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Discussion Starter · #1 ·
It is interesting reading the different theories on header length and size for a turbo application on the YXZ.
Have the shorty header guys actually tested the stock header vs the shorty?
We have tried many different headers on Yamaha triples and know what works. We have also tested many different header pipes on the R1 motor with a turbo and have found the same results.
It is shocking how important primary header tube length and size is.
The fast spool theory also may be more myth than people think.
It's interesting to read the different theories though.
 

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I guess you don't understand what I am saying. I was agreeing with the op in that there is a lot to exhaust, turbo or not. It is along the same lines as finding the right carb for an application. It is very possible (and quite often done) to put too large of a carb on an engine. Yes the big carb flows more but with the proper size carb you maximize air velocity and therefore horsepower. Same thing with exhaust. Too big of an exhaust pipe and you lose velocity. Yes it flows more but velocity is more important for hp than just flow.
A turbo header with properly designed runners (length, diameter, etc.) Will work much better than a super short stubby header. When you are comparing 6" runner length to say 12" or 18" there is not going to be a noticeable lag difference. Comparing 6" runners to a muffler mounted turbo with 8-10 feet of pipe there is a major difference.
So yes, I will be much happier/faster with air velocity and you can have straight airflow.
 

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I guess you don't understand what I am saying. I was agreeing with the op in that there is a lot to exhaust, turbo or not. It is along the same lines as finding the right carb for an application. It is very possible (and quite often done) to put too large of a carb on an engine. Yes the big carb flows more but with the proper size carb you maximize air velocity and therefore horsepower. Same thing with exhaust. Too big of an exhaust pipe and you lose velocity. Yes it flows more but velocity is more important for hp than just flow.
A turbo header with properly designed runners (length, diameter, etc.) Will work much better than a super short stubby header. When you are comparing 6" runner length to say 12" or 18" there is not going to be a noticeable lag difference. Comparing 6" runners to a muffler mounted turbo with 8-10 feet of pipe there is a major difference.
So yes, I will be much happier/faster with air velocity and you can have straight airflow.
I guess you do not understand what airflow means. Go blow through a straw, lots of velocity, not much flow. Flow measures the volume of air going through, the velocity of that air does not matter. The more CFM processed the better. If I am processing more airflow at half the velocity I am still moving more air. In your example of the carb it is because the engine is not able to make use of the flow due to some other restriction downstream such as the intake or the head or valves or exhaust. The turbine is the only restriction involved, we want as much pressure hitting it as possible.
 

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The more air velocity you have in the exhaust, the more pressure hits the turbine. By your logic, 3" diameter runners would work much better than 1.5" diameter runners on a turbo manifold. These engines don't move enough air to use 3" diameter runners and there would be too much "flow". It is about PROPER sizing not just the biggest thing that we can fit.

Google "velocity stack" and look at the pictures. Why would someone add this to their carb (in essence reducing flow)? The answer is horsepower :)
 

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I guess you do not understand what airflow means. Go blow through a straw, lots of velocity, not much flow. Flow measures the volume of air going through, the velocity of that air does not matter. The more CFM processed the better. If I am processing more airflow at half the velocity I am still moving more air. In your example of the carb it is because the engine is not able to make use of the flow due to some other restriction downstream such as the intake or the head or valves or exhaust. The turbine is the only restriction involved, we want as much pressure hitting it as possible.
the part about the carb is with the proper volicity, then you get atomazation and if voilcity is to slow and carb too big then fuel drops out of air stream cause air is flowing too slow, but the big carb can flow more cfm but its useless if the fuel drops out of the air .so volicity and cfm are both important but with a turbo the shortest runners helps keep lag to a minimum and performance to a maximum .
 

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Nonsense. The turbine is the flow limiter. It determines pressure. Pressure is nothing more than resistance to flow. Why do think wastegates exist? Too much pressure (resistance to FLOW) causes power to decrease.

Velocity stacks were originally designed to prevent fuel air expulsion from the carburetor. These days they are always built to smooth the air as it enters the throttle area to increase. . . wait for it . . . . . FLOW.
 

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Discussion Starter · #11 ·
There are some interesting views. Did someone say the speed of the exhaust flow over a certain area determines the acceleration of the turbine? The engine produces the same amount of exhaust no matter the header.
Keep in mind all the cylinders fire at different times. Primary tube length is critical in this application.
Just because a turbo is now on the motor, it does not change how important the header design is. How much did Yamaha leave on the table with header pipe only?
How would a shorty do on a Dyno without the turbo?
 

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Yamaha probably left 10 horses on the table with the header, the pipes are too small. But that is not the real issue here, because when you add the turbo you are no longer looking at using the header to possibly scavenge exhaust gasses to possibly increase flow. Instead of using primary diameter and length to control the expansion and retain energy of the exhaust gasses as they cool and exit the exhaust the job of the header becomes to reduce restriction to deliver as much energy to the turbine as possible at the lowest possible drive pressure. The longer the distance to the turbine the more heat (energy) lost and the more drive pressure (energy) lost. We can always dump the excess via wastegate but we still want as much of it arriving to do work on the turbine as we can get and THEN we can decide what to do with any excess.
 

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Discussion Starter · #13 ·
Why does a turbocharged F1 car use long tube primary's and not a more compact and lighter short tube header?
 

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Or maybe all the stock header turbo shops could actually post before and after Dyno graphs with their turbo kit installed instead of the "guesstimate" or "projected" numbers. Proof is in the pudding. Seems like every time a new turbo kit is released it has a higher HP number then the last kit yet no proof to back it up.
 

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Why does a turbocharged F1 car use long tube primary's and not a more compact and lighter short tube header?
I would expect this to be more due to the fact that these cars are engineered for a more limited window of operation and concerns for daily driving performance would not phase them. F1 cars also were not known for the outstanding spool of the turbochargers. And as the RPM range that the car operates in for the majority of a race is for a lack of technical term "screaming" Even with use of an inconel alloy turbine wheel, the EGT's and back-pressure on a short runner would be insane.

Also in F1, there is much more to consider designing the system than HP, Even positioning the turbochargers lower,higher, further outwards, closer inwards, could affect lap times due to weight balance and distribution. Perhaps a 1000RPM faster spool doesn't overcome the advantages of specific positioning of the turbochargers. lower COG etc.

Much of the design also depends on the use, much like the type of SXS a person should own depending on the terrain they plan on traveling. Sure a big GT47 could be called the best turbocharger for a supra because it makes tremendous power, however if your plans are to autocross, that would be completely useless.

In some scenarios turbo lag can be your friend, having a more gradual onset of HP is much friendlier to the drivetrain.
 

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Nonsense. The turbine is the flow limiter. It determines pressure. Pressure is nothing more than resistance to flow. Why do think wastegates exist? Too much pressure (resistance to FLOW) causes power to decrease.

Velocity stacks were originally designed to prevent fuel air expulsion from the carburetor. These days they are always built to smooth the air as it enters the throttle area to increase. . . wait for it . . . . . FLOW.
A waste gate is there to regulate the boost. Without a waste gate you would not be able to set a desired boost level and/or keep the turbo in its efficiency range. Once the desired boost is hit, the waste gate opens to bleed off any excess exhaust in order to control the boost levels.
You act like I am saying flow isn't important. Have you ever seen an intake with variable length runners? Yes this is still used in racing today.
Check out the picrure. The intake runners extend out for lower rpm (to increase velocity) and shorten up as the engine gets to higher rpm. If you went to a larger intake runner all together then it would make less horsepower because air velocity is lost. The same length/size runner does not work optimally at all rpm ranges.
An engine moves a set amount of air and the goal is to maximize the velocity of the air being used. It is about proper sizing not just the biggest thing that we can make fit.
 

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We will never get to the same page Blan because velocity does not equal flow and you cannot seem to understand that. Yes, you pursue velocity . . . in an effort to achieve maximum flow. If velocity were all that mattered then you would place a tiny venturi in the way and get all sorts of velocity . . . .. unfortunately flow would be nothing and it would be the restriction to flow and power would also be nothing.

BUT when you are talking velocity as you are in an intake tract you are talking about a vacuum environment, where attempts are made to take advantage of the energy of a moving column of air to achieve maximum flow. In a header leading to a turbine we are talking about a pure pressure environment, the objectives then change into preventing pumping losses and retaining heat energy so that we can apply it to drive the turbine.

Going on and on about tuning an intake tract for velocity when we are discussing manifold piping to a turbine is like talking about what size torque wrench to use to paint your house. It is not relevant because the task has changed. Similarly a header designed for a naturally aspirated engine has certain properties that engineers pursue, one of which is maintaining velocity etc etc in order to provide as much scavenging effect as possible . . . but once a turbo is introduced all that becomes moot.
 

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Ever notice what happens to all those sweet tuned intake setups you keep talking about once turbos or superchargers are added? Away they go in favor setups designed to reduce pumping losses. Its the shift from a vacuum system to a pressure system that dictates the change, same as what happens on the exhaust side where we change to driving a turbo instead of attempting to retain heat energy to scavenge.
 

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I understand velocity does not equal flow. The purpose of all of it is to move as much air as possible. What I am saying is that for the set amount of air that the engine moves, it is important to maintain as much velocity as possible without restricting flow. I was merely talking about the intake tract as an example of velocity compared to just flow. Flow by itself is crap without velocity. Otherwise all of our exhaust systems would just be the largest tubing we can fit.
I understand exactly what you are saying. Yes flow is extremely important but the goal is to get as much velocity with that flow as possible.
The problem with shorty headers is that air likes to move straight, not turn at sharp angles. A little length on the runners allows a more gradual direction change. If this was a 2 cylinder, then super short STRAIGHT runners to each side of a divided turbo would be ideal. This is a 3 cylinder so the runners have to turn. A super short almost log style manifold would not work as well as one with a little more runner length to smooth out the direction changes.
 
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