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Braided injector pipes


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When I changed over from Nylon to Braided Hoses I did not notice any difference with concern to starting the engine. But this goes back to around 1992, but I do not know how today this hoses behave with the modern fuels... ;)

I can only agree with earlier posts speaking about pressure retaining capability of the system as any decrease will prevent injectors to open in so far will require additional cranking to fire the engine.

 

Today with the EFI I have little concern about this fact as injectors are triggert by electric current and not by fuel pressure.

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  • 3 years later...

Hi all ,am rebuilding tr6 currently and am about to mount shell to frame .I read with interest regarding braided fuel hoses apposed to nylon originals .I prefer the look of the braided type but take on board poss issues re longer to start and evaporation? Reading Nigel Triumph April 2017 .I agree simple maths regarding volume of fuel greater time to fill the hose. I struggle to think the steel braid would become hot enough to then evaporate fuel within ? Yes steel is a conductor of heat but rubber inner is an insulator? Just not sure what way to jump braided or nylon ? Is there anyone who has braided hoses and all ok ? Any help would be appreciated    Darryl 

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I have the braided hoses and have had no issues and I live in a hot dry environment. I dont notice too much issue with starting time. If the car has been sitting for a while then it takes a little bit of cranking but nothing to bad. I think some of the time the extra cranking might be due the battery having drained a bit.

 

Simon

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When I builr my other car, a Dax Rush (Se7en kit car) with a 5 Litre TVR (RV8) V8 EFI system, I used SS braided hose with rubber inner pipe for feed and return for the whole car's fuel lines. 8mm dia to match the fuel rail's inlet / outlet connections. That was circa 10 years ago. The car is only used in the summer so sits on blocks for winter with fuel in tank / lines.

I have had no problem at all.

Granted mine is not a PI Lucas system and having read all posts I'm not clear on why it causes the starting to have problems. I'm refurbishing my TR6 and plan(ed) to use the same again for the whole (non) Lucas PI injection system fuel lines that uses 8mm fuel rail connectors.

I cannot actually see why a SS braided hose would not work the same as anyother hose (ignoring splitting, etc.). Is it the throughput of the fuel pump not being enough? After all the rubber tube inside the SS braiding does slightly increase in dia but doubt that makes a difference.

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The issue, as I understand it from an article written by the late Robert Johnston in New Zealand, is that unlike the original stiff plastic hoses, SS/rubber hoses expand a small amount with the pressure pulse thereby absorbing energy. Therefore the pulse that arrives at the injector is weaker. He did many hours of testing and concluded Triumph had it right in the first place.

There is another potential downside to SS hoses, if your earth strap connections are not up to scratch then the current will find another way back to the battery. Throttle and choke cables have been known to be damaged this way, so a nice shiny SS fuel hose does not sound like a good idea for a conductor.

Mick

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I changed mine to braided about 3 yrs ago after a couple of the originals started to leak. So far there has been no issues starting. 

If the car has been laid up for a few weeks I've always had to let the pump run for a short while before starting even with the original plastic pipes.

The one 's I fitted were from Revington's which I believe use a non rubber inner (teflon I think)

Brian

 

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2 hours ago, BlairP said:

A propos to this subject, I am considering fitting braided stainless brake hoses to my TR6. Is the same issue evident with them? Better to rest with originals? Thanks, Blair

 

Triumph knew what they were doing, stick with originals and save your money.

Stuart.

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The exact spec of the Pirtek tube I can't recall.

One of the guys in the Leicester group who worked for Pirtek at the time reassured me that it was petrol safe and capable of taking way more pressure than it would be subjected to in the Lucas application.

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10 hours ago, stuart said:

Triumph knew what they were doing, stick with originals and save your money.

Stuart.

Yep, Alec nailed it above back in 2017 - nope, keep your bling. Anyway, braided hoses do not translate the pulse so how do you tell if an injector is not firing correctly, remove them all and check them individually? 

Cheers, Andrew 

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23 hours ago, stuart said:

Triumph knew what they were doing, stick with originals and save your money.

Stuart.

I fitted s/s braided PTFE hoses to my TR brake lines, 15 years ago, but they were Aerospace grade. Never had any trouble from them and they have been subject to temps of over 35C+!

Bruce

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58 minutes ago, astontr6 said:

I fitted s/s braided PTFE hoses to my TR brake lines, 15 years ago, but they were Aerospace grade. Never had any trouble from them and they have been subject to temps of over 35C+!

Bruce

I think the point is brake fluid needs to get a bit hotter than petrol before it boils.

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19 minutes ago, Mike C said:

I think the point is brake fluid needs to get a bit hotter than petrol before it boils.

I have renewed my injection fuel lines with the original black nylon 66 tubing which is resistant to the current fuel formulae? It is not as good as nylon 12 which is fully resistant to ethanol fuels of any percentage. But nylon 12 is difficult to obtain in the UK but not in the USA. but I would not use s/s braided fuel lines as I like to be able to feel the pulsing action to check the operation of the injectors which you cannot do with s/s braided fuel lines?

Bruce.

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Purchased our 1972  2.5PI in 2011 which was fitted with braided injection lines. One of the lines (#4) was showing chaffing, so had it replaced. Used   thinkauto.com  to make up a new one.   Invoice shows PTFE smooth bore tubing used. Never had a problem in starting. I do however have a hi-torque starter motor fitted.   Have done about 14K enjoyable and trouble free miles since purchase of the car.

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On 11/22/2020 at 9:36 AM, Mick Forey said:

The issue, as I understand it from an article written by the late Robert Johnston in New Zealand, is that unlike the original stiff plastic hoses, SS/rubber hoses expand a small amount with the pressure pulse thereby absorbing energy. Therefore the pulse that arrives at the injector is weaker. He did many hours of testing and concluded Triumph had it right in the first place.

There is another potential downside to SS hoses, if your earth strap connections are not up to scratch then the current will find another way back to the battery. Throttle and choke cables have been known to be damaged this way, so a nice shiny SS fuel hose does not sound like a good idea for a conductor.

Mick

I do not know the Lucas PI system so assume there is no fuel rail with the pump feeding it and a return plus pressure regulator to the tank so possibly understand the reason. Normally EFI fuel pumps are continuous whereas carb pumps only pump when triggered. Continuous feed would avoid the problem.

Fo me (and I am fitting an EFI with fuel rail) I'll use SS braided fuel pipes for feed and return as I have before (on non TR) cars.

As for SS braided brake pipes, they had to be fitted on my two (non TR) cars to be flexible from chassis to moving wishbone suspension and wheel steering. Absolutely no problems over 20+ years. Again I'm planning to use SS braided brake pipes in my restoration allowing me to route pipes much better. Easy to join too with Goodridge style compression connectors.

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14 hours ago, Richard Pope said:

I do not know the Lucas PI system so assume there is no fuel rail with the pump feeding it and a return plus pressure regulator to the tank so possibly understand the reason. Normally EFI fuel pumps are continuous whereas carb pumps only pump when triggered. Continuous feed would avoid the problem.

Fo me (and I am fitting an EFI with fuel rail) I'll use SS braided fuel pipes for feed and return as I have before (on non TR) cars.

As for SS braided brake pipes, they had to be fitted on my two (non TR) cars to be flexible from chassis to moving wishbone suspension and wheel steering. Absolutely no problems over 20+ years. Again I'm planning to use SS braided brake pipes in my restoration allowing me to route pipes much better. Easy to join too with Goodridge style compression connectors.

The thing with braided injector pipes on Lucas PI is they run over the top of the engine from metering unit to injectors so can suffer heat soak.

Stuart.

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50 minutes ago, stuart said:

The thing with braided injector pipes on Lucas PI is they run over the top of the engine from metering unit to injectors so can suffer heat soak.

Not only the soak from radiant heat and convection, but they conduct heat really well along the pipes back from the hot intake manifold. The heat soak is less of an issue when running, as there's a constant flow of cool fuel (and the narrower the bore, the less time the fuel spends in the pipe BTW), but more of a problem when the car is stopped. Not always a show-stopper (as some on this forum have noted), but it's just one more thing to make a not-quite-perfect injection system behave badly. And why introduce a potential problem if you don't need to? If you want bling, go for red pipes!

JC

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  • 2 months later...
On 11/24/2020 at 3:04 AM, astontr6 said:

I have renewed my injection fuel lines with the original black nylon 66 tubing which is resistant to the current fuel formulae? It is not as good as nylon 12 which is fully resistant to ethanol fuels of any percentage. But nylon 12 is difficult to obtain in the UK but not in the USA. but I would not use s/s braided fuel lines as I like to be able to feel the pulsing action to check the operation of the injectors which you cannot do with s/s braided fuel lines?

Bruce.

Here in the US you can get 100 ft. of Nylon 12 tubing in a multitude of colors for under 20 USD.

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Kenrow after a 5 second look on the internet i found this company in Uk sellling 12Nylon and its not expensive here either

 

https://www.advancedfluidsolutions.co.uk/5mm-od-x-3mm-id-metric-nylon-pa12-tube-red-flexible-tubing-bs5409--din-73378-5547-p.asp

Though your price is about a third cheaper than ours!

 

Edited by michaeldavis39
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13 hours ago, michaeldavis39 said:

Kenrow after a 5 second look on the internet i found this company in Uk sellling 12Nylon and its not expensive here either

 

https://www.advancedfluidsolutions.co.uk/5mm-od-x-3mm-id-metric-nylon-pa12-tube-red-flexible-tubing-bs5409--din-73378-5547-p.asp

Though your price is about a third cheaper than ours!

 

Michael,

I've also been looking at the AFS piping, one issue that has stopped me buying it is their size range.

I think you need to replace the Nylon piping with the same Internal diameter pipe as Lucas/Triumph used originally, or over time you could risk getting fuel leaks on the fittings.

An original injector pipe is 3.8mm ID and 6,6mm OD  ( as best measured on my diy vernier). This is 0.260" OD and 0.150" ID.  Wall thickness is 1,4mm (0.055").

This correct size is not currently available from AFS.

Bob

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19 hours ago, OldBob said:

An original injector pipe is 3.8mm ID and 6,6mm OD  ( as best measured on my diy vernier). This is 0.260" OD and 0.150" ID.  Wall thickness is 1,4mm (0.055").

I wonder if it's actually 0.25" OD, 0.15" ID? Megaflex list that exact size on their website. Makes sense that it's an imperial sized tube, but that's still no guarantee it's the correct size. I do like the idea of pink injector tubes!

John

Edited by JohnC
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  • 1 month later...

Nylon 12 is commonly labeled as DOT Nylon Tubing here in the USA. If going above 5/16" OD the tubing must be braided (Type B). Its primary use is in truck air brakes. 

Be aware that while, Nylon 12 does have better chemical resistance than Nylon 66, the tensile strength is lower and the melting point is lower. 

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