new top speed

[OppoLock]

Of course! The inertia of weight that the engine has to overcome to put power to the ground directly corresponds to the response time.

Right, the basic concept is completely logical, but I thought that the driveshaft's inputs would be dampened by other connecting pieces in the drivetrain. Like, I get that on some technical level the response has improved, but not to the point that the driver would detect anything (hence the use of 'tangible' in my previous post). Not like a low-weight flywheel.

Edit: like in reference to this post discussing the F80 M3/M4 CF driveshaft. I don't know what kind of education or credibility that "swamp2" poster has, but his explanation makes sense. I also don't have any first-hand experience with a vehicle that's gone from a stock to lighter driveshaft. I'd be interested in hearing from someone who has, but I'm also cautious of the potential for bias/placebo effect considering that anyone dropping $1,000+ on a driveshaft is going to want to think that their purchase is justified.

I'm really intrigued to drive this. Anytime you dramatically reduce the weight of an integral rotating part, the feeling of direct-response increases. The flywheel is probably the most classic example.

Not exactly. It is basically the same as loosing weight with the added benefit that it is rotating weight. Performance is increased although the effect of this part alone won't be big enough to be felt. Now if you are talking about how quick an engine will rev in neutral that is a whole different thing which is affected much more by large changes to flywheel moment of inertia reductions

But the driveshaft has always been the longest rotating part of the assembly and the most prone to torsional forces as a result - so now I'm really curious how a super stiff super lightweight driveshaft feels in a high torque application.

You, nor a seasoned race driver will not be able to tell the difference. The main reason is that the overall torsional stiffness of this part of the drivetrain is governed by the hard rubber "mating" parts that give the drivetrain a much decreased torsional rigidity giving the driveline an acceptable level of feel and "forgiveness". Those parts of the system will have their stiffnesses altered to accommodate the new design but very well might have their stiffnesses decreased substantially.

In short slightly more performance, non detectable.

http://f80.bimmerpost.com/forums/showthread.php?t=921523

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[EiBStudent]

Right, the basic concept is completely logical, but I thought that the driveshaft's inputs would be dampened by other connecting pieces in the drivetrain. Like, I get that on some technical level the response has improved, but not to the point that the driver would detect anything (hence the use of 'tangible' in my previous post). Not like a low-weight flywheel.

Edit: like in reference to this post discussing the F80 M3/M4 CF driveshaft. I don't know what kind of education or credibility that "swamp2" poster has, but his explanation makes sense. I also don't have any first-hand experience with a vehicle that's gone from a stock to lighter driveshaft. I'd be interested in hearing from someone who has, but I'm also cautious of the potential for bias/placebo effect considering that anyone dropping $1,000+ on a driveshaft is going to want to think that their purchase is justified.



http://f80.bimmerpost.com/forums/showthread.php?t=921523

Regarding the seat of your pants noticeability I can't speak for that personally. I have, however, spoken to a few people at local AutoX events that claim they did notice a difference in response while driving. I suppose it could be a placebo affect though.

 

[volsfan0911]

Unless I go back to Montana, doubt that I'll ever get to wring anything out much past 120 on the East Coast. Did hit 135 in a rental Maxima (allegedly capped at 128 mph) heading back to Miles City from Billings on I-94 East. One beautiful thing about that state! :love: Lots of highway, very little traffic or law enforcement presence

 

[Grimace427]

Driveshaft weight actually has a tangible effect on throttle response? First time I've heard that.

Of course! The inertia of weight that the engine has to overcome to put power to the ground directly corresponds to the response time.

Throttle response is the delay from pressing the throttle pedal to the engine beginning to rev. While installing a lighter driveshaft will make the car accelerate a little quicker, the fact that the driveshaft is directly connected to the drive line and not the engine means that it does not improve throttle response. Even a lightweight flywheel which definitely makes the engine rev quicker does not actually change the engine response time though it certainly feels quicker.

Things that improves throttle response are a tune with a more aggressive throttle pedal curve, a shorter/less restrictive intake path, a complete burning air/fuel charge, and less restrictive exhaust.

 

[EiBStudent]

I suppose it's semantics. But, I understand what you're saying.


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[OppoLock]

Throttle response is the delay from pressing the throttle pedal to the engine beginning to rev. While installing a lighter driveshaft will make the car accelerate a little quicker, the fact that the driveshaft is directly connected to the drive line and not the engine means that it does not improve throttle response. Even a lightweight flywheel which definitely makes the engine rev quicker does not actually change the engine response time though it certainly feels quicker.

Things that improves throttle response are a tune with a more aggressive throttle pedal curve, a shorter/less restrictive intake path, a complete burning air/fuel charge, and less restrictive exhaust.

Aha, that makes sense, so what's the proper terminology that EiB and I should be using? Drivetrain response? Sounds a little too all-encompassing.

 

[IGJoe2192]

I think calling it throttle response would be incorrect. I had a 2001 GT 5spd car that I had driven quite hard in stock form and in full bolt on form.

2001 GT mods:
JLT CAI
Professional Products 70mm TB and Plenum
BBK LT Headers
BBK Offroad H-pipe
Magnaflow Magnapacks
Fidanza Lightweight Flywheel
FRPP King Cobra Clutch 10.5"
TKO500 Trans
FRPP Aluminum DS
Diablo Sport Tune

I do remember the way it felt when I installed the FW and the DS and the car had a bit more git'up and around town driving was improved immensely.

With all of these modifications the car had a very crisp feel, the pedal feel was very direct to what I was putting through the rear tires. I could literally use my right foot and start wheel spin as soon as I wanted, drifting/powersliding had a very organic feel, I could place the car where I wanted. *sigh* I miss that car too.

anyhoo :ford:

http://vid105.photobucket.com/albums/m238/igjoe2007/lts.mp4

 

[Trackaholic]

I think the flywheel definitely can improve throttle response. One huge item not mentioned in your list is rotating inertia. Lowering the inertia will have an effect because the engine can accelerate more quickly for a given torque. Therefore lowering inertia will have the same effect as changing the throttle mapping.

Maybe the difference is what one considers to be part of throttle response. For me, and the purposes of a quick, rev-matched downshift, throttle response encompasses both the time it takes for the engine to begin changing speeds when you step on the gas, as well as the time it takes to reach the desired RPM. So, rather than defining it as when the engine begins to rev, I would define it as when the engine finishes, as that is what is important. Therefore you have the throttle mapping, air path, and rotating inertia to consider.

-T

 

[Grimace427]

I suppose it's semantics. But, I understand what you're saying.

Yeah I'm not about to go around yelling at people that they're saying it wrong. I spend a lot of time explaining auto tech stuff to non-car people here at work so I try to make things as clear as possible.

Aha, that makes sense, so what's the proper terminology that EiB and I should be using? Drivetrain response? Sounds a little too all-encompassing.

That is actually how I think of it. Among upgrades to drivetrain response(including driveshaft and flywheel) would be the differential as it can improve power transfer to the ground and improve response from pressing the throttle to actually accelerating the car(especially out of a corner).

I think the flywheel definitely can improve throttle response. One huge item not mentioned in your list is rotating inertia. Lowering the inertia will have an effect because the engine can accelerate more quickly for a given torque. Therefore lowering inertia will have the same effect as changing the throttle mapping.

Maybe the difference is what one considers to be part of throttle response. For me, and the purposes of a quick, rev-matched downshift, throttle response encompasses both the time it takes for the engine to begin changing speeds when you step on the gas, as well as the time it takes to reach the desired RPM. So, rather than defining it as when the engine begins to rev, I would define it as when the engine finishes, as that is what is important. Therefore you have the throttle mapping, air path, and rotating inertia to consider.

-T

I know the feeling you are talking about, but I don't call that throttle response because even with a super light flywheel if your throttle pedal tune is lazy you will still feel a lazy throttle response. Likewise if the engine has a super long intake track with a restrictive airbox or whatever, there will still be lag from pressing the throttle pedal to when the engine finally starts to rev. Other examples include turbo cars which even with a lightweight flywheel when they are under load at low RPM's and out of boost the throttle feels very lazy(IMO).

Like EiBStudent said it's really semantics and I don't mean to argue with anyone. Just my thoughts on the matter. My current datalogged Steeda tune has a wicked throttle response and I love it!

 

[EiBStudent]

The stock response of my previous 3 valve S197 was one of my only complaints about the car...it was very lazy at times.


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[AlphalphaMale]

I believe they upped it to 123 or something like that. I do remember it's no longer 115 for the V6, but as others have said it's been posted.

Edit: Found it it's now 121

Why that low, I wonder? My 2013 370Z is limited also, but to 155.

 

[1stWorldMustang]

2015 Mustang 2.3L TurboCharged EcoBoost Up Close …: looking at this body style makes me think of top speed runs :-)

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