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   Adjusting 'on-boost' fuelling - now with pics!

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Topic: Adjusting 'on-boost' fuelling - now with pics! (Read 815 times)

sector-9
Senior Member

No scorpio anymore

Posts: 1069

Adjusting 'on-boost' fuelling - now with pics!
« on: Jun 24^th, 2006, 5:32pm »

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First and formost, this is very likely to affect your emissions and fuel consumption. It is imperative before making adjustments that you mark the original positions so that they can be reset if desired! Also I am not a mechanic or diesel specialist and accept no responsibility if doing any of this causes problems - it works on my car but I haven't done any long-term testing.

Start with one 115PS diesel Scorpio... http://scorpio.scrapper-site.net/boost_fuelling/smile.jpg, bonnet open helps too! http://scorpio.scrapper-site.net/boost_fuelling/say_ahh.jpg. These are the bits we'll be working on http://scorpio.scrapper-site.net/boost_fuelling/bits1.jpg

First mark the position of the throttle-position sensor in relation to the mounting bracket - use tippex or paint on a fine brush or a marker pen (http://scorpio.scrapper-site.net/boost_fuelling/step1.jpg). Slacken the two torx screws which clamp the TPS still (http://scorpio.scrapper-site.net/boost_fuelling/step2.jpg) and rotate it clockwise enough so that you can access the torx screw obscured by the wiring (http://scorpio.scrapper-site.net/boost_fuelling/step3.jpg).

Unscrew and remove the two torx screws holding the TPS bracket (http://scorpio.scrapper-site.net/boost_fuelling/step4.jpg), and the two large slot-head screws either side of the banjo union on the diaphragm housing (http://scorpio.scrapper-site.net/boost_fuelling/step5.jpg). Lift off the top of the housing (there is no need to disconnect the pipe) http://scorpio.scrapper-site.net/boost_fuelling/cover.jpg. You should now be able to see the following http://scorpio.scrapper-site.net/boost_fuelling/bits2.jpg

Gently blow off any rust particles, dirt, etc. which may have accumulated on top of the diaphragm or in the housing cover making sure none gets underneath it! If available use compressed air to blow through the boost sensing pipe connecting the housing cover to the inlet manifold.

If the diaphragm has stuck to the lower face on the housing then gently peel it off - in most cases this won't be neccessary.
You now need to remove the diaphragm so mark it up so you can refit it in it's original position (http://scorpio.scrapper-site.net/boost_fuelling/step6.jpg) then rotate it a quarter turn anti-clockwise (http://scorpio.scrapper-site.net/boost_fuelling/step7.jpg) and lift it up and off (http://scorpio.scrapper-site.net/boost_fuelling/step8.jpg). You should be able to see under it a large spring and a toothed wheel which it sits in (http://scorpio.scrapper-site.net/boost_fuelling/spring.jpg). This is an adjustable spring seat and determines how much spring pressure the diaphragm (and therefore manifold pressure) has to overcome to increase fuelling.

Mark the current position of the spring seat relative to the housing (http://scorpio.scrapper-site.net/boost_fuelling/step9.jpg) and then use the edge of a small flat-blade screwdriver to rotate it. Rotating clockwise will allow more fuel for a given manifold pressure, and vice-versa for anti-clockwise. The spring seat is held in position by a flat spring in the housing and it will click as you rotate it. Typically half to one turn should make a noticeable difference in performance. Here I've rotated mine 1/4 turn clockwise (small steps is best) http://scorpio.scrapper-site.net/boost_fuelling/step10.jpg

Insert the diaphragm and metering rod back into the central hole noting the following:

1) The conical metering section of the rod is offset (http://scorpio.scrapper-site.net/boost_fuelling/diaphragm.jpg), it should be refitted like it was removed - with the mark 90 degress out and then rotated back to line up once it is inserted fully.
2) If the metering rod will not slide fully into the hole then it is possible the metering pin is obstructing it. This protrudes into the hole (amount governed by the conical section on the diaphragm metering rod) from the front of the pump and can be pushed back in using a screw driver. This should only happen if you move the throttle or run the engine with the diaphragm removed as rotating and removing the diaphragm pushed the pin back in (you cannot pull the diaphragm up without rotating it 90 degrees first).

Refit the diaphragm housing cover and reset the TPS sensor to it's original position. Road test! Grin

Darren

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mazzy_j
Full Member

Posts: 664

Re: Adjusting 'on-boost' fuelling - 115BHP diesels
« Reply #1 on: Jun 26^th, 2006, 9:02am »

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Hi Darren, does this mean your mpg problem is fixed? I have always wondered how to turn up the boost fueling, and now i know! Grin

I have a spare pump to practice on before i do this to mine, because having fitted the forced air feed mine seems to have been running on the lean side by the feel of it.

A point to add, turning up the fueling will to a point make it quicker, but you'll need to turn up the turbo wastegate (by shortening the actuator rod) so that there is more air for the extra fuel to burn with. Anyone else thinking of doing this don't go too mad cos the old VM lump isn't a race car engine and the headgaskets aren't indestructable Wink

Another useful write up there Darren,

Matt

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Dave
Senior Member

Tourmallard 24v (ex-owner)

Posts: 1984

Re: Adjusting 'on-boost' fuelling - 115BHP diesels
« Reply #2 on: Jun 26^th, 2006, 10:47am »

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Still not tempted you to keep it, Darren? Undecided

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Life after the Scorpio ain't easy..

sector-9
Senior Member

No scorpio anymore

Posts: 1069

Re: Adjusting 'on-boost' fuelling - 115BHP diesels
« Reply #3 on: Jun 26^th, 2006, 10:34pm »

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Well I've put the price up on ebay, so if it doesn't sell then I will be keeping it provided I can find a replacement ABS sensor to get it through the MOT in a few months!

Matt, I've not really ran it much since upping the fuel quantity (don't want to fill it up in case it does sell on ebay!) but so far - as the gauge is quite consistent down to the last quarter tank - there seems to be no difference in economy and possibly it might even be better under some circumstances.

You're quite correct about needing more air for the extra fuel but it would appear my engine had no problem with air volume but too little extra fuel to take advantage of it. Like I said, I don't know if this is the case generally or just a peculiarity of my engine. In my case simply increasing the fuelling has had the desired effect though I won't know until the MOT whether the emissions are still acceptable at the new setting. If not it's only 10 minutes to set back (unfortunately I don't know what the exact original setting was as I didn't mark it). Be careful if you do shorten the wastegate rod - this will increase the manifold pressure which will generate more heat in the cylinders and this engine doesn't like being cooked!!!

Actually I'm suprised you haven't already found this adjustment out yourself - I only twiddled it after speaking to you at Harewood and hearing how you had removed the diaphragm housing and cleaned it all out including the connecting pipe. Perhaps I'm just more cavalier in my approach... Grin

Darren

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mazzy_j
Full Member

Posts: 664

Re: Adjusting 'on-boost' fuelling - 115BHP diesels
« Reply #4 on: Jun 27^th, 2006, 8:37am »

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Quote:

Actually I'm suprised you haven't already found this adjustment out yourself - I only twiddled it after speaking to you at Harewood and hearing how you had removed the diaphragm housing and cleaned it all out including the connecting pipe. Perhaps I'm just more cavalier in my approach...

I do remember seeing that gearwheel when i cleaned out the diaphram, i just didn't want to touch it because i knew i'd only end up breaking something or making it worse than it is!

That said, i gave it a go last night, gave it turn clockwise to up the fueling and went out for a test drive. The first thing i noticed was that it was idleing a bit higher (about 100rpm higher), and that i didn't need as much throttle to keep a constant speed than i did before, this was presumably because the 'base' fueling had been raised (the equivalent of me having my foot slightly on the throttle).

The real difference was above 3k rpm. After about 3500 the engine used to run out of steam, but now it pulls just as strongly from there on upwards to 4000 when i then change gear.

Having the EGR disconnected and the air feed i'm sure my engine was running extremely lean, and now the fueling has been upped it should now be closer to the optimum fuel/air ratio, which should = more power and mpg

Matt

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sector-9
Senior Member

No scorpio anymore

Posts: 1069

Re: Adjusting 'on-boost' fuelling - 115BHP diesels
« Reply #5 on: Jun 28^th, 2006, 12:34am »

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Hmmm, strange. Didn't make any noticeable difference to the idle speed on mine. Still, if it works for you then great. At the moment my EGR is all connected back up - I've 'adjusted' (in a similar cavalier fashion) the TPS so now it closes as soon as the throttle starts to open. TBH I think this is how it should have been anyway and it certainly feels more responsive under light throttle and low revs.

Of course, the proper way to do it would be to set it to give the specced output voltage when closed - if I knew what it should be!

In any case, after making any adjustments to the fuel system it would be worth disconnecting the battery for a while so the ECU re-learns the new engine characteristics on next run (if that's not crediting it with more intelligence than it has) - it made a difference to the operation of the EGR valve solenoid following the repair I did to the ECU a while back...

Darren

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sector-9
Senior Member

No scorpio anymore

Posts: 1069

Re: Adjusting 'on-boost' fuelling - 115PS diesels
« Reply #6 on: Jul 8^th, 2006, 7:25pm »

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Have now added step-by-step photos and edited the text to correct a few errors. So far it seems to have made no or very little difference to my economy but is much more enjoyable to drive. Unfortunately it hasn't helped with towing but I think that's because at the legal limit of 60mph the engine is doing less than 2000 revs in fifth gear and at this point the turbo isn't doing much. Above 2K and it's fine, even in fifth...

Darren

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taliban aka Cheekyboy2
Senior Member

I'm a YaBB newbie!

Posts: 1552

Re: Adjusting 'on-boost' fuelling - now with pics!
« Reply #7 on: Jul 12^th, 2006, 12:04am »

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excellent write up, will give this a go when i have some time....

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Dave
Senior Member

Tourmallard 24v (ex-owner)

Posts: 1984

Re: Adjusting 'on-boost' fuelling - now with pics!
« Reply #8 on: Jul 12^th, 2006, 9:39am »

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I think I know why your Scorpio is so poor economy wise, you are comparing it to that Daewoo Matiz next to it, aren't you Grin

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Life after the Scorpio ain't easy..

Dave2302
Senior Member

2006 Mercedes S55 AMG, Retired Barefoot Waterskier

Posts: 1119

Re: Adjusting 'on-boost' fuelling - now with pics!
« Reply #9 on: Jul 12^th, 2006, 2:34pm »

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Try injecting a small amount of LPG into the Manifold under full load condition, via a solenoid with micro switch at 7/8 throttle. It will take off like a scalded cat !! Grin

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Dave "The 'ol Bear" ex Footer !

sector-9
Senior Member

No scorpio anymore

Posts: 1069

Re: Adjusting 'on-boost' fuelling - now with pics!
« Reply #10 on: Jul 12^th, 2006, 11:14pm »

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Yes but I only want it take off in a forward direction - not in all directions at once (a.k.a exploding!). My knowledge of LPG is limited to caravan systems and refilling my butane soldering iron... Wink

Darren

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