Anti dieseling relay.

DaveEFI · Post by **DaveEFI** » Tue Jan 14, 2014 9:56 am

An SD1 Club member has a car fitted with the flapper EFI system from a Range Rover. It has an 'odd' extra relay which according to this:-

http://www.mez.co.uk/TuningTheRoverV8-pt9.html

"Note that on later airflap models an anti-dieseling mod was done consisting of an ignition operated relay on the airfilter bracket, which disconnects the ECU tacho feed (white/black or white/blue wire) from the coil. This isn't shown on the diagrams."

Can anyone give a clue as to how it works? Surely just switching off kills both the ECU and sparks?

unstable load · Post by **unstable load** » Tue Jan 14, 2014 11:20 am

If it's Dieseling in the sense that they mean the engine runs on after switching it off, then surely all that's needed is a way of shutting off the fuel pump to stop supplying fuel, thus stopping the run on?

DaveEFI · Post by **DaveEFI** » Wed Jan 15, 2014 2:31 pm

What it may just be, it seems, is part of the fuel cut-off on the over-run, so nothing to do with dieseling.

r2d2hp · Post by **r2d2hp** » Wed Jan 15, 2014 5:43 pm

At a guess its could be that there is some back voltage getting back to the ecu and keeping it running when the key is turned off. I had this when converting an old carbed car to run efi and when turning the car off it continued to run. In my case the problem was sorted by using a diode.

Am sure Elliot will explain when he see the post

DaveEFI · Post by **DaveEFI** » Wed Jan 15, 2014 5:51 pm

As far as I know it's not causing a problem. Was just curious about the description of what it was on that website.

ChrisJC · Post by **ChrisJC** » Wed Jan 15, 2014 9:51 pm

I suspect some confusion.

The Range Rover version of the EFi system did have an overrun valve which shut off the ignition feed to the ECU. Thus there was no fuel going into the engine during overrun conditions.

The SD1 version didn't have this.

Chris.

DaveEFI · Post by **DaveEFI** » Wed Jan 15, 2014 11:39 pm

ChrisJC wrote:I suspect some confusion.

The Range Rover version of the EFi system did have an overrun valve which shut off the ignition feed to the ECU. Thus there was no fuel going into the engine during overrun conditions.

The SD1 version didn't have this.

Chris.

Yup - I know that. What I didn't know anything about was the anti-dieseling system as mentioned here:-

http://www.mez.co.uk/TuningTheRoverV8-pt9.html

Which was what I was asking about.

SimpleSimon · Post by **SimpleSimon** » Thu Jan 16, 2014 12:39 pm

DaveEFI wrote:
ChrisJC wrote:I suspect some confusion.

The Range Rover version of the EFi system did have an overrun valve which shut off the ignition feed to the ECU. Thus there was no fuel going into the engine during overrun conditions.

The SD1 version didn't have this.

Chris.
Yup - I know that. What I didn't know anything about was the anti-dieseling system as mentioned here:-

http://www.mez.co.uk/TuningTheRoverV8-pt9.html

Which was what I was asking about.

Trouble is just cutting the FP will still allow adequate time for the motor to run on as the system de-pressurizes

seconds I know but still time, never known this to be a RV8 problem though

DaveEFI · Post by **DaveEFI** » Thu Jan 16, 2014 1:11 pm

Breaking the tach feed to the ECU will stop the injectors instantly. Which appears to be purpose of this - to prevent fuel being injected at high vacuum over-run, for emissions reasons.

And I've never know an RV8 of any type to run on either- unless something is very amiss.

ChrisJC · Post by **ChrisJC** » Thu Jan 16, 2014 8:11 pm

DaveEFI wrote:
ChrisJC wrote:I suspect some confusion.

The Range Rover version of the EFi system did have an overrun valve which shut off the ignition feed to the ECU. Thus there was no fuel going into the engine during overrun conditions.

The SD1 version didn't have this.

Chris.
Yup - I know that. What I didn't know anything about was the anti-dieseling system as mentioned here:-

http://www.mez.co.uk/TuningTheRoverV8-pt9.html

Which was what I was asking about.

I realise that Dave - it is Eliots article that I suspect might be confused, not you!

Chris.

DaveEFI · Post by **DaveEFI** » Thu Jan 16, 2014 11:44 pm

Ah - was it written by someone on here?

r2d2hp · Post by **r2d2hp** » Fri Jan 17, 2014 9:08 am

Yes, its Eliot's site.

ramon alban · Post by **ramon alban** » Fri Jan 17, 2014 12:09 pm

An SD1 Club member has a car fitted with the flapper EFI system from a Range Rover. It has an 'odd' extra relay

My take on this:

The relay described belongs to the later alternative overrun system fitted to Land Rover versions of the SD1 flapper system.

# It employs a vacuum operated switch to activate a relay disconnecting the engine running signal from Coil Negative to ECU, Pin 1, thereby preventing any fuel injection taking place during overrun.

# The point of this being that the extreme pressure differential felt across the injectors cannot suck through any extra fuel in the throttle closed mode because the injectors are not opening.

# So, no bulk mixture correction (as controlled by the normal SD1 flapper overrun valve) is required, resulting in improved exhaust emissions and fuel economy.

# It also limits any exhaust noises to a brief period at the start of an Overrun sequence when any condensed fuel in the intake area is quickly dissipated and silence reigns inside the exhaust!

This explanation is drawn from my 'Amazing Scientific Overrun Treaty' available here:-

http://www.vintagemodelairplane.com/pag ... run02.html

Eliot · Post by **Eliot** » Sat Jan 18, 2014 1:17 pm

The "tuning the rover v8" wasn't written by me - I found it on the internet very badly formatted but with lots of info, so re-formatted it and put it up for the benefit of others. Not sure who the author was.

DaveEFI · Post by **DaveEFI** » Sat Jan 18, 2014 1:59 pm

Eliot wrote:The "tuning the rover v8" wasn't written by me - I found it on the internet very badly formatted but with lots of info, so re-formatted it and put it up for the benefit of others. Not sure who the author was.

Hi Elliot - I didn't realise it was your site. The link to it was given on the SD1 club forum article.

I was hoping I'd found out something new about the flapper system. Which happens most days.