2005 vs 2006 Z4

[kwakr738]

Hello,

I am in the market for a used Z4. I have been reading that the 2005 3.0i has 225 HP and the 2006 3.0si has 255 HP. I was wondering if the performance is really that much different. I was hoping someone could give me a real world perspective and not just magazine stats. The 2005 3.0i I am looking at has the sexy sport seats, and the 2006 3.0si has the engine with more power. I am wondering if I will regret not having that extra 30HP.

Thanks,
Alan

 

[561design]

Those ratings are from the flywheel and not at the wheel. Anyhow, as a general rule anything of 10hp you notice a difference on the butt dyno. Anything less you won't feel it. Of course this only works if you are comparing similar cars. You can also work out the power to weight ratio and see what the difference is from there.

 

[WLH]

Having had a 2003 3.0i and now driving a 2006 3.0si there is very little difference. Seems to have a just little more punch above 4,000 RPM.

 

[kwakr738]

Thanks guys. I found that the final drive is different too. What is the general rule of final drive? The bigger the number the better the accelaration?


2007 Z4 3.0si
255 hp @ 6600 rpm
220 lb-ft @ 2750 rpm
Final Drive: 3.23

2004 Z4 3.0i
225 hp @ 5900 rpm
214 lb-ft @ 3500 rpm
Final Drive: 3.07

 

[easty027]

i have a 2003 3.0i and had a 2007 3.0si for a week, and i could tell the difference, however i wouldnt say it was massive, however you could tell.

 

[kwakr738]

i have a 2003 3.0i and had a 2007 3.0si for a week, and i could tell the difference, however i wouldnt say it was massive, however you could tell.

To both easty027 and WLH.

...would you pay $2000 dollar more for that difference?

 

[cj10jeeper]

Thanks guys. I found that the final drive is different too. What is the general rule of final drive? The bigger the number the better the accelaration?


2007 Z4 3.0si
255 hp @ 6600 rpm
220 lb-ft @ 2750 rpm
Final Drive: 3.23

2004 Z4 3.0i
225 hp @ 5900 rpm
214 lb-ft @ 3500 rpm
Final Drive: 3.07

Yes the general rule would be that if all other factors were equal then the higher the final drive ratio then the quicker the acceleration to a point, which let's assume is 0-60. It's a bit simple mechanical gearing

However the compromise is that for any given speed the engine will be running faster and will therefore need to change up to the next ratio sooner. That could actually adversly affect acceleration. (By simple illustration suppose a high geared car could hit 60 in bottom it may accelerate faster than one that had to change gears becuase it was low geared. Crude and unlikely but it illustrates)

The car will also run out of revs in top gear and therefore top speed at a slower speed (unless air or mechanical resistence is the limiting factor)

We also have to consider a lot of other things too. Intermediate ratios of the gearbox, rev range of the engine, what revs peak torque is delivered, rolling tyre size and some other minor factors. Add all those together and you come up with the a correct driveline and matching final drive ratio. so the real answer is that the final drive ratio tells you nothing much about the performance of the car. Changing it can destroy the performance unless its part of a thought out sequence of modifications.

Hope this helps.

 

[azroadie]

The si will do 0-60 in 2nd gear for sure...I don't think (not sure) the 3.0i does. If so than there's that extra shift to 3rd to get to 60. I know that's the case with my 2.5i. I drove the 3.0si vs the 2.5i and didn't notice that much of a difference for accelleration...small...but not worth the cost.

Here's another factor. These 2 cars have 2 different engines. So most of the super sweet engine upgrades...superchagers, etc., are only currently available for pre 2005 engines. That weighed into my decision.

 

[kwakr738]

Thanks guys. I found that the final drive is different too. What is the general rule of final drive? The bigger the number the better the accelaration?


2007 Z4 3.0si
255 hp @ 6600 rpm
220 lb-ft @ 2750 rpm
Final Drive: 3.23

2004 Z4 3.0i
225 hp @ 5900 rpm
214 lb-ft @ 3500 rpm
Final Drive: 3.07

Yes the general rule would be that if all other factors were equal then the higher the final drive ratio then the quicker the acceleration to a point, which let's assume is 0-60. It's a bit simple mechanical gearing

However the compromise is that for any given speed the engine will be running faster and will therefore need to change up to the next ratio sooner. That could actually adversly affect acceleration. (By simple illustration suppose a high geared car could hit 60 in bottom it may accelerate faster than one that had to change gears becuase it was low geared. Crude and unlikely but it illustrates)

The car will also run out of revs in top gear and therefore top speed at a slower speed (unless air or mechanical resistence is the limiting factor)

We also have to consider a lot of other things too. Intermediate ratios of the gearbox, rev range of the engine, what revs peak torque is delivered, rolling tyre size and some other minor factors. Add all those together and you come up with the a correct driveline and matching final drive ratio. so the real answer is that the final drive ratio tells you nothing much about the performance of the car. Changing it can destroy the performance unless its part of a thought out sequence of modifications.

Hope this helps.

Thanks for the information. I understand that final drive alone will not determine quicker acceleration. Considering the Z4 being similar, I am assuming that 3.23 final drive and extra HP and Torque shoud improve acceleration. I also noticed that Dinan sells a diff with the 3.23 ratio.

http://www.dinancars.com/store/3.23-Differential-Manual-03-05-c-756-p-1308.html

Considering the cost of the diff and bolt on engine mods, it may be well worth it to cough a lil extra for the 3.0si.

 

[easty027]

Not only did it feel a little quicker, the noise was far better in the 2007 3.0SI !........but no probably not worth $2000 !

 

[kwakr738]

Not only did it feel a little quicker, the noise was far better in the 2007 3.0SI !........but no probably not worth $2000 !

Thanks for your perspective. I will take that into consideration when I get back from vacation in April. I am looking forward to gaining and sharing knowledge with this group.

 

[GP20]

i have a 2003 3.0i and had a 2007 3.0si for a week, and i could tell the difference, however i wouldnt say it was massive, however you could tell.

To both easty027 and WLH.

...would you pay $2000 dollar more for that difference?

If the difference is only $2K, the depreciation factor alone is worth getting the 3.0Si, not to mention you get an extra year of free warranty and maintenance. The extra HP is icing on the cake.