3.6 Conversion: How Fast Does It Go?

[CharlesJones]

Originally Posted by peritus

Yes, I know.. and actually I lived in Scotland for a few years.. but Ontario just recently imposed a new law, whereby a police officer will take away one's license and impound their car, as well as give a $10,000 fine for going 30 mph over any posted limit.

Ouch, that's ridiculous! That's just so draconian! That's the sort of law which would make people want to move. Mind you, I think it's going this direction in most countries now - in the UK for example, you hear of people getting prison sentences for speeding, and it's going that way in Ireland too. Soon the only people how will be allowed to enjoy spirited driving will be police officers themselves.

[cashflyer]

Originally Posted by CharlesJones

That's interesting. So does the top speed remain the same due to gearing, regardless of the extra power?

Well at least it will get there much quicker!

If two engines have the same redline, and are fitted to the same transaxle, then the top speed will be the same.

The two ways to get more top end, assuming you aren't aero limited, is to build the engine so that it will safely turn a higher RPM or to regear the transaxle so that it has a higher final drive ratio (or install taller tires).

[Kevin Stewart]

cashflyer, the 3.0 doesnt have a enough hp to push it through the wind to achieve the same speed as a 3.6.

when i was a kid everyone had the same story yep at half pedal i was doin 110 so at full pedal i know i could have gone 150, reality was they could have went to the floor and still only went 110. I know on paper it says both motors will do the same speed according to gear ratio and redline, I truely dont believe a 3.0 can redline in 5 gear, when my car had a really healthy 3.0 125 to the floor was all it had with the 3.6 i have went 140. Kevin

i dont even believe porsche quoted top end more then 128,

[Joe Bob]

Originally Posted by cashflyer

If two engines have the same redline, and are fitted to the same transaxle, then the top speed will be the same.

The two ways to get more top end, assuming you aren't aero limited, is to build the engine so that it will safely turn a higher RPM or to regear the transaxle so that it has a higher final drive ratio (or install taller tires).

Yup, just like adding more or larger coolers will not lower operating temps....it's a function of limitations. You'll get there faster, stay cooler longer with engine and cooler mods.

Thermostats, gearing, aero dynamics, etc.....are a limiting factor....

[Christien]

James, I think it's only a $1000 penalty, not 10K, isn't it?

I can't possibly imagine going 140 in an SC-based car, no matter what the suspension upgrades! I hit 230 km/h on the back straight at Mosport (about 144 mph) in a 996TT and the car felt anything but planted. At first I thought it was maybe just windy at the top of the straight, but the 2nd day was dead calm. The car felt very skittish, like the slightest gust of wind would just whip it around and into a wall. I'm sure it had power to go much faster, but I didn't have the balls...

[peritus]

Originally Posted by Christien

James, I think it's only a $1000 penalty, not 10K, isn't it?

I believe $10k is the max amount, probably depending on the officer's mood and your (the driver's) attitude.

I think if we had an Autobahn to practice on, the sensation of experiencing 140 mph would hit a certain comfort zone only Europeans get to feel...

[peritus]

Chris, we'll take my SC up to 140 mph at Dunneville next weekend!!! You can drive!! Is there a hundred yard stretch where we can open her up at that track?

Remember to bring your crash helmet!

[sl951]

I've personally tested two V-Ram 3.6 conversions -
915 box & G-50 box. 2200-2400 lb range, with 16" R-compound tires.

Numbers were easily repeatable (not just 1 glory run), yes tires helped:

0-60 = 3.8-4.0 sec
1/4 = 12.5 - 12.6 ~ 117 MPH

G-50 car will do 165 MPH, and probably very close to 170 if you had 7,000 redline.

[peritus]

Originally Posted by sl951

0-60 = 3.8-4.0 sec
1/4 = 12.5 - 12.6 ~ 117 MPH

That's awesome!

I'm too nervous (poor) to try 0-60 time trials with that ol' 915.

It's good to know though. Thanks!

[martin_gibson]

Originally Posted by Christien

I can't possibly imagine going 140 in an SC-based car, no matter what the suspension upgrades!

In the almost 10 years that I have owned my SC, I have probably hit over 140mph on a dozen occassions, but always on straight, relatively clear modern European (or Asian) highways and always in good weather.

My SC was originally equipped with a 'sports pack' turbo tail / front spoiler, bilsteins and 7"/8" Fuchs and it now wears a ducktail, but at 'high' speed it has always hunkered down and tracked straight (always on Bridgestone SO2's)and true 'without' recourse to any specific suspension upgrades.

The only time it feels a little nervous is when those (normally insignificant) motorway bends approach at which point I'll certainly back off (993/965 caliper assistance) as a cautionary measure rather than a lack of faith in the machine.

The bizzare thing about Autobahn driving is the number of Audi A4/A6's diesels that seem to be overtaking at these sort of speeds, but as you might imagine german lane discipline is second to none and drivers seem to be very much more aware of other drivers which unfortunately is not the case in the UK.

You guys really need to save up for a European 'budget' flight and hire a car for a trip to the Ring 'before' the European Union bans it and the Autobahns that get you there.

Martin
911SC 3.6

[peritus]

Originally Posted by martin_gibson

You guys really need to save up for a European 'budget' flight and hire a car for a trip to the Ring 'before' the European Union bans it and the Autobahns that get you there.

Am I wrong in thinking that there are statistically less accidents / fatalities (whatever) on the Autobahn vs. speed regulated motorways around the world?

[martin_gibson]

Originally Posted by peritus

Am I wrong in thinking that there are statistically less accidents / fatalities (whatever) on the Autobahn vs. speed regulated motorways around the world?

No idea but Wikipedia says the following:

Accident Record
The overall safety record of autobahns is comparable to other European motorways, and generally motorways are considered safer than other road types and despite the high traffic density comparably low. A 2005 study by the German Interior Ministry indicated that motorway sections with unrestricted speed have the same accident record as sections with speed limits. The only identifiable source of traffic risks in connection with speeding have been high-powered, light trucks that came up within the last 15 years and as their used by courier services (e.g. Mercedes-Benz Sprinter and trucks alike). Over the years they were only capable of speeds comparable to heavy duty trucks, but since manufacturers began to build in significantly more powerful engines they attain speeds of up to 180km/h. This led to a significant portion of fatal accidents being caused by such vehicles due to the driver overestimating his or the cars ability to cope with sudden and heavy braking, side-winds etc.

Public debate
Since the mid-1980s, when environmental issues gained importance and recognition among lawmakers, interest groups and the general public, there has been an ongoing debate on whether or not a general speed limit should be imposed for all motorways. Typically a car's fuel consumption increases with speed, and fuel conservation is a key factor in reducing air pollution. Safety issues have been cited as well with regards to speed-related fatalities. Those opposed to a general speed limit maintain that such regulation is unnecessary because only two percent of all roads in Germany would be affected and because better fuel economy even at high speeds has been achieved in most modern cars. Moreover, recent accident statistics don't lend proof that traveling at high speeds is significantly more dangerous. Another reason is that the German cars have a high speed image and so the car lobby (ADAC, Porsche, BMW, etc.) is against a speed limit. [citation needed]

Twenty years after the beginning of this debate, there are no plans by the German government concerning such a speed limit.

In the discussion about such plans during his political term of office, the former Bundeskanzler Gerhard Schröder called Germany an "Autofahrernation" (a nation of drivers) to point out the fact that a speed limit would not be generally accepted by the public

Martin
911SC 3.6

[layzee]

Well the safety record of UK roads is significantly better than in Germany. I think people get carried away singing the praises of German roads and driving. They are aware of other high-speed traffic but then you'd expect that if it was a common occurance.

I have seen my fair share of terrible driving in Germany just as in other countries in Europe. In fact I would say the standard in the UK is better - Germans are more aggressive, cutting in at the last moment etc etc.

[rattlsnak]

Originally Posted by cashflyer

If two engines have the same redline, and are fitted to the same transaxle, then the top speed will be the same.

The two ways to get more top end, assuming you aren't aero limited, is to build the engine so that it will safely turn a higher RPM or to regear the transaxle so that it has a higher final drive ratio (or install taller tires).

Quote:
Originally Posted by CharlesJones
That's interesting. So does the top speed remain the same due to gearing, regardless of the extra power?

Well at least it will get there much quicker!

We had this debate in college, One side said as above, one side said absolutely not true.

The opposing side-- If an engine is producing more power, it will take less of that power to equal the same speed.

ex. 6,000 RPMs in a 2.0L will give you 140 MPH, but 6,000 RPMs in a 3.6L will give you 165 MPH, with the SAME gearbox.

[silverc4s]

Originally Posted by rattlsnak

Quote:
Originally Posted by CharlesJones
That's interesting. So does the top speed remain the same due to gearing, regardless of the extra power?

Well at least it will get there much quicker!

We had this debate in college, One side said as above, one side said absolutely not true.

The opposing side-- If an engine is producing more power, it will take less of that power to equal the same speed.

ex. 6,000 RPMs in a 2.0L will give you 140 MPH, but 6,000 RPMs in a 3.6L will give you 165 MPH, with the SAME gearbox.

The opposing side is absolutely incorrect in this case. A mechanically connected engine, gearbox and differential will ALWAYS result in the same wheel rotations per engine rotation in a given gear, regardless of the engine connected to the gearbox, etc.

The difference comes in the engines ability to overcome all of the opposing forces (gravity, air resistance, rolling resistance, etc.) as compared to another engine. The 3.6 will just sneer at forces that will bog down a stock 3.0 CIS engine.

I recall years ago having a Yamaha 2 stroke road bike that was actually faster in 4th gear than in 5th under most conditions. An upshift to 5th at redline would find you starting to slow down, as there was not enough (hp, torque) at the wheel to keep up the pace.

[wide911guy]

Im seeing people who are mentioning the G50's alot. Are there any strenght differences or speed differences of one over the other trans?? I cant thing a G50 is a faster box stock over the 915, right? Dont mean to change direction here...

[johndglynn]

Originally Posted by jevvy

I'm not a street racer or anything daft like that but these are just observations I have made while pootling about

Pootling about on the tail of an R8... LOL

Whatever you say Jev

[87coupe]

Originally Posted by wide911guy

Im seeing people who are mentioning the G50's alot. Are there any strenght differences or speed differences of one over the other trans?? I cant thing a G50 is a faster box stock over the 915, right? Dont mean to change direction here...

• The G50 is stronger than the 915.
• The gearing of the top gear on the G50 equates to a higher theoretical top speed (if you have the power to get there).
• Neither is really "faster" than the other as the gearing is just one piece of the "fast" equation.

Do a search and you'll find Bill V. has graciously provided ample info on this subject.

[Bill Verburg]

Originally Posted by wide911guy

Im seeing people who are mentioning the G50's alot. Are there any strenght differences or speed differences of one over the other trans?? I cant thing a G50 is a faster box stock over the 915, right? Dont mean to change direction here...

Ignoring aero and slipage, speed in any gear is dependant on gear ratio, final drive ratio, rpm and dynamic loaded tire radius.

There were dozens of combinations of the above used on various 911s from '72 - today

here is a comparison, no attampt was made to normalize for a specific tire or rpm.
some common 915s


some common G50 5 speeds


and some G50 6 speeds

[Kevin Stewart]

Bill I think your chart is great, and it does show what our cars should be able to do, and i am actually going to copy and save the chart, I have never seen a better gear ratio chart.

on top end air and HP will be the factor that limits our cars from actualy achieving the numbers. There is a possibility that a strong tail wind will help one of our cars achieve these numbers. Remember I am talking about bone stock cars with no mods, or maybe a slant nose, lowered roof, even the windshield angle is not even within the angle that will allow it to slip through the wind, Kevin

on another note most cars dont even have a tire rated to achieve these speeds safely, i know the oe sc tire was an explosion waiting to happen.

I mean this in no way disrespectful to anyone