FNBADAZ06 Posted December 11, 2011 Share Posted December 11, 2011 Just interested in what causes the dips and peaks in the MAF graph...watching it as g/sec on my logs. Is the MAF signal usually an oscillating signal (a function of intake valve opening ? ), or is this oscillation a result of turbulent airflow across the sensor ? I understand that the MAF readings are a clear indicator of how much power the car can make ? Should you ever expect to see a smooth MAF signal in the log ? Link to comment Share on other sites More sharing options...
Two Fangs Posted December 11, 2011 Share Posted December 11, 2011 The MAF should be a smooth signal. The new Hitachi MAFs are so sensitive, that they usually are not. This condition is usually amplified through the use of aftermarket intakes. It can be improved by installing a honeycomb to smooth the air out. Link to comment Share on other sites More sharing options...
FNBADAZ06 Posted December 11, 2011 Author Share Posted December 11, 2011 The MAF should be a smooth signal. The new Hitachi MAFs are so sensitive, that they usually are not. This condition is usually amplified through the use of aftermarket intakes. It can be improved by installing a honeycomb to smooth the air out. Is it possible this is being caused by my open shroud...my custom ram-air setup ? I guess I could close it back up and see what the logs show. Do you think this turbulence is causing more of a problem than any benifits I'm seeing by the rapid drop of IAT's when the car is in motion ? Link to comment Share on other sites More sharing options...
Two Fangs Posted December 11, 2011 Share Posted December 11, 2011 Dude, I have found myself on the bad side of this on more occasions than I would like to admit. Where I stand on the subject is, air does not flow into the engine like the sawblade that the datalog shows, and I have seen hundreds with this problem since the LS7 and especially since the LS3 was introduced. My stance is that it is unnatural for the air to flow in that manner. I want you to imagine you have to fill a very small glass (think teeny-tiny, like an 1/8" across the top) just a tick from the top from a kitchen faucet that has the screens in the end of it removed. Now fill the same one just a tick from the top from a regular kitchen faucet. Now do this several times a second. It does not take long to figure out that the smooth flow is easier to measure than the flow that is not. The honeycomb in front of a regular MAF allows this to occur, and it was closely replicated with the air filter design and MAF placement in the stock LS7 and LS3 setup. When we move it, change filter design, and everything else, it really screws with this sensor. I ran into the same challenge with El Superbeasto. The airflow perturbations through the turbo up-pipe gave me fits until I bought a honeycomb from this dude and fixed it. http://www.saxonpc.com/100mm-cells-for-100.html Link to comment Share on other sites More sharing options...
FNBADAZ06 Posted December 12, 2011 Author Share Posted December 12, 2011 Dude, I have found myself on the bad side of this on more occasions than I would like to admit. Where I stand on the subject is, air does not flow into the engine like the sawblade that the datalog shows, and I have seen hundreds with this problem since the LS7 and especially since the LS3 was introduced. My stance is that it is unnatural for the air to flow in that manner. I want you to imagine you have to fill a very small glass (think teeny-tiny, like an 1/8" across the top) just a tick from the top from a kitchen faucet that has the screens in the end of it removed. Now fill the same one just a tick from the top from a regular kitchen faucet. Now do this several times a second. It does not take long to figure out that the smooth flow is easier to measure than the flow that is not. The honeycomb in front of a regular MAF allows this to occur, and it was closely replicated with the air filter design and MAF placement in the stock LS7 and LS3 setup. When we move it, change filter design, and everything else, it really screws with this sensor. I ran into the same challenge with El Superbeasto. The airflow perturbations through the turbo up-pipe gave me fits until I bought a honeycomb from this dude and fixed it. http://www.saxonpc.com/100mm-cells-for-100.html Awesome info, bud Link to comment Share on other sites More sharing options...
Jon Posted December 12, 2011 Share Posted December 12, 2011 What size honeycomb would I need for my LS3 with Callaway Honker? It seems to me that in an NA application that would be a bit of a flow restriction though. I would dyno it before and after if I put one on. Link to comment Share on other sites More sharing options...
Two Fangs Posted December 12, 2011 Share Posted December 12, 2011 The trade-off for the slight pressure drop it creates versus the benefit of stable output is a no-brainer from where I stand. I think the 6:1 with 1/8" cells is the way to go. As always, your mileage may vary... Link to comment Share on other sites More sharing options...
Cross Posted December 12, 2011 Share Posted December 12, 2011 HHHMMMM very interesting... and sad I removed my honeycomb. I have an SLP Maf though and I think it still has it, looks the same as the Vette one. Link to comment Share on other sites More sharing options...
Jon Posted December 12, 2011 Share Posted December 12, 2011 What does 6:1 mean? Link to comment Share on other sites More sharing options...
HOXXOH Posted December 12, 2011 Share Posted December 12, 2011 What does 6:1 mean? It's the ratio of cell hex size to cell length. A 1/8" hex cell with a 3/4" length is 6 to 1. Likewise a 5 to 1 has a length of 5/8". Link to comment Share on other sites More sharing options...
Jon Posted December 12, 2011 Share Posted December 12, 2011 Thanks. Now what would determine which one you should use? Wouldn't the 5:1 have a smaller differential pressure? Link to comment Share on other sites More sharing options...
HOXXOH Posted December 13, 2011 Share Posted December 13, 2011 Thanks. Now what would determine which one you should use? Wouldn't the 5:1 have a smaller differential pressure? I'd first want to know the % of free area and to calculate friction losses. There's a world of difference between .004 wall and .030 wall 1/8" hex, but very little between 5/8" and 3/4" length. Maybe 4 to 1 in 1/4" hex mounted a little farther upstream would be enough to reduce turbulence with less restriction. Link to comment Share on other sites More sharing options...
NicD Posted December 13, 2011 Share Posted December 13, 2011 No MAF signal is going to be perfectly smooth even with airflow straighteners, etc. Now in a perfect world I would much rather have a nice steady signal but unfortunately it's not. I would go as far as saying that as long as the signal isn't tripping burst knock and isn't bad enough at part throttle/idle that it's causing driveability issues it's workable. Of course this varies significantly with the MAF size and resolution of the sensor as to what you can get away with and generally the later model stuff is more affected since it's resolution is much smaller and each data point is quite a bit more significant than the earlier generation. Link to comment Share on other sites More sharing options...
Jon Posted December 14, 2011 Share Posted December 14, 2011 With the new Callaway Honker cold air intake I get a bit of bucking if I'm at light throttle and let off the gas to slow down a little. Link to comment Share on other sites More sharing options...
Two Fangs Posted December 17, 2011 Share Posted December 17, 2011 I believe it is worth it to try the honeycomb. While the car is primarily working in SD at those RPM ranges, if the disparity between the two airflow signals vary too greatly, it can give you issues up to and including a CEL and no traction control. Nic brings up a good point, we do not live in a perfect world, but these freaking Hitachi MAFs are pain in the ass. Link to comment Share on other sites More sharing options...
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