Using a supercharger for a blow through flow bench

[gte]

All of my vehicles are turbocharged and I was wondering if using compressed air would be more beneficial for my testing?

It seems like a cabinet housing a supercharger and a variable speed motor to drive it would be beneficial, but I'm new and don't want to fail at reinventing the wheel. What is everyone's thoughts on this?

Has anyone used multiple air flow meters to read individual intake manifold runners when testing an entire manifold? Is there an electronic device that can read 8 mass air sensors at the same time?

[gte]

No one has done this with all of the years of information here?

[Tony]

It has been done, my own flow bench uses a large centrifugal blower, 10Hp motor, and variable speed drive.
Flow benches have also been built with motor driven GM roots blowers.

For every bench using a supercharger, there are probably at least a hundred other benches in operation around the world using vacuum cleaner motors.

If you have all the parts, supercharger, motor, and variable frequency drive, it will certainly make you a very nice flow bench.
There are both advantages and disadvantages of doing it that way.

The main disadvantages of a big blower bench are cost, physical size, and the difficulty of packaging. Vacuum motors are small, low cost, more or less readily available, and very compact. And a bench design using them is a very well established and proven way to build a successful problem free flow bench.

The main advantage of using a large diameter centrifugal blower is that the pressure output remains pretty flat over a very wide flow range. If flow is blocked the stalled pressure does not spike upward as it will with high rpm vacuum motors. Setting exact test pressure is a lot less touchy.
Both the motor and blower operate at low rpm and will last a lifetime and probably make less noise. Vacuum motors are mass produced with planned obsolescence in mind. Brushes, commutators, and bearings, have a finite life when run at 20,000+ rpm.

A roots blower bench would be interesting. Reversing the flow is dead easy, so the flow path stays the same. The output side of the blower will pulse, but the intake side does not. If flow is blocked, the pressure differential generated will be huge and could be dangerous. It has been done, but I have never seen a bench like that in operation.

Big blower benches tend to be more efficient power wise. If your electricity supply is strictly limited, you will very likely get more airflow per watt than with less efficient vacuum cleaner motors.
Few people that start out in this realize how much electrical power is actually required to power a really large flow bench.

In the end its how much electrical power you actually have available that usually decides bench final airflow capacity.

[gte]

Hi Tony,

Thanks for the reply. Do you use individual maf sensors to measure each port/manifold runner?

Also could you post some pictures of your setup? If you did it again would you build a roots or centrifugal type design?

It has been done, my own flow bench uses a large centrifugal blower, 10Hp motor, and variable speed drive.
Flow benches have also been built with motor driven GM roots blowers.

For every bench using a supercharger, there are probably at least a hundred other benches in operation around the world using vacuum cleaner motors.

If you have all the parts, supercharger, motor, and variable frequency drive, it will certainly make you a very nice flow bench.
There are both advantages and disadvantages of doing it that way.

The main disadvantages of a big blower bench are cost, physical size, and the difficulty of packaging. Vacuum motors are small, low cost, more or less readily available, and very compact. And a bench design using them is a very well established and proven way to build a successful problem free flow bench.

The main advantage of using a large diameter centrifugal blower is that the pressure output remains pretty flat over a very wide flow range. If flow is blocked the stalled pressure does not spike upward as it will with high rpm vacuum motors. Setting exact test pressure is a lot less touchy.
Both the motor and blower operate at low rpm and will last a lifetime and probably make less noise. Vacuum motors are mass produced with planned obsolescence in mind. Brushes, commutators, and bearings, have a finite life when run at 20,000+ rpm.

A roots blower bench would be interesting. Reversing the flow is dead easy, so the flow path stays the same. The output side of the blower will pulse, but the intake side does not. If flow is blocked, the pressure differential generated will be huge and could be dangerous. It has been done, but I have never seen a bench like that in operation.

Big blower benches tend to be more efficient power wise. If your electricity supply is strictly limited, you will very likely get more airflow per watt than with less efficient vacuum cleaner motors.
Few people that start out in this realize how much electrical power is actually required to power a really large flow bench.

In the end its how much electrical power you actually have available that usually decides bench final airflow capacity.

[Tony]

Do you use individual maf sensors to measure each port/manifold runner?

Not sure there is really any value in doing that.

Inlet manifolds on a running engine suffer from severe induction pulsing in each runner, which is greatly influenced by cylinder firing order, and where the throttle body is situated with respect to everything else.

You only have to look at manifolds designed for either carburetors or EFI to see the weird humps, bumps, steps and curves in an attempt to get even air fuel distribution working over a wide range of rpm and loads in a STOCK engine.

Someone bolts on a turbo and doubles the original airflow and horsepower, and wonders why the exhaust gas temperatures are all over the place because of uneven air distribution. What it does on a flow bench with steady flow is nothing like what is going to happen in a real running engine, so why even bother ?

I know someone that tried turning an engine with an electric motor to try and get the induction pulsing in a way that he could measure a few things. It was hopeless. What happens at valve overlap with all the heat and violence in the combustion chamber and tuned exhaust, makes nonsense of what happens with an electric motor drive, and everything at room temperature.

Only way to study all this is on an engine dyno.
If one cylinder is obviously not right, you need to do something with air distribution, and its not very likely going to show up on a steady flowing airflow bench, even with wet flow.

My flow bench is now very old and so am I. Have not used it in many years.
If I was going to ever build another flow bench I would almost certainly now buy the Forum plans and use vacuum cleaner motors.

I might consider using a large centrifugal blower for some obscure back to back testing for muffler and exhaust pipe testing, where flow is very high, and back pressure minimal. Might also be good for some intercooler and induction pipework back to back testing, air filter testing etc. But that is not strictly a proper flow bench. Just a really rough comparative flow measurement at flow volumes much higher than a typical bench might be able to reach.

Just fit an orifice plate into a large flat sheet mounted over the inlet hole of a centrifugal blower. Then blow test your piece with turbulent air. That is how it will run in the car anyway, and should give some usable indications. The air will be heated by the blower, and the flow turbulent, but for strictly A/B comparative testing should be acceptable.

[gte]

The value I see in it is that I have a 6 cylinder common plenum, which is more cylinders than can take advantage of tuned length runners for the Helmholtz effect. My goal is to build a manifold that will allow the cylinders to fill the best due to the least amount of turbulence created by the throttle body and manifold design, since I cannot alter runner length or divide the manifold to 3 cylinder sections because of packaging constraints.

The second best way to test the manifold is a flow bench with compressed air, similar to ideal running conditions on my turbocharged direct injected 6 cylinder, unless I can get a 750hp engine dyno for 2000 dollars or less, this is my best option. It's a good starting point for me to get my design close to optimal (flow) in ideal conditions and I will move to a chassis dyno afterwards, which I do have.

I want to compare its flow to the stock manifold and throttle bodies in the initial design phase and then see what happens on the chassis dyno after. Maybe you are correct that it would be pointless, but I think my theory has value in the flow comparisons to the stock manifold. I know that Hogan Manifolds said they could build me a manifold and they do not have an example of my engine to test on an engine dyno ... do you know if they have something other than the engine on the dyno that allows them to optimize their intake manifolds?

Most of all, I want to learn, experiment and tinker, taking theory and seeing what empirical evidence is produced.

Do you use individual maf sensors to measure each port/manifold runner?

Not sure there is really any value in doing that.

Inlet manifolds on a running engine suffer from severe induction pulsing in each runner, which is greatly influenced by cylinder firing order, and where the throttle body is situated with respect to everything else.

You only have to look at manifolds designed for either carburetors or EFI to see the weird humps, bumps, steps and curves in an attempt to get even air fuel distribution working over a wide range of rpm and loads in a STOCK engine.

Someone bolts on a turbo and doubles the original airflow and horsepower, and wonders why the exhaust gas temperatures are all over the place because of uneven air distribution. What it does on a flow bench with steady flow is nothing like what is going to happen in a real running engine, so why even bother ?

I know someone that tried turning an engine with an electric motor to try and get the induction pulsing in a way that he could measure a few things. It was hopeless. What happens at valve overlap with all the heat and violence in the combustion chamber and tuned exhaust, makes nonsense of what happens with an electric motor drive, and everything at room temperature.

Only way to study all this is on an engine dyno.
If one cylinder is obviously not right, you need to do something with air distribution, and its not very likely going to show up on a steady flowing airflow bench, even with wet flow.

My flow bench is now very old and so am I. Have not used it in many years.
If I was going to ever build another flow bench I would almost certainly now buy the Forum plans and use vacuum cleaner motors.

I might consider using a large centrifugal blower for some obscure back to back testing for muffler and exhaust pipe testing, where flow is very high, and back pressure minimal. Might also be good for some intercooler and induction pipework back to back testing, air filter testing etc. But that is not strictly a proper flow bench. Just a really rough comparative flow measurement at flow volumes much higher than a typical bench might be able to reach.

Just fit an orifice plate into a large flat sheet mounted over the inlet hole of a centrifugal blower. Then blow test your piece with turbulent air. That is how it will run in the car anyway, and should give some usable indications. The air will be heated by the blower, and the flow turbulent, but for strictly A/B comparative testing should be acceptable.

[Tony]

Individual inlet runner tuning for normally aspirated engines is a pretty well understood art. Computer programs such a pipemax are excellent for achieving highest volumetric efficiency over a limited rpm range.

Designing an effective common plenum seems to be the fly in the ointment, because the individual runners are then no longer individual, and the more cylinders you have feeding off the same plenum, the more complicated it all becomes..

Its been a very long time since I messed with six cylinder turbo engines, but the ideal for either an inline six, or a V6 would have to be two exhaust manifolds, two turbochargers, and two inlet manifolds. There is much less cylinder to cylinder interference with only three cylinders per manifold. Each cylinder gets a clear unmolested 240 degrees in which to work.
Its probably the ideal number of cylinders to have for turbocharging.

Apart from that, I have been out of straight turbocharging for a very long time.
Over the last thirty years or so, all of my efforts have been towards twincharging, or combining a positive displacement supercharger and a turbo which eliminates just about all of the problems that either supercharging or turbocharging have.
It combines the best characteristics of each without any of the disadvantages either has individually.