Lightweight flywheel from a mpg standpoint - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Lazarey · 11-09-2010, 09:05 AM

Considering putting a lightweight flywheel on my strictly DD S14 when I put in a new clutch. I know it's odd but I actually enjoy tracking the gas mileage on it. Over 34 fill ups, I have averaged 28.7 mpg. I was wondering how a lightweight flywheel would affect that. On one hand, it would take less effort for the engine to spin up, but the rpms would fall faster which in my mind could make the engine have to use more gas to catch it before it stalls.

I know there are much smarter people than myself on here, so I thought I'd ask your opinions.

Sileighty_85 · 11-09-2010, 09:40 AM

It should help since your lighting the rotational mass that the engine has to turn.
Frees up power and engergy the engine has to use to rotate it.

I put a Lightweight flywheel on my RB25 and man i can notice a difference as far as revs go especially when it falls back to idle.

Not to sure on the gas mileage yet seeing that i just got the engine running last friday

The way i kinda see it:
Think about throwing a 10lb weight and and a 20lb weight in the air, which is gonna require less energy and force to throw and catch?

Lazarey · 11-09-2010, 10:10 AM

I agree with you on all of that, just wondering if the engine has to use more fuel to catch the engine as it rapidly spins down and if so, how much more...

Hywarp161 · 11-09-2010, 10:27 AM

when i installed a lightweight flywheel in my wife's tiburon she averaged an extra 100 miles to a tank of gas. But if i drive it goes the other way lol. The motor is doing less work to generate the same amount of horsepower.

Sileighty_85 · 11-09-2010, 10:42 AM

Quote:

Originally Posted by Lazarey

I agree with you on all of that, just wondering if the engine has to use more fuel to catch the engine as it rapidly spins down and if so, how much more...

Nah should you less, even though the engine will decel faster it shouldnt have to use as much engery to catch it since it lighter

***S14DB*** · 11-09-2010, 11:06 AM

It should get better hwy mileage cause there is less rotational mass. You may loose some city millage if you do a lot of stop and go. You loose some stored tq(potential energy) in the flywheel for launch. So, it takes a little more gas to get going.

A "street" lightweight will be heavy enough to not take to much gas on the launch. But, still get benefits on cruise. The gains will outweigh the losses.

A "race" weight will be undesirable on launch.

11-09-2010, 09:05 AM	#1
Lazarey Join Date: Jul 2010 Location: Texas Posts: 7 Trader Rating: (0) Feedback Score: 0 reviews	Lightweight flywheel from a mpg standpoint Considering putting a lightweight flywheel on my strictly DD S14 when I put in a new clutch. I know it's odd but I actually enjoy tracking the gas mileage on it. Over 34 fill ups, I have averaged 28.7 mpg. I was wondering how a lightweight flywheel would affect that. On one hand, it would take less effort for the engine to spin up, but the rpms would fall faster which in my mind could make the engine have to use more gas to catch it before it stalls. I know there are much smarter people than myself on here, so I thought I'd ask your opinions.

11-09-2010, 09:40 AM	#2
Sileighty_85 Post Whore! Join Date: Dec 2006 Location: Misawa, Japan Posts: 6,815 Trader Rating: (8) Feedback Score: 8 reviews	It should help since your lighting the rotational mass that the engine has to turn. Frees up power and engergy the engine has to use to rotate it. I put a Lightweight flywheel on my RB25 and man i can notice a difference as far as revs go especially when it falls back to idle. Not to sure on the gas mileage yet seeing that i just got the engine running last friday The way i kinda see it: Think about throwing a 10lb weight and and a 20lb weight in the air, which is gonna require less energy and force to throw and catch? __________________ 後輪駆動車１番 1989 Built SR GT2871R -363whp 1998 S14 W/RB25- 250ish (For Now) 1986 SR86 - 200ish 1990 R32 GTR - 320hp Don't Buy Engines from JDM-Online http://zilvia.net/f/businesses/207457-jdm-online.html Don't Buy XS-Power or SSAC Shit

11-09-2010, 10:27 AM	#4
Hywarp161 Leaky Injector Join Date: Jan 2005 Location: Long Island NY Age: 49 Posts: 105 Trader Rating: (2) Feedback Score: 2 reviews	when i installed a lightweight flywheel in my wife's tiburon she averaged an extra 100 miles to a tank of gas. But if i drive it goes the other way lol. The motor is doing less work to generate the same amount of horsepower. __________________

11-09-2010, 11:06 AM	#6
*S14DB* AFC #1 Join Date: Oct 2003 Location: 昨晩あなたのお母さんの家 Posts: 20,181 Trader Rating: (3) Feedback Score: 3 reviews	It should get better hwy mileage cause there is less rotational mass. You may loose some city millage if you do a lot of stop and go. You loose some stored tq(potential energy) in the flywheel for launch. So, it takes a little more gas to get going. A "street" lightweight will be heavy enough to not take to much gas on the launch. But, still get benefits on cruise. The gains will outweigh the losses. A "race" weight will be undesirable on launch. __________________ Comments should be taken as Opinions not as Statements of Fact

11-09-2010, 10:10 AM	#3
Lazarey Join Date: Jul 2010 Location: Texas Posts: 7 Trader Rating: (0) Feedback Score: 0 reviews	I agree with you on all of that, just wondering if the engine has to use more fuel to catch the engine as it rapidly spins down and if so, how much more...