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Just because it can see 27psi, doesn't mean its sealed. The plastic could be separating enough for small boost leaks to occur, which short term is not an issue, but if the conditions outside the car change enough, it is more than enough to put a tune out of wack and cause major issues.

I've run 30psi through an OEM MR16DDT intake manifold (also plastic). Did it hold up? Yea. Would I let anyone drive around like that if they didn't understand the risks? hell no. Uprev blew the threaded inserts right out of a nissan intake manifold in ~2013 by running 32psi through it.

Take into consideration how many heat cycles the plastic has seen, and how plastics get brittle with age, and eventually your gunna have a bad day XD

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I hear ya, personally wouldn't run 27 psi on 8740 arp studs anyways. unless I was running l19 studs you won't see anything over 24 psi without having coolant issues pushing through the head. It alot comes from turbo size too bigger turbo more air velocity. Example. Gt28 30psi isnt the same flow as a 6266 would be. If my tuner says 20psi is max, I trust him over joe anyday. hes tuned my car which is currently on 12 psi on 93 and the man knows his stuff worldwide tuner Martin from rs-enthalpy
Your correct about flow, but on the EXHAUST side. PSI is PSI. Your CFM of the turbo determines what you can push into the engine, yes, and how efficient you can maintain a pressure. But pressure is pressure. 28 psi is 28 psi is 28 psi weather the turbo is off a fork lift, a semi, or a sentra. The difference is how much heat and flow is behind that pressure, which is where power comes from with a larger compressor wheel. Less heat, more flow. So in regard to the intake manifold, cfm wont kill the manifold, it is just pressure. The added heat of a smaller turbo obviously does not help.

Say your blowing through a straw into a pressure gauge with a balloon on the end. your trying to pop the balloon. With a small straw, you have to push the air a lot harder to build the pressure to pop the balloon. With a larger straw, you do not have to push as hard, and the balloon pops sooner. It took X PSI to pop the balloons in both cases, or really X volume, one way was just more efficient than the other.

As for the head stud thing; I ran 24 psi on my qr with normal arp studs without issue. On the jukes I run normal ARP studs well north of 28psi. Shit, the 400 whp 28psi juke I built was on OEM Nissan Head Bolts. Same diameter as the qr ones (i had not sorted out what studs from arp fit at the time and said fuck it)
 

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not saying you shouldn't, I was more focused on the intake manifold thing, all i was saying in regards to the studs is that its not 100% required at a certain point. A lot of factors play into it.
 

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pin 87 on a relay goes to the thing you want to power on when the relay turns on. pin 85 is 12 sw+ and is how you signal the relay to kick on with low amperage power. Make sure that is a 35+ amp relay. If you are running 30A through it continuously and its a 30A relay, its going to get insane hot and possibly fail. Always go bigger on relays. Your going to want a 8 (at the smallest) gauge wire, and if the relay terminal doesn't have the same material volume as an 8g wire, then your going to have a hard time getting full amps through the relay itself.
 
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