I've had the same thoughts about my Z4. I've recently sold a Westfield which was stupidly quick stupidly impractical. My first thoughts on the Z4 were that it's a slow car. I think you've got to accept like has been said on here, that it's more of a tourer than a straight-line speed demon. Once you get that into your head, you can enjoy it for what it is. I'm loving mine now and only occasionally miss the raw power of the Westfield.
3.0 feels slow...
- Thread starter T2FFN
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2.5 owner here. Have to agree with what's been said about the engine "feeling" slower in a straight line than a turbo. I used to have a 1.8 golf GTI only 150 BHP but felt similar to the near 200 BHP z4. I've recently driven the new audi a3 convertable (sline) 200 bhp turbo engine and it felt significatly faster whilst the actual 0-60 of 7.5 seconds on the audi is less than the 7.0 seconds quoted for the bmw.
Very strange but I think its true - the turbo engine just delivers the power differently giving a sensation of very fast acceleration.
Fast A roads is where the z and its straight 6 really shines. Cruising in 5th and occasionally dropping down to 4th before a corner or a 3rd for overtaking makes the engine work how its supposed to.
Very strange but I think its true - the turbo engine just delivers the power differently giving a sensation of very fast acceleration.
Fast A roads is where the z and its straight 6 really shines. Cruising in 5th and occasionally dropping down to 4th before a corner or a 3rd for overtaking makes the engine work how its supposed to.
Its essentially turbo lag - what you 'feel' is the torque of a car (or the gradient of the BHP line). Turbo cars rapidly gather torque and then loose it, therefore you get the pushed-back sensation... A good little comparison of 2 comparable cars:
A Stg1 1.8T 180bhp (Seat Ibiza FR/Cupra @224bhp) and a Slightly fettled K20A2 (Civic Type R):
http://www.dyno-plot.co.uk/dyno/dynoplot/id%3D456_323%26sort%3Dveh%26but_sea%3Dqs%26sea_simple%3DK20A2/index.htm
If you super impose those power lines, the K20A2 actually has more power for longer (area underneath the graph), but not necessarily in its power-band (lets say the last 2500rpm).
In summary, to get the sensation back - use the gearbox more
A Stg1 1.8T 180bhp (Seat Ibiza FR/Cupra @224bhp) and a Slightly fettled K20A2 (Civic Type R):
http://www.dyno-plot.co.uk/dyno/dynoplot/id%3D456_323%26sort%3Dveh%26but_sea%3Dqs%26sea_simple%3DK20A2/index.htm
If you super impose those power lines, the K20A2 actually has more power for longer (area underneath the graph), but not necessarily in its power-band (lets say the last 2500rpm).
In summary, to get the sensation back - use the gearbox more
Yep, turbo gives you the large rate of change of accelerative g independent of your demand.
Ie, 3.0i BMW pushes you back instantly on the throttle, and is quite a flat output over the rpm range.
1.8T 265bhp, pushes you back half as much at first, then over maybe the next second you get the push, which makes it much more noticeable!
The Z4 feels much faster from the passenger seat when driven hard for this reason, you don't know what the throttle position/demand is
I'd not bother with a remap. Sports cats and/or full Milltek system or similar is the way to liberate another 10bhp, more noise, and a feeling of more freedom in the revving from what I have read/seen.
£1000 though! Superchargers start to look more appealing
Dave
Ie, 3.0i BMW pushes you back instantly on the throttle, and is quite a flat output over the rpm range.
1.8T 265bhp, pushes you back half as much at first, then over maybe the next second you get the push, which makes it much more noticeable!
The Z4 feels much faster from the passenger seat when driven hard for this reason, you don't know what the throttle position/demand is
I'd not bother with a remap. Sports cats and/or full Milltek system or similar is the way to liberate another 10bhp, more noise, and a feeling of more freedom in the revving from what I have read/seen.
£1000 though! Superchargers start to look more appealing
Dave
Much of the difference in felt acceleration between similar sports cars is a result of the drivetrain gearing. The Z4 3.0i and Z4M have, for example, almost identical (vehicle weight adjusted) torque curves from 1500rpm to 4000rpm, yet the Z4M applies that engine torque at much higher wheel torque thanks to it's differential gear ratio. A very effective performance modification is simply changing the differential carrier gears (usually a simple differential swap). It's easy, 100% predictable, and requires no engine modifications whatsoever. In fact, with aggressive gearing the increase in wheel torque can match the performance gain from a stage I twin screw supercharger in the aforementioned engine speed range at less than 1/5 of the outlay. Cams are more expensive and can hurt low rpm performance whilst providing most of their real gains at near-maximum engine speeds. Intake and exhaust modifications also provide their gains (if any :wink: ) at higher engine speeds. IMO: The engine breathing modifications such as cams, intake and exhaust, offer expensive and mostly track-justified performance improvements. Forced induction offers broader gains, but is at it's best at highway speeds. Drivetrain gears, tires and suspension improve daily driving performance the most.
Hi T2FFN,
What you may be feeling is the computer adapting to the primary use that the car has had. If the previous owner drove the car gently, the computer remaps the throttle for more gentle driving. To reset to factory defaults turn the key on for 10 seconds (don't start), then off for 10 seconds, then on again for 10 seconds (don't start), then start the car. You'll likely find that the throttle response is a little more "urgent" (more response from less input - but no more power at full throttle)
Hope this gives you what you need without any expense.
Bill
What you may be feeling is the computer adapting to the primary use that the car has had. If the previous owner drove the car gently, the computer remaps the throttle for more gentle driving. To reset to factory defaults turn the key on for 10 seconds (don't start), then off for 10 seconds, then on again for 10 seconds (don't start), then start the car. You'll likely find that the throttle response is a little more "urgent" (more response from less input - but no more power at full throttle)
Hope this gives you what you need without any expense.
Bill
T2FFN said:
Totally agree.bimster said:
The 3.0 is pretty tall geared IMHO, so not exactly cheap but most effective would be to swap the diff from from the 2.5Si auto at 3.73 instead of the standard 3.07 in the 3.0, which would give much more acceleration over other tuning methods, apart from the supercharger.
Changing final drive ratios in the diff is of course a fairly cheap route to increase rate of acceleration. (I do it all the time on Jeeps as required to overcome ever bigger wheels being fitted and keep it driveable off road)
Of course it's not 'free' performance and you will without doubt increase fuel consumption all the time as at any given speed the engine will be running faster, albeit under less throttle. You will compromise top end, not that it may matter to many and create a tiresome drone a bit like driving in a 1/2 a gear too low all the time.
I built a mini years back that was totally nuts in the 0-60 and through the gears, in its day leaving everything behind and spinning front wheels in third, but it topped at 75 even with a 1340cc race tuned engine :thumbsdown:
Of course it's not 'free' performance and you will without doubt increase fuel consumption all the time as at any given speed the engine will be running faster, albeit under less throttle. You will compromise top end, not that it may matter to many and create a tiresome drone a bit like driving in a 1/2 a gear too low all the time.
I built a mini years back that was totally nuts in the 0-60 and through the gears, in its day leaving everything behind and spinning front wheels in third, but it topped at 75 even with a 1340cc race tuned engine :thumbsdown:
Hmmm... something to think about i guess, and can always swap back if it didn't feel right or was killing the mpg.
Cost wise, (a new/recon diff from the 2.5si) what are we talking?
The car is due an oil service, and was thinking I'd get the transmission fluid changed at the same time. This may smooth things out.
Also, I had a rediculous buckaroo moment the other day trying to downshift too quickly, assume it was the cdv, this will be getting removed! :lol:
Paul
Damn it, I didn't think I'd do anything to this car, now the list is growing.
Anyone have a spare M sport front bumper, my deal has gone south
Cost wise, (a new/recon diff from the 2.5si) what are we talking?
The car is due an oil service, and was thinking I'd get the transmission fluid changed at the same time. This may smooth things out.
Also, I had a rediculous buckaroo moment the other day trying to downshift too quickly, assume it was the cdv, this will be getting removed! :lol:
Paul
Damn it, I didn't think I'd do anything to this car, now the list is growing.
Anyone have a spare M sport front bumper, my deal has gone south
Turbo cars will always feel faster than N/A. Even if they are not. I know what you mean about it feeling 'slow' It certainly isn't slow but with the smoothness of the engine etc. it feels like your doing 30mph when really your doing 60.
You wouldn't really see a huge difference but think about a few induction mods and then a remap, if your not bothered about the cost for a smallish gain.
You wouldn't really see a huge difference but think about a few induction mods and then a remap, if your not bothered about the cost for a smallish gain.
T2FFN said:Hmmm... something to think about i guess, and can always swap back if it didn't feel right or was killing the mpg.
Cost wise, (a new/recon diff from the 2.5si) what are we talking?
The car is due an oil service, and was thinking I'd get the transmission fluid changed at the same time. This may smooth things out.
Also, I had a rediculous buckaroo moment the other day trying to downshift too quickly, assume it was the cdv, this will be getting removed! :lol:
Paul
Damn it, I didn't think I'd do anything to this car, now the list is growing.
Anyone have a spare M sport front bumper, my deal has gone south
I had the final drive changing in my TVR T350 - from 3.54 to 3.91 (you don't change the whole diff - just the crown wheel and pinion). The car is too highly geared as standard, and this made the car a lot more 'in the power band' all the time. Note that it will mean even 5th/6th are geared lower and you will thus suffer say 10% worse fuel economy even when cruising. I suspect it will be too costly for most - it cost me £1200 on the TVR, and that is with 'normal' race-car stylee parts and not some BMW specific bits.
The buckaroo moment could have been the delay due to the CDV, but it may also have been bad rev matching on a 'sporty' downshift. Are you familiar with driving a RWD car hard? It can be easy to lock the rear wheels when doing fast downshifts unless you add some revs, resulting in brown trousers/a spin/a visit to the nearest ditch or lamp post depending on various factors. This is exactly why the new Nissan 370z has that clever rev-sync technology - because most mere mortals can't (or don't know about) heel & toe.
T2FFN said:
I swapped to a 3.64 differential from a 3.07 and haven't experienced a change in fuel economy in daily driving in my '04 Z4 3.0i...credit BMW's ECU programming.
Cost is lowest with a salvaged differential. BMW differentials are quite ruggedly built and should not need reconditioning. Even a new one costs no more than a performance cam and installation is much less expensive and less technical.
Smooth downshifting depends on the position of the accelerator pedal at clutch engagement. What works for me is to keep the accelerator in exactly the same position through the whole (down)shift. I know this sounds strange if you were taught to take your foot off the accelerator when depressing the clutch, but it works beautifully and it's actually easier on the gearbox.
Tref said:
:lol: Yep, got plenty of driving quals, including close protection anti-hijacking stuff, so I'm fine with rwd
I usually blip the throttle during a downshift to lift the revs so its smoother (and sounds nice 
), heel and toe isn't really required for road driving imo, unless you're a racing driver by trade and do it out of habit 
I might have to speak to my garage changing the diff gearing, they're all ex-bmw and pretty decent guys.