Bill - I certainly didn't meant to come off as high and mighty at all. Last I checked though, I also had built several fast Subarus (about 30 sup to nuts customer cars ) as well as a fairly quick EJ20 equipped 2.5 RS myself (11.88@118 on pump gas). Does that make me an authority? Nope, never professed to be one either. Does it make me know what I am talking about? Absolutely. And unlike JC sports, we are still in business and would never sell something for the sake of it being sold.
In any event, here is my rationale:
1. I think the fuel pump upgrade is a worthwhile one on a car that requires it (i.e. higher flowing turbo or much increased boost pressure). From personal experience, if the Lehacy 2.2 T pump is in fact the same as a WRX unit, it will flow 133 lph, which should get us nicely to around 300 or so crank hp. Will a Wlabro or Supra unit do it too? Sure will...so I am not fighting you on that one at all. want an easy way to see if you are out of pump? Hook up a fuel pressure gauge.....go out for a run. If at WOT under full boost (whatever boost that might be), if fuel pressure drops as you approach redline, a bigger pump is a good idea. If it doesn't you have yet to reach the limits of the existing pump.
2. Even in a bypass system, we have found some form of fuel controller a worthwhile additionl to a fuel pump upgrade. Simple reason is that though the IPW will be the same as before, the pure volume of fuel now being fed to the injectors will be much higher (in the case of a Walbro or Supra TT unit, they flow roughly 2x the volume what a stock pump would). As such, an aftermarket fuel computer would allow us to slow down IPW a tad to compensate.....this really only comes into play in the upper rpms. At lower rpms(example at idle), IPW should not be affected much at all, simply because they are barely opened in the first place. But in the uipper rpms at higher boost levels, you might find the need to lean it out a bit as it might be excessively rich. I speak from experience on many WRX's, and Turbo's 2.5 RS's. I would suspect the same holds true for a Legacy. Now compund that richer mixture (not a bad thing mind you, again, especially if you want to run higher boost l
In other wordsm if on a factory turbo car, you find the only way to maintain safe EGT's and nice rich mixture (call it over .90 on an O2 voltage meter) is with a 2:1 or more fpr, then it is time for bigger injectors. Does that mean a 2;1 unit won't work? Of course it will....but working, and being the right part for hte job are different stories which is all I was pointing out
As for the hoodscoop, I am certainly all for it if you are so inclined. I realize the benefits and rationale of the larger scoop, but simply find it unecessary on most street driven Legacies that's all. To each his own.
Lastly, you are correct, your piggybacked fpr won't affect fuel pressure at idle. What affects fuel pressure at idle though is your pump...again, my supplying far more volume than the OEM pump, you are now asking the stock fpr to work harder and bypass more fuel than it originally was intended to bypass back to the tank while mainting OEM base idle pressures. manyc ars can handle a pump with double the flow without ill effects (a WRX is one of them); manyc ars cannot (a DSM is a perfect example). Again, a simple test will reveal if a better fpr is in order: measure base pressure at idle, vacuum line off, with the stock pump, and make sure it is within factory specs. Now install your new pump and perform the same test. If your FPR is up to the task, fuel pressure at idle will be unaffected. If it is now inadequate, base fuel pressure at idle will now be higher. Big deal? Maybe not, depends how much higher it now is. On some DSM's for example, b
Adam
Z-1 Performance
www.z1auto.com
(631)254-8277
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