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MG MGB Technical - Temperature Sensor

Not being very experienced with MGB electrics, can anyone tell me if there's any reason why the MGB's temperature sensor cannot be replaced with a modern unit? And if so, will the dashboard temp gauge be able to display the temperature?

I've had to take my old one off with an extractor nut as it was jammed solid, but eventually want to modify the engine to electronic ignition so a modern sensor can feed the ECU. I could replace it with another original one, and apparently this can be modified to output to an ECU but less accurately than, say, a GM sensor. My thought was, why not just clag a modern one straight in?

Grateful for thoughts on this, please assume a near-zero level of electrical knowledge but v keen to learn.

Cheers!
A Riddett

Be careful in selecting sensor and sender. A sensor is a multi-wire unit that provides coolant temperature information to the ECU to tell it, the ECU, which loop mode to operate in. A sender is a simple heat resistor that chokes a voltage sent to it depending on the heat input. A sender will generally have the one wire. Many modern cars will have both a sensor for the ECU and a separate sender for the gauge.

The answer to your question as you have written it, is no.

My advice would be to replace your u/s sender with the correct one but smear the thread with some copper slip or other such engineering sealant and wait until you choose your ECU and see what is required. For example, the Emerald will want a standard Bosch sensor, but not send a signal to the gauge - you will need to keep the MGB sender for this.

I am intrigued to know how the standard sender can be modified to give the detailed information to an ECU...

Hal Adams

Hal, thanks. It's been done on an EFI setup by a chap called Werner, his page is here: http://home.comcast.net/~whaussmann/wmgb/wmgbframeset.htm (you might have to flick through a page or two).

In this setup a GM sensor is additional to the block to inform the ECU, but later is removed and the original sender used. My thought was, if the ECU can drive a tachometer (which the MegaSquirt can do), can it drive a temperature gauge in a similar way?
A Riddett

I have not seen the comcast site before. I really do not like to criticise, but whilst Werner is doing a great job at a diy economical solution, but at the end of the day, I question what extra he is getting from the set-up. I imagine not a lot.

If you are seriously considering an ECU implant, I urge you to spend a bit more and go for a pukka job with a good injection system and a distributerless ignition, sure this will cost four or five thousand, but the result will reflect the investment (if you can call it an investment..!!)

My main criticism of Werner is that there are too many 'conversions'. A good performance engine will have the minimum of mechanical linkages. By the time you ask a distributor to advance, with the gear slap of the cam, wear of the main shaft, wear in the advance mechanism, the request can easily be a degree out of true, and maybe more. A trigger wheel and coilpack will overcome all of this.

I am not too sure about his fuel injection either, if for no other reason, he does not have a swirl pot in the fuel delivery, nor a TPS on the throttle. Both of these are vital for the injection to be precise enough to work to the small tolerances of an ECU.

To answer your question though, yes an ECU can send the necessary info to a temperature gauge and much more besides, but you are into the realms of really modern cars. I would stick to fixing yours and forget about mapping it into an ECU!

I cannot abide the noise of the B series engine, so converted mine to an injected and EDIS Rover V8. But if I were to modify the existing engine, I would go down this route for the injection:

http://www.moss-europe.co.uk/shop/viewproducts.aspx?plateindexID=15789

This is the daddy of them that combines injection with flow. Expensive, yes - and you have to allow for a fully fashioned fuel system, TPS and exhaust. Down the scale, I have heard that these are good:

http://www.extrudabody.com/servlet/the-90/2-dsh-ITB-dsh-KIT-dsh-40mm-fdsh-45mm-fdsh-48mm-or-Single-DCOE-fdsh-IDF-fdsh-IDA/Detail

But you will need a Weber 45 manifold as well, plus the fuel system.

For your ignition system, EDIS kits are easy to put together using the Ford coilpack, the only difficulty might be mounting the trigger wheel:

http://www.trigger-wheels.com/store/contents/en-uk/d6.html

For the ECU, there are many choices. I use the Emerald, but in hindsight might have done better with something else as the Emerald is better suited to performance applications:

http://www.emeraldm3d.com/ecu.html







Hal Adams

Hal, many thanks. I've put a lot of research into this, and Werner's is just one inspiration I've come across. There are loads of options, but the aim of the project is purely as a technical challenge for me, not to extract vast amounts of power! Copy all on the electronic ignition, I have plans for a full setup coming together nicely including EDIS, MegaSquirt ECU and trigger wheel. I'm working on a multiple-injection system rather than single-point, and have even found a solution to the siamesing issue which affects the B-series engine.

My real query was how I might drive the standard temperature gauge from a temperature sensor or an ECU output instead of the standard temp sender. Any ideas on how this can be done are gratefully received.

For a really odd way to inject, have a look at this one!! I couldn't help but grimace when I read it. http://www.mgexperience.net/journal/scotabbott&PageID=2#jid-1682
A Riddett

I really would park the idea of the ECU running your temp gauge - I just do not see how it can be done by the bolt on ECUs (let me know if you find one that will though!)

Yes, you are doing it the right way by researching. I do hope you keep away from the real diy solutions though!

Do not forget to look into all the add-ons such as lambda, O2 and speed sensors. These all combine to make things that much more precise.

I attach a photo of my swirl pot which might be of use to you - it does mean hacking into the boot floor and tank, but it is absolutely brilliant. Basically it is a Range Rover swirl pot, pump and fuel gauge sender all in one!



Hal Adams

Another pic. Under the floor of the tank after it was cut to take the pump. Excuse the bronzing - it was a pig of a job as the tank is so flimsy and the collar was thick steel...

Hal Adams

Cheers Hal, I've posted the same question on a number of sites and all have said the same. I just thought it was unusual; since the tachometer can be driven by the ECU I figured, why not the gauge. But a separate sensor it will be! That'll teach me to use logic. A knock sensor is also in the plan. I'm just trying to work out how a fast idle solenoid fits into the equation now.

From what I've read, the O2 sensors are fairly key to solving the siamesing issue. By having two, one on the centre branch and one on a side branch of the exhaust, the MegaSquirt has a sequential injection mode capable of adapting the injection using the data from the inner pair and one outer cylinder. It also needs big injectors - there's a wealth of info out there which will all make more sense once it comes together. But if it works, I'll be chuffed - even if it's not exactly generating any V8 thunder!

Your swirl pot looks really good, and a Range Rover item ought to be easily findable. It's one of the neater solutions I've seen as well, so I'll definitely look into it. Did you buy new or is it second hand, and did you get the collar from an old tank?
A Riddett

You have not said what you plan to use for the injector body. Most of the professionally made bodies will have a slot in the butterfly spindle to take a throttle position sensor and all good ECUs will want to see one of these. I am not sure how the diy ones you were looking at overcame this.

My swirl pot was made up using new parts, but absolutely no reason why you could not use old parts. The RR pump seems to go on forever. I do confess though to getting the collar made up by a friend of mine who has a CNC plasma cutter. The other alternative, and definitely far easier and out of sight is a separate swirl pot mounted in the spare battery well that a lot of people use:

http://www.cbsonline.co.uk/product/Rear_Mount_Fuel_Swirl_Pot_SWIR.

OK they are expensive, but good quality, but I guess you could make one up quite easily.
Hal Adams

The current plan is (deep breath) to retain the original SU's. The pistons, needles and all other elements will be removed and carefully packed up, and the spacer blocks (between carb and manifold) replaced with purpose made aluminium blocks, with an injector point underneath. The existing throttle valve spindle will be replaced by a scrap one with a slot cut in the end, to take an extension bar into a TPS mounted on the LHS of the forward carb. If that doesn't work, then I'll likely mount it on the throttle linkage assembly with a little bracket to hold it in place. It allows me to retain as much of the original fitments as possible, keeping the look vaguely original and concealing much of the injection system underneath the twin carbs. The new blocks also have ample space to take fuel rail anchor points. There are small issues with clearance around the heat shield, but I have a mockup already built which is about to be fitted with the injectors and rail and a new slimmer profile exhaust manifold.

The inspiration was this chap - http://stevesaustinhealey.com/index.php?option=com_content&view=article&id=2%3Aprojects-1&catid=2%3Aprojects&Itemid=3 - it's also one of the least work-intensive options that also doesn't need a whole raft of new parts to be grafted on. If that all works, I may eventually be able to replace the SU's completely with small throttle bodies, and use the same idea for larger bores in future - maybe a pair of scrap HIF6's. But this is purely a technical challenge, so reducing overheads is always desirable!

Thanks for the advice - we'd probably better wrap this one up or else the purists will kick us off and onto the 'modified MG's' page!! Happy driving!
A Riddett

This thread was discussed between 01/09/2012 and 11/09/2012

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