Jump to content
SAU Community

Horsepower

girlpower

By girlpower,
in Engines & Forced Induction

 Share

Recommended Posts

simpletool Mentor

simpletool

Posted
Posted

A combination of set figure (offset) and percentage (factor).

For a manual I estimate: flywheel(kw) = 20kw + (rwkw x 1.15)

Derived from stock figures. It's estimating it takes ~20kw to spin a gearbox at high rpm, plus you lose a percentage (15%) of gains as friction.

Seems to work well for a lot of cars, and is a hell of a lot better than straight up 25% loss claims!

ie. Stock GTST 140rwkw > 181kw flywheel

My current 230rwkw > 285kw flywheel

A random 300rwkw > 365kw flywheel

2011 Ford GS 256rwkw > 314kw flywheel, even seems to work for new automatics ;)

mad082 Grand Master

mad082

Posted
Posted

as people have said, it can't be a set figure. not just because of how hard the gears are meshing together. you have to remember that the more power it has the faster it is going to accelerate. the faster something accelerates the higher the forces acting against it. so while it might not be exactly a percentage it won't be a fixed figure either. there might be an exact figure of how much power it takes to turn a gearbox, drive shaft, diff, wheels, etc at a set speed, but when it comes to accelerating all that then it won't be a set number that applies to all power levels.

Adriano Grand Master

Adriano

Posted
Posted

A combination of set figure (offset) and percentage (factor).

For a manual I estimate: flywheel(kw) = 20kw + (rwkw x 1.15)

Derived from stock figures. It's estimating it takes ~20kw to spin a gearbox at high rpm, plus you lose a percentage (15%) of gains as friction.

Seems to work well for a lot of cars, and is a hell of a lot better than straight up 25% loss claims!

ie. Stock GTST 140rwkw > 181kw flywheel

My current 230rwkw > 285kw flywheel

A random 300rwkw > 365kw flywheel

2011 Ford GS 256rwkw > 314kw flywheel, even seems to work for new automatics ;)

That looks pretty good,cant we all agree to this

Rolls Grand Master

Rolls

Posted
Posted (edited)
But still Id think a 2000hp would quite easily lose 3-400 through driveline which is still close to 20% but once again the style of driveline would make a huge difference ,for instance a regular sedan with tailshafts compared to a car that has the engine/gearbox bolted directly to the diff..

It might show it on the dyno but there is absolutely no way it is actually losing 400hp, do you have any idea how much heat that would create? it would be enough heat to literally melt the gears if that was the case.

I think a large amount of it is how inertial dynos calculate their figures and they don't actually 'lose' the majority power that we see on a dyno, they just read less due to the way it is being measured, there are losses due to the extra weight being spun up, but they are not completely lost this way.

Edited by Rolls
  • 2 weeks later...
Thelen Rising Star

Thelen

Posted
Posted

A combination of set figure (offset) and percentage (factor).

For a manual I estimate: flywheel(kw) = 20kw + (rwkw x 1.15)

Derived from stock figures. It's estimating it takes ~20kw to spin a gearbox at high rpm, plus you lose a percentage (15%) of gains as friction.

Seems to work well for a lot of cars, and is a hell of a lot better than straight up 25% loss claims!

ie. Stock GTST 140rwkw > 181kw flywheel

My current 230rwkw > 285kw flywheel

A random 300rwkw > 365kw flywheel

2011 Ford GS 256rwkw > 314kw flywheel, even seems to work for new automatics ;)

That is basically the figures I have been using as well. I've always used 15% for manual, 20% for auto, then some % for age. ie, because the skyline is now 15 years old, you loose more power (compression loss, tune loss, just small bits here and there). Rebuilt/modded changes it though and brings it more closely down to the 15%, as does purely having more power (ie so the 20kw base means nothing).

I can't remember what the figures were on a rotary that was engine dyno built and then drivetrain (ie rear wheel) dyno'd, but certainly it couldn't have been even 15% otherwise the gearbox would have fried.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Latest Posts

    • Dose Pipe Sutututu
      Dose's Sometimes DIY and Pay Someone Home & Boat Improvement Thread

      By Dose Pipe Sutututu · Posted

      Wife wanted basket things in the wardrobe in our temporary house. Thought about ripping our the wardrobe and fitting the entire IKEA set, but it's a temporary house and we want to move in a few years. So IKEA advertises this as a 50cm unit, however the actually basket and rails measure 46cm wide. Only issue was depth, IKEA stuff is quite deep, where as the builder special junk is super shallow at less than 40cm. Send it, chopped the rails, then offset the mounting holes, job done, happy wife, less shit scattered all over the bedroom. Did the same to the other side too. Also drove the Skyline shit box today, dropped off oil at Supercheap Auto. I didn't realise they only now take max 2x bottles per visit. I visited 2x Supercheap Autos.  
    • Kinkstaah
      Strange issue RB25DET wont start

      By Kinkstaah · Posted

      I've seen similar actually in my situation. You never know what tables are attempted to be used when the car thinks it's -99C or +200C. The fail state is not usually that extreme but you know what I mean - it was in my case though! This is where being able to read all the sensors is useful cause you see this stuff really quickly.
    • Kinkstaah
      First time Skyline owner

      By Kinkstaah · Posted

      The above is very important. However as long as you keep timing relatively low, it's plausible to make your own knock ears and plausible to learn to tune with a modern ECU that can do wideband O2 correction like a boost controller. I mean if you only have one viable road to even drive the car on, learning to tinker to this level may be worth doing given you can't do much else with the car...?
    • Kinkstaah
      Chris' Toyota Mark ii JZX110

      By Kinkstaah · Posted

      I find the fact that the rear plate has to be bent inwards at the rear not so bad: but the front is just awful: It's like come on. (these are my very old, now retired/turned in plates) TBH it is a lot of money to fix a minor issue, the fact I said "I'll never really spend the money on doing this" is why people ended up buying them as a gift for a 'car guy' who can be hard to shop for.. for car guy things.
    • GTSBoy
      Chris' Toyota Mark ii JZX110

      By GTSBoy · Posted

      I just bent the ends of my premo plates. It even went through Regency like that after the engine conversion and the inspector (a great bloke!) just squinted his eyes and said "I didn't see that". Plates, and how they look, are just something that have zero importance to me.
×
×
  • Create New...