^ weight removed from the drivetrain (from flywheel down to the rim/tire) will NOT give any crank hp, but will increase whp as less is lost (dissipated)
300 whp without opening your engine?
- Thread starter BBVNSX
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couldn't have said it better or simpler myself :smile:
I agree that an engine with a lighter flywheel will rev up faster and I'm sure you'll agree it will also slow down quicker than an engine with a heavier flywheel.
The difference in rate of change of rpm up or down is due to the amount of energy stored or released by the change in inertia of the flywheel.
The total power, not acceleration rate, available to the transmission is a product of the crankshaft power output plus/minus the stored energy in the flywheel.
In a typical gear shift when the accelerator pedal is lifted, engine power is reduced and the engine decelerates.
This rate of deceleration is slowed by the stored energy in the flywheel which is resisting the engine deceleration rate and is felt as a smoothing out of power delivery.The heavier the flywheel the slower the rate of engine deceleration due to the energy stored in the flywheel.
In short the loss in rate of engine acceleration as the flywheel stores power during the increase of rpm is offset (ignoring friction) during the deceleration phase by slowing the rate of engine deceleration resulting in more power output at a given rpm on the way down.
This doesn't have anything to do with clutch release or shift duration, just the physics of an engine turning a rotating mass during an increase or decrease in rpm. Imagine an engine with a 10 ft diameter flywheel. It might take all day to spin it up to 5,000 rpm but shut off the gas and the engine will spin a long time on the energy stored in that flywheel. I think that's Newton's First Law.
It then seems to come down to the effect of flywheel mass and diameter on the type of power delivery your driving style needs.
A racing application likely wants a light flywheel for faster engine acceleration and deceleration.
A street application may prefer the smoothing effects of a heavier flywheel on daily driving.
In either case the flywheel doesn't change engine power, only the characteristic of engine power delivery.
The Williams F1 team (Williams Hybrid Power) developed a flywheel based energy storage system which was used succesfully by the Audi team in this year's LeMans effort
Jim
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Well yes, but the result (of a LWFW) is more power delivered to the wheels. For example for an engine producing a 100hp, let's say 2 hp is used to accelerate the stock flywheel, and 13hp the rest of the drive tran, this leaves 75hp at the wheels. Let's say we fit a LWFW and it only needs 1hp to accelerate, then 76hp will get the to the wheels.
I assume this is a KERS (Kinetic Energy Recovery System) as widely used in F1. These don't use engine to accelerate those flywheels, instead the flywheel is part of the braking power management system. During heavy braking the flywheel is accelerated because it's inertia assists in providing braking force. In return, some of the energy from the car's reduction in momentum is converted into flywheel momentum = kinetic energy saved as FW revs. Later this is "recovered"by converting this kinetic energy into motive power to add to the cars acceleration, through electric motors I believe, and all driven by some very smart software...
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I agree when considering acceleration, but my point is that the 1 hp difference stored in the stock flywheel is not thrown away.
It will show up under deceleration as the engine power will have 1 hp added from the decelerating flywheel.
The 1 hp is not lost, it just shows up in a different way.
Of course if the throttle is immediately closed and full braking applied then the brakes will have the job of dissipating that 1 hp as heat.
As our V6 engines are not inherently as balanced as say a cross plane V8 perhaps that had something to do with the Honda engineers choice of flywheel weight.
I believe in F1 KERS the electricity generated by the electric motors on the wheels under braking is stored in a battery. When the KERS button is pressed the stored electricity is sent to the same motors to resulting in more power while the electricty lasts.
As I understand the Williams hybrid system, the electricity generated by the electric driving motors under braking is used to spin a flywheel storing the energy in a rotating flywheel rather than a battery
When more power is needed the flywheel energy is converted back to electricity to power the electric motors on the driving wheels.
Apparently this is more efficient than using batteries particularly in endurance racing like LeMans.
I don't know if they use this system in their F1 cars.
Jim
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How about looking at it like this: you need horsepower to overcome the car’s wind resistance, rolling resistance, etc. and when accelerating, its inertia. Decreasing the car’s weight will decrease its inertia and will allow it to accelerate more quickly. But deceasing the weight doesn’t increase the horsepower.
Decreasing the weight of the flywheel decreases the drivetrain’s inertia, which will allow the engine to spin up (and down) more quickly. If you’re accelerating slowly, you probably wouldn’t be able to tell the difference. If you’re accelerating quickly, you might. If you do one continuous dyno pull from 2000 to 8000 rpm that takes two minutes, drivetrain inertia will have little impact on your measurement because the rate of acceleration is so low. If the dyno is set up so that the pull only takes two seconds, a lot of the engine’s power will be used to overcome the flywheel’s inertia.
The shorter your dyno pull, the more of the engine’s horsepower will be absorbed by drivetrain inertia and the less will make it to the rollers. Similarly, if you hold the length of the pull constant, the heavier your drivetrain (the higher its moment of inertia), the more of the engine’s horsepower will be absorbed by inertia. Even if dynos were 100% accurate, the rear wheel horsepower measurement will vary depending on how quickly the car was accelerating on the rollers.
Inertia impacts acceleration, but not top speed. The lighter your flywheel, the easier it will be to accelerate but that won’t impact the maximum amount of horsepower your car is able to put to the road at top speed when the car is no longer accelerating. Inertia doesn’t dissipate power (like wind resistance or your brakes), it stores it.
Decreasing the weight of the flywheel decreases the drivetrain’s inertia, which will allow the engine to spin up (and down) more quickly. If you’re accelerating slowly, you probably wouldn’t be able to tell the difference. If you’re accelerating quickly, you might. If you do one continuous dyno pull from 2000 to 8000 rpm that takes two minutes, drivetrain inertia will have little impact on your measurement because the rate of acceleration is so low. If the dyno is set up so that the pull only takes two seconds, a lot of the engine’s power will be used to overcome the flywheel’s inertia.
The shorter your dyno pull, the more of the engine’s horsepower will be absorbed by drivetrain inertia and the less will make it to the rollers. Similarly, if you hold the length of the pull constant, the heavier your drivetrain (the higher its moment of inertia), the more of the engine’s horsepower will be absorbed by inertia. Even if dynos were 100% accurate, the rear wheel horsepower measurement will vary depending on how quickly the car was accelerating on the rollers.
Inertia impacts acceleration, but not top speed. The lighter your flywheel, the easier it will be to accelerate but that won’t impact the maximum amount of horsepower your car is able to put to the road at top speed when the car is no longer accelerating. Inertia doesn’t dissipate power (like wind resistance or your brakes), it stores it.
Thats exactly why whp gains will decrease when you go through gears (1st - 2nd -3rd - 4th -5th) on your car, your gear box works like a lever, so the efect of decreasing Flywheel inertia is more noticeable when you use 1st or 2nd gear than in 5th or 6th... this lever efect is also related to how fast your car will accelerate, that's why JDM short gears will be faster on low speeds...
I have a question. When Prospeed does the tune for the injectors, is there a whp difference between 91-93? Or is the tune only based on 91 octane so if you were to put in 93 there would be no difference? I'm looking to have NY's first at least 285whp NSX(when I get one, hopefully asap).
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Also due to gearing, larger gears make the topspeed higher add to that the longer the car is in the torque band giving it the push to overcome air pressure.
Was doing some research into this and it appears that there isn't many options on phenolic gaskets... only found this:
http://www.nsxprime.com/forum/showt...NSX-Thermal-Intake-Gaskets?highlight=phenolic
Would it be necessary/recomended to shave the intake manifold to fit those gaskets?
Any other options on phenolic gaskets?
There are no other options for the gaskets. I initially tried getting Hondata to make them, but they weren't interested due to the volume, and they wouldn't disclose their manufacturer. (Boo to Hondata.)
No, you do not need to shave your intake manifold for fitment.
Getting them made is a piece of cake.
Like greenberet and i discussed, shaving would help flow getting the correct balance between flange strength and flow is going to be tricky.
Like greenberet and i discussed, shaving would help flow getting the correct balance between flange strength and flow is going to be tricky.
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Do you know the thickness difference between OEM and Prospeed?
thanks
Do you know the thickness difference between OEM and Prospeed?
thanks
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In his "Thermal Intake Gaskets" thread, Prospeed wrote that his gaskets are made of a different material than stock (he said OEM is phenolic with a rubber seal) and that his gaskets are thicker than stock. I don't think he mentioned how much thicker than stock his gaskets are nor what material they are made of.
^ i bought them and i can measure them and post here, but i don't know the specs for the OEM ones !!
i have the OE ones next to me.
^ i will measure them tomorrow and post here a pic of the thickness.... (just forgot to do it)
It would be very nice if we could compare those values :wink:... what diference in thickness could lead to the necessity of shaving the intake?
man...just forgot to do it...let's see if i remember tomorrow...(knocking head on desk as i write this :biggrin
any major difference i'd say 3-5mm would make it necessary certainly if you see induction trajectory it does come in at quite a angle.It would be very nice if we could compare those values :wink:... what diference in thickness could lead to the necessity of shaving the intake?
Hi,
finally i did it: The Prospeed Thermal Gasket is 3.5mm thick.... the cuts are completely straight, 90º angle to the gasket head/manifold faces.
Nuno
finally i did it: The Prospeed Thermal Gasket is 3.5mm thick.... the cuts are completely straight, 90º angle to the gasket head/manifold faces.
Nuno
OEM = 1,5mm
2mm difference calculate that in the runner/port diameter x air velocity = spoiler/gurney flap idea.
I have a idea on how to improve that, i'll be mailing nuno,
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Would be interested to know too!
Just did some calculations on a spare cylinder head and my manifold drawings.
I've made a re-design on the intake manifold gasket that corrects a flow problem i discovered whist testing in a flow simulator.
Still in design stage.
The Prospeed gasket does effect flow and could react with the valve resonance.
Simplified there are three plains of interaction, the sides of the runner and the center (inline with the injector area). (left, center, right)
From test I've seen that there is a difference in flow between the smooth OEM and the bend caused by the spacer.
Their spacer works because it cools the manifold enough to over come the issue, these spacers are more effective on a inline, boxer and most '60 degree engines (V6 and V12).
This is a V engine at '90 degrees which adds a complexity in bank and manifold angles, this goes as far as interacting with the injector placement. (C-Series, V8 & V10 engines)
My redesign also gives the added feature of further insulation in the manifold itself making partitions to counter heat soak of the cylinder heads.
These won't be major but every-bit helps in NA tuning, it also slightly increase plenum volume.
I'll going to talk with my machine shop, as it's not a 2D piece.
I've made a re-design on the intake manifold gasket that corrects a flow problem i discovered whist testing in a flow simulator.
Still in design stage.
The Prospeed gasket does effect flow and could react with the valve resonance.
Simplified there are three plains of interaction, the sides of the runner and the center (inline with the injector area). (left, center, right)
From test I've seen that there is a difference in flow between the smooth OEM and the bend caused by the spacer.
Their spacer works because it cools the manifold enough to over come the issue, these spacers are more effective on a inline, boxer and most '60 degree engines (V6 and V12).
This is a V engine at '90 degrees which adds a complexity in bank and manifold angles, this goes as far as interacting with the injector placement. (C-Series, V8 & V10 engines)
My redesign also gives the added feature of further insulation in the manifold itself making partitions to counter heat soak of the cylinder heads.
These won't be major but every-bit helps in NA tuning, it also slightly increase plenum volume.
I'll going to talk with my machine shop, as it's not a 2D piece.
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