MG MGB Technical Fitting RevoTech fan to MGB BBS discussion at MG-Cars.net

MG MGB Technical - Fitting RevoTech fan to MGB

I meant to put images below. Also note they now have the note "Revotec Retrofit cooling kits are designed to work with standard unmodified vehicles", that'd be for the fitting requirements and for the cooling of standard power cars rather than uprated power. 12" fan will do more than 10", and the fan engine side and sucking is better too.

Nigel Atkins

Paul, I'm surprised you take any notice of where the 'N' is positioned on your gauge. I've had four gauges in my midget and all of them have run with the needle well before the 'N', with engine fan only and then with Revotec fan only. On the four gauges the 'N' mark has very little relation to where the needle actually is, or looking at it the other way the needle bears little relation to where the 'N' is, by that I mean the needle (and gauge) are acting more as an estimate than an accurate. Best thing I could do is is to blank out the 'N' so that it's not there, as on later gauges, because I'm the same as you and can't help mentally giving it unwarranted significance. I forget the switch on and off difference on the fan controller (5 degrees?) but like you I'd sooner it cut in earlier and cut out earlier going by the needle on the gauge. Now I know you're a technical guy and I'm certainly not but I do have 30 years and hundreds of thousands of miles experience of using various classics as dailies and running plastic cars with bigger engines that certainly heat up and hold the heat, so merely a suggestion from this experience. Set the switch to cut in earlier, say twenty-to and see what difference that makes as prevention is better than cure for heat build up. You probably know already the manufacture tolerance range of 'water' thermostats, so where on the clock does your 82 stat start to open and where did your 88 stat start to open on the clock? I've found the position on the gauge where the stat starts to open again has little relation to the correct needle position, bearing in mind the gauge probe sits just beneath the stat, and the needle doesn't show correctly for the electric fan controller allowing for it being just a bit away from the stat housing in the top hose. I did wonder if turning the fan controller so that the switch is at the bottom instead of top to perhaps be more at coolant flow might make any negligible difference but I don't have any reliable and accurate tools to see. As you know I'm all for having the cooling/heating system thoroughly cleaned (initially at least) and all kept in good and clean working order. If you've got the 10" blower Revotec then as Andy has put it might not be man enough (the Midget uses the same) plus I've found the fan and it's brackets being in front of the rad hold quite a bit of debris and insects and the build up is quite quick so the effectiveness of having a blower fan and its position are even further reduced. I went from standard (10" blower) fan kit to an uprated 10" blower fan and apart from being less noisy I didn't notice too much difference in performance. I later also replaced the fan controller (c/w cheap relay, it might have just been the relay that was faulty but I wasn't taking a chance) and being me managed to get a "one in 5,000" controller that got some sort of RFI that caused stuttered starts to the fan so had to wait for an "original design" unit to be made, in-house I believe. I guess they're all made in China now to cheaper design/manufacture, black instead of blue switch body or other way round, I can't remember. Over the years I've spoken to the Revotec guys at the NEC, and on the phone when the (first) wrong fan was sent, on the phone several times sorting the fan controller and whilst they've always been helpful and polite I feel the company may have changed a bit over the years as many British firms do.

Nigel Atkins

Mike, I agree with you and Paul I think the range is too wide. Whether it was meant to be or something's changed or the manufacturing tolerances are a lot looser than originally intended I don't know. 5c is in my mind, might be on fantasy island but the figure is stuck in my mind. Assuming (always dangerous) that your gauge shows accurate figures then 190f is 88c and 210f is 99c so a difference of 11c which is wide from 5c (if I'm correct with 5c). I'm not sure the fan blades are physically big enough on the Revotec fans especially where space isn't limited. And to correct myself the Midget has a 9" blowing fan.

Nigel Atkins

I twice tried an 88c stat in my Midget but just couldn't settle to the new needle position having also adjusted the Revotec to tie in. I'd got so used the the needle on all the gauges I'd had in the car sitting well before the 'N' (about 25-to) I went back to a 82c and didn't worry about the needle going back toward the 'C' in winter (make the expensive engine oil pay for itself). As I put I was surprised at how much debris was behind the fan and mounting plates but two years later when I removed the fan again I was even more surprised how much debris have gathered in that short time. I've no worries about battery charging as there's so little electric on the Midget and early on in ownership I fitted an uprated alternator in anticipation of fitting an electric cooling fan later and then later fitted an uprated starter motor (it's only real benefit on my car is that it doesn't do that awful clatter at start, so worth every penny). 40mph in 4th (or 50mph in 4o/d or 5th) are good cooling speeds. The expensive oils are in their element with working in the heat so again they can earn their money for me. I think it was Mike(?) that said he had his BGTV8(?) 'water' needle into the oil part of the gauge without drama (I didn't realise the needle would go that far). For road car use and the accuracy of some of the temperature gauges some owners may worry unnecessarily about needle position too much. For those that like to see an 'N' on the water gauge how about this. -

Nigel Atkins

You are right Nigel, 'twas I. Mrs H and I took the GTV8 down to visit friends not too far from Lyon in the summer of 2017. It was HOT with shade temps around 37 Celsius. Stuck in a traffic queue I watched the temp gauge climb and climb even though both radiator fans were on permanently. I couldn't take a photo at the time, but mocked one up later as you see here. The temp needle got to where I have drawn the yellow line. The engine didn't seem to mind at all and idled as normal and didn't spit out any coolant, but then it is a fuel injected engine and has 4Life coolant which has a very high boiling point. The car may have been fine, but we weren't! In a GT in those temps was very unpleasant. At one point we had to pull into a motorway camping site and seek shade as Mrs H felt faint from the heat.

Mike Howlett

Having too much time on my hands (but lack of necessary skill and tools) how about these gauges to reduce worry levels about needle positions on gauges, assuming some sort of accuracy to the gauges. (Again please forgive the poor quality of the "photoshopping" and just see the idea meant.)

Nigel Atkins

I fitted the Revotec 10 inch fan pusher fan to my MGA as an experiment to replace the standard engine driven fan. This wasn't all that effective because the car tended to run about 10 degrees hotter than it did with the engine driven fan and I found that the electric fan struggled to keep control of the temperature, especially when driving around town. I hadn't taken into account that the engine driven fan ran all of the time and therefore, it was cooling engine all of the time. So it shouldn't have come as a surprise that the electric fan similarly had to run most of the time to keep the engine cool. The MGA is a bit more prone to overheating than the MGB because its packed engine bay is a lot more restrictive to airflow. I had almost decided to go back to using only the engine driven fan when I read an article about an owner in Australia that was using twin 9 inch electric pusher fans. So I decided to try them and they have worked out brilliantly. They have more than enough cooling effect to keep the engine temperature under control. In fact I have experimented by switching the fans on permanently and I found that, even on a very hot summer day, the coolant temperature dropped to around 165 degrees F and never moved above this. I still use the Revotec thermostatic controller to operate them, I have set it to switch the fans on at 208 degrees and off again at 193 degrees. This may seem a bit high, but when my car is moving, it runs at between 175 and 185 degrees and so the fans never switch on. My engine will only ever reach 208 degrees when the car is stood in traffic and the fans soon bring the temperature back down to 193 degrees. Then when we are back on the move again, it is back to running at 175 to 185 degrees. I similarly would like to find a thermostatic switch that only have a 10 degree difference between switching on and off, but so far I haven't been able to find one. I have attached a picture of the twin fan set up on my car (they are Davies-Craig 9" fans) I have included the Revotec 10" fan on its brackets in the picture to illustrate the difference. Cheers Colyn

Colyn Firth

During the first lockdown I installed a pair of 7 inch pull fans behind the radiator on my B. I mounted them on a frame that attaches to the side mounting plates of the radiator. I did this not because the engine driven fan wasn't doing it's job, but because I'd been having the classic hot start issues in slow traffic or when filling up. I wanted to be able to move more air through the engine bay at low speeds. I felt I needed more control over the fans than I could get with off the shelf units, so I designed my own. While the radiator was out fitting the mounting hardware for the fans, I soldered a fabricated brass tube to the top left of the radiator to accept a digital temperature sensor, this gives me the readings that I use an Arduino nano to read and control the fans. As I wasn't sure what readings I'd get and how I'd need to change them, I made it as flexible as possible. The controller has a 1.3 inch OLED display that shows the temperature and state of the fans, it also includes setup options. Of the 3 buttons on the right, the white button selects the option and the red and blue button are up and down. The LED's on the left show power and the state of each fan. Due to lockdown and limited days out since fitting I've only been able to give it a number of short tests but it seems to work well and was able to control and keep the temperature down even on some of the hot days last year. Each fan is controlled separately with the on and off temps set individually, currently I've got fan 1 set to, ON at 94 and OFF at 89, fan 2 is set to ON at 96 and OFF at 90. The idea being that if fan 1 is able to control the temp, then that's all that will operate, if needed fan 2 can cut in to help. I've included a couple of other features including, Max Temp Seen, this is retained until reset, Over Temp, which flashes a warning on the display, I could add a buzzer. As this project was more about cooling the engine bay, I have considered at low speeds, say less than 5 mph, reversing 1 or both fans. This would need a speed sensor so I'll wait to see if it's needed. I was a bit reluctant to move away from the engine fan as I believe simple is best but I've included as much redundancy as I can. Each fan has it's own fuse and relay and can be controlled independently by the toggle switch to the right of the fan switch, I just need to change the legend on the switch. Bob

R.A Davis

Nigel The displays are sold as 1.3 inch displays you can also get a 0.96 inch which work the same but I thought it would be a bit small. I removed the engine driven fan and because I'm using 2 small fans the nose of the water pump and it's pulley sits nicely between them. I'd originally intended to only have the display visible, possibly sitting in place of the blanking plug where I've now got the override switch fitted but as I wanted to have access to the controls during setup it seemed easier to fit it where it is. The mechanical fan has always worked fine but I would have had to fit the fans to the front of the radiator. I wanted to avoid this for 2 reasons, I prefer the look of them fitted to the back and more importantly I believe they work better there. It also frees up a bit of power used by the mechanical fan and I believe it reduces the noise while cruising, not that you'd notice it with the top down. Bob

R.A Davis

This thread was discussed between 07/02/2021 and 22/02/2021

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