Need IDEAS for 6-speed conversion Reverse LO Problem

[NSX_PDX]

I have a 91 w/ a 6 speed transmission. The problem is that the previous owner did not care to address the reverse lock out (RLO) problem on the car.

The stock car engages the RLO at 19 mph. The late model cars have a lead from the ECU that triggers this action. The solenoid for RLO is built into the trans.

My problem... how to work around this without paying the 600.00 for a relay from CT!

Solution 1) Thank you M Basch! - Hook up a relay to the Brake pedal Sending unit.

Ok, but how would this effect the duty cycle of the solenoid. Reverse would engage every time the brake is depressed!

Solution 2) Wire in a switch - Hold down for reverse. OK, but kind of tacky...

Solution 3) fork out the dough for the CT Part... Not recommended by girlfriend so close to Valentine's Day... Valentine's, did I mention I need a new radar detector... Oops, I'm in trouble...

Any novel ideas would be helpful.

B

 

[grippgoat]

There was an email from Brian Zublin explaining how a smartshift *may* be adaptable, with instructions on how to hook it up and see what happens. I'm willing to bet a motivated buyer could probably prod him for a little more support.

If it were my car, I'd probably just leave it without the lockout, or put in a switch and drive it until I got sick of it, and then find another solution.

-Mike

[This message has been edited by grippgoat (edited 06 February 2002).]

 

[Lud]

1) Aren't you usually going to be on the brakes in a situation where you are most likely to botch a shift and accidently put it into reverse?

2) Cheap but effective

3) The best existing solution

 

[NSX_PDX]

The Smartshift would work by rpm count. The problem is the same as the brake pedal. It will engage/disengage every time a certain rpm count is crossed. Further, a low rpm shift into reverse would be possible.

Thanks for the input LUD. Did you see my post on the stereo install?

 

[grippgoat]

Actually, the smartshift idea bryan outlined was to work off the speedometer signal instead of the tach. The only question was going to be whether signal was in the right range. And if it wasn't, he said he could burn a different chip.

Lud: I think his concern with the brake pedal relay solution was all the times you used the brakes and had no desire at all to go into reverse, causing un-needed wear on the solenoid.

-Mike

 

[grippgoat]

Here's the email Bryan sent.

I missed some of this thread on the NSX list, but I will jump in here and
add my comments.

I think that the SmartShift unit ($50) will work for the reverse lock-out
electronics:

Connect RED wire (power) to +12V (ON when key in RUN position).
Connect BLACK wire (ground) to chassis ground.
Connect GREEN wire (tachmoeter) to the speedometer signal.
Connect YELLOW wire (output) to one wire of the lockout solenoid.
Connect the other wire of the solenoid to +12V. If the solenoid has an
internal diode, then polarity WILL matter, and we will have to determine
how the diode is connected in the solenoid before it is connected,
otherwise it could be damaged.

Configure the SmartShift for 4000 RPM (the lowest setting), 4 cylinders,
and "Steady mode" for the output. 4000 RPM for a 4 clyinder is 133
Hz. When the speedometer signal exceeds 133 Hz, the SmartShift will ground
its output wire (YELLOW) to energize the solenoid.

The big question is: what vehicle speed corresponds to 133 Hz? The only
way to know is to test it, or maybe the freq. vs. speed relationship is
already documented in the manual. If the speed is too high for the
lock-out engagement, then I can program a new chip for the SmartShift to
lower the speed. At what speed does the stock NSX and/or Comptech box
engage the lock-out?

General installation instructions for the SmartShift are at: http://www.zublin.com/smrtshft/900010/900010.PDF

I will be out of the country until 24-Jan.

Regards,
Bryan Zublin

 

[BryanZublin]

I think my comments about using the SmartShift for the reverse lockout are still valid. The only change that I would make to my previous post would be to put a relay between the SmartShift output and the solenoid. This will guarantee that the current rating of the SmartShift output is not exceeded (it's conservatively rated at 2 amps max). The relay should have a contact rating of at least 10 amps.

So, here are the updated installation instructions:

Connect SmartShift RED wire (power) to +12V (ON when key in RUN position).
Connect SmartShift BLACK wire (ground) to chassis ground.
Connect SmartShift GREEN wire (tachmoeter) to the speedometer signal.
Connect SmartShift YELLOW wire (output) to one lead of the relay coil.
Connect the other side of the relay coil to +12V.
Procure a 1N4001 diode (Radio Shack 276-1101) and connect the anode of the diode to the YELLOW wire. Connect the cathode of the diode to the relay coil that is connected to +12V. This diode will prevent the "inductive kick" of the relay coil from damaging the SmartShift when the relay is de-enerigized.

Connect the relay contacts in series with the lock-out solenoid, +12V and chassis ground.

Configure the SmartShift for 4000 RPM (the lowest setting), 4 cylinders, and "Steady mode" for the output. 4000 RPM for a 4 cylinder is 133 Hz. When the speedometer signal exceeds 133 Hz, the SmartShift will ground its output wire (YELLOW) to energize the relay.

The big question is: what vehicle speed corresponds to 133 Hz? The only way to know is to test it, or maybe the freq. vs. speed relationship is already documented in the manual. If the speed is too high for the lock-out engagement, then I can program a new chip for the SmartShift to lower the speed.

General installation instructions for the SmartShift are at: http://www.zublin.com/smrtshft/900010/900010.PDF

Bryan Zublin


------------------
Zublin Engineering
http://www.zublin.com

 

[Lud]

Originally posted by grippgoat:
Lud: I think his concern with the brake pedal relay solution was all the times you used the brakes and had no desire at all to go into reverse, causing un-needed wear on the solenoid.
-Mike

I understand that concern but I don't think it is the important one. The duty cycle on a solenoid like that is through the roof.

My concern is that wiring it up that way does not achieve the intended protection, because I think you are usually on the brakes when you are most likely to botch a downshift and put it into R while going forward at a high rate of speed.

I like Bryan's SmartShift mod. If someone works gets it tested and working, that would be a good solution for a lot less $. Document it all and I'll put it in the FAQ!

 

[NSX_PDX]

I am placing an order for the S Shift today and I would be happy to document the install.

BZ - Thank you for the additional input. I misunderstood the original config and thought the S Shift would monitor RPM, not speed.

I will reply to this thread as soon as the fix is installed and tested. In the interim - I installed a switch / relay.

B

 

[grippgoat]

Originally posted by NSX_PDX:
BZ - Thank you for the additional input. I misunderstood the original config and thought the S Shift would monitor RPM, not speed.

Just to make sure... I have no idea if BZ actually reads this thread. If you want him to see feedback or answer questions, you'll probably want to email him directly.

-Mike

 

[BryanZublin]

Actually, I have been reading the Forum a lot lately. I'm stuck in New Jersey this week with nothing to do.

Let me know when you get close to installing it and we can discuss the details.

Bryan Zublin

------------------
Zublin Engineering
http://www.zublin.com