Electronically upping a 1.9xu idle by 500 rpm

[Beeluff 2 1 Cars]

Not sure if this is the right place to post this?? But I was wondering if anyone knew how to up the idle on a 205 1.9 GTI by means of an electronic switch??.....

 

example, if the car is idle-ing at 1000rpm, I’d like to press a electronic switch (maybe connected to a certain pin in the ecu?) and it rises to 1500rpm until the switch is turned off???

 

everything I can think of on the 205 to do this is mechanical and I know it’s a strange question lol!!!! there is a genuine reason for wanting to do this!!!

[welshpug 1,666]

what is the reason?!

 

the ecu has no control of the idle speed, its purely set by throttle butterfly position, you set up the ignition and fuel accordingly.

 

the only way I can figure would be an air solenoid to create an air leak in essence, fitted alongside the idle valve plumbing.

 

 

[Beeluff 2 1 Cars]

Hi welsh pug.....

 

the reason is a long one lol!!!

 

ive bare shell restored a lovely 205 over the last few years, I have been determined to get air con into it, but with the absence of local cars to inspect that have Aircon I’ve mix and matched parts from a 206 and 205 that I can find to make the whole thing look as oem as possible.....

 

today being a hot hot day I went out to test it as that’s the only way I could fully confirm it works properly. it was freezing in the cabin which was amazing, but when idling the compressor knocked the revs down from a steady 1000rpm to about 600rpm (almost stalling) so I upped the air screw to compensate for the compressor which made it idle at 1000 rpm with the compressor on, but over 1500rpm when the compressor was off.

 

my plan was to find an electronic way to up the idle by 500rpm and wire it in parallel with the compressor so when the demand was on from the compressor, the engine would compensate??

 

hope that makes sense???

 

ps, I used your very helpful thread on avoiding the cycle of doom to set the idle at 1000rpm in the first place !!!!

[Thijs_Rallye 87 4 Cars]

Just thinking "out loud". Can't you connect an extra wire to the TPS and operate a solenoid (via a relay ofcourse) which introduces a bit of extra air behind the throttle plate? (i.e. the fuel pressure regulator or an extra connection to the SAD or brake booster pipe)

Is this a motronic or jetronic? (5V or 12V on TPS switch)

[Beeluff 2 1 Cars]

Hmmmm, that sounds an idea... to mimic the sad being open so the engine revs up like when cold??..... 

 

I think mine is the jetronic? It’s a 1989 1.9, I didn’t know the difference between the two was 5v or 12v for the TPS, but that makes sense now why I see the different voltages quoted in the set up guides, so thanks for mentioning that! 

 

So out of the throttle switch idle wire, into a relay that opens a solenoid to allow air to bypass the sad mimicking the air flow the engine would get when the sad was open, and thus raising the revs???

[Beeluff 2 1 Cars]

On a side note, I’d seen this air con controller for the 205 whilst looking online, I think the 205s with Aircon as standard had an extra controller to control it all?...... and I was wondering how they got over the Rev dropping problem when the compressor was on??? Or if this ecu in the picture was only for the high/low pressure switch controls etc???

[Thijs_Rallye 87 4 Cars]

6 minutes ago, Beeluff said:

So out of the throttle switch idle wire, into a relay that opens a solenoid to allow air to bypass the sad mimicking the air flow the engine would get when the sad was open, and thus raising the revs??? 

'89 is likely a jetronic yes. With the switch to Motronic, all ECU sensor signals have been measured and fed with a 5V reference instead of a 12V reference.

 

I do have to mention is that you will have to make an additional circuit to the TPS switch, I don't think the ECU is up to the job of powering the coil of a relay. So you'll have to make something with a transistor and own 12V live feed.

[Beeluff 2 1 Cars]

Thanks for the reply, and good point on the ecu not powering the coil of the relay directly, I hadn’t thought about that, but I agree with what you are saying there! I’ll let you know how I get on  

[Thijs_Rallye 87 4 Cars]

I quickly drew this up in paint. This should work if the idle switch is at 12V with closed throttle. Never checked if that is so though . The resistor values depend on the type of transistor used.

 

As for connection 86 (coil minus) it might be better to hook that to the ECU ground to prevent earth loops. And it has to be a relay with a diode in it.

[Thijs_Rallye 87 4 Cars]

I had my head up my *rse. You could easily attach the solenoid to the same switch which turns on the magnetic clutch on the AC pump :').

[Beeluff 2 1 Cars]

Lol, oh yeah!!! That would work perfectly if the compressor kicks in and out wouldn’t it... thanks for the advice!! I just need to do it now.... just drove 300 miles to get home, so I don’t think it will be tonight tho!!

 

hopefully I’ll get onto it tomorrow and will update

[welshpug 1,666]

I see what you mean, I dont think youll need the full 500 rpm, but it will be a little trial and error trying to find a solenoid that allows enough air through to add the appropriate extra rpm.

as mentioned plumb it alongside the sad, to mimmic the sad being open wider than it is should do the trick as the AFM will add fuel for the extra air, but being on the idle circuit on the tps will help stop stalling also.

 

one valve that comes to mind which may be ideal is the evap solenoid from later charcoal canister equipped pugs, I think they run at 12v from the double relay (injection/fuel pump relay as found on gti6) using the ac compressor trigger to work a relay for this, or even tee the ac compressor feed for the solenoid.

[ian010778 21]

This is really intereting as my 205 has always suffered with high electrical load when idling and one of my main reasons for doing the refurb' as it will give me the opportunity to check and replace wiring and properly chase down any air leaks and get it all set up absolutley spot on with new breathers etc.

 

In the past I just put it down to old wiring and I also tweaked the ignition advance a little which made a big difference.

 

I don't see such a dramatic drop as the OP here as I don't have any extra ancilliaries but just to put my mind at rest - is it common for 205's (mine's a standard 1.6 XU5JA on Jetronic) to drop a few hundred revs and struggle when appliances such as the lights, heather fan and rear window heater are on simultaneously?

 

 

Ian.

[Anthony 1,003]

19 minutes ago, ian010778 said:

I don't see such a dramatic drop as the OP here as I don't have any extra ancilliaries but just to put my mind at rest - is it common for 205's (mine's a standard 1.6 XU5JA on Jetronic) to drop a few hundred revs and struggle when appliances such as the lights, heather fan and rear window heater are on simultaneously?

 

I wouldn't say that it should "struggle" when there's high electrical load, but the idle speed will drop a little on Jetronic equipped models - it's an inevitable consequence of the primitive engine management that lacks any form of idle control and can't compensate for the extra load.

 

The Motronic equipped models (1.9 GTi's with a catalyst) are much better in this regard as they can compensate to a degree to keep the idle constant.

[ian010778 21]

45 minutes ago, Anthony said:

I wouldn't say that it should "struggle" when there's high electrical load

 

Cheers Anthony - I have often wondered about this but never got around to posting about it. In the past, in winter, it has killed the idle consistently when trying to de-mist the windows with the lights on.

 

I suspect I'm going to find some very dodgy wiring when I get into the looms properly but with that fixed and everything else all set up properly I'm sure I'll see an improvement.

 

ps - sorry Beeluff for hijacking the thread

[Richie-Van-GTi 73 2 Cars]

I would use a small solenoid to push the butterfly open slightly by means of a secondary dead stop. Could put it on a thread fitting so you can tweak the position to find the lowest possible setting for a 'natural' idle with the AC engaged.

[Thijs_Rallye 87 4 Cars]

21 minutes ago, Richie-Van-GTi said:

I would use a small solenoid to push the butterfly open slightly by means of a secondary dead stop. Could put it on a thread fitting so you can tweak the position to find the lowest possible setting for a 'natural' idle with the AC engaged.

That will completely disable the overrun fuel cut off.

 

1 hour ago, ian010778 said:

I don't see such a dramatic drop as the OP here

An AC pulls about 10 Hp from the crank.

 

In regards of the solenoid sizes; I'd personally would mimic the idle screw and hole dimensions of the throttle body and plumb that in parallel to the SAD hoses. That way the solenoid does not really matter since you can throttle the additional air with the secondary idle screw. The carbon canister one is a good suggestion.

 

As for using it electronically I had some second thoughts, you still need the TPS switch because in case the pump isn't running you will have a high idle and very little engine braking power.

 

If you are starting with this I will have another look at the "schematic" because is still lacks some stuff. (I am no electrical engineer ;))

[Beeluff 2 1 Cars]

Welshpug- thanks for the reply, agreed that I don’t think I’ll need as much as 500rpm, I just used that as a generic figure to start off the thread with as I didn’t know if I’d get any replies or if I was in the right section, that Peugeot solenoid suggestion sounds a good idea, I haven’t seen or heard of them before so I’ll have a google now to see if I can find one on eBay

[Beeluff 2 1 Cars]

Rallye- thanks also, I agree that the dimensions of the sad hole when open would be about right for the load the Aircon drops the revs by, and thanks for the offer of a schematic, but don’t stress about that side too much- I am actually an electrical engineer lol, so the wiring and control side of this was a piece of cake for me, it’s all the mechanical side I’ve been struggling with haha! 

[Beeluff 2 1 Cars]

Ian- no worries for the hijack!!!! Haha

[Thijs_Rallye 87 4 Cars]

15 minutes ago, Beeluff said:

I am actually an electrical engineer lol.

Pfew , as soon as you've figured out the correct schematic and components please post back .  

 

Anyways, in regards of the additional air I did mean to mimic the actual idle hole from the throttle body with a tapered screw and all. And connecting that in parallel to the SAD hoses.

Sortof like this one:

 

 

 

[Beeluff 2 1 Cars]

Ahhh I didn’t know that sort of solenoid existed!!! But yes the fine tuning of that type with a screw would be perfect.....

 

and yes, I’ll post a schematic, I suppose the theory of this all works so I could just add this last bit in parallel with the compressor coil and do the schematic and do it now??..... although I might wait till it all actually works, just in case there is a sting in the tail haha!!!!  

 

Basically i did it with 3 relays, a sensor in the evaporator behind the dash for stopping it freezing up, a high and low pressure switch/sensor, an illuminated ac switch on the dash, and 2nd radiator fan from a diesel that comes on half speed when the Aircon is initially switched on and full speed if the high pressure switch is activated (when the condenser needs to get rid of heat).....

 

it it works perfectly without any ecu....... except for this idle issue lol!!!!! 

[Thijs_Rallye 87 4 Cars]

There are solenoids that can do this but that will need some more sophistication. I meant this:

 

If your car had an idle stepper valve this wouldn't be an issue to begin with

[Beeluff 2 1 Cars]

I’m Going to give this a go over the weekend.

 

ive quickly drawn up a schematic of the wiring side of things, and where the new solenoid will join into it all..... it’s not a brilliant drawing lol, but the basics are there!!

[forbeslongden 32 13 Cars]

I have a theory on this that may or may not help your cause, I bought a GTi some years ago which now belongs to my Mum - in the footwell was what looked like flexihose with a tap attached to the centre console on the side - what this method allows the car to do is once turned on slightly, will manually lift the revs, much like a choke I guess? So, when it's say, a cold winter morning and my Mum needs the heater screen on and the lights, it would refuse to tick over had this tap system not been installed, naturally in the summer, the car warms to temperature quicker but it's actually dead handy... Not very original Peugeot but good all the same, I'm sure it leads off one of the air hoses near the AFM.