240 speed limiter

Hi everyone, this is my first post, but i've checked out these discussions many times. Thanks for all your advice and stories.
Anyway, my question is this. Does anyone know the best way to eliminate the top speed limiter in a 90 240. I've heard that disconencting the speed sensor wire from the tranny can have negative effects? anyone know. I've also heard rumors of cutting a wire to the computer (maybe from the computer) that allows you to maintain the speedometer (not very important, but nice), and still eliminate the speed limiter.

Any help would be great,
Thanks in advance

I also had this problem, I ended up sending the computer to Wolf tech computer# 619-442-0680. talk to Jim Wolf.

Thanks DPC, I've thought about that, but unfortunetely I am in kind of a time bind. Also, Jim's computers seem a bit steep at $600 for 10 horsepower, and no speedlimiter.

bb,

On the S14, you unplug the 5th gear speed sensor and the speedometer to disable the speed limiter. There is a rev limiter at 5500rpm in 5th gear or a certain speed (which I don't know what it is since my speedo has never worked). There are 2 plugs in the transmission, check your FSM to determine the correct plugs.

Hope that helps....

BB,

I've read (on several forums, and in one car magazine article) that there is a wire going into the ECU from the speedo that feeds the info on speed, and if you cut that wire you'll disable the speed limiter (it doesn't effect the rev limiter though). This method also has the advantage that it doesn't kill the speedo. The only place I've seen where the specific wire was discussed though was in reference to a later model 240 (on the 240SX.org website I think), so I doubt it would be the same for the '90. Also, I'm still waiting for my shop manual so I'm not sure if it's addressed there - but I'm guessing it is.

Regarding the Jim Wolfe ECU - you didn't say whether your 240 is a grocery getter or an ITA car, but if you're running (or building as I am) a car for racing, that $600 for another 10 hp doesn't seem too steep at all if it will get you that much closer to the front of the pack. Just MHO.

The car is an A car, but i'm taking it in strides. I do intend to get the computer, but I want to do a few other things first, mainly stop using junk-yard motors. Thanks for the input though, i'll try the shop manual and 240sx.org for more info. on the computer wire.

I believe you need to plan the ECU. While i've never tried it myself, I have been told that the factory ECU will allow 4 seconds of wide open throttle above 4,000 rpm without a signal from the speed sensor. Then the ECU shuts it down. There are other alternatives to Jim Wolf. Stillen does custom ECU mapping for these Nissans. I believe Sunbelt has someone doing some ECU work for them also.

If you need any other info, let me know.

Jim
ITA 240
#23

Quote:

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Originally posted by ITA240:
There are other alternatives to Jim Wolf. Stillen does custom ECU mapping for these Nissans. I believe Sunbelt has someone doing some ECU work for them also.

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JWT and JUN are the only worth considering. There are others who can do limited things with the Nissan ECU, but generally not much. One, JET, simply throws a sticker on a stock ECU. This ECU was checked out and it was found that NO code was changed from stock.

JUN is expensive as hell. JWT can almost always give you a dyno tested program for your ECU. Every JWT ECU is tested before it leaves.

Stillen buys their ECUs from JWT.


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George Roffe
Houston, TX

84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed

ITA 240, i'm not sure if you've allready covered this so i may need a little clarification. Does that 4 second interval apply no matter how the speed sensor is removed, whether it's from the tranny or by cutting the computer wire? Has anyone actually tried either of these methods to be sure whether it works or not? Second, what does the computer do if you exceed that parameter, shut down completely, impose a reve limiter?? And does that apply in all gears, or just fifth (I assume all gears because the car doesn't tell the difference between the forward gears does it?) Thanks for keeping this going, i'm going to the track tomorrow to test, but won't be able to go fast enough to tell at this track.

Stillen buys their ECUs from JWT.


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George Roffe
Houston, TX

....
I didn't know this. Adam at Stillen was one of my sources of information and he never revealed this. He is the one who told me aobut this 4 second thing. The way he explained it, the computer allows the 4 seconds for "diagnostic" type work. He said that the factory was woried that over four seconds and you would grenade the engine. He also indicated that it didn't matter where the signal was interrupted, the ECU would react the same way.

From what I undertand, your only options are to buy an ECU or run really short courses.

I would guess that if you were able to block every other pulse from the vehicle speed sensor, you would theoretically double the speed before the limiter kicked. I discussed this option with both Sven and Aaron back before the modified ECU's were legal. I was told that their interpretation of the rules would make modifying this signal illegal.


..Also, the ECU does know fourth and fifth gear. There are sensors on the transmission indicating each of those gears.



[This message has been edited by ITA240 (edited October 07, 2002).]

I have unplugged the 5th gear sensor and the speedometer on my S14. No rev limiter, no speed limiter.

It runs fine without them sending a signal to the ECU.
I think the two models share the same tranny?

The "snip" mod only works for the 16 valve cars. There's no way to fool the 12-valve ECUs. WE've tried everything including a potentiometer on the speedo signal.
JWT's ECU is the best $600 you can spend on the car, outside of actual seat time.
I spent almost an hour on the phone with the JWT programmer, and he told me everything Nissan does to cripple the car, and everything JWT does to keep it from happening.
Michael

Quote:

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Originally posted by handfulz28:
The "snip" mod only works for the 16 valve cars. There's no way to fool the 12-valve ECUs. WE've tried everything including a potentiometer on the speedo signal.

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We're working with a company that markets stuff under the "AutoTrans" name. It generates a speedo signal that is some percentage faster or slower than is really happening. Great for axle/trans swaps where things don't quite match up anymore. We of course are working with Ford type sensors (Hall and VRS, 1000 pulse per mile I believe.)

I'll get a contact at AutoTrans and post it here. It'll be way less than a $600 processor, like $120.

Edit:
This part won't be sold under the AutoTrans name, only Ford Racing. If the Nissan speed sensor is a Hall or VRS, it ought to do the trick.

[This message has been edited by tderonne (edited October 15, 2002).]

Thanks everyone for your advice. I ended up going to the race this weekend, and just living with bumping the speed limiter at the very end of the straights. Real bummer. A JWT computer is tops of the list for stuff over the winter.

The rheostat won't work because pulses are counted instead of voltage generated. Some cars send the signal to the ecu after passing it through the speedo. It is possible that a vehicle speed sensor from another nissan has the proper value to skew the brain's perception in the direction you want.
I wonder if there is a rear drive nissan vehicle that uses a higher ratio rear end. Maybe a 4wd truck.

Tweo other options...Nissan sells different drive gears for the speedo sensor...this would slow the pulses down...I have been told that this would not be a legal mod (Aaron in Denver) I would never protest you for it though. I don't understand the reasoning here other than the GCR doesn't specifically allow you to change the gear...

Another option...much less than the JWT ECU...Call Keith Goldin..305-275-0365...He has been messing with a few ECU's and told me last weekend that he has been able to move the RPM limit and remove the speed limiter on these cars..

hope this helps..

Jim