Quick question

[CassiesMan]

Not sure if this is the right place to drop this, but, I have a question in a bit of an argument. Well two questions really.

1)What is the difference between aerodynamic and electronic limitation. For example, my car stops accelerating at 129mph. However, the speedo goes up to 155. My friend claims that this is just so that the speedo looks good, and that my car couldnt reach 155 (Not saying it could, and if it did, it would probably take a good two or three minutes). Also, when top speed numbers are givin' are those limited or physical?

2)The best search we could find has a BMW E46 ///M3 rated at a 4.8 0-60, and the '05 GTO at 4.9. Now then, not turning this into a GTO v M3 thread or a flame war or what not, the question my friend wants to know is what has the S54 been modified with. He doesnt quite understand that its a performance engine and that a I6 could hold with a V8, and thinks that the S54 is a heavily modified 3.2, even though its only used in the M Coup and M3? Or, to ask it better, why is the LS2 (I think thats what in the 05 GTO, not to up to date on my Chevy Engines?) not a performance modified engine and the S54 a performance modified engine?

Also, if possible, put any form of credentials, or links supporting your point, becuase my friend also thinks everyone on AF is lying and a BS artist.

[ec437]

aerodynamic limitation is when the engine doesn't have enough power to force the car any faster through the air. Electronic limitation is when the ECU won't let the engine exceed whatever RPMs in whatever gear.

[sierrap615]

Originally Posted by ec437

aerodynamic limitation is when the engine doesn't have enough power to force the car any faster through the air. Electronic limitation is when the ECU won't let the engine exceed whatever RPMs in whatever gear.

exactly, the limiter in the ECM/PCM is used for safety reasons(set to the speed limit in japan IIRC) the biggie is that lots of peices stock from the factory are not rated to the aerodynamic limitation speed, your car would be flying apart before you reached the true top speed.

[curtis73]

Many cars are also speed limited. For instance, my 1991 Beretta was limited to 110 mph. The computer would shut down fuel based on speed even though I had another 1500 rpms to go.

Your friend is right on at least one thing. Speedos have NOTHING to do with top speed. I had a 1983 celebrity that had an 85 mph speedo and I had the needle buried somewhere in the dash many times. My 1996 Impala SS has a 160 mph speedo, but it will never get there.

You can also NEVER compare 6-cylinder vs 8-cylinder or any other type of configuration. The bottom line is this: Engines make torque. How much they make and where they make it in the RPM band determines HP. Period. Sometimes orientation makes a difference. For instance, a 4.3L V6 like is found in S10s might have a different torque/hp curve compared to a 4.3 V8 like is found in L99 Caprices... but forget I6 versus V8.. its bull.

Top speed is only vaguely determined by power. My 450-hp 454 in my 1973 Impala Station Wagon is probably good for about 120 mph. Put that engine in a Lotus and its probably good for 190 mph. Aerodynamics, weight, and gearing play very important roles.

Finally, acceleration numbers have almost nothing to do with top speed. Top speed is a dance between power vs. drag. Acceleration is a dance between power, traction, and weight. Entirely different animals.

If you put either of those engines (the LS1 or S52) in a Van, they would probably go 0-60 in a similar time, but their top speed might be 110 due to wind drag.