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New efi guy question. On my LQ4 that I’ve turbo’d , I have the stock gm fuel rail with a feed and return and factory FPR with vacuum port built into it . I’ve also got the aeromotive boost reference fpr that I bought based upon reading I would need it since I run a walbro 450 in the factory tank and sender basket . Am I just going to use the factory one that’s built in and hook straight up to it, which would save me time and effort and I can finally prime and crank the motor. Or am I having to put that aeromotive one inline with the factory one ? I’ve heard conflicting answers that I need the aftermarket. And I’ve also heard since I’ve got a return rail system the factory one works perfectly fine. Sorry if this is a simole question to some of y’all but the only performance motors I’ve done before this have been carbed and non forced induction

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This is what my factory one looks like

Crf450r420

iTrader: (1)

Not sure if the factory one can raise pressure or not, but I'm certain it wasn't designed for it. You might be able to get away with it if you bought injectors to large for you desired power level, but if you sized them correctly or you plan on a lot of boost it won't work.

Injector flow works off of the pressure delta between the rail pressure and intake pressure on the other side of the pentle. Normal aspiration at wide open throttle there will be no vacuum in the intake and it won't pull on the FPR to lower pressure and this is the base. As you close the throttle and the intake is pulled into vacuum and the rail pressure doesn't change you then the injectors will flow more. If you go into boost and you don't raise the fuel pressure the injectors will flow less. This is why you would need oversize ones to run without a boost reference FPR.

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They are the SD 80lbs that a lot of guys are running.

Lsxford

iTrader: (6)

Didnt Denmah use stock regulator when he had 3 450s in the tank of his Colorado? I say try it out see what it does. I know hes using stock regulator now with just 1 450

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Yeah if I could use the factory stuff and just run 8an and 6an for feed and return to the factory lines it would be perfect and I wouldn’t need to find a place to mount this FPR and all the extra fittings needed.

kingtal0n

iTrader: (1)

I would try the OEM regulator. As long as it's rise rate is 1:1 with boost, it should work "fine". It depends how the inside is made (I can't see it and I've never had one so, guessing) but one thing that I could see happen is it may become a restriction after some power level (flow rate) due to it's small size (on the feed). The aeromotive regulator probably has much larger holes for fuel feed, or it may be designed more "conveniently" for fuel to flow. The return can all but be clamped shut on a full power run on all but the highest flowing fuel pumps; so it isn't really a concern for "making power". Its just the feed you have to be careful with.

Another possibility is that the regulator cannot return fuel to the tank fast enough for a high-flow pump. This would cause the fuel pressure to be unstable, and it will not be able to adjust down. The regulator can only open so far, and if that isn't enough, the fuel pressure is no longer under control.

You would be surprised (maybe) how much fuel a tiny regulator like that can flow, though. That is why I say try it. I bet that sucker can support at least 500 horsepower on gasoline. Just watch the fuel pressure on the rail as you raise power.

the only other thing is adjust ability, I like to be able to reduce my fuel pressure lower than factory. Way lower. It helps with fuel temperature, and will extend the life of the fuel pump, and helps if you have "oversized" injectors, I usually am running a low pressure like 35-38psi base.

Crf450r420

iTrader: (1)

He has to put more info about the goal here to get any real help other than to try it and see what it does, which he will have to do either way to really know what it does.

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Honestly I’m just trying to have fun with this truck and as I joke, I just wanna go fast enough that the track says don’t come back without a cage. My realistic power goals are 600-800hp range, figuring if guys are getting 500 with cam and valve springs and such I should be able to get 600. If I get 700 with tuning even better , and would be ecstatic to get near 800 for some bragging rights. But I’m not trying to win classes at the track nor trying to race on street. It’s just mainly a weekend driver that’ll fry the tires and pucker the ******* a little when you get into it.

Crf450r420

iTrader: (1)

With no pressure rise with boost you will be able to get around 800HP out of the those injectors, so as long as the regulator doesn't bounce all over dealing with the volume and can pull the pressure down at idle so the pulse with isn't to long at idle you should be okay. Still have to give it a try to check.