Lightweight flywheels

[spetz]

So, is it worth getting?

Does it make the car quicker? Or just more responsive and stuff?

Does it make the car slower at higher speeds?

[SKREMN]

more acceleration
is worth getting
depending how light you go it can make it harder / less comfort on takeoff
want make car slower
yes more responsive and stuff

[sivic]

yeah go it. just got a toda one installed. the main benefit is the response.
as far as acceleration goes i found 3rd benefits the most (engine is ZC).
combined with a HD clutch its fun

[DC5TYPER]

Well being light in weight it should really make the driveline more effecient.
Meaning accelearation will increase because less resistance in the gearbox area and you'll get power to the ground quicker.

[Slow96GSR]

Having a lightweight flywheel is good for drag racing, not so great for street courses or auto-x. We tend to use the 11-14lbs chromoly. See if it's too light it will spin up fast but also drop in speed fast too. You have to find a mid point. You want to get up to speed/rpms fast but you want the rpm drop off to only be 4-5krpms. Lets say the power curve starts at about 1500rpm and starts to drop off at 7krpm, the max rpms for this car is 9k and the drop off (When you push the clutch in and change gears) is 5k with the chromoly and 6-6500 with aluminum. The chromoly would be the best because the motor would drop to 3krpms (If you shift at 8krpm to take full advantage of the power curve) and the power curve would just be started vs. the 1000-1500rpms lower on the curve. Dropping all the way will take you longer to speed up. We find that the faster you can get you rpms up the fast you are in the ¼ mile. This means, hopefully, more wins, especially drag racing. In our formula cars we used a stock, if that's what you could call it, flywheel. Cast steel more or less. In the drag cars we use the chromoly, and street applications we use the stock ones or the chromoly. Aluminum tends to be to worst choice but whether that’s driver error or just too much power to safely run it I don’t know. It's going to depend on what you are building the car for.

Here's a pic I have of a Teg....
http://www.strathlan.com/TEK/images/powercurve.jpg

[Chris_F]

i just had a hd clutch and 4.7kg chromoly flywheel installed on my euro and i'm very happy with it. theres a difference in accleration especially in the first few gears and generally the car simply feels lighter and more eager to rev.

listen to Slow96GSR, everything he says is true - you need something that will suit your particular application. so far the 4.7kg job has been great for my euro :thumbsup:

[spetz]

Yeah I was thinking of putting a 4.5kg flywheel on the car.

I understand the revs will also drop quicker but does that matter? In a drag race the shifts would be so quick they wouldn't have time to drop off enough?

Chris F, were there any negative effects of putting the flywheel on?


And someone told me, a lightweight flywheel will make the car quicker to a point and then in the top end it will suffer?


Also, as a guesstimate, if a car does 14 flat down the quarter, how much quicker will it be roughly with a few kg off the flywheel?


Is it ok to remove weight from the standard flywheel?

[aaronng]

Don't remove weight from your stock flywheel. It makes it structurally weaker. Go for chromoly. I've read that aluminium flywheels can fail easily.

[spetz]

Any negative effects of putting a lightweight flywheel??

Is 4.5kg ok, too light?

[chunky]

Having a lightweight flywheel is good for drag racing, not so great for street courses or auto-x. We tend to use the 11-14lbs chromoly. See if it's too light it will spin up fast but also drop in speed fast too. You have to find a mid point. You want to get up to speed/rpms fast but you want the rpm drop off to only be 4-5krpms. Lets say the power curve starts at about 1500rpm and starts to drop off at 7krpm, the max rpms for this car is 9k and the drop off (When you push the clutch in and change gears) is 5k with the chromoly and 6-6500 with aluminum. The chromoly would be the best because the motor would drop to 3krpms (If you shift at 8krpm to take full advantage of the power curve) and the power curve would just be started vs. the 1000-1500rpms lower on the curve. Dropping all the way will take you longer to speed up. We find that the faster you can get you rpms up the fast you are in the ¼ mile. This means, hopefully, more wins, especially drag racing. In our formula cars we used a stock, if that's what you could call it, flywheel. Cast steel more or less. In the drag cars we use the chromoly, and street applications we use the stock ones or the chromoly. Aluminum tends to be to worst choice but whether that’s driver error or just too much power to safely run it I don’t know. It's going to depend on what you are building the car for.

Here's a pic I have of a Teg....
http://www.strathlan.com/TEK/images/powercurve.jpg

[aaronng]

Having a lightweight flywheel is good for drag racing, not so great for street courses or auto-x. We tend to use the 11-14lbs chromoly. See if it's too light it will spin up fast but also drop in speed fast too. You have to find a mid point. You want to get up to speed/rpms fast but you want the rpm drop off to only be 4-5krpms. Lets say the power curve starts at about 1500rpm and starts to drop off at 7krpm, the max rpms for this car is 9k and the drop off (When you push the clutch in and change gears) is 5k with the chromoly and 6-6500 with aluminum. The chromoly would be the best because the motor would drop to 3krpms (If you shift at 8krpm to take full advantage of the power curve) and the power curve would just be started vs. the 1000-1500rpms lower on the curve. Dropping all the way will take you longer to speed up.
Doesn't the amount of RPM drop depend on your road speed when you release the clutch in the next gear and not on the flywheel? The flywheel determines how fast the RPM drops, but the number of RPM dropped after shifting gears.

[Slow96GSR]

Doesn't the amount of RPM drop depend on your road speed when you release the clutch in the next gear and not on the flywheel? The flywheel determines how fast the RPM drops, but the number of RPM dropped after shifting gears.

There are many determining factors but rotating mass makes up the most. Once you release the clutch the road speed doesn't matter since the input shaft no longer connects the transmission and the motor. The tranny is now freely spinning with the wheels. The motor will drop in rpms now that there is no load. I was just using those numbers as an example. It will vary depending on the gear ratios and the rest of the parts. If you could shift perfectly and as fast as possible then the drop off wouldn't matter. But since 99% of drivers can't, you have to build the car to them not to a perfect driver. This is why you want the drop off to be slow and make it easier on the car and the driver.

Also road speed is set by rpm, wheel size and time. So the same car with 22" tires will have lower rpms than a car with 20" tires. It takes more rpms to move a smaller tire. It has to spin more times to keep up with a bigger tire, thus this will also affect the outcome.

Sorry this is gonna be long, but might as well make 1 post not 2-3!!

Formula for MPH
MPH = TIRE DIA. ÷ 336 X ENGINE RPM ÷ GEAR RATIO

Example: What MPH at 6500 RPM with a 4.9 rear axle and 28 inch diameter tire in 4th (1:1) gear?

MPH = 28 ÷ 336 x 6500 ÷ 4.90 ÷ 1 = 111 MPH

Example: in 3rd gear (1.34)?

MPH = 28 ÷ 336 x 6500 ÷ 4.90 ÷ 1.34 = 83 MPH

Note: Tire Radius is distance, in inches, from center of wheel to the top of the tire.
Note: Gear Ratio is Rear Axle ratio divided by Transmission Gear ratio.

Formula for RPM
RPM = 336 X GEAR RATIO X MPH ÷ TIRE DIAMETER

Example: Using the first example, what will be the RPM after shift from 3rd to 4th gear at 83 MPH?

RPM = 336 x 4.90 x 83 ÷ 28 = 4880 RPM

Note on Tire Diameter:
Tire diameter is measured on an unloaded tire. For best accuracy, measure tire roll-out and divide by 3.14.

Formula for Gear Ratio
GEAR RATIO = TIRE DIAMETER X RPM ÷ 336 ÷ MPH

Example: Using the first example, what Gear Ratio is required for 120 MPH at 6500 RPM?

GR = 28 x 6500 ÷ 336 ÷ 120 = 4.51

Formula for Tire Diameter
TIRE DIAMETER = 336 X MPH X GEAR RATIO ÷ RPM

Example: Using the first example, what tire diameter for 110 MPH but at 6000 RPM with a 4.11 gear?

336 x 110 x 4.11 ÷ 6000 = 25.4 inches

Note: Approximately a 25" diameter tire. Remember that the tire diameter will be less during hard acceleration than when the vehicle is standing still. Also, diameter will be greater at high speed due to tire expansion from centrifugal force.

Formula for HPQ
HPq = (0.00426 x MPH)3 x WEIGHT

HPq = Engine horsepower required to reach MPH in quarter mile

Note: understates HP required at speeds exceeding 100 MPH.

Note: assumes engine HP must be 2 x the HP required at drive wheels.

Example: What engine HP is required to achieve 110 MPH in a 3200 pound vehicle in 1/4 mile?

HPq = (0.00426 x 110) x (0.00426 x 110) x (0.00426 x 110) x3200 = 329 engine HP

Formula for HP and Torque
HP = TORQUE X RPM ÷ 5252 • TORQUE = HP X 5252 ÷ RPM

Example: What torque is required to generate 329 HP at 6000 RPM?

T = 329 x 5252 ÷ 6000 = 288 foot pounds @ 6000 RPM

Example: What torque is required for 296 HP at 4880 RPM?

T = 296 x 5252 ÷ 4880 = 319 foot pounds @ 4880

Here too! (http://www.edelbrock.com/automotive/sport_compact/index.html)

[aaronng]

Thanks for your explanation. What I was thinking was that for 2 identical cars, one with a standard flywheel and one with a lightweight flywheel, if both drivers shifted from 1st to 2nd equally fast, wouldn't the resulting RPM in 2nd when they release the clutch pedal be the same for both cars?

[Chris_F]

Chris F, were there any negative effects of putting the flywheel on?


i haven't really noticed any negative side affects. 4.7kg could be said to be on the "heavier" side of lightweight flywheels as some manafacturers make it as low as 3.5kg and this is a genuine honda item from the jdm DC5R so i trust it.

all i notice is that the car now revs more freely, no real obviously negative side affects to report. But if ppl put on a really really light 3kg flywheel the affects will be more drastic good or bad, i dont know.

[bennjamin]

I recently installed a TODA 3.5ish KG flywheel on my totally stock eg5 (d16a8) - and can report it is a good mod. Only really worthwhile if installing a new clutch at the same time (saving the $300ish on labour to install another time).

Otherwise , normal driving is ofcourse affected - car needs more revs and more clutch slip to get off the line in normal driving and engine braking is reduced - but in "spirited driving" this hidden mod shines :) Response is increased and car seems to be more lively and nippy. IMO , its one of the best mods to do to a 1.6 or smallish capacity engine. Think of it as changing your 18 inch wheels for lightweight 15's or 14's :)