Aiming to own one of the "coolest" MX-5 in OZ...

[Juffa]

So if I understand how the BEGI bypass works the hot coolant coming out of the cabin heater is diverted to a T junction in the upper radiator hose. This means the hot coolant is passed through the radiator before re-entering the engine and is not mixed with the cooled coolant coming out of the bottom radiator hose. This hot coolant does not flow through the block or the thermostat before it enters the radiator.

Looking at the coolant flow diagram in the link the coolant enters the block from the lower hose, and then works its way to the back of the engine where is flows via a hose into the cabin heater, and with the bypass now in place it then flows out of the heater into the BEGI bypass then into the upper radiator hose, into the radiator and so the cycle continues.

So does this mean that the coolant is not getting hot enough to open the thermostat, which for the OEM is 93c.

Anyone else?

J

[Steampunk]

Jeff;
Correct.
The coolant from the heater core returns into the water pump at the same junction where the lower radiator hose connects. In other words, the flange for the lower radiator hose and heater core return, is integral so the water pump gets feed cooled coolant from the lower radiator hose (that has passed through the radiator) AND the heated-up coolant from the heater core (that has passed through the engine) at the same time.

With the BEGi bypass, the water pump ONLY gets fed cooled coolant from the bottom radiator hose.

And Graham, 74deg Celcius in 21st Century, dot.com, iPhone, emo-generation talk

[JBT]

There can be problems with the engine running too cool...........

[Fatty]

can someone post a link to the info for the begi bypass kit, i can't find it.

[Steampunk]

http://www.bellengineering.net/product_info.php?cPath=5_12&products_id=299

They used to have a detailed description a few months ago, but stuff-all on their new site.

[Fatty]

thanks andrew.

gee you don't get much for your $89 US ... or does it include the hoses as well ?

[Sheck]

I would say that the temp sensor is off, when the thermostat stayes closed the coolant in the engine heats up very fast. I had a problem of the thermostat not opening properly when i installed my PWR radiator, i'm pretty sure that the water in the rad side of the hose was still air temp when the water on eng side was hot which roughly equalled less than the temp required for the thermostat to open (i tried 3 different thermostats).

If i was to start the car and get onto the highway after only a short drive the car's incabin temp gauge would climb up to the H at which point the equilibrium temp was enough for the thermostat to open. This is not something you want to be doing to your car.

My solution was to take out one of the little flow regulators on the edge of the thermostat so that more water would pass through when it was closed this allowed a more equal temp level on both side of the engine and that fixed the problem.

I had an aftermarket gauge getting the temp from the rad side of the thermostat and before would be on 0 -> or air temp then shoot up to 95-100 when the thermos finnaly opened, after the fix it would slowly climb up to operating temp and thermos would open and the temp would be pretty much stable. Running temp was about 80deg C. You cant trust the temp sensor unless you know it is properly calibrated, as well as the mega squirt being properly calibrated to the voltage outputs from the sensor.

Dave

[Steampunk]

thanks andrew.

gee you don't get much for your $89 US ... or does it include the hoses as well ?

Includes all the hoses.
You're right though, it isn't much to look at, but it obviously works.

[Boags]

Thermostats will allow some coolant to flow through at all times, and it's only at a certain temperature, let's say 90deg Celcius, that it will open up 100% and allow as much coolant to flow through as possible.
Thermostats open gradually, according to temperature, in other words, they are not completely closed at, for example 50deg Celcius, then completely open at 90 deg Celcius.

OK; this was something I overlooked. They aren't on/off and there is always flow. Good points.

This is turning out to be a very informative thread. Has the MS got the ability to think in Degrees C???


Boags

[Steampunk]

Has the MS got the ability to think in Degrees C???
Boags

Mei Oui Monsieur
The MS can speak in Metric and Imperial

But just for ease of reference:
200 degF = 93degC
165 degF = 74degC
145 degF = 63degC

[Mr Starlet]

Some pics might help...

..this is the stock coolant path....


...is this the path of the BEGi re-route Andrew?


I could be wrong but if that's right then I can see a problem with this path as well, I'm a firm believer that Mazda engineers designed the engine to run at particular temp for a good reason already been covered by others here. We can think of the thermostat as simply a temperature control valve that regulates the engines temperature keeping it running at optimum range, when bypassing the thermostat this way you've effectively running WITHOUT a thermostat, hence without any control or regulation for ideal temp range.

Also keep in mind the complexity of metal expansion under heat, part of the reason why the engineers design things for a reason.

I think there are merits in relocating the thermostat housing to the rear to derive a more even temperature spread across the cylinder bores for reliability and consistent wear, the stock setup has the 4th cylinder running hottest. But I think there are too much a compromise in by-passing the thermostat.

[Steampunk]

Yup, that's the path it now takes.

[Mr Starlet]

Yup, that's the path it now takes.

Hmmm... Andrew I'd seriously consider undoing the mod, you'd find the thicker radiator and air diversion plate be more than enough cooling the engine will ever need, if Mazda wanted for the engine to run that cool they could simply not add the thermostat in the first place, cheaper for them too. Just a thought.

[Sheck]

you need to take into account that the majority of the water will be flowing through the LARGE pipes at the front of the engine, with only a portion flowing through the smaller heater core side.

Easy test, run the car on idle that way no air flow and all engine heat. Just wait till the car heats up check to see if the thermo to rad hose is pressurised (thermostat open, mind this mod may have changed things) and then leave it running for a good while see what temp the MS says when the fans come on, this should be around the 82-86deg mark.

Doesnt the rear have a mini thermostat in it?? I just think you should make sure its actually running at a proper temp before you start removing things thinking the worst when all it MAY be is wrong temp readings.

Dave

[Steampunk]

Dave, the longest I've had it idling stationary is about 4 minutes and the temperature gets up to 79deg Celcius. I'll let it sit for 10 or so minutes to triple check the thermostat and everything is working fine.

Minh, I've sent BEGi an email asking if they have any issues arising from this.

NOTE: The dash temperature needle is sitting at the same "normal" position, and after lots of googling, I read that even though the needle is not accurate in terms of it doesn't move up and down gradually according to changes in temperature, it will give you an accurate reading that the engine is operating within optimum parameters, ie. if its too hot or cold, it will move out of the usual position to warn you something is amiss.