Trying to resolve some conflict between two different sources of info that should both be reliable. New crate LS3 with 08 Corvette ecu and harness by PSI conversions. Both recommend a 12" straight section of inlet pipe before the intake elbow/throttle body. GMPP in instructions for their cold air intake kit suggests placing the MAF sensor at least 2" beyond the filter (they use a cone filter on the end of a straight section of 4" pipe) and 10" of straight pipe downstream of the MAF sensor before the throttle body. PSI suggests putting the MAF sensor in the middle of the 12" section of straight pipe - 6" of straight pipe on either side of the sensor.

Anyone have any experience with this? It's likely I'll have a 45 degree mandrel bent elbow just after the filter -- picture below mocked up with paper...

 

I have always heard that you need at least 12" of straight pipe before the TB. I have seen air cleaners right up on the TB, but I am pretty sure they tune out the MAF with a Speed Density tune for that.

 

Thx - clarifying - my question isn't how long of a straight section is needed. It's WHERE in the straight section should the maf sensor be mounted.

 

Put it in the middle and see how it runs?

Here's where I put mine an it runs fine with no codes so far....haven't driven it yet however.

 

12" of straight, anywhere before the TB. Put it anywhere beyond that, but no closer than that unless your motor has a Speed Density tune. Only reason for the straight pipe requirement is so that the MAF can read more accurate air not bouncing around corners.

 

Thx for the responses guys - and now we have 3 answers, no closer than - 12" from TB, 6" from TB and 10" from throttle body.

Since the guys at PSI do this for a living I suppose I'll follow their guidance and put it in the middle of the 12" pipe. Jozw30 - trying to avoid cutting/fabbing the aluminum tubing more than once.

 

I think a lot of it has to do with the newer 5 wire MAF having the IAT built into it. On my 02 LS1 my MAF is right after the 90 on the throttle body, but my IAT is further down the line. Been this way since 2012 with zero issues.

 

PSI did my harness and had some concerns about my intake system. Not much room in a '39 Chevy so I did what I had to. It doesn't throw codes and, as far as I can see, doesn't affect the engine operation. Note I did not say performance because I have nothing to compare it to.

 

double post

 

So where did you put yours? PSI happy with my mock up - but it conflicts with Chevy's aftermarket guidance. I think I see yours in the upper tube bout halfway between filter and elbow?

 

Thanks for help guys - caused me to go back and re-read Chevy's instructions on their universal kit. My bad - I mis-read them the first time. All they suggest is that the maf sensor (5 wire 'blade' type) go 2"-3" beyond a filter or elbow and at least 1" before the throttle body or elbow into the throttle body. Should be fine where I've mocked it up. Now to find the right elbow.....

 

It has to do with turbulent air causing irratic readings. The best thing you can do is put in a large cell MAF screen from SaxonPC to improve the laminar airflow across the sensor. Older factory MAFs have these screens, dating all the way back to the mid-80s.

 

Thx Mike - well aware of what the issue is; just to achieve some others' experience of how they solved the issue. The screens of the past were necessary because the older style mass air sensors were much more jenky with regard to flow across the hot wire than the more contemporary ones are. Consensus seems to be -- get the newer 5-wire blade style into the middle of a 10"-12" straight section of 4" pipe and the sensor will be happy. That's where we're headed. BTW - those SaxonPC straighteners look like nice pieces!

 

I still used one despite having a clean shot at the sensor in our Procharged TBSS - you can actually see the difference in how much cleaner the MAF signal is with the screen installed while datalogging.

 

A quality air filter will help reduce turbulence in the area right after the filter, allowing you to place the maf closer and closer to the filter. Alot of performance 4-cylinder engines with OEM turbochargers use a maf directly bolted to the air filter (it literally has a flange to bolt the filter housing on the maf). The only time turbulence will be introduced at the filter area is if there is a leak, or no filter, or you are using a poor filter design. You can test this by powered up the maf, using a vacuum cleaner on the pipe, install the filter and maf to the pipe will pulling suction through it, and log the voltage of the maf output, it should be consistent (no jumping voltage) output with varying degree of suction (make a leak to reduce suction and gradually "fix" the leak to increase suction)

#2. turbulence AFTER a maf due to a rapidly closing throttle body or surging compressor wheel is what really screws with the maf voltage. You want as much pipe as you can get between the compressor/throttle body and maf sensor as possible, and as much straight as you can right before it hits the maf. A maf sensor requires a very consistent gradual flow. Anytime the voltage spikes or dips the engine will stumble.

#3 Do a "boost leak" test (even if you are non turbo) to the pipe. A maf sensor to properly work depends a leak free plumbing. A leak in the intake manifold or pre-engine tube will mess with a maf in a big way.

 

Yep, if you give it at least 6" straight before and 6" after it works well. Try and keep 90* or less bends out of your system, use sweeping bends, not tight turns, it makes a difference.

 

In case anyone else pulls this one up as a reference - pic below of where I ended up - right in the middle of the 12" section of 4" pipe, very close to the DBW throttle body motor. And it's running flawlessly -- no check engine light, no codes. Thanks for the help guys!