C20XE ECU question

[SanderGA]

I got a 93 HPC with a C20XE last year. The engine was originally tuned by Swindon Racing Engines to 218 HP. I drove it cross country last October and for the most part it ran great. I let it sit for about a month and now it’s dead. It will turn over but won’t fire. The possible reasons in descending order of probability based on my diagnostics and reading are:

1 - dead ECU that needs to be replaced

2 - dead ignition coil

3 - crank position sensor is not working

4 - bad distributor

 

The ECU is an MBE Systems 906 and apparently they are all dead or near dead. If If I can find a working one that plugs in I’ll go that route. If I have to do something other than a direct replacement I’ll put in a modern one.

 

Are there any ECUs people recommend? How difficult is this?

 

Specs are

pre 93 C20XE

distributor

45 DCOE Webers

[coffee break]

Things I would check...

- Spark @ plugs

- Power to ECU

- Ground connections

 

FWIW

[Croc]

Following on from @coffee break after his items, I would definitely check you have a fuel pump that is priming.  Like all electrical connections, the vibrations in our cars tend to eventually impact the fuel pump as well.  

 

ECU should be fairly safe - its rare they go but the wiring connections within the MFRU wiring plugs are known to deteriorate over the years.  

 

Also if your car has the FIA battery cut off switch and/or the Caterham black rubber roll over safety cut off button switch then these should also be checked for wiring connections coming loose and electrical current not passing through them.  FIA switches usually have about a 10 year life.  

[ashyers]

Is it lacking spark or fuel?

[SanderGA]

22 minutes ago, ashyers said:

Is it lacking spark or fuel?

Thanks for all the input.

 

There’s no current coming off the ignition coil to the distributor. I’m not skilled enough to check for gas but when I try to start it, it stinks of gas so I’m assuming it has fuel but not spark.

 

I’ve been working with people on the Lotus 7 C20XE Facebook group. They’ve guided me through the process of checking the ignition coil and say the problem is that the ECU isn’t functioning. They give two reasons the ECU won’t function. The most likely explanation is that the ECU failed. It’s an MBE 906 circa 1993 and apparently they have reached the end of their life span. The other reason the ECU might not function is that it’s not getting a signal from the crank position sensor. I am working on checking that. 

 

(The C20XE Facebook group is a great resource. If I was in the UK that would be the only place I’d go. Unfortunately, some of their solutions work a lot better in the UK than the US. If I was in the UK I would have already put the car on a flatbed to someone that fixes these things . Not so easy hear. SibI thought I’d raise the issue here. 
 

I thought I had a lead on a replacement ECU of the same vintage that I could just plug in but that doesn’t appear to be the case. 
 

From the feedback above, I’m going to check the power to the ECU and learn how to verify that it’s getting fuel. I’m also going to pull a spark plug and see what that tells me.

 

Back to the original question, is there a modern ECU I could install as a replacement and, if so, how big a job is that?

[JohnCh]

To answer your original question, there are a few ignition-only ECUs available today: megajolt, Nodiz, Omex, and others.  MBE also makes a unit, which might be a little more plug and play given it's the same manufacturer as your current unit.  Of course, things have moved on so much, that might not be the case. 

 

The size of the job is...it depends.  If you aren't making any other changes, you'll want to ensure your sensors are compatible with the new ECU, and then you will need to rewire the plug so the correct wires go to the correct pin out out the ECU.  I'm also not sure if the current crop of ECUs will work with your distributor setup rather than a wasted spark.  Although, even if they do, I'd consider modernizing that aspect of the system.  

 

-John

[Lotusfan]

The trick is figuring out a new ECU that will work with the current crank position sensor and trigger wheel.  You can mount another trigger wheel and sensor but it's more work and some fabrication.   Please post what you end up doing.

[SanderGA]

I made a call to SBD Motorsports. As always, they are knowledgeable and helpful. I need to start making that my first call when things like this come up.

 

They asked me to provide photos of all the relevant parts such as the ECU, ignition coil, distributor, etc. They are going to supply a new MBE ECU (9A4i I believe for 345 GBP without VAT) along with a wiring harness suitable for my car. They put a suitable map on the ECU before they ship it. I'm going to ask them to also include a crank position sensor and an ignition coil. Mine might work but they are 30 years old and I want this all behind me. My hope is that I will need to install the new ECU, ignition coil, crank sensor, and connect the wires and I'm all set. I'm sure it won't be that easy.

 

The wiring harness for the ignition circuit is integrated with the wiring harness for the rest of the car so I'll disconnect the ignition wires from all the places they go. I can't pull the wires for the ignition circuit out of the existing OEM wiring harness. The wiring harness provided by SBD will be separate for the OEM wiring harness. I don't think that's a problem.

 

Assuming I get the new ECU and wiring harness installed, I know what I'll be thinking. Why not install a Motogadget M-unit for all the things that are not ignition related? Then I pull out the original wiring harness and I have a completely rewired 1993 Caterham HPC with modern electronics with Bluetooth! Problem for another day.

 

At the moment, I think I'm just going to proceed with the new MBE ECU, wiring harness, crank position sensor, and ignition coil. John raises the issue of my outdated distributor so I'm going to give some thought on that (issue that would never have occurred to me). I'll keep everyone informed.

 

 

 

 

 

 

 

[fastg]

I ran a MegaJolt on a V8. Simple setup using loss spark Ford EDIS coils. Simple to wire and setup, and removed the distributor. A win win.

 

Graham

Edited May 5, 2021 by fastg
auto correct

[SanderGA]

I've posted what SBD Motorsports recommend below. It's about 850 GBP of parts and includes an ignition only ECU and harness, elimination of the distributor and a new coil pack, and a new crank sensor. 

 

 I know this will fix the problem and my car will be much more reliable. Will it be more tunable or perform better? I'm guessing the answer is it would perform the same if it's properly set up with the old arrangement or the new arrangement though it may be easier to tune with this setup.

 

I realize there are other solutions that are cheaper. I could get a used MBE ECU and adapt it or any of a host of other aftermarket ECUs and set it up myself. If I had a garage where I could work on the car for three months and cobble together the parts as I hit hurdles, I might go one of those other routes but, this seems to be a package of exactly what I need and will probably save me $1,000 worth of time and frustration. Plus, I can call these guys to walk me through it when I run into problems.

 

I welcome any thoughts, and I already have the thought "that's expensive and there are much cheaper routes."

 

Thanks,

 

Sander

 

And here's their email:

 

 

Dear Sanders,

 

Thank you for all the photos, very useful. I can see that yours is a very early installation and my suggestion would be to replace it with a kit that I have quoted you for. This gives 2 advantages. First of all the original system is distributor driven with a coil pack and a king lead. So any of these components could be a fault or create issues if not now but in the future. By replacing everything there is nothing else left that can be faulty. The second advantage is you have got rid of the distributor and mounted a coil pack in its place, so no moving parts.

 

What I have done to make it easier for you to see what the kit includes is to attach links below to everything that is detailed in the quote. If you scroll down the page within each link, there are additional photos. Effectively you will unscrew the distributor you have, we provide a ball bearing in the coil mounting kit which blanks the oil fed camshaft. Then the mounting screws in place of the distributor and you fit the new coil. We have included new HT leads as they will need to be slightly longer and the originals are also likely to be coming tired from their age. There is a photo of a cylinder with the coil pack mounted with the HT leads fitted, so you can see that when it is finished it will look fairly similar to what you have now. You will then get rid of your original coil pack and king lead. The new wiring harness is self-contained and there are links within this section that describe how to wire it. In theory you should be able to find the 12 volts going into your original ECU and connect to it, but you may prefer to start again, but this is entirely up to you.

 

I have also included a crank sensor and an extension lead as we discussed on the phone yesterday. Your original one may be ok but again if you have issues it is one less thing to diagnose.

 

The only optional extra which is not in the sales order but listed at the bottom, is the basic CAN mapping kit and adapter. These are not essential, but useful. It allows either yourself or somebody at a rolling road to interrogate the ECU and see if there are any faults. It can even be used by us and we can log in with Team Viewer remotely and advise, but in theory this is more of a luxury and with a relatively simple system that you have, not essential and can easily be ordered at a later date if you wish.

 

Have a look through the links and the quote. We can then finalise the quote, include the shipping and add the PayPal fee if you wish to pay by PayPal as you did last time. If you have any specific questions by all means call as this is sometimes quicker than lots of emails.

 

MBE9A4I ECU

https://www.sbdmotorsport.co.uk/MBE9A4I-mbe9a4i-ecu--ignition-only-up-to-4-cylinders.html

 

LM9A4I-IC-WS-01

https://www.sbdmotorsport.co.uk/LM9A4I-IC-WS-01-Ignition-Only-Wiring-Harness-for-MBE9A4i-ECU.html

 

COIL-4L

https://www.sbdmotorsport.co.uk/COIL-4L-bosch-4-pin-coil-to-suit-distributorless-engines.html

 

COIL-4-MNT-02K

https://www.sbdmotorsport.co.uk/COIL-4-MNT-02K-2-0L-XE-COIL-4-Mount-and-Head-Blank-Kit.html

 

HT-LK1-SBD-03  HT Leads kit.

https://www.sbdmotorsport.co.uk/ht-lk1-sbd-02-2-0l-xe-sbd-ht-lead-set-dless-engines-1.html

 

CRK-SEN-VX2-K

https://www.sbdmotorsport.co.uk/crk-sen-vx2-k-sbd-2-0l-xe-competition-crank-sensor-kit.html

 

LM-CRK-EX

https://www.sbdmotorsport.co.uk/lm-crk-ex-vauxhall-crank-sensor-3-way-to-3-way-extension-lead.html

 

Below recommended Option to allow for fault diagnosis & tuning on rolling road (NOT INCLUDED IN QUOTE) .

 

MBE-MAP-KIT-3-CAN

https://www.sbdmotorsport.co.uk/MBE-MAP-KIT-3-CAN-basic-can-mapping-kit-for-mbe-can-based-ecus.html

 

MBE-MAP-KIT-3-CAN-ADP3

https://www.sbdmotorsport.co.uk/MBE-MAP-KIT-3-CAN-ADP3-adaptor-lead-obd-to-4-way-amp-superseal.html

 

Best Regards

 

Steve

 

 

[SanderGA]

11 hours ago, fastg said:

I ran a MegaJolt on a V8. Simple setup using loss spark Ford EDIS coils. Simple to wire and setup, and removed the distributor. A win win.

 

Graham

 

Thanks Graham. I have thought of doing something like that. I know there are a host of aftermarket ECUs that can be adapted to my car. I just can't imagine I'm going to have a lot of success doing that on my first attempt. As I noted above, they seem to be offering a near turn key package that has exactly what my car needs. I'm inclined to go that route this time and maybe be more creative next time. 

[fastg]

That looks like a great package, a lot more than a MegaJolt style setup that really only replaces your distributor. This setup is a full engine management setup just without  the fuel injection. Anything you can to to get rid of a distributor is good. 

 

Graham 

[JohnCh]

I don't see a Throttle Position Sensor mentioned.  Did they feel there was no reason to proactively replace that?  If you piecemeal this and buy common parts elsewhere (coil pack, have Magnecor make a set of plug leads to your spec, etc.), you could likely do this a bit cheaper, but there is peace of mind knowing that if something isn't working as planned you have support.  

 

-John

[SanderGA]

4 minutes ago, JohnCh said:

I don't see a Throttle Position Sensor mentioned.  Did they feel there was no reason to proactively replace that?  If you piecemeal this and buy common parts elsewhere (coil pack, have Magnecor make a set of plug leads to your spec, etc.), you could likely do this a bit cheaper, but there is peace of mind knowing that if something isn't working as planned you have support.  

 

-John

You are correct. There’s no mention of a TPS. I don’t have one currently and this new setup works without one.

[JohnCh]

One of the main benefits of converting to an ECU controlled ignition is 3D mapping which requires knowledge of the throttle opening via a TPS or MAP sensor.  The advantage over 2D is better part throttle response and reduced fuel consumption since different engine loads have different advance requirements to optimize the burn.  Although we don't intend these cars to be gas sippers, the tanks are small and every little bit helps when touring.  Given the cost and effort involved, it might be worth having that discussion with SBD before placing the order.  

 

-John

[SanderGA]

14 minutes ago, JohnCh said:

One of the main benefits of converting to an ECU controlled ignition is 3D mapping which requires knowledge of the throttle opening via a TPS or MAP sensor.  The advantage over 2D is better part throttle response and reduced fuel consumption since different engine loads have different advance requirements to optimize the burn.  Although we don't intend these cars to be gas sippers, the tanks are small and every little bit helps when touring.  Given the cost and effort involved, it might be worth having that discussion with SBD before placing the order.  

 

-John

Wise words. Thank you.

[Pokey]

My assumption would be the ECU is unlocked, but the mention of the mapping kit only seems to refer to diagnosis rather than changes.  I would just be doubly sure that what they send is something you can have someone local to you tune.

[SanderGA]

8 minutes ago, Pokey said:

My assumption would be the ECU is unlocked, but the mention of the mapping kit only seems to refer to diagnosis rather than changes.  I would just be doubly sure that what they send is something you can have someone local to you tune.

SBD can log in and check the mapping remotely. @coffee breakgave me the name of someone local that has done some work on his car. That individual may be able to help with tuning. To date, I’ve had very bad luck finding someone willing and capable to work on the car in Atlanta. I particularly need someone to tune the Weber carbs. Haven’t found anyone that seems to possess that black magic. 

[SanderGA]

I checked and I can add the throttle position sensor later. I’m going to get the car running first, see how it does and decide whether to add it.

[Croc]

3 hours ago, SanderGA said:

SBD can log in and check the mapping remotely. @coffee breakgave me the name of someone local that has done some work on his car. That individual may be able to help with tuning. To date, I’ve had very bad luck finding someone willing and capable to work on the car in Atlanta. I particularly need someone to tune the Weber carbs. Haven’t found anyone that seems to possess that black magic. 

 

SBD normally sell locked ECUs, unless you specifically buy the unlocked version.  

 

@yellowss7did a remote mapping session with SBD.  Found a local dyno with broadband connection at a suitably early hour of day to accommodate the UK.  Then while the car was on the dyno doing runs, Steve at SBD played with the map to tune it remotely.  Did not need a local engine tuning specialist at all.   Quite an efficient process with great results.  

 

Good luck on finding weber tuning specialists - they are a hard find.  I have too many of the damn things running around.  Just be thankful you only have 2 to tune...