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Petrol engine very high rev at UK speed limit why? - Theflyingpostman
Another day, I had a party, and I was to wait for a bus it did not turn up, so I had to call my sister to get me home!

Her car is cute Fiat Panda 1.2 8v 2007 which never been in before, but when she cruises the speed at 70mph (she did at 80mph sometimes) I was look at the rev counter it meet at 3,800 rpm for 80mph, I was wonder if she drove for a very long would not do any good to the engine?

I have a diesel which do 2,300rpm at 70mph in fifth gear. I can't believe the rev on petrol, it seems far too much!

Why are they doing that low gear ratio instead of high ratio, it would be save a lot on fuel.
Petrol engine very high rev at UK speed limit why? - brum

Gear ratios are chosen bearing in mind torque v rpm and top speed/max power.

102Nm at 2500 rpm, 60bhp at 5000 rpm, Top speed 96 mph, Aerodynamics brick

Petrol engine very high rev at UK speed limit why? - badbusdriver

Re fuel consumption, what is important is not how much revs it is doing but how far down you are pressing the throttle. Your sister's Panda has 60bhp and 102NM of torque @ 3000rpm, coupled with a tall boxy (i.e, not very aerodynamic) shape. And in the words of Scotty, "Ye canna change the laws of physics"!. In other words, you need a lot of torque at low revs to do what you expect of it (you know, like you get in a turbo diesel).

Petrol engine very high rev at UK speed limit why? - madf

I use 5,000 rpm regularly in my Honda Jazz. It is great for overtaking and clears the engine and spark plugs of deposits. The latter have only done 47k so still another 20k miles until changing them.

Petrol engine very high rev at UK speed limit why? - bathtub tom

My Yaris petrol hits the rev limiter around 6K (80 MPH in 3rd). I try to change up before then, as I've another 3 gears. Reckon it rattles some loose stuff out.

Petrol engine very high rev at UK speed limit why? - Engineer Andy
Another day, I had a party, and I was to wait for a bus it did not turn up, so I had to call my sister to get me home! Her car is cute Fiat Panda 1.2 8v 2007 which never been in before, but when she cruises the speed at 70mph (she did at 80mph sometimes) I was look at the rev counter it meet at 3,800 rpm for 80mph, I was wonder if she drove for a very long would not do any good to the engine? I have a diesel which do 2,300rpm at 70mph in fifth gear. I can't believe the rev on petrol, it seems far too much! Why are they doing that low gear ratio instead of high ratio, it would be save a lot on fuel.

Actually, 3.8k revs at 80mph is quite reasonable - my old (90s) Micra would happily sit at 70 in 5th with 4k revs, if a little bit noisy, whereas my current 15yo Mazda3 1.6 petrol will do the same at about 3.5k revs.

The engine suns just as sweetly as it did when I first bought it back in early 2006, and still gets the same average 40ish mpg. The Micra averaged around 53 - not bad for a car designed nearly 30s years ago!

Petrol engine very high rev at UK speed limit why? - Theflyingpostman
Thanks for all the replies, I have learned something new, thanks.
Petrol engine very high rev at UK speed limit why? - Big John
I have a diesel which do 2,300rpm at 70mph in fifth gear. I can't believe the rev on petrol, it seems far too much!

It depends on the petrol engine/gearbox design. My 2014 Superb 1.4tsi 125ps does just under 2400 rpm at 70mph in sixth gear - about the same as my previous 2003 1.9pd diesel in top gear. The turbo tsi has good torque at lower revs so pulls the overdrive 6th gear surprisingly well. The sixth gear must be a tall overdrive as at 6000rpm you'd be doing about 180mph which obviously the 1.4 can't do (official top speed is 127mph).

Mrs BJ has a 1.2 Panda that is a bit of a screamer at 70mph. Actually I hate it on a motorway as well as high engine revs, wind noise is bad and it's really thrown around by winds especially when passing lorries. Saying that it's a great car around town especially when parking.

Edited by Big John on 29/06/2021 at 19:46

Petrol engine very high rev at UK speed limit why? - barney100

Does driving with high revs on small petrol units wear the engine more quickly? Knew a bloke who ran 2cvs for years and revved them to the limit most of the time and he reckoned they were unburstable... and he didn't burst one either.

Petrol engine very high rev at UK speed limit why? - madf

2200rpm at 70 mph : 2012 Honda Jazz CVT

Petrol engine very high rev at UK speed limit why? - Bromptonaut

It's a 14yo car with, I assume, a fairly basic petrol engine without a turbo or any other add on stuff. Probably one of the FIRE series originally dating to the eighties.

Highish revs were a feature of the time, these engines tended not to pull well at low revs with both power and torque higher up the rev band than today's units. Provided they're smooth running then at the revs quoted I don't think NVH would be too much of an issue neither would engine wear; they're engineered to minute tolerances and provided there are no lubrication issues they'll run for ever.

Normal for it's age I think.

Petrol engine very high rev at UK speed limit why? - dan86

It's a 14yo car with, I assume, a fairly basic petrol engine without a turbo or any other add on stuff. Probably one of the FIRE series originally dating to the eighties.

Highish revs were a feature of the time, these engines tended not to pull well at low revs with both power and torque higher up the rev band than today's units. Provided they're smooth running then at the revs quoted I don't think NVH would be too much of an issue neither would engine wear; they're engineered to minute tolerances and provided there are no lubrication issues they'll run for ever.

Normal for it's age I think.

Those old FIRE engines were brilliant, so simple to work on and bomb proof, I had a 1.1 MK1 Punto and I knew the cambelt needed doing but was just to lazy to change it it snapped at the Yorkshire grey roundabout in Eltham if anyone knows the area, I pushed the car to the side of the road lifted the bonnet removed what was left of the old belt from the engine bay got the replacement out of the boot ligned up the cam and crank shaft and was on my way in under half and hour, what can't modern cars be so simple? All about the emissions and needing to take it to a dealer.

Petrol engine very high rev at UK speed limit why? - PeterRed
Petrol engine very high rev at UK speed limit why? - madf

2200rpm at 70 mph : 2012 Honda Jazz CVT

_______________________________________________________________________.

......until you meet a hill and try to maintain momentum. My 2016 Jazz CVT will easily hit 5000rpm at 70mph.

Edited by PeterRed on 30/06/2021 at 21:02

Petrol engine very high rev at UK speed limit why? - bathtub tom

revved them to the limit most of the time and he reckoned they were unburstable... and he didn't burst one either.

I used to reckon that about my old Kia Pride, until I pushed it too far and the diff pin sheared, resulting in the planet wheel shaft punching a hole in the gearbox casing.

Cost me fifty quid for another gearbox!

Petrol engine very high rev at UK speed limit why? - badbusdriver

revved them to the limit most of the time and he reckoned they were unburstable... and he didn't burst one either.

I used to reckon that about my old Kia Pride, until I pushed it too far and the diff pin sheared, resulting in the planet wheel shaft punching a hole in the gearbox casing.

Cost me fifty quid for another gearbox!

Kia Pride, wow!

Please tell me it had the whitewall tyres?!

Petrol engine very high rev at UK speed limit why? - bathtub tom
Kia Pride, wow!

Please tell me it had the whitewall tyres?!

I think it still had one when I bought it for fifty quid, but strangely the whitewall was on the inside.