legacycentral bbs

Can someone confirm that I'm reading this turbo map correctly

http://www.boostplanet.com/images/td05map.gif

The most air this turbo would be able to push through is about 0.29 kg/s or about 38.4 lb/min?


Also, looks like deadbolt's website got hacked
http://www.boostplanet.com

Yeah, I got 38.36 lb/min.
Whats the airflow rate of the EJ22t @ 85% VE?

I'm not sure. I'd have to dig through some documents to see if I can find it. I was looking at it to see what type of pressure drop I would see in using 2.5" dia intake piping from the airbox to the turbo instead of 3" reducing down to 2.5 at the turbo 90 deg inlet. I was using 6" of inlet piping for the numbers.

The numbers are pretty insignificant. Depending on the air temp, the pressure drop difference between 2.5" & 3" inlet piping range from 0.014 to 0.017 psi. It's not much, but if you look at the percent change, it's nearly a 61% decrease in pressure drop when going from 2.5" to 3". This is assuming an unfinished steel material. A smooth piping is around a 58% decrease in pressure drop when going from 2.5" to 3"

I've been playing with the numbers in an excel spreadsheet. I need to clean things up a little bit, but i was going to share the spreadsheet for people to play with if they wanted.

You know the crazy thing is the velocities. At that mass flow rate, 38.36 lb/min, the velocity ranges from 158 - 186 mph in the 2.5" piping, and 110 - 129 mph in the 3" piping.

Those velocity #s are for the turbo inlet?

Yup, the turbo inlet piping of roughly the diameters I mentioned.

Wouldn't a reduction in dia just before the turbo increase inlet velocity and density?

Creating a pressure drop in front of hte turbo decreases density, since faster moving air is at a lower pressure than slower moving air.


You want the least amount of restriction possible before any compressor. A lower amount of restriction means a compressor has to work less to make a given amount of pressure. This also equates to less heat generated by compression.

Just as in a venturi, a dia reduction means an increase in pressure for a given volume.

We're talking about vacuum though, not a pressurized venturi.

The pressure is still lower in the faster moving air.

Except that the dia doesn't increase again until after the turbo outlet.

All I'm saying is that in a smaller diameter of pipe, the faster moving air will be at a lower pressure than in the larger pipe. It's basic bernoulli.


There is a reason people make more power on a given turbo with a 4" intake vs. a 3" , and so on.


Obviously packaging is a restraint, especially with a stock location turbo, so Josh needs to do what is necessary to make it work.

Explain Bernoulli for those of us less educated.
All I'm saying is: for a decrease in area and a constant of speed, pressure increases. Or at a constant pressure, speed must increase. Either way decreasing the load on the turbo.

Sorry about the bernoulli reference. The general jist of his principle is that for an increase in velocity of a fluid, you have a simultaneous decrease in pressure.


If you are saying that velocity is constant and a change in area will affect pressure, then yes, you are correct. The problem is that we cannot look at this in terms of a constant velocity. Pumps and compressors move a specific volume of a fluid, so pressure and velocity are what change in a system.


In the end, we're just splitting hairs. A 16g doesn't move enough air for a step from 3" to 2.5" to be a big problem, especially if the step is smooth in nature. With 22T heads, its all a wash anyways.

Legacy777 wrote:The most air this turbo would be able to push through is about 0.29 kg/s or about 38.4 lb/min?

Yes, that's the most. But about 0.19 kg/s is what you want to aim for.

Legacy777 wrote:You know the crazy thing is the velocities. At that mass flow rate, 38.36 lb/min, the velocity ranges from 158 - 186 mph in the 2.5" piping, and 110 - 129 mph in the 3" piping.

pretty fast....

I believe the inlet on the TD05 is 2.5". I'm going to map out a proposed intake setup, and see what the difference is in the entire intake track, comparing a 3" section, reduced to 2.5" vs. a complete 2.5" setup.

As Dan mentioned, in the end I'm splitting hairs here. It's more just to fulfill my engineering minded curiousity. In reality, the pressure drop should be measured in, inches of water, not psi. If I can get the shop fabricating the intake to do it in 3" I will, but if not, 2.5" it will be.

Well.....I've got some intresting results. Some expected, some not expected.

Remember above how I said that a change from 3" to 2.5" piping is only 0.014 to 0.017 psi difference for a 6" long pipe? Well to give you an idea how insignificant that is compared to the rest of the intake piping:

2.5" to 3" reducer: 0.3 - 0.36 psi
2.5" 45 deg. elbow: 0.09 - 0.111 psi
two 2.5" 90 deg. elbows: 0.33 - 0.40 psi


The thing that I guess really doesn't make intuitive sense is that based on the numbers I came up with, you will actually get less pressure drop using 2.5" piping the entire way, vs. using a small section of 3" and then using a reducer.

Even if my numbers are off a little, I can double the 2.5" straight run of pipe and cut the equivalent length of the reducer by half and STILL have less pressure drop using the 2.5" piping.

My spreadsheet is a mess. I'll work on cleaning it up so I can post it without a decoder ring.

I've been thinking about the numbers from the reducer.....they're still kind of funky. I'm probably going to try and find another equation to use and see if I get the same results....

Considering the Reynolds number of air given it's viscosity, isn't it always in somewhat turbulent flow?


To it kind of makes sense though. If you are only changing the air's direction instead of the direction and area of the tube at the same time, would that be better?


At the same time, the larger piping for most of it would have less perceived friction on the air for that amount of flow.


arrrg. Fluids are efffing complicated, especially compressible fluids. What I would give for some baddass CFD software.

So, the only pressure pre-turbo is atmospheric despite airflow. And a reduction in diameter of pre-turbo ducting would only create turbulence in the flow.
Therefor, a consistent pre-turbo dia tubing, causing less turbulence, would be optimal?

93forestpearl wrote:Considering the Reynolds number of air given it's viscosity, isn't it always in somewhat turbulent flow?

Reynolds number for all the scenarios I looked at or 2.5 - 3.4 x 10^5. So yes, the flow is definitely turbulent flow. I don't think you'd have any piping that would be laminar flow in your intake track. There's just too much bends.

I went back and used the continuity equation just on the reducer, and the numbers I got did more or less confirm what the equivalent length results said. I got like 0.24 psid vs. 0.29 psid.

I think if you had a long enough run of 2.5" piping, the pressure drop losses of going with the larger 3" piping and then reducing would probably offset the reducer fitting's pressure drop.

93forestpearl wrote:At the same time, the larger piping for most of it would have less perceived friction on the air for that amount of flow

Actually, that's backwards. With the larger pipe, you have more surface area, i.e. more friction for the air to interact with the pipe wall.

For the most part though, the friction component is pretty steady. For all six scenarios, the friction coeficient only ranged from 0.02 to 0.021. This is for steel pipe, so the actual friction component of a "smoother" intake piping would be less. Plastic, copper, & brass are considered "smooth" and their friction factors ranged from 0.0132 to 0.0142. The lowest friction factor was the 2.5" dia piping at 32 degrees F. Highest friction factor was 3" at 120 degrees F.


You know, I hated fluids in college. I think it had a lot to do with the professor. When I studied to take the professional engineer license exam something just clicked, and fluids made sense for me. I don't know what it was. The one thing I learned that I kind of ignored in college was units. They can be your saving grace. If you know what the solution's units should be in, you can sometimes work backwards to see what you need to use to solve the problem based on what you are given.

The CFD programs are pretty crazy to try and use. I've been to a pipeline hydraulics class, and we basically reviewed a lot of fluids stuff, but they showed us some software they used for sizing pipelines, placing pump stations, etc. It was pretty involved...

beatersubi wrote:So, the only pressure pre-turbo is atmospheric despite airflow. And a reduction in diameter of pre-turbo ducting would only create turbulence in the flow.
Therefor, a consistent pre-turbo dia tubing, causing less turbulence, would be optimal?

Yes, the pressure pre turbo is atmospheric at the inlet/airbox. From there, as ou move through the intake piping, you get into an increasing vacuum, or negative pressure.

For the most part, the air in the intake track is all turbulent flow. I'm not sure I'd say turbulance is the driving factor in the increased pressure drop across the reducer. It's definitely a contributor though. I think the other quesiton you have to ask is, how long is your intake piping? Depending on the flow and the length of the intake piping, the smaller diameter piping make give you more pressure drop than the larger piping and reducer. For a short run, yes it looks like a consistant diameter piping would be more ideal.