sorting VHPD drivability issues

The Oily Bits S1 Specific Topics
21

Hi Klaus,

I checked mine today to add another car to the data. Spec is std ECU, Eliseparts exhaust (std manifold & cat) and 82° C thermostat.

Cold start (ambient 4-5° C) it idled at 1500rpm initially. Idle dropped as temperature rose, fluctuating between 1200-1400rpm until the temperature stabilised at an indicated 67°C when the idle was settled at 1200rpm.

Revving to ~4000rpm, the revs settled smoothly back to 1150-1200 similar to Keith’s video.

It was noticeable as the engine warmed, if the idle dropped below 1100, it would surge momentarily - presumably the IACV - then settle back to 12-1400.

Hope that helps!

22

Hi Tlracer,
thanks for providing your data. It seems to be that idling and returning to idle while the car is stationary is easier to achieve for the ECU.
When driving under load and coming off the throttle the situation the ECU has to deal with is more complex as there will be some surplus fuel which still needs to be burned properly.
How is your car returning to idle while moving? Are you able to cruise at 2000 to 2500rpm without stuttering?

I contacted a user over at seloc who was so kind to provide a routine from 340R users of how to adjust the idle speed screw.
It consists basically of the process of opening the throttle screw more and more while the ECU reduces the air delivered by the IACV to keep the idle revs stable.
As soon as the IACV is fully closed the revs will raise above the target and after closing the throttle a little back again you are done.
I’ll give this method a try and see what is happening.

After Keith mentioned the IACV reset procedure I did some research and found some hints in the Esprit V8 community (the V8 uses the same EFI ECU):

[u]V8 ecu reset | The Lotus Cars Community

It looks like the EFI ECU does adjust its idle control behaviour over time and stores the adjustment parameters internally.
Using the reset procedure described in the link above erases all the stored data and the ECU will start to learn from the beginning.

Klaus

23

Hi Klaus,

I haven’t noticed any issues with the revs returning to idle after a running load condition (except when I had a split vac line some time ago).

Unfortunately the British obsession with road salt at the slightest drop in temperature means I won’t be able to verify for some while now.

Certainly the ECU ‘learns’ so it might be that yours is still including the earlier issues you mentioned (gasket leak, etc.). Over time this effect may dilute or if you can perform a ‘reset’ procedure that might help?

24

This discussion is far too technical for me to offer much, but in my experience, and after reading the handbook, I can give you my experience with my car which must be one of the few which has not had the 190 upgrade. Mine is completely standard so far as I know.
On start up from cold, I rev the engine for 10 seconds (as per the handbook) or thereabouts, at just over 2,000rpm.
Foot off the throttle, the engine then settles into its typically lumpy idle. Car picks up and delivers once warmed through without any stuttering.
A long time ago, the engine would sometimes almost die when pulling up at traffic lights, and had to be kept revving as I pulled to a halt. It would not idle. That problem disappeared, no idea why.
Interesting to hear of the the ECU " learning".
When I had a Cat bypass fitted the car would gently is missfire at around 4,000 revs. I was told that the ECU would “learn” the presence of the bypass and the missfire would be eliminated eventually. It never did and I restored the Cat which cured the missfire.

25

Hi thommo,
thanks for you contribution. Very cool that your car is still all original and nice running too. It mus be one of the very few cars that run still in 177bhp spec.

I think the problem with the original ECU is not that it is a bad one but that we are missing the tools and the knowledge to investigate things once they start to go wrong.
That’s why owners switch from that black box to the Emerald unit which is well documented, offers lots of tools and a well informed community.

Klaus

26

FWIW…

I recall I had very similar ‘issues’ with my 177/190 ECU’s on Shrek (originally a 177!)

Whilst being a moderate PITA, I just accepted it as a characteristic of the VHPD!

However! I finally resolved the ‘issue’ by taking the IACV off, stripping it and both the inlet and outlet hoses off and giving the whole lot a clean… they were caked in oil etc and I doubted the IACV even worked.

Re-assembed, the ‘issue’ went away and my 190 ECU powered 'Shrek" ran so well…

… even Steve then bought him!

27

Klaus,

I really don’t believe the “wall wetting” suggestion. It is true that not all the fuel injected makes it into the cylinder on each stroke and you can get wall wetting and even puddles of fuel in the inlet tract. However, at 1200rpm, each cylinder breathes 10 times per second (1200/60*2) so any fuel will be sucked in on closed throttle pretty quickly and, as stated before, you need more air to raise the rpm significantly. It’s far more likely that there is still and air leak or the ECU is holding the rpm high. There can be many reasons why the ECU is holding the rpm high (and I have no idea how the software is written but I expect it is pretty basic). It could be from the “learning” so a reset could be useful. At times, the idle rpm has to be kept high to control emissions. As I noted, my car was idling at 1500rpm until it got hot (20 miles) and then it idled at 1200 (it just switched next time I went to idle). I would advise going for a good blast to get it nice and hot and try the idle out.

Keith

28

Hi Keith,

resetting the idle data in the ECU by using the procedure I found in the Esprit V8 posts is the next thing I will try. Good to know that it may take while due to the ECU adapting its behaviour until the final effect show up. Another air leak is rather unlikely as I exchanged all hoses and connectors but you’ll never know.

On my last drive the clutch slave cylinder broke down and I need to fit a new one. The slave cylinder was one of the very few parts I did not exchange as a precaution and of course it collapsed. Luckily it happened directly in front of my garage when I returned from my last test drive. I was just able to turn the ignition off before hitting the garage door as I couldn’t choose neutral anymore :astonished:

Klaus

29

Making sure that the IACV is properly working is essential. I bought a new one as my car came without any IACV. So hopefully mine should be fine.

Klaus

30

Chasing the drivability gremlins in my car I did some more research about the engine management. I post my findings here as they might be useful to other owners running a VHPD with the original ECU.

As most of us know the Exige S1 ECU is manufactured by EFI and shared with the 340R. It was initially used to control the turbocharged Esprit V8 engine which is a rather complex job controlling ignition, injection, boost, knock, air condition, exhaust recirculation, four lambda probes, etc.

The ECU is capable to adjust some of its setting by ‘auto-learning’ such as idle control or long term fuel trim. Good to know that those settings are kept even when the battery is removed. So you can not reset the ECU by cutting the power supply.

The ECU including the whole sensor, ignition and actuator ecosystem was carried over to the Exige S1. So nothing you read about the other Rover engined Elises is true for the Exige. It is all different.

A proper ECU/OBD scanner tool is essential as it would be very hard to solve such problems without one. Fortunately the EFI ECU uses ISO9141-2 which is one of the standardized OBD protocols. Lotus did not develop their own protocol to control the manufacturer specific settings on the ECU but extended the OBD protocol. Lotus uses the multi manufacturer covering Tech-1 scanner tool in their workshops. To get access to the proprietary settings a special cartridge needs to be inserted into the scanner tool. There is only one cartridge specified to be used with all three cars (Esprit V8, 340R and Exige S1), spare part number T000T1307F.

There is a US based seller of those cartridges for around 100 GBP see [u]http://home.earthlink.net/~turboesprit2/bitsforsale.html[/u]

I was tempted to buy one and a Tech-1 scanner but there is an alternative way. The Esprit V8 owner Peter Maeers has extended an OpenSource OBD Windows application to support the Esprit V8 specific settings. Please see [u]Free V8 OBDII Scan Tool - ECU/OBDII - The Lotus Forums - Official Lotus Community Partner for more details and get a free copy of that software.

You’ll need an ELM327 OBD connector to actually connect your laptop with the car. It is nearly impossible to buy a genuine one as there are tons of cheap Chinese clones around. My first one (too cheap, version 1.5a) didn’t work so I bought a more expensive one (version 1.4, still no idea if it is genuine one). Anything priced at less than 20-25 GBP will be a clone for sure.

The good news is that I successfully ran the software at my Exige S1 ECU :stuck_out_tongue:
I’m now able to read settings like the IACV duty cycle (very useful!) and the requested idle speed while warming up (starts with 1500rpm from cold).
You can manually switch on or off some ECU controlled ancillaries like the radiator fan or the fuel pump.

And there are a couple of options to reset different parts of the learned data. I used the full ECU reset. This seems to be the same like the one triggered by flooring the accelerator pedal four times with the engine off but ignition on and wait for 10 to 20 seconds. The successful reset is recognizable by the fuel pump priming and the re-engagement of IAC valve.

You can even log some live data into a file for further analysis but I found that the data rate was tool low to give useful results in my case.

It’s an older VisualBasic application so don’t expect an exciting user experience while working with the tool. Everything is rather slow and it may be difficult to tell if you are actually connected to the car or not. Reading all PIDs didn’t work and the tool got stuck. To be sure that I’m connected I switch the radiator fan on and wait until the fan actually starts (takes a couple of seconds if not connected).

But all in all a very useful tool and I’m very thankful that Peter Maeers has written and published this software :thumbup:

31

Saw a link to this on seloc about sport 160’s, however it does say they can deal with the EFI ECU, dont know if it will help with any of the problems youre having.
Gav

http://www.hpeauto.co.uk/sport-160-upgrade/

32

That’s interesting. Dan has a good press on on the forums, which is hard earned with all the keyboard warriors. I have spoken to him once when I had an Emerald in my Exige and he appeared to know his stuff.

33

Good to know that there is a specialist company that may fix an EFI ECU, thanks for the tip.
I think the ECU itself on my car is fine.

I noticed that the newly fitted throttle cable may still have too much friction for the nearly 3.5 meters of length. The throttle position reported by the OBD scanner jumps in small steps upwards when slowly pushing the pedal to the floor. Fitting a new TPS didn’t help either.
Next step will be to fit a new Exige S2 throttle cable and see if that helps.

EDIT:
Jonny, when you are talking to Dan could you ask him if they are able to remap the Exige S1 ECU. And it would be interesting to know what scanner tool they use to read out the Lotus specific settings.

34

I finally found the cause of the slowly dropping revs after coming off the throttle :smiley: It was caused by a slightly sticking throttle cable.
Although the cable was a new teflon lined low friction bicycle cable it was not up to the job.

Now I switched to a new Exige S2 cable as other have done before. The drivability is now as it should be with fast dropping revs when switching gears. I’m very happy with the result. The only issue that still remains is a slight stutter when cruising at lower revs but this could be normal with such an engine.


I was able to use the S2 cable without major mods to the existing throttle linkage system. I just fitted an M5 8mm ball stud to the throttle lever and attached the Exige S2 cable end. The only thing is that the cable is slightly too long (20-30cm).

This is the original setup:

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An Elise Parts upgraded throttle linkage has been fitted before:

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1024×768 83.7 KB

35

I have the S2 cable and this to do possibly at a later date. Thanks for the info :thumbup:

36

Good work finding the solution to the revs not dropping. Must admit I find mine does this a little intermittently so I may just have to check out this throttle cable replacement also. Nice work !

37

Hey trackrod, I’m currently getting data on the running of my car and I’ve suspected there may be a small manifold leak on mine. Vacuum readings are similar to yours before you fixed your leak, around 64-66kPa.

Is the seal of the airbox potentially contributing to a slightly high vacuum reading I wonder? Mine doesn’t perfectly seal and the gasket appear to no longer be available.

38

Hi Rich,

I detected the vacuum leak by spraying some brake cleaner to the seam/join of the manifold and the cylinder head while the engine was idling. Doing so the revs did noticeable rise for a short moment. You nee to be careful when spraying the brake cleaner not to set your car on fire :open_mouth:
How is the short term fuel trim on your car?

The seal between the backbox and the throttle bodies doesn’t matters as it is outside of the high vacuum area between the throttle plate and the inlet valve. Check all the small vacuum hoses for leaks or better renew them all including the tiny plastic T-connectors.

64 to 66 kPa could still be normal - I don’t know. It would be interesting to get more readings from other VHPD cars.

Klaus

Edit: I re-checked the fuel trim issue and my ECU was reducing the fuel via short term fuel trim (and not increasing it as written by me before).

39

Hi Klaus

Short term fuel trim I don’t have a full handle on yet but does seem to be fluctuating around quite a lot, I’ve seen figures ranging from -10% to -17% at idle. I don’t really understand these numbers and not sure what should be expected here.

Rich

40

Hi Rich,

as I understand it the ‘short term fuel trim’ is used by the ECU to adjust the amount of injected fuel based on the lambda reaing of the near past.
My understanding is that our ECU calculates the load and thus the required fuel based on the measured manifold pressure. Taking this value it looks into a table (the fuel map) to get the amount of fuel to inject. After the fuel has burned the lambda sensor reading is used to check if it was too much or too few fuel. In closed loop mode the ECU uses then the short term fuel trim to adjust the value taken from the map for the following injections.

So if like on my and on your car the fuel trim is constantly used to adjust the values from the fuel map there should be something wrong. My guess is that the too high MAP pressure readings messes up the calculated load so a wrong value is taken from the map all the time.

After fixing the air leak on my car the fuel trim is osciallting around 0% when idling like it should be.

Klaus