Factory Speed Limiter

[nikp]

I had what i thought was a fuelling issue at high speed on my FD - I think i\'ve figured out what the issue is: I think it\'s the mazda factory speed limiter! It makes sense cos i hit it in only fifth gear whether i\'m on full boost or partial throttle, etc. (Obviously this is all done in the confines of a private test track!  :3gears-rh ).

So, my question is, how do i remove this \'feature\'? I used to have a speed converter to convert from kph to mph which i understand removes this. But i now have a speedo in mph, so no longer use the speedo converter.

[Adriansturgess]

As I understand it jap imports are speed limited to approx 112mph (law in Japan). Fuel supply is momentarily cut at this speed and it has nothing to do with what gear you are in or how much boost.

[nikp]

Yeah - that\'s how i understand it too (It\'s pretty much exactly whats happening)

My question is how do i disable it!? I know it\'s disabled when an after market speed converter is fitted. I think there\'s some sort of feed to the ECU isn\'t there?

[Adriansturgess]

I had same problem and got Rotechniks to remove it while the car was in for service. Don\'t know what they did or how easy it would be to do yourself. Forget what they charged me but I think it was around the £100 mark.

[WeasleRx7]

When my speedo convertor wasn\'t working, one of the guys at RX Motors offered to remove the limiter for me.  

I was told it was just a single wire that goes to the ECU and it just needs snipping. 2 minute job including removing and replacing the trim.  They had even located the wire and were just ready to snip it!  I opted just to remove my converter and get it replaced.

Unfortunately I didn\'t look as to the colours of the wire, but I did see that it was just a single wire going to my ECU.  Maybe one of the tuners here can tell you which one it is.  I can only tell you it\'s possible (sorry).

[WeasleRx7]

Just had a look at my ECU, and the cable is still separated from the loom.

It\'s on the 2nd multiplug from the bottom and is green with a black stripe.
(EDIT)** Not the right cable, please see later posts **(EDIT)

If no one else can confirm this is the correct cable, maybe just remove that one cable from the muliplug and give it a try?!  

Small print:  Due to the fact that I am no expert, or in anyway qualified to offer advice, any changes made will be at your own risk!!

But what\'s the worst that could happen??

[nikp]

Cheers - i\'ll check it out. Although, I\'m going to work from behind the dash i think. I\'ve had that apart numerous times now, so i am familiar with the cables back there. I also know which ones have been snipped for the speed converter, so i shall just look for a green wire with black stripe. Might not tie up completely, but it\'ll be worth a look. Cheers for the input: i knew it was a single wire.

[WeasleRx7]

If you want to try snipping that cable, trust me, it\'s much easier to do it at the ECU.

Just remove the one trim panel on the left of the passengers footwell (the one that holds your emergency flare if you have one), and hey presto ECU is there and cables are all in full view!

I\'ve also had my dash off a number of times, and this is much much quicker.  Also if it doesn\'t work for some reason, you dont need to strip the dash to re-connect it.  I\'ll take a pic.....

[WeasleRx7]

I seem to recall this cable does come from the speedo loom behind the dash, but here\'s a pic of the location of the ECU anyway.

[nikp]

Cheers - nice one! Is the ecu in the passenger footwell?

[WeasleRx7]

Yes mate, as per photo ^^^^

But as I said before, this cable wasn\'t singled out by myself so I can\'t confirm either way it\'s the right one.  Having said that though I\'ve not had the trim covering the ECU off since I had the problem, so I\'m sure it\'s the same cable!

Just be ready to reconnect it if the limiter isn\'t disabled.

[nikp]

Righto! Cheers - i\'ll check it out.

[TonyBlair]

I\'m confused...

when my car arrived from the land of the rising sun it had a HKS Speed Limit Defencer. It\'s a little device that was wired into back the ECU. I looked about on the net and it seems the sole purpose of this "Speed Limite Defencer" was simply to cancel out the speed limiter.

I can\'t see why HKS would bother making such a device if all you really need to do is cut a wire? Anyhow, not too bothered about it since I have a Apexi ECU now - which boviously doesn\'t have a speed limiter built-in  

Cheers
Jon

[WeasleRx7]

I don\'t know the answer to that one Jon, but hopefully Nikp will report back to us with his findings...?

[nikp]

I haven\'t done it yet, but as far as i understood, it was a single wire going to the ecu was all that there was that controls the speed limiter. My question was which one was it, and what do i need to do.


As found on the ebay auction for the speedo converter:
"There is also a special wire on the unit which goes to the E.C.U which will remove the 112MPH Restriction"
(http://cgi.ebay.co.uk/MAZDA-RX7-SPEEDO-CONVERTER-DELIMITER-CHIP_W0QQitemZ4566697961QQcategoryZ52640QQssPageNameZWDVWQQrdZ1QQcmdZViewItem)