Did i struck a nerv?
I am rather offended by that last sentence....
I have done the weight-loss program on my m3 trackcar flyweel in my own lay and the gain did show up on the dyno.
I am saying the ectra weight in the pulley probably is not the holy grail.
But what do know.....

Regards. Ben

 

Hello, sorry I dig about it but what specialists think about ATI Dampers ?
http://www.atiracing.com/products/dampers/index.htm

I think reducind moving mass does not give more hp but just help engine to rev up faster, isn't it ?

The mass (cranck pulley, flywheel) help to smooth the torque produced by the engine and reduce vibrations, isn't it ?

 

A light weight damper doesn't increase hp/tq, your right..but if you were to dyno a before and after you will notice a difference in a higher hp/tq number in the lower end.

Now this doesn't mean you increased power, what you actually did is "regain" power back that was eaten by by the accessories and driveline.

Ever notice when a spec shows the car makes 430bhp(which is just the engine with nothing added, no power steering, Ac, alt, pulleys, damper), you get the car on the dyno and now only see around 365hp..but what ever happened to the brochure spec of 430bhp??

The dyno horsepower is what is outputted from the engine to the ground by the wheels( that's as the car is, with all accessories AND the loss of power through the drivetrain..so 365whp = 430bhp for the car of this example . Now on the dyno sheet you will notice at 365whp, that's usually near the end of the graph, not at the beginning, at 2,000rpm you might only have 200whp...

If you put a lightened damper, you will not increase your 430bhp number or even your 365whp number, but you will see a difference somewhere on the dyno graph showing more..ex at 2,000rpm when you made 200whp, you might now see 201whp and carry this up on the power band somewhere... So by regaining hp back from what was lost from that initial 430bhp number will automatically net you a faster rpm response...you've lightened the load needed to make the 430bhp.

As for the throttle response...

Think of 2 x18 wheels(don't think of power, think of the large flat shape of the truck), both are same size and model..

Truck A is 7 tons and truck B is 500lbs..if both are rolling at 60mph and both drivers lift the throttle at the same time a wind gush hits..truck A will keep travelling but Truck B will drastically slow down.... And when both trucks hit the throttle, due to the weight difference truck B will speed up faster...although both make the same amount of power..

So by lightening the load will allow the throttle to respond faster BUT depending on how much lighter will also affect how fast the throttle dives when you lift vs hanging there for a few second...with also affects fuel mileage. If you lift with a heavy damper on the throttle, few seconds is needed for rpm to react, which means no fuel is being injection and maintaining the same rpm..when you put a light damper, once you lift, rpm reacts faster which requires more fuel to constantly maintain the idle required when load is lifted.....

But, there's always 2 sides to a story..so to get the power moving requires power..a heavier weight will require more fuel. So by having a heavy damper will require more fuel to get the rpm turning.. And a light damper will require less fuel.

So depending on the driving scenario, a light damper can increase or decrease fuel mileage..all driver request and exterior terrain/weather conditions dependant.

Sry if this all sounds like a run on sentence, writing by my cell on a uncomfortable waiting chair. :-S

 

I've been thinking about this damper issue with my V8 Vantage... My Audi R8 had a lightweight damper which while it offered better throttle response, it was a drag as it hampered smooth driving and made highway driving fatiguing. All things considered, I've decided that I'm going to leave my flywheel as is.

 

So if I understand :
- if I drive my car cool : OEM damper is perfect,
- but if I drive my car in insane mode lightweight damper is perfect.
Am I right ?

Thanks a lot Irish ;-)
Are you in the hospital ?
Mom and baby are they fine ?
Congrat ;-)

For the dyno, I put my car on a power bench, so I have the power and the torque on the rear wheels.

I know then if I put a smaller pulley I can obtain more power and more torque by less energy consumption for accessories and driveline.
Am I right ?

And about ATI Damper what do you think about it ?

 

heavy damper = smoother driving, but sluggish response. Better for a GT car.
light damper = quicker engine response (both revving up and losing revs), but not as smooth driving. Better for a race car.

If you use a *smaller* pulley, you need to change your FEAD belt. Also, you'll be putting more strain on your accessories because they'll be spun faster.

Not sure if the ATI damper will do anything, I've never used one.

As for power at the wheels:

A vehicle dyno (aka "rolling road") measures the power that is actually put down to the pavement (power that is actually getting transmitted through the wheels to the road - meaning, wheel horse power - WHP). An engine dyno (or engine brake dyno) measures power directly coming from the engine - this means the engine is NOT in a car.

Power figures that are published by manufacturers are BHP (brake horsepower - as in, engine brake dyno readings). They measure the power from the engine on an engine dyno, then stick it in a car. Once in the car, power is lost going from the engine to the ground - everything takes a toll. You lose power moving accessories (A/C, power steering, etc). You lose power spinning your flywheel. You lose power twisting a differential. You lose power throughout the drivetrain.

When I dyno'd my ~410 BHP car (4.3L w/ Power Pack and high-flow cats), I put down 343 WHP. That means I lost 67 HP between my engine and the road.

Swapping out certain components, specifically the crank pulley and flywheel, for lighter ones reduces that power loss. So instead of losing 67 HP, maybe I'd only lose 57 HP because my lightweight flywheel takes 10 fewer HP to get spinning. Now I'd be putting down 353 WHP, but my BHP would still be the same at 410.

 

Many thanks Telum,

Now I understand the difference between WHP and BHP (sorry I am French I dont understand everything at the first time ;-)).

Probably Whp for Wheel Horse Power, and BHP for Bench Horse Power...

 

No worries, language is always fun to work around Here we go - pictures to clear it up!

This is a rolling road / vehicle dyno / chassis dyno (different names, same thing). It measures wheel horsepower (WHP)



This is an engine dyno / brake dyno. It measures brake horsepower (BHP)



I'm honestly not sure what a power bench is - that's a new term for me, sorry!

 

Dont be sorry I made a mistake the true is Brake not Bench....

 

Lightweight crank pulley will increase the HP & TQ on the dyno, it has for decades on various platforms. You will pick up a lot more torque earlier in the power band, but the gains at very high rpms are far less than down low.

Also, just because a damper is heavier does not mean it is smoother. I have always felt my engines were smoother after doing crank pulley than the stock damper, but I suppose is is more a subjective thing. What is for certain, the stock sluggishness comes from the ginormously heavy stock crank damper. Event the ford counterparts weigh much less. I do not recommend getting an underdrive pulley, it's not worth the sacrifice, just get a stock diameter lightweight pulley

Bottom line, it's a torque mod. If you want more torque... Nothing beats a lightweight crank pulley.

 

I kind of wanted to stay off this thread; every point of view seemed to have been covered.
But here goes
I believe there are two different engine parameters here. The go fast guy who wants to make the most horsepower. Then there is the factory, who also wants to make the most horsepower, but have other hard parameters the go fast guy does not have.

Theoretical example.
Aston Martin builds the 4.3 engine and after final testing certifies the BHP at 380.
However earlier in the testing process they were getting 440 BHP. The problem is that the engine required race fuel (not readily available) along with open headers and an ignition timing not suitable for street cars.
93 octane fuel requirements meant a loss of 15 HP
Noise parameters meant long tube headers and no mufflers were out. There goes 20 HP
Compression ratio and igniting timing reductions? Another 15 HP.
Maximum RPM lowered to 73000, another 10 HP reduction. You see where I am going with this. Car manufactures have to worry about stuff that go fast guys don’t.
In looking at the lightened crank pulley I offer a theory. Aston Martin engine department long term tests indicate that main engine bearing life was somewhat reduced with the lighter pulley.
Note: the go fast guy does not care if the engine lasts 100 or 200 thousand miles. Aston Martin absolutely does. Their reputation depends on it. In the final analysis they determined a slightly quicker response that would be imperceptible to the average driver was not worth comprising the longevity of the engine and possible sullying their reputation

My 2 cents

 

you're absolutely correct - everything done by the manufacturer has numerous concerns to address.

 

The only reason they went to such crazy extremes is because Aston requirements of Cosworth were so insanely high. Keeping an engine at redline for 100 hours straight is absurd, no manufacturer on earth uses that as their benchmark. It's also why Aston has the smoothest redline cutoff out of any manufacturer.

You can easily keep engine reliability to 150-200k miles for the engine and still put a bunch of "go fast" buts on the car. It's a myth that you somehow have to sacrifice one for the other, that's simply not true.

 

There's a reason why race engines get rebuilt as often as they do...