Specifically plumbing of automotive applications using stainless braided hoses. I’ve been working with braided hose for the best part of 30 years and therefore feel that I have a bit of knowledge that I can impart to the MFUK massive.
Nothing looks better than an engine bay glittering with Stainless-steel braid and anodised aluminium fittings (in the colours of your choice). The hoses are reliable, pressure and heat resistant and aesthetically pleasing, but how to go about achieving that look without disappointment?
Firstly, and possibly most importantly, there are many different qualities of braided hose. Mostly the hose supplied by the major manufacturers (Goodridge, Aeroquip, Speedflow, Gates etc.) is of reasonable/good quality, but beware of some hose that comes from speed shops and from the internet auction sites. Just recently a customer of mine bought (cheap) braided hose from Jegs and the quality was appalling. Hosing is definitely one area that you want to buy on quality not price.
Having chosen your manufacturer, you then need to establish what you need the hose for: If it’s oil systems or coolant systems then the ‘standard’ rubber braided hose is fine, but (despite the fact that 1,000’s still use it) the rubber braided hose is not good for modern fuels. The molecules of modern unleaded and the additives therein will permeate the walls of the hose and give off a strong fuel smell (particularly if the car is kept in a closed garage). People have been known to spend thousands chasing the fuel ‘leak’ before asking a hose expert.
So for fuel you will need to use a PTFE hose (or ‘Teflon’ hose) with the appropriate fittings. The hose ends for the PTFE hoses are not the same as for rubber hose and will not seal properly if you attempt to use them.
If you are plumbing a car with braided hose I’d suggest the following sizes & hoses:
Oil Cooler/Filter remote: -10an minimum (5/8” or 16mm bore). Rubber braided hose is fine, but make sure it’s a double-reinforced hose as the cheaper hoses have a habit of bulging and leaking.
Engine breather: -12an minimum (3/4” or 19mm bore) per bank. Rubber braid is fine. For race applications this needs to vent to a catch-tank (minimum 1 litre for smaller engines, 2 litre for larger ones). Many racers use -10 size for this (5/8” or 16mm bore), but with big V8’s I think the flow rate is marginal.
Fuel: From pump to fuel rail = -8an minimum (1/2” or 12.5mm bore). Most modern vehicles are plumbed as standard with 3/8” or 10mm bore hose. If you’re re-plumbing then go up a size just in case you ever need to uprate the power and therefore fuel flow. It may cost just a few extra $$$ but it will be future-proof.
From tank to pump (if using an external pump) use a size larger than the post-pump hose.
Transmission Cooler: no need to use any larger than a -6an (3/8” or 10mm bore).
Coolant: For heater hoses, most vehicles will use -10an (5/8” or 16mm bore) or -12an (3/4” or 19mm bore). The largest hose that most manufacturers make is -20an (1-1/4” or 32mm bore) which is probably a bit small for top/bottom hoses, though a lot of drag cars are plumbed with this as the cooling isn’t as essential as on road/roundy cars.
Power Steering: High pressure hoses are usually -6an (3/8” or 10mm bore). Due to the pressures and pressure spikes in PAS systems the ‘normal’ rubber braid will not work in this application. If you try it you’ll find the ends blow off the hose. PTFE hose is the only hose that will work with the pressures/ spikes involved. Good quality -6an rubber braid has a burst pressure of 6000psi whereas Teflon braid in the same size is over 10,000psi.
Return/Feed for PAS are usually -6an (3/8” or 10mm bore) and -10an (5/8” or 16mm bore) respectively. These can be the rubber braided hose as the pressures involved are minimal.
Brakes: Usually plumbed in -3an (3/16” or 4.5mm). These are always plumbed in the PTFE hose (burst pressure of almost 13,000psi). For road applications a lot of countries are now insisting these use crimped hose ends which have to be made by a ‘professional’ (read ‘someone who has a crimping machine’) and be tagged with the safety tag of the appropriate country. For years the self-assembly hoses have been fine, but with the blame culture that has arisen worldwide the hose suppliers can now be held responsible if the self-assembly hoses cause an accident. Stupid, but there it is!
Also, don’t use aluminium fittings/adaptors for braking systems as they have a habit of breaking off at the most inopportune times…..
Hose Ends and adaptors: Just about all manufacturers produce hose ends in all sizes in straight, 30deg, 45deg, 60deg, 90deg,120deg, 150deg and 180deg. Screw in adaptors for most applications come in straight, 45 and 90 degrees, and there are now adaptors to convert standard ‘clip-on’ hose fittings to the anodised AN hose ends. As with the hose there are a myriad of different hose end qualities, but as a personal preference I will always use hose ends that have large wall-thickness swept bends (as opposed to the forged angular fittings) as flow rates will always be better. They will also generally be more expensive, but you get what you pay for.
Legality: Road legality and competition legality are two different things, but it makes sense to build to the best safety standards.
If you are running hoses through the car for motorsport they must be either a metal pipe, a metal braided hose, or encased in metal for the complete run of the hose. To me this makes sense for a road car too. There are nylon braided hoses available that have the same pressure/temperature ratings as the Stainless braid, but these are currently NOT LEGAL to run through the car.
All hoses should be securely clipped every 300mm (12”). This is a requirement for road cars already, it’s not yet a motorsport regulation but it will be!
Common sense dictates that the hoses need to be away from likely contact with moving components or the road. Use bolt-through bulkhead fittings wherever the hoses need to pass through the bulkheads or floors. I don’t like holes drilled with hoses passing through rubber grommets as they don’t seal that well (particularly if the hole has been drilled large enough to get the hose-end through), they tend to break the grommet and rub through, and it’s also a royal PIA to change the hose if you need to.
Aesthetics: Applying the old adage of ‘if it looks right it probably is’, when you’re plumbing your car make sure you have enough hose to get nice, swept bends in it that follow the flow of chassis/panels. The larger AN sizes of quality hose do not take kindly to sharp bends so you will need to allow for the larger bend radii. To plumb your whole car will cost in the region of $8000 so don’t skimp. It’s better to buy ½ metre too much hose and have it spare than to get 100mm too little and make the job look botched.
Experts: The world is full of them. I deal with the public and professional race teams in equal measure and I am constantly astonished by the lack of knowledge on this subject that even the most established professionals exhibit.
If you are contemplating using a professional to plumb your car for you PLEASE ask questions before you go ahead – What hose will you use for which application? What make of hose and fittings will you use? Are you familiar with the safety/road regulations? Are those cheap Chinese fittings really the same as Aeroquip?
I’m happy to answer any questions.
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