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4JB1 wastegate pressure????

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4JB1 wastegate pressure????

Postby magicdeo » Thu Dec 07, 2017 7:58 pm

Hi guys, a lot of people tell me that a stock 4JB1 runs 9 or 10 psi of boost but my manual says that the wastegate opening pressure is 757mmHg (14psi). Should it be 14 or is that just the maximum output?
Cheers
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Re: 4JB1 wastegate pressure????

Postby magicdeo » Thu Dec 07, 2017 8:08 pm

Also does anyone know the difference between a RHF4 and a RHF5?
magicdeo
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Re: 4JB1 wastegate pressure????

Postby geeves » Fri Dec 08, 2017 4:35 am

I wonder how many people have read the manual in that much detail. Ive heard the 10psi number before so many times but all 3 of the isuzus Ive owed ran 14 without any known of mods. 14 certainly does no harm
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: 4JB1 wastegate pressure????

Postby magicdeo » Fri Dec 08, 2017 5:27 am

Then why does everyone say 10? Some time back mine was at 14 and i figured the previous owner played with it so i took it back to 10. Maybe i should of left it? My turbo is a RHF5 but i got quoted for a new RHF4 which says it fits a 4JB1 97 - 2001. Mine is a 97 so i assume it will fit. Do you know the difference? My RHF5 doesnt come on boost until 2200rpm which i thought was suppose to be 1800?
magicdeo
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Country: Australia
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Vehicle: 1997 Holden Rodeo

Re: 4JB1 wastegate pressure????

Postby geeves » Fri Dec 08, 2017 9:20 am

Pass on first question
second change to 2.5 inch exhaust snorkle and a good quality air cleaner and low end boost will improve
Sanding your knuckles before starting work can help. That way you cant skin them
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