Why the cooling rads on the Cerb don't work
Discussion
Took my cerb to bits yesterday to inspect the rads yesterday. A whole day needed to clear enough just to see them. I wonder why they couldn't have made the bottom of the nose detacheable 
Anyway, got a bit of a shock because I have to remove the fans to locate a leak. The fans are mounted on plastic surrounds which completely cover the back of the radiator. There is no airflow unless it travels through the fan?
If the fan isn't turning then you have virtually no airflow through the radiator. The car relies on airflow around only, and theres precious little of that with the air con radiator in front and the oil cooler to one side.
Has anyone tried removing the plastic surround. Obviously the fans would be a little less efficient but surely the conventional airflow would be much better?
Anyway, got a bit of a shock because I have to remove the fans to locate a leak. The fans are mounted on plastic surrounds which completely cover the back of the radiator. There is no airflow unless it travels through the fan?
If the fan isn't turning then you have virtually no airflow through the radiator. The car relies on airflow around only, and theres precious little of that with the air con radiator in front and the oil cooler to one side.
Has anyone tried removing the plastic surround. Obviously the fans would be a little less efficient but surely the conventional airflow would be much better?
What about when you're stuck in traffic, if the fans are not working as efficently then surely it'll overheat.
I see what you mean about improving the airflow though, however, on the M4 today, temp gauge didn't go over 80, (can't say the same for the speedo), stuck in miserable Bristol, was up around 95 with the fans almost constantly on, seems to work fine in both conditions.
See your point, but I'll leave it alone for now.
Edited to add, Had an old Cortina years ago, that had no shrouding on the rear of the rad, and it was so efficent that you had to block off half of it just so it'd run hot enough at this time of year
>> Edited by crazycats on Friday 7th November 18:24
I see what you mean about improving the airflow though, however, on the M4 today, temp gauge didn't go over 80, (can't say the same for the speedo), stuck in miserable Bristol, was up around 95 with the fans almost constantly on, seems to work fine in both conditions.
See your point, but I'll leave it alone for now.
Edited to add, Had an old Cortina years ago, that had no shrouding on the rear of the rad, and it was so efficent that you had to block off half of it just so it'd run hot enough at this time of year
>> Edited by crazycats on Friday 7th November 18:24
OOOOh cooling.
A subject I was very interested in when I had my cerb. I too was always convinced that the cooling was crap (especially in traffic) but the dealer never agreed with me, using the fact it never overheated as proof.
Remove the shrouds. Hmmmm. Well plenty of cars I have seen run with no radiator shrouds (not TVR's), particularly older cars.
Whilst I normally defer to Mr GreenV8s, I would say try it. To test the cooling in traffic simply go gor a run, park it on the drive and let it idle. Note how fast the temp drops when the fans cut in and see if the cooling is noticeably worse (not letting it actually overheat obviously
).
Sadly in this weather the cooling when on the move will be fine even with the shrouds in place, so removing them will make no difference. I reckon this would have made a big difference in the summer we've just had mind you.
Keep up the good work in supporting the cerbera community. This is the sort of thing the dealers and factory should be helping with IMHO.
Rob.
A subject I was very interested in when I had my cerb. I too was always convinced that the cooling was crap (especially in traffic) but the dealer never agreed with me, using the fact it never overheated as proof.
Remove the shrouds. Hmmmm. Well plenty of cars I have seen run with no radiator shrouds (not TVR's), particularly older cars.
Whilst I normally defer to Mr GreenV8s, I would say try it. To test the cooling in traffic simply go gor a run, park it on the drive and let it idle. Note how fast the temp drops when the fans cut in and see if the cooling is noticeably worse (not letting it actually overheat obviously
). Sadly in this weather the cooling when on the move will be fine even with the shrouds in place, so removing them will make no difference. I reckon this would have made a big difference in the summer we've just had mind you.
Keep up the good work in supporting the cerbera community. This is the sort of thing the dealers and factory should be helping with IMHO.
Rob.
Have a switch installed to turn the fans on when needed and remember that air out is just as important as air in for cooling. Have you thought about additional vents in the bonnet?
Couldn't find a good pic, but imagine these two vents either up towards the windscreen end or turned through 90 degrees and placed on either side of the bonnet at the windscreen end.
Couldn't find a good pic, but imagine these two vents either up towards the windscreen end or turned through 90 degrees and placed on either side of the bonnet at the windscreen end.
ro_butler said:
I would say try it.
Never hurts to try, although I agree at this time of year the system has so much spare cooling available its hard to compare. But I would expect it to be significantly worse without shrouds. Hence virtually every modern production car has them. The reason is, increasing the air flow through the matrix is a case of diminishing returns. Double the air flow through the same bit of matrix gives much less than double the cooling. But increasing the amount of matrix that has air moving through it increases the cooling roughly in proportion to the area. Since the air is spread out over a bigger area is is slower through the matrix so there will be less drag - you can get more blown air flow with the shrouds as well as better distribution over the matrix.
The shroud will probably cut ram air flow by 10%, which will cut cooling by about 1% while you're moving. But when you're stationary, the shroud means you're pulling air over the whole area of the matrix, not just the half actually swept by the fans. This could roughly double the available cooling.
I would not remove the shrouds. Pete is right and many have taken them off and found that their cars will overheat more in traffic. Interestingly on the Griffs and Chimaeras, the factory started with no shrouds and then very quickly fitted them. They are pretty well essential to keep these cars cool.
The cooling system is adequate but the margin is not as big with other cars and it needs to be kept in A1 condition. If the car overheats, there is a problem. It is not a design limitation.
The cooling system is adequate but the margin is not as big with other cars and it needs to be kept in A1 condition. If the car overheats, there is a problem. It is not a design limitation.
GreenV8S said:
The reason is, increasing the air flow through the matrix is a case of diminishing returns. Double the air flow through the same bit of matrix gives much less than double the cooling. But increasing the amount of matrix that has air moving through it increases the cooling roughly in proportion to the area. Since the air is spread out over a bigger area is is slower through the matrix so there will be less drag - you can get more blown air flow with the shrouds as well as better distribution over the matrix.
I think what Julian was getting at is that the shroud blocks off the back of the radiator, thus restricting airflow. Removing them will allow air to flow through a larger area of matrix when on the move giving a proportional increase in cooling (as stated above by yourself). Wasn't really thinking about ram effect.
I fully appreciate the arguments for the fan efficiency increase due to the shrouds but I can't quantify how much it helps, so that was why I suggested trying it out.
I guess you're probably right though.
I had to remove the shrouding on my 520 when the alloy rad went in and there is a marked decrease in cooling capability. I had to uprate the fans to Chimaera/Cerbera ones to maintain a similar level of cooling when the fans kicked in in traffic. Keep meaning to make a new one but as it maintains the right temp, I haven't bothered. Without the shroud, the fans will draw air in from outside and not through the rad and in traffic that is what calls the issues.
Some rads are mounted close to the rad with no shroud. Problem is that the fan bearings can wear causing the blades to move and wear through the rad core with disasterous results.
Some rads are mounted close to the rad with no shroud. Problem is that the fan bearings can wear causing the blades to move and wear through the rad core with disasterous results.
You could do as Jaguar do and cut some slots in the shrouds, then fit rubber flaps, fixed /hinged along one long edge. In traffic the slots are covered and the shroud is sealed for best efficiency, then at speed the foward air motion forces opens the flap and gives you some through flow.
Matt
Matt
Well Mr GreenV8s, shpub etc...
I did some quick checking on the shroud thing and it seems that the cooling is approximately halved at standstill if you remove the shroud (we are talking american cars here). I looked at quite a few sites and the general consensus was that the shroud is essential in traffic.
I couldn't find any hard numbers, and you have to take what you find on the web with a pinch of salt, but it definitely seemed to suggest that you two are correct.
Rob.
I did some quick checking on the shroud thing and it seems that the cooling is approximately halved at standstill if you remove the shroud (we are talking american cars here). I looked at quite a few sites and the general consensus was that the shroud is essential in traffic.
I couldn't find any hard numbers, and you have to take what you find on the web with a pinch of salt, but it definitely seemed to suggest that you two are correct.
Rob.
I think we're talking at crossed purposes here. I don't for a second think the airflow is improved by taking the shroud off IF the fans are running.
In my cobra the fans come on only if I sit in traffic for a prolonged period >10 mins. Setting off again dramatically cools the engine and the fans switch off instantly.
In the TVR the fans are ready to come on the minute I stop as the engine runs between 80 and 90. The minute the cars stops the fans come on and occasionally the fans have come on even if I am going slow in the car! That would never happend in the TVR. I assume due to loss of RAM air effect.
All the america engines I have seen have conical ducts running back from the radiator to the fans. The TVR is just a flat plate which is a complete brake to ram air effect.
I wonder if Jools air induction kit improves cooling?
In my cobra the fans come on only if I sit in traffic for a prolonged period >10 mins. Setting off again dramatically cools the engine and the fans switch off instantly.
In the TVR the fans are ready to come on the minute I stop as the engine runs between 80 and 90. The minute the cars stops the fans come on and occasionally the fans have come on even if I am going slow in the car! That would never happend in the TVR. I assume due to loss of RAM air effect.
All the america engines I have seen have conical ducts running back from the radiator to the fans. The TVR is just a flat plate which is a complete brake to ram air effect.
I wonder if Jools air induction kit improves cooling?
Julian64 said:
I think we're talking at crossed purposes here...
I think you're probably right. The shrouds are there to improve cooling when the fans are on but they probably do reduce it slightly when the fans are off. My gut feeling is the effect will be very slight though, at least for the fan shrouds I've seen. What is likely to make a much bigger difference IMO is the shape of the ram air entry at the front, and how easy it is for hot air to escape out of the engine bay.
Julian64 said:
I think we're talking at crossed purposes here. I don't for a second think the airflow is improved by taking the shroud off IF the fans are running.
I know. I was just wondering wether taking the shroud off would have a noticeable effect in traffic, that way it would be safe to see if your original theory was correct. It seems I underestimated the effect it would have in traffic.
However I still think your original idea is correct. As an example, if you put a sheet of plastic across the back of the radiator (covering it entirely) then the cooling on the move would be ruined since there would be no airflow through the radiator, only around it.
It doesn't take a great leap to imagine that if half the radiator is covered it will have a detrimental effect albeit a lesser one.
Now if I understand you correctly you are saying the shroud covers a portion of the radiator rather than leaving a slight gap between itself and the radiator (as most do). I never bothered to look at the shroud on mine so I could be mistaken.
As a point of interest I think the engine is designed to run between 80 and 90 so making it cooler while on the move may not even be a good idea anyway (aside from the fact that the thermostat will stop the temp going below a certain level regardless of the cooling capacity).
joospeed said:
the induction has no effect on cooling, better or worse, but I see no problem with the current set -up, why should it matter if the fans are on when the car is moving slowly? if it's cooling the car that's ok surely?
I would have though that removing the front portion of the airfilter would now leave a dirty great rectangle blowing cold air under ram effect into the top of the engine?
ro_butler said:
Now if I understand you correctly you are saying the shroud covers a portion of the radiator rather than leaving a slight gap between itself and the radiator (as most do). I never bothered to look at the shroud on mine so I could be mistaken.
The shroud is a flat piece of plastic which is flat against the radiator and covers the WHOLE of the back of the radiator. There are only two holes in it for the two relatively small fans.
All air either ram or sucked 'by the fan' has to pass though these fans.
I should have taken a photo of this before I put it all back together again, Sorry.
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