[flash]

i finally got cartest2000 working on the new mac - WOW!!!





with this software i can plug in different parameters and it will calculate what the car will do - i can adjust hp, torque, rev limits, launch revs, tire size, frontal area, height, ride height, yada yada



you can get 0-60 times, 1/4 mile times, top speeds - whatever



very cool stuff - it already had both a manual and tip 968 in its database too - insanely accurate results



you can even match up cars and race them around a choice of 50 tracks - extremely fun and very informative



there are definitely limits to what it can do, and a number of things are missing that are needed for determination of actual top speed, (like underbody aerodynamics and downforce figures), and suspension setup changes to determine real skidpad ratings and cornering speeds, but it gets a really good estimate, and a whole lot better than any of the other calculators out there



lol - the downside is that it also clearly showed that it takes a lot more power to go really fast than people think it does

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[flash]

for those out there who are curious, the top speed of the stock hardtop 968 in perfect running condition (100% compression, etc) is 156 - the tip is lower due to the gearing and additional drivetrain loss



keep in mind that the stock redline is 6700 - to reach any real top speed, that needs to go up



using factory specs on the car itself:



to reach 160, you need 260hp and torque increase to match



to reach 165 you need 275hp



to reach 170 you need 315hp



to reach 180 you need a whopping 450hp and you need to raise the rev limit



other calculators inaccurately tell you that you could go 190 with that power - not going to happen - it's a lot more than just tire diameter, gear ratio and hp - even the wheelbase plays into accurately calculating top speed capability



so, anybody telling you they are going 165 in a stock 968 is pulling your leg - i'm willing to bet that there are very few cars out there anymore actually capable of cracking 150 in stock trim - a really tight runner with a good chip, airbox, and cat-back might hit 160, but that's it guys - even the 337hp Turbo RS only did 175 (the Turbo S doing that is a misprint carried over from the RS and perpetuated because nobody actually tested one to discover the error), and even then they added a bigger wing and a splitter, lowered the car, and changed the gearing to get there



but the software is really fun to play with and see how much power it takes to go how fast



i'm actually looking forward to a planned run at bonneville - until then, i'll have to rely on the GPS on the radar detector, and the NAV unit for a true reading, since the speedo is way off up at the top end (they all are)

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[94SilverCab]

A bit off topic, but since you brought it up...just how accurate is a GPS calculated speed? If my standard out of the box Garmin Nuvi says I'm doing 60 MPH is it 100% correct...how long would I need to sustain that speed for an accurate reading? If I take my car out and blast it, would the highest calculated speed be accurate if I maintained it for 10-20-30 seconds?



Jay

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[flash]

you have to read up on the data update rate of the particular unit - the GPS in my radar detector is fairly fast, and updates every second or so



if you ran at a given speed for 10 seconds, the latest reading should be accurate - this of course must be on flat ground and straight, as it calculates based on that

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[rhudeboye]

Sounds like a pretty fun tool.



Hey- Can you input the HP form your dyno results post SC, then play with the weight, down force, suspension etc. to see what happens with your 0 -80 ?

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[flash]

lol - yes - did that - fun stuff - matched up pretty well to the road tests i did (which i already posted)

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[Lord_Galva]

So the real limiting factor is the engine not the transmission?

I understand that lighter weight will speed up 0-60 times.

Actually that is a little depressing. <img src="/forum/images/smilies/968/dry.gif" class="smilie" alt="" />

I've been looking at the power/weight on the new 5.0 Mustang, Camero's, and Challengers.

They are just faster. Even with the Challenger tipping the scale at 4,200 the 5.7L version is quicker off the line.

You need at least 260hp to pass the 5.7L, for the 6.1 425hp version you need to up the 968 to 300hp!

I don't know how tranny affects the take off speed however. The 6.1 only comes in Automatic so maybe the standard chip, exhaust, airbox and a little weight loss could push you ahead.



Am I on the right track Flash?

Trying to understand all this. <img src="/forum/images/smilies/968/laugh.gif" class="smilie" alt="" />

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[flash]

no - the real limiting factor is the body - the engine just has to overcome the Cx to push the car, which isn't helped by the .34 Cx - the body lines then determine stability once you get there



transmissions affect take-off by means of gear ratios - drivetrains affect things by means of power loss



i'm not sure what you are aiming at though, as there is a big difference in 0-60, 1/4 mile and top speed and how you optimize each

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[rxter]

Got mine to 142 on gps. Was going a bit downhill. It felt incredibly stable at speed. I was loaded pretty heavy and my aero was horrible (lots of tape flapping in the breeze and a vinyl bra on the front). That felt like terminal speed - maybe 1 or 2 mph in her but I was very close to the top). And yes I had z-rated tires, brand new properly inflated. Brakes were checked and working properly.

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[ds968]

" to reach 160, you need 260hp and torque increase to match "



I can attest to this. My car's engine has always been as strong as you can find out there in a 968, and I'm guessing that with the chip, airbox mod, and high flow catback I might have been right around 260 hp, even before the head rebuild. On a few occasions ( three times, IIRC ) I had the speedometer at the 160 mark, which I suppose means I was probably going close to 150, and after the head rebuilt I drove to the point where the engine produced no more pull whatsoever, with the speedo near the 170 mark, which again, I suppose means I might have gone 160 or slightly past it <img src="/forum/images/smilies/968/huh.gif" class="smilie" alt="" /> . No idea where speedo error readings start and what the delta is at any given speed, but I can tell you that at 80 mph my speedometer has an exact reading. I tested that on various stationary " your speed is " radar boards ( I know where they are, and there's never any police around them <img src="/forum/images/smilies/968/cool.gif" class="smilie" alt="" /> )

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[flash]

the problem with those things is that you have to be holding a speed for about 5 seconds for them to register accurately, and even then they are somewhat questionable, as there is a tolerance built into them - that's why radar tickets are so easy to beat on their face



to check your speedo, you need to do a measured distance with a measured time - for example, find a truly straight road, with a measured mile, set your speedo at a fixed speed (say 60mph) and start the stopwatch - it should take exactly 1 minute - record the time - if it's off from 1 minute, you can do the math to figure out how much you were off - to really get a good reading, do this for 3 miles (which is why the highway odometer check strips are 3 miles long)



as to the delta, speedos are off more at the top than they are at the bottom - the faster you go, the more error - they are only required to be within 10% at 55mph at the time of manufacture



tire diameters affect this a lot, so new tires will read lower than old tires too, because as they wear, the diameter decreases - the range is usually about 2% from new to the wear bars

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[ds968]

" that's why radar tickets are so easy to beat on their face "



Yeah, right.. <img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" />

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[flash]

they are - but you have to know how to fight them - i've beaten 2 so far



of course it all depends on the judge, and whether or not they are in the mood to listen to you - unfortunately we don't get jury trials in traffic court here in CA, so you are at their mercy, and these days it's pretty much jus about the money and not the trial

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[rxter]

tougher to beat when you are 40 or 50 mph over the posted speed....

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[Lord_Galva]

I find not getting caught an effective strategy <img src="/forum/images/smilies/968/laugh.gif" class="smilie" alt="" />

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[lbpesq]

Actually, in California, radar tickets are often beatable - not because of inaccuracy in the radar, but rather because California law requires a valid traffic survey before radar can be lawfully used (in many cases). If you know what to look for, you will find that most traffic surveys are invalid under the statute in that most do not contain a description of hazards not readily apparent to the driver. This is required under the code and the failure to include this info renders the survey invalid and the use of radar an unlawful "speed trap". I've beat many radar tix for self and friends over the years.



Bill

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[flash]

he is absolutely right

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[Lord_Galva]

[quote name='lbpesq' timestamp='1291383812' post='101930']

Actually, in California, radar tickets are often beatable - not because of inaccuracy in the radar, but rather because California law requires a valid traffic survey before radar can be lawfully used (in many cases). If you know what to look for, you will find that most traffic surveys are invalid under the statute in that most do not contain a description of hazards not readily apparent to the driver. This is required under the code and the failure to include this info renders the survey invalid and the use of radar an unlawful "speed trap". I've beat many radar tix for self and friends over the years.



Bill

[/quote]



I've heard of that.

So how does one use this information.

Can you give an example?



Thnx

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[flash]

at trial it is a part of the defendant's examination process - this particular piece would generally occur during pre-trial discovery - the defendant is entitled to be confronted by the accuser, and examine all evidence - some of that evidence must meet certain standards - if it does not, then you file a motion to dismiss



consult an attorney for advice in your particular jurisdiction



back on topic



i'm going to be playing around with the software today to determine how changes in the torque curve result in changes in and out of corners

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[Nikoror]

I've had CarTest for a long time and it is a fun way to waste time and surprisingly accurate for the straight line stuff, but track analysis is pretty bad just because of the number of variables associated with driving technique (it basically uses straight line braking followed by constant radius turning followed by straight line acceleration)

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