Strange hiccup on heavy acceleration

[LeedsMike]

Hopefully someone can help me with a strange issue.

I have an otherwise standard S2 that is fitted with an Everest chip. Under heavy acceleration, when the boost goes over around 0.5 there is a short hiccup/hesitation before the full boost is delivered.

I ran 2 test runs that were identical, one with the Everest and one with a factory standard ecu. The standard run was smooth and the Everest run produced the hiccup straight away after.

I have Elan Scan for both.

Is this a normal feature of Everest ? If not, any ideas on where to look in the data?

Thanks!

[HJ2]

Power delivery with the everest should be just as smooth as OEM.

[LeedsMike]

Could it be an ECM fault? I suppose I could swap the mountain chip around and repeat.

Wondering if anyone else has seen this type of issue?

[LeedsMike]

So another test carried out:

Take mountain chip out and try ecm in standard mode - everything worked fine

Add mountain chip to ecm that was working ok - hiccup reproduced.

Conclusion is the Everest 4.5 chip is the cause.

Not sure why though….could it be something to do with the exhaust system?

[Simon_P]

I have Elan Scan for both.

Without the files we are just guessing - My guess is secondary throttle.

[HJ2]

And you are running the correct plug-gap of 0.8mm … right?

[LeedsMike]

So, I had a deeper look at the Elan Scan data. Most things look ok apart from the knock data.

On the factory standard no knock count or retard and the mountain chip there is the following profile:

Mountain45.pdf

I am new to this type of diagnosis so if someone could help me with a resolution path, that would be great. (knock readings are on page 2)

Thanks!

[LeedsMike]

And you are running the correct plug-gap of 0.8mm … right?

I don’t know 100% but it had a recent service at a Lotus specialist so I assume so…

[dapinky]

Without seeing the car, anything I suggest is probably best taken with a grain of salt as I don't really understand enough of the Elanscan run data to be useful in determining faults from it - as such, I make suggestions based on what I would look at, and NOT what the results of the scan may suggest to other people far better at it than I am.

My thoughts have little to do with the actual chip, other than the fact that it is trying to release more power from the car than the OE chip in various ways relating to fuel delivery. (Okay I know it's more than that, but basically it tells the injectors to put more petrol in, as there is more air in there now!).

Going back to basics, you can only get more fuel in if there is somewhere to put it, and that means you have to get the old (burnt) gasses/vapours out first.

So, if the exhaust pipe isn't up to the increased flow, there may be a problem. A standard 2" pipe should be okay with an Everest chip, but if it's blocked anywhere, it wont be. So, I am thinking that it may have a partially collapsed Cat, or a breaking-up pre-cat.

In a similar vein, is the wastegate working properly? (that is far more likely to lead to overboost and fuel-cut than a simple hiccup though).

Then we are on to the injectors - are they clean enough to deliver the required amount of fuel all the way through the range? Same with fuel pump?

[Simon_P]

I am new to this type of diagnosis so if someone could help me with a resolution path, that would be great. (knock readings are on page 2)

Best is zip the scan and post it here so that we can have a look.

From the very small part of the data in your PDF it looks like you might be close too/exceeding the boost limit, but again that is a stab in the dark.

[LeedsMike]

Without seeing the car, anything I suggest is probably best taken with a grain of salt as I don't really understand enough of the Elanscan run data to be useful in determining faults from it - as such, I make suggestions based on what I would look at, and NOT what the results of the scan may suggest to other people far better at it than I am.

My thoughts have little to do with the actual chip, other than the fact that it is trying to release more power from the car than the OE chip in various ways relating to fuel delivery. (Okay I know it's more than that, but basically it tells the injectors to put more petrol in, as there is more air in there now!).

Going back to basics, you can only get more fuel in if there is somewhere to put it, and that means you have to get the old (burnt) gasses/vapours out first.

So, if the exhaust pipe isn't up to the increased flow, there may be a problem. A standard 2" pipe should be okay with an Everest chip, but if it's blocked anywhere, it wont be. So, I am thinking that it may have a partially collapsed Cat, or a breaking-up pre-cat.

In a similar vein, is the wastegate working properly? (that is far more likely to lead to overboost and fuel-cut than a simple hiccup though).

Then we are on to the injectors - are they clean enough to deliver the required amount of fuel all the way through the range? Same with fuel pump?

Thanks for this, some good pointers. I am pretty happy the exhaust and the wastegate are ok, but I have no idea whether or not the fuel pump/injectors are. Perhaps maybe I should start with some cleaner?

[LeedsMike]

I am new to this type of diagnosis so if someone could help me with a resolution path, that would be great. (knock readings are on page 2)

Best is zip the scan and post it here so that we can have a look.

From the very small part of the data in your PDF it looks like you might be close too/exceeding the boost limit, but again that is a stab in the dark.

Thanks Simon, attached is a scan file from a run just now.

070923.zip

[RonR]

I'm no expert but according to the Mountain chips website maximum boost for the Everest chip is 0.9 bar, and 0.98 bar is the fuel cut limit. You have 0.98 bar at 63.6 seconds followed by a Fuel cut, and several other instances which are close enough to have peaked at 0.98 bar. I'd be looking in the areas of Wastegate and Exhaust back pressure, as it looks like your wastegate isn't reducing the extra turbo pressure on the inlet side quickly enough.

Edit: the figures for a standard chip are: Max boost 0.65 bar, 0.92 bar fuel cut - so there's a 0.27 bar margin as standard, 0.8 bar margin with Everest.

[Fredjohn]

Edit: the figures for a standard chip are: Max boost 0.65 bar, 0.92 bar fuel cut - so there's a 0.27 bar margin as standard, 0.8 bar margin with Everest.

Surely that should be 0.08???

[Simon_P]

First observations and questions:
Try feeding the accelerator pedal in - squeeze it rather than standing on it, otherwise it looks like you are driving rather too conservatively for "Heavy Acceleration" - change gear at say 6500. its hardly got going when you are changing gear (you should notice the difference) - do you usually drive a diesel?

And, have you set the base timing in service mode?

I think that the fuel cut is because the throttle is closed

[Simon_P]

You have a slight "hesitation" as it switches from closed loop to open loop.
which version of the chip do you have and what fuel are you using ? e10?
Can you post the earlier scans that you did.

[LeedsMike]

First observations and questions:
Try feeding the accelerator pedal in - squeeze it rather than standing on it, otherwise it looks like you are driving rather too conservatively for "Heavy Acceleration" - change gear at say 6500. its hardly got going when you are changing gear (you should notice the difference) - do you usually drive a diesel?

And, have you set the base timing in service mode?

I think that the fuel cut is because the throttle is closed

Thanks @simon_p - I am a diesel driver daily i will re-test with that driving profile
The base timing was set by a Lotus specialist when the CAS was changed - one thing I do notice though is a little weird start issue from time to time where it almost feels like it might stall then a little accelerator cure it and it returns to normal - maybe that's a red herring though....

You have a slight "hesitation" as it switches from closed loop to open loop.
which version of the chip do you have and what fuel are you using ? e10?
Can you post the earlier scans that you did.

Everest 4.5 using Shell vpower99
I dont have the other scans to hand at the moment as they are on another laptop, but will record a few runs this evening and post them. Anything specific you think i should try other than the above in terms of driving profile?

Really appreciate your help here....

[LeedsMike]

080923a.zip

Here is another log file. I tried being a bit more gentle with the squeezing of the throttle. Bit restricted due to traffic.....

[LeedsMike]

You have a slight "hesitation" as it switches from closed loop to open loop.

@Simon_P - just want to double check what’s the significance of the hiccup at this point?

[Simon_P]

Hi, sorry busy for the rest of the week.

The injector pulse width is briefly constant (that means that there is no increase in fuel) as it switches to open loop. zoom in to one of the peaks and plot Pulse width and closed loop.

Also plot secondary throttle and rpm or throttle position - you lift off just as it opened hence the suggestion to change gear later - did you notice the difference?