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Speed governer

11093 Views 86 Replies 45 Participants Last post by  ART
I just found out last night that I apparently have a speed governer on my car. Why give me 140 on my speedometer, when I can only go 120?
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[quote author=amru link=topic=71065.msg1338638#msg1338638 date=1176679328]
is this a speed governor or is it drag/power limited? and if it is indeed a governor.. any way to remove it? [no i didnt search]

Not really, it is an electronic speed governor that cuts fuel and spark. It is set for 117.5mph on the 3i and 3s. The only way to defeat it would be a stand alone ECU or finding a way to hack the existing one (or giving favors to a mazda dealership to use their ECU program tools to remove it aparently).

Who the heck really needs to go that fast on public roads though? Unless you race your car and also have the output pumped up a fair amount to actually manage speeds above that on a normal race track you don't need to defeat it.

My guess is the 3i and 3s hatch would be drag limited around 130-135mph and the 3s sedan around 135-140mph (the 3s hatch has much higher aero drag then the sedans do, even though it has higher engine output then the 3i...but its not by that much).
Not likely. Speedometers aren't exactly the most exact things on the planet. The ECU has a pretty correct speed reading (so long as at has been calibrated for the tires, supposing other then stock size have been installed), but the speedo might not show the correct speed.
Yes it is.

I have only pushed the car up there once or twice to 100+, but it wasn't hard to hit at all. No quick acceleration drop off or anything like that. The shift from 3rd to 4th around 90mph of course meant slower accel, but it stayed pretty steady up to about 100mph where I let off both times.
I doubt your friend really managed mid 160's. The earlier 5.7L 350hp corvettes had a top speed around 170mph...150hp less doesn't seem like it would manage 5mph or so slower.

I could see 140's on an RSX type-S, maybe 150, but 160's must have been downhill with a tailwind.

Yeah, with no speed limiter a mazda 3i or 3s should be able to hit low to mid 130's.
[quote author=aminzer link=topic=71065.msg1688845#msg1688845 date=1188933017]
nah you would run out of gear around 150mph

What does that have to do with it?

Our cars don't have enough power to hit 150mph without quite a few modifications. Technically at the fuel cut we could hit about 156mph in 5th gear...if we had the power, but we don't. They are drag limited to low to mid 130mph for both 2.0 and 2.3 models (the 2.3 sedan and hatch have a higher drag coefficient then the 2.0 sedan, due to different wheels and in the case of the hatch a different roof line, so the 2.3 sedan is only a bit faster and the hatch might actually have a lower top speed then the 2.0 sedan).
The limiter is set where it is on most American cars because of the tires that come with the car. In the case of a lot of manufacturers they are lazy (IE want to save money), so they'll set the limiter on ALL cars of a trim based on the tires that come with the base trim, even if the standard tires are higher speed rated on one of the upper trim levels.

In this case the base tires that come with the 3i are H rated, 124mph max (Toyo Proxie A17s). So 117.5mph limiter (to be more exact and to have a 'cushion'). This is why the Speed 3 comes with Y rated tires (186mph) and a 155mph limiter.

My response from the thread about removing the governor in the performance mods section, this is why the differing limiters and the lower one on the Mazda 3.
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