which "other thread" covers the "proper intake manifold? thanks
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on the dyno with comptech cams...
- Thread starter austrian type-R
- Start date
All a dyno must know is the power it is measuring and the speed of the engine (tachometer hook-up). Engine power is measured at the wheels and engine torque is deduced from the tachometer reading. Since power is conserved, the gear-ratio, wheel diameter, 1:1, 0.967:1, 1.033:1, etc is irrelevant, which is why the dyno guys don't ask.
In reality, however, the power is not measured at steady engine RPMs (most accurate), it is measured during a sweep. Because of this highly transient sweep, the drivetrain inertia is very relevant. Minimizing the drivetrain inertia makes the engine's performance more measurable by the dyno (not dampened by the drivetrain). On this note, for comparison, it is a good idea to use the same wheels & tires, as not to change the drivetrain inertia, therefore the dyno numbers.
Lucas
That's my point: the dyno knows the gear ratio as a result of comparing the engine rpm to the dyno speed. You need not input it manually but it is a necessary part of calculating torque.
Dynos measure torque and can calculate horsepower if they know the engine speed. They can measure the engine speed from the ECU or a tachometer pickup loop or they can guess the engine speed based on the roller speed and the gearing and tire sizes the operator entered. If they have to guess the engine speed based on roller speed, then tire slip, tire wear, incorrectly entered gear ratios, etc. can impact the calculated horsepower figures.
The weight of a car pushes down on and deforms the tires where they contact the road. As the tires roll, they get kneaded. Kneading the tires takes energy so the faster the tires roll, the more energy they absorb. The higher the gear in which you perform a dyno test, the more energy will get swallowed by kneading the tires.
As has been pointed out, a lot of dynos are inertia dynos that measure the rate at which your car can accelerate a big drum. When performing the test, your engine doesn't just have to get the drum spinning though, it also has to accelerate your flywheel, wheels, etc. Changing your wheels or flywheel obviously doesn't change your engine's horsepower but it does change how fast your car can accelerate a drum and therefore the results an inertia dyno will spit out. During a continuous pull to the redline, the lower the gear you are in, the more of the engine's power will get swallowed by drivetrain inertia.
So the higher the gear you are in, the more of your engine's energy will get absorbed by the tires but the less will get absorbed by drivetrain inertia. If you use a hub dyno like austrian type-R did, at least you take the tires out of the equation.
The weight of a car pushes down on and deforms the tires where they contact the road. As the tires roll, they get kneaded. Kneading the tires takes energy so the faster the tires roll, the more energy they absorb. The higher the gear in which you perform a dyno test, the more energy will get swallowed by kneading the tires.
As has been pointed out, a lot of dynos are inertia dynos that measure the rate at which your car can accelerate a big drum. When performing the test, your engine doesn't just have to get the drum spinning though, it also has to accelerate your flywheel, wheels, etc. Changing your wheels or flywheel obviously doesn't change your engine's horsepower but it does change how fast your car can accelerate a drum and therefore the results an inertia dyno will spit out. During a continuous pull to the redline, the lower the gear you are in, the more of the engine's power will get swallowed by drivetrain inertia.
So the higher the gear you are in, the more of your engine's energy will get absorbed by the tires but the less will get absorbed by drivetrain inertia. If you use a hub dyno like austrian type-R did, at least you take the tires out of the equation.
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That's all very helpful, thanks. But I have a question about this regarding inertia:
For a very low gear, the engine feels the inertia of the post-transmission drivetrain and dyno much less. The gear ratio, however, has no effect on the inertia of the pre-transmission drivetrain. So changing the gear ratio changes the relative influence of the pre- and post-transmission drivetrain. If the point is to isolate the dyno inertia, using a tall gear will help minimize the effect of pre-transmission inertia but I don't understand how the gear ratio changes the balance between the post-transmission inertia and the dyno inertia.
Also, with these dynos, why can't they do a run with no tire-dyno contact, which would give an idea of the drivetrain inertia based on how fast the rpm climbs? Seems like you could get a decent way down the road of actually quantifying drivetrain-inertia effect.
For a very low gear, the engine feels the inertia of the post-transmission drivetrain and dyno much less. The gear ratio, however, has no effect on the inertia of the pre-transmission drivetrain. So changing the gear ratio changes the relative influence of the pre- and post-transmission drivetrain. If the point is to isolate the dyno inertia, using a tall gear will help minimize the effect of pre-transmission inertia but I don't understand how the gear ratio changes the balance between the post-transmission inertia and the dyno inertia.
Also, with these dynos, why can't they do a run with no tire-dyno contact, which would give an idea of the drivetrain inertia based on how fast the rpm climbs? Seems like you could get a decent way down the road of actually quantifying drivetrain-inertia effect.
Poor guy's thread got turned into a dyno debate. I love prime 
Brain damage aside...there's one thing I do know.. my Red car with the Type R final drive and the JDM gears feels fast as hell! Not sure how the dyno will read the big grin on my face every time I reach that 3rd gear redline.
Brain damage aside...there's one thing I do know.. my Red car with the Type R final drive and the JDM gears feels fast as hell! Not sure how the dyno will read the big grin on my face every time I reach that 3rd gear redline.
I thought it was more of an educational discussion rather than a debate.
On preferentially using a 1:1 ratio, from what I gather poking around, that is to minimize loss within the transmission itself, not to change how the loss affects the dyno computation. And that makes sense because it is the ratio within the transmission alone, not that of the overall drivetrain.
On preferentially using a 1:1 ratio, from what I gather poking around, that is to minimize loss within the transmission itself, not to change how the loss affects the dyno computation. And that makes sense because it is the ratio within the transmission alone, not that of the overall drivetrain.
Poor guy's thread got turned into a dyno debate. I love prime
Brain damage aside...there's one thing I do know.. my Red car with the Type R final drive and the JDM gears feels fast as hell! Not sure how the dyno will read the big grin on my face every time I reach that 3rd gear redline.
I personally feel responsible.. Sorry OP!
Ryu, can't help you there, happiness is subjective. Science doesn't play nice with "feelings", those Neuroscience guys will try to convince you otherwise though hahaha.
I bet the higher final drive ratio is a blast.
It may seem like that , but it's actually the other way around. Because the drivetrain is accelerating much more in the low gear compared to a high gear significantly more torque is lost to overcoming rotational inertia of the drive train .
This is main reason it's better to dyno in a high gear. Yes rolling friction losses (kneading etc) are less in a low gear but the rotational inertia losses are far more significant in a low gear than a high gear. (and when you go real road driving even the front wheels count in these inertia losses, hence why lighter wheels are important)
For anyone interested in more detail see the discussion of "rotational inertia coefficient" (Cri) on page 328 of the Bosch Automotive Handbook, where it explains the effect of all rotational interia (wheels, flywheel, crank etc) has effect of increasing the vehicles apparent mass, and Cri is higher the lower the gear.
To give you an idea how inertial forces really matter when accelerating, for an NA1 NSX the Cri is around 1.28 in 1st gear compared to 1.05 in 5th gear. In other words, from the engine's perspective the cars apparent mass is 22% more (1.28/1.05 = 1.22) when accelerating in 1st gear compared to 5th gear !
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I would have to look at the Bosch text to know but suspect you are looking at things from the dyno's perspective or from the road's perspective. The idea of reflected inertia is very straightforward and gear reduction from the motor to load means the load appears as low inertia to the motor. See http://www.engineersedge.com/motors/gear_drive_system.htm
I think what you mean is that because the pre-transmission inertia is higher from the road's perspective when using a low gear, it increases the apparent mass of the car. Makes sense.
For a dyno, the post-transmission drivetrain inertia cannot change relative to the dyno inertia. But the pre-transmission inertia can and you certainly reduce that relative to the dyno by using a tall gear. We're all on the same page here. Let's be accurate though. I'd like to see the equation you are using for Cri and how that fits into the car's linear dynamics.
Taken on it's face, this would suggest that the car accelerates quicker in 5th gear, because from the engine's perspective, the maximum torque output never changes.
Back on topic, it's great to see this combo finally on a dyno. It goes to show when you do cams, compression and engine management, there is a lot of power on tap in the C30A. The "street" combo would probably be:
SOS high-comp pistons (90mm)
SOS NA cams
CT Cam Gears
SOS AEM v2
SOS big bore throttle
RDX or RC injectors (270cc +)
Reliable Tuner
SOS high-comp pistons (90mm)
SOS NA cams
CT Cam Gears
SOS AEM v2
SOS big bore throttle
RDX or RC injectors (270cc +)
Reliable Tuner
What i'd like to know is what's the timing advance threshold on this type of motor. Timing on a NA motor can make a decent impact.
On my stock 3.0L boosted on 7psi we started detected hints of knock at 3* of advance. We backed it down to 1* of advance which is where i'm at now. Hate this crap California gas. They're so strict on emissions yet give us the crappiest gas to work with.
On my stock 3.0L boosted on 7psi we started detected hints of knock at 3* of advance. We backed it down to 1* of advance which is where i'm at now. Hate this crap California gas
. They're so strict on emissions yet give us the crappiest gas to work with.
SOS pistons are the Wiseco 2618 forged pistons.
If I were you I would look for the Wiseco 4032 forged pistons.
For an all engine application I think this is better suited since it's a lighter piston and there is less piston contraction and growth concerns when cold starting as you see in the 2618 material.
2618 is less brittle which is great if you are worried about forced induction detonation, but will burn more oil (sometimes a quart every 1k miles if you cold start often) during the cold start process.
2618 pistons will wear out faster when cold since they will "slap" around (making piston slap noise) in the combustion chamber before expanding.
Rest of the items noted are fine by me.
Of course I would go beyond with upgrading to lighter valves port matching and clean up (smooth out rough casting texture and sharpen up the vein).
Finally thermo coating (both barrier and dissipation).
Most of this is covered in my hijack DIY engine build on Mac Attack's thread.
I am about to have all this done but with a Link system and on a 3.2 OEM block, the heads have been ported at Portflow with the larger valves and complete valve train WPC coated so the only thing i wont have is different pistons, what's everyones thoughts on how much of a difference would the pistons make. I will be dynoing it later this year and posting up for reference
Hijacking continues ... with apologies to those bored with dyno analysis
I’m thinking from the engine’s perspective. The goal (I think) is to figure out engine power at the crank when all we have is the dyno measured power at the roller. So we need to consider all rotating parts post-crankshaft and their contribution to the inertial losses.
Not really. The rate of acceleration is much higher in 1st than 5th gear … for everything: car, post-transmssion parts, pre-transmission parts etc. So even the “pre transmission losses” (e.g. clutch/flywheel) are affected by gear chosen.
We need to keep in mind it’s not the rotating speed (angular velocity) of rotating parts it’s only their angular *acceleration* that matters. (Apologies if that sounds like “how to suck eggs”)
Well yes, on the face of it. But our mortal enemy gets in the way: aero drag :frown: Hmmm … raises an interesting question: how does a dyno roller simulate aero drag?
See attached the Bosch book section on "motor vehicle dynamics". Rotational inertia is discussed on page 328, figure 3 and paragraph headed "Acceleration" (note what I've called "Cri" they call "km" (that's k-subscript-m). Must mean something useful in German!).
I worked out values for NSX for horizontal axis of Bosch figure 3 and using curve 1 (NSX with driver on board is 470kg/l) read off the Cri values from 1.05 up to 1.28 for a US 5 speed NSX.
For example, in 1st gear 0.3i/r = 0.3 * 12.474 / 3.071 = 11.96 therefore Cri = km ~= 1.28
Sure it's a very "top down" method, and only approximate, but still useful for this topic.
View attachment 110975
I’m thinking from the engine’s perspective. The goal (I think) is to figure out engine power at the crank when all we have is the dyno measured power at the roller. So we need to consider all rotating parts post-crankshaft and their contribution to the inertial losses.
Not really. The rate of acceleration is much higher in 1st than 5th gear … for everything: car, post-transmssion parts, pre-transmission parts etc. So even the “pre transmission losses” (e.g. clutch/flywheel) are affected by gear chosen.
We need to keep in mind it’s not the rotating speed (angular velocity) of rotating parts it’s only their angular *acceleration* that matters. (Apologies if that sounds like “how to suck eggs”
)Well yes, on the face of it. But our mortal enemy gets in the way: aero drag :frown: Hmmm … raises an interesting question: how does a dyno roller simulate aero drag?
See attached the Bosch book section on "motor vehicle dynamics". Rotational inertia is discussed on page 328, figure 3 and paragraph headed "Acceleration" (note what I've called "Cri" they call "km" (that's k-subscript-m). Must mean something useful in German!).
I worked out values for NSX for horizontal axis of Bosch figure 3 and using curve 1 (NSX with driver on board is 470kg/l) read off the Cri values from 1.05 up to 1.28 for a US 5 speed NSX.
For example, in 1st gear 0.3i/r = 0.3 * 12.474 / 3.071 = 11.96 therefore Cri = km ~= 1.28
Sure it's a very "top down" method, and only approximate, but still useful for this topic.
View attachment 110975
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I think you're losing track to what gearing is. An engine dyno measures the engines power (1:1 ratio due to no transmission). If you had zero gears in a car and directly connect the engine to the wheels, there is not enough torque to get the car moving. Its like starting an nsx in 4th gear from a stop (closest to 1:1 ratio). Gearing multiplies torque, allowing the ~200lb-ft nsx motor to be able to accelerate the car. This torque multiplication is not as accurate on the dyno as a 1:1 ratio gear. Aero drag has nothing to do with the dyno, again you're trying to measure the power (well torque) of the engine from the drive wheels and a 1:1 ratio transmission gear usually results around a 15% drive train loss from the engines true output.
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An engine dyno has the engine is pulled from car, held in a stand and connected direct to the dyno, without any of the drivetrain present, not even clutch/flywheel. Then you get to measure actual engine power. All roller dyno readings, and even a hub dyno, have to contend with drivetrain losses due to rotational inertia, more in a low gear, less in a high gear. Chosing a 1:1 ratio helps but it doesn't eliminate.
austrian Type-R: please add your dyno chart and specs to the Dyno Library:
http://www.nsxprime.com/forum/showthread.php/109312-NSX-Dyno-Library-Registry/page2
thanks!
http://www.nsxprime.com/forum/showthread.php/109312-NSX-Dyno-Library-Registry/page2
thanks!
Increased compression alone will not add much. But, with cams and engine management, I would highly recommend it. Probably worth at least 20 whp on the NSX. Also, Bats is right. For a NA car I would stick with 4032 alloy, since it expands much less and will give you a more OEM-like oil consumption. 2618 is really for FI and high-output V8 drag cars.
I'm not convinced that the SoS NA cams (Web re-grinds) have enough lift or duration on the high-lift side to make a significant difference (i.e., make it worth the time & money spent). IMO the worthwhile options for now are Comptechs (discontinued) or Todas.
I'm also not convinced that the SoS big bore is worthwhile either, as their advertised +5 mm has been found by several owners to be closer to 2-3 mm.
As to the cam gears, this is a tough one. The cam gears are just about impossible to tune with the engine in the car. You have to strap the motor to an engine-dyno, test, re-adjust, re-test, repeat, get to final (best) results, then return the engine to the car. Giant PITA, IMO.
AEM EMS + a knowledgeable tuner is critical.
A good read:
"The two main types of forged aluminum pistons are 2618 aluminum alloy and 4032 aluminum alloy. Either type can be used in street or race-only applications but there are a few differences. The 2618 alloys used by many of the aftermarket piston manufacturers have a low to zero silicon content. The 4032 alloy forged pistons have a higher silicon content but still much less than what is found in the stock eutectic and hypereutectic cast aluminum alloy pistons found in the stock Zetec and Duratec.
The amount of silicon is directly proportional to how ductile the piston is, or in simple terms how "hard" or "soft" the alloy is. While a high silicon content piston like the stock units are technically stronger since the alloy has a tighter bond at the molecular level, they're also more brittle and don't stand up to detonation as well as a forged piston with less silicon content. That is one of the primary benefits of a forged piston over a cast piston in that they are somewhat softer and can absorb the occasional mild detonation better than a cast piston. If detonation is too severe, exhaust gas temps too elevated, or a combination of both you can still kill a forged piston but they're generally more tolerant.
The other reason a forged aftermarket piston is better for forced induction applications is due to the design of the stock piston. The stock cast pistons in a naturally aspirated engine are generally light weight to reduce rotating assembly mass which is better for performance and economy but that means there usually isn't as much material in key locations to help keep the piston from deforming when cylinder pressures go up once boost is applied. The stock pistons also generally have very small ring lands with the rings placed close to the top of or "crown" of the piston. This helps with emissions by minimizing the space between the piston and the cylinder bore of the block above the upper compression ring where un-burnt fuel and hydrocarbons can get trapped. Combined with rings that may not be optimal for forced induction and any severe detonation under boost can lead to damaging the ring and/or ring land.
Back to the forged alloy pistons, as mentioned earlier, the 2618 alloys have a lower silicon content than the 4032 alloy and the 2618 alloy is therefore softer. This means the piston will wear out faster than some of the higher silicon content alloys like the 4032. They also have greater thermal expansion and need looser bore clearances to allow for expansion as they heat up. This causes many of the forged pistons to have "piston slap" when cold. This is basically the piston moving around in the bore until it warms up and expands and it sounds like a slapping sound as the name implies. It won't damage anything but can be annoying on a daily driver and you really need to be careful to fully warm the engine up before driving it hard (which is best for any engine but especially important on one with these types of forged pistons).
CP primarily uses a 2618 alloy as does many of the other piston makers. Their alloy is low silicon content like most JE, Wiseco and other pistons designed for forced induction applications. Venolia on the other hand favors a zero silicon content 2618 alloy that can stand up to slightly more abuse but technically may wear out faster and have more piston slap (and by shorter service life that could be 50k, 75k or even 100k or more on a daily driver depending on how the car is driven).
There are only a couple sources in the industry for the raw piston blanks or "slugs" a forged piston is machined from, so the material can be essentially the same between aftermarket piston companies with the main difference in the design and machining. CP has very good machining and if the design is strong and catered towards your usage and power goals I wouldn't have any reservations running them.
-Eric H"
"The two main types of forged aluminum pistons are 2618 aluminum alloy and 4032 aluminum alloy. Either type can be used in street or race-only applications but there are a few differences. The 2618 alloys used by many of the aftermarket piston manufacturers have a low to zero silicon content. The 4032 alloy forged pistons have a higher silicon content but still much less than what is found in the stock eutectic and hypereutectic cast aluminum alloy pistons found in the stock Zetec and Duratec.
The amount of silicon is directly proportional to how ductile the piston is, or in simple terms how "hard" or "soft" the alloy is. While a high silicon content piston like the stock units are technically stronger since the alloy has a tighter bond at the molecular level, they're also more brittle and don't stand up to detonation as well as a forged piston with less silicon content. That is one of the primary benefits of a forged piston over a cast piston in that they are somewhat softer and can absorb the occasional mild detonation better than a cast piston. If detonation is too severe, exhaust gas temps too elevated, or a combination of both you can still kill a forged piston but they're generally more tolerant.
The other reason a forged aftermarket piston is better for forced induction applications is due to the design of the stock piston. The stock cast pistons in a naturally aspirated engine are generally light weight to reduce rotating assembly mass which is better for performance and economy but that means there usually isn't as much material in key locations to help keep the piston from deforming when cylinder pressures go up once boost is applied. The stock pistons also generally have very small ring lands with the rings placed close to the top of or "crown" of the piston. This helps with emissions by minimizing the space between the piston and the cylinder bore of the block above the upper compression ring where un-burnt fuel and hydrocarbons can get trapped. Combined with rings that may not be optimal for forced induction and any severe detonation under boost can lead to damaging the ring and/or ring land.
Back to the forged alloy pistons, as mentioned earlier, the 2618 alloys have a lower silicon content than the 4032 alloy and the 2618 alloy is therefore softer. This means the piston will wear out faster than some of the higher silicon content alloys like the 4032. They also have greater thermal expansion and need looser bore clearances to allow for expansion as they heat up. This causes many of the forged pistons to have "piston slap" when cold. This is basically the piston moving around in the bore until it warms up and expands and it sounds like a slapping sound as the name implies. It won't damage anything but can be annoying on a daily driver and you really need to be careful to fully warm the engine up before driving it hard (which is best for any engine but especially important on one with these types of forged pistons).
CP primarily uses a 2618 alloy as does many of the other piston makers. Their alloy is low silicon content like most JE, Wiseco and other pistons designed for forced induction applications. Venolia on the other hand favors a zero silicon content 2618 alloy that can stand up to slightly more abuse but technically may wear out faster and have more piston slap (and by shorter service life that could be 50k, 75k or even 100k or more on a daily driver depending on how the car is driven).
There are only a couple sources in the industry for the raw piston blanks or "slugs" a forged piston is machined from, so the material can be essentially the same between aftermarket piston companies with the main difference in the design and machining. CP has very good machining and if the design is strong and catered towards your usage and power goals I wouldn't have any reservations running them.
-Eric H"
http://www.nsxprime.com/forum/showthread.php/154927-Semi-DIY-Mild-Engine-Build-for-FI/page10
I've mentioned this in my engine build.
Koneggsegg supposedly uses Diamond Pistons that are CNC milled from 7075.
<iframe width="640" height="360" src="//www.youtube.com/embed/wVarKLId0wE?feature=player_detailpage" frameborder="0" allowfullscreen></iframe>
I've mentioned this in my engine build.
Koneggsegg supposedly uses Diamond Pistons that are CNC milled from 7075.
<iframe width="640" height="360" src="//www.youtube.com/embed/wVarKLId0wE?feature=player_detailpage" frameborder="0" allowfullscreen></iframe>
unfortunately i didn't get the Comptech cams i wish they still made them and the Toda's are just too much money for the gains, hopefully the new intake manifolds being talked about will offer something other than the SOS enlarged TB but until then it is really the only one option available to help increase flow. Cam gears not worth the money either and you don't seem to need them with these options of cams
The cam gears were setted to the Tuners experience and yes, you defenitly need an good tuner who know his stuff.
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