Intake, Header, HFC, CBE = Too Lean?

Modshack · 03-24-2010, 09:57 AM

Quote:

Originally Posted by Red370

Self admittedly, I know jack squat about A/F ratios, but i'm curious... my AP says that i'm running an avg. of 14.2-14.4 at idle, is that a normal idle ratio? is it only considered running lean at a specific RPM?

There are 2 fuel control systems. The first, when at idle or partial throttle, is controlled by the MAF and 02 sensors who are constantly sending readings back to the ECU to maintain ideal Stociometric ratios (14.7:1). This is called closed loop. An A/F gauge will bounce around a lot as the mix is read and constant corrections are sent to the ECU. When you go wide open throttle (open loop), the fueling defaults to some pre-built fuel maps in the ECU. These are usually slightly modified by the Long term fuel trims (correction factors) that are determined over time by the adjustments the 02 sensor Has been making. Typically the Z corrects from a slightly rich tune.
As Parts are added (Exhaust, Intake, HFC's), the rich correction is reduced as the Fuel trims approach Zero. Add Zero to the pre-built map and you'll have a bit more power due to the leaner mix.. (richer is slower). To truly see how closely you are to optimum, read the A/F ratio at WOT as is the case with all dyno plots.

In this picture, Additive is the short term fuel trims, Multiplicative is the long term trims:

Red370 · 03-24-2010, 10:02 AM

Quote:

Originally Posted by Modshack

There are 2 fuel control systems. The first, when at idle or partial throttle, is controlled by the MAF and 02 sensors who are constantly sending readings back to the ECU to maintain ideal Stociometric ratios (14.7:1). This is called closed loop. An A/F gauge will bounce around a lot as the mix is read and constant corrections are sent to the ECU. When you go wide open throttle (open loop), the fueling defaults to some pre-built fuel maps in the ECU. These are usually slightly modified by the Long term fuel trims (correction factors) that are determined over time by the adjustments the 02 sensor Has been making. Typically the Z corrects from a slightly rich tune.
As Parts are added (Exhaust, Intake, HFC's), the rich correction is reduced as the Fuel trims approach Zero. Add Zero to the pre-built map and you'll have a bit more power due to the leaner mix.. (richer is slower). To truly see how closely you are to optimum, read the A/F ratio at WOT as is the case with all dyno plots.

In this picture, Additive is the short term fuel trims, Multiplicative is the long term trims:

Tis why I love this forum, lots more people smarter than I, learn somethin new every day, thanks, +1 rep to you sir.

Zsteve · 03-24-2010, 09:26 PM

Quote:

Originally Posted by Red370

Self admittedly, I know jack squat about A/F ratios, but i'm curious... my AP says that i'm running an avg. of 14.2-14.4 at idle, is that a normal idle ratio? is it only considered running lean at a specific RPM?

And you read me at the same point too and I dont have a tune and only had the CBE and K&Ns drop ins.

mrdino77 · 03-25-2010, 09:38 AM

Wow I just learned a lot by reading up on this thread. I have a question then, since I will be running FI CBE w/test pipes and might do a K&N Drop in would I need a retune for that as well? I plan on most likely getting a tune anyway but I was just curious if this would also present a case to retune seeing im not actually switching the CAI.

semtex · 03-25-2010, 09:48 AM

Quote:

Originally Posted by mrdino77

Wow I just learned a lot by reading up on this thread. I have a question then, since I will be running FI CBE w/test pipes and might do a K&N Drop in would I need a retune for that as well? I plan on most likely getting a tune anyway but I was just curious if this would also present a case to retune seeing im not actually switching the CAI.

Just dyno your car after you get all your mods in. As part of the dynoing process, they measure your AFR. (Not all places do it automatically, so you might have to ask for it.) If your AFR is in the acceptable range, then you're good to go. If it's out of whack, then you know you need a tune. There's no sense in guessing on whether or not you'll need a tune when you can actually go get your AFR measured and find out for sure. It's like trying to figure out if you need blood pressure medication without getting your BP reading checked first.

F.I. Inc. · 03-25-2010, 09:58 AM

Quote:

Originally Posted by semtex

Just dyno your car after you get all your mods in. As part of the dynoing process, they measure your AFR. (Not all places do it automatically, so you might have to ask for it.) If your AFR is in the acceptable range, then you're good to go. If it's out of whack, then you know you need a tune. There's no sense in guessing on whether or not you'll need a tune when you can actually go get your AFR measured and find out for sure. It's like trying to figure out if you need blood pressure medication without getting your BP reading checked first.

Good analogy about the blood pressure medication!

Tony

Zsteve · 03-25-2010, 10:43 AM

Quote:

Originally Posted by mrdino77

Wow I just learned a lot by reading up on this thread. I have a question then, since I will be running FI CBE w/test pipes and might do a K&N Drop in would I need a retune for that as well? I plan on most likely getting a tune anyway but I was just curious if this would also present a case to retune seeing im not actually switching the CAI.

Im not sure if this means I am running lean but again when I did the K&N drop ins and the CBE my tail pipes went from having black junk on them(before the mods), to not having any black junk on them after the mods. But something changed. Im getting my Cobb today so I will do a AF reading before and after to see the changes and where Im at when at higher rpms then idle before I put the new map in. I think I went leaner than I was but thats not to say that Im too lean to hurt anything, Im sure the tune will get me some extra gains.

m4a1mustang · 03-24-2010, 10:13 AM

Tony, thoughts on the injen intakes? From what I remember thee MAF tubes are virtually identical in diameter (injen vs stock).

Modshack · 03-24-2010, 10:29 AM

Quote:

Originally Posted by m4a1mustang

Tony, thoughts on the injen intakes? From what I remember thee MAF tubes are virtually identical in diameter (injen vs stock).

It's not the diameter of the intake tubing, but actually the diameter of the tube where the MAF reads the airflow. You'll notice some designs run a larger pipe, but neck them down at the MAF. As Tony said, this needs to be tuned to the car. I do a lot of work in this area and recently have been experimenting on the Z. As you open up the tube at the MAF, the air flow actually slows down and the fuel system signal is reduced (this is basic physics). This is why some intakes make more power. Since filter restriction is not really a big factor, it is this subtle fuel adjustment that is making the difference. The Z is naturally a bit rich...Lean it a bit to bring it to optimum A/F ratios and you make more power.

The stock MAF tubes are tapered a bit from a 2.34 to 2.36 Internal diameter. I've recently revised my Custom CAI and cut some new tubes at 2.39 with a Venturi taper at the leading edge. These have resulted in a Zero Fuel trim correction over 150 miles now, which indicates they are pretty much on the money. The car runs very strongly. For more info on this you can read my page here: Modshack | Stage 2 MOFO (BAMM)

F.I. Inc. · 03-24-2010, 10:38 AM

Quote:

Originally Posted by Modshack

It's not the diameter of the intake tubing, but actually the diameter of the tube where the MAF reads the airflow. You'll notice some designs run a larger pipe, but neck them down at the MAF. As Tony said, this needs to be tuned to the car. I do a lot of work in this area and recently have been experimenting on the Z. As you open up the tube at the MAF, the air flow actually slows down and the fuel system signal is reduced (this is basic physics). This is why some intakes make more power. Since filter restriction is not really a big factor, it is this subtle fuel adjustment that is making the difference. The Z is naturally a bit rich...Lean it a bit to bring it to optimum A/F ratios and you make more power.

The stock MAF tubes are tapered a bit from a 2.34 to 2.36 Internal diameter. I've recently revised my Custom CAI and cut some new tubes at 2.39 with a Venturi taper at the leading edge. These have resulted in a Zero Fuel trim correction over 150 miles now, which indicates they are pretty much on the money. The car runs very strongly. For more info on this you can read my page here: Modshack | Stage 2 MOFO (BAMM)

Very impressive, you should market this if it works in the long run. Got to run, have alot of exhaust and headers to build...

Thanks, Tony

F.I. Inc. · 03-24-2010, 10:35 AM

Quote:

Originally Posted by m4a1mustang

Tony, thoughts on the injen intakes? From what I remember thee MAF tubes are virtually identical in diameter (injen vs stock).

As far as fitment, quality and overall looks I think hands down they are the nicest. I am throughly impressed with them!

As far as performance I have not dynoed a set yet. I hear mixed reviews from customers and until I dyno them I just don't know. What I can tell you is the filter location is closed off from the world and cold air will have a really hard time getting up in there. Now if you modified the bottom of the fender well liner by drilling holes in it to create perforation you will obviously allow more air to get to them. This is the goal, right! Cold Air!!! Now, it is very simple theory if you can keep the bends to a minimum, allow the filters to get cold air and mimic the stock tube size to keep the maf calibrated then you should pick up performance across the board. I think Ingen has achieved two out of three. If you look at their tube it looks like it was designed off of stock with a smaller diameter where the MAF is located. They also claim that it is dyno tuned and calibrated in the R&D process. The bends are also long sweeping bends that are as minimal as you can make them given the room they have to work with. Remember less dramatic bends, less restriction. The only one of the three that they do not have is the cold air factor. Like I stated before, the filters are hidden from the world. I know about the hydrolocking issue from water getting in them and this is part of the reason why they are where they are but has it really ever happened to anyone with this car???

LiquidZ · 03-24-2010, 10:15 AM

Still waiting on those results Tony

Vegitto-kun · 03-24-2010, 10:20 AM

Ha...ha...ha

I already got the stillen gen 3 CAI's installed

CrownR426 · 03-24-2010, 10:36 AM

A tune seems like a great solution to the problem.

Vegitto-kun · 03-24-2010, 10:39 AM

problem now is where the hell will I find a place that is actually good at tuning/solving these problems -_-

03-24-2010, 10:13 AM	#8 (permalink)
m4a1mustang A True Z Fanatic Join Date: Feb 2009 Location: Northern VA Posts: 55,385 Drives: on two wheels Rep Power: 6964	Tony, thoughts on the injen intakes? From what I remember thee MAF tubes are virtually identical in diameter (injen vs stock). __________________ - Steve Zs & Coffee - Saturdays at 10AM in Fairfax, VA and Columbia, MD (Click the banner!) LIKE us on Facebook!

03-24-2010, 10:15 AM	#12 (permalink)
LiquidZ A True Z Fanatic Join Date: Nov 2008 Location: Columbus, OH Posts: 1,940 Drives: Mag. Black 2009 370Z Rep Power: 706	Still waiting on those results Tony __________________

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03-25-2010, 09:38 AM	#4 (permalink)
mrdino77 Base Member Join Date: Jan 2010 Location: Tampa FL Posts: 52 Drives: 2009 370z Rep Power: 17	Wow I just learned a lot by reading up on this thread. I have a question then, since I will be running FI CBE w/test pipes and might do a K&N Drop in would I need a retune for that as well? I plan on most likely getting a tune anyway but I was just curious if this would also present a case to retune seeing im not actually switching the CAI.

03-24-2010, 10:20 AM	#13 (permalink)
Vegitto-kun A True Z Fanatic Join Date: Feb 2010 Location: USA Posts: 2,011 Drives: 09 370Z Rep Power: 264	Ha...ha...ha I already got the stillen gen 3 CAI's installed

03-24-2010, 10:36 AM	#14 (permalink)
CrownR426 A True Z Fanatic Join Date: Nov 2008 Location: South Korea Posts: 4,676 Drives: Manual Rep Power: 849	A tune seems like a great solution to the problem.

03-24-2010, 10:39 AM	#15 (permalink)
Vegitto-kun A True Z Fanatic Join Date: Feb 2010 Location: USA Posts: 2,011 Drives: 09 370Z Rep Power: 264	problem now is where the hell will I find a place that is actually good at tuning/solving these problems -_-