Last post on Mar 24, 2013 at 11:51 AM
You are in the BMW 3-Series
What is this discussion about?
BMW 3 Series, Sedan
Feb 21, 2003 (10:23 am)
Looking at the bmw web site one can find for the 2.5 liter 6:
1995 - 189 hp5900 -> 168 ft-lbs 5900
1998 - 168 hp5500 -> 160 ft-lbs 5500
1999 - 170 hp5500 -> 162 ft-lbs 5000
2001 - 184 hp6000 -> 161 ft-lbs 6000
We can furthur compute that at 6000 RPMs the torque is less than:
1995 - 165 ft-lbs
1998 - 147 ft-lbs
1999 - 149 ft-lbs
2001 - 162 ft-lbs
So I think the 2001 engine has more torque at low and high speeds than the 99-2000 engines. I suspect that the 95 engine was not good below 2000 RPMs. But others on this forum can speak to that.
Feb 21, 2003 (12:21 pm)
From 92-95 there was no 328, so of course the 2.5L made more power. When the 328 arrived, note the immediate and substantial loss of output.
Feb 21, 2003 (2:35 pm)
Very interesting stuff is there a web page with all the differences that happened from 97 on. I really have to check with my insurance for the M3. I pay 140 for 4 months and then I get 2 off but that is for my 96 civic. It really is interesting to read all the differences between the cars.
#22000 of 30250 MY2000 Data--Torque
Feb 21, 2003 (3:32 pm)
fjk... Why didn't you include the MY 2000 torque and hp data? (Methinks some of your numbers are off. The 2.5L torque data for 1999 and 2001 seems too low.)
Feb 21, 2003 (3:45 pm)
shipo and others have posted the peak torque. What I did is compute backward from the peak horsepower, the torque at that engine speed. We know that the peak horse power is at 5500 on the 1999 and 2000 MY engines. So the torque 6000 RPMs will produce no more horsepower than 5500 which puts an upper limit on the torque at 6000 RPMs. Generally torque drops off fairly quickly after the peak horsepower is reached (for increasing engine speed).
Does this make any sense? Note that I have a typo on the engine speed for the 1999 models: should be 5500 RPM's!
#22002 of 30250 Lost on Torque Analysis
Feb 21, 2003 (4:14 pm)
fjk... Peak torque is normally produced thousands of RPMs less than peak HP. IF the torque curve is flat enough, torque decline won't be too bad at peak HP RPM. Key is to have high torque and flat torque curve. I-6 helps do this as does double VANOS and all the other things BMW does to have efficient and effective high output engine.
But if I'm interested in peak HP, driving at those high RPMs, I'm not normally too interested in the twisting power of the resulting torque and vice versa. That is why modern high torque European diesels are so interesting for real world purposes from standing start and speeds around town. Torque equal low end response; HP equal high end response & top speed.
Feb 21, 2003 (4:42 pm)
What I demonstrated was that the 2001 engine does have a "flat" torque curve relative to the 1999-2000 engine (2.5 liter). I also demonstrated that the torque curve is not flat.
It may be easier to grasp if I make things relative:
1999-2000 engines: 181 ft-lbs3500 170 hp5500
At the peak hp the torque is 89% of peak and by 6000 RPMs is not more than 82% of peak
The 2001 engine: 175 ft-lbs3500 184 hp6000
At the peak hp the torque is 92% of peak and 90% of the older engines peak. This is a flatter torque curve. Is this clear?
#22004 of 30250 Guess I Need to See The Torque Curve Graphed
Feb 21, 2003 (5:40 pm)
fjk... Give me their respective HP and torque output figures at 2K, 3K, peak torque, 4K, 5k, 6k, and redline. That would let me see how flat their respective torque curves are.
You've lost me. First, not sure where you are getting the torque data at RPMs not shown in BMW or other published sources. Second, thought the flatness of the torque curve is NOT automatically relative to HP. It is more an absolute figure determined by how much the torque number varies across the engine's RPM curve. Same for the HP curve. Take two entirely different engines. One has twice the torque and 3 times the HP as the other. But if the lower output engine has no variability in torque over its torque curve, it would be absolutely flat, regardless of its HP curve or the HP and torque curves of the other engine.
Feb 21, 2003 (5:44 pm)
Horsepower is a function of the torque and engine speed. This is physics. So we have two published torque numbers, the first one is torque, the second is horsepower from which the torque can be computed. This may be beyond your capability to grasp.