How much boost am I making? (Log Screenshot inside)

[stanielz]

Hi all,

I am trying to answer the question, how much boost am I making vs how much am I supposed to be making? I have a screenshot of a WOT attached. I have a Gen 2 5.0 and a Gen 2 Whipple on a 3.5 pulley with Kooks LT and green cats. All the documentation I see online and from searching the forums seem to apply to Gen 3+ whipples which, from my understanding, make more boost than the gen 2 whipples (assuming pulley is the same size).

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[K4fxd]

My guess is 8 psi

 

[SolarFlare]

Based on airload maybe 10-11.

 

[K4fxd]

.

 

[raptor17GT]

if the Manifold Absolute Pressure is showing 27.4 psi and Barometric Pressure is 13.9 does that not mean 13.5psi of boost?

 

[stanielz]

if the Manifold Absolute Pressure is showing 27.4 psi and Barometric Pressure is 13.9 does that not mean 13.5psi of boost?

Thats what I am not sure about... was just looking for confirmation.

 

[K4fxd]

Airload is 1.761 baro is 13.9 So airload of 1 is 13.9 13.9*.761 is 10.577

10.5 PSI of boost.

 

[stanielz]

Airload is 1.761 baro is 13.9 So airload of 1 is 13.9 13.9*.761 is 10.577

10.5 PSI of boost.

so the stock kit was advertised as 10-11 psi (stock headers, 3.75 pulley)... I've gone down 2 pulley sizes to 3.5 + LTs. I feel like I am missing something

 

[2022 Mach 1]

so the stock kit was advertised as 10-11 psi (stock headers, 3.75 pulley)... I've gone down 2 pulley sizes to 3.5 + LTs. I feel like I am missing something

LTH reduces back pressure which reduces boost. Probably started at 10 stock, lost 2psi with the headers and then gained it back with the two pulleys Seems about right

 

[K4fxd]

feel like I am missing something

The only way to know for sure is to put a mechanical boost gauge on the manifold. It's all inferred by using the MAF signal and the SD tables along with who knows what else. So it is only as good as the tuner. I doubt they hooked a MAP sensor and spent the weeks it would take to get it perfect. Also there will be some blow through due to the better exhaust.

You really are not losing anything. I'm surprised by the cool intake air. Unusual with a PD.

 

[raptor17GT]

Airload is 1.761 baro is 13.9 So airload of 1 is 13.9 13.9*.761 is 10.577

10.5 PSI of boost.

Surely Manifold Absolute Pressure is what is measured and is saying 27.4psi which being absolute and not gauge makes sense in a boosted engine. Trying to learn as i see this debate on boost levels a lot on here. My previous JDM turbo car, MAP did the calculation for the fuelling so if it pumped in fuel for your 10.5psi calculation yet the gauge said 13.5psi, that's short on fuelling and ka-boom engine. Just asking for me as I can't get my head around it. MAF fine, multiplier away but MAP i don't get changing the reading by a ratio

 

[Ruiner46]

The only way to know for sure is to put a mechanical boost gauge on the manifold. It's all inferred by using the MAF signal and the SD tables along with who knows what else. So it is only as good as the tuner. I doubt they hooked a MAP sensor and spent the weeks it would take to get it perfect. Also there will be some blow through due to the better exhaust.

You really are not losing anything. I'm surprised by the cool intake air. Unusual with a PD.

This is correct. The cool intake air is probably the wrong sensor since MCT and IAT are the same number. If HPTuners is up to date and this is the Whipple tune, then the proper sensor to log is IAT2. The latest versions of HPTuners stopped using MCT for some reason... at least in my case (gen2 2.9L with Whipple tune).

raptor17GT, MAP is not an actual sensor, it is inferred from MAF and the speed density tables. Looking at any inferred or calculated value could be completely wrong depending on how detailed the tuner was with adjusting tables. Even air load could be rescaled. On my Whipple tune, barometric pressure is set to a static value since the car doesn't have a sensor. So even the baro is wrong.

The logged MAF value in this case is hitting the maximum limit for the PID being used, so it is not even the right airflow, but the ECU uses the right airflow internally for its calculations.

 

[K4fxd]

The coyote does not have a MAP sensor. Fueling is taken care of by the O2 sensors. Manifold absolute pressure is inferred. Also this is a gen 2 so Baro is inferred. Best we can do is an educated guess

 

[smokescreens]

The answer to "how much boost am i making" is always "not enough".

Remember boost is really a measure of resistances. Headers, ported heads, cams, ect make the engine breathe better so "boost" will drop as a result.

 

[Whitedevil95]

WHen i had a gen 2 whipple with a 3.5 Pulley it made about 12.5 psi on stock headers and cats. Now with the Gen 3 on a 3.5 pulley with free flowing exhaust and long tubes it makes 13.5psi.

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