Fuel pressure?

phunk

^^^ and the white dragon is using a twin fuel pump assembly. in this circumstance its a requirement. An external regulator is required. The stock regulator is a part of the stock fuel pump assembly. With the twin assembly, its gone. And we didnt make a way to include it in the twin pump because it would be too small to handle twin fuel pumps unless you were to stage the pumps (activate the second pump only at high load).

Sam, youre not using a vacuum line on the regulator on that car are you?

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SAM@GTM

Of course it is...we're using a rising fuel pressure regulator, which has made it a ************ to tune. Keep in mind that the VVEL vacuum variation has a negligible affect on fuel pressure under vacuum, since the difference is only a few psi between low vacuum and high vacuum. Once you're in boost, that is no longer a concern and the rising rate fuel pressure regulator does what it needs to do.

BTW, your Twin Pump setup is doing its job very well.

Sam

phunk

Yes under boost it will surely work consistently. But its the low load cruising that made me decide not to follow through with building external regulator 1:1 ratio based fuel system kits for these cars.

What about under this circumstance as an example. And yes, I understand closed loop fueling SHOULD be able to handle this situation, but it still feels improper to me.

Say you are cruising down the tollway, and the VVEL is maintaining a 0/0 vacuum environment in the intake manifold. If you simply tap on the brake but do not lift throttle. The system instantly switches to throttle control and generates vacuum to operate the brake booster. But instead of holding on the brake, it was just a mere tap (for whatever reason). Now I know this test circumstance is more like searching for a inherent flaw than it is an actual driving condition... But, we have now created a situation where we have gone from no vacuum to engine load specific vacuum. The fuel pressure will instally drop due to vacuum, and then within a few moments it switches back to VVEL load control and fuel pressure will raise.

Like I said, I know thats a strange set of conditions and not very likely to occur in regular driving... but that set of circumstances alone was what told me that I cannot depend on the VVEL system to give me a consistent connection between actual engine load and manifold vacuum. I stopped trying to theorize other conditions where this could occur... but I certain there has to be some others.

But if the car seems to drive and cruise without issue regardless, then I suppose my concerns are exaggerated for the situation.

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phunk

That is good news. I figured it should work out as its based on the 350z twin design.

Build more crazy cars! I have a handful of those twin pumps with your name on them!!

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