A speed limiter... on an LS?

97stscaddy

97stscaddy

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Was F'in around on the interstate tonight, being stupid, and wanted to see how fast I could go in the LS. (I wanted to go fast! :p )

It pulled hard right up to 120 then just quit. And I wasn't even close to shifting to 5th yet! Still had another ~1500 rpms to go. So I slowed down to 110 or so and tried again, same thing. Hit 120 and just would not go any faster. It was fun, but I was disappointed. I expected at least 130.
 
if he has aftermarket wheels with a different diameter, he could've been going 133, and his speedometer might not be recalibrated.
 
ground_zero298 said:
Why did his cut out at 120 then?
Click to expand...

I can't say for sure since I was not with him.

It could be a number of things...

aftermarket wheels as pektel mentioned,
terrain,
atmospheric conditions,
vehicle conditinos,
poor fuel,
someone set a new speed limiter using the x-cal,
aliens :D

I do know that even the v6 LS will go ~130 mph (indicated)
 
Last I checked my wheels are factory. And tires are stock 235 50 17 size.

Think my speedometer could be off by 13mph at that speed? :p

I dunno what the deal was, perfectly straight and flat stretch of interstate, mid to upper 30s outside temperature, been running premium since the day I got it.

I have noticed some slight hesitation the last few weeks or so on kick-downs and hard acceleration from stop. Maybe this could be related?
 
condition of injectors/fuel filter/fuel pump maybe? i'm just taking a wild guess here...
 
Plus even if his tire size is off, I don't think the limiter would "know" that.
 
Ah, good point. Funny. If this is true, bigger wheels/tires can make your car faster (higher top speed)!
 
cars do not get governed to a certain speed. They get limited to the RPM in top gear or wind resistance. Having bigger tires will not make you get a faster top end.
 
02V8Sport said:
cars do not get governed to a certain speed. They get limited to the RPM in top gear or wind resistance. Having bigger tires will not make you get a faster top end.
Click to expand...

hummm that makes sense I guess. But couldn't the LS be governed to a set speed since everything from the throttle to the fuel injectors is controlled by the computer?

If as you indicate it is limited by RPM in top gear his vehicle accelerated up to a certain point and stopped at the preset RPM in the top gear. This would normally produce a velocity of ~130 mph but on his car it only produced 120 mph. This would indicate that his car is not producing the factory spec power and therefore could not overcome the wind resistance above 120 mph.
 
n8bachelor said:
If as you indicate it is limited by RPM in top gear his vehicle accelerated up to a certain point and stopped at the preset RPM in the top gear. This would normally produce a velocity of ~130 mph but on his car it only produced 120 mph. This would indicate that his car is not producing the factory spec power and therefore could not overcome the wind resistance above 120 mph.
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But he didn't shift into 5th! So maybe it limited him there in 4th for some reason but would have let him go faster to some rpm limit if he went into top gear.
 
97 - Did you have the pedal to the floor both times?

If this trans is like most, it won't allow you into overdrive at wide open throttle.

Just a guess here.
 
As for all the Nubbie Questions, It seemd that more people will gettin on to the web site becasue more of the LS's are coming out of lease or going to sesound Owners now. So we will be seeing more questions being asked until they get the hang of the message boards and the search engine.
 
pektel said:
if he has aftermarket wheels with a different diameter, he could've been going 133, and his speedometer might not be recalibrated.
Click to expand...

I can't resist... So if his speedo isn't re-calibrated, how is it his car would know he was going 133 and kick in the speed limiter? Also by my estimation, that would make for an almost 10% larger tire... meaning if the standard tire height is 24", he would have about 26.5" tires... that would be a bit big...

Anyway, the speedo is going to show how fast the car thinks you're going. There for if he was going to have a speed limiter kick in as factory set, it should have been at 133mph on his speedo. Doesn't matter if he was actually doing 160, or 60.

I assume you just confused yourself on that one
 
Nah, it's all the figures involved that confuses me. I remember awhile back where someone said that it was a "percentage" difference when going to a different diameter tire. so the speedo would be off less at low speeds, and off by more at high speeds. I'm not experienced when it comes to the actual physics of it. I was just guessing based on the concept, not on the actual figures...
 
02V8Sport said:
cars do not get governed to a certain speed. They get limited to the RPM in top gear or wind resistance. Having bigger tires will not make you get a faster top end.
Click to expand...


Entirely not true. There are two types of limiters, and most modern cars have both... a rev limiter (so idiots don't over rev their car) and a speed limiter. The two are totally separate from each other. If this were not the case, mustang owners who's car comes from the factory with a 3.03 (or something along those lines) ratio and bump up to a 4.10 would effectively have their speed limited dropped down by around 1000 RPMs (because your RPMs at speed in overdrive would increase by nearly 1000 RPM's. There for bringing on the "RPM induced speed limiter" a full 1000 RPM early... which would be something along the lines of what... 75-80mph??)

My 98 F-150 is factory limited to 94mph... before I changed my axle ratio's I was running 33" tires (factory are about 28-29), I assure you... my limiter was still at 94mph. But remember that I am still turning my axles and tires at the same rate... there for because the tires have a larger circumference... the radar said around 105ish. Your statement kind of contrdicted itself.

As for the first part, a friend of mine's mustang is a prime example... as I explained to you his exact case. His car had something like 2.98 gears in it, he installed 3.73's, then later 4.10's; top speed unaffected. It goes by the speed of the vehicle, not the RPM's in top gear.
 
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