Closing the EGR Valve *check first post for links*

Re: Closing the EGR Valve

Postby Longranger1 on Sat Aug 27, 2011 2:59 pm

coxy47 wrote:Ok guys so there have been various methods posted about avoiding a CEL from an underboost code and the truck going into limp mode.

One method was to disconnect the throttle valve to ensure that there was never a vacuum in the manifold. The downsides of this being that it gives an engine light on startup and the shutdown is really rough.

Ive currently fixed this by putting a normally closed relay inline with the throttle valve servo. This is triggered once the accessory circuit is on and it creates an open circuit hence no power to the throttle. As long as you turn the key straight to the off position the car shuts down normally. So far it hasnt given me an engine light on startup :? not sure why, as i thought it would but im not complaining. This also allows a fully blanked plate to be run without causing a limp mode.

Ill post up how it goes after ive driven it a bit longer and see what happens.

*I cant take credit for this as its based of a post from RHK about 20 pages ago*

Cheers
Chris


Yet another potential fix. Sounds like a winner Chris :) .
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Re: Closing the EGR Valve

Postby sierra on Sat Aug 27, 2011 4:14 pm

coxy47 wrote:Ok guys so there have been various methods posted about avoiding a CEL from an underboost code and the truck going into limp mode.

One method was to disconnect the throttle valve to ensure that there was never a vacuum in the manifold. The downsides of this being that it gives an engine light on startup and the shutdown is really rough.

Ive currently fixed this by putting a normally closed relay inline with the throttle valve servo. This is triggered once the accessory circuit is on and it creates an open circuit hence no power to the throttle. As long as you turn the key straight to the off position the car shuts down normally. So far it hasnt given me an engine light on startup :? not sure why, as i thought it would but im not complaining. This also allows a fully blanked plate to be run without causing a limp mode.

Ill post up how it goes after ive driven it a bit longer and see what happens.

*I cant take credit for this as its based of a post from RHK about 20 pages ago*

Cheers
Chris


That's a good solution Chris. Was it easy to fit?
What are your impressions of driving with the throttle valve disabled? Against all logic I found it crisper and more responsive with it working!! :?
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Re: Closing the EGR Valve

Postby coxy47 on Sat Aug 27, 2011 5:21 pm

Personally i prefer driving with it disconnected i find it feels smoother and a bit more responsive.

As for fitting it was relatively easy hardest part was to find where to tap into the accessory circuit to trigger it off. It took around an hour and a half with lots of screwing around. Ill get some pics and post everything that has been done.
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Re: Closing the EGR Valve

Postby coxy47 on Sat Aug 27, 2011 8:07 pm

Ok so ive just gone for a bit longer of a drive and it appears that my modification has not solved my problems. It appears that creating an open circuit on the servo power supply triggers a CEL every time the egr triggers. Also it appears that intermittently the accessory circuit doesnt disengage quickly enough so its not ideal for a trigger on the relay.

Back to the drawing board.
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Re: Closing the EGR Valve

Postby sierra on Sat Aug 27, 2011 8:12 pm

I'll give it another go with it disconnected to see how it feels with the few mods since then.
I'll certainly be interested to see what you did.
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Re: Closing the EGR Valve

Postby sierra on Sat Aug 27, 2011 9:30 pm

coxy47 wrote:Ok so ive just gone for a bit longer of a drive and it appears that my modification has not solved my problems. It appears that creating an open circuit on the servo power supply triggers a CEL every time the egr triggers. Also it appears that intermittently the accessory circuit doesnt disengage quickly enough so its not ideal for a trigger on the relay.
Back to the drawing board.


That's a shame after the work but at least you gave it a go.

If yours is playing up with an EGR blank fitted why not try my idea of fitting a check valve to a tee piece on the MAP hose? $2.95 for the valve through Ebay or grab one at the local pet shop for aqariums.
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Re: Closing the EGR Valve

Postby coxy47 on Sat Aug 27, 2011 9:55 pm

Fortunately i havent had a limp mode with the blank yet. My issue is that my fuel economy goes through the roof when cruising at highway speeds and running with the trottle disconnected fixes that.

I had considered that method of fooling the map sensor but i was under the impression that my main issue was just a shortage of air in the mixture due to partially closed throttle.

Ill see if i can find a better method of triggering the relay and possibly try disabling the sensor rather then the servo and see what the effect is.
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Re: Closing the EGR Valve

Postby sierra on Sat Aug 27, 2011 10:15 pm

That's very interesting that you get better economy with it disconnected.
I'm a bit obsessive with economy and keep a note book, it's within a whisker of 8.1L/100km all the time and I don't hang about. So I would know the first tankful if it was better on mine. It gets shipped interstate in a couple of weeks but I'll give it a go when I catch up with it in WA.
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Re: Closing the EGR Valve

Postby RHKTriton on Sun Aug 28, 2011 12:40 am

Better than Lego these things, ongoing project. I just have a switch in the positive feed to the throttle drive and every so often I run it normal to see the light go out after a few starts.

What I've found that driving around Melb is painful in standard form. With throttle out of action, its much more responsive at lights etc.
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Re: Closing the EGR Valve

Postby coxy47 on Sun Aug 28, 2011 9:32 am

RHKTriton wrote:I just have a switch in the positive feed to the throttle drive and every so often I run it normal to see the light go out after a few starts.


I think i might just do this and deal with it for the moment.

I still want to try and find a better solution to the relay though. Ill need to find other then the accessory circuit to trigger it off. Was contemplating using the air con compressor circuit.
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Re: Closing the EGR Valve

Postby sierra on Sun Aug 28, 2011 5:42 pm

coxy47 wrote:
RHKTriton wrote:I just have a switch in the positive feed to the throttle drive and every so often I run it normal to see the light go out after a few starts.

I think i might just do this and deal with it for the moment.
I still want to try and find a better solution to the relay though. Ill need to find other then the accessory circuit to trigger it off. Was contemplating using the air con compressor circuit.


Could you wire it to only work when the handbrake switch is on? :?
Start up with the handbrake on, throttle body on, engine check lights off, handbrake off and away with the throttle valve off and open.
Stop, handbrake on, throttle body on and closed, shut down.
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Re: Closing the EGR Valve

Postby Longranger1 on Sun Aug 28, 2011 6:34 pm

I've wondered for a while now just how much the throttle valve would be closed at say 100km/h.

Certainly, there is a reasonable amount of boost pressure indicated. Wouldn't the throttle valve be wide open at highway speeds? The ecu would command the valve to be wide open at highway speeds I would have thought (and consequently close the egr).

If it is partially closed at say 100km'h then I would be a little concerned for economy reasons.

Edit: I'll do the disconnect thing then reconnect and compare fuel flow on the fuel computer at 100km/h and see if it actually makes a difference to fuel flow at 100km/h. Never know...
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Re: Closing the EGR Valve

Postby sierra on Sun Aug 28, 2011 7:29 pm

After a read up on EGR systems it's likely to be off at idle and full throttle but could be open at most throttle openings with the throttle butterfly going from fully closed on shut down and over run and even mimicking the throttle pedal through the range?
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Re: Closing the EGR Valve

Postby coxy47 on Sun Aug 28, 2011 8:28 pm

Longranger1 wrote:I've wondered for a while now just how much the throttle valve would be closed at say 100km/h.

Certainly, there is a reasonable amount of boost pressure indicated. Wouldn't the throttle valve be wide open at highway speeds? The ecu would command the valve to be wide open at highway speeds I would have thought (and consequently close the egr).


sierra wrote:After a read up on EGR systems it's likely to be off at idle and full throttle but could be open at most throttle openings with the throttle butterfly going from fully closed on shut down and over run and even mimicking the throttle pedal through the range?


How open much the throttle closes is purely dependent on the throttle input whether it be at 10km/h or 100km/h. Assuming the scangauge reading is accurate it goes from 99 which is fully open to 19 or 20 when closing (at least on my truck). If you let the truck idle for a while, it will partially close and open the EGR. With regards to boost, I get a vacuum of 1-2psi when the throttle is closed. Not sure if this is a side effect of the boost controller some how though.


sierra wrote:Could you wire it to only work when the handbrake switch is on? :?
Start up with the handbrake on, throttle body on, engine check lights off, handbrake off and away with the throttle valve off and open.
Stop, handbrake on, throttle body on and closed, shut down.


Thats is by far the best way to go and Ill be wiring my truck to do that when I get a chance this week. Cheers for the idea. Ill need to change it to a normally open relay in this configuration but with the one im using that not a problem.
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Re: Closing the EGR Valve

Postby RHKTriton on Mon Aug 29, 2011 7:43 am

I think years ago when EGR was first being installed (talking petrol in this case) the manuals indicated that EGR was applied at light loads and most around the 80kph mark.

Re the throttle operation, when I thought about the handbrake, I was thinking about using a delay module so that the throttle was killed for say 5 or 10mins (give engine time to warm up and sensors/ecu tests to settle). On arriving, putting the handbrake on would bring in a relay that drove the flap shut for 10secs if the ign switch is turned off - giving a normal shut down.

I've just disabled the swirl doovi and engine seems better with that off too! I'd reckon overall, if you took all the Krape off the engine could actually run to its potential, you'd save weight, make servicing easier and probably get better economy as you wouldn't have to press as hard on the loud pedal to overcome all the parasites.
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Re: Closing the EGR Valve

Postby sierra on Mon Aug 29, 2011 8:19 am

RHKTriton wrote:Re the throttle operation, when I thought about the handbrake, I was thinking about using a delay module so that the throttle was killed for say 5 or 10mins (give engine time to warm up and sensors/ecu tests to settle). On arriving, putting the handbrake on would bring in a relay that drove the flap shut for 10secs if the ign switch is turned off - giving a normal shut down.


So that's where my brainwave came from! :oops: I remember now. It's a bit like when someone borrows a book and after they've had it long enough it becomes their book! :?

I wouldn't bother with the delay module. I unplugged mine several times as soon as it was running and the ECU never picked it up. If it was wired like Coxy suggested, as long as the check engine lights are off before the handbrake is released it should be good.
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Re: Closing the EGR Valve

Postby coxy47 on Mon Aug 29, 2011 9:18 am

I remember reading about how you considered the delay RHK but ill wire it up without it first if it turns out that the CEL comes on due to me taking off the handrake too soon ill try that method but id say it does its check immediately once the engine is on.
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Re: Closing the EGR Valve

Postby coxy47 on Mon Aug 29, 2011 6:09 pm

Ok so heres another update on my attempts.

This afternoon I tried using both the handbrake light and the power supply for the stereo to trigger the relay unfortunately the handbrake light doesnt supply enough voltage to trigger the relay and the voltage supply to the stereo doesnt drop quickly enough to avoid the rough shutdown.

Im now thinking about using the break lights to trigger a normally open relay so the throttle can close when the brake pedal is pressed and will probably give that a try tomorrow. Just have to remember to have my foot on the brake at startup and shutdown.
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Re: Closing the EGR Valve

Postby gregned on Mon Aug 29, 2011 6:26 pm

Coxy you can use a SSR as these have a wide trigger range from 3 to about 50VDC
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Re: Closing the EGR Valve

Postby coxy47 on Mon Aug 29, 2011 7:08 pm

gregned wrote:Coxy you can use a SSR as these have a wide trigger range from 3 to about 50VDC


Thanks for that. Electronics really arent my strong point. I might look into a SSR the only thing that is putting me off that at the moment is the cost though (at least from a quick jaycar search).
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Re: Closing the EGR Valve

Postby Longranger1 on Mon Aug 29, 2011 7:19 pm

Solid state relays are a lot safer too. Inductive spikes aren't kind to ecu's. Although the coil in this case shouldn't cause issues as it isn't directly connected to the hardware controlled by the ecu.
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Closing the EGR Valve

Postby gregned on Mon Aug 29, 2011 7:24 pm

Coxy pm me your address I've got one that's been kicking around my drawer for 7 years now I'll send it to you.
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Re: Closing the EGR Valve

Postby RHKTriton on Tue Aug 30, 2011 8:25 am

The switch on handbrakes generally simply grounds (connects the negative side of) the lamp circuit. What you'd need is a couple of diodes and a suitable relay with spike suppression. The diodes are used to isolate the lamp and relay circuits from each other.
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Re: Closing the EGR Valve

Postby coxy47 on Tue Aug 30, 2011 3:33 pm

Yeah having looked into it further today made me realise my method was outright wrong and will be a bit complex to get it to work.

At the moment ive just wired up a switch to disconnect the power to the servo when i want it open.

This did however lead me to discover that once a pending trouble code is generated from the servo being disconnected P0638 if you reconnect the circuit the throttle still wont close until the engine has been shutoff or the code has been cleared.

Hence the voltage on the accessory circuit does drop quickly enough. Im going to try disabling the sensors rather then the servo when i get a chance and hopefully that will work better.
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Re: Closing the EGR Valve

Postby Longranger1 on Tue Aug 30, 2011 5:45 pm

Good luck trying to cheat that sucker!
The voices in my head may not be real, but they do have some damned good ideas.

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