cooling pipe questions

[Paul Bristo]

Hi guys, in between prepping the moulds for the carbon tub i'm trying to sort the tunnel package and hope some of you more experienced guys can weigh in with some thoughts.

I plan to route the main cooling pipes and the rad air bleed line down the tunnel. first question, is this likely to be an issue with the bleed line being this low ? should I route it somewhere else so its always higher than the top of the rad ?

next question, pipe materials. I see stainless steel is a common choice, i'd like to go aluminium for the reduced weight, but am I missing some important factor? Also If I go Ali should I worry about coating/anodising it against corrosion ? The tunnel will be sealed underneath and the pipes will be well thermally insulated to protect the carbon tub.

last question, rad air bleed line, what approx min size should i plan for, and what material do people usually use ?

all suggestions gratefully received, cheers

 

[PAB]

aluminium pipes should be fine - Mclaren F1 roadcars use / used HE30 (not sure what the new equivalent is) - no problem 25 years later other than the anodising faded - not that you need to anodise. 5 or 6mm bore bleed lines are usually good - ptfe hose is good

 

[Terry Oxandale]

I used SS only so I'd never have a corrosion issue, and for the thermal reasons, but PAB makes a point. Then I had them Jet-Hot coated as well. Perhaps overkill, but I had very limited space to shroud the pipes with insulation, so I was looking at materials that presented the least heat transfer to the leg. Having these tubes low in the chassis was never an issue, but I was confused about your routing of air bleed lines. I've never used bleed lines (just air bleed ports at the high point at each end of the coolant system (front/rear) other than what may be on the block to tie the bleed ports for the heads, etc. Other than that, any overheating water is dumped behind the transaxle from the overflow reservoir.

 

[Howard Jones]

First. The air bleed system will have continuous coolant flow thru it. Any air in the system should be forced back to the header tank so routing isn't that critical. Straight lines are much better than a lot of 90-degree turns. I ran my bleed line down the top of the side pod and I used 1/4 inch AN-4 lines and fittings for all of the bleed system. The height of the side pods is not much different than the center of the tunnel so I think both would work fine.

As far as material selection for the coolant system. I really think you will be better served to use stainless steel for both the coolant pipes and bleed line in the center tunnel where it is difficult to get to. The bleed system smaller pieces in the nose and in the engine room are made up of stainless clad hose and AN fittings. The smaller pieces of the coolant system in the engine room and in the nose could be made from aluminum but if it was me I would use stainless throughout. The weight savings are so minimal that it just makes sense to do so.