Hondaswap.com | Honda Technical & JDM styling Forums

Turbo&Auto · 07-31-2006, 10:18 PM

enlighten me then

Calesta · 07-31-2006, 11:20 PM

It's going to take about an hour of typing...

reikoshea · 07-31-2006, 11:59 PM

dont act like you got shit to do

Calesta · 08-01-2006, 12:47 AM

I do.

Calesta · 08-01-2006, 04:55 AM

Ooooooooooooook. This is why you're both right and wrong, and both totally missing the point.

1. LHO is correct in saying that psi is psi no matter what turbo it comes from. Pressure is pressure. It is measured at the intake manifold, so if your boost gauge shows 4psi, you have 4psi. It's that simple. He is also correct in saying that the bigger turbo just applies that 4psi later in the rev range of the engine.

2. He is NOT correct in saying that the bigger turbo will make the same amount of power at the same pressure level as the smaller turbo- not unless both are pushing the same pressure at the same engine RPM, and at the same efficiency.

3. LHO's post about volume vs flow rate vs fixed volume of the intake manifold is correct. Pressure is pressure. 5psi on a manifold is going to flow the same amount at the same engine RPM no matter what turbo is pushing it.

4. T&A is correct in saying that 300cfm will make more power than 200cfm provided you have the fuel to use it- but only partially correct.

5. LHO's comeback saying that 10psi will make 250whp (arbitrary example) no matter which turbo its from is incorrect. He's leaving something out.

6. T&A's last comeback talking about different compressor maps is starting to show some understanding about the whole debate.... but doesn't lay it all out there.

Alrighty T&A (and LHO), let's all go to school.

----- I know a lot of you know a lot of this stuff already, but just sit tight. -----

Engines are big energy converters / reactors. They convert the latent energy contained in fuel to thermal energy that pushes pistons/rotors around, which act on lever arms (rods, crankshaft) to create torque. Power is a function of that torque applied over time. The faster you apply the torque (higher rpm), the more power you get- even if you have the same amount of torque.

Higher amounts of fuel and air mean more energy is released in the reaction (combustion), so you get more torque and therefore more power.

Now air on its own isn't the important part. Oxygen is- that's what reacts with the fuel to make a nice boom and push your pistons around. Density is the key. With turbochargers, when you look at a compressor map, you see all those wonderful efficiency islands. Higher efficiency values mean higher air densities- and therefore higher oxygen densities.

Take an imaginary box. When it's full, this imaginary box holds one pound of air. Now let's squish that air to half its size- the equivalent of 14.7psi (1 atm) of boost. Squish more air the same amount and fill the box to the top. At 100% efficiency (not possible, but imagine), you'll have exactly two pounds of air in the box. Twice the air means twice the potential to burn more fuel, right? With 2 pounds of air in the box (or engine) that's designed to hold only 1 pound, you have the opportunity to burn twice as much fuel and make twice as much torque.

Let's say your turbo is only operating at 80% efficiency. At 1atm (14.7psi) of boost, you'll spend 20% of your turbo's work generating heat, and only 80% of the work will go to compressing air. The air heats up, and you have only 1.6 pounds that are usable to potentially burn fuel, not 2 pounds like you had before. The box is still full to the top. You have the same pressure, the same volume (so the same FLOW), but less oxygen available to burn fuel.

All of this assumes you have a box with no hole in it.

Your engine is this box with a hole in it. Well, I guess your intake manifold is, but you get the idea. The faster your engine is turning, the bigger the hole gets. This is where flow rate comes into play. The faster your engine runs, the more flow the turbo has to provide to establish the same pressure ratio. That's why small turbos run out up top- because they can't move enough air to maintain pressure against the engine once the engine is gobbling up more air.

Addressing points:

1. Yes, pressure is pressure- but assuming everything else is the same. LHO has to assume that both setups have engines of the exact same displacement running at the same speed. With a 2 liter engine running at a constant 4000rpm, a turbo pushing 4psi against it is always pushing the same volume of air, no matter what the turbo size. Pressure is pressure.

2. On the bigger turbo making the same amount of power but just at a different RPM, that makes no sense. LHO is already stating that the larger turbo will make boost at a higher engine speed than the smaller turbo, and that's correct. Everyone knows that. Assuming the same efficiency, a small turbo pushing 10psi at 5000rpm will make half as much power as a turbo pushing 10psi at 10000rpm. Both engine setups are making the same amount of torque- they're both burning the same amount of fuel per engine revolution- but since the 10000rpm engine is applying that force twice as fast as the 5000rpm engine, it makes twice as much power. Easy. So... if the larger turbo is making the same pressure as the smaller turbo but does it higher up in the rev range of the engine, then it will make more power at the same pressure level, not the same amount of power. That's just a function of engine speed.

I'm sure homie LHO would come back with something like "oh, the small turbo can make 10psi in the same place that the big turbo can," and he might be right- but then this is where all the efficiency fun comes into play. The small turbo might be able to push 10psi at 10k just like the bigger turbo, but it won't do it as efficiently as the larger turbo. Even at the same flow rate and the same pressure, the larger turbo will flow more MASS into the engine because it is operating more efficiently. The small turbo is just generating heat because it's out of range, while the larger turbo is working pushing more air. Same pressure, same CFMs, different mass flow rate, different power outputs.

3. See #1. 5psi is 5psi, assuming the engine is consuming air at the same speed in both cases (box with hole in it). You have a constant cross section for air to flow across, you have the same pressure differential, and you have the same amount of air going out. Everything is identical.

4. Yes, more flow = more power... generally. When you're reading the compressor maps for a turbocharger, they're mapped with pressure ratio vs flow rate. Just because a turbo can flow a certain amount of air volume doesn't mean that it can succesfully push that volume into an engine at a certain pressure. You could theoretically have a turbo that could push 500cfm, but only be capable of pushing it at 1psi. Any more resistance, and you don't get that flow rate. The turbo must have both the capability to flow the volume AND be able to maintain pressure to push it into an engine.

Also, talking about flow on its own without reference to the density of that flow is misleading. Flow on its own doesn't tell you anything. You can flow the same volume of light sugar water and thick molasses- and they will be the same flow rate- but you get totally different amounts of sweetness, right? I generally think that people who just talk "oh but this one FLOWS more CFMs" without mentioning efficiencies or air densities doesn't fully understand what they're talking about.

5. See efficiency.

6. Yay T&A! Talking about compressor maps... but it's not just the volume vs pressure that are important- the efficiency islands are the most important part of the compressor map.

-----

So basically- T&A is a lot more right than LHO, but LHO is technically right in most of his stuff. He just doesn't have the whole picture.

I hope that clears things for some people and doesn't muddy the waters for too many....

Turbo&Auto · 08-01-2006, 07:44 AM

Thanks for the writeup, I need to read it a couple more times to fully soak it all in. Some of it I do know, but a lot is new and good info

I realize about efficiency and somewhat how to read a compressor map, still learning that aspect of turbocharging. I couldnt get to that point with this guy though, he didnt want to hear anything but 4psi is 4psi and you cant make anymore power at the same psi no matter the turbo. I got a bit derailed and skirted some of the more important issues. We were also assuming them to be on the same motor within the same kind of group of turbos too. Like T25's, GT28's. The guy Wish that I was talking about has a Matrix like mine and originally had a T25 on it, he swapped out to a Big16G equivelant turbo and pickeed up a lot of power without anymore boost. He couldnt understand how that was possible and I was just lacking all the terminology to get it across properly.

Thanks for the info, you rly can never learn too much about turbos. If you have any other sites that you could point me to for reading info I would appreciate it. I google the shit, but you get a mixed bag of peoples opinions and whats actually real.

MikeBergy · 08-01-2006, 08:06 AM

lol. Mike, I have been in the process of writing this exact same writeup for the last couple of hours. Then I ran into this post while taking a mental break. how odd. I guess we have both been thinking about the noobs with all their PSI questions. You put out good points. The box with the hole in it analogy is great. I like to think of it as water-in-water-out. If you have a compressor that can maintain a set pressure within the same efficiency island (i.e. 14psi) from the time it is fully spooled up to the engine's redline, then you are good, provided that you aren't lagging too much. If your turbo moves away from the higher efficiency island, you'll start heating up the intake temps, lowering intake air density.

If you want to size a turbo correctly, you gotta do the calcs. It's not too much work. Here is a good site that has a lot of compressor maps available. Turbo and Supercharger Maps

Turbo&Auto · 08-01-2006, 09:05 AM

I've read it a few times now, its starting to sink in more and more and make more sense too. I think I'm starting to see the whole picture instead of a narrow view of what doesnt matter as much.

I'm still hazy on compressor maps though. Every place I read trying to figure out how to read a compressor map misses all kinds of important factors. Do you have a site that clearly can explain how to read a compressor map?

reikoshea · 08-01-2006, 11:57 AM

okay, so there was a lot to write.

good work yizzle.

MikeBergy · 08-01-2006, 06:11 PM

Okay. It's pretty easy if you know what all the math mumbo jumbo means.
These particular maps compare a t3 'super 60' compressor and a t70 compressor. I picked the t70, because it has been showing up a few times over the past week or so.

Start with the vertical axis. The vertical axis displays the outlet:inlet pressure ratio. For example - if the inlet is at atmospheric standard, and you read 2.0 on the chart, the exit pressure will be twice standard atmospheric pressure, which 29.4psi absolute, or 14.7 psi gauge. Gauge pressure is what you will see on the boost gauge if it is an SAE gauge.

Next, the horizontal axis. This is simply the MASS flow of the compressor, corrected for standard temperature and pressure. 'w' is a standard symbol for mass flow. (T1c/545)^.5 is the correction for standard temperature, where T1c is the ambient temperature of the air at the compressor inlet in degrees Rankine. P1c/28.4 is correction for standard pressure.

Temperature and pressure corrections are commonly shown in equations as the greek symbols theta and delta respectively. I have honestly never seen 28.4 used in the delta term, as standard pressure is 14.7 psia, so I am thinking it may be a typo. Regardless, the corrected flow is just a way to comparing compressor performance test results from two different climates, say florida and california, whose average atmospheric temperature and pressure will be fairly different at each location. They are just used to get everything on the same page, number wise. Here is some literature on corrected flow. Gas Semantic Definition: Corrected Mass Flow

Now to the graph. You'll notice there are concentric circular blobs drawn on the page. These are called efficiency islands. While the areas within each area may not be exactly a certain efficiency, it can be said that within each island, efficiency is equal to or greater than that which is shown on the line. For example, any operating point of the compressor within the innermost island on the super 60 map will operate with at least 74% efficiency. That is to say, 74% of the work done on compressor by the turbine shaft will actually compress the air. The rest of the work will be turned into heat. The higher the efficiency, the better. This is pretty straightforward.

The lines moving somewhat horizontally across the graph are lines of constant rotor RPM, corrected of course. These are just lines showing how pressure ratio of the compressor varies directly with mass flow given a constant rpm. Not really useful imo in regards to applying it to anything, but it's there.

Far left, you'll see a surge line. You've heard of compressor surge, no doubt. Basically this is the point at which the rotor blades will stall, causing a drop in pressure ratio. As the pressure ratio drops, the blades begin moving air again. Then, it proceeds to cycle itself between stalled and unstalled conditions. This creates pressure pulses which can really screw things up mechanically, because the compressor is no longer steady state, and is pretty much out of control.

I created a couple of lines for comparison of the two maps. The red line is a typical operating line along which a compressor will most likely be operating. Compressors are much more likely to follow a path of greatest efficiency. I just showed that at a single operating point of 14.7 psig (p2/p1 = 2.0), the t70 is capable of flowing MUCH more air than a 'super 60' t3, about twice as much.

As Mike said, the engine only sees manifold pressure, and intake temperature. You could be boosting 12 psi on both compressors from the time the turbo spools up to the engines redine. But the difference lies in the efficiency islands. You may be pushing 12psi to both systems, but the super 60 might be adding 20% more heat to the intake charge than the t70.

The t70 is a huge beast. It's not a good choice for small honda applications, as it would take so much exhaust gas flow to spool it up, you'd be near your redline before you even achieved a desirable boost level.

Calesta · 08-01-2006, 07:33 PM

Quote:

Originally Posted by Turbo&Auto

Thanks for the writeup, I need to read it a couple more times to fully soak it all in. Some of it I do know, but a lot is new and good info

I realize about efficiency and somewhat how to read a compressor map, still learning that aspect of turbocharging. I couldnt get to that point with this guy though, he didnt want to hear anything but 4psi is 4psi and you cant make anymore power at the same psi no matter the turbo. I got a bit derailed and skirted some of the more important issues. We were also assuming them to be on the same motor within the same kind of group of turbos too. Like T25's, GT28's. The guy Wish that I was talking about has a Matrix like mine and originally had a T25 on it, he swapped out to a Big16G equivelant turbo and pickeed up a lot of power without anymore boost. He couldnt understand how that was possible and I was just lacking all the terminology to get it across properly.

Thanks for the info, you rly can never learn too much about turbos. If you have any other sites that you could point me to for reading info I would appreciate it. I google the shit, but you get a mixed bag of peoples opinions and whats actually real.

I'm glad it helped you.

I'm still trying to figure turbos out. The compressor side is easy- but what I want to know is how to crunch to the math on the spool characteristics of a given turbocharger. That's a lot more difficult... you have to take into account the drag on the turbine from the amount of work the compressor is doing, then deal with exhaust velocity, density and temperature. Fun stuff. I think Bergy probably knows why I would be wanting to know how to calculate spool characteristics...

That guy you were arguing with on the board knew some good basics, but he was still missing most of the picture- even though he thought he knew it all. We all have lots to learn.

Quote:

Originally Posted by MikeBergy

lol. Mike, I have been in the process of writing this exact same writeup for the last couple of hours. Then I ran into this post while taking a mental break. how odd. I guess we have both been thinking about the noobs with all their PSI questions. You put out good points. The box with the hole in it analogy is great. I like to think of it as water-in-water-out. If you have a compressor that can maintain a set pressure within the same efficiency island (i.e. 14psi) from the time it is fully spooled up to the engine's redline, then you are good, provided that you aren't lagging too much. If your turbo moves away from the higher efficiency island, you'll start heating up the intake temps, lowering intake air density.

If you want to size a turbo correctly, you gotta do the calcs. It's not too much work. Here is a good site that has a lot of compressor maps available. Turbo and Supercharger Maps

Heh. Mike and Mike both engineers (well, you're still in school

), both thinking about posting the same information. Gotta love it.

I teach by analogy. I've found that it works well, especially since I'm always trying to explain really complicated ideas to non-technical people (like Katie). It's also one of the most effective ways to teach 6th grade kids complex concepts in chemistry and physics. That was a fun bunch of years. It's badass when you get a 10 year old to truly understand the Bernoulli effect, the math behind chemical reactions, centrifugal force, distributed loading etc. It's a good feeling.

So you like the box with the hole in it huh? I'll have to write up a series of more formal articles and post them up somewhere.

Quote:

Originally Posted by Turbo&Auto

I've read it a few times now, its starting to sink in more and more and make more sense too. I think I'm starting to see the whole picture instead of a narrow view of what doesnt matter as much.

I'm still hazy on compressor maps though. Every place I read trying to figure out how to read a compressor map misses all kinds of important factors. Do you have a site that clearly can explain how to read a compressor map?

Sinking in is good.

Mike's explanation of the compressor map reading is pretty good. There really isn't much to it. Once you understand how to look at the map, you'll slap yourself in the forehead and go "duh."

Quote:

Originally Posted by reikoshea

okay, so there was a lot to write.

good work yizzle.

Thanks homie.

Quote:

Originally Posted by MikeBergy

Okay. It's pretty easy if you know what all the math mumbo jumbo means.

Mike- good writeup on reading compressor maps! I created an Excel sheet that I use to approximate volume and mass flows based on engine displacement, intake temp, and constant volumetric efficiency (uh oh, another concept to explain!). I apply that information to the compressor maps to get a rough idea of how an engine will perform.

Here's a little something I made a while back to size up a 1G DSM 14b turbo to the Nissan Hardbody's KA24E engine. There are a few assumptions- constant volumetric efficiency for one- so it's not a perfect real world approximation, but it's close enough to get a rough idea of how things should fall:

The graph isn't all that clear on its own, but hopefully the lines and how things sit give you an idea of how to estimate the operating range of a turbocharger vs a specific engine.

reckedracing · 08-02-2006, 09:51 AM

nice write ups guys, excellent info
now if i could just find a map for my IHI turbo
lol

Turbo&Auto · 08-02-2006, 10:07 AM

Thanks for the rundown. What was puzzeling me when I looked at maps was the fact that you need to add atmospheric pressure to the equation. I would convert 10psi to the equivelent used on the chart and it wouldnt even be on the map. Then yesterday I added 14.7 to the amount of boost I planned on running and things started to make a LOT more sense.

Thanks again for the writeups guys, I rly love to read about turbos and how everything works. I seem to learn at least 2 things everytime I sit down and read more and more.

Edit: After looking at that 14b map, I'm glad I went with a larger turbo. It would've choked out early. The Big16G I'm using will make good power without a lot of heat around 10-12 and then be much more efficient in the area I want to track the car at, 15-17psi. BUT, it does look like I could've still went larger.

Turbo&Auto · 08-02-2006, 10:19 AM

This 20G might be better suited for more HP and a better drag turbo.

I know someone selling one soon too.....hmmmm......

reckedracing · 08-02-2006, 10:24 AM

lmao, you're a boost addict...

Turbo&Auto · 08-02-2006, 10:28 AM

who me

Calesta · 08-03-2006, 12:47 AM

Yup, that 20g would be nice. You want to spend as much time in the best efficiency island as possible. I'm still going to use the 14b on mine even though I'll be all over the map. At least it will be cheap and spool almost instantly. I won't have much power up top, but at least I'll be able to maintain at least a power curve that tapers off to flat past 5000rpm. It will be a very full torque curve.

hondatur62d16 · 09-07-2006, 08:45 AM

then what is the sence of a turbo upgrade if it just switches your boost RPM s and dont give you more H/P does nt make sence to me bigger turbo more air more H/P right or wrong on any motor bigger turbo more H/P not saying how long it will last like that but

Cashizslick · 09-07-2006, 09:19 AM

Well, at least most of us have car's where there are a few 'no brainer' turbos on the market to choose from.

Just wait till i get a GT2871R and some 550cc injectors . . .

Turbo&Auto · 09-07-2006, 01:06 PM

Thats what I WAS going to use on my Matrix, good choice in turbos. There's a guy on MatrixOwners that's using a GT2876R, 4" inlet. WAY too big

Cashizslick · 09-07-2006, 01:27 PM

Too big for a Matrix . . .

Turbo&Auto · 09-07-2006, 04:41 PM

The 4" inlet I meant, the position of teh turbo on our cars is behind the motor. There was just enough room for a 3" intake pipe on mine and even that was tighter then I would've liked. I'll be impressed if this guy can get that turbo in there nicely.

Cashizslick · 09-07-2006, 05:53 PM

Quote:

Originally Posted by Turbo&Auto

The 4" inlet I meant, the position of teh turbo on our cars is behind the motor. There was just enough room for a 3" intake pipe on mine and even that was tighter then I would've liked. I'll be impressed if this guy can get that turbo in there nicely.

Actually mine is on the side

Turbo&Auto · 09-07-2006, 09:45 PM

Ya, Nissan's are nice like that, looks HOT too

The Sube's have a reverse mount kit that makes it look similar, just the other side of the engine bay.

tloc · 09-08-2006, 01:23 AM

ok i somewhat understand how to read compressor maps but i dont understand how or Why T&A said that it would run better at 15-18 psi or why he would do better with a larger turbo, such as the b20g... 15 psi would have a pressure ratio of about 2.02 or 2... but how do u read the bottom so u know where to line up the turbos at or how do u know which one is for u... i didnt understand mikes part about reading the bottom

07-31-2006, 10:18 PM	#26
Turbo&Auto Nick Go FAST!! Join Date: Jan 2006 Location: East Burg, PA! Age: 28 Posts: 3,271 iTrader: 3 / 100% Ride: 09 Cobalt SS/TC Rep Power: 87	enlighten me then __________________ www.BackyardTurbo.com

07-31-2006, 11:20 PM	#27
Calesta Admin with a big stick Join Date: Sep 2002 Location: Dallas / Fort Worth, TX Age: 32 Posts: 24,525 iTrader: 0 / 0% Ride: 2003 S2000 Rep Power: 291	It's going to take about an hour of typing... __________________ DO NOT PM me with tech questions! Use the forums! Intercrew Auto Salon - (972) 485-8688

08-01-2006, 12:47 AM	#29
Calesta Admin with a big stick Join Date: Sep 2002 Location: Dallas / Fort Worth, TX Age: 32 Posts: 24,525 iTrader: 0 / 0% Ride: 2003 S2000 Rep Power: 291	I do. __________________ DO NOT PM me with tech questions! Use the forums! Intercrew Auto Salon - (972) 485-8688

08-01-2006, 04:55 AM	#30
Calesta Admin with a big stick Join Date: Sep 2002 Location: Dallas / Fort Worth, TX Age: 32 Posts: 24,525 iTrader: 0 / 0% Ride: 2003 S2000 Rep Power: 291	Ooooooooooooook. This is why you're both right and wrong, and both totally missing the point. 1. LHO is correct in saying that psi is psi no matter what turbo it comes from. Pressure is pressure. It is measured at the intake manifold, so if your boost gauge shows 4psi, you have 4psi. It's that simple. He is also correct in saying that the bigger turbo just applies that 4psi later in the rev range of the engine. 2. He is NOT correct in saying that the bigger turbo will make the same amount of power at the same pressure level as the smaller turbo- not unless both are pushing the same pressure at the same engine RPM, and at the same efficiency. 3. LHO's post about volume vs flow rate vs fixed volume of the intake manifold is correct. Pressure is pressure. 5psi on a manifold is going to flow the same amount at the same engine RPM no matter what turbo is pushing it. 4. T&A is correct in saying that 300cfm will make more power than 200cfm provided you have the fuel to use it- but only partially correct. 5. LHO's comeback saying that 10psi will make 250whp (arbitrary example) no matter which turbo its from is incorrect. He's leaving something out. 6. T&A's last comeback talking about different compressor maps is starting to show some understanding about the whole debate.... but doesn't lay it all out there. Alrighty T&A (and LHO), let's all go to school. ----- I know a lot of you know a lot of this stuff already, but just sit tight. ----- Engines are big energy converters / reactors. They convert the latent energy contained in fuel to thermal energy that pushes pistons/rotors around, which act on lever arms (rods, crankshaft) to create torque. Power is a function of that torque applied over time. The faster you apply the torque (higher rpm), the more power you get- even if you have the same amount of torque. Higher amounts of fuel and air mean more energy is released in the reaction (combustion), so you get more torque and therefore more power. Now air on its own isn't the important part. Oxygen is- that's what reacts with the fuel to make a nice boom and push your pistons around. Density is the key. With turbochargers, when you look at a compressor map, you see all those wonderful efficiency islands. Higher efficiency values mean higher air densities- and therefore higher oxygen densities. Take an imaginary box. When it's full, this imaginary box holds one pound of air. Now let's squish that air to half its size- the equivalent of 14.7psi (1 atm) of boost. Squish more air the same amount and fill the box to the top. At 100% efficiency (not possible, but imagine), you'll have exactly two pounds of air in the box. Twice the air means twice the potential to burn more fuel, right? With 2 pounds of air in the box (or engine) that's designed to hold only 1 pound, you have the opportunity to burn twice as much fuel and make twice as much torque. Let's say your turbo is only operating at 80% efficiency. At 1atm (14.7psi) of boost, you'll spend 20% of your turbo's work generating heat, and only 80% of the work will go to compressing air. The air heats up, and you have only 1.6 pounds that are usable to potentially burn fuel, not 2 pounds like you had before. The box is still full to the top. You have the same pressure, the same volume (so the same FLOW), but less oxygen available to burn fuel. All of this assumes you have a box with no hole in it. Your engine is this box with a hole in it. Well, I guess your intake manifold is, but you get the idea. The faster your engine is turning, the bigger the hole gets. This is where flow rate comes into play. The faster your engine runs, the more flow the turbo has to provide to establish the same pressure ratio. That's why small turbos run out up top- because they can't move enough air to maintain pressure against the engine once the engine is gobbling up more air. Addressing points: 1. Yes, pressure is pressure- but assuming everything else is the same. LHO has to assume that both setups have engines of the exact same displacement running at the same speed. With a 2 liter engine running at a constant 4000rpm, a turbo pushing 4psi against it is always pushing the same volume of air, no matter what the turbo size. Pressure is pressure. 2. On the bigger turbo making the same amount of power but just at a different RPM, that makes no sense. LHO is already stating that the larger turbo will make boost at a higher engine speed than the smaller turbo, and that's correct. Everyone knows that. Assuming the same efficiency, a small turbo pushing 10psi at 5000rpm will make half as much power as a turbo pushing 10psi at 10000rpm. Both engine setups are making the same amount of torque- they're both burning the same amount of fuel per engine revolution- but since the 10000rpm engine is applying that force twice as fast as the 5000rpm engine, it makes twice as much power. Easy. So... if the larger turbo is making the same pressure as the smaller turbo but does it higher up in the rev range of the engine, then it will make more power at the same pressure level, not the same amount of power. That's just a function of engine speed. I'm sure homie LHO would come back with something like "oh, the small turbo can make 10psi in the same place that the big turbo can," and he might be right- but then this is where all the efficiency fun comes into play. The small turbo might be able to push 10psi at 10k just like the bigger turbo, but it won't do it as efficiently as the larger turbo. Even at the same flow rate and the same pressure, the larger turbo will flow more MASS into the engine because it is operating more efficiently. The small turbo is just generating heat because it's out of range, while the larger turbo is working pushing more air. Same pressure, same CFMs, different mass flow rate, different power outputs. 3. See #1. 5psi is 5psi, assuming the engine is consuming air at the same speed in both cases (box with hole in it). You have a constant cross section for air to flow across, you have the same pressure differential, and you have the same amount of air going out. Everything is identical. 4. Yes, more flow = more power... generally. When you're reading the compressor maps for a turbocharger, they're mapped with pressure ratio vs flow rate. Just because a turbo can flow a certain amount of air volume doesn't mean that it can succesfully push that volume into an engine at a certain pressure. You could theoretically have a turbo that could push 500cfm, but only be capable of pushing it at 1psi. Any more resistance, and you don't get that flow rate. The turbo must have both the capability to flow the volume AND be able to maintain pressure to push it into an engine. Also, talking about flow on its own without reference to the density of that flow is misleading. Flow on its own doesn't tell you anything. You can flow the same volume of light sugar water and thick molasses- and they will be the same flow rate- but you get totally different amounts of sweetness, right? I generally think that people who just talk "oh but this one FLOWS more CFMs" without mentioning efficiencies or air densities doesn't fully understand what they're talking about. 5. See efficiency. 6. Yay T&A! Talking about compressor maps... but it's not just the volume vs pressure that are important- the efficiency islands are the most important part of the compressor map. ----- So basically- T&A is a lot more right than LHO, but LHO is technically right in most of his stuff. He just doesn't have the whole picture. I hope that clears things for some people and doesn't muddy the waters for too many.... __________________ DO NOT PM me with tech questions! Use the forums! Intercrew Auto Salon - (972) 485-8688

08-01-2006, 07:44 AM	#31
Turbo&Auto Nick Go FAST!! Join Date: Jan 2006 Location: East Burg, PA! Age: 28 Posts: 3,271 iTrader: 3 / 100% Ride: 09 Cobalt SS/TC Rep Power: 87	Thanks for the writeup, I need to read it a couple more times to fully soak it all in. Some of it I do know, but a lot is new and good info I realize about efficiency and somewhat how to read a compressor map, still learning that aspect of turbocharging. I couldnt get to that point with this guy though, he didnt want to hear anything but 4psi is 4psi and you cant make anymore power at the same psi no matter the turbo. I got a bit derailed and skirted some of the more important issues. We were also assuming them to be on the same motor within the same kind of group of turbos too. Like T25's, GT28's. The guy Wish that I was talking about has a Matrix like mine and originally had a T25 on it, he swapped out to a Big16G equivelant turbo and pickeed up a lot of power without anymore boost. He couldnt understand how that was possible and I was just lacking all the terminology to get it across properly. Thanks for the info, you rly can never learn too much about turbos. If you have any other sites that you could point me to for reading info I would appreciate it. I google the shit, but you get a mixed bag of peoples opinions and whats actually real. __________________ www.BackyardTurbo.com


Welcome, Guest! Please Register or Login: User Name Password Members have access to more features, better search, and see fewer ads! It's free, what are you waiting for?

08-01-2006, 09:05 AM	#33
Turbo&Auto Nick Go FAST!! Join Date: Jan 2006 Location: East Burg, PA! Age: 28 Posts: 3,271 iTrader: 3 / 100% Ride: 09 Cobalt SS/TC Rep Power: 87	I've read it a few times now, its starting to sink in more and more and make more sense too. I think I'm starting to see the whole picture instead of a narrow view of what doesnt matter as much. I'm still hazy on compressor maps though. Every place I read trying to figure out how to read a compressor map misses all kinds of important factors. Do you have a site that clearly can explain how to read a compressor map? __________________ www.BackyardTurbo.com

08-02-2006, 09:51 AM	#37
reckedracing TTIWWOP Join Date: Dec 2002 Location: 845 Area, NY Age: 29 Posts: 15,381 iTrader: 0 / 0% Ride: 90 z6-t hatch, 94 Bagged S10, 91 Lifted Mazda Rep Power: 411	nice write ups guys, excellent info now if i could just find a map for my IHI turbo lol __________________ I'll blow a hole in your face then go inside and sleep like a baby.

08-02-2006, 10:07 AM	#38
Turbo&Auto Nick Go FAST!! Join Date: Jan 2006 Location: East Burg, PA! Age: 28 Posts: 3,271 iTrader: 3 / 100% Ride: 09 Cobalt SS/TC Rep Power: 87	Thanks for the rundown. What was puzzeling me when I looked at maps was the fact that you need to add atmospheric pressure to the equation. I would convert 10psi to the equivelent used on the chart and it wouldnt even be on the map. Then yesterday I added 14.7 to the amount of boost I planned on running and things started to make a LOT more sense. Thanks again for the writeups guys, I rly love to read about turbos and how everything works. I seem to learn at least 2 things everytime I sit down and read more and more. Edit: After looking at that 14b map, I'm glad I went with a larger turbo. It would've choked out early. The Big16G I'm using will make good power without a lot of heat around 10-12 and then be much more efficient in the area I want to track the car at, 15-17psi. BUT, it does look like I could've still went larger. __________________ www.BackyardTurbo.com Last edited by Turbo&Auto; 08-02-2006 at 10:18 AM.

08-02-2006, 10:19 AM	#39
Turbo&Auto Nick Go FAST!! Join Date: Jan 2006 Location: East Burg, PA! Age: 28 Posts: 3,271 iTrader: 3 / 100% Ride: 09 Cobalt SS/TC Rep Power: 87	This 20G might be better suited for more HP and a better drag turbo. I know someone selling one soon too.....hmmmm...... __________________ www.BackyardTurbo.com

08-02-2006, 10:24 AM	#40
reckedracing TTIWWOP Join Date: Dec 2002 Location: 845 Area, NY Age: 29 Posts: 15,381 iTrader: 0 / 0% Ride: 90 z6-t hatch, 94 Bagged S10, 91 Lifted Mazda Rep Power: 411	lmao, you're a boost addict... __________________ I'll blow a hole in your face then go inside and sleep like a baby.

08-02-2006, 10:28 AM	#41
Turbo&Auto Nick Go FAST!! Join Date: Jan 2006 Location: East Burg, PA! Age: 28 Posts: 3,271 iTrader: 3 / 100% Ride: 09 Cobalt SS/TC Rep Power: 87	who me __________________ www.BackyardTurbo.com

08-03-2006, 12:47 AM	#42
Calesta Admin with a big stick Join Date: Sep 2002 Location: Dallas / Fort Worth, TX Age: 32 Posts: 24,525 iTrader: 0 / 0% Ride: 2003 S2000 Rep Power: 291	Yup, that 20g would be nice. You want to spend as much time in the best efficiency island as possible. I'm still going to use the 14b on mine even though I'll be all over the map. At least it will be cheap and spool almost instantly. I won't have much power up top, but at least I'll be able to maintain at least a power curve that tapers off to flat past 5000rpm. It will be a very full torque curve. __________________ DO NOT PM me with tech questions! Use the forums! Intercrew Auto Salon - (972) 485-8688

09-07-2006, 08:45 AM	#43
hondatur62d16 Chris D16 turbo Join Date: Sep 2006 Location: Bufflako,N.Y Age: 28 Posts: 29 iTrader: 0 / 0% Ride: Honda Civic 94 EX Rep Power: 7	then what is the sence of a turbo upgrade if it just switches your boost RPM s and dont give you more H/P does nt make sence to me bigger turbo more air more H/P right or wrong on any motor bigger turbo more H/P not saying how long it will last like that but

09-07-2006, 01:06 PM	#45
Turbo&Auto Nick Go FAST!! Join Date: Jan 2006 Location: East Burg, PA! Age: 28 Posts: 3,271 iTrader: 3 / 100% Ride: 09 Cobalt SS/TC Rep Power: 87	Thats what I WAS going to use on my Matrix, good choice in turbos. There's a guy on MatrixOwners that's using a GT2876R, 4" inlet. WAY too big __________________ www.BackyardTurbo.com

09-07-2006, 04:41 PM	#47
Turbo&Auto Nick Go FAST!! Join Date: Jan 2006 Location: East Burg, PA! Age: 28 Posts: 3,271 iTrader: 3 / 100% Ride: 09 Cobalt SS/TC Rep Power: 87	The 4" inlet I meant, the position of teh turbo on our cars is behind the motor. There was just enough room for a 3" intake pipe on mine and even that was tighter then I would've liked. I'll be impressed if this guy can get that turbo in there nicely. __________________ www.BackyardTurbo.com

09-07-2006, 09:45 PM	#49
Turbo&Auto Nick Go FAST!! Join Date: Jan 2006 Location: East Burg, PA! Age: 28 Posts: 3,271 iTrader: 3 / 100% Ride: 09 Cobalt SS/TC Rep Power: 87	Ya, Nissan's are nice like that, looks HOT too The Sube's have a reverse mount kit that makes it look similar, just the other side of the engine bay. __________________ www.BackyardTurbo.com

09-08-2006, 01:23 AM	#50
tloc Junior Member Join Date: Aug 2006 Posts: 21 iTrader: 0 / 0% Rep Power: 7	ok i somewhat understand how to read compressor maps but i dont understand how or Why T&A said that it would run better at 15-18 psi or why he would do better with a larger turbo, such as the b20g... 15 psi would have a pressure ratio of about 2.02 or 2... but how do u read the bottom so u know where to line up the turbos at or how do u know which one is for u... i didnt understand mikes part about reading the bottom

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Safe boost level and what times to expect?	RyanA	Engine Building	0	04-24-2004 08:44 AM
Static vs. Effective Compression	pissedoffsol	Turbo Information	0	01-12-2004 01:43 AM
Digging up Turbo Vs Superchargers	Silverchild79	Forced Induction	36	01-03-2004 11:58 PM
if you weren't in chat tonight....	pissedoffsol	Members' Lounge	33	10-16-2003 12:30 AM
Is there a Supercharger kit	chap_e77	Forced Induction	3	08-26-2003 07:09 PM

Hondaswap.com | Honda Technical & JDM styling Forums

Boost & HP Level