Silicon Hoses - How much difference? Is the cost worth it??

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J

Jon

Guest
Whilst under the bonnet yesterday when I revved the engine hard
(Defender 200tdi) I noticed the rubber turbo hoses flexing.

Is this normal? The one that seemed to flex (expand) the most was the
bend on the pressurized side of the turbo. I'm guessing it expanded
probably 1 or 2 times the width of the rubber hose wall, perhaps 10mm
in total.

I couldnt see the hose onto the bottom of the intercooler - it was too
much faff to remove the air filter housing!

I think Ive read before that silicon hoses dont flex... This
**theoretically** would mean more pressure into cylinders.

Has anyone changed the hoses only and noticed any difference?? I
suspect most will change hoses, intercooler & tweak fuel pump...

Silicon hoses are not cheap and so wont change if theres no *real*
difference.

Thanks
Jon

 
Jon wrote:

> I think Ive read before that silicon hoses dont flex... This
> **theoretically** would mean more pressure into cylinders.


No MORE, but probably faster, because you are not spending time
expanding the walls of the tube until the forces in the wall can resist
the pressure. Stiffer tubes will have less pressurisation lag.

Steve
 
>> I think Ive read before that silicon hoses dont flex... This
>> **theoretically** would mean more pressure into cylinders.

>
>No MORE, but probably faster, because you are not spending time
>expanding the walls of the tube until the forces in the wall can resist
>the pressure. Stiffer tubes will have less pressurisation lag.
>
>Steve


Agreed - A point I had overlooked - Thanks.

As to whether Silicon hoses are worth the cost - I guess the cheapest
/ easiest way to find out is to buy a dozen 2" jubilee clips and
restrict my existing hoses. Maybe a job for the weekend!


Jon
 
Jon wrote:

> As to whether Silicon hoses are worth the cost - I guess the cheapest
> / easiest way to find out is to buy a dozen 2" jubilee clips and
> restrict my existing hoses. Maybe a job for the weekend!


Hmmm. Why not bind them with wire ?

Steve
 
> Whilst under the bonnet yesterday when I revved the engine hard
> (Defender 200tdi) I noticed the rubber turbo hoses flexing.
>
> Is this normal? The one that seemed to flex (expand) the most was the
> bend on the pressurized side of the turbo. I'm guessing it expanded
> probably 1 or 2 times the width of the rubber hose wall, perhaps 10mm
> in total.
>
> I couldnt see the hose onto the bottom of the intercooler - it was too
> much faff to remove the air filter housing!
>
> I think Ive read before that silicon hoses dont flex...
>

silicon hoses certainly do flex, more so than rubber ones.


 
SimonJ wrote:

>>Whilst under the bonnet yesterday when I revved the engine hard
>>(Defender 200tdi) I noticed the rubber turbo hoses flexing.
>>
>>Is this normal? The one that seemed to flex (expand) the most was the
>>bend on the pressurized side of the turbo. I'm guessing it expanded
>>probably 1 or 2 times the width of the rubber hose wall, perhaps 10mm
>>in total.
>>
>>I couldnt see the hose onto the bottom of the intercooler - it was too
>>much faff to remove the air filter housing!
>>
>>I think Ive read before that silicon hoses dont flex...
>>

>
> silicon hoses certainly do flex, more so than rubber ones.
>


It's not the silicone vs 'rubber' that determines the stiffness it's
what reinforcement is included. Silicon will give a higher temperature
capability but the 'burst' strength is purely a function of the
reinforcement. Silicone rubber is actually weaker in tension than
natural rubber and neoprene.

 
>>
>> silicon hoses certainly do flex, more so than rubber ones.
>>

>
>It's not the silicone vs 'rubber' that determines the stiffness it's
>what reinforcement is included. Silicon will give a higher temperature
>capability but the 'burst' strength is purely a function of the
>reinforcement. Silicone rubber is actually weaker in tension than
>natural rubber and neoprene.



So I'm guessing that the Silicon hoses are heavily reinforced to make
them "Superior" to the standard rubber ones? i.e. the reinforcement
doesnt allow them to flex? If not, whats the point in them?

Jon

 
Jon wrote:

>
> So I'm guessing that the Silicon hoses are heavily reinforced to make
> them "Superior" to the standard rubber ones? i.e. the reinforcement
> doesnt allow them to flex? If not, whats the point in them?


They sure look purdy.....

Steve
 

"Jon" <[email protected]> wrote in message
news:[email protected]...
> >>
> >> silicon hoses certainly do flex, more so than rubber ones.
> >>

> >
> >It's not the silicone vs 'rubber' that determines the stiffness it's
> >what reinforcement is included. Silicon will give a higher temperature
> >capability but the 'burst' strength is purely a function of the
> >reinforcement. Silicone rubber is actually weaker in tension than
> >natural rubber and neoprene.

>
>
> So I'm guessing that the Silicon hoses are heavily reinforced to make
> them "Superior" to the standard rubber ones? i.e. the reinforcement
> doesnt allow them to flex? If not, whats the point in them?
>

They look pretty!

I think they can take higher temp than rubber hoses (I know on the HGV's I
work on often as not it is a silicone hose from the turbo to the
intercooler, and the rest are rubber)
Also they have a smoother surface so less restrictive to the airflow, but I
don't think you'd notice the difference on the average land rover!!


 

"Jon" <[email protected]> wrote in message
news:[email protected]...
> >>
> >> silicon hoses certainly do flex, more so than rubber ones.
> >>

> >
> >It's not the silicone vs 'rubber' that determines the stiffness it's
> >what reinforcement is included. Silicon will give a higher temperature
> >capability but the 'burst' strength is purely a function of the
> >reinforcement. Silicone rubber is actually weaker in tension than
> >natural rubber and neoprene.

>
>
> So I'm guessing that the Silicon hoses are heavily reinforced to make
> them "Superior" to the standard rubber ones? i.e. the reinforcement
> doesnt allow them to flex? If not, whats the point in them?
>
> Jon
>


Ability to withstand higher temps is the reason for silicone - the after
market silicone turbo hoses offer a performance advantage ( doubtful if you
will feel it underfoot ) by being made with less expansion under pressure.
This ccould just as easily be done with rubber hoses so the performance
issue is not in the material but in the construction.
It is quite normal for the hose off the turbo to be silicone because of
the heat and the rest to be rubber.
Silicone also lasts longer before it gets all wrinkly and brittle....

The best way to reduce any expansion in any intercooler / hose application
is to have as muuch solid pipe as possible ( plastic / ally ) and use
flexible joiners only, keeping them as short as possible......


David
LLAMA 4x4
www.motorsport-plumbing.co.uk
www.llama4x4.co.uk



 
Don't forget that perished rubber hoses do tend to clapse under the vacuum of the turbo. Silicon hoses don't delaninate like rubber and hense will last longer, look better & not expand under pressure like the std hoses.
 
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