Inlet Flow Testing

[BQTuning]

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.

Keep in mind I am not totally disagreeing with you....

Your leaving out another factor. Not only did it happen when raising boost on the "previous setup", it does not happen on the "new setup" pushing more power = more strain on the fueling system ever if I increased boost, richer fuel, the issue does not repeat as it did on the previous setup.

So what I am looking for is a "constructive" reason why then and why not now. The easy way out is when it makes no logical sense to say it was something else but not have a spec of theory of what that something else could be. When we conclude to this then we really dont understand things between hardware and DME logic.

 

[NoQuarter]

I have learned that the difference between "common sense" and factual measured results often lead to some pretty cool revelations.

Or not...

 

[BQTuning]

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.....

Thus my exact thoughts..... then we have significant difference in EGT and cylinder pressure between the banks ?

 

[The Convert]

Thus my exact thoughts..... then we have significant difference in EGT and cylinder pressure between the banks ?

Pretty much, and, effectively, an unbalanced rotating assembly due to varying loads bank to bank. So, it could potentially destroy a motor of power levels were pushed too high with too much of a difference. All speculation of course.

 

[135iTX]

Would merging the inlets at equal lengths mitigate any bank to bank variations? I wonder how hard that would be to incorporate given the space under the hood

 

[Torgus]

Like I said when these results 1st came out. You want the delta between the front and rear to be as close as possible.

Also remember a certain vendor was selling inlets for over $500 for $100 tops worth of silicone

The n54 is a profitable platform, for some.

The RB inlets are the highest quality I have seen fwiw.

Also the testing using different sized couplers is flawed from day 1. At least use apples to apples.

 

[Rob09msport]

We have crazy pressure differential on stock turbos like over 2 to 1 so at 20 psi the exhaust is seeing over 40 psi that is the only reason i can't see any real effect from more negative pressure on inlet side. Fluid dynamics I'm pretty sure support that compression is much more effective than vacuum that's why pumps can have cavitation issues and why it is much easier to push then pull. If the turbos were pulling exhaust out i could maybe see it but they don't , they get back pressure so i get that one turbo might flow more but that gets equalized.

 

[martymil]

@BQTuning you might be onto something here.

I've been doing the same testing here in oz as our inlets are even more problematic with rhd.

Something to think about, you guys are saying that inlets don't make a difference ?

Well if the rear turbo is suffering a little and the front turbo is spinning freely offcourse there will be bank differences.

Turbos are spinning at different rpm's and not exactly equal, its not a lot of difference but enough to cause discrepancies
at high boost levels, now if you back off the boost a little until the inlets are moving the same air volume they are going to work more equally.

This is what I found with my turbos & I can make more power with more boost but what I found is bank 1 turbo is spinning a lot faster than bank 2 and while this is all happening there is differences in egts and heat will cause different gas movements through the exhaust housings and this will cause bank 1 and 2 to run at substantially different cylinder temps.

So if one inlet flows even a little different at higher rpms the differences can be substantial.

This is why most people go single as those differences are gone and everything works more equal.

 

[The Convert]

@BQTuning you might be onto something here.

I've been doing the same testing here in oz as our inlets are even more problematic with rhd.

Something to think about, you guys are saying that inlets don't make a difference ?

Well if the rear turbo is suffering a little and the front turbo is spinning freely offcourse there will be bank differences.

Turbos are spinning at different rpm's and not exactly equal, its not a lot of difference but enough to cause discrepancies
at high boost levels, now if you back off the boost a little until the inlets are moving the same air volume they are going to work more equally.

This is what I found with my turbos & I can make more power with more boost but what I found is bank 1 turbo is spinning a lot faster than bank 2 and while this is all happening there is differences in egts and heat will cause different gas movements through the exhaust housings and this will cause bank 1 and 2 to run at substantially different cylinder temps.

So if one inlet flows even a little different at higher rpms the differences can be substantial.

This is why most people go single as those differences are gone and everything works more equal.

Pretty much same thing I said. When you look at it at the system level, rather than component, it seems like there really should be an effect.

 

[RSL]

So who's going to be the first with twins that have speed sensors? I don't think there's any question the banks don't run identical. Anyone who has changed their own plugs on a relatively stock N54 or has run TBI probably knows this. Mine started running more closely together after hybrids + inlets, at least plug-reading-wise.

Good argument for tuning or at least monitoring EGT by bank though. What would be great is actual individual bank WG control. It'd be an interesting test to bleed a fraction off bank 1 DC and slow it down relative to 2 or run one turbo at a time with really low target and note the DC difference for each to hit it. You'd know pretty quickly how much different they're working based on their inlet only and gap would only get bigger with more boost.

 

[martymil]

In rhd we even got more issues as our outlet pipes are squished especially on the rear turbo which makes things even worse.

I modify the rear turbo pipes for better flow but between the rear inlet and outlet it will get very expensive to make something better for very little gain.

The silicone pipes work far better but I've seen a few fail now due to how closely they run to the turbo's, I've been asked by a couple of owners of these to make something to stop this but its going to get costly.

But if your chasing that glory number it can be done.

 

[martymil]

So who's going to be the first with twins that have speed sensors? I don't think there's any question the banks don't run identical. Anyone who has changed their own plugs on a relatively stock N54 or has run TBI probably knows this. Mine started running more closely together after hybrids + inlets, at least plug-reading-wise.

Good argument for tuning or at least monitoring EGT by bank though. What would be great is actual individual bank WG control. It'd be an interesting test to bleed a fraction off bank 1 DC and slow it down relative to 2 or run one turbo at a time with really low target and note the DC difference for each to hit it. You'd know pretty quickly how much different they're working based on their inlet only and gap would only get bigger with more boost.

I don't think anyone will, those speed sensor setup is going to get very expensive to implement to prove a point.

Good luck but no one will especially when proven there is little gain to be had except a glory number at the expense of reliability and longevity.

 

[The Convert]

Vargas has done it.

 

[fmorelli]

So who's going to be the first with twins that have speed sensors?

@barry@3DM and I are planning them on our upcoming twin turbo builds.

Filippo

 

[RSL]

I don't think anyone will, those speed sensor setup is going to get very expensive to implement to prove a point.

Good luck but no one will especially when proven there is little gain to be had except a glory number at the expense of reliability and longevity.

Forgot to flip sarcasm switch on the speed sensors comment. Way too much for a quick check, but would be interesting data. Pulling the WGs to run one at a time to see what's up would be pretty painless though.

Vargas has done it.

Speed sensors or each twin individually? I'm sure we'd all be curious to hear any info on deviations bank to bank.

 

[The Convert]

Forgot to flip sarcasm switch on the speed sensors comment. Way too much for a quick check, but would be interesting data. Pulling the WGs to run one at a time to see what's up would be pretty painless though.

Speed sensors or each twin individually? I'm sure we'd all be curious to hear any info on deviations bank to bank.

As far as I remember, he's said they did backpressure, individual cylinder egt, wheel speed sensors, multiple iat sensors throughout the charge stream, etc. They use an aem data collector I think.

@Chris@VargasTurboTech

 

[RSL]

As far as I remember, he's said they did backpressure, individual cylinder egt, wheel speed sensors, multiple iat sensors throughout the charge stream, etc. They use an aem data collector I think.

@Chris@VargasTurboTech

Thanks, I do remember seeing that info now that you mention it, but don't remember if they bank to bank in there. Hopefully, Chris can chime in.

 

[Chris@VargasTurboTech]

Yes, we did speed sensors a long time ago. Backpressure, EGT, you name it, we've looked at it. You'd have to dig through history on other forums for all the details, and also understand that back when we did that tuning and hardware was not at the level of development that it is today. You can glean some info, but just take it with a grain of salt, that some things have changed a bit. What hasn't changed, though, is that to make the big boost numbers many chase after the shaft speeds required are absolutely ridiculous.

Currently the white car is fully instrumented with the Garretts on the car. Tony loves meaningful data and we have tons, much of which we've published through the years here and there for those who are interested, but the majority we use for internal knowledge and development.

Chris