a long queue of several light cycles and use no petrol at all in 5 mins, which is quite nice. Then when you get back into a normal car you think ‘shit why the hell is my engine still runnning, I’m wasting fuel here!’

If you lift off when driving at any speed the engine stops and doesn’t even turn over.. it applies a bit of recharging to simulate the feel of an auto. At this point if you touch the pedal ever so slightly it’ll just freewheel completely, engine off, no braking, and it’ll roll for ages only losing a couple of mph. Great technique for saving fuel 🙂

The boot – on mine, it’s deeper than say a Golf but shallower. Not dissimilar really. With the seats down however it’s pretty big – as long as an estate although not as square. It’ll take bikes in with front wheel off no problem. The boot floor is level with the rear sill. The batteries go underneath that, but only about 12″ deep from the back of the rear seat. There’s a storage compartment under the floor right behind the sill about 8″ deep and 18″ long. If that makes sense. The spare wheel is under that.

The new one is bigger – the boot is I think taller in the back, not sure if it’s slightly longer or not. I say new, they’ve been out since 2009.

If you are just creeping forward in traffic, or closing a gap in a traffic light queue or something, you’ll stay electric. You can be in a long queue of several light cycles and use no petrol at all in 5 mins…

I want this retrofittable to all cars!

DrP

Toyota are giving it a good go, and Ford in the US.

I drove our petrol and diesel yesterday. The petrol will do 7500rpm (2.4L) and is smooth to drive, plus great to drive on local roads. The diesel I use on the motorway and it sits at 1800rpm at ~80pmh, super comfy. Petrol and diesel – pro and cons for each.

‘My OH thinks I am very sad.’

Funny that! Still you’re in good company on this thread! 😉

I don’t know why 7500 rpm is important. It’s the torque delivered at the wheels that’s the important thing, so if you are in a lower gear your engine goes faster.

The Civic 2.2 diesel I drove was just like a turbo petrol. If I’d put a sticker over the rev counter that went 0-8000 instead of 0-5000 and put the stereo on full you would never have known.

I don’t know why 7500 rpm is important

It’s not. But with the right engine it sounds niiiiice. 🙂

The Civic 2.2 diesel I drove was just like a turbo petrol. If I’d put a sticker over the rev counter that went 0-8000 instead of 0-5000 and put the stereo on full you would never have known

This. I went from a turbo petrol (Subaru) to a turbo diesel (BMW 530d) They really aren’t that different, the Scooby pulled hard from 3000-6000rpm, the BMW pulls hard from 1800-4000rpm, so either one could double it’s speed in one big pull without changing gear, the only difference is that the Scooby would be a gear lower to do that at most speeds.

Oh dear!

They got it. its currently in a 1990 discovery that weighs about 2 tonne – and its destined for my 1987 ninety. Nice and torquey Unlike modern revvy petrol engines that bog down once you load em up 🙂 bhp figure isnt everything.

Its not for road use 😉

cruise not economical..

think of a generator or a piece of plant machinery thats used to create electricity or hydraulic pressure they are wherever possible run at a constant load / torque output, the load applied and the torque produced are set to the most fuel efficient operating condition.
On a diesel the amount of fuel burnt = torque produced, as the gradient (hills) or wind changes so the load changes, if you then try and maintain a fixed road speed the amount of torque required to maintain the same speed also changes IE you force the engine into more inefficient operating areas of its cycle..
Drive with the accel pedal and half an eye on the tacho and an ear on the engine note (and avoid loading it) change gear to maintain a moderat engine speed matched to a low loading and you will burn the least amount of fuel on your journey.
Cruise is great for maintaining a set speed but rubbish at economy (esp if on a manual and incapable of making gear shifts automatically as you regulary end up in high load conditions).
same logic with petrol but delivered torque not directly proportional to torque..

hybrids before getting carried away, start looking into the effcy of conversion (ie how much fuel you have to burn to charge a battery to get back in electric use) its not a good equation, unless you drive it like you stole it in non electric form to gain lots of regen braking charge, but who would by a hybrid and then deliberatley drive aggresively to improve economy, most likley buyer will drive conservatively and hence get little regen and burn loads of fuel charging a batt which then gives back less energy than that burned to create it :roll:.
Full plug in better, but you shift the carbon burn somewhere else.
Stop-Start systems, a sales pitch to claim improved MPG when your not actually moving anywhere ?? maybe use the bus / bike on journeys where a stop-start car is worth having as the fact your not moving implies the car is not a good choice in the 1st place.

thisisnotaspoon – Member

My tuppence after having to endure 600miles in a diesel this weekend.

Petrol – floor it and revs x torque = power; simples! If you try and set off from 20mph in 5th of course nothing happens, knock it into 3rd though and shit leaves the shovel.

Diesel, floor it, and the engine thinks about it, makes a whirring sound, anddddddddddddddddddd nothing. Then you drop a few gears, floor it again, it thinks about it, makes a whirring sound and then sets off like an overweight Labrador, then you run into the rev limiter at 4000 and have to repeat the process again.

The saving grace of diesel is it seems to do the same mpg whether you thrash it or cruise. This is a product of slightly more efficient combustion and the above mentioned turbo lag means that airflow is only vaguely correlated to what your right foot is doing, if you built in throttle response that slow into a petrol ECU it’d probably be efficient too.

1) try using the gearstick..
2) diesels run massively lean at all times, their not throttled in the 1st place, turbo lag is a function of lower engine speed / gas velocity. A twin sequential CRD can be made to deliver torque across as wider range as a petrol and more of it (for a given capacity) just takes more cost than somewhat archaic hence cheap petrol engines.

The last diesel I had with glowplugs I replaced them myself, was a doddle. Mind you that was about 12 years ago now as not had any since with glowplugs.

All diesels have glowplugs to allow them to start in extremely cold temperatures (ie well below zero) – but they are still used to improve emissions from a cold start.

You are more likely noticing the fact that the durability is better nowadays as they are better controlled, and the fact that a direct injection diesel can start without glowplugs (but will be a bit more smoky) and therefore haven’t had to replace any

Makes sense Paul I was under the impression they had none but could be they’re need in really cold days, must have to be bloody cold as we had temps of -15c and less a few years ago here and still the VAG started first time every time without waiting. I have noticed when you unlock the car and open the door you can hear it priming so maybe that’s how they do it. Never had to wait on the little orange light coming on and going out like on my old 306.

Learnt something there.

As said by a few others “I like the way diesel’s drive”.

Just out of interest, what apps are people using to record fuel economy??

I use Fuelly.

]

hybrids before getting carried away

You don’t quite understand how hybrids work.

When braking, about 25% of the energy you put in to accelerating the car is stored in the battery as usable charge. It’s a fairly low percentage, but it’s better than dumping it all as heat, isn’t it? My car shows a graph of energy regenerated over time. On a typical country road, driving economically but not especially slowly, I’ll get mabye 200-400Wh of energy back in a half hour period. That’s very roughly enough to light a house for an evening. That’s energy that would’ve been completely wasted in a non-hybrid.

However, most of the regenration comes when cruising. A normal petrol car closes the throttle to keep your speed constant – that is inefficient – pumping losses. The hybrid, when it wants to recharge the battery, opens the throttle a bit more which reduces losses and diverts some of the energy to the battery.

And as for getting carried away – this is not a theoretical system, they are on the roads and they work.

Diesel, floor it, and the engine thinks about it, makes a whirring sound, anddddddddddddddddddd nothing. Then you drop a few gears, floor it again, it thinks about it, makes a whirring sound and then sets off like an overweight Labrador, then you run into the rev limiter at 4000 and have to repeat the process again.

how old was that diesel?

sporty diesels have loads of torque at low revs, that is where they are impressive. thing I don’t like is how they don’t slow down as quick as a petrol – don’t feel as tightly connected to the accel. pedal. Plus the don’t sound quite as good when revved, although the alfa ones sound pretty fair.