Första turbo bilar var byggda för mera effekt och hade stora turbon som bara kom igång vid högre varvtal men senare bilar med s.k. lågtrycksturbo tror jag har lägre förbrukning än motsvarande större motor skulle ha haft. Om man tänker eftermontera en turbo för spara bränsle är det nog en förutsättning är att växellådan tillåter att man kan ta vara ökade vridmomentet av motorn med turbon och att motorvarvtalet kan sänkas. Ibland finns det kanske passande växellåder eller slutväxel från större motorer eller dieselmotorer med större vridmoment / lägre varvtal som man skulle kunna montera samtidigt.
Ett exemepel där eftermontering av en turbo i en bil med variabel utväxling som verkar ha gett bra resultat är i första gen Prius här
http://autospeed.com.au/cms/title_The-S ... ticle.htmlCitat:
So it’s been lots of work and there have been a helluva lot of problems to overcome along the way – but now, finally, what’s the turbo Prius like on the road?
In a word – fantastic.
The turbo NHW10 Prius now has better than standard fuel economy. And performance? Well, the key aim has been realised – country road hill-climbing performance has been completely transformed.
Fuel Economy
On an open road cruise at 100 km/h, the turbo Prius will turn in a best economy of about 4.6 litres/100km [21.7 km/litre, 61.4 miles per imperial gallon, 51.1 miles per US gallon]. In the same conditions, the dead standard car used to get about 6.3 litres/100 km [17 km/litre, 5.9 litres/100km, 48 miles per imperial gallon, 40 miles per US gallon], so the modified car has improved the fuel economy in these conditions by up to 28 per cent!
However, that’s a very best case scenario.
In a mixture of some urban, a fair amount of open road cruising at 110 km/h, and some steep country road hill-climbing (in other words, my most frequent driving mix), the economy now averages 5.5 litres/100 km [18.2 litres/100km, 51.4 miles per imperial gallon, 42.8 US miles per gallon] . In the same driving conditions it used to be 5.7 litres/100 km [17.5 km/litre, 49.6 miles per imperial gallon, 41 miles per US gallon], showing that there’s been an improvement of 3.6 per cent.
It’s hard to make a comparison in heavy traffic urban driving, because economy varies so much with the conditions. However, a best economy of about 4 litres/100 km [25 km/litre, 71 miles per imperial gallon, 59 miles per US gallon] can now be gained in these conditions. I don’t remember previously ever seeing economy that good.
And it needs to be kept in mind that’s all achieved in a car with comfortable seating for four adults (it’s a very roomy cabin for the size of the car), and having dual airbags, climate control, excellent NVH, etc. In other words, it’s not a small, poorly riding economy box with a screaming engine.
Performance
As mentioned earlier in this series, the Achilles Heel of this NHW10 domestic Japanese model is the lack of open-road performance when the high voltage battery is short-term exhausted – as happens after full-throttle has been used a lot. Without the additional electric motor power then being available, the performance is miserable. In fact, up a very steep open-road test hill, the full-throttle performance at the top could drop as low as 47 km/h, and was typically only about 50 km/h. But with the turbocharger, the Prius can consistently top the same hill at 86 km/h – an absolutely incredible 70 per cent improvement in real world open-road performance.
But what about the car’s quarter mile and 0-100 km/h times? Well, while improved, the gain is nothing like as great as the lift in hill-climbing performance. What happens is that the hybrid control system acts in such a way that the peak combined power of the electric motor and the petrol engine is not substantially increased. In other words, total peak power is not much changed over the best it could previously ever be.
Part of the difficulty in describing the performance change is because the Prius Power Split Device varies engine revs according to speed and throttle position. So to reach peak engine power (as measured by the airflow meter signal), the car needs to be travelling at over 100 km/h at full throttle. At anything less than about 100 km/h, full throttle makes use of the typically much improved mid-range power. (It’s improved because there’s always plenty of electric power available.)
That’s why dropping the boost from 7 psi to 5 psi at high loads makes little difference to normal on-road performance – in fact, it’s hard to even tell the change. But drop 3 or 4 psi of boost in the mid-range - and then climb a steep hill - and the engine can immediately be felt revving harder to generate enough power. And after only a short time of this (eg 30 seconds), Myrtle the Turtle will come on indicating that the high voltage battery is down in level... .and then performance is just woeful. With the turbo boosting the mid-range by 7 psi, Myrtle is completely banished.
But there’s no getting away from it – even with the turbo, the petrol engine is still a low powered one. On the freeway at 110 km/h, the level of turbo boost varies from 0-2 psi – the engine is working much harder than you would expect in a conventional car. On extremely steep grades (eg marked at 18 per cent!) the Prius still struggles...although then, so do lots of other low-powered cars.
NVH
Amazingly, noise, vibration, harshness are now improved over standard. This is primarily because with the greater mid-range torque produced by the petrol engine, the ‘gearbox’ keeps engine revs lower for a given power output. So instead of engine revs flaring loudly at each small hill, the car now just torques its way up with engine revs and noise both much lower.
When the front undertray was off the car, some intake noise from the large airbox could be heard, but with the tray back in place, this is inaudible. There may – may – be a slightly deeper exhaust note on the overrun, where the injectors are switched off and the engine is freewheeling, but from inside the car, the new exhaust is otherwise dead quiet.
Outside, the exhaust has a deeper note and the turbo can be very faintly heard whistling-up – those noises overlay the (also faint) whistling/whine of the electric motor and power converter and the normal sounds of the combustion engine. From inside the car, about the only time you can hear any performance is at full throttle at higher speeds, where the engine makes a muted growl.
Conclusion
To achieve modification results on such a complex car that include superior fuel consumption and vastly improved open-road performance are very satisfying results.
The upshot is that the Prius drives exactly like a turbo factory NHW10-model Prius would. There’s no added induction noise, no blow-off valve noise, no exhaust noise. There’s no rush of boost as the turbo spools-up, no change in the sensitivity of the electronic throttle, no increase in vibration or harshness. Instead, the car is punchier in urban cut and thrust, and much more powerful when being driven hard along a sinuous and hilly country road. Drive it everywhere at full throttle and fuel consumption is far poorer than standard, but drive it normally and the fuel consumption is a little better than standard – the consumption depends entirely on the mood of the driver. Having said that, it's rare not to get 750 kilometres out of a single 45-litre tank...
In short, all the criteria for improved open road driving performance without a severe overall fuel economy penalty or poorer NVH have been met.
Första gen Prius fick enligt en annan (Amerikansk) rapport också mera vrid och effekt om man kör den på E85 än på bensin, och motorn går därför med lägre varvtal i samma hastighet än med bensin , tänk om man skulle köra denna turbo Prius på E85 då fick man troligtvis ännu bättre resultat!?
PS Jag förstår inte att de flesta nya bilar fortfarande har kamaxlar och fasta ventilöppningstider. Med elektronisk ventilstyrning skulle man kunna slippa gasspjället och pumpförlusterna helt, reglera egr med avgasventilen, kunna stänga av cylindrar efter behov, rulla ut längre med all ventilar stängda osv.
PS2 en Renault CV2 har nog aldrig funnits, däremot Citroen 2CV och Renault 4CV