PCV system delete pros and cons - Page 2 - TCCoA Forums

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post #31 of 41 (permalink) Old 01-07-2017, 02:53 PM
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Originally Posted by twin turbo 281 View Post
It would only be an unmetered leak out of boost.
Correct, as long as the PCV valve seals correctly.


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Originally Posted by twin turbo 281 View Post
Also the Pcm I believe does not use MAF input under WOT conditions anyways?
Incorrect.


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Originally Posted by twin turbo 281 View Post
Either way I never had an issue running a PCV that way even untuned. I ran a breather when the engine was mostly stock as well and never had any problem. When I was running the PI motor with the small turbo I did however modify the MAF and installed larger injectors to incorrectly richen AF as I never got into tuning in those days.
That says it all.

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Originally Posted by twin turbo 281 View Post
I still don't understamd why it could not be compensated for unless the software you are using has limits on adjustments to the file. Some tuning software has no interlocks and you have full control.
As said above, you can "fudge" things to keep things reasonably close, but you can't get around the fact that you're introducing unmetered air. It isn't right.


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Originally Posted by XR7-4.6 View Post
You can run the car without a MAF at all if you wanted to, running purely off of the tables, with no feedback, it'll work just like a carburetor. Yes it can be compensated for in tuning software to an extent, but asking any repudiate tuner to dial in your car with a vacuum leak and you'll get the same look of bewilderment from them as you would asking a shop to align your car without fixing the tire leak. You don't fix a problem by trying to make the problem work.
Bingo #2.

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post #32 of 41 (permalink) Old 01-07-2017, 03:34 PM
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Even if the PCV valve did not seal it would be a very small boost leak. You can also add another check valve in the PCV to intake line. I had a question mark after the MAF question as I was unsure. I have yet to tune anything that uses a MAF. I had only read on some older information back in the day that the MAF was ignored as things were happening faster than a MAF could feedback input to the pcm. Again it may not be right but will work and did for me even untuned. I'm also not talking about asking a reputable tuner to dial in your engine with a unmettered leak. Many tune thier own combinations. Also I as a customer if getting custom tuning done and paying good money were to ask a tuner to compensate for this or that and they were to look at me strange I would pack up and find another tuner. I have personally known reputable nationally known tuners who will do what it takes to make a combination work even of they would not do it that way.

Again just my opinion and experience. I have used software to compensate for all sorts of changes on PCMs PLCs, CNC, and other automation controls.

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Last edited by twin turbo 281; 01-07-2017 at 03:44 PM.
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post #33 of 41 (permalink) Old 01-07-2017, 04:42 PM
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Anyone with the capability and knowledge to tune their own combinations should be aware of the flaw and futility of this endeavor, an unmetered vacuum leak is a completely unnecessary and defeating variable to tune around when your primary objective is to simply make the car run right using the measured scientific data given, not assumptions and anecdotes. I know tuners who will tell you straight up that your car will be a pain in the ass to tune unless you change this, this, or that, wise ones indeed will turn you away just to avoid the potential hassle of an unsatisfied belligerent customer whose combination was, as suspected, an unnecessary pain to tune.

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post #34 of 41 (permalink) Old 01-07-2017, 04:51 PM
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Quote:
Originally Posted by racecougar View Post
Will you be running draw-through or blow-through?




That setup equates to an unmetered air leak. Air is drawn through the breather, through the crankcase, and into the plenum via the PCV valve without being metered by the MAF. Sure you can fudge things in the tune file, but it isn't correct. Either run a OCV system or a CCV system, not half and half.
Draw-through, I'd understand in a blow-through set up I'd have other issues such as fouling the MAF if I ran PCV before it. (??)

I see some good suggestions and other suggestions that create more questions. Since you seem to know how the PCV system works, what do you suggest?

I'm thinking either, stock PCV setup with a catch-can with the PCV routed to the SC inlet or I put breathers on the PCV, I really don't wanna do breathers though.
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post #35 of 41 (permalink) Old 01-07-2017, 06:37 PM
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It's really hard to model a vacuum leak: With a fixed leak area, the leak volume is proportional to the pressure across it, the humidity, and the barometric pressure; and it's nonlinear.

You don't know what the vacuum level is, so you have to guess, and the barometric pressure/humidity relationship is based on that guess, and you have to model a fueling response based on those guesses; so that makes your mix at any given time a third-order guess relationship, and that will never fucking work.

Enough time and effort could model the response for a given leak for a drag run, changing absolutely nothing on the car, but it would take months to tweak. And fail if the weather wasn't close to the same.

And if the leak area changes any, every assumption you made is now wrong.


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post #36 of 41 (permalink) Old 01-07-2017, 07:23 PM
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Not to say it's the correct way. However it could work as many have done it including me. If my setup ran fine untuned it would likely be even better had it been tuned. In a draw thru application it is not an issue as you can have the line plumbed after the MAF. However on a blow thru you cannot. Unless you run a bunch of check valves and a check valved external vent along side the standard system to alow the crankcase to vent pressure when boost pressure has forced the PCV and breather line check valves closed. As the way I had it under boost when fueling is most critical there is no unmetered air as the crankcase is vented to atmosphere.

Most are not running a blow thru MAF here anyways unless they are running a Centrifugal.

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post #37 of 41 (permalink) Old 01-07-2017, 08:06 PM
No, Mr. Lemmywinks, No!!!

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I'm just saying that by not having it predictable, you're obviously running rich enough that all your parts are remaining in the engine, over variations in weather.

That leaves an enormous amount of power on the table; you could pick up 25% in the really bad spots.

That's the only reason I mention it; I bet any of our racers might trade a relative for 25%...

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
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post #38 of 41 (permalink) Old 01-07-2017, 08:35 PM
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Quote:
Originally Posted by ikutoisahobo View Post
Draw-through, I'd understand in a blow-through set up I'd have other issues such as fouling the MAF if I ran PCV before it. (??)

I see some good suggestions and other suggestions that create more questions. Since you seem to know how the PCV system works, what do you suggest?

I'm thinking either, stock PCV setup with a catch-can with the PCV routed to the SC inlet or I put breathers on the PCV, I really don't wanna do breathers though.
You have a couple of options:

1) Go OCV, either with breathers on the valvecovers or route both to a catch can. It's cheap, you'll have no oil-laden vapors entering the air charge, but you loose the benefits of CCV.

2) Keep it CCV by routing the fresh air side of the system to a location between the MAF and the blower inlet and the oil-laden side (PCV valve side) to the inlet plenum. Without any oil separator(s), you will get some oil-laden vapor in the air charge. Adding a good separator to the PCV valve side will protect you while in vacuum. Adding a good separator to the fresh air side will protect you while in boost.



TT281: Just because you can, doesn't mean you should. Running with a known unmetered air leak, injectors that don't match the profile in the tune file, and an uncorrected tune file to boot is a disaster waiting to happen and is not good advice to pass on as "hey this works". It would be bad enough in a NA application; the scenario is only compounded by the fact that we're talking FI here.

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post #39 of 41 (permalink) Old 01-07-2017, 10:15 PM
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Keeping the CCV is the way to go. I'll do the separators. I don't wanna do it the cheap way, cause there are benefits of CCV that I feel are necessary to the life of the seals and what not.

Also people saying the MAF is ignored at WOT, that's so untrue, it's probably the most critical at mid-high throttle stage. MAF is a super critical EFI component, really can't do a self-tuning EFI without some sensor that detects air intake.
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post #40 of 41 (permalink) Old 01-07-2017, 10:34 PM
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Quote:
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Keeping the CCV is the way to go. I'll do the separators. I don't wanna do it the cheap way, cause there are benefits of CCV that I feel are necessary to the life of the seals and what not.

Also people saying the MAF is ignored at WOT, that's so untrue, it's probably the most critical at mid-high throttle stage. MAF is a super critical EFI component, really can't do a self-tuning EFI without some sensor that detects air intake.
Sure you can. Speed density, utilizing a MAP sensor, is a pretty common self-tuning EFI platform. That said, for the setups we're talking about here, there is no cause to jump over to that school of thought/tuning.

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post #41 of 41 (permalink) Old 02-02-2017, 07:18 PM
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There's a reason why Ford ditched speed density, it isn't as precise as MAF fuel injection. Because there's a MAF sensor, the computer can adjust itself around wear and tear and modifications, to an extent. CCV is the way to go...and stay.

FWIW, JLT makes awesome PCV air/oil separators. My high mileage 11.2:1 setup was filling a 1 oz catch can every fuel tank.

Strangely, or not, my 250,000+ mile 5.0 mustang doesn't fill it nearly as fast.

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