High Revs

jamieh · 09-03-2006 5:45pm #1

Hey all,

My mum (and I) drive an 06 1.4 Astra GTC.

I find that its fairly heavy on petrol. I noticed that when you're crusing along at 100kmh in 5th gear the revs are up at 3,000, which seems fairly high, which I'm guessing affects fuel comsumption.

Is there anything that can be done to reduce the high revs?

comanche · 09-03-2006 5:48pm

drive slower

ZENER · 09-03-2006 5:53pm

use lighter petrol

Seriously though. 3000 rpm at 100kph/62mph sounds about right judging by my car - Alfa 147. What mpg are you getting or are you going by the onboard trip computer readout if available.

ZEN

Anan1 · 09-03-2006 6:12pm

If anything, that gearing sounds a little on the high side already. Top gear should give top speed at or very close to maximum power output. I would have thought that most 1.4s would peak at or around 6,000rpm. The figure you've given equates to around 200km/h at 6,000rpm. Would a 1.4 Astra get to that speed?

comanche · 09-03-2006 6:26pm

Anan1 wrote:

If anything, that gearing sounds a little on the high side already. Top gear should give top speed at or very close to maximum power output. I would have thought that most 1.4s would peak at or around 6,000rpm. The figure you've given equates to around 200km/h at 6,000rpm. Would a 1.4 Astra get to that speed?

I'd say not too far off... I've touched 175kmph in a 1.4 megane, was very suprised by it myself and there was still a bit left

Think it would be inpractical to gear 1.4s (or smaller) any lower.. but the revs are about right for a 1.4 (even 1.6 doesn't rev that much lower @ 100kmph)

mike65 · 09-03-2006 6:28pm

Thats about 20 mph per 1000 rpm in top gear (in old money) which is'nt unusual for a 1.4.

Mike.

HungryJoey · 09-03-2006 6:29pm

Sounds right, my mam's 1.4 06 Leon is the same. Cruising at say 110/120 km/h and you would think the engine is understrain.. But you realise its not when you put your foot down... eventually it does get up to around 160KM/h ish... Tops out at about there ( Very noisey ) But yeah... 5th gear at 70MP/h Ain't very smooth.. Engine just sounds strained.

Hj

jamieh · 09-03-2006 6:32pm

Ok lads, thanks for the advice!! I just thought it seemed a little bit on the high side. There's a 6th gear on my dads car and when I'm driving the astra it feels like there should be a 6th!! If I bring it up to 120kmph rev usually go to 3,500, 140kmph revs go up to 4,000.....I'll just have to live with it I guess!!

maidhc · 09-03-2006 6:56pm

A friend has an old shape 1.4 Astra and finds in very heavy on petrol.

Anan1 · 09-03-2006 6:59pm

It could just be that that particular engine is not at its most comfortable at around 3,000rpm.

unkel · 09-03-2006 7:10pm

Anan1 wrote:

Top gear should give top speed at or very close to maximum power output

Yeah would think so too

Anan1 wrote:

I would have thought that most 1.4s would peak at or around 6,000rpm. The figure you've given equates to around 200km/h at 6,000rpm. Would a 1.4 Astra get to that speed?

That's where the calculation is going wrong. The 1.4 has max power of 75bhp @5000rpm and a top speed of 164km/h. Very much in line with OPs reportings of speed and revs taking into account near +10% positive reading of the speedo at higher speeds which is quite normal in that class of a car

Anan1 · 09-03-2006 8:03pm

"That's where the calculation is going wrong. The 1.4 has max power of 75bhp @5000rpm and a top speed of 164km/h. Very much in line with OPs reportings of speed and revs taking into account near +10% positive reading of the speedo at higher speeds which is quite normal in that class of a car"

Ah. That makes sense. Is it a diesel, or is it just not Italian?;)

unkel · 09-03-2006 8:25pm

Anan1 wrote:

Is it a diesel, or is it just not Italian?;)

LOL

Anan1 wrote:

Ah. That makes sense

It would, but I got the figures wrong

Above are for a 1.4 Golf. The 1.4 Astra has 90 BHP @5600rpm, top speed 178km/h. Still 100km/h @3000rpm is about right too

kluivert · 10-03-2006 11:34am

unkel wrote:

LOL

It would, but I got the figures wrong

Above are for a 1.4 Golf. The 1.4 Astra has 90 BHP @5600rpm, top speed 178km/h. Still 100km/h @3000rpm is about right too

I have a 99 Opel Astra and this is spot on. I even checked my car with a new one to make sure my clutch wasnt starting to slip.

About the petrol consumption, i get around 350 miles per week from a full tank. I normal drive at 50 mph and need to in order to get the most out of a full tank.

I find the car doesnt like to be driven around town, drinks petrol. But in saying that, it has good performance, the Golf is 75bhp, why its slighty better when it comes to fuel economy.

Please note that the New Astra is heavier than the new Golf which is heavier than the Corrolla which is heavier than the Civic.

Btw, love the Sportshatch very nice looking car.

comanche · 10-03-2006 11:51am

define heavy on juice?

Getting 40.7 out of 1.4 megane (98bhp) mixed driving. Think thats pretty good especially since I have a heavy foot.

SouperComputer · 10-03-2006 12:15pm

sounds about right to me. Revs dont necessarily use fuel, its revs + throttle opening + fuel\air ratio. The amount of vacuum on the inlet tract is one way of judging it.

I have a 1.4 ibiza and its the same gear ratio as yours, basically 5th is RPM x 2 /100 = MPH (approx)

So 2000 RPM = 40Mph
3000 = 60
4000 = 80
5000 = 100

etc etc

Interesting thing is that the engine produces peak power quite early @ 4700, but will pull well above that in top gear.

My 1.6 passat has the same ratio, but revs higher

el tel · 10-03-2006 12:30pm

Last weekend I was driving a 1.6 Golf and at 60mph the revs were 3000rpm. I was also amazed at how quick the fuel needle went down over the two days. My daily driver is a Passat 1.9TDI and 3000rpm get's me 90mph and even then the car feels like it could do with a 6th gear.

SouperComputer · 10-03-2006 12:39pm

el tel wrote:

Last weekend I was driving a 1.6 Golf and at 60mph the revs were 3000rpm. I was also amazed at how quick the fuel needle went down over the two days. My daily driver is a Passat 1.9TDI and 3000rpm get's me 90mph and even then the car feels like it could do with a 6th gear.

Aye, but the TDI has a LOT more torque.

el tel · 10-03-2006 1:00pm

SouperComputer wrote:

Aye, but the TDI has a LOT more torque.

Of course, but even at that, a 6th gear wouldn't go amiss on it. The next petrol car I get definitely must have a six-speed box as I find the incessant high revving really tiresome on the motorway.

SouperComputer · 10-03-2006 1:22pm

el tel wrote:

Of course, but even at that, a 6th gear wouldn't go amiss on it. The next petrol car I get definitely must have a six-speed box as I find the incessant high revving really tiresome on the motorway.

Yea, it can be annoying alright if you drive on the motorway a lot.

High Revs

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