LS2FD3S

I had a fabricator make my intake tube to use a card style MAF, and weld in a 6an nipple for my catch can return from the passenger valve cover. He was supposed to put it downstream of the MAF but he put it directly across from it.....so before I take the car to my tuner is this going to cause turbulence at the MAF? With the catch can I'm hoping I won't be oiling the sensor.

drew408

Like I said in the other thread,why even run it back to the intake?? That's for emissions....

If u have a catch can,run from your VC's to the catch can and stop. If u want vacuum on it,put a header evac on it...

LS2FD3S

Because I already have a built can, expensive AN lines, expensive AN fitting intake tube, and everything is already mounted in my freshly painted bay. The line ran from the cover to the intake from the factory so I'd rather leave it that way, I don't know what your talking about with the header I've never seen or heard of that before.

LS2FD3S

I could always tap a AN fitting into the silicone coupler downstream and it'll work like factory plus a can in-line. But my OCD will kill me capping the aluminum AN fitting in my intake tube.
Looking for advice from a tuner and what their insight would be.

Old Geezer

iTrader: (3)

didn't like the responses he got the first time.....

drew408

Lol

I run the same thing and have lots of AN lines on mine...as a matter of fact,I run an lines for vacuum lines on both my Buicks and my 408.


This is what I'm talking about and it even comes for AN fittings http://m.summitracing.com/parts/vpe-...FdUUHwodqdACXA

Google crankcase evac....

A smart tuner will tell you exactly what I am right now.

You fucked up by getting a fitting welded onto your intake pipe man.

LS2FD3S

Well I'd say the fabricator fucked up putting were it wasn't supposed to go across from the MAF, if a tuner thinks it will disrupt flow there then it seems like the logical choice would be to just move it downstream of the MAF into the coupler. That scavenger had horrible reviews and I don't have access to welding in my garage and the car doesn't run yet. So it has nothing to do with weather or not I liked the answer I got, this is the Internet, I'd like more than just one persons point of view, a tuner to be specific, because if it will effect it than I'll move it, if not, I'll leave it. I'm glad you have AN fittings on your car. Again not the point, the point is I don't want to spend more $$ removing the dual can, repainting the firewall where it was mounted, spending more $ on the header evac option and drilling into a new custom made set of headers, the car is a conversion.

LS2FD3S

I don't want a atmosphere vented can

LS2FD3S

Here's what I have, the red cap has the 6an under it, right across from the MAF

LS2FD3S

Ok this is what I came up with. It's post MAF just like OEM, should work fine. We'll see after I get it started up this weekend.

93Z2871805

iTrader: (5)

I'd second this. However OP, since the airstream will always be sucking towards the throttle body, I'd say the placement you have won't cause issues.

This only works with open headers. A full exhaust would allow for back-pressure.

edge04

iTrader: (9)

my set up has them across from one another. I too wondered if it would cause an issue but was told by many, including the maker of my can might mouse, that it would not. To date hasn't. And like mentioned above, the air stream will always be sucking toward the TB.

LS2FD3S

Good to know everyone thanks for the input!

COSPEED2

iTrader: (7)

I would make sure it is a can return, and not your cleanside of the system. Cleanside (on non turbo or centri SC) should always be connected just downstream of the MAF so all air entering is metered by the MAF. If you are running a dual outlet can, then the secondary outlet would attach right where the picture shows to a barb installed just in front of the throttle body as this provides suction for evacuation when your under acceleration when intake manifold vacuum drops to zero due to reversion pulses providing constant evacuation no matter what mode of operation the engine is in.

Can you describe what you have and how it all runs? You never want any of a proper system connected upstream of the MAF as the ECU/PCM is looking at air flow in measured by the MAF, Pressure or vacuum present in IM from the MAP, and the upstream O2's. All of this data is how the ECU decides cylinder fill rate, short term fuel trims, etc. If you introduce non metered air, then your short term fuel trims go nuts adding and subtracting fuel in an attempt to have all sensors fall within the tunes parameters. If turbo or centri blower, then this is done a bit different due to the iM always being under boost pressure when turbo's are spooling.

edge04

iTrader: (9)

Interesting. I am using a draft can that has a filter on top that breathes into the atmosphere. I have it hooked up exactly like I had it when I was running a procharger. The line that went pre blower is now in my inatke basically across from my card style map and pre TB and the 2nd line is connect to my passenger side valvle cover via the oil fill cap, all are -8 fittings.

When I had the PC i was MAF less however I am now running a MAF and been trying to dial in the tune. Wondering now if I am fighting an up hill battle???

COSPEED2

iTrader: (7)

If you are not FI that pressurizes the IM with boost, then yes, you do want the cleanside air metered by the MAF. You were speed density tuned then so the MAP dictated most of what the fuel trims did. If you can plumb the cleanside into the main intake air tube post MAF, then your tune will be far easier as the PCM is hunting and constantly adding and removing fuel via short term fuel trims. It see's data from the MAP and upstream o2's, but the MAF is sending inaccurate data so to try and compensate the short term trims go nuts.

Let me know if you need more guidance in how to properly route a system for yours.

edge04

iTrader: (9)

well it is slightly post the MAF in the stock hole from K&N. I asked the manufacture of the catch can and was told it should be fine but I always wondered about it.

COSPEED2

iTrader: (7)

As the MAF on the K&N is right at the TB, several issues arise. #1 is when the TB blade closes, this disruption in flow will cause the MAF to not give accurate readings to the PCM. MAF should always be a minimum of 6" from the TB but fitment issues that is not always easy to do. Your cleanside barb is directly across from the MAF so it is NOT getting 100% measured/metered air and this will throw off your tune as far as short term fuel trims. If you could somehow get the MAF moved further from the TB so the barb is definitely providing air that has already passed the MAF you will find it much better.

LS2FD3S

To answer a previous question I have the Iines routed exactly as OEM for the LS2, just the addition of cans, my new tap post MAF is about 5" down now so I think it will be perfect. The KN setup above was pretty much close to what I had but mine was worse and directly accross.

edge04

iTrader: (9)

Thanks for the info, makes sense however I just got done tuning it and its dialed in. I'm running both MAF and VE using HPT COS. Still a little rich during idle but I'll tune that out.