Air Load

[Leonidas514]

What's up everybody. It's been a while, just been doing tons of work and mods to the car. Finally got it all back together and decided to switch tuners from PBD to Lund.

I'm doing my initial logs with Lund and was wondering if anyone knows if Lund and PBD dyno use the same air load data? My car only shows 1.78 @6500 with the Lund tune but on the PBD tune at the same 6500 showed 2.20. I'm thinking I've got a boost leak. Or, I also moved the MAF from the IC to the intake tube, would this cause a lower reading? I'm sure Lund will reply in the morning but was just curious.

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[engineermike]

Air load is defined as the mass air flow divided by engine speed divided by engine displacement air mass at standard temp and pressure. If the maf is calibrated right, there are no leaks, and the displacement is correct, then it should read the same.

How much boost?

 

[markmurfie]

Half the engines displacement air mass at standard temp and pressure. Only half the engines cylinders do an intake stroke per revolution on a four stroke engine.

If all else is equal, during a steady state throttle condition, just moving the MAF location the lb/min should be the same, so the load should be the same.
Different MAF locations will have different frequency transfers, but thats your tuners job to understand, not yours.

Don't get too caught up in it. Focus on your goals for the car and if you are making progress toward them. You paid these tuners to think for you.

 

[Leonidas514]

Air load is defined as the mass air flow divided by engine speed divided by engine displacement air mass at standard temp and pressure. If the maf is calibrated right, there are no leaks, and the displacement is correct, then it should read the same.

How much boost?

Should be around 18lbs

 

[Leonidas514]

Thanks guys

 

[SolarFlare]

I would expect higher BUT he can change it from 1 tune to another and car should show higher and not be any faster.

 

[Leonidas514]

I would expect higher BUT he can change it from 1 tune to another and car should show higher and not be any faster.

Thats what Lund told me this morning. Thanks

 

[engineermike]

18 lb should be way more than 1.78 though. 1.78 is more like 14 lb.

 

[Jackson1320]

Half the engines displacement air mass at standard temp and pressure. Only half the engines cylinders do an intake stroke per revolution on a four stroke engine.

If all else is equal, during a steady state throttle condition, just moving the MAF location the lb/min should be the same, so the load should be the same.
Different MAF locations will have different frequency transfers, but thats your tuners job to understand, not yours.

Don't get too caught up in it. Focus on your goals for the car and if you are making progress toward them. You paid these tuners to think for you.

Air load is defined as the mass air flow divided by engine speed divided by engine displacement air mass at standard temp and pressure. If the maf is calibrated right, there are no leaks, and the displacement is correct, then it should read the same.

How much boost?

When he moved the m.a.f sensor from the intercooler to the intake charge pipe it changed the diameter of the m.a.f housing. Is that going to cause a change in load?

 

[engineermike]

When he moved the m.a.f sensor from the intercooler to the intake charge pipe it changed the diameter of the m.a.f housing. Is that going to cause a change in load?

It won’t change the actual air load, but if it changes the maf calibration and the calibration data in the pcm isn’t corrected then it will affect the measured and logged load which will no longer be accurate.

 

[TRP45ACP]

18 lb should be way more than 1.78 though. 1.78 is more like 14 lb.

What would you estimate a load of 2.0 at?

 

[engineermike]

What would you estimate a load of 2.0 at?

I’d guess 18 or so.

 

[markmurfie]

Because PV=nRT, what load equals what boost is very air charge temperature dependent. I can agree with 18 for a popular positive displacement blower with the current water intercooler setups they come with. Less during the winter months. A turbo or centrifugal with an inadequate intercooler setup it might take a bit more boost, as air density will just be lost to out of control temperatures if you are beyond the intercoolers limits. There's also volumetric efficiency that you need to factor in. Smaller turbos and blowers do become a limit to over all airflow required to maintain charge density. Then of course there is physical limit to how fast they can spin. This table assumes the boost level is produced from a constant volumetric efficiency with the needed airflow being meet by both the engine and FI application. Reality may vary greatly because of these factors. Its just a overly simple way from load to approximate boost based on temperature.

 

[engineermike]

Barometric pressure affects it significantly as well…

 

[Jackson1320]

It won’t change the actual air load, but if it changes the maf calibration and the calibration data in the pcm isn’t corrected then it will affect the measured and logged load which will no longer be accurate.

What is your opinion on the MAF location? Is in the intercooler better versus in the charge pipe? Do you think it makes a difference?

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