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TimK 07-27-2016 05:34 PM

330i Soft top user from England saying hi
Hi all,

Nice site you've got here. I've been reading up on economy techniques on this site, and have gone for a partial grill block on my 2005 330i Convertible. I learned a lot on how to design the grill block on this site, so thanks.

Of course the 330 is never going to be a super economy car, but I just wanted to optimise what I've got, without changing the looks of the car.

So far it gets about 31mpg (US) at 65-75mph on the motorway (highway), but with the massive grilles up front I have made a partial grill block to see if I can reduce the drag and gain an mpg or two.

Will post a thread on the grill block.


mcrews 07-27-2016 06:49 PM

Welcome Tim!!

TimK 07-27-2016 06:50 PM


Originally Posted by mcrews (Post 519442)
Welcome Tim!!

Thanks mcrews!

MetroMPG 07-30-2016 01:06 PM

Welcome to the forum!

Fun car. And the manual transmission gives you lots of options for fuel-saving.

I'm curious if you've compared top up vs. top down MPG at a the same speed, just for fun.

TimK 07-30-2016 01:39 PM

Thanks, yes the manual is very useful and it's a great allround car. Over here 80%+ of cars have a manual still, but this is going down slightly over time as direct shift autos become more popular.

I have not tested the mpg with the roof down yet, I might tyr it sometime. In reality though, having the roof down encourages a more laid back driving style so it does probably save fuel overall. I don't find too much wind in the car with the roof down so the penalty might not be to much for dropping the top.

TimK 07-30-2016 01:50 PM

I did some testing today, on my local 2 way test road, I did testing at 40-55mph. Same tyre pressures as last time, and same brand of fuel.

The results show a calculated gain of 0.5mpg in the testing, however, it was gusty today so that may have showed less gains then there would be in identical weather conditions.

However, I did a 30 mile run on a familiar road cruising at 65mph, and with the occasional moment at 70-ish mph to overtake quickly. The result was 40mpg UK, 33mpg US. There was wind around though so I'll reserve judgement, however the wind direction was across me, so not a tail or headwind.

So the initial results at high speeds look good, I would expect to get 31-32mpg US normally in those conditions, so it's possible I've gained 1.5-2mpg at highway speeds with the partial grill blocks and achieved my goal of 40mpg UK.

There is less wind noise at the front so I think drag is reduced to some degree.

I will see what happens next time I go on a run to see if the mpg contiues to be a couple higher than normal.

TimK 08-03-2016 03:24 PM

Here's a picture of the 330:

Upper grill block:

Lower grill block:

And the grill block thread:

TimK 08-03-2016 03:29 PM

I got a welcome from bendav on this thread, thanks for this. It's disappeared though, so not sure what happened there...

TimK 08-04-2016 02:24 PM

Another welcome, from drew191, thanks! That's disappeared too :confused:

MetroMPG 08-04-2016 04:50 PM

They were both spammers -- they only posted in your thread to camouflage their nefarious intentions. So they got the boot. Friendly spammers though!


That's one handsome car you've got. I agree about the top-down effect on motoring style.

TimK 08-04-2016 04:59 PM

Thanks, well it's nice to get a genuine welcome and friendly comments.

Yes the car does have a lot of appeal for the money, I think the convertible style has aged very well. I paid about $5000 for it, have spent a few thousand making it almost perfect though, the previous owner had skimped a bit. I think the later models have lost a bit of the sweet looks.

It's not a low maintenance car but it's very easy to work on, and none of the common issues on the 330 are very expensive to fix, a couple of hundred max. (except rust, which mine doesn't have).

Since I tweaked the toe setting, it turns in a lot keener too (reduced the toe in on the rear to just a touch, and made the front neutral toe).

I like the look of the Metro, it reminds me of a Suzuki Forsa I once owned, bouoght as a cheap runaround, a proper pocket rocket. It has a 3 cyl turbo engine and felt very rapid, probably about 110bhp but weighed nothing, and always did 35mpg+ whatever I did to it - I was 17 so usually drove slightly enthusiastically. It was a LHD canadian import, the UK spec. for the same car was non turbo and called the Suzuki Swift. A nice link to big up the little Forsa:

SDMCF 08-06-2016 03:52 AM

Nice car.

SWMBO has a similar car, a 2003 325 soft top which she bought new. It has now done 330 000 km. She doesn't hypermile and we don't keep fuel logs for the car but the fuel consumption display seemed quite accurate when I checked it and it is rarely re-set. It shows 8.0 litres per 100 km (say 29 MPG US or 35 MPG UK). On occasions I have tried to do better but my limit seems to be about 7 litres per 100 km (33 MPG US, 50 UK) and that is quite difficult to maintain for a full tank.

I haven't done anything to the car to improve economy. Perhaps I should follow your lead and do a grill block. The car is not used much these days though so any savings would be small.

How often to you use the soft top? My wife says the threshold is 13 Celsius ambient temperature. Above that she wants the top down. Below that, the top is up. For winter use she has a hard top which is just like driving a "normal" car. It is a 2-man job to put on or remove so it goes on at the start of winter and stays on till spring. Basically the hard top goes on and comes off with the winter tyres, give or take a little.

elhigh 08-06-2016 08:30 PM

For those who don't know, SWMBO = She Who Must Be Obeyed. AKA The Warden, Morticia, Fang and Silent Death.

That's a very British idiom for a guy in Finland.

Suzuki Forsa = Geo Metro. Same car.

TimK 08-07-2016 04:04 AM

Haha yes I wondered if you were living in the UK using the phrase SWMBO.

The OBC on these petrol E46s does seem to be very accurate from people who post on the BMW forums. I've not done a proper brim to brim test but on longer trips the consumption on long stints matches the amount needed to fill up. You know on these cars, it is not recommended to fully brim the tank, as it damages the evaporative emissions system with fuel that overflows and soaks into it, it is recommended to fill to the 1st click only, just thought I'd mention it.

Yes the savings from a grill block would probably be quite small for you, it's a cheap mod though and every little helps as they say.

I don't use the soft top enough to be honest, I enjoy driving the car regardless of being a soft top, and when I'm driving on faster roads I prefer the roof up. I have had it down at around 12-13 Celsius ambient, and the heaters did a good job keeping the cold out.

I guess the hard top helps to protect the hood from snow in winter in Finland, it's not quite so necessary in the UK, as we usually get around a week of snow every year. I like the fact you can use an E46 convertible year round in such a cold climate though.

I think the best way to get really decent fuel economy from these would be to use pulse and glide with coasting in neutral for the glide phase. I think late 40's mpg UK would be possible (about 40mpg US) on longer runs at around 60-65mph with this technique. I tried pulse and glide using the cruise control, with the car in gear, at about 60-67mph, but it seemed to slow too quickly on the glide phase with the car in gear, even though the revs were only about 2000rpm (6th gear). I might try this again as it's a really easy technique, set the cruise for say 67mph, press the button to turn cruise off, then at 60mph press the resume cruise button. The acceleration on cruise seems to be about 75% of maximum, so will be in a good BSFC zone for the engine.

Anyhow, enjoy the summer in your 325!

TimK 08-09-2016 03:45 PM


Originally Posted by MetroMPG (Post 519596)
Welcome to the forum!

Fun car. And the manual transmission gives you lots of options for fuel-saving.

I'm curious if you've compared top up vs. top down MPG at a the same speed, just for fun.

I did a top down test with the roof up and roof down today, at 55mph on cruise control, on my usual test route. Average of 3 runs each way, car was driven for about 30mins/15 miles before:

Roof up:
Direction A-B (Slight Downhill) - roof up @ 55mph: 48mpg (UK)
Direction B-A (Slight Uphill) - roof up @ 55mph: 39mpg (UK)
Average: 43.5mpg (UK)

Roof down:
Direction A-B (Slight Downhill) - roof down @ 55mph: 48mpg (UK)
Direction B-A (Slight Uphill) - roof down @ 55mph: 41mpg (UK)
Average: 44.5mpg (UK)

A real surprise, the roof down test seemed to yield a touch more mpg, but probably within the bounds of experimental error. The surprise is that mpg didn't drop off noticeably at all. I wonder if the zone from the windscreen to the flat rear trunk top surface is acting like an aerodynamic tail, with a high pressure zone inside the cabin area, deflecting air over the top and to the trunk, and is actually helping economy slightly. There is certainly not much wind inside the car with the roof down.

I can't say driving everywhere with the roof down would be a great hypermiling technique in the UK, the rain would cause a lot of expense with messing up the car's electrics....

Still an interesting result.

MetroMPG 08-09-2016 03:59 PM

Interesting! Thanks for doing & reporting that.

Not what I would have expected.

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