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savedbygrace
Well-known member
Post your opinions and/or theories of operation proudly below.
Experience may be helpful…
Junior
Experience may be helpful…
Junior
Short Charge Tube Good or Bad?
- Thread starter savedbygrace
- Start date
Shorter would be better . In theory less volume to pressurize for the turbo to spool faster. But somtimes you have to do what works and a longer one must be used.
I believe that Junior is posting this in light of the recent Polaris Twisted kit that is in the Prototype stage of development.
Lets leave this open for a constructive discussion and not a "Pissin match" that has people defending their favorite turbo builders... that is the part of this forum that I HATE.... much better to have constructive discussions that discuss the plus's and minus's of an given topic.
Here is my opinion for what it is worth.
There is a difference between a fast spooling turbo and an intake tract that is quick to build pressure.
In my experience... Two stroke...a short charge tube has no "air reservoir" to draw from before the manifold pressure goes positive. IMO this greatly affects the way the engine responds in low RPM situations.
This seems to be a delicate balance... I've seen non intercooled turbos with lag and correcly sized intercooled systems that have relatively no lag. Large turbo, large intercooler "race" systems that are built for maximum power seem to have the most lag....lots of intake to pressurize when the turbo starts to spool.
Also, In rapid cycling of open/closed/open throttle situations (ie boondocking)... Compressor chatter would need to be wholey managed by a blow off valve (BOV). In these situations, I've come to learn on the sleds, there is no "buffer" or "accumulator" with a tiny charge tube/box.
With a BOV, there seems to be an effect on throttle response in the rapid on/off cycling of the trottle... when it is blowing off ... the airbox seems to lose that immediate available pressure.
Now, if the short charge tube feeds into a larger volume airbox... these effects might be negated.
All this "theory" can go out the window as I have been very supprised by turbos that should not work very well on paper but perform well in real life use.
Lets leave this open for a constructive discussion and not a "Pissin match" that has people defending their favorite turbo builders... that is the part of this forum that I HATE.... much better to have constructive discussions that discuss the plus's and minus's of an given topic.
Here is my opinion for what it is worth.
There is a difference between a fast spooling turbo and an intake tract that is quick to build pressure.
In my experience... Two stroke...a short charge tube has no "air reservoir" to draw from before the manifold pressure goes positive. IMO this greatly affects the way the engine responds in low RPM situations.
This seems to be a delicate balance... I've seen non intercooled turbos with lag and correcly sized intercooled systems that have relatively no lag. Large turbo, large intercooler "race" systems that are built for maximum power seem to have the most lag....lots of intake to pressurize when the turbo starts to spool.
Also, In rapid cycling of open/closed/open throttle situations (ie boondocking)... Compressor chatter would need to be wholey managed by a blow off valve (BOV). In these situations, I've come to learn on the sleds, there is no "buffer" or "accumulator" with a tiny charge tube/box.
With a BOV, there seems to be an effect on throttle response in the rapid on/off cycling of the trottle... when it is blowing off ... the airbox seems to lose that immediate available pressure.
Now, if the short charge tube feeds into a larger volume airbox... these effects might be negated.
All this "theory" can go out the window as I have been very supprised by turbos that should not work very well on paper but perform well in real life use.
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POLARIS600cc
Member
You stated in the other thread that you DID have experience with a short charge tube. Well lets hear it.
J
JSCC
Well-known member
Well it depends on what you are building. There really is no one size fits all for every kind of riding.
But for me, I want a "cooled" intake track, with as short of a charge tube I can get......
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Snowstar
Well-known member
My own experience with my IQR1000 turbo (M1000 motor) is that the shorter charge tube increased throttle response and overall ridability of the sled. My charge tube is about half as long as the standard TTM1000 charge tube. The new Twisted Polaris that I rode yesterday had even better response than my sled. No sales gimics here just honest experience.
This is a sincere question... so don't take it the wrong way Snowstar... I am always intersted in innovation... and open to learn more as these turbos evolve.
How much transistional-throttle full-load work were you able to get in your testing on the the TT-D8? Were you able to spool it up, snap the trottle closed and get back into it multiple times in the same pass?
Can't wait to hear how it works on the snow.
How much transistional-throttle full-load work were you able to get in your testing on the the TT-D8? Were you able to spool it up, snap the trottle closed and get back into it multiple times in the same pass?
Can't wait to hear how it works on the snow.
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The shortest distance from A to B is always best.... Also the straightest path would be beneficial as well...With that said some of you savey turbo guy's need to build a turbo that mounts directly behind & horzontal to the carb rack. This could be made possible by 1st designing a smaller gas tank to allow for the room to make the install possible. The cold air intake would externally be mounted just infront of the riser bar for optimum air intake and the exhaust would dump out under the tunnel and would require a deflector for those deep powder days.
OT
OT
for those who question ?
Why would a short tube be better or worse ?
why would a longer tube be better or worse?
why would no plenum be better or worse?
please answer from a field use perspective, flow benchs and modeling programs mean little in this application.
I like to see outside the box thought,, sometimes its wayyyyyy outside..even for me..
Gus
Why would a short tube be better or worse ?
why would a longer tube be better or worse?
why would no plenum be better or worse?
please answer from a field use perspective, flow benchs and modeling programs mean little in this application.
I like to see outside the box thought,, sometimes its wayyyyyy outside..even for me..
Gus
if you have a super short system you have to have a VERY good blow off valve to as snapping the throttle closed will make that short little intake tract see huge pressure really quickly, and major compressor surge.
mountainhorse, i think you ment blow of valve not wastegate? as wastegate is just for getting rid of extra exhaust to limit boost levels. a LARGE high quality blow off valve so the turbo can keep a decent spool level when you chop the throttle, this way, it can keep spining(obviously slowing due to less load) but not be hammered to a stop by a sudden increase boost pressure from nowhere for LOTS of air to flow. if you have a well setup BOV on a super short system, it has no reason NOT to work great.
exhaust setup design definately also hage a major impact on spooling, but we shall keek to the intake tract for now.
the turbo is nothing more then an exhaust powered air compressor, so say on the identical sled with identical clutch/track/gearing everything, the motor should rev under no load identicaly, its the same motor, so the turbo's exhaust side spins up equally as fast(were still in theory land, but it should be close) so if the turbo is spinning at the same speed in each of the sleds, but one has to fill a 2' 2.5" tube and the other has to fill a 6" 2.5" tube, obviously the shorter one will spool faster, and as more boost sees the motor quicker, more exhaust gas is produced, and more spooling.
poor shaping of an intake setup no matter how short definately can be a negative affect, as air still likes the path of least resitance so if its poorly shaped, well, now we are getting into fluid dynamics, and i dont think THAT much thought goes into all of this, but maybe im wrong, just more common sense type stuf for airflow.
last but not least plenum in my mind allows for boost to reach each of the cylinders equally, as you have a sort of resiviour of pressure with a slight excess so each cylinder gets an equal amount(0r as close as possible) if you had a charge tube that just split with say a Y and then went directly into each of the cylinders you would have to design if VERY well, or you would run a high risk of one side of the Y being more efficient and sending LOTS more air into one side, heck, even a 1psi difference, but your fueling is setup equally, so you would be looking at risk there. and uneven load on a twin seems like a BAD type of situation for me.
again, this is ALL theory, so correcty anything if its obviously wrong, just seems pretty practical type stuff.
mountainhorse, i think you ment blow of valve not wastegate? as wastegate is just for getting rid of extra exhaust to limit boost levels. a LARGE high quality blow off valve so the turbo can keep a decent spool level when you chop the throttle, this way, it can keep spining(obviously slowing due to less load) but not be hammered to a stop by a sudden increase boost pressure from nowhere for LOTS of air to flow. if you have a well setup BOV on a super short system, it has no reason NOT to work great.
exhaust setup design definately also hage a major impact on spooling, but we shall keek to the intake tract for now.
the turbo is nothing more then an exhaust powered air compressor, so say on the identical sled with identical clutch/track/gearing everything, the motor should rev under no load identicaly, its the same motor, so the turbo's exhaust side spins up equally as fast(were still in theory land, but it should be close) so if the turbo is spinning at the same speed in each of the sleds, but one has to fill a 2' 2.5" tube and the other has to fill a 6" 2.5" tube, obviously the shorter one will spool faster, and as more boost sees the motor quicker, more exhaust gas is produced, and more spooling.
poor shaping of an intake setup no matter how short definately can be a negative affect, as air still likes the path of least resitance so if its poorly shaped, well, now we are getting into fluid dynamics, and i dont think THAT much thought goes into all of this, but maybe im wrong, just more common sense type stuf for airflow.
last but not least plenum in my mind allows for boost to reach each of the cylinders equally, as you have a sort of resiviour of pressure with a slight excess so each cylinder gets an equal amount(0r as close as possible) if you had a charge tube that just split with say a Y and then went directly into each of the cylinders you would have to design if VERY well, or you would run a high risk of one side of the Y being more efficient and sending LOTS more air into one side, heck, even a 1psi difference, but your fueling is setup equally, so you would be looking at risk there. and uneven load on a twin seems like a BAD type of situation for me.
again, this is ALL theory, so correcty anything if its obviously wrong, just seems pretty practical type stuff.
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Snowstar
Well-known member
I did do that a couple times (almost going over the bars when letting off, water and grass can really slow you down in a hurry) and responded well without loading up or hesitation. Cant wait to get it in some tight trees.
I'd say that a smaller tank is the last thing you want on a turbo regardless of throttle response. I just ordered a larger tank, got tired of always being the first one running low on fuel.
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savedbygrace
Well-known member
Thanks for the replies,
The general consensus seems to be the smaller the intake (charge tube/air box) volume between the turbo and the engine the faster the spool time. It would appear that the order of operations is disregarded, and the focus is shifted primarily to the intake or charge tube area.
Everyone knows that a turbo is powered by exhaust energy. So it would stand to reason that the volume between the engine exhaust and the turbo would be more critical in regards to spool time than the intake. But the exhaust is still not the first component in the order of operation. First the engine has to create this exhaust energy.
In order for the engine to create the exhaust energy needed to power the turbo, it first has to take air in, digest it, and finally exhaust it. If the intake air space between the engine, and the turbo is not adequate, then the engine will have to pull air through the restriction of a stagnant turbo, before creating enough exhaust energy to propel the turbo henceforth causing classic “turbo lag”.
This line of thinking completely debunks the “smaller the charge air space the better” theory.
Here is one example of real world R&D, to back this up. We mounted a turbo to an engine in such a configuration that the compressor housing mounted almost directly to the throttle body, performance was minimal. Without relocating the turbo, we then indexed (rotated) the turbo compressor housing to accommodate a charge tube that circled the entire turbo before entering the throttle body, this charge tube was approximately 20” in length, and was the only change made to the turbo configuration, throttle response, and performance was increased a hundred fold.
The next thing to consider in charge tube design would be would be charge air velocity. What effects does the size, and shape of a tube have on charge air velocity, and what effect does charge air velocity have on engine performance?
Junior
The general consensus seems to be the smaller the intake (charge tube/air box) volume between the turbo and the engine the faster the spool time. It would appear that the order of operations is disregarded, and the focus is shifted primarily to the intake or charge tube area.
Everyone knows that a turbo is powered by exhaust energy. So it would stand to reason that the volume between the engine exhaust and the turbo would be more critical in regards to spool time than the intake. But the exhaust is still not the first component in the order of operation. First the engine has to create this exhaust energy.
In order for the engine to create the exhaust energy needed to power the turbo, it first has to take air in, digest it, and finally exhaust it. If the intake air space between the engine, and the turbo is not adequate, then the engine will have to pull air through the restriction of a stagnant turbo, before creating enough exhaust energy to propel the turbo henceforth causing classic “turbo lag”.
This line of thinking completely debunks the “smaller the charge air space the better” theory.
Here is one example of real world R&D, to back this up. We mounted a turbo to an engine in such a configuration that the compressor housing mounted almost directly to the throttle body, performance was minimal. Without relocating the turbo, we then indexed (rotated) the turbo compressor housing to accommodate a charge tube that circled the entire turbo before entering the throttle body, this charge tube was approximately 20” in length, and was the only change made to the turbo configuration, throttle response, and performance was increased a hundred fold.
The next thing to consider in charge tube design would be would be charge air velocity. What effects does the size, and shape of a tube have on charge air velocity, and what effect does charge air velocity have on engine performance?
Junior
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savedbygrace
Well-known member
Thanks JSCC,
Interesting… I’d like to see that….
I think the expansion chamber on a two stroke is as vital a functioning part of the engine, as an exhaust valve or cam shaft is to a four stroke engine. So I can’t see an advantage to eliminating it completely.
But I think you have the right idea.
Interesting… I’d like to see that….
I think the expansion chamber on a two stroke is as vital a functioning part of the engine, as an exhaust valve or cam shaft is to a four stroke engine. So I can’t see an advantage to eliminating it completely.
But I think you have the right idea.
Ok now how about the length of the exhaust tubing on the twisted kit? More volume to pressurize before the turbo will spool would this work against the throttle response?
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SNOW JW
Well-known member
I too would like to know more as to the effects of the lengthening of the stinger pipe from the expansion chamber on the pipe like seen in the Twisted Kit I have talked to many very well known pipe builders about this in the past and have gotten allot of feedback your thoughts on this Jr.???
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POLARIS600cc
Member
Did you guys have any other sleds there when you were testing? I think your seat of the pants test could be very misleading if you only had that ONE sled to ride. Especially when your all excited about being done with a new kit. No offense intended here, just curious.
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RKT
Well-known member
savedbygrace...
Great post... Very relevant IMO.. Like you stated.. the order of operations is often over-looked.. If you get focused on 1 single area, sometimes you forget about the actual "process" of the entire system.. When I worked in the Electronic Engineering Field.. We called this "Systems Engineering" which dealt with the system as a whole vs. single components.
ANY internal combustion engine's(2 stroke or 4 stroke) power is directly related to its air/intake.. If the air intake is not adeqaute then peak power will suffer. To make big power you need big air... This is EXACTLY the concept behind the whole turbo/supercharged operation. Force Feed it more air.. The air is STILL pulled from the open area whether it be under th ehood or outside the hood.. It can only pull what the system's design will allow..
So, we are dealing with the pressure ratio... which is ATM + Boost Pressure / ATM
BUT if you you have a restrictive intake system then the ATM in the denominator is not true ATM but the actual ATM pressure MINUS the restriction loss.. So, as the inlet becomes more restricted, the pressure ratio increases..
ANYTIME the turbo is asked to make the same amount of boost with LESS air, it MUST work much harder to acheive the desired boost level.. When the turbo works harder, more HEAT is produced as a result..
So, at this point, we have a turbo working harder, producing more heat and this equates to a less dense and hotter intake charge which will always equate to LESS power.
Just like the N/A sleds. the airbox design is critical to making power.. They are designed to add air velocity to compensate for lack of air.. This is why Pod filters usually never produce the same power as a properly designed airbox--->> the air velocity and purity is diminshed..
Then IF the intake charge tube is shorter, then there is a good possibility that the exhaust pipe is longer (more volume).. This means the exhaust pipe will have less pressure in the pipe and this is also a negative.
Now, I am not saying that the short charge tube design will always have a longer pipe nor be starving for air.. But, there does exist this possibility.. I suspect you are thinking that thelonger intake charge tube will act as an air storage compartment and better support the need for air.. I think we can assume that the air charge temp would be lower with the longer charge tube but velocity would be down as a result..
Seems like a fine balance is required between outlet pressure, inlet pressure, velocity and charge purity... Only way to really tell what is working and what is not is to built it and test it.. You got to hand it to the twisted boys.. they are trying new ideas.. and with new ideas comes new products..
Kelsey
Great post... Very relevant IMO.. Like you stated.. the order of operations is often over-looked.. If you get focused on 1 single area, sometimes you forget about the actual "process" of the entire system.. When I worked in the Electronic Engineering Field.. We called this "Systems Engineering" which dealt with the system as a whole vs. single components.
ANY internal combustion engine's(2 stroke or 4 stroke) power is directly related to its air/intake.. If the air intake is not adeqaute then peak power will suffer. To make big power you need big air... This is EXACTLY the concept behind the whole turbo/supercharged operation. Force Feed it more air.. The air is STILL pulled from the open area whether it be under th ehood or outside the hood.. It can only pull what the system's design will allow..
So, we are dealing with the pressure ratio... which is ATM + Boost Pressure / ATM
BUT if you you have a restrictive intake system then the ATM in the denominator is not true ATM but the actual ATM pressure MINUS the restriction loss.. So, as the inlet becomes more restricted, the pressure ratio increases..
ANYTIME the turbo is asked to make the same amount of boost with LESS air, it MUST work much harder to acheive the desired boost level.. When the turbo works harder, more HEAT is produced as a result..
So, at this point, we have a turbo working harder, producing more heat and this equates to a less dense and hotter intake charge which will always equate to LESS power.
Just like the N/A sleds. the airbox design is critical to making power.. They are designed to add air velocity to compensate for lack of air.. This is why Pod filters usually never produce the same power as a properly designed airbox--->> the air velocity and purity is diminshed..
Then IF the intake charge tube is shorter, then there is a good possibility that the exhaust pipe is longer (more volume).. This means the exhaust pipe will have less pressure in the pipe and this is also a negative.
Now, I am not saying that the short charge tube design will always have a longer pipe nor be starving for air.. But, there does exist this possibility.. I suspect you are thinking that thelonger intake charge tube will act as an air storage compartment and better support the need for air.. I think we can assume that the air charge temp would be lower with the longer charge tube but velocity would be down as a result..
Seems like a fine balance is required between outlet pressure, inlet pressure, velocity and charge purity... Only way to really tell what is working and what is not is to built it and test it.. You got to hand it to the twisted boys.. they are trying new ideas.. and with new ideas comes new products..
Kelsey
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A great compare would be to have a look at the 4 stroke turbo's. Both Bender & MCX elected to build kits that are mounted at the rear of the tunnel which is great for cooling. However, because the exhaust flow needed to travel down the tunnel to reach the turbo and than needed to retutn the boost back up the tunnel the kits were much slower than any front mount kit.
The shortest distance between A + B = Optimum Pressure
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The shortest distance between A + B = Optimum Pressure
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