New LS swap/install questions

[First c10]

So this is a stock truck air cleaner box with the MAF mount. The pipe diameter can't be over 3". If that is the case the 4" spectra won't work since the MAF is to high in the tube. Correct?

[Houston Ben]

Hi First,
Here is how I have my setup for now. Not pretty but I still need to get my A/C hooked up to clean up a little. This is the original intake minus the air box that I modified.

[First c10]

What year is the motor and is that the original intake tube for that motor?

[Houston Ben]

The motor is a 2011 5.3 from a 1500 and yes, that is the original intake tube for motor. I cut a hole just big enough where the grommet around the MAF had to be forced in a little to keep it sealed. However, I think I am running rich as my exhaust still smells like I am running my old Holley 750 dbl pump. Also, I will most likely upgrade to a Airaid u-build-it kit for the tubing.

[First c10]

So your MAF is not in the factory location correct? Do you have a picture of the MAF sticking down into your tube? I think that is my problem. The MAF is not down in the tube enough.

[Houston Ben]

I will see what I can do after work today.

[Hart_Rod]

Originally Posted by First c10

ok so yesterday I took the truck for a longer drive put on about 25 miles. tried it with the MAF connected and disconnected. When the MAF was connected the trans shifted funny (up shifted and down shifted) on normal acceleration and the motor didnt run very well.(stumbled coughed etc). so I disconnected the MAF and the motor idled great about 630 rpm and the trans shifted like a new car, nice and smooth....
this MAF or leak or problem whatever you call it is making me mad..... should I just remove the intake and check for leaks?

Sounds like your MAF needs to be recalibrated within the Tune (or you have a serious air leak downstream of where the MAF is reading the air flow). When you disconnect the MAF (simulated MAF fail), your tune will default to Speed density calibration and use the MAP part of the tune to run the engine.

REAL WORLD SCENARIO: I was almost done tuning my engine/tranny when I decided to build a custom CAI. After I finished it and installed it on the engine, it wouldn't run worth crap and the transmission acted like it had 500,000 miles on it! The fuel trims were all screwed up, the idle was terrible, and the transmission would shift and lock up erractically.... So, I put the original air intake on it that I had used for all of the tuning and it purred like a kitten......BLUF, nearly every calculation in the tune (engine and transmission), is based on the MAF sensor being calibrated correctly....

[First c10]

Rob,
I have been all over the engine looking for a vacuum leak plugged all the intake ports and still the same thing. sprayed carb cleaner and starting fluid all over the intake with no change to the readings. But when I move the CAI tube around the computer goes crazy. I am thinking I need to lower the MAF in the tube. what do you think?
Scott

[Hart_Rod]

Originally Posted by First c10

Rob,
I have been all over the engine looking for a vacuum leak plugged all the intake ports and still the same thing. sprayed carb cleaner and starting fluid all over the intake with no change to the readings. But when I move the CAI tube around the computer goes crazy. I am thinking I need to lower the MAF in the tube. what do you think?
Scott

I don't think a vaccum leak is your problem. I think you need to get someone to calibrate the MAF within your tune. Here's some light reading, ...

http://forum.grrrr8.net/showthread.php?t=20813

[First c10]

Rob,
Should I just buy the stock intake tube assembly and see if that works? ebay has them for like 150$ which will probably be a waste of money or should I find someone local to calibrate like your link talked about?
Do you think lowering the MAF in the path of air in the CAI would help?

[First c10]

Originally Posted by Houston Ben

I will see what I can do after work today.

That would be great thanks.

[Hart_Rod]

Originally Posted by First c10

Rob,
Should I just buy the stock intake tube assembly and see if that works? ebay has them for like 150$ which will probably be a waste of money or should I find someone local to calibrate like your link talked about?
Do you think lowering the MAF in the path of air in the CAI would help?

One thing you need to realize is the tune and calibration in your computer were based on a specific vehicle, with a specific weight, with a specific tire combo, with a specific air intake, with a specific drag coefficient, with a specific......I think you get the picture....

Instead of spending more money on air intakes, I would pay the money to get it dyno tuned by a reputable shop that you trust with the CAI that you currently have on your truck. All the big car company's spend a lot of time and money testing the air flow through factory air intakes. If the MAF sensor is not calibrated correctly, then the ECM will be giving the wrong information to the injectors therefore causing them to inject too much or not enought fuel into the engine. When the computer goes into closed loop, the O2 sensors will try to correct the rich or lean condition. This is what's causing your STFTs and LTFTs to be real hi or low. On a factory car in good working order, the LTFT are usual +/-3%.

This will also throw off the calibration in the transmission by providing incorrect torque calculation and thereby affecting the shifts and performance of the transmissions (due to the torque management).

As I said before, if the MAF calibration is wrong, everything beyond that is not going to work as it's supposed to. If it costs you $500 to get it dyno'd, that will be the best insurance money you've spent on your project. Just my .02$

EDIT: I forgot to add, everytime the ECM/TCM is flashed, the transmission has to learn the line pressures all over again. So drive it for a day or so to let everything settle in.

[First c10]

Rob
I agree with you that the best thing to do is have it calibrated on a dyno. I just can't believe I am the only one with this problem. Either a lot of people doing swaps are keeping the stock intake or they are not saying they have this problem.
I figured it out that if the stock tube at the MAF is 3" 7.06 sq" and the new tube I have is 4" 12.56sq" that's a 77% 5.5sq" increase in tube area. So if the MAF is calibrated to the stock 3" than I am way off. Does that sound right?

[Hart_Rod]

Originally Posted by First c10

Rob
I agree with you that the best thing to do is have it calibrated on a dyno. I just can't believe I am the only one with this problem. Either a lot of people doing swaps are keeping the stock intake or they are not saying they have this problem.
I figured it out that if the stock tube at the MAF is 3" 7.06 sq" and the new tube I have is 4" 12.56sq" that's a 77% 5.5sq" increase in tube area. So if the MAF is calibrated to the stock 3" than I am way off. Does that sound right?

....Or maybe they are getting them dyno tuned......,

It's not quite that simple, as the shape of the tube plays a part in it also, but that shows you the difference in potential flow. Also, the air filter size, shape, and design affects what the MAF sensor reads.

[First c10]

Yes I agree maybe they are!!!! Yeah the calculation was just on size. And that's a bunch as the computer doesn't know it. Ok sooooo where to get a dyno tune???? Anyone??? In cali Central Valley area???

[Houston Ben]

Hi First, sorry, wasn't able to get the pic last night. I will try today.

[First c10]

No Worries when you get a chance. Thanks.

[Super73]

Scott,

I also PM'ed you the info below.

Thanks for reaching out. Here is what I think is happening (sorry for the lengthy explanation but I like people to understand the fix):

The PCM bases air calculations for proper air fuel off of the volumetric efficiency table in the tune. It then uses the MAF to fine tune the VE table by reading actual air flow as it passes through the MAF. If the MAF table is not in synch with the VE table, the PCM can't do calculations properly. The O2 sensors also have a role in adjusting short trimm fuel cells (averaging to long trimm cells) helping to keep the AFR at stoich (what ever that is set to in the tune).

Location/restriction of the MAF or motor changes like a cam swap can affect this synchronization between the MAF and VE table.

When the MAF is disconnected the PCM does all of its calculations strictly on the VE table and takes a reading from the O2's for STFC and LTFC's correcting for AFR in closed loop only (Closed loop = Idle/part throttle - Open loop = cold starts and wide open throttle). You will have an SES light but the vehicle will run with the MAF disconnected, the fault causing the SES can be removed from the tune. This is a fail safe built in by GM called speed density mode. Might not run great though with out proper tuning.

There are two timing tables in the tune, High octane and low octane. When in the SD fail safe mode, the PCM automatically puts you in the low octane timing table. This can be fixed that so it is in the high table again if left in SD mode.

There are a couple ways to fix this issue you have:

SD tune, this is the method I prefer. You remove the MAF completely, and temporarily disable the O2 sensors. From there you are able to completely tune the VE table with a wideband AFR gauge. Once you are done with that you can add the factory O2's back in and they will self adjust AFR during closed loop compensating for environmental changes, IE hot/cold day or climbing a mountain. WOT was also tuned during this process.

MAF tune, I don't like the MAF much as it is a restriction and in my opinion does no good with a well dialed VE table. But, in the event one wants to keep it, a tuner must do the steps above then plug the MAF back in and recalibrate the MAF.

Shaun

[First c10]

thank you for the response I will check my PM's