Speed limiter removal causes gearbox death - fact or fiction?

[elnevio]

Well, I've had a few minor issues with Newera Imports, but have eventually received a response to these.

One of them, however, was that although the speedo and odo were converted to mph and miles respectively, the 180kmh speed limiter hadn't been removed. The response is a belter, and is as follows:

"Also spoke with Gareth regarding the speed limit restrictor. The way a UK conversion chip works to show MPH instead of KM/H is to divide the signal pulses going into the speedometer by a factor of 1.6. On a Legnum VR-4 the the gearbox feeds the speed signal to the ECU, which in turn cuts power at around 180 km/h (As with all japanese spec cars).
An auto gearbox should not receive a speedometer conversion as otherwise it can "think" the car's doing km/h when in fact it's doing mph.... This is dfangerous & could cause gearbox failure eventually. I've heard of FTO's having gearbox failures because of speed signal conversions to gearbox signals, when carried out by other garages. Gareth has correctly not converted the signal for the gearbox for this reason. It means the car is restricted to 180 km/h as it came from the Mitsubishi factory - but the gearbox's safety isn't compromised."

So, fact or fiction? I'm firmly in the BS camp on this one...

[bradc]

the VR-4 auto gearbox changes up and down at predefined points.

IE you can change into 3rd at about 15kmh, 4th at about 30kmh and 5th and 60kmh. It then changes down out of 5th at 50kmh and so on.

I think what they are saying is that the gearbox will change to 15mph, 30mph, and 60mph. However I don't beleive this is the case, I've never heard of a UK member mentioning it.

The other option is that torque converters have problems lubricating themselves at high rpm. The common limit is said to be 7000rpm. Perhaps they are thinking that sustained operation at speeds above 180kmh at high rpm might cause problems for the gearbox life.

[elnevio]

the VR-4 auto gearbox changes up and down at predefined points.

IE you can change into 3rd at about 15kmh, 4th at about 30kmh and 5th and 60kmh. It then changes down out of 5th at 50kmh and so on.

I think what they are saying is that the gearbox will change to 15mph, 30mph, and 60mph. However I don't beleive this is the case, I've never heard of a UK member mentioning it.

The other option is that torque converters have problems lubricating themselves at high rpm. The common limit is said to be 7000rpm. Perhaps they are thinking that sustained operation at speeds above 180kmh at high rpm might cause problems for the gearbox life.
Yep, my gearbox changes pretty much at those kmh points, i.e. 3rd at about 10mph, 4th at about 20mph, and 5th at about 38/39mph.

So the gearbox is still operating as it should, but the limiter is ECU-based, is it not, and only cuts back on the engine power, i.e. nothing to do with the gearbox. I find it hard to believe that removing the limiter could cause such fatal issues. I notice that BeastLee has been chewing through his gearboxes...

[bradc]

wouldn't worry too much then!

[Beastlee]

I haven't chewed through anything ;), all I needed was a top-up and considering the car is due an ATF and AYC fluid change in September I don't think that's bad. I also believe mine had an issue with electrical Gremlins as it still didn't cure the fault until I did an ECU reset. The car is back to normal now just shifting a little lumpy whilst it relearns.
I've done a few long runs at 100+ and almost every day it goes up to 130-140 without any noticeable problems or excessive heat build up. I can't see how it would have too many issues as the gearbox and ECU both definitely still see km/h on the signal wire. I cut my feed to the ECU but the car still shifts gear at the expected km/h points which indicates to me that the gearbox still knows exactly what speed it's doing. In fact Evoscan also reports the km/h speeds accurately when logging, as does my Profec which is directly connected to the speed signal wire.
If there's anything else I can do to help give a definitive answer please ask. Any requests for sustained 120mph+ driving will be responded to with a request for cash..../rally ;)

[elnevio]

Lol, didn't think you had any probs!

So it's purely the speed signal wire to the ECU that needs cutting (i.e. I don't need another convertor)?

[bradc]

just up the boost and max it out :) I want 180mph

[elnevio]

Could do that!

Just need to find a local Veyron owner willing to let me slip-stream 'em.

No wait. I'd need something a bit taller...

[bradc]

Cayenne Turbo?

[Beastlee]

I was almost to the limiter in 4th and hit 229km/h(142mph) which was confirmed on the SatNav I assume I could get some more from 5th but I don't know how much... Bear in mind the distance to this point from the slip road is just on 1km and I was rolling from about 50km/h(30mph) onto the autobahn.
If I had started a junction further back I reckon I could max it out as the acceleration would be on the curved part of the road and the top end would then be on the straight and is quite a long run. The previous slip is about 1.5km back from my usual one so I reckon 2.5km is plenty of space to run it up...with a faster entry speed too ;)

[Davezj]

i have removed the limiter on my VR4 by just cutting the wire from the A/T ECU and the Engine ECU. i have not had a chance to test the limit on a track/autoban yet but there is no difference in the autobax behavior.

[The Vee]

Hmmmm interesting. My knowledge is not good on the auto/tip versions, but I was under the impression that the gearbox worked on revs which just equates to a road speed regardless of whether the speed is shown in MPH or KMH.

[elnevio]

Hmmmm interesting. My knowledge is not good on the auto/tip versions, but I was under the impression that the gearbox worked on revs which just equates to a road speed regardless of whether the speed is shown in MPH or KMH.
Exactly! Precisely my thoughts. The gearbox doesn't give a monkey's about speed, just revs!

[Nick Mann]

I have had a dash convertor, a gearbox convertor and none at all. I have never noticed a difference in the auto boxes behaviour. In which case, I would have to say it is a load of old cobblers.

As to extended periods of high revs, is a limited 112 and a bit mph low revs? When would you cruise at that speed in the UK? So, I still say it is a load of old cobblers!!!

[Beastlee]

You don't have to be at high speed to be at high revs......

[Turbo_Steve]

I call cobblers.

In fact, removing the speed limiter is more likely to lead to engine problems than Gearbox (which is connected to the wheels...why would it need a speed sensor when it is connected to the wheels? ) as sustained high speeds in some cars result in a richening of the map to keep things running a little cooler.

[elnevio]

Well, I've done the ECU wire cut - and my fingertips feel like they've been sandpapered off, due to the 40 minutes of trying to unplug the ECU plugs - dammit that was fiddly!

But it's done and I haven't killed the gearbox on my little test run down my private test track...

Anyway - I'm a happy boy. :afro: But I DEFINITELY need the brake upgrade NOW!! /Hissy

[bradc]

so the stock brakes don't do so well from 150mph? :)

[elnevio]

so the stock brakes don't do so well from 150mph? :)
Judder-tastic!

[Beastlee]

Brad, I think mine are now so warped they make the front of the car wobble slightly when driving!
Problem is they're only a year old and have less than 10000miles on them so hardly any wear. I'm considering what discs to replace them with but it depends on what is available over here as shipping discs from the UK would be a bad idea.

[Davezj]

I can tell you for fact (i have measured it) that the signal going between the ECU's is a frequncy dependant signal. Pulses tansmitted down the wire and as the car goes quicker the more pulses are transmitted, increasing the frequency.

as i say i have not noticed any difference in the cars behavior since snipping the wire.

Just to let you all know the best way to remove the Engine ECU is to unbolt the metal bracket (2 bolt, 1 nut) the ECU is attached to and swivel it out from under the centre console, then unplug the ECU once out in the passenger footwell.
I got the ECU in to the passenger footwell with the battery still connected, then thought maybe the ECU Ground is supplied by the metal bracket to chassis Ground. so added a wire to bridge the gap. No ill effects to the ECU.

[bradc]

You can get them skimmed if they still have a ton of metal left.

Stock front VR-4 rotors are:

294mm, 24mm thick, minimum 22.4mm

rear are:

284mm, 20mm thick, minimum 18.4mm