07-22-2014, 02:30 AM | #199 | ||
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I do doubt these other dyno tests because: 1) Motortrend did a test that showed contradictory results 2) I think it's unrealistic that BMW would've under rated their car by that much 3) I don't think that an auto journalist's butt dyno is the end-all-be-all determination of how much HP a car has...but with all the cars they test, they would certainly notice if a car had substantially more HP that what was claimed. So far none have commented on that. 4) the C7 is a bit faster around a track (according to the times put out so far). My lack of a M4 has nothing to do with the 4 reasons stated above. For the record, I wish I had M4 euphoria too. Quote:
The lap times show how fast these cars are running down the straightaway (instead of from a dead stop). The braking is similar between the 2. Your assessment on the C7 having better handling is subjective and others seem to dispute it as shown by the video I posted previously. Though the C7 is 100lb's lighter, that's not enough to account for an over 1 sec difference on the Hockenheim. Most things being equal, or at least comparable, between the 2 cars, the C7's higher HP is allowing it to put out faster lap times...so far. If the M4 truly had something north of 450HP, would that be the case? |
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07-22-2014, 02:43 AM | #200 | |
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So in the same way that the HP and Tq differences can be demonstrated between the E9x M3 and the F8X M4, so too can they be demonstrated between the M4 and C7. As for the cars being tested on different days, unless there was a drastic temperature difference (which it didn't look like there was), I don't see how the test results could have been affected differently on one day versus the other. Everything else in your post was addressed above. |
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07-22-2014, 06:44 AM | #201 | |
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A couple of comments... the auto in the C7 is fast shifting and would not meaningfully impact the car's trap speed. The same thing with traction... some of the 60' times, etc for the C7 have been very impressive. Also, the C7 auto has been faster than the 911S in most tests. The 911S weighs SO much less than both the M4 and C7 that its speed is impacted by this regardless of its HP. In any event, this debate is academic at this point and it has already been beaten to death here in several threads. I believe the general consensus (although I may be wrong) is not in agreement with you and that would include people who are far brighter and informed than I am. You can believe what you want and so will I. Just for the record, I don't really care about HP and straight line speed other than for interest sake. I'm a road course kind of person. My perspective in this debate is not from M4 euphoria but, rather, just my interpretation of a lot of data. I believe you are discounting information, making justifications and interpreting things based on you not being able to believe what you see... I could be wrong but that's my personal view. Let's agree to disagree on this one.
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07-22-2014, 07:37 AM | #202 | ||
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07-22-2014, 11:39 AM | #203 | |||||
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I have a hard time believing that the M4 has +450HP at the crank because: 1) C7, a car of comparable weight, pulls faster 1/4 times, with a manual. 2) C7, a car of comparable, if not slightly worse, handling and braking, pulls a faster lap time. 3) C7, a car with 460HP at the crank, puts out a higher HP/tq result on the same K&N dyno facility. I know that BMW under rates their cars and truly don't care how much HP the M4 has...I just think people are over exaggerating this car's HP capability and are ignoring the real world evidence which shows that. Quote:
http://www.corvette7.com/forums/showthread.php?t=329056 http://www.lingenfelter.com/LPEforum...sis-Dyno-Video http://www.stingrayforums.com/forum/...t-results.html Also, as I said above, dyno tests in and of themselves don't mean a whole lot..it's only when you test 2 cars on the same dyno facility that you get something useful, like Motortrend did with the C7 and M4 at K&N. |
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07-22-2014, 11:53 AM | #204 | |
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You're absolutely right, dynos dont matter unless done at the same location and same settings back to back (generally speaking), but I do truly believe the S55 is making more WHP/WTQ. Where I would disagree is the weights. The vette is much lighter than the M3/M4 (and that's where I think the majority of the performance advantage is coming from, not to mention that big ass rear end) The stingray is a beast and a better track car IMO, but thats another topic.
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07-22-2014, 12:01 PM | #205 | |
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Also, do you have threads/links to demonstrate what you said below: Last edited by Dalko43; 07-22-2014 at 12:06 PM.. |
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07-22-2014, 12:41 PM | #206 | |
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As far as weight, I didn't realize you had specified the Z51. I know base model to base model, the C7 is a good bit lighter.
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07-22-2014, 03:11 PM | #207 |
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I prefer track results. A dyno is good for comparing a before and after or comparing 2 cars on the same day back to back under the same conditions. The numbers themselves are mostly irrelevant but the disparity between them is as accurate as you will be able to measure without pulling the motors and using engine dynos.
As far as comparing the weight vs HP of the cars and determining something from the comparison. Well at the drag strip traction and gearing play a role. It's not so much how fast the shifting as the differential and transmission gearing matched ideally to the engines power curve. Try not to look solely at peak HP numbers. How fast a car is isn't about just its peak numbers. It's more about the curve before and after. The cars will only be at their peak numbers for a moment. Think of the power through the entire rpm range. Look at where the shift points are and how long it takes to first get to its ideal power range and how long it can stay in that range. It's the reason we have 7 and 8 speed transmissions now. The closer the gears are the better the trans can keep the engine in its ideal power range. Also how much parasitic drag does one driveline have vs the other...Weight, design etc all play a part. Overall weight is part of the equation but how much of the Vettes weight is unsprung vs that of the M3. We don't have enough data to make exact comparisons on the chassis. Both cars you are comparing have strengths, both make power and transfer it differently but both are Fantastic platforms. I would expect the Vette to be faster on a race track for a couple of reasons. First its got a lot of tire under it. But besides how fast it is in the turns it can exit the turns with zero lag and a lot of low end torque. Torque is what moves you. Look at HP as more of the potential for higher speeds but torque is what you feel in the seat of your pants and snaps your neck when you accelerate. Also FI cars heat soak on a road course and as someone mentioned the heat on the turbo car will slow it down. I enjoy the discussion. I don't think anyone here is stating untruths about the how and why. There is just some lack of experience here on general understandings of why one car is faster then another. While these ARE factors; it comes down to more then curb weights and trap speeds or dyno sheets. |
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07-23-2014, 09:52 AM | #208 | |
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Would that mean the dyno was set to AWD for the M4 and M3, hence low numbers for both the M4 and M3? The C7 dyno was set to RWD so more accurate to what it should be. |
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07-23-2014, 01:43 PM | #209 | |
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As I posted several time in this thread, since the E92 M3 and F80 M3 were tested with all four wheel rollers interconnected significantly increased the losses and inertial impacts, thus lower WHP numbers. Since the C7 was tested with only two rollers running, it suffered less loss. |
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07-23-2014, 01:45 PM | #210 | |
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The dyno run for the C7 was done in 2WD mode. Lower losses and inertial impacts, hence higher reading. |
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07-24-2014, 04:48 PM | #211 |
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I remember one of the videos saying they have to spin the front wheels b/c the car is programmed to not run after a certain mph if the front wheels arent spinning.
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07-25-2014, 07:34 AM | #212 | |
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There are example of E9X M3s and F8X running on dynos with only the rear wheel turning though... |
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07-26-2014, 07:18 PM | #213 | |||
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The only reason I didn't include those aspects of car performance is because I was trying to focus in on how the C7 is not only faster than the M4 but also has more HP....something more than a few people on this forum refuse to acknowledge. Quote:
But anyone who thinks that the M4 truly has more or comparable HP to the c7, and there are a few on this forum, is living in a fantasy land. That was really my only reason for bringing up the two Motortrend dyno tests. |
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