[flash]

it's less than if it were at the outside for sure (like a heavy brand/model of tire for example), but it's there.



here's a fun tool:



http://hpwizard.com/rotational-inertia.html#wheelstires

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[968Syncro]

Just a guess for the more knowledgeable to clarify, but I suspect that 4 vs 6 cylinders has something to do with it. Given the same displacement, and other things being equivalent, it seems like a 6 cylinder engine should "accelerate" more quickly than a 4 cylinder engine (until friction from more moving parts starts to diminish this possible advantage). Reciprocating weight also plays a part, but I have no idea of the weight difference of 6 911 pistons/rods vs 4 968 pistons/rods.



Roland

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[flash]

still searching for the factory dyno chart - having a VERY hard time finding it. doesn't anybody have one of these with an owner's manual?

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[hot968]

I don't know if this ads any thing to this thread but little things sure make a difference in these 968's. My car was unbeieivable fast when I got it then I had the power steering pump and the A/C fixed and now just regular take off, so sad!!

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[mike]

[quote name='flash' timestamp='1349132493' post='133248']

still searching for the factory dyno chart - having a VERY hard time finding it. doesn't anybody have one of these with an owner's manual?

[/quote]

I scanned mine from the owners manual of my '93 C2. When compared to the 968 curve, you can see that following numbers:



964



RPM Torque

1000 ~240

2000 ~255

3000 ~260

4000 ~290 Peaks at ~4900 RPM / ~302 Torque and holds until ~5700 RPM

5000 ~303

6000 ~297



968



RPM Torque

1000 ~100

2000 ~190

3000 ~250

4000 ~300 Peaks at ~4200 RPM / ~302 Torque and holds until ~4300

5000 ~290

6000 ~277



So, the 964 has more torque at just about everywhere in the band and holds the peak torque much longer.

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[flash]

yup - that's what i expected to see - thanks!!!

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[ds968]

Oh crap, I forgot that my AC was on also ( I keep it on pretty much year-round and forget to turn it off..) But I doubt that made a huge difference..however, it might have added yet one more disadvantage. Still, it has to be the gearing / flat power curve that makes all the diff.

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[ds968]

Just saw the charts - the 964's distinct torque advantage below 4000 rpm is not relevant to the particular run we had, but the fact that it sustains the peak after that point for a longer band segment, coupled with the other stuff mentioned earlier certainly explains the acceleration difference. Thanks, curiosity now satisfied .

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[flash]

the AC can pull as much as 25hp. between that, the differential of your full tank vs his 1/4 tank, the crap you carry around int he back, his aerodynamic advantage, and the likelihood of his lighter wheel/tire combination, there is a very real advantage to the 964



yes, the torque curve is the key to how a car accelerates. it's not about peak numbers. our torque drops after 4200 and the 964 keeps climbing. but, that would not make for a "walking away" experience. he would pull away for sure, but i'm still guessing he also was in a gear lower than you.



lol - by the way - i do have a fix for that

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[ds968]

You have a fix for the roughly 50 lbs of crap I carry in the cubby holes, and the spare tire hub ??! ( which defeats the weight savings purpose of taking the spare out of there, lol..). Yeah, yeah I know what you're referring to, but you also know my answer to " that " fix option..



Speaking of the power curve I presume a ' 04 Carrera C4 power curve is even stronger than that of the '93 964 one, but running against the 968 that car fared as badly as I did against the 964.. and it was not the driver, we took turns driving the other's car and in both cases tne 968 won the contest. But..that was a C4 ( not tne S ..) a convertible so extra heavy, tne top was down so a bunch of drag there, a tiptronic, and I did not have the spacers at the time nor all of the crap I now carry around in the trunk, so that HAD TO BE purely a weight issue..in spite of what the specs or power curves may reveal. Those runs were from a roling 20 mph to right around 100 mph, I would have kept going just to see if the C4 does better at higher speeds but he chickened out at 100 , and slowed down after reaching that point, both when driving his car or whn driving mine. The C4 was easily one car length behind the 968 at 100 mph, on both runs.

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[flash]

yeah - i regularly beat the snot out of the C4 convertible when running up and down the 2.8 mile long canyon near the last house. the extra drive wheels, weight, and all that just make the car slow. it feels very planted for a rear engined car, but it is not fast

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[Cloud9...68]

I guess I'm surprised the 968 would even be close to a 964, given the latter car's 20% displacement advantage, more favorable torque curve, and rear-heavy layout. But there's one other factor that's probably even more significant - the 911 has always been Porsche's flagship model, so there's no way Porsche would allow a "lesser" model of the same year to be competitive with the 911.

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[ds968]

now that I think about it I believe it was a 2005, but I presume the same specs. too funny, I recall he said he paid over $ 90,000 for it, and then a sub-$20k 968 humiliates his car.. <img src="/forum/images/smilies/968/dry.png" class="smilie" alt="" /> , but I'm OT now.. we were talking about equal peak power and weight stuff..

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[ds968]

ok, so one more thing given syncro's and cloud's comments re number of cylinders and/or or displacenment . if all else is equal ( hp, torque, weight, power curve, gearing, etc ) it should not matter at all if the car has 4 cylinders or 12 cylinders.. right ? <img src="/forum/images/smilies/968/huh.png" class="smilie" alt="" />

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[flash]

yes it does. the nature of a 4 cylinder limits the shape of the curve, but more importantly, the more cylinders means the more power pulses per revolution. given the same displacement, the more power pulses per revolution, the more torque. the tradeoff though is the extra weight of the increased number of cylinders, and the additional drag of those components. it's pretty complicated, but as a rule, a 6 cylinder will be torquier than a 4 in the same displacement

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[Qfrank]

Try it again with your AC off, and report back the difference.

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[94SilverCab]

Dan,



...Must.Install. NOS......



Jay

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[Rap]

It seems to me that perhaps the only comparison that was talked about were the age of the drivers. Can this make a difference?

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[94SilverCab]

I would not let the other driver's youth and inexperience detract from their superior performance (ala Ronald Raygun)...



Jay

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[ds968]

you guys are too funny.. and, age ?! what, are you implying my reaction time is slower that a 29 year-old's ?! <img src="/forum/images/smilies/968/dry.png" class="smilie" alt="" /> <img src="/forum/images/smilies/968/angry.png" class="smilie" alt="" /> and just so you know, those extra 25 - 30 lbs that I have over him is all muscle weight..yeah, that's it, all muscles.. <img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" />



btw, I just spoke to him, he was in 3rd gear and I was in 4th , though I sense even if we were both in 3rd, and I had the AC off, yada, yada .. the 964 is still quicker by virtue of its torque sustainability ..

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