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petert

BE3 Gearbox Temps

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petert

After calibrating an oil temp sensor on the stove top in some cooking oil, I recently fitted it to the drain plug of the BE3 in the race car. I was alarmed to see temps of 145ºC in each of the three races. This was using Penrite Pro Gear 75W-90 oil. The sensor failed at some point in the 3rd race, so it may have even been more. I've ordered a new 170ºC sensor and will fill it with Motul 75W-140 this time. Next outing will be 23 Dec for a track/test day.

 

Does anyone else have any data on gearbox temps? Or how to cool them?

Edited by petert

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wicked

I can recall that there was someone on the forum here, who did the same and was claiming that the BE gearbox failures on turbo builds were due to excessive oil temperature, not due to weakness of the housing. 

 

TBH I'm not surprised by the 145ºC in race conditions. I've been thinking on adding cooling by adding oil pump, connected to the drain and via an oil cooler back in the filler hole or drilling a new hole in the housing for that.

Finding an electric oil pump that can resist this temperature with this thick oil is not easy, combined with the extra chance on leakage, I never continued with the idea. Since I have dedicated NA track car, my turbo equipped one hasn't been on the track anymore, so also have no need for that anymore.  

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Tom Fenton

My gut feeling would be pump as low as possible, to give positive head to the pump, probably take the oil from the diff housing, pass it through a cooler radiator then back in the top of the box somewhere. Volume needed to maintain working level with the pump running would need thinking about.

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petert
2 minutes ago, Tom Fenton said:

My gut feeling would be pump as low as possible, to give positive head to the pump, probably take the oil from the diff housing, pass it through a cooler radiator then back in the top of the box somewhere. Volume needed to maintain working level with the pump running would need thinking about.

I'm not sure. Would taking oil from the diff housing, eg the drain plug, leave the cwp dry? I'll take some pics tomorrow, but I was thinking of taking it up higher, around 5th gear.

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petert

I found some pics I'd taken earlier. Imagine taking oil out of the side casing and returning it in the side (arrow), where oil normally returns.

IMG_0658.jpg

IMG_0659.jpg

IMG_0661.jpg

Edited by petert

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PhilNW

What evidence have you that the high temp is detrimental to oil/gearbox?

What temp (from the spec) is the oil good for?

If using a pump and cooler, with all the turbulence around the diff, supply to pump would not be guaranteed and keeping the level constant would probably be tricky

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petert
7 minutes ago, PhilNW said:

What evidence have you that the high temp is detrimental to oil/gearbox?

What temp (from the spec) is the oil good for?

If using a pump and cooler, with all the turbulence around the diff, supply to pump would not be guaranteed and keeping the level constant would probably be tricky

All good questions. I know 150ºC destroys Honda gearboxes. As I said, I don't think the diff area is a good place to suck oil from.

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welshpug

straight cut dog box I'm guessing?

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wicked
39 minutes ago, petert said:

I'm not sure. Would taking oil from the diff housing, eg the drain plug, leave the cwp dry? I'll take some pics tomorrow, but I was thinking of taking it up higher, around 5th gear.

Is that point not too high, meaning even more risk of catching air in the pump.

And would the cwp because of its rotation not force the oil into the drain if you would use that as pickup? Maybe a restrictor in the line after the pump could limit the flow and avoid pumping it dry?

 

That Setrab pump has a max work temperature of 121ºC. If you put it in front of the cooler, it might see those temps?

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petert
22 minutes ago, welshpug said:

straight cut dog box I'm guessing?

No, standard 1.9L gear set and 4.75 cwp.

 

The Setrab pump will self prime.

Edited by petert

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welshpug

with standard synchros I wouldn't use anything but oem oil 75w140 is transit diff oil, treacle!

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mmt

I run Castrol syntrans 75w90 and a duct to the diff housing- just like a brake duct - for cooling. N/A race car. Never had issues 

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SRDT

There is (at least) one racing BE gearbox with external oil pump, on the 4WD Saxo T4:

c20-bv-saxo-t4.jpg

 

The pump should be a Marco UP3. As the gearbox is a custom 4WD unit internal oiling may be more complex that what we see in this picture.

Speaking of internal oiling you could try to use a oil spray bar.

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SweetBadger

Wow, that’s much hotter than I would have expected!

 

What case do you run - the later BE4 cases have cooling fins, but not sure if that would provide enough extra cooling capacity.

 

how quickly did you reach those temps? And did it stabilise at 145, or was it still on an upward curve?

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DanteICE

Wow, I thought about this not long ago, just purely out of curiosity, because my 206 GTI 180 clearly has a funky gearbox which responds to heat, as the gear change can move around from good to bad depending on previous driving circumstances. I did wonder whether oil jetting directly onto the gears and synchros would be possible, I know that's done (or was done) in F1 and high performance applications. I've read that direction of spray onto the gear is important.

 

Just food for thought, obviously heat extraction is more important.

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SRDT

If there is a hot spot somewhere inside spraying oil there could be more important than lowering the overall oil temp.

Now with oil at 145°C you must have some heat expansion on the alloy casings, that means you need more bearing preload when cold so that there is some left when hot.

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petert
16 hours ago, SweetBadger said:

Wow, that’s much hotter than I would have expected!

 

What case do you run - the later BE4 cases have cooling fins, but not sure if that would provide enough extra cooling capacity.

 

how quickly did you reach those temps? And did it stabilise at 145, or was it still on an upward curve?

It's an early BE3 case. The temp gradually increases over time. The last race was longer, so I think the temp went higher and the sensor died. It was an oil temp sensor from an XU10J4.

 

Looking at the picture of the Saxo T4, you would assume the return hose goes in the breather hole. But how would it breathe? Maybe a BE3/6 case is used and the return goes in the lift-up reverse hole. However, looking at the other pic from the same site, it would appear a temp sensor goes in that hole. It's all very interesting.

Screen Shot 2021-11-20 at 3.08.23 pm.png

Edited by petert

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SRDT

It looks like one of those racing cases for TU engines, way before PSA started to use BE4 gearboxes on TU5JP4 engines Peugeot Sport and Citroën Sport had custom cases made. Some where used on six speed gearboxes so the boss for lift-up reverse was added.

They are easy to spot: if you see a BE3 clutch fork then it's not a regular case.

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Spesh

Thats hotter than I expected!  

 

Would those oil pumps handle the crap that plated diffs put into the oil?  Suppose you could add a filter of some sort too but not sure adding complication would be the right thing to do.

 


Would be interesting if there was a way to find out if there is a particular hot 'spot' in the box and if one was found it could help with the choice of where to return the cooled oil.

 


Edit - Mocal also make a pump that looks suitable and seems to be a better price too  https://www.advocultmotorsport.co.uk/mocal-electric-oil-pump-eop2/

Edited by Spesh
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Spesh

This is the only other thread I've found on the subject when I looked into this a while back

 

 

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SRDT
7 hours ago, Spesh said:

Would be interesting if there was a way to find out if there is a particular hot 'spot' in the box and if one was found it could help with the choice of where to return the cooled oil.

On the outside you could use someting like brake temperature paint but with a narrower range.

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petert

I picked up the Motul 75W-140 and a new sensor. The Honda gurus expect the temp will only drop to 135º with the thicker oil. In the meantime, I'll start on a new gearbox in the 6spd case.

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opticaltrigger

Hi Pete, yeah, isn't this a great tread, thanks for the info your giving us all here, very interesting stuff.

 

Anyway, I thought i'd throw in a thought. Many years ago, I did know some drag racers who took the entire gear set on a manual VW unit and ground a 1/8th" slot in them all to give an oil relief channel. It showed that they picked up a few wheel hp and that the oil temperature was reduced somewhat. 30 years ago though so I can't remember the numbers involved, and I'm pretty sure that with modern oils things have moved on.

Anyway just a thought really, but I'd love to know how this develops, great one.

 

All the best,

O.T.

 

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