Pro Stock John

iTrader: (34)

Question:

How do you adjust the MAF T either BASE or WOT if you have......a breather on driver's side valve cover, no pcv on that side. That's like having a vacuum leak in some respects. So my l-trims are always going to be high to compensate are they not? So I should not mess with the BASE right? Are the other 400-436ci folks running a complete stock pcv system?

02 'Hawk

I don't know why you wouldnt. breathers are old school anyway. just pick up the new PCV, part number is posted here somewhere. guy said it works and it's what, 2 bones?

I'm going to get it just for the helluva it. hell john, check it out too. I wouldnt do a breather anyway. didn't on my LT1

Pro Stock John

iTrader: (34)

I'm not sure the stock pcv system for a 99 car (I have 99-01 heads) is adequate enuff for my 422ci motor.

But having a breather on the car is tantamount to having a slight vacuum leak so the car is going to appear lean on Autotap for sure (and it does). But that is not the case with my setup. I have 40 lb injectors, big intank pump, calibrated SLP MAF with the screen intact so I have a lot of fuel.

onfire

iTrader: (17)

Even if it is a small vac leak (the jury is out in my mind on that one) you would tune the same. The o2's at idle and part throttle will ramp up the ltrims to to get the A/F ratio back to desired...so the same theory applies....get the ltrims under 5 at part throttle and get the wot A/F ratio on a wideband around a 12.6 on a Dynojet or 13.0 if you're using a wideband at the track. <img src="graemlins/gr_xmas.gif" border="0" alt="[santa]" />

Pro Stock John

iTrader: (34)

I'm seeing 15% or more at cruise/part throttle I am running a small K&N breather in the back of the driver's side valve cover, I capped off the back of the passenger side valve cover, and just the front pcv line part on the passenger side going into the TB.j I also have an LS6 pcv system on the car but it seems like it would not keep up.

I am shooting for my like 13:1 or even a bit more lean since I am NA.

onfire

iTrader: (17)

If I had that nice 422 in my car I would find someone close by to get an ls1edit dynotune and tune the ltrims to near 0 and set the wot around 12.7 on a dynojet (which in reality is around 13.1 on the track)...and I would make sure the wot curve is smooooth. My second option would be to set the maft on 0 wot and on +10 part throttle and drive it for 20 miles...autotap and check the ltrims if they were under 5 call it good and do a wot check. Tune the wot o2's until 890ish (even though I HATE tuning with regular o2's...the rick/lean curve is steep and can be misleading). After obtaing 890's (and if I didn't hear any audible pinging) I would do a wot run at the track (without oct booster...it colors plugs) and shut the engine at the end of the run and pull a couple of plugs to get a reading.......Although with a nice 422 I would make a hard attempt at the first option. <img src="gr_grin.gif" border="0">

jimmyz80

iTrader: (1)

John,
I had the same dilemma myself awhile ago. I could set up a-tap, and watch my LTrims go down when I pulled off the breather and covered up the hole. It definitely lets some air pass though into the manifold but I'm guessing not enough to affect anythingat part throttle and above when your manifold vacuum decreases.

I ended up just taking the breather off for the sake of seeing more friendly numbers on the screen.

Today I just installed the new PCV someone had mentioned in this thread, so I can reduce my oil consumption. It is just a PCV valve with no "valve" in it. Just a very small oriface. I don't think the oriface is large enough to pass the amound of crankcase gasses a large cube or power adder motor would generate so I would say it's not a solution for you.

You could possibly have a little valve fabricated for the breather to only allow gasses to leave the crankcase through the breather. This would keep it from ingesting all the excess air that will throw your #'s all out of whack at idle.

Myabe something as simple as removing the top of the breather and attaching a piece of rubber over the hole as a little "flapper" valve and then re-attaching the top.

Colonel

I just use the stock setup. Ltrims are usually 10 or less which is fine with me. I set the base once a long time ago and have left it alone ever since, tuning the WOT only. <img src="gr_stretch.gif" border="0">

Pro Stock John

iTrader: (34)

Jimmy, that is exactly what I am talking about.

15% L-trims don't really concern me, crankcase pressure concerns me more. <img src="gr_stretch.gif" border="0">

jimmyz80

iTrader: (1)

See, not all my ideas are whack <img src="gr_tounge.gif" border="0">