IS300 Drag Governed or Engine Governed.......

Well, here is a way to check. If anyone can measure the frontal cross section of the car, and then use the CD=D/0.5*ro*v^2*A to figure out D. You then put use the equation P=DV, and you will be able to find out approxmiately how much horsepower is required to overcome drag at 144mph. If the HP is less than what the wheel is outputing, then it means the top speed is electronic governed, but if the HP is greater than the actual output, then you know you are drag limited.

WTF is this:
CD=D/0.5*ro*v^2*A to figure out D

is this a joke or a real equation? urgh math makes my head hurt.

it is a real suggestion. It is not that difficult. Just take a tape measure, find out the exact width, height of the car, and then find the area. Get the density of air and plug them into the equation. Take less than 5 minutes to do this. I just don't have anything to measure my car right now since I am at work, but I may do that once I get home.
BTW, remember all your units has to be consistent.

According to the Lexus website, it says the top speed in "143.7 mph." Now, if it were governed, don't you think they would chose a nice round number, like 144? It appears that it's drag limited.

Daniel, it would really help if you defined the variables...but the CD of the IS is .28 or .29 if that is of any help...

When you do the math, it is DEFINITELY aerodynamically limited to ~144 mph.

hmm... I read that it was drag limited @ 144mph. BUT, there were a few posts where someone had the car "dyno'd" and they claimed that it ran right up to 143-144. If this is the case, then it must be electronically limited. There's no wind resistance when you "dyno" a car, right??
Any ideas on this??

well, people can say it is drag limited because they see the rpm stopped before the redline, so they thought they have ran off the power. You are right, there is no aerodynamic drag applied to most dyno, so if the IS is able to go up to 144mph on a dyno, then it means it is electronically limited at that. There are only about 4 or 5 dynos I know in the world that can simulate a real life driving situations, and I highly doubt any of the consumer car manufacturers will use those to test their cars.

forget all that equation crap. I took in on the road and hit exactly 144mph, and then the car like gave me a halt.
and no it wasn't an open road.
NY state Thruway baby!!!

I hope the IS300 is putting more than 156 hp at the rear wheels, because that is quite low for 215 hp at the crank. :|

I've seen dyno sheets for a 323i, and it puts 152-155 hp at the wheels, while a 328i puts 167-170 hp at the wheels.

Are you sure about the IS300 numbers??? Even though the automatic sheds an extra 10% power loss, it should be putting close to 165-170 rwhp. Any way, just curious...

I hear ya.. I'm waiting for a chip that will override the governor.!!

Not that this proves anything, but for calculations like these I use a nifty little program called Car Test. From what I've found, it is actually pretty accurate in estimating 0-60 times and top speeds. It uses similar equations and finds the IS to be drag limited at 145 mph. I tend to agree with it, although I think webmaster owes it to us to take it to 144 and see if there's any punch left =). Interestingly enough, car test estimates 0-60 times of 6.6 or so, which would be more representative of a car with these numbers. I've always wondered if the transmission eats away power to make the car so smooth... even in power mode. Anyway, you can download car test from

here, it is 479k

I have the IS300 stored under "IS300" instead of "Lexus IS300". Apologies in advance for my laziness not to change it.

[This message has been edited by Nate (edited September 30, 2000).]

Also, the IS300 reaches that 144mph at 6000rpm not 6200 like the Top Speeds of the other gears.

Can everyone say "Electronically Governed"

Im sure the car would hit at Least 150mph
at "6200rpm" in 5th gear.

smra, even if the chip is removed it does not mean that it can hit 6200 rpm in 5th gear. the car may not have enough hp to do so.

I just tried the Car Test software. I changed a few parameters for the IS, including the weight (now is at 3400lb) and the launch rpm (1500rpm). I think these are more realistic numbers because you need to include the weight of a driver and most people do not power brake their car when they launch for 0-60mph.
The 0-60 time I got was 7.3, which is closer to what everyone claims right now.
I do have to say that all the numbers for other cars I have seen so far look a bit slower. It showed 2G Eclipse GSX goes from 0-60 in 7.1 sec, but I have in fact done 6.9s using G-Tech and many magazines have able to get somwhere between 6.5 to 7.0 times. Also, the Supra number is so of low, so maybe there is a parameter in there that is not optimized?

probably turbo boost