Inlet Flow Testing

RSL

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It's buried in other forums. As usual, turned into a shit show for vendors, so maybe that was best. Good data, but Frankenturbo did the testing and we've been stuck with them ever since.
 

135iTX

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The “debacle” might refer to the variances in flow from inlet lengths? Or maybe that one of the OEM location inlets outflowed a relocation one? Or maybe that once filters are added none of it may matter.
 

RSL

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Is this the source that made him say inlets didn't help?
LOL no telling. Dude just posts chart after chart, half of which are meaningless without other data that doesn't get posted.

Not sure if the debacle is the flow difference front/rear or the mess that ensued after the tests.
 

Jeffman

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Interesting data.
I’d imaging you’d want your front and rear inlets to perform about the same on the flow test. The MMP front and rear inlets seem to do this. The stock and VTT’s don’t. Interesting.
 
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BQTuning

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Interesting. Im thinking of perhaps sending my CF kit in as a prototype custom Y inlet setup to compare with all of them. I would imagine all the stock location silicone inlets will have similar results.

I dont know how much of this matters, it seems like it does, but the rear stock location silicon inlets branches off for PCV connection which may have an impact on the flow tests ? If you look a the stock flow results they mirror the VTT flow results in character front vs rear

Great lesson to learn why the VTT front out performed the MMP front and rear significantly which have to do with the bends. I would bet if the rear VTT inlet is designed differently, eliminating the PCV support, it will improve air flow I think.
 
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Aaron

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Interesting data.
I’d imaging you’d want your front and rear inlets to perform about the same on the flow test

In an ideal world of course you would, however for all practical purposes the difference in flow front and rear will not make a discernable difference, and certainly not a big enough difference to even worry about. If the two banks stayed completely separate, ie 2 separate charge pipes, 2 separate intercoolers, and 2 separate intake manifolds then it'd be a pretty big deal. But with the outlets/charge side converging right away, the delta inlet flow is largely irrelevant.
 
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Jeffman

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In an ideal world of course you would, however for all practical purposes the difference in flow front and rear will not make a discernable difference, and certainly not a big enough difference to even worry about. If the two banks stayed completely separate, ie 2 separate charge pipes, 2 separate intercoolers, and 2 separate intake manifolds then it'd be a pretty big deal. But with the outlets/charge side converging right away, the delta inlet flow is largely irrelevant.
Good point!
 

Ilkka

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The results are biased because the VTT inlets are designed for larger turbos and the narrowest part of inlets, which are at the turbo attachment points, are clearly larger than the properly designed inlets for stock turbos. Obviously the smallest diameter is a very big factor on how a pipe flows. When these bad VTT inlets are attached to the stock turbos, they have the exact same small diameter at the turbo and what is worse, they have a more abrupt step right there than the properly designed inlets that fit well to the turbos. Sonwhen attached to the turbos, the others still flow the same as in the bench, except VTT, which flows worse.
 
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RSL

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In an ideal world of course you would, however for all practical purposes the difference in flow front and rear will not make a discernable difference, and certainly not a big enough difference to even worry about. If the two banks stayed completely separate, ie 2 separate charge pipes, 2 separate intercoolers, and 2 separate intake manifolds then it'd be a pretty big deal. But with the outlets/charge side converging right away, the delta inlet flow is largely irrelevant.
This true in a systemic output sense, but on the input side of things, the rear turbo has to work harder to pull in air, making it more inefficient and causing more load on the thrust bearing. Maybe the level is fine and the front just has it a lot easier, but pretty clear that inlets free up a good bit of pressure ratio, so they do relieve that stress overall. Too bad first thing everyone does with them on stock turbos is crank it to stupid boost levels and run them even harder.
 

RSL

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Interesting. Im thinking of perhaps sending my CF kit in as a prototype custom Y inlet setup to compare with all of them. I would imagine all the stock location silicone inlets will have similar results.

I dont know how much of this matters, it seems like it does, but the rear stock location silicon inlets branches off for PCV connection which may have an impact on the flow tests ? If you look a the stock flow results they mirror the VTT flow results in character front vs rear

Great lesson to learn why the VTT front out performed the MMP front and rear significantly which have to do with the bends. I would bet if the rear VTT inlet is designed differently, eliminating the PCV support, it will improve air flow I think.
Send them in man, would expect cool to see the results.
 
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BQTuning

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In an ideal world of course you would, however for all practical purposes the difference in flow front and rear will not make a discernable difference, and certainly not a big enough difference to even worry about.

I disagree with this to an extent based on some R&D I did a while back and my experience between stock, stock location silicone inlets, and custom built inlets. The OP source pretty much is inline with my findings and this is the first time I am seeing those air flow results.

I agree with you that the "difference in flow front and rear will not make discernible difference" which depends on how much airflow is being demanded. What matters is how much bias there is in the airflow which can have an impact on the fueling system from what I have seen.

Here is a complete stock N54 with a custom tune with an ethanol blend. I was testing the stock intake system on my Z4. Pay attention to the fuel trims, normal.

https://datazap.me/u/buraq/dyno-stock-tune?log=0&data=3-12-14-15-19&zoom=83-242

About 7 months later I went FBO with stock location silicon inlets (with PCV support) in one day. So it was time to turn things up. Again, pay attention to the the fuel trims

https://datazap.me/u/buraq/log-1456696348?log=0&data=4-21-23-24-29&zoom=32-78

In the above log more fuel is being added (deviating from target) at peak power "only on bank 2", which has a significant impact on the HPFP. IF I "lowered" boost, fuel trims would be fine, but when I raised boost we are back at deviating bank 2 trims and fueling going rich and the HPFP spiking downward. I went through two sets on silicone inlets 2.0" and 1.75" all results the same.

Now the only way to counteract this behavior was to bias the bank 2 scalar table in the affected RPM/Load area which technically is a band aid. You want to keep your scalar table values equal matching on the banks (not advised to bias scalar tables on the N54).

I have seen this same behavior on other cars and have asked customers to clean their rear filter which seems to to get more dirty than the front and it helped improve fuel trims on that bank.

I got fed up with my fueling behaving like this, almost thought it was the injectors, but my deep hunch from looking at previous logs led me to believe it was the inlets, so I decided to get custom inlets that were not all silicone and of a different design setup. So i decided to go the Carbon Fiber route.

960x537.jpeg.8d9c7e8468ce4e1cbaa9182cffa28c61.jpg

2000x1120.jpeg.10d2de86244442d398d3bc91a9494629.jpg

960x537.jpeg.70d39887ae0a48dea6e4c4e6d440709d.jpg


These inlets have no PCV support, in fact the PCV venting with a OCC connects to the intake box to recirculate. (This project is still undergoing developement)

Here is what my fuel trims look like now, pushing a hell of a lot more power than before

https://datazap.me/u/bqtuning/log-1525580155?log=2&data=3-21-23-24-29&zoom=67-127

I am now running equal and matching scalars on both banks.

I wasnt planning on bringing this forth till my project was done but might as well now to consider contrary thought on the topic to weigh in.
 
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Aaron

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Your fuel trim disparities have nothing to do with front and rear inlet flow difference, that's not even possible. When your outlets converge, any difference in air flow between cylinders is solely do to the intake manifold or intake runners in the head (Which of course aren't changing). You could literally weld the intake of bank 2's turbo closed, and your airflow between cylinders (And thus, your fuel trims), wouldn't change.

Sorry, but something else is causing what you're experiencing.
 

BQTuning

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Your fuel trim disparities have nothing to do with front and rear inlet flow difference, that's not even possible. When your outlets converge, any difference in air flow between cylinders is solely do to the intake manifold or intake runners in the head (Which of course aren't changing). You could literally weld the intake of bank 2's turbo closed, and your airflow between cylinders (And thus, your fuel trims), wouldn't change.

Sorry, but something else is causing what you're experiencing.

Perhaps, still unable to narrow down what was causing it, and it may have been a coincidence that coincided when things were changed
 

Aaron

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There's no perhaps about it, your trim disparities had nothing to do with the differences in airflow between the front and rear inlets. Coincidence /=/ causation.

I don't know a whole lot on N54 specific tuning, but you mentioned it happened when you raised boost. As overall pressure, and therefore airflow, increases, the disparities between individual cylinder airflow are magnified accordingly, and thus fuel trims would get further and further off as you increase boost/cfm.
 

Rob09msport

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There's no perhaps about it, your trim disparities had nothing to do with the differences in airflow between the front and rear inlets. Coincidence /=/ causation.

I don't know a whole lot on N54 specific tuning, but you mentioned it happened when you raised boost. As overall pressure, and therefore airflow, increases, the disparities between individual cylinder airflow are magnified accordingly, and thus fuel trims would get further and further off as you increase boost/cfm.
I was gonna say the same thing we have y pipe outlet and single charge pipe to throttle body and then splits back to 6 at intake runner i understand the confusion cause for a tuner from dme pov their is 2 banks and 2 turbos and 2 o2 sensors but we have an inline 6 with a common rail setup and single plane intake manifold
 

The Convert

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I largely agree with Aaron, but BQTuning also has a point. While the charge air does converge into a single tube and a single throttle body. The front and rear turbos will spool at different rates based on the inlet's flow rate and that will have an effect on the rate the exhaust exits the head and the amount of air that is drawn into the cylinder. So, you could actually make more power on the front bank and less on the rear. How big will these disparities be??? I can't honestly say, but every part of the system will have an effect on the rest of the system.