[scathing]

I had the JUN Flywheel I picked up from Z350Lover installed on Thursday, and I did some not-scientific testing runs with it.

In a nutshell, I drove the car up the motorway, got the car in-gear and at the start speed, and then used the stopwatch in the car to measure. Not particularly accurate, but I did it a few times to get an average

From 40-80km/hr in 2nd, with the stock flywheel in my car's setup I ran back to back 3.17s.

With the new flywheel, it blew out to 3.4s or so. I even made an extra couple of runs to make sure I wasn't fucking it up, but the were all hovering well above the non-flywheel time.

I also did 3rd gear pulls from 80-120km/hr. With the stock flywheel I was averaging around 4.5s. With the lightened flywheel, we're looking at 4.1s.


So it appears to be better for in-gear acceleration at higher speed (I'll have to give standing start a go, but I never measured myself doing a standing start pre-flywheel since I can't guarantee keeping my shifts constant) but, at lower speeds, its a penalty.


As for drivability, its not bad. The car isn't any harder to launch. One thing I noticed is that, with the stock flywheel, when I lift off the throttle and hit the clutch the revs will increase for a second before dropping, whereas with the JUN it stays constant a little before dropping.

Unsurprisingly, its ability to pull up hills is compromised. I used to drive my car low in the rev range, and in places where I used to keep it in 6th I find myself now having to find 5th.

There are rattles, but I'm not sure if some of them are install-related or not. I'll take it back to them and have a look, and if they can't fix it after 1-2 goes I'll be paying Nizmo Pete a visit.


Since I don't commute as much in my car anymore (and I'm considering buying an old banger for the times I do), and I would like to start focusing on doing track work i don't think it'll be an issue. Given the drivability of the 14lb 'wheel, I'm starting to think that maybe the 7lb Tilton one isn't too light

 

[davidm]

As for drivability, its not bad. The car isn't any harder to launch. One thing I noticed is that, with the stock flywheel, when I lift off the throttle and hit the clutch the revs will increase for a second before dropping, whereas with the JUN it stays constant a little before dropping.

Are you saying that launching in a day-to-day is not any harder compared to OME? That is what interests me the most - how difficult is the car to get off the line in your every-day-normal-start (ie. nothing agressive). I know that the Jun flywheel is awesome once you're actually on the move, but in Richie's car it needed good 2000 - 2500rpm clutch-slip to get off the line in order not to stall. Though, not sure how much of it was due to the tuning/cams and how much was the flywheel. I would have not thought that the flywheel could make a difference in this regard.

So it appears to be better for in-gear acceleration at higher speed.

I don't think that flywheel will make any difference to the acceleration (one way or the other). It only influences how the car feels when the engine is not engaged to the driving-wheels (ie. in neutral). Afterall, the Jun flywheel drops around 6kg from the OME flywheel/clutch assembly which weights around 25kg OME. That's less than 25% saving in rotaing mass in here and when you add all the other parts that spin in the engine I'm not sure if this 6kg will account for 5% of difference in weight.

Generaly speaking flywheels are changed in the car to match them with driving style and gear-box, but not to improve actual performance (except for quicker gearchanges of course).

So maybe I'm not seeing the whole picture, but how would the weight of a flywheel influence the acceleration?

Not particularly accurate, but I did it a few times to get an average

You know what would help you make this more acccurate? Don't go by speed. Start at certain revs and then either go to the limiter (which is the easiest), or set your shift-light at desired revs where you'd like to stop.

Also it would help if you had someone in the car to do the actual timing as all they need to do is watch the revs/shift-light while you can concentrate on driving. If you always use the same person then you should get consistent results.

 

[Nuff]

Scathing, did you also make sure that you had the same amount of fuel? As in full vs empty. I can definitely feel a difference between full and empty tank, mostly when driving away from service station after filling up 65-70l of petrol.

As for tilton, there's a huge difference, you are forgetting the weight of the clutch, the size of the clutch and the weight distribution in the flywheel (and previously mentioned clutch). I think the next step down in weight is ATS which is still easy to drive, it's 4.5 kg flywheel, with 9" clutch compared to 11" OEM clutch. The clutch and flywheel assembly weights for twin plate weights 11.6kg and 12.8kg. OEM flywheel weights 12.6kg and with clutch it weights 20.5kg. Your JUN flywheel and clutch weights at 14.3kg.

David, as for rotational mass reduction it makes a lot more difference in kg per kg then non-rotational. I've read some place that removing 1kg of rotational mass is equivalent to removing 5kg (this number could be wrong, it might have been higher). It also makes a bigger difference the higher RPM you are dealing with. Since it takes a lot more energy to spin more mass. This is why lightweight pulley works and this is why flywheel change will make a lot more difference. There is a lot less power loss and you get more power to the wheels. Another point to remember that a 350z with tilton flywheel can keep up with supercharged 350z. It makes a lot of difference in acceleration. As for the % of total spinning mass you have calculated. You have to remember that not all rotational mass is equal. The further away the mass is, the more impact it has.

 

[scathing]

My launch technique hasn't changed. I was really concentrating on it for the first 1-2 starts, but I found it to be no different. I still take off at around 1000-1200RPM on a sedate start.

Its a trifle late to do pre- and post-install tests now. I was a bit rushed this week getting everything sorted, so I only did the pre-install runs just before the car went to the mechanic's.

Most of what I read says that a car will accelerate faster with a lightened flywheel on the flats or downhill, but its only uphill where the lack of inertia catches it out. I think it accelerates harder in gear from what I'm feeling, but it could be psychosomatic in some cases.

The best "feel" I get from the flywheel is when I double clutch from 3rd to 2nd. The engine blips a lot quicker and harder, so it makes it easier to slot it into 2nd when barreling towards a tight corner.

I went through the Royal National Park and Macquarie Pass tonight, and while the car went well through the RNP it did feel a little less powerful hillclimbing up the Pass. Since I had less time to concentrate on the flywheel "feel", among avoiding Skylines through RNP, and trees / cliff walls up the Pass, its probably a bit more accurate.

 

[scathing]

Originally posted by Nuff@May 14 2005, 03:30 AM
Scathing, did you also make sure that you had the same amount of fuel? As in full vs empty. I can definitely feel a difference between full and empty tank, mostly when driving away from service station after filling up 65-70l of petrol.

Yep. Full-tank runs each time, from the same servo, and the same route from the servo to where I was testing. There'll only be a few mL in it between days. I also did it at approximately the same time, and according to the car's ambient temp gauge both runs were done at 13 degrees.

 

[ky350]

Originally posted by Nuff@May 14 2005, 03:30 AM
Another point to remember that a 350z with tilton flywheel can keep up with supercharged 350z.

Nuff - this sound very unrealistic. How can a stock 350Z with lightweight Tilton flywheel keep up with a supercharged 350Z?
Considering that a supercharged 350Z puts out 220kW ATW and a stock Z 150kW ATW, then we can assume that a Tilton flywheel adds about 70kW due to its lighter weight and inertia benefits - now way never.

 

[Nuff]

[/quote]


Don't ask me about the details, talk to Jason from Performance Nissan, he has it on his car and that's what he and other's have said. It's his quote, and few other's have said the same thing. the thing is tilton doesn't add 70kw, it's more like reducing the weight of the car. Also with superchargers the boost comes in later in the rev-range, where as the flywheel makes a difference through out the revrange.

But the supercharger is better when it comes to ease of driving, noise and you can increase boost for more power. Also the Tilton Zed had exhaust, intake, pulley wheels, tires few other things as well. So the tilton Zed has around 165kW atw.

 

[ky350]

Nuff - I realise that the FW does not add 70kW and I appreciate that its considerably lower mass will result in less mechanical deficiency than the stock Z's FW, making it much more responsive and also fater.
Even with 165kW onboard Jason's Z, there has still got to be 50kW surplus on the supercharged Z and even this is too big a disadvantage for the FW to overcome.
Never the less, you've sparked my interest and I will do a search on the old site for more info on this, when I get some spare time.

 

[scathing]

Originally posted by scathing@May 13 2005, 09:39 PM
There are rattles, but I'm not sure if some of them are install-related or not. I'll take it back to them and have a look

Just took the car back today. We tightened some stuff (which seemed tight already) and reseated the new pads / rotors, and its all good.


Its the first time I've taken my car to Pro Concept, and I'm quite happy with Joshua's work. He's also looking at installing a Power Enterprise Twin Turbo kit in the future, and he'll let me know how that goes.

 

[db350z]

so the rattle still there?

 

[scathing]

Well, the flywheel rattle is there. The hollow clunking noise I was getting when hitting bumps with my passenger-side front wheel (which is the rattling I was mentioning I wanted to fix) is gone.

The chatter is a given for a single-mass flywheel. Especially when you try giving it throttle under 2000RPM, its loud. Once you clear that, it just adds a slightly metallic and angrier noise to the drivetrain. I think it sounds good, actually, especially at full throttle next to a cliff wall in 3rd.

In terms of effect, it reminds me of the HiTech over the stock exhaust. A little louder, more metallic, and a little angrier, but its not overbearing and it adds to the experience rather than detracting from its commutability.

 

[mchapman]

Good to hear you like it.

 

[Z350Lover]

Alan,

Good to know that you enjoy it as much as I did with the JUN piece... I really loved it...

A bit of chatter noise = You are driving a tuned up car... that's what most of the people think about!

cheers,

richie