Fuel Demand affected by Dry Sump?

[TheJet-09]

Looking for anyone's opinion or experience: Is it possible for the dry sump system on a sealed engine (one that is not vented to the atmosphere, only a breather on the oil tank itself) to somehow affect the fuel demand of the engine (under heavy load) versus an engine that is vented to the atmosphere (the old valve cover breather/s setup)?

Say if there were some "blow by" of the piston rings, not evident because of the engine being sealed, or even not enough to be noticed if it were vented to the atmosphere?

Thanks in advance!

[billetbirdcage]

Looking for anyone's opinion or experience: Is it possible for the dry sump system on a sealed engine (one that is not vented to the atmosphere, only a breather on the oil tank itself) to somehow affect the fuel demand of the engine (under heavy load) versus an engine that is vented to the atmosphere (the old valve cover breather/s setup)?

Say if there were some "blow by" of the piston rings, not evident because of the engine being sealed, or even not enough to be noticed if it were vented to the atmosphere?

Thanks in advance!

Pretty much NO (at least to where it was noticeable). Only way it could is if somehow it was causing the engine to pull more air thru carb as the carb is what is metering the fuel into the engine.

[Kromulous]

I always thought pulling a vacuum in the crankcase generated more HP, more HP i would think would use more fuel?

Seems plausible, but maybe some engine guys know.

[powerslide]

Drag guys are claiming 10-20-30-40hp increases in some cases but they are running vacuum pumps, not sure if you can get enough vacuum on just the dry sump to get the topend of those HP claims. If you could its likely you would need to rejet.

[billetbirdcage]

To be clear: I said a noticeable change in fuel usage, but I guess that depends on what you call noticeable?

Most increases in power you're gonna see, will fall into the 1 to 5% range in power added. So even if you go off a direct fuel usage off that power %, it's very minor least to me it is.

Most of the time you're gonna see around 2% or least to me that is the most common average number I see for circle track engines, but have seen a few closer to the 5% mark but your talking engines close to the 1000HP mark and drag engines.

[TheJet-09]

Thanks for the replies. My reason for asking was merely thinking outside the box, as I've struggled with an apparent fuel pressure/demand issue all year (only when the track is heavy). Without going over every change I've made (and looking back, I believe I created some problems unintentionally while trying to cure this one, which just delayed the final outcome), I was baffled at how last years engine (just an 18* 421, nothing fancy) ran just fine on a Carter fuel pump, yet the engine I have now (same size, but old Dart/Buick heads) will not, even though it had a Carter fuel pump on it when I purchased it.

The only outstanding difference in the two engines (yes, aside from heads) was last year's was vented to the atmosphere while this year's engine is not. I was grasping at straws in trying to find the cure.

[rakracing]

jet , the engine that's sealed up is there a vacuum pop off on the valve covers, was shur you needed that on a system with 5 stage pump, maybe your pulling to much vacuum

[TheJet-09]

Funny you should ask, as I failed to mention (or even think about) the fact I used a 4-stage pump last year but a 5-stage pump this year. But I believe yes, there is a pop-off valve. It has two "breathers" on the left hand valve cover. I replaced them and realized the one tube has a freeze plug blocking it off, and the other has something threaded down inside of it, which I believe is a pop-off valve, but have not taken out to confirm.

It was originally built by Rhyne, so I trust things were done right. And now having named the builder, I'll add that when it runs correctly (once corner speeds have gone down, like in the heats and feature), it is by far the best running engine I have ever had.