What RPM at 70mph?

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Desperado
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What RPM at 70mph?

Post by Desperado » Sun 24 Aug, 2014 20:40

Hi,

I owned a 1.9 Z3 7 years ago and circumstances forced me to sell her and go for more practice cars, however, times have changed and I've not lost my love for them. My current car for my daily commute is a BMW 330ci E46 which is great but not what I really want. I've been looking at Z3's again and have come to the conclusion I want a 2.8l based on power/weight and availability.
I do 200 miles a day and it's mostly driving on fast single lane A roads and then motorways, I want a bigger engine to offer smoother and quieter performance when on the motorway. I also would prefer an automatic given I drive around London a fair bit.

That's the background but my question is, at 70mph on a motorway, how many RPM does a 2.8l sit at? As I said I'm looking for information about an auto specifically so if anyone has one I'd be interested to know. If anyone has taken their Z3 to Germany, how many RPM does it do at 80mph (out of interest).

I'm going to be starting my search properly during the winter months to maximise availability/cost and I've got a few very specific requirements, I'm in no hurry so I can play the long game.

For anyone that is interested, I fully intend to get an LPG conversion done as I've done with my current BMW, it's brilliant as I recoup the cost of conversion within 7 months, thereafter I'm just saving money.

Any info about RPM's would be greatly received.
Thanks
Ed

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Southernboy
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Re: What RPM at 70mph?

Post by Southernboy » Sun 24 Aug, 2014 20:47

If you already have a BMW six cylinder, then it will be doing about the same RPM...ie. it should be just under 3000 rpm at 70mph.... accurately probably 2850 rpm would be closer... :wink:
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Re: What RPM at 70mph?

Post by Desperado » Sun 24 Aug, 2014 20:50

I've got a 3l M54 engine, with the 5 speed ZF gearbox - I'd have thought that with 200cc less it would make a little difference - there s 150kg weight difference to consider also.
I'd have though tit was much the same but really wanted some real world confirmation.

Thanks

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Southernboy
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Re: What RPM at 70mph?

Post by Southernboy » Sun 24 Aug, 2014 20:58

Both my 3.0 M54 motor and my previous 2.8 Z3 are identical RPM (3000) at 120kph - which is a tad over 70mph. (70 mph = 112.65 kph)... so that should tell you that it makes no difference being 200cc smaller and a few kg weight difference... the gearboxes are what counts... you have more torque with a larger engine capacity and the same gearbox, but the rpm remains the same.
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Desperado
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Re: What RPM at 70mph?

Post by Desperado » Sun 24 Aug, 2014 21:12

Perfect, thank you.
Out of interest, with a 2.8l do you get any better MPG than a 3.0l, I assume it around 26-27mpg on average with mostly motorway driving?

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Southernboy
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Re: What RPM at 70mph?

Post by Southernboy » Sun 24 Aug, 2014 21:26

My 2.8 was a 97 model, my 3.0 is a 2001 model... single vs double vanos technology... the 3.0 is more economical and considerably more powerful... I can't quote you the mpg consumption though.... it's something that has never concerned me... :wink:
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c_w
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Re: What RPM at 70mph?

Post by c_w » Sun 24 Aug, 2014 22:25

The dual vanos 2.8 is pretty economical. I think the gearbox for all 6cyl cars is the same 2.0-3.2, just the differential ratio varies.

deni2s
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Re: What RPM at 70mph?

Post by deni2s » Sun 24 Aug, 2014 22:57

I have 1997 single vanos 2.8 and on average it is never less than 23.5 mpg (or 10l/100km). It's 50% city traffic, 50% outside city, no matter how hard I drive. I tend to think that is not bad for 2.8 displacement.

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lightning
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Re: What RPM at 70mph?

Post by lightning » Mon 25 Aug, 2014 11:45

I was going to say, why not look at the 3.0 as well as the 2.8.

There seem to be a fair few 3.0 automatics for sale at any given time.

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Re: What RPM at 70mph?

Post by Desperado » Mon 25 Aug, 2014 12:16

I'll be sure to look out for the 3.0 engine Z3's, I kind of discounted them due to the number available but as I'm in no real hurry I will certainly entertain the idea.

amancuso
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Re: What RPM at 70mph?

Post by amancuso » Tue 26 Aug, 2014 17:58

I have the 2.5L engine with a 4spd automatic. At 70 MPH RPMs are at 2850. at 80 MPH they are nearer 3400 RPMs.
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Southernboy
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Re: What RPM at 70mph?

Post by Southernboy » Wed 27 Aug, 2014 07:16

That seems to confirm my assessment...at 70mph most cars are turning around 2850'ish...seems to be the "norm" with most brands.
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OXO
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Re: What RPM at 70mph?

Post by OXO » Wed 27 Aug, 2014 09:29

My 2.2i does 4000 RPM at 70 mph.

It has the short final drive fitted. :D and it's absolutely epic round the twisty road and in town.

This was a factory build option:-

S204A Kürzere HAG-Übersetzung Shorter final drive ratio

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Southernboy
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Re: What RPM at 70mph?

Post by Southernboy » Wed 27 Aug, 2014 13:24

Is that like a "sport" mode set-up Must be a bit heavier on consumption running those revs ? It must have a different diff gearing to achieve the higher rpm ?
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OXO
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Re: What RPM at 70mph?

Post by OXO » Wed 27 Aug, 2014 14:24

It's a bit worse, but not hugely so.

Of course the effect is that all the gears are closer together, so there's a bit more cog-swapping than you'd normally do.

deni2s
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Re: What RPM at 70mph?

Post by deni2s » Wed 27 Aug, 2014 15:09

OXO wrote:It's a bit worse, but not hugely so.

Of course the effect is that all the gears are closer together, so there's a bit more cog-swapping than you'd normally do.
On my 2.8 I sometimes skip a few gears (like 1-3-5). Maybe you can use only two gears :D

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Re: What RPM at 70mph?

Post by Desperado » Thu 28 Aug, 2014 20:06

Thanks for all the posts chaps, very much appreciated. I'm going to start searching for the right Zed in earnest around Christmas. just a little matter of a house to buy first. Mrs J claims it's more important, although we disagree.

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Davejue1
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Re: What RPM at 70mph?

Post by Davejue1 » Fri 29 Aug, 2014 07:55

I have a 2.8 manual and get 27-28mph but do drive it like a jessy! Just one thing, if your doing that sort of mileage I'd strongly reccomend getting one with sports seats rather than standard, there much better cut and it's the one thing I'd wish mine had got. I'm crippled with back pain after 100 miles. :)

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akirk
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Re: What RPM at 70mph?

Post by akirk » Sat 30 Aug, 2014 09:23

I have an auto 3.0 2001 - not sure about revs but will differ between sports mide (gear stick over to the left) and normal...
Mpg i would expect at least 28-30 on a motorway run - speed irrelevant and you can get above 30...

At other times between 24-27 average depending how you drive it, but def. possible to get it below 20!

Alasdair

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Re: What RPM at 70mph?

Post by Desperado » Sat 30 Aug, 2014 09:25

Great, thank you.
My 330 got a whopping 20.1mpg yesterday on a 45 minute drive to Bristol. half local roads, half M4.

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What RPM at 70mph?

Post by Dino D » Sat 30 Aug, 2014 09:59

Hi Desparado,
I converted my 330i manual back in 2006, it was one if the first in UK. Used a good fitter with a Prins system.
Used it for about 20k miles and was great. Only regret was fitting a 45l tank. I'd get 150-190 maybe 200 miles tops between fills!
I used to around 500 - 1000 miles a week then so spent much time at the 'gas' pump but worth the compromise to run. A 330i for 320d money!!
I used to drive it accordingly so average mpg was 20mpg combined. No hypermiling for me, why use 5th to pass when 3rd would do was my motto (well when paying 39p for gas back then why not!).

I now have a Z3 (albeit quite improved for sportier driving to really release the roadster character I wanted for a fun car) and will say that on days when I do use the car for long trips I do miss my my 330 dearly.

Even in a standard one 200 miles a day everyday in a Z3 might be very tiresome, especially in wet winter days after a days work.
The low driving position mean headlights in your eyes from the front and from the rear view mirrors.
They don't have auto dimming mirrors like the e46..and perfectly aligned for 'normal' cars to shine right into them and then reflect in your eyes!

They are more nervous on the road and want more attention on the wheel especially if making progress compared with an e46. If you e46 is a sport model then you will be used to it already.

Definitely more noisy inside (it's good when on a blast but tiresome after a while if you driving for work).
If you like making calls on the go then a very good Bluetooth will be needed to cancel the noise inside.

Space to hang your jacket, shirts, ties etc is missing!

Space to put the seat back down and nod off when waiting for another motorway closure to end is also missing!

Decent cup holders are missing (and space to eat lunch/dinner) but Southerboy on here can sort you cup holders and armrest. You'll need his elbow pads too for your right arm.

M Z is louder and firmer than standard but even the standard ones I find are much less 'refined' than an e46 (which conversely I found too smooth on weekend blasts).
It's the unrefined character that makes the z fun for the weekend and vice versa for the e46.
If I still had the e46 I think I would have fitted a Remus switchable backbox to give a louder note on weekends and quite note when working.
Would have also fitted an LSD from quaife. (It was a apart the suspension was already firm but could have been improved for sure too).

My 2p is given the low price of these cars is to keep the e46 (especially for winter driving, longer trips) and get a well priced 2.8 and see how you get on before converting it or selling the e46.

Trying to get one car to do it well on a budget is tough. My ideal would be an e46 M3 cabriolet on lpg as would do it all for me, might still get one one day as may move from having a weekend and weekday car to just one car..

Is your 330 on gas already?

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Re: What RPM at 70mph?

Post by Desperado » Sat 30 Aug, 2014 10:23

That's a great summing up. In reply.
I converted my 330ci to Gas last January and already recouped my costs, I went for a BRC conversion.

I had a Z3 about 9 years ago, albeit a 1.9. I'm all too aware of the limitations on space and low driving position, however, when I sold my Z3, I left a bit of my heart with it and have wanted to return.

I did some extra long journeys in the Z3, drove it from the Isle of Wight to Scotland in one sitting once, that was a long day but run. I had 17" rims on my Zed and the tram-lining was a little irritating but I can live with that. I've considered all sorts of cars, from an E46 cab to a lotus Elise but I keep coming back to the Zed due to the retro styling.

I'm happy to work on my cars and I find INPA saves a load on diagnostics at garages so I'm up for a foolish (perhaps) challenge.

Regarding your LPG conversion, I take it you had a doughnut tank, I've seen cylinder tanks in pictures but not sure on the size that can be achieved. I'd certainly want as big a tank as I could manage, the battery access though is the biggest concern. I'd be happy to fill the whole boot if possible.

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c_w
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Re: What RPM at 70mph?

Post by c_w » Sat 30 Aug, 2014 19:52

OXO wrote:My 2.2i does 4000 RPM at 70 mph.

It has the short final drive fitted. :D and it's absolutely epic round the twisty road and in town.

This was a factory build option:-

S204A Kürzere HAG-Übersetzung Shorter final drive ratio
Do you know which ratio that is? I'm sure the 2.2s came with 3.38 ratio as standard which gives 70@about 3300rpm.

littlefeller
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Re: What RPM at 70mph?

Post by littlefeller » Sun 31 Aug, 2014 08:06

70 for me is about 3250rpm :o why is mine different :evil:

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OXO
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Re: What RPM at 70mph?

Post by OXO » Sun 31 Aug, 2014 18:14

c_w wrote:
OXO wrote:My 2.2i does 4000 RPM at 70 mph.

It has the short final drive fitted. :D and it's absolutely epic round the twisty road and in town.

This was a factory build option:-

S204A Kürzere HAG-Übersetzung Shorter final drive ratio
Do you know which ratio that is? I'm sure the 2.2s came with 3.38 ratio as standard which gives 70@about 3300rpm.
No idea, but you could calculate it with a factor of 4000/3300

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akirk
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Re: What RPM at 70mph?

Post by akirk » Mon 01 Sep, 2014 08:24

Right, checked it out...

2001 3.0l auto

70mph is c. 2100 - 2200 revs, exact amount slightly depending on how you read the rev counter...

That is in full auto = 5th gear
Push across to sports mode and you get 4th gear = 3,000 revs
Tap back up into 5th and you are back to c. 2,100 revs

Seems to be considerably less than others are suggesting...

80mph in germany / on a private road would be c. 2,500 from memory...

Alasdair

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