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PostPosted: Sun Nov 12, 2017 11:28 am 
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Joined: Sun Aug 21, 2016 10:43 am
Posts: 119
Location: Germany
After getting my Exige back on the road I'm currently sorting some driveability problems with the VHPD engine.
The engine runs too rich on idle and I've got the 'high idle speed while moving' problem which I think is related to the first problem.
I'm using the AutoXray 6000 EZ-Scan tool to read out the ECU data.

I know the VHPD engine reacts quite sensible to faults like buggy sensor, vacuum leaks, etc. That's what I did already:

    - new temperature, cranking and manifold temperature sensor
    - new MAP sensor which reads the same values so the old one was fine
    - new wheel speed sensor and the ECU does shows the correct speed
    - all new vacuum lines
    - new iridium spark plugs + coil pack + high tension leads
    - throttle position sensor has been renewed before and shows plausible readings between 0% and 100%
    - new idle air control valve (IACV) and hoses
    - new lambda sensor which shows the typical 'narrow band' voltage jumps
    - balanced the throttle bodies

The following things are ongoing:
    - renew the manifold gasket as I suspect the old one to be faulty. Spraying brake cleaner on the joint did affect the idle speed.
    - letting the injectors be refurbished by a local ASNU service

To help tracing the error(s) I'd like to know:

    1. which manifold pressure do you see during idle? Mine reads 65 to 70kPa which I think is to high.
    2. which short term fuel trim do you see while idling. I see -7.5% to -15% on my car which indicates rich running. The car does run in 'closed loop' after warming up.
    3. does anybody know a source for the fuel pressure regulator? It reads MKW10016 on its housing and it should be a Rover part.
    4. is anybody running the 190hp ECU together with a cat? The cat and the exhaust are getting really hot (500 to 600°C easily on the outside of the cat and still 250°C at the entry of the exhaust). The high temperatures are probably related with the rich-running problem and might disappear if that is solved.
    5. Which air flow do you see when balancing the throttle bodies using a 'air flow meter' (idling at 1250rpm)? Either when running with or without IACV connected.
    6. I couldn't find any torque setting or the tightening order for the manifold screws in the workshop manual.

I'd like to stay with the standard ECU so going the Emerald route is currently no option.
Any input is highly appreciated.

Regards,

Klaus


Last edited by trackrod on Fri Nov 17, 2017 7:55 am, edited 1 time in total.

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PostPosted: Sun Nov 12, 2017 1:17 pm 
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Joined: Wed Sep 27, 2006 1:50 pm
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Location: Perth OZ
The 'standard' ECU is very limited how it handles the engine... runs it very rich amongst other problems.

I know you said you did not, but I would 100% get an Emerald fitted... it solves all the problems it sounds like you are having and will get the best out of the VHPD with power, fuel 'economy' and drivability!

Been there, done that, fitting an Emerald and having it RR tuned properly works!

You can always retro-fit the OEM ECU if needs be when Exige S1 values hit the £100k mark!


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PostPosted: Sun Nov 12, 2017 2:23 pm 
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Joined: Sun Aug 21, 2016 10:43 am
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Location: Germany
The biggest advantage of fitting an Emerald would be that the ECU is no longer a 'black box' and you can take full control of the settings.
On the other hand I believe that quite some development time was spent by Lotus to get things like cold start, barometric compensation, closed loop mode, etc. right.

Switching to an aftermarket unit means to do it all over again or just live with a simple map that needs to fit all situations.

As long as there are still faults in the system like air leaks, defective sensors or a broken fuel pressure regulator I need to get those things fixed first.
When my car runs as good as a VHPD might run using the standard ECU and I'm still not happy I will go the Emerald route.


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PostPosted: Sun Nov 12, 2017 9:18 pm 
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Joined: Fri Feb 12, 2010 4:45 pm
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Location: Sunny Derbyshire
I'm with you and I would not fit an Emerald. I switched to one when my VHPD ran dangerously badly and it was better but it stumbled with things like changes in altitude, weather, temp, even switching the lights on dipped the idle speed and mapping things like canister purge or IACV never really worked well. It had been mapped professionally on a RR and timed with verniers and made 188 bhp and pulled like a train on track. I then fixed the lambda probe and it ran so much better on the standard ECU that I switched back. It was down on power compared with the Emerald but more driveable in varying situations. However, I would use an Emerald if I had a tweaked engine.

The symptoms of my car was that it used to run nicely when cold and then run like a dog when warmed up. I now realise that was when it switched to closed loop lambda control and the lambda probe was giving dud readings. The standard ECU does not switch on the check engine light. That does not sound like your problem.

In my case I know it is possible to get a standard ECU to start first time, idle at 1000-1100rpm, pull from 2000rpm in any gear and not drive like a bucking bronco. My car did none of those when I first got it. It now is almost as tame as a standard K, apart from the noise.


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PostPosted: Sun Nov 12, 2017 10:09 pm 
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Location: Germany
I'm just trying to understand what's going on. I think the increased idle speed while the car is moving is not a bug but a feature.
The ECU tries to protect the system from damage by avoiding a rich running idle.

It is probably the same feature when lifting the throttle and there is still some surplus fuel on the manifold walls that needs to be properly burned but the airflow dropped to nearly zero. Using the IACV the ECU is able to burn the fuel in a controlled manor and what may also helps to keep emissions low.

Assuming there might be an air leak and the manifold pressure wouldn't be as low as it should be while idling. As a result a too high value will be taken from the static fuelling table. In addition the fuel pressure regulator does not reduce the fuel pressure enough as it would be necessary when idling.
As the TPS indicates 0% throttle opening the ECU 'knows' it should keep the engine at idle speed and uses the IACV and the ignition advance to keep the revs down. In closed loop mode it tries then to trim the surplus fuel using short term fuel trim.

Keith, are you able to read your ECU data to tell me what MAP value you see when your car is idling? The workshop manual states 25 to 40 kPa for the standard Elise but no value is given for the VHPD engine.


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PostPosted: Sun Nov 12, 2017 10:26 pm 
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Joined: Fri Feb 12, 2010 4:45 pm
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Location: Sunny Derbyshire
Klaus,

Sorry, I do not have a scanner for my car. I have a simple OBD Blue Tooth transmitter which gives me a few values but nothing much. My car does not have "high idle". If I come off the gas (even at speed) it would fall to idle if I put it into neutral (I will confirm tomorrow when I collect it from being serviced by Gavin). I think you are on the right track, high idle means too much air. Have you checked your IACV works? I had one which was stuck. If it's stuck (part) open that could be your problem.

I believe, the standard ECU will run the engine with the IACV disconnected and blocked off, so it's an easy test. If you need a new valve (Bosch part) I believe they are a SAAB part number (maybe GM) and are cheap on ebay.

Keith


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PostPosted: Mon Nov 13, 2017 8:24 pm 
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Joined: Sun Aug 21, 2016 10:43 am
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Location: Germany
Hi Keith, thanks for your thoughts. I bought a new IACV so this should be fine. In fact what I was trying to explain above is that the 'high idle while moving' issue is just a symptom of
another problem that is the too rich running at the low idle level. I'm pretty sure that blocking the IACV valve will prevent the high idle level but it wouldn't solve the actual problem.
So most likely the idle will return to a normal level as soon as the mixture at the low idle speed has been fixedr.
Let's see what is happening once I renewed the manifold gasket, checked the fuel pressure regulator and fitted the cleaned and serviced injection valves.

Knowing the right manifold pressure level on idle would help a lot but it looks like there aren't too many owners around that have access to an OBD scanner tool.
For me the scanner tool is very useful and it would be very difficult for me to solve such problems without it.

Klaus


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PostPosted: Tue Nov 14, 2017 5:53 pm 
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Location: Sunny Derbyshire
I have just read your first post more carefully. Fix the manifold leak and there is good chance all will be well. High idle will come from a leak. Having a leak will give some odd fuel map results which will affect the mixture.


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PostPosted: Thu Nov 16, 2017 8:11 pm 
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Joined: Sun Aug 21, 2016 10:43 am
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Location: Germany
The injectors have been cleaned and checked by the German distributor of ASNU machines with before and after comparison. They weren't too bad before but now they are near perfect. He told me that there is zero deviation in the injection quantity between all four of them. This could be only achieved if the injectors have been perfectly matched to each other by Lotus. The guy told me that Porsche used to match their injectors to a level of +/- 2% but stopped it some years ago. So zero percent deviation is quite impressive.

I fixed the manifold gasket by cleaning the surfaces, checked them for straightness and using liquid sealant as the new gasket. I re-balanced the throttle bodies with the IACV disconnected. The car runs now better than before :).
The MAP dropped from 70kPa to something like 58-60kPa while idling. The rich running idle stopped and the fuel trim stays around 0% in closed loop mode.

While driving the car the high idling issue stopped but to my feeling it is still not perfect. When I come off the throttle it may take a second or two until the revs are fully dropped to 1250 rpm. And there is an occasional slight stutter when driving at around 2000 to 2500rpm.

Unfortunately there is no other car with a VHPD engine around so I have no clue what is considered to be normal.
I would appreciate it a lot if others would share their experience considering returning to idle and driving at constant lower revs.


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PostPosted: Thu Nov 16, 2017 9:47 pm 
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Joined: Fri Feb 12, 2010 4:45 pm
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Location: Sunny Derbyshire
:) that sounds much better. Have you reconnected the IACV and driven it, it will have better idle control.

I need to take mine out at the weekend so I can make a recording of how it behaves. I would say that slowly falling back to the correct idle is normal. Not sure of the time taken, it's not instant. Have you had verniers fitted? I have them on my car and one cam was quite a bit out, it was set with power runs.

Keith


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