The real top speed of our 951's?

[Yan]

Hi!

Today, I made some tests using Cartest and according to the maths and our gearing ratio, the 1986 951 redlines at 155 mph in 5th gear. Also, beside the results that Car and Driver obtained concerning the reached speed in each gear, Cartest was a bit optimistic. What are the real specifications?

Does anybody have a magazine really explaining it all? I thought that ours cars were capable of 160 mph with minor modifications.

Thanks!
Yan
1986 951, 90K miles

[justin]

Hey Yan, where did you get this Cartest thing...never heard of it,can you download it off the internet?

[Yan]

CarTest is an automobile maximum acceleration computer simulation. The user enters the specifications for an automobile and CarTest will mathematically accelerate the car from a standing or rolling start until maximum speed is reached. The simulation is time-based and event-driven. That is, the acceleration times are not explicitly calculated but, rather, time progresses at small increments and the usual events that take place during acceleration: clutch dump, wheelspin, shifting, etc. happen in proper course. The acceleration times are arbitrary milestones that are reached during the car's response to these events.
Program Capabilities:The user can choose from among the following:
-Edit/Analyze Car - Modify data for an existing car and/or perform analyses.
-Add Car - Add a new car to the database by inputting the 33 required values (11 engine, 10 drivetrain, 12 chassis and body) all of which are readily available from magazine road test specifications pages.
-Delete, Rename, or Copy a car.
-Comparison Tests: Race up to six cars in a one-quarter mile drag race on screen or produce various plots and listings comparing various aspects of car performance, or rank cars by various performance criteria.
-Track Tests: Race a car (against an optional pace car) on any of the 50 top race circuits in the world to assess track performance.
Calculated specifications:
-Standing Start Acceleration
-Rolling Start Acceleration
-Optimize Launch Method
-Display Horsepower and Torque Curves
-Display Power Loss Component Curves
-Display Drive Power in Each Gear
-Display Speeds in Gears
-Fuel Economy
-Skidpad and Slalom

Most cars until ~1998 are listed in this application, and the results are relatively accurate. For example, I tried to reproduce the same results as obtained with my G-Tech Pro (0-60 mph in 5.5 seconds, 1/4 mile in 13.9@107.9 mph) and the power-torque specifications were approximatively 248 rwhp @ 5400 rpm and 264 rwlb-ft @ 3200 rpm. As you can see, the application is a bit optimistic but still near the reality.

You can download it at:
http://www.cartest2000.com/data/cartest.exe

Have fun!

[adrial]

Thats the coolest thing I've ever seen....I showed it to a few people and they loved it...

goin to spread the word...

--Adrial

BTW I believe the top speeds people see are gotten by exceeding the 6200rpm redline..

[ribs]

Well...One time I got my speedometer up to the 170 MPH hash, and my engine was putting along at around 6200 RPM's in 5th gear. Another time, the speedo read 165ish MPH, but the tach was over 6600 RPM's and the engine was slowly bouncing off of the rev limiter. I believe I was going faster when it read 165 MPH, but I don't know. Don't try this at home folks, and as always, YMMV.

[justin]

Does a 83 model have a rev limiter? If it does when should it kick in?

[1.2gees]

I've had my no full boost hitting POS turbo up to an indicated 145, but it was still pulling very strong. I think it should have no problem breaking an indicated 160, which is probably a bit faster than the real ground speed of the car. I believe for the early turbos it should be aorund 157mph stock.

Pretty sure the gearing of a 944 NA is good for 170mph+, but the engine will not have enough power to push it past ~138mph (should be around 145mph indicated-don't hold me up to that!). Which means you will NOT hit the rev limiter in 5th. In other gears it'll kick in at redline (top off my head 6250rpm?).
Ahmet

[Bob's944]

On stock tires, this is how fast an NA will go IF it can push into the higher RPM range. There should be a similar chart in the back of the turbo manual. Reality is that wind drag limits the top end with stock HP to somewhere around 130 mph or so depending on temperature, wind, altitude, road grade, state of tune, quality of fuel and so on. Larger rear diameter tires will also make top end potential higher. You should be able to chart top speed and peak horsepower higher than stock along the curve if you know the real comparible horsepower of a modded car and it corresponding top end.