Rad cap
20 October 2012, 09:28 PM
#1
Rad cap
Looking at changing my radiator cap but then I noticed there are different 'bar' ratings so wondering what is the significance of a high pressure radiator cap & which one should I go for?
EG: Cosworth have a 1.1, 1.3 & 1.5 bar
I am running WRX 2005 PPP
EG: Cosworth have a 1.1, 1.3 & 1.5 bar
I am running WRX 2005 PPP
21 October 2012, 11:36 AM
#6
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1.3 bar will be fine. You would only run a 1.5 Bar cap if you are running a high power motor which might push the water out with a 1.3 bar cap.
If you want a Cosworth cap we have them on special offer at the moment, but being a Sunday I can't remember how much they are!!
If you want a Cosworth cap we have them on special offer at the moment, but being a Sunday I can't remember how much they are!!
21 October 2012, 12:34 PM
#7
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With a two cap system (1 on rad and 1 on header tanker) the highest pressure cap should be on the rad so that any "normal" expansion takes place at the highest point in the system.(makes sure any trapped air is expelled)
On the later systems the rad cap is rated at 137kPa (1.37 bar) so running a 1.3bar rated cap on the header tank instead of the 1.1 bar standard one is fine.
On the later systems the rad cap is rated at 137kPa (1.37 bar) so running a 1.3bar rated cap on the header tank instead of the 1.1 bar standard one is fine.
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21 October 2012, 01:31 PM
#9
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Running a 1.5 header cap with the OEM 1.37bar rad cap means that all pressure release activities will take place via the rad cap and you are still only running the system at 1.37bar and not the 1.5bar you expected.
21 October 2012, 01:44 PM
#10
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Run with a 1.3 bar cap. If everything is ok then leave it alone. If you have a cap venting off then it's time to upgrade to 1.5 (providing you dont have any circulation/head gasket or thermostat issues!). That's only likely to happen in race spec engines.
In 99% of cases 1.3 bar is sufficient.
In 99% of cases 1.3 bar is sufficient.
21 October 2012, 05:02 PM
#12
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I'd assume that Subaru decided upon a 1.37 bar rad cap for a reason, and that is why they only supply a 1.3bar STi version header cap.
Running a 1.5 header cap with the OEM 1.37bar rad cap means that all pressure release activities will take place via the rad cap and you are still only running the system at 1.37bar and not the 1.5bar you expected.
Running a 1.5 header cap with the OEM 1.37bar rad cap means that all pressure release activities will take place via the rad cap and you are still only running the system at 1.37bar and not the 1.5bar you expected.
Run with a 1.3 bar cap. If everything is ok then leave it alone. If you have a cap venting off then it's time to upgrade to 1.5 (providing you dont have any circulation/head gasket or thermostat issues!). That's only likely to happen in race spec engines.
In 99% of cases 1.3 bar is sufficient.
In 99% of cases 1.3 bar is sufficient.
22 January 2013, 08:27 PM
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Sorry for the thread resurrection... 
On my Blob Sti, the standard caps are 108 and 137 kPa as mentioned. Presumably if I replace with a Cosworth 1.1 and 1.3 bar then it will be same as OEM more or less? No issues?
On my Blob Sti, the standard caps are 108 and 137 kPa as mentioned. Presumably if I replace with a Cosworth 1.1 and 1.3 bar then it will be same as OEM more or less? No issues?
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