Fuel Pressure Regulator

[Skeeve]

A vacuum regulator is not about richening at redline, it is about richening upon throttle opening....

A bottle would store vacuum so the vacuum will not drop instantly when the throttle is opened so that bulky set up would be of little value.

 

Counterpoints:

 

A) Sue me, I misunderstood the description of the functioning of the pressure regulator: my understanding was that it was intended to add fuel at high air flow rates, not low flow. My bad.

 

Evening out the pulses from the two cylinders by merging the respective signals into one average signal doesn't change the fact that the combined signal is still valid. Note that there's no delay as there would be w/ a flow restrictor, just a reduction in both frequency & amplitude, which were the faults listed with getting the signal direct from the vacuum bleeds. BTW, the bottle under discussion is pretty dang small, so I don't think your complaint about "bulky set up" is completely valid either, but yes, it will occupy some of the space under the tank.

 

Like I said, I've got a 2003, so this discussion is less than pertinent to me. I'm going to bow out now, & leave it to the '00-'02 guys...

[Guest ratchethack]

Note that there's no delay as there would be w/ a flow restrictor, just a reduction in both frequency & amplitude, which were the faults listed with getting the signal direct from the vacuum bleeds.

If I may counter your counterpoint without setting off another Great Wallopping Clusterfarge/Group Dork Wrap Around the ol' Driveshaft Contest, Skeeve, (not you, but, umm. . . others, y'unnerstan'. . . ) I b'lieve you've got this wrong WRT "no delay".

 

As Dan posted above, with the "dual mode" OE fuel pressure regulator, you'd need it to switch to "high pressure mode" INSTANTANEOUSLY upon opening the throttle -- otherwise, you're missing the most critical window of necessity for high fuel pressure, completely overwhelming any possible benefit of running in "low pressure mode" at idle.

running both intake manifold bleed nipples to a common "boost bottle" sized tank would go a long way toward evening out the pulses while maintaining full amplitude of the depression, I should think.

Setting aside running a vac bottle off the highly restrictive .030" dia. bores of the intake barbs, and assuming you could replace these with intake vacuum reference barbs of even 4-5 mm dia., how long d'you think it would take a relatively unrestricted flow of air to take a vac bottle from max intake vacuum at idle to drop below the 5-10 PSI vacuum regulator trigger point and cause the regulator ro jump to "high pressure mode" when the butterflies are suddenly whacked open? If it took long enough to result in one lean cough (or any kind of a hesitation), it'd be too long.

 

Don't know what size "boost bottle" you were thinking of, but FWIW, I'd considered using an old Weber OE fuel filter for a vac bottle (~300 cc) many years ago when I experimented by connecting the regulator vac reference to one of the intake barbs as mentioned above (effort level, less than a half-notch above ZIP, and no downside risk). But when I'd thought it through per above, I'd concluded in advance that plumbing in a vac bottle weren't worth any effort a-tall.

[emry]

Actually it is used to maintain a pressure differential across the injector. Total fuel flow through the injector is based on the pressure difference between the manifold and the fuel rail. Fuel mapping is set once the design (vented or mainfold based) and takes this into account. Models (most inline 4) use the manifold as a reference, twins and singles normally use baro. Due to pulses as mentioned before. If you mapping is set for Baro - don't change it. Like wise for manifold based. The effects are normally felt below 1/4 throttle. (For you butt dyno folks ) I'll let you folks debate as to why. Have fun.