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Discussion Starter #1 (Edited)
Is there a place in the exhaust where both can serve there function?
Old school says to place the gulp valve at 45 degrees(180 from ground) at the start of the collector.
New school wants to locate the oxygen sensor further back into the collector atleast 90 degrees from ground level. Just some thinging about some possible conflicts for when I ditch the carb.
 

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My problem is will the crankcase vapors upset the O2 sensor located further down stream?
I would think so, but what do I know? :eek: Will it really make that much difference if you put the valve downstream of the 02 sensor?

Dan, the pan evac systems as we know them may be old school. While trying to find another name for your "gulp valve" I ran across a few more things I didn't know.

Why do race cars run a vacuum pump?
Where it all began, at least in the NHRA Sportsman ranks, was with the introduction of mufflers to the racing class. Once the cars started running mufflers traditional pan evacuation systems (pan-evacs) no longer worked properly.
One way is that as the crank spins in a partial vacuum, less air density means less resistance to rotation.

The proper amount of vacuum will improve ring seal. C&S research indicates you can have too much. About 10” to 14” of vacuum at 7000 RPM yields the highest power gains.
I don't know if you've researched these options or not but if you haven't you may want to.

Harold
 

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You can run a pan evac system with mufflers. We installed quite a few on Subaru drag cars, the trick was to drill a hole into the pipe, and hold the evac tube in place with the engine at a set rpm while on a lift. Then pivot the tube slowly and at some poiint you'll find the 'sweet spot' where the exhaust created the highest vacuum on the evac tube. You'll want a few degrees off from this angle, as too much vacuum means you'll over-draw the crankcase and oil down the track (blackflag!).

Bob
 

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Well things are moving along nicely. The 02 bung is in place and is working fine when a wide-band is installed. The electronic ignition(edis) has been rock solid for the last few months. I'm planning on only using the wide-band during tuning since it's going to running open loop all the time anyway.
Looks like its time to get the check valve installed to hopefully reduce the crankcase pressures there by helping out the ring flutter.

gulp valve1.jpg

I"m a very cheap person, that way I can spend the money where it counts. Ok the valve you can get at any parts store. They've been installed on most cars/trucks with smog pumps. This one I found laying around from a 84 vette of all things LOL. The short piece of galvanized pipe was cut at a 45 angle and striped of its outer coating. After cutting a hole in the collector of the proper size I'm going to tack weld. Then find the sweet vacuum spot and tip it a hair like was suggested from Bob.
 

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I'm planning on only using the wide-band during tuning since it's going to running open loop all the time anyway.
Glad I'm not the only one that tunes in open loop and leaves it there.
 

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personally I'm a big fan of using closed loop, especially when you have wide band input
closed loop on a stock engine is fine.
 

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Discussion Starter #11 (Edited)
Glad I'm not the only one that tunes in open loop and leaves it there.
Yeah all of my "hot tunes" are done in open loop.

personally I'm a big fan of using closed loop, especially when you have wide band input
For fuel mileage yep.
First I always force open loop fuel control.
Tune the base tables for a great foundation without the adaptive fuel control
mucking things up.
After the base tables are nice turn the adaptive back on.
Using the short and long terms adjustments to get closed loop mixture for fuel
economy. I like to give the adaptive a range of 25%.

Heres a picture of the spreadsheet for Fords.
LT_ST_fuel_corrections.jpg
 

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Discussion Starter #13
A little closer.
Got the rear vent welded up and painted.
No powder coating here.

 
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