Logic Overdrive Devices

[Dannyb]

I was looking at the Revington TR device and if it was worth it on a 1500 o/d Spit.  I know 3rd od is almost the same as 4 gear butt 2nd gear and 2nd od may be worth it. I wonder how it let's od in on 2nd gear but still blocks 1st gear as the inhibitor switch on the box blocks both gears. 

I understand the TRs  have a better spread of ratio's. 

Anyone had any experience of these. 

Danny

[Clive]

Possible not worthwhile on a spitfire. 

The tr box, (same ax saloon and sprint) drop out of overdrive between 3rd and 4th, I have done that often enough, and it can crunch. That would be a big advantage of a logic controller. Likewise, 2nd od is not easy to achieve with a spitfire (I won't say impossible, but much much harder than the big boxes)

[Martins Stag]

I agree with Clive on there there are better things to spend your money on...

[Dannyb]

8 minutes ago, Martins Stag said:

I agree with Clive on there there are better things to spend your money on...

Yeah I agree. Sometimes I get these urges come over me... What to mess around with next. 

Danny

[yorkshire_spam]

I did think climbing some of the passes on the 10CR a 2+OD would have been handy, so I looked at swapping to a P-type (better able to handle the torque than the J from what I understand) and re-arranging the interlock so that OD was prevented on 1+R not 1+2+R, but after a while the expense and hassle didn't seem worth it for the really rare occasion where it'd be useful. 

[sparky_spit]

I'm with Yorkshire Spam on the desirability of having O/D on 2nd just for the passes, especially the bit where you exit an upwards hairpin bend in 2nd and then have to rev the nuts of it to catch 3rd with enough speed/revs to not bog down. 

Dirk Devogoleir (spelling...) posted some years ago about how how he did this on his Mk3 Spit and it was relatively straightforward. it must still be on here somewhere, with the parts list and diagram? I think that all you lose is the automatic switching on of the reversing lights, which is a small price to pay.

Its been on my to-do list for years.

[RobPearce]

11 minutes ago, sparky_spit said:

I think that all you lose is the automatic switching on of the reversing lights,

I see no reason why you should lose that. When we modified my brother's Mk2 Spitfire for 2nd OD - using the existing D-type unit because the torque it handles in 3rd on a GT6 Mk2 exceeds the torque of a Mk2 Spitfire in 2nd - we didn't interfere with the reverse light circuit at all. It just needed an extra bracket to hold a third switch in a very particular position, using the arm that would operate the reverse light switch had the factory not moved it to the top cover plate for commonality with non-OD cars. But even if your reverse light switch was at the front, it's not where you'd put the 2nd gear one and wouldn't prevent our mod.

[Batch]

Danny

I cannot comment on having a logic box fitted to spitfires, but having recently had one fitted on my TR4 is brilliant. It gives you easy access to a seven speed gearbox, gone is the need to remember to drop out of overdrive before changing up. If you do go down this route you need to change/modify your on/off switch to a momentary one.

Dave

[yorkshire_spam]

4 hours ago, sparky_spit said:

I'm with Yorkshire Spam on the desirability of having O/D on 2nd just for the passes, especially the bit where you exit an upwards hairpin bend in 2nd and then have to rev the nuts of it to catch 3rd with enough speed/revs to not bog down. 

Catch 3rd... so that a few seconds later you can cog it back down to 2nd (which on my box needs a double de-clutch) and then repeat the whole palaver over again for the next hairpin! 🙂 We love it really.

 

[Nick Jones]

Extensive discussion of the subject here.

https://sideways-technologies.co.uk/forums/index.php?/topic/9456-overdrive-in-2nd-gear-and-logic-switching-moved-from-miss-fire-over-4000-rpm/

Even a pic of the mods needed on a Spit 1500 box for the extra inhibitor switch.

 

[Hogie]

Hi Folks,

the OD logic box can be fun to use but you really do need to understand why you want one.

The original one (Revington) was designed for the racing brigade for the quick gear changes - both up and down.  This is not required for the touring car.

Along with the expense you also have added complexity that could bite you  in the bum.

My one works very well and I am happy with it. But !!!!  you do need a momentary ON switch to power it and then placed in the correct position.  Not always easy.

 

Roger

[PeteStupps]

@Dannyb when I fitted overdrive last year (3 rail Spit) I boldly enabled it on all forward gears. On RBRR I used OD 2nd a couple of times and it was useful, but very much only needed on steep inclines. Or perhaps when following awkwardly slow vehicles up moderate inclines. Tried using it at Mallory Park trackday last month but it didn't really add much.

My long term to-do list includes modifying the control circuit so dipping the clutch drops OD out, but doubt i'll ever get round to it!

[WIMPUS]

You can weld a piece on the cog that presses on the switch inside the box (on a single rail).

Then you can have 2nd OD to.

 

A friend of mine has a very early TR6 with OD on 2nd, 3th and 4th.

This was original, sadly the OD is dead 😅

 

 

Edited July 21, 2022 by WIMPUS

[Gt6s]

2nd OD eats the shit out of the OD clutch EXPENSIVE !

[Hogie]

On 26/07/2022 at 21:08, Gt6s said:

2nd OD eats the shit out of the OD clutch EXPENSIVE !

+1

 

Roger