I Want My Skyline To Rev

[J_Red33]

This is turning into a rather interesting thread, though I have to say from reading so far that I'd have to agree largely with Roy on his idea's on how to get the response levels up.

Carbonfibre tailshafts are something you do when all the fundamental stuff has already been covered & you have money to burn. You will get a lot more for your 2k spending it on other parts like the flywheel & powerfc.

Also I'd have to say that not enough emphasis has been put on changing the intercooler, everyone I know that has put a front mount on their car has noticed a massive increase in response.

The stock 33's intercooler is very restrictive & from the many threads I've read is only good for about 200KW anyway.

By changing to a larger aftermarket cooler the engine will get a cooler air charge & it will also be there a lot faster. Engines have to breathe just like humans do, have you ever tried running around the block with your nose pegged & a straw stuck in your mouth to breathe through? You'll find you can't go as fast because of the restriction of air that you can breathe.

[scathing]

So you're saying that a front mount, with its greater restriction due to the larger core size (for the purpose of this comparison we'll say that a unit length of core between the OEM 'cooler and the aftermarket one is just as restrictive to airflow), and its increased plumbing length, is more responsive than the OEM side mount?

Interesting......

[jeffworld2]

i agree, front mounts are NOT restrictive at all, just pipe length is longer. I found running 7psi in r33 stock turbo is the same (in terms of lag) as with my frontmount on and running 10psi. I have full exhaust mods, so the thing actually slowing me down seems to have been the tiny stock intercooler. Now i get more power and boost up to it in the same/similar time.

I dont beleive pipe length is truly as big a deal as its made out to be, although its obvious it must have an effect.

[rev210]

This is turning into a rather interesting thread, though I have to say from reading so far that I'd have to agree largely with Roy on his idea's on how to get the response levels up.

Carbonfibre tailshafts are something you do when all the fundamental stuff has already been covered & you have money to burn. You will get a lot more for your 2k spending it on other parts like the flywheel & powerfc.

Also I'd have to say that not enough emphasis has been put on changing the intercooler, everyone I know that has put a front mount on their car has noticed a massive increase in response.

The stock 33's intercooler is very restrictive & from the many threads I've read is only good for about 200KW anyway.

By changing to a larger aftermarket cooler the engine will get a cooler air charge & it will also be there a lot faster. Engines have to breathe just like humans do, have you ever tried running around the block with your nose pegged & a straw stuck in your mouth to breathe through? You'll find you can't go as fast because of the restriction of air that you can breathe.

Hi not wanting to make things more complicated here but, just a small point of order on the tailshaft.

The carbon fibre tail shaft is a 'Good Value' modification and one that can be done at any time. The performance increase is very significant.

In this case where a person is aiming at response and a relatively low power street vehicle it makes very good sense.

Going back to the earlier example of the Z06 I mentioned and adding a bit more info.

On the same dyno. A 437rwhp / 376ftlb Z06 accelerated from 2,500rpm to 6500rpm (145mph) in 9 seconds with the factory flywheel /clutch setup.

By losing 10kg of rotational mass the time dropped to only 8 seconds.

Comparing this to the stockish Z06 ,on page 3 othis thread, shows us that a difference of 80rwhp accounts for a difference of 5 seconds when the heavy factory flywheels are in both cars. The difference drops to only 2 seconds when the stockish car has the lightweight kit installed.

So it's close to an equivalent 36rwkw extra that the stockish Z06 has gained by dropping about 10kg of rotational mass. The added point is this is under full load in 4th. Lightening rotational mass has actually greater gains in lower gears.

The benifit of going from 200rwkw on a tuned stock turbo to 236rwkw is big fat turbo upgrade territory in terms of acceleration. BUT:

* You don't have extra lag that a larger turbo always has.

* You acelerate faster off boost as well

* You have better deceleration potential due to reduced inertia

* Better fuel economy

And so on...

Now lets look at the real cost of the 'responsive' 230rwkw turbo upgrade.

I need :

HKS 2530 Turbo $2k

Bigger fuel pump $300

Larger injectors $900

Oil lines/gaskets etc $300

A dyno retune $300

Total = $3,800 (granted if you are a miserly tight ass you can find things a touch cheaper here and there but, I didn't include someone fitting it for you which adds more to the total).

Something to consider.

The R34 side mount intercooler is a good choice upto 230rwkw by the way.

[scathing]

I don't think a lighter flywheel gives you better economy. Its worse, if anything.

I'm running a flywheel that's have the weight of OEM. Because I now have to drop down a gear to go up hills I could ignore the shifter in previously, and I'm having to rev the engine harder from a standstill to stay on-torque, my economy has suffered.

[discopotato03]

Gets warm in here . IMO lightened std flywheel and if real keen low innertia clutch .

If someone can get 270 odd Kw from the usual GTR cooler/port job/cams/exhaust/PFC/GCG Hi Flow/pump and injectors this is great bang for buck . Would also have no trouble selling the thing when tired of it .

[Abo Bob]

This is turning into a rather interesting thread, though I have to say from reading so far that I'd have to agree largely with Roy on his idea's on how to get the response levels up.

Carbonfibre tailshafts are something you do when all the fundamental stuff has already been covered & you have money to burn. You will get a lot more for your 2k spending it on other parts like the flywheel & powerfc.

Also I'd have to say that not enough emphasis has been put on changing the intercooler, everyone I know that has put a front mount on their car has noticed a massive increase in response.

The stock 33's intercooler is very restrictive & from the many threads I've read is only good for about 200KW anyway.

By changing to a larger aftermarket cooler the engine will get a cooler air charge & it will also be there a lot faster. Engines have to breathe just like humans do, have you ever tried running around the block with your nose pegged & a straw stuck in your mouth to breathe through? You'll find you can't go as fast because of the restriction of air that you can breathe.

Yes from a shaky start it's done well. (the thread that is)

I have to take a point with:

"everyone I know that has put a front mount on their car has noticed a massive increase in response."

You can't be serious. Response is the one thing you lose with a front mount upgrade. I'm not talking about lag here.

Also, the R34 sidemount is significantly bigger than the R33 one and until you've experienced it you wont understand. Plenty of things between R33 and R34 are practically the same but this is not one of them.

As response is the subject of the thread I would strongly recommend keeping the stock cooler but would of course add the usual warnings about heat soak. You might find it worth while to have a temp probe, gauge and maybe a warning light for after cooler temp so that you can see when it has stopped being effective.

Interesting to hear about the economy Scathing.

[r33_racer]

less rotating mass, means revs drop off faster then usual...when you back off for a second (std flywheel) the moving mass takes longer to slow down then a lightened one, so your at a benefit of being at a higher rpm when your back on the gas. Thats the way i understood it anyway.

[Abo Bob]

I had a very long convo with SK one day in the street about weight reduction (not talking about response here). Basically he had just spent 7 or 8 grand on some weight reduction to gain 0.2 seconds a lap on a racetrack. His opinion was that for sprints, fun, club days, street, etc, it was not in the slightest bit worth it but on a 20 lap race 0.2 per lap is 4 seconds and that might be enough to win it.

Regarding this post; it was suspension components and yes it's a track GTR but not sure what other weight saving mods were done because I think there are some restrictions in the class they run in.

[Abo Bob]

less rotating mass, means revs drop off faster then usual...when you back off for a second (std flywheel) the moving mass takes longer to slow down then a lightened one, so your at a benefit of being at a higher rpm when your back on the gas. Thats the way i understood it anyway.

Are you referring to fuel economy?

[rev210]

I don't think a lighter flywheel gives you better economy. Its worse, if anything.

I'm running a flywheel that's have the weight of OEM. Because I now have to drop down a gear to go up hills I could ignore the shifter in previously, and I'm having to rev the engine harder from a standstill to stay on-torque, my economy has suffered.

I have had a different experience to you, with plenty of other cars too.

Interesting you say the economy has suffered however. I drove my old car (r33 gtst) a good few kms (work vehicle with log books) I was getting 10L/100km or better. I had the car 3 or so years and drove it a good 30,000kms a year or so. I checked this on the log book records I have and I didn't get any penalty of fuel eccomomy at all. In fact the fuel ecconomy is better afterwards but, I'm reluctant to say thats conclusive proof. Although it's probably better proof than anyone else probably has on this forum it's not really a dedicated test. I think you might have an issue with the kind of clutch pressure plate you are using.

It was a 4.8kg Ogura flywheel, 8 puck ceramic sprung clutch plate and factory stock pressure plate for the record. I never had to rev the car any harder than stock to get off the line or start on a hill, it felt just as friendly as stock. 4.8kgs is not really so drastic with a 2.5L six.

The problem most people have with lightweight flywheels and stalling the car is due to a nasty clutch setup installed at the same time. Usually the pressure plate is over the top in terms of being sprung too heavy causing a much reduced friction point. It becomes more an 'on' or 'off' proposition and means slipping the clutch without chatter means more revs. It may suprise people to know that the stock pressure plate force is more than enough to work with a fairly decent power increase when matched to a good friction plate. If you are suffering from an over developed left leg and you are driving around in a street car you have probably got the wrong clutch in there. If you do have a bit of power with this issue, twin and tripple plate clutches were made for you. The good ones are lovely to drive with (although some make a bit of a rattle noise).

[mokompri]

less rotating mass, means revs drop off faster then usual...when you back off for a second (std flywheel) the moving mass takes longer to slow down then a lightened one, so your at a benefit of being at a higher rpm when your back on the gas. Thats the way i understood it anyway.

this is where a lighter tailshaft has some advantages over a lightened flywheel. on gear change when you pop it into neutral, with a lightened flywheel revs will drop faster relative to a heavier flywheel as there is less inertial mass attached to the engine, but the tailshaft is no longer part of this inertial mass because its after the clutch and its now disconnected from the engine, so between gear changes it will not cause a faster drop in revs.

the same effect occurs with lighter wheels, its inertial mass after the clutch. its too bad the lightened flywheel is the cheapest option !

[shonen]

hmm not sure if this point has been covered yet..but dont lightend flywheels give slower acceleration/response uphill ?

If this guy really is building it for the mountain pass than there will no doubt be plenty of uphills and downhills in his path..

Oh and if you wanna spend $2k on your car get an aftermarket launch/traction control system fitted, some of them come with the option of "flat shift" and will no doubt help in acceleration and make the car more responsive overall.

Edited November 20, 2006 by shonen

[Abo Bob]

Well I think that's what scathing is saying but rev210 disagrees.

[rev210]

hmm not sure if this point has been covered yet..but dont lightend flywheels give slower acceleration/response uphill ?

If this guy really is building it for the mountain pass than there will no doubt be plenty of uphills and downhills in his path..

Oh and if you wanna spend $2k on your car get an aftermarket launch/traction control system fitted, some of them come with the option of "flat shift" and will no doubt help in acceleration and make the car more responsive overall.

No.To understand that one in a measured way refer to the Z06 example, that is under load in 4th just like going up a hill. The lighter flywheel is quicker. If you were in lower gears its faster again.

[discopotato03]

The way I read it is that the revolving mass of the flywheel dampens out the power pulses of our multi cylinder piston pump . The advantage of an OEM weight flywheel is that the engine is less likely to drop revs and stall when the clutch takes up from a standing start , thats to say that the innertia or energy stored in this flywheel only has to move the weight of the car divided by its overall lowest gear ratio and not let the engine revs drop below sustainable running speed . Once your moving the disadvantage is that the load on an accelerating engine is higher just accelerating the greater flywheel mass . You may think yeah right but its this beating the innertia ie accelerating the cars weight plus all of the engines and drive lines reciprocating and revolving mass is what acceleration of the vehicle is all about - gravity and air drag aside .

The lightened flywheel advantage is highest in the lowest gear and drops away as you step up the gears to a degree and this is because the car becomes effectively heavier as you pull each gear (less mechanical advantage through gearbox reduction) .

There are other advantages of lower mass flywheels like as was mentioned engine revs drop much faster when de clutched because there is no extra flywheel innertia to hold the revs up there . All manual gearboxes really like this scenerio - particularly production like wide ratios - because when engine revs drop like a brick between gears you stand a FAR better chance of picking up the next "cog" . Its not well known that syncro baulk rings have a very hard time trying to SLOW down the input side of the box and driven plate when changing up from high revs . You can (and every rev heads been here) have an impossible time trying to grab 2nd gear if you've reved your car as far as it will go in 1st and attempt to slam 2nd . Very often won't go in or if it did not too many more times . Generally the cause of the infamous buggered 2nd syncros . Lightening the flywheel very much helps this situation and I guess you could say that the quick rev on the down change needs less fuel energy for faster engine speed transients .

I reckon for the extra couple of hundred revs you may need above idle to get the beast rolling its money well spent . Anything that sharpens up engine response to accelerator pedal inputs is a large bonus .

Nuther 2c spent , cheers A .

[-_-StRyDeR-_-]

if you dont want lag then buy a v8. and dont waste 15k. if u wanna get rid of the 15k il give u my bank details!

crazy thread.

[rev210]

if you dont want lag then buy a v8. and dont waste 15k. if u wanna get rid of the 15k il give u my bank details!

crazy thread.

You forgot this part tho'

"....and if you don't want a V8 buy a gun and end it all!"

I hope you weren't thinking small block V8 buddy. Because anything less than 426 cubic inches is a toy.

[scathing]

the moving mass takes longer to slow down then a lightened one, so your at a benefit of being at a higher rpm when your back on the gas. Thats the way i understood it anyway.

That's true. The revs fall quicker, so you're not waiting as long to rev match when you're shifting up. And, when downshifting, the engine flares a lot easier when you give it a blip on heel-toe.

I did some in-gear acceleration runs before and after (same stretch of road, same amount of fuel in the tank, same weather). Ease the throttle in to load the car up to hold the minimum speed, and then floor it. I was using a hand stopwatch, but I did about 3-4 runs each and averaged the times out.

In 2nd gear from 40-80 my acceleration times were slower after the flywheel. In 3rd gear from 80-120km/hr my acceleration times were higher. I was so surprised at the results of second gear that I did it twice (so 6 runs) - couldn't even match my old times.

Still, it definitely does make the engine more responsive. I'm running a stock clutch so the feel is no different. I'll occasionally stall, but unless you were told you'd have no idea by launching it that the flywheel wasn't factory. I let a mate with another Z drive my car, and he only noticed something was different when heel-toeing. He probably didn't notice the acceleration difference since he's come out of a supercharged one.

As for economy, on the motorway when I'm driving interstate the economy is about equal. But, around town, the economy is a little worse. Some 6th gear hills are now 5th gear. I have to shift at 2500RPM instead of 2000RPM.

Economy loss or not its still worth it, but if I could do it again I'd buy an 8lb flywheel (I've got a 14lb one in there at the moment, and the OEM is around 28lb). The current one is so user friendly it may as well be stock, so I want something faster.

[scathing]

hmm not sure if this point has been covered yet..but dont lightend flywheels give slower acceleration/response uphill ?

Only low in the rev range, to my notice, and only when you're cruising. If I'm pootling around in 6th gear at 60km/hr, there are some hills where the OEM flywheel could get up the hill without lugging the engine in that gear. These days, I have to use 5th.

For example, if you drive north up the Pacific Highway from the shops at Lindfield on the North Shore. That's no longer a 6th gear at 65km/hr hill. I need 5th, or 80km/hr, to stay in 6th without having to use a lot of throttle.

But, if I'm on the Old Pac I honestly don't notice the missing torque when I'm WOT going up the hill. And the dyno graphs are pretty much no different on power runs before and after the install.

If we can keep the engine in the torque band and you're constantly on the throttle, its not an issue. Its only when you fall off the torque curve that the lightened flywheel starts being a penalty....but then unless you're in 1st you can just downshift and get back up into the revs.