150 Sigma ECU help

[Domus]

 

The last couple of runs in the Seven I have had a feeling that not all was 100%,  nothing i could put my finger on but I thought I needed to re fuel sooner than expected and not quite as  smooth low down in the rev range.  I checked it with the MBE lead and Easymap software yesterday, 1.04v for the TPS at 950 RPM and balanced throttle bodies and all seemed fine.

Went to Cholmondley today and the idle was very lumpy in traffic and seemed to rock the car, under load (when we had a little break in traffic) it pulled like a train.

Last time the car behaved like this it drank fuel like it was going out of fashion, a new Lambda was fitted.  This was a couple of years ago before re mapping by the Two Steves. Today it seemed to be just a little thirstier than normal.

When I connect the lead over the weekend what values indicate a good v bad Lambda?

[martyn]

A lambda can have one of two failure modes..  One where the ECU knows it is faulty (for example a completely broken wire) and another where the lambda appears to be working normally but is in-fact feeding incorrect information to the ECU.

With the first failure mode, you will get a clear error status in Easimap. The ECU will ignore the lambda and the car will appear to run fine. In my case, with the default Caterham map, I couldn't tell anything was wrong until I looked in Easimap. Switching to a new working lambda sensor didn't make any noticeable difference! Not that I monitor my fuel economy close enough to notice. Perhaps the engine didn't smell so rich when running but could be a placebo.

With the second failure mode, you probably wont get any errors so you'll have to look for other clues.

Useful panels to have open in Easimap are..

Lambda Status - Shows what the lambda is currently doing.. e.g. "Waiting for warm up timer", "Coolant temp too low", "Closed cycle", etc.

Lambda - Shows the currently detected lambda value. You should see this oscillate up and down quite predictably. If it is stuck on a value then your sensor is most likely broken. If the panel is yellow or red then the value is out of the expected range - again probably a broken sensor, or could be a wiring fault / short maybe?

There is a test you can do with a multimeter and a blowtorch on the lambda sensor. Haven't tried this myself and dont know how useful it is, but you'll find info by googling it.

 

Here is the Easimap layout I use. It has all the important info and readouts from all the sensors on a 150 sigma. Link here for a better hi-res image

 

[Domus]

 

Many thanks, will try this on Sunday.

[Domus]

 

I ended up changing the Lambda just to see if I got different readings on the laptop, which i did.

However the idle was still lumpy and the revs were not steady.  I noticed that just moving the allen key in the adjuster a thou or two moved the revs about 500 RPM and had the TPS voltage switching too and fro.  Again just loosening off the TPS screws made dramatic changes to the voltage and the revs, it really is super sensitive.

TPS removed and inspected nothing obvious and refitted.  Adjustments made again as when the engine was restarted the idle was down at 800 or so.  New TPS ordered from Ebay at £17.00 it seems cheap enough

[martyn]

The TPS generally is quite sensitive, tightening it will usually move it by ~0.01v.  I find it is better to set it with the engine off, but ignition on.  That way you're not dealing with the vibration and revs jumping about.

How did all the other parameters look from the screenshot I posted above?

[Bob_C]

It sounds as if we have the same engine. I haven't yet started playing with the TPS and balancing the throttle bodies. However, significant low rev improvement has been achieved by ensuring the plugs all have the same gap and were clean, etc. Also, ensuring that the vacuum pipe from the back end of the engine is completely blocked off at that end and open to the elements at the vacuum switch end beside the ECU. The latter took a lot of time to resolve as it is not that well documented.

Bob

[Domus]

I assume you mean the spigot next to number 4 injector, if so it seems to be sealed, the open spigot on the MAP sensor has a hose to atmosphere bent down towards the road.  New plugs bought today.

Engine is coming out next week for fitting of a lightened flywheel, when it goes back in I will fit the new TPS and set up at 1.04v with ignition on (top tip) and only fit the new plugs if I still get no joy.

I find the data on the easimap screens baffling.   I am a definite nuts and bolts man.

 

What I need is a"Get to know your easimap" session. 

[martyn]

I'd be very interested to hear your feedback on the lightened flywheel.  Its something I'm interested in but obviously such a big job to consider without knowing how much difference it actually makes.

[GFWilliams]

I didn't drive my car much before I put the lightened flywheel on it, but it is a big difference from 8kg down to 4.5kg.  The car now revs really quite fast, almost like a motorbike.

I put it on as the gearbox was out anyway, but it's one thing I'd definitely do again as it's a nice change in the way the car drives

[Domus]

 

New flywheel fitted and first road test feels quicker.  It spins up much quicker and seems to want to fly.  A good investment I think.

When taking the engine out of the car I found the centre exhaust manifold bolt loose, not falling out but certainly not as tight as the others.  I suspect this played a part in my lumpy running.

A new TPS was fitted and the engine started first kick and was allowed to warm up, then the TPS, idle speed and throttle bodies balance were all adjusted to the recommended settings which took a few cycles to get right.  One problem that came up was the TPS value was all over the place which turned out to be a poor latch on the plug connector, it would not click into place, once this was sorted the rest fell into place.

Idle is smooth now at around 950, throttle bodies are in sync at a reading of 4 Kg/H with the TPS at 1.04v.

 

Happy bunny  

 

 

[johnpbransfield]

The lightened flywheel is certainly a good investment Peter.

[colindavies56]

hi peter,have you revved it to the limiter yet,just curious.

[Domus]

 

Not yet Colin, as I say it was just a road test to check for leaks etc.

I did "make progress" though on the Edenfield by-pass.   

[Eccles]

Might sound daft but, do you split the engine and gearbox first and leave the gearbox in the car when changing the flywheel or is it an all out job?

Cheers

Ivan

[johnpbransfield]

When mine was done the gearbox was left in situ.

[Domus]

 

Ditto, out and back in in less than a day.  Two of us but we spend almost as much time looking for the tool we had in our hand just a minute ago as we do actually spannering.   

[Eccles]

Thanks guys, and I know that feeling all to well Peter!! 

Ivan