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Old 01-18-2018, 06:37 PM   #11 (permalink)
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Quote:
Originally Posted by cRiPpLe_rOoStEr View Post
That would be more of a problem if the only input for the speed limiter was engine RPM. Well, even though a lower top speed may eventually become a problem to merge with the traffic in some expressways, depending on how the speed limiter is tuned would still enable the cut-off limit to vary according to the gear selected (a similar setup had been used in some 50cc motorcycles in my country in order to enable them to be registered as mopeds).
The only speed limiter I have had experience with is a block of wood under the gas pedal. Didn't know it was there until after I pulled onto a busy 2 lane highway... I had some not-so-kind words for the owner.

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Old 01-18-2018, 06:46 PM   #12 (permalink)
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The thing is that I'm used to driving my 1985 VW non-turbo diesel. Basically you floor it and wait 80 seconds to reach 55mph on flat ground. The Leaf I own has an ECO button that lowers the pedal response. But after driving my mom's Chevy Sonic I'm not too fond of the speeding up the car can do with such little pedal pressure. Of course her car doesn't have cruise control so that doesn't help.
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Old 01-18-2018, 06:53 PM   #13 (permalink)
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I think the onramp argument is a straw man. If it is an on ramp, you will get up to a reasonable speed that allows a merge. You certainly will always be faster than a loaded tractor trailer doing the same thing, and they need 100'+ of space. If it's just a little turn onto a fast highway then you need to wait until it is clear even if you have a Tesla S in ludicrous mode.
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Old 01-18-2018, 08:30 PM   #14 (permalink)
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No add-on *electronic* module will work correctly with modern software, unless you made a module that intercepted the throttle pedal signal.

Most throttle pedals have two potentiometers in them, that are opposite in effect (one goes, say, 0-5v with increasing load, the other goes 5-0v with increasing load). As long as both signals add up to 5v the signal is valid and the pedal is deemed not faulty.

To fool this in the least intrustive way you would need to know the required throttle to maintain the speed, and use something like an arduino to switch in both fake pedal signals while over speed and over this throttle position. This would close the throttle *to the correct amount to maintain speed* (as opposed to completely) when at and over speed, while still allowing torque to be controlled to lower levels. It would, however, have a fault if for some reason, like a headwind/tailwind/trailer/hill in that it would still allow overspeed if the power requirement was lower or pulse around the limiter if it was higher.

Your best bet is to access the factory PCM and change the limiter settings, as nowadays they automatically close the throttle if you approach the limit slowly and the transition to 'limited' would be smooth and accurate. If you do this, the chances are that you then have access to auto trans tuning too, which is a powerful economy tool
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Old 01-18-2018, 09:55 PM   #15 (permalink)
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Best way I have found to limit speeding is by not being late before I leave the house. If you didn't feel rushed, you won't think you need to drive faster to make up lost time.

Any computer flash can set a governor, popular brands are HPTuners and SCT and COBB accessport. Some companies encrypt and lock their ECM, HPT and SCT have been tuning GM and Fords for years. If this is actually something you'd want to do to the car find a speed shop in the area and ask what cars they can and can't tune and limit your search to those they can tune. I picked up HPT on Craigslist for a good price which enables you to tune the computer from a laptop. Pretty sure SCT and COBB are mail-order type tuners.

The best situation here is a "valet" key. A lot of keys in modern cars have RF transponders for anti theft protection. If the computer can recognize different keys, 1 can be the slow key and another the regular key...I believe the hellcat or demon have this feature along with other hi performance cars.
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Old 01-18-2018, 10:29 PM   #16 (permalink)
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Quote:
Originally Posted by Hersbird View Post
I think the onramp argument is a straw man. If it is an on ramp, you will get up to a reasonable speed that allows a merge. You certainly will always be faster than a loaded tractor trailer doing the same thing, and they need 100'+ of space. If it's just a little turn onto a fast highway then you need to wait until it is clear even if you have a Tesla S in ludicrous mode.
And I also live hundreds of miles of any modern freeway or onramps. Where I live is very rural, where it's common to get behind farm tractors or even herds of cattle being driving down the highway. And after driving school bus for several years that also had a limited speed I'm used to pulling over every once in a while if I get a line of cars behind me.

PS. As of today I'm leaning towards trading in all three cars for a Prius Prime because of the tax credits. About $4500 federal and $5000 state. That knocks the price down to close to that of a new Honda Fit or Toyota Yaris.
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Old 01-19-2018, 12:04 AM   #17 (permalink)
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If it hasn't been pointed out...if you prevent the gas pedal going down all the way, I doubt your engine will ever be able to hit peak efficiency. In theory, you want to floor it (at least up until just before fuel enrichment kicks in) to get up to speed most efficiently.
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Old 01-19-2018, 01:16 AM   #18 (permalink)
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Quote:
Originally Posted by Hersbird View Post
I think the onramp argument is a straw man. If it is an on ramp, you will get up to a reasonable speed that allows a merge. You certainly will always be faster than a loaded tractor trailer doing the same thing, and they need 100'+ of space. If it's just a little turn onto a fast highway then you need to wait until it is clear even if you have a Tesla S in ludicrous mode.
There was a guy on one of our sites a few years back who INSISTED that anything slower than his car was dangerous to take up his local on-ramp.

As he drove a Subaru STI, which does zero to the legal limit in about five seconds flat, it was fun asking him how many of his neighbors had died taking that very ramp.
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Old 01-19-2018, 02:19 AM   #19 (permalink)
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Quote:
Originally Posted by Stubby79 View Post
If it hasn't been pointed out...if you prevent the gas pedal going down all the way, I doubt your engine will ever be able to hit peak efficiency. In theory, you want to floor it (at least up until just before fuel enrichment kicks in) to get up to speed most efficiently.
Very good point. And easily done with a manual transmission. Or as BLSTIC pointed out:

Quote:
Originally Posted by BLSTIC View Post
Your best bet is to access the factory PCM and change the limiter settings, as nowadays they automatically close the throttle if you approach the limit slowly and the transition to 'limited' would be smooth and accurate. If you do this, the chances are that you then have access to auto trans tuning too, which is a powerful economy tool
In other words, if the engine could be set to hit nearly full throttle, right before it enriches, and the transmission set to keep RPM's down, that would be the best efficiency mod as far as all that goes.

But the other point was to limit top speed, although that is perhaps easier to do with pure will power and a cruise control system. For an example, all summer I was traveling once a week to the next town 65 miles away in my Nissan Leaf. On the way there it wasn't bad with the 2,000ft drop, but on the way back I had to limp along at 35mph to make it back up those 2,000ft. I'm just afraid that if I trade my Leaf for something with a longer range I'll be tempted to go much faster. Not that I want to go 35mph everywhere but 55mph seems like a good limit for where I live. Less wear and tear and better fuel mileage.
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Old 01-19-2018, 11:31 AM   #20 (permalink)
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Quote:
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But the other point was to limit top speed, although that is perhaps easier to do with pure will power and a cruise control system.
It may be the easiest approach if the vehicle is driven by only one person who's committed to that approach. Not the case with most commercial vehicles that get their ECMs reflashed in order to limit speed, usually operated by multiple drivers (plus there are those who are simply careless when driving a vehicle they don't actually own).

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