Rev limiter

[chrishill 0]

Bit of an odd one this, recently swapped my dials over and stupidly pulled the needles off without checking their positions...doh! anyway with a little help they're now roughly right, speeds just about as close as I can get it (+/- a few mph) and the rev counter is reading under by about 200rpm according to that nifty hidden digital tacho on the odometer.

 

Anyway, on to the question...

 

Should I really be able to rev the engine past the redline so that the needle is pointing almost vertically down before the rev limiter kicks in?? I noticed the other day while driving in a bit of a spirited way that it went past the red (hand slipped off the gearstick :oops:) so with the engine warm i tested it last night to see how far it went before the limiter cut in and it got vertical! at that point I stopped thinking I'd probably do some damage if i carried on...the limited never actually cut in.

[crazymarcel 0]

I've never seen my car go past the redline, but too be honest when given it that much of a caining i'm not looking at the rev counter. Will have a look next time.

 

learnt on an old car that messing with the dials/needles, they never go back how they were.

[chrishill 0]

I was parked up when I took it all the way off the clock, i'm not daft enough to cain it down a road that fast!

[gibber 0]

You shouldnt realy be reving your car that high when it is parked up, you can do all kinds of damage.

 

IT could be just the needles momentum taking it past where the red line is!

 

I think it would be best to floor it in 3 all the way up and see where the needle stops, it should be around 6900 rpm

[dr_mat 0]

Wotcha got? A VR simply won't rev beyond a certain point due to the limiter in the ECU, but a 1.8 16v might have a simpler setup with no hard limit.

[Kevin Bacon 5]

There's no point even going up there in a VR, unless it's cam'd or charged, anyway.

 

When the limiter kicks in, the engine should do the usual Hire Car style "wha wha wha wha wha wha". Couldn't tell you where the needle was pointing though as I wasn't looking.

 

And yes, agreed on the dials. All too easy to feck up. What's wrong with black/green? White dials look tacky.

[dr_mat 0]

Ah, a VR. There's a hard rev limit in the ECU. I am led to believe that earlier cars (non-CP) had a higher rev limit than later ones, or maybe it's the other way round. Who knows. Mine brick-walls at around 6600 rpm (god that VR is so smooth you just can't tell when you're running out of revs!).

[chrishill 0]

well as i said, the first time was unintentional but got me thinking, i thought it'd be a safer option doing it parked up, both from a road safety point of view (watching the revs under hard acceleration probably isnt as good a plan as watching the road) and from an engine damage standpoint, but i stand corrected.

 

there was deffinalty no 'wha wha wha', i backed off before the limiter cut in... both h8rra and chris vr6nos suspect the engine may have been cam'd but the heads not been off to check yet, would a cam'd engine give these sorts of effects?

 

oh and kev, i quite agree, no white dials here, just blue illumination and red mfa.

[Kevin Bacon 5]

Cams won't affect the rev limiter, the ECU governs that. It's not uncommon for rechipped VRs to have the rev limit either removed completely or extended.

 

I can 100% guarantee you a Standard ECU will limit the engine at it's predermined rpm. If yours isn't doing the wha wha thing, then the ECU is either faulty, or has been tampered with.

 

I would get it checked out professionally mate as you don't want to be without a limiter if you ever f'ck up a gear change.

[chrishill 0]

hmm might have to have a gander at the ECU then, would it be easy to tell if its been fiddled with or if its been chipped? where is it and how do I get at it? I've got very little history on the engine itself in terms of modifications, but like i said before both h8rra and chris vr6nos suspect its had something done to it, cams being their first guess, as its a little too sprightly for a standard VR (in their opinions).

[Kevin Bacon 5]

Haven't either Chris or H8RRA got a spare ECU (standard) you can try.....I'd be surprised if they haven't tbh!!

 

Anyway, the ECU is under the only bit of scuttle cover, LOL!

 

To make life easier, I find removing the leaf guard first makes ECU removal easier. On some cars it will just pull out of the scuttle, but on others the guard needs to come out.

 

To undo the ECU plug, pull the tabs toward you and then the plug will detach, then undo the 10mm nut holding the ECU cage to the bulkhead.

 

Once the ECU is out, remove the outer casing.

 

On the small printed cicuitboard, if you can see a chip holder, it's been rechipped. As standard, the EPROM is hardwired to the board.

If the chip is an AMD job (if modded) it will have a white sticker on it with a hand written s/n number.

 

Get the car on the rollers and look at the torque curve if you suspect it's been modded. Cams will alter the torque curve.

 

It might just be a freak like Asims.

[Funkster 0]

How does one access the hidden digital tacho? Also I've heard there's a way to turn the MFA into a digital speedo - I tried holding the button down when turning the ignition on once but this only served to removed some stuff from the list of available things.

 

Cheers,

--

Olly

[chrishill 0]

if you've got a digital odometer, with the ignition off press and hold its reset button in, turn on the ignition, then turn off, then on again and release the odometers reset button to get the extra features. not sure what they all do but No.7 is the tacho.

[dr_mat 0]

No.7 ? I didn't get that on mine. I think earlier cars had more features on that mode than later ones did.

Mine just showed instantaneous fuel consumption and one other thing.

Weird though: the speedo trip counter was showing "1" all the time, except for a few moments where I'm sure I saw it showing "2". .. no idea what that was all about.

[Chris VR6nos 0]

Chris your ECU has a 'Chip in Socket' from AMD and has the serial number on a white sticker on the EPROM's window

 

Chris

[chrishill 0]

AMD chip? :D class! theres a nice suprise! i wonder if i take it out and give them the serial number, if they have a dyno plot on record? or at least some figures?

 

matt, did you press the reset button a few times? from what i could work out the number on the trip computer is the mode you're in.

[RW1 0]

not sure what they all do but No.7 is the tacho.

 

VW Fault Finding Programme No. 16/5 ( or Bentley page 91.55)

 

Position 1 = Distance impulse number. (Can be: 3735, 6010, 3800, 6160, 3800, 6160 – depends on engine/mph or kph.).

Position 2 = Country version code. (1 all except GB/USA, 3 = GB, 4 = USA).

Position 3 = Speedo/Rev counter code.

Position 4 = No. of cylinders (4 or 6).

Position 5 = Display segment test.

Position 6 = Impulse from speedo sender, 4 pulses per wheel revolution.

Position 7 = RPM Display.

Position 8 = Programme version.

 

Applies to early VR6, later G60 & 2 ltr 16v’s.

[Chris VR6nos 0]

This is funny, i have the correct readings but i also have a 'F' instead of a 'C' for the temp and Kmh instead of Mph but it does read in celcius and mph!

How do i change that? :help:

 

 

Chris

[Supercharged 2]

Silver=Faster, What country code does it bring up?? sounds like the clocks have been changed...

[Chris VR6nos 0]

Country code : 3

[Kevin Bacon 5]

Chris your ECU has a 'Chip in Socket' from AMD and has the serial number on a white sticker on the EPROM's window

 

Chris

 

I hate being right all the time :lol:

[chrishill 0]

still yet to confirm this, AmD have no record of the reg number on file, but its had a fair few owners over the years so its possible it had a private reg. I've got to get in touch with the DVLA and find out. Apparently theres little point giving them the serial number as they do everything by registration plate, which i thought was a little odd!

[Kevin Bacon 5]

The sticker must have some relevance as why put it on there!?? I've never found AmD to be particularly helpful or pleasant tbh.

 

I rang up once about the Big Brakes they sell, asked if they fit the Corrado the anser was "No". End of conversation. F'ck em then, I don't do business with people like that.

[chrishill 0]

quote from AmD's email...

 

Don't bother taking the ecu apart it will tell us nothing from that age of

ecu type.

 

to be fair they have said they'll find out what they con provided I can give them the old reg numbers, cant say fairer than that!

[dr_mat 0]

Position 1 = Distance impulse number. (Can be: 3735, 6010, 3800, 6160, 3800, 6160 – depends on engine/mph or kph.).

Position 2 = Country version code. (1 all except GB/USA, 3 = GB, 4 = USA).

Position 3 = Speedo/Rev counter code.

Position 4 = No. of cylinders (4 or 6).

Position 5 = Display segment test.

Position 6 = Impulse from speedo sender, 4 pulses per wheel revolution.

Position 7 = RPM Display.

Position 8 = Programme version.

 

Applies to early VR6, later G60 & 2 ltr 16v’s.

 

Most of these don't work on late VR6s. The only one I remember was instantaneous MPG. Good point about the number in the trip counter (someone), that could well be right.