Sorry about all these electric questions, but I'm nearly finished now.

Do you need to have a permanent feed to your ECU or just one that is live when the ignition is switched on ?

ps.. finally figured out the relay stuff.. once I had established that the switch was a dim/dip one. Addressed the issue of the dip beam coming on with the side lights, by connecting the low and high beam relays with an ignition fed live connection. Turn the ignition off and the side lights stay on and the headlamps go out. (Just like my wifes Fiat....at least that's what happens on her car, couldn't say if it was right or not !)

GMTBH - our's is fed through the fused starter relay so is switched live. Having said that so are our sidelights, horn and headlights. Nothing works when ignition is off - and ours passed SVA like this.

Stops tamperers too!

I've gone for switched.

thought switched would be better, just wondered if powering the ecu on and off all the time might affect the internal memory chips in some way.

But if others have used this method and it was OK, I'll do the same

thanks

[Edited on 3/5/04 by givemethebighammer]

Most north american ecu's are learning- sensning how the car is drived and setting up the set points for the fuel / spark advance ect. shift points if its an auto. Every car I have ever seen with the engine control unit has allways had power to it and you had to disconect the battery from the car to clear memory.
Dale

I agree with give me the big hamer most ECU are lerning ans develop ther fule mapping witch is saved internelin hoever most ECU's drop tis map if the battry is disonected. however the map will be relernt very quickly.

this feature is designed in incase the battry goes flat or for when you put difrent fule in as it will give a slighly difrent bang per unit volume.

ps a new ECU sutch as the one fitted to a VAG (Valtsagen audy groupe) and I suspect many other but do not know will enter in to GYHM Get You Home Mode if it detects that ther is repeted memory corupion (constantly removing and replacing the power) this means it willstop trying to do clever stuff and gust use fixed map amongs other things.

Blake
sorry no spell checker to day

depends entirely on what ECU you have. Bosch L-Jetronic and earlier (maybe later too?) Motronic was not self learning. Certainly non-lambda systems are not self learning!!

Mine's a GEMS (now DTA) ignition only unit. Not worried about the learning thing (doubt mine does) more worried about corrupting the unit's flash memory by repeated connection / disconnection of the power. Just my thoughts ?

[Edited on 3/5/04 by givemethebighammer]

Not 100% up on the GEMS/DTA stuff, I use MBE. With this the main power is just to the relays, i.e the control box "on" relay and the fuel pump "on" relay. The ignition controlled live then turns the control box relay on. The permanent live is only connected to the switched side of the relay. The ign controlled live switches the relay on.

Maybe the GEMS is different but I doubt it.

In any case it shouldn't corrupt the eprom in the ecu. Do you have the mapping software? If so for peace of mind make a copy of the map (chipfile), then you are covered anyway.

Yes you need to have a wire from the battery to the ECU

Have a look here
http://www.xr2zetec.co.uk

quote:

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Originally posted by mad4x4
Yes you need to have a wire from the battery to the ECU

Have a look here
http://www.xr2zetec.co.uk

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If you run a OEM ECU, then you'll want to have a permanent power circuit to the ECU. The reason for this is that the computer stores trouble codes and driveability settings (especially newer ECU's that often have a learning capacity to suit themselves to the engine as it wears and changes, as well as the way the vehicle is usually driven). This is put into volitile memory so when the power is cut, they are lost (want a pain in the ass, disconnect the Porsche boxster battery without a powersaver connected). With aftermarket ECU this isn't an issue and it can be permanent or not. Might ask the supplier for their preference. Cheers!

As Givemethebighammer says, he is running a GEMS ecu (now DTA) which is aftermarket, so no need for permanent live. Also like to point out that most older OEM ecu's do NOT self learn, and do NOT need a permanent live!!

Yup NS is right, finally got hold of someone who knew about the gems unit. He said no problem with an ignition controlled feed.

Just a very minor point, many ECU post '88 have volitile memory for trouble codes. If you know you'll trigger codes with your set-up, then always switching it off is probably a good idea. Post'94 and beginning OBDII cab be a little more finicky, and NSDev is right that most anything that isn't in the past few to five years doesn't self learn, and new ones that aren't from performance cars often don't either. My past post was just to a generalized list. Cheers!