<![CDATA[Stock FPR okay for boost?]]>I suppose the only way to get a definitive answer here will probably be to test it myself, but I thought I'd ask anyway.

I have to admit that , until my recent research into injectors, I never knew what the vacuum line on the fuel pressure regulator was even for, so I guess I'll explain it to make sure we're all on the same page and there aren't any details I'm over-looking.

The regulator itself is more or less a valve with a spring holding it shut. Fuel enters the regulator on one side of a diaphragm and the spring is on the other. Once the pressure reaches the set-point, the force pushing on the diaphragm is greater than the spring force. This causes it to move and opens the valve which allows fuel to flow out the return line.

fuelregulator.gif

This is all well and good, but the fuel injectors are located inside the intake manifold, not hanging out in free air. If the fuel pressure stays constant relative to atmospheric pressure, then the pressure seen at the injector nozzle will increase as vacuum builds in the manifold and decrease when the manifold is exposed to boost pressure. The vacuum from the intake manifold is connected to the opposite side of the regulator's diaphragm as the fuel pressure. As vacuum increases the valve is opened farther, and fuel pressure is kept constant relative to manifold pressure, not atmospheric pressure.

My initial thought was that the stock fuel pressure regulator was never designed to handle boost, and would have to be replaced. After learning how these things work, I can't see any reason why the regulator would perform any differently with boost pressure versus vacuum so long as the case can hold the pressure and something is done to keep the manifold reference line from popping off...

Thoughts? Hearsay? TL;DR?

]]>https://wibimmers.com/topic/5490/stock-fpr-okay-for-boostRSS for NodeWed, 16 Sep 2026 05:42:57 GMTSun, 25 Nov 2018 17:02:41 GMT60<![CDATA[Reply to Stock FPR okay for boost? on Tue, 27 Nov 2018 21:01:41 GMT]]>Thank you for properly understanding the fuel pressure regulator!

]]>https://wibimmers.com/post/96281https://wibimmers.com/post/96281Tue, 27 Nov 2018 21:01:41 GMT<![CDATA[Reply to Stock FPR okay for boost? on Mon, 26 Nov 2018 15:44:28 GMT]]>I did not like the overly complex M20 booster check valve at all. I ran a stock E21 check valve. Just putting that out there in case your M42 has a goofball double check valve like the M20 does

]]>https://wibimmers.com/post/96215https://wibimmers.com/post/96215Mon, 26 Nov 2018 15:44:28 GMT<![CDATA[Reply to Stock FPR okay for boost? on Mon, 26 Nov 2018 15:25:49 GMT]]>FPR is good to go as stated

Crankcase vent can be run with a catch can to the intake tract for the turbo, if not that vent it to atmosphere as nothing else will have vacuum.

Make sure you have a check valve in your brake booster line as well to ensure it doesn't see boost pressure.

]]>https://wibimmers.com/post/96212https://wibimmers.com/post/96212Mon, 26 Nov 2018 15:25:49 GMT<![CDATA[Reply to Stock FPR okay for boost? on Sun, 25 Nov 2018 22:05:37 GMT]]>

The Full Banana said:

Totally fine. Same style regulator was used on many factory turbocharged cars. 

snap said:

Can confirm: FPR and idle control valve are both fine with boost. Stock Crankcase ventilation/PCV layout is not however

Thanks guys. Glad that there's at least one thing that I don't have to worry about.

Crankcase ventilation is another one that I've been putting off thinking about...

]]>https://wibimmers.com/post/96200https://wibimmers.com/post/96200Sun, 25 Nov 2018 22:05:37 GMT<![CDATA[Reply to Stock FPR okay for boost? on Sun, 25 Nov 2018 18:42:43 GMT]]>Can confirm: FPR and idle control valve are both fine with boost. Stock Crankcase ventilation/PCV layout is not however

]]>https://wibimmers.com/post/96195https://wibimmers.com/post/96195Sun, 25 Nov 2018 18:42:43 GMT<![CDATA[Reply to Stock FPR okay for boost? on Sun, 25 Nov 2018 18:04:44 GMT]]>Totally fine. Same style regulator was used on many factory turbocharged cars.

]]>https://wibimmers.com/post/96191https://wibimmers.com/post/96191Sun, 25 Nov 2018 18:04:44 GMT