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Posted by Peter on February 08, 2000 at 02:27:03:

In Reply to: Re: Here is the real deal!! LooooonG posted by Paul E on February 07, 2000 at 15:26:07:

: : There seems to be a misconception about the differences of the 3.0L motor and the 3.2L motor.
: : after reviewing some paper work and checking out some dynojet runs of both 3.0s and 3.2s before and after SC'ing l found what l originally thought was the case.....l will try to scan them in and post them but for now here are the numbers and descriptions of the runs.... all runs are at the wheel figures.

: : For the 3.0L @ 69 deg.F
: : Stock HP = 205.3 HP @ a range from 5500 to 6500
: : Stock TRQ = 208.6 lbs @ 4300

: : For the 3.2L @ 84 deg.F
: : Stock HP = 200.4 HP @ 6150
: : Stock TRQ = 211.6 lbs. @ 4000

: : Now for the Supercharged figures

: : For the 3.0L @ 65 deg.F
: : SC'd HP = 304.7 hp @ 6500
: : SC'd TRQ = 255.7 lbs. @ 4800

: : For the 3.2L @ 50 deg.F
: : SC'd HP = 289.4 @ 6500
: : SC'd TRQ = 256.6 @ 3900

: : All dynojet pulls were done at ERT in Delaware. Looking at the numbers you can see why the claimed to fame power advatage of a 3.2 over a 3.0 is not only non-existent but its actually the other way the stock pulls the 3.0 had the cooler temp advatage, so given the same temp..the 3.2 would probably pull similar HP numbers but the 3.0 still puts out peak HP for a 1000rpm range while the 3.2 peaks for a moment and then drops....and torque figures are surprisingly close. advantage goes the the 3.0s top end pull...(which is what counts)
: : In supercharged format the the temperature advantage goes to the 3.2L and the 3.0L still pulls 15hp more and only loosed out on torque by less than one pound. By looking at the curves, the 3.2L power curve looks like a rollercoaster up top in SC'd form...not smooth at all...probably due to the restrictive manifold is having a hard time dealing with the all the extra air coming in. The 3.0Ls free flowing int.manifold flows smoothly all the way to the top and this is the reason for the difference in power. So to sum it up....SC'd 3.2 is not faster than 3.0.....other way around if anything!!!!! Hope this sheds some light on the subject

: : Cheers
: : Peter

: I'm sure this is what you found...But I'm also sure its not universally found this way...Why do 2/10 litre of size do nothing for the torque figure on your pulls, when in stock trim, BMW and others report an 11 ft lb advantage, owing directly to this extra stroke? Also, I've heard others attribute this 'rollercoaster' apperance of the curve, at least if it is a very 'quick' and 'jagged' rollercoater appearance to the Vanos doing its thing...This is how it usually appears on a pull...It usually hits at about 4k rpms for a portion of the curve, before it smooths out again. I'm not disagreeing with you...I just find it strange why BMW ups their power figures with the bigger (slightly ) engine, but your pulls dont seem to show it.

: BTW, is your SC working at 6 psi? Is it a Powerdyne? Thanks.

Here is why the stock pulls were so close in the torque category... Temperature. The stock 3.2 run was done in 80+ temp. and the 3.0 in 60+ temp. that explains the disprepancy. in the same temperature the stock pulls would probably be the same in HP and the 3.2 would make a little more torque supporting the claimed 11lbs. diff. in TRQ.(see stock temp/TRQ figures above) Remember also that the 11lbs is crank power not the wheel that is about 8lbs. diff. only. And l am very aware of the infamous Vanos power curve during lower timing transition. Let me also tell you that the supercharger makes that little zigzag on the power curve virtually invisible. What l was refering to was a deep up and down that started occuring at 6000rpm and went till on redline (6-8hp dips). l believe this is because of the int. manifold that is so restrictive and is having a hard time dealing with the extra air the SC is putting in. And that is the main reason why the 3.0s make more usable up top power than the 3.2s....If you had that manifold on your car it would be unstopable. l am not arguing the benefits of higher displacement! But in this case there are other factors that are acting as the limiting factors on these motors. All being equal...of course the 2/10ths of a liter would make a sweeter difference. But unfortunately it is not the case this time. And my car is not SC'd....l've just been tunning and playing around with these things for a while...but l hope the info helps and that all is clear..
Take care


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