[NonaLude]

I've read across forums for a variety of different car makes and models and I can't find a single right answer so I figured I would post it here.
Are lightweight flywheels safe for our cars? My car specifically is a '99 5th gen. I ask because I've read that it could destroy transmissions because it's not dampening anything from the engine (read this on subie forum), alter idle (read this on chevy forum). Apparently this happens because the ECU has to be tuned for ignition timing to compensate for the lack of weight and pressure exerted on a lightweight flywheel.
My plan was to go with a 13lbs ACT flywheel for fun since it's my weekend driver (although I take it for commutes sometimes) and I don't plan on tuning my car at all (I have SH and I wanna keep ATTS and legal).
With this in mind, would it be safe for me to run a lightweight flywheel?
I also wouldn't mind running lightweight pulleys but... I've heard horror stories, wondering if there are horror stories for lightweight flywheels on untuned cars.

 

[Faulcun]

Its a complicated subject, but if you want to be super technical about it, it is less safe than a normal flywheel. Ill explain in short.

As an engine runs and spins, it produces harmonics/vibrations. The H22 has balance shafts specifically to combat this and nullify the harmful harmonics. The harmonic balancer pulley also has this job. Not all engines are made the same. Some manufacturers have more issues than others with harmonics. Boxer motors have a lot of issues, harmonics among others. More harmonics/vibrations ( when i say that im talking about vibration frequencies, not physical vibrations felt through the vehicle) equals wear on the bearings and can cause premature bearing failure.

Lightweight pulleys are ok EXCEPT for the harmonic balancer on the front of the crankshaft. If you arent upgrading it with an ATI damper, leave it stock.

As for flywheels, they do provide some dampening for harmonics, but nowhere near as effective as the other components. I would say the flywheel is last in line and is minimal to begin with. The clutch assembly is still heavy as well, so yes you are reducing rotating mass, but only a few pounds.

In the grand scheme of things, I wouldnt worry about a light flywheel. And no, your car will have no issues running with it. There are other things to consider though. While the throttle response is faster, giving up rotating mass also means you lose the ability for the car to maintain momentum while cruising on the highway for example. So you'll find yourself in the gas a little more to maintain speeds. Its not significant though. I think the most we've calculated on any of our vehicles was a 2mpg loss.

 

[NonaLude]

Its a complicated subject, but if you want to be super technical about it, it is less safe than a normal flywheel. Ill explain in short.

As an engine runs and spins, it produces harmonics/vibrations. The H22 has balance shafts specifically to combat this and nullify the harmful harmonics. The harmonic balancer pulley also has this job. Not all engines are made the same. Some manufacturers have more issues than others with harmonics. Boxer motors have a lot of issues, harmonics among others. More harmonics/vibrations ( when i say that im talking about vibration frequencies, not physical vibrations felt through the vehicle) equals wear on the bearings and can cause premature bearing failure.

Lightweight pulleys are ok EXCEPT for the harmonic balancer on the front of the crankshaft. If you arent upgrading it with an ATI damper, leave it stock.

As for flywheels, they do provide some dampening for harmonics, but nowhere near as effective as the other components. I would say the flywheel is last in line and is minimal to begin with. The clutch assembly is still heavy as well, so yes you are reducing rotating mass, but only a few pounds.

In the grand scheme of things, I wouldnt worry about a light flywheel. And no, your car will have no issues running with it. There are other things to consider though. While the throttle response is faster, giving up rotating mass also means you lose the ability for the car to maintain momentum while cruising on the highway for example. So you'll find yourself in the gas a little more to maintain speeds. Its not significant though. I think the most we've calculated on any of our vehicles was a 2mpg loss.

Thanks for the response. That's actually exactly the answer I was looking for haha. In that case I'll probably run a 13lbs ACT flywheel and a "stage 1" clutch when it's time to replace my clutch. I'll look into lighter pulleys if I have money to burn but following your comment, I'll only look at the ones for the accessories. I might consider an ATI as well just because my current one is 20+ years old.
Anyway, thanks for the help, I appreciate it. I get pretty scared about asking questions on forums because I've gotten flamed before 😅
But your answer was pretty much what I was looking for. Thank you and have a good one

 

[NonaLude]

Update: I can't even find any lightweight pulleys for the accessories, only for the crankshaft. Are most of them discontinued or something? I can't seem to find them anywhere.

 

[Faulcun]

Update: I can't even find any lightweight pulleys for the accessories, only for the crankshaft. Are most of them discontinued or something? I can't seem to find them anywhere.

Probably discontinued. Honestly you'd never notice a difference on the pulleys with a butt dyno anyways. You will notice a difference with the flywheel though.

Theres not a ton of support for these cars anymore, and even less for the SH. Im planning to change that this coming year. Hopefully Ill be making a few parts for these cars that dont exist anymore, or ever.

 

[NonaLude]

Probably discontinued. Honestly you'd never notice a difference on the pulleys with a butt dyno anyways. You will notice a difference with the flywheel though.

Theres not a ton of support for these cars anymore, and even less for the SH. Im planning to change that this coming year. Hopefully Ill be making a few parts for these cars that dont exist anymore, or ever.

Oh man that sounds exciting, can't wait to see what's in store heh. I'm just making a fun street car. Right now it's my daily driver but planning to make it more as a fun car and when that happens I plan on picking up a newer car so we'll see. But yeah, just for now I think a flywheel and clutch will make it plenty for what I need. Cheers

 

[mooncaller]

Theres not a ton of support for these cars anymore, and even less for the SH. Im planning to change that this coming year. Hopefully Ill be making a few parts for these cars that dont exist anymore, or ever.

What parts are you looking to make?
I have a 1993 K-swap with some 5th gen parts for wheel compatibility. But support for both 4th and 5th gen sucks right now.

 

[wavyg]

Oh man that sounds exciting, can't wait to see what's in store heh. I'm just making a fun street car. Right now it's my daily driver but planning to make it more as a fun car and when that happens I plan on picking up a newer car so we'll see. But yeah, just for now I think a flywheel and clutch will make it plenty for what I need. Cheers

I had a lightened Fidanza flywheel on my '01 SH for about five years. I believe it was in the 12-13 pound range. Anyway, I installed it at the same time as installing a Clutchmasters clutch disc (stage 2 I think?), poly motor mounts, Tein basic coilovers, and I even had carbon synchros installed in the trans. So I basically did a bunch of stuff all at the same time. Nothing wrong with that, but it was a lot of freshening up and tightening up at the same time. Just to give some context about what my experience was. So when I got it back on the road the biggest change was the poly motor mounts, they made it kinda shudder and vibrate at low rpms. It wasn't terrible, but it was and still is a little annoying. However, that and the coilovers changed my power to road transfer a lot. I went from broken motor mounts and softer suspension to a much tighter feel. I would get wheel hop and all kinds of flex before and now I could spin the wheels at will but with no hop or hesitation. I felt like the throttle response was better because of the flywheel but I did have to give it a tiny bit more to get the clutch engagement to be smooth and avoid stalling.

So that was then. But after about five years and maybe 30k miles my clutch was worn out and I had to pay someone to change it for me while I was overseas. The disc was in bad shape and the flywheel was very bad, apparently with cracks and burns and lots of signs of abuse. I never got to see it myself, unfortunately. So now I'm back to a stock flywheel and clutch and I've had it for about four years 20k miles.

I say all that to say this: Be prepared to have fun with it! But also be prepared to have to change it out sooner. I would also say be more gentle on it than I was... I can't quantify that in any meaningful way but I think being disciplined with your clutch technique is far underappreciated and I wish I had worked much harder when I was younger to learn proper and non-abusive clutching!

Good luck and I hope you get many good years and many thousands of miles out of it!

 

[Faulcun]

What parts are you looking to make?
I have a 1993 K-swap with some 5th gen parts for wheel compatibility. But support for both 4th and 5th gen sucks right now.

The main parts Ive been designing are adjustable upper control arms for the 5th gen SH front and rear. The control arms are different between the base model and SH in the front. I know nobody makes them for the SH, and im pretty sure nobody makes them for the base anymore. So that was something important to me because the adjustable ball joints for camber are garbage and constantly move.

The second part in design is a tubular cross member in the front. If anybody wants to use the H22 awd bell housing on the 5th gen, it requires you to cut the cross member to fit. I dont like doing that, and Id prefer to have a clean build. I think we can add a little more strength and bracing and save some weight at the same time.

Also working on a new cam trigger to replace the distributor for those who move to a COP setup since AEM stopped making theirs.

Two other things on my list I plan to address. S1Built's design for the rear differential required it to be flipped upside down. I dont like that because of fluid transfer from the yoke area back to the rear, among other things like changing the fluid. So Im going to address that situation eventually.

The other thing is possibly a double fuel cell system that stays under the vehicle. Most people dont care about putting a fuel cell in the cargo area in the trunk because a lot of the awd swaps are used for drag racing. My shop focuses on road course. So we'd like to keep the center of gravity as low as possible and forward of the rear axle. Moving 10 gallons into the trunk area is not ideal for weight transfer.

 

[wavyg]

The main parts Ive been designing are adjustable upper control arms for the 5th gen SH front and rear. The control arms are different between the base model and SH in the front. I know nobody makes them for the SH, and im pretty sure nobody makes them for the base anymore. So that was something important to me because the adjustable ball joints for camber are garbage and constantly move.

The second part in design is a tubular cross member in the front. If anybody wants to use the H22 awd bell housing on the 5th gen, it requires you to cut the cross member to fit. I dont like doing that, and Id prefer to have a clean build. I think we can add a little more strength and bracing and save some weight at the same time.

Also working on a new cam trigger to replace the distributor for those who move to a COP setup since AEM stopped making theirs.

Two other things on my list I plan to address. S1Built's design for the rear differential required it to be flipped upside down. I dont like that because of fluid transfer from the yoke area back to the rear, among other things like changing the fluid. So Im going to address that situation eventually.

The other thing is possibly a double fuel cell system that stays under the vehicle. Most people dont care about putting a fuel cell in the cargo area in the trunk because a lot of the awd swaps are used for drag racing. My shop focuses on road course. So we'd like to keep the center of gravity as low as possible and forward of the rear axle. Moving 10 gallons into the trunk area is not ideal for weight transfer.

Count me in for the control arms! There's a kid on FB that's supposedly got Godspeed making some adjustable control arms for the 5G but I don't think they will fit the SH so we'd be out of luck again. His name is "Ron Cheesman" and he's on the Prelude Nation FB group. Here's a YouTube video of him reviewing the prototype.

 

[mooncaller]

The main parts Ive been designing are adjustable upper control arms for the 5th gen SH front and rear. The control arms are different between the base model and SH in the front. I know nobody makes them for the SH, and im pretty sure nobody makes them for the base anymore. So that was something important to me because the adjustable ball joints for camber are garbage and constantly move.

The second part in design is a tubular cross member in the front. If anybody wants to use the H22 awd bell housing on the 5th gen, it requires you to cut the cross member to fit. I dont like doing that, and Id prefer to have a clean build. I think we can add a little more strength and bracing and save some weight at the same time.

Also working on a new cam trigger to replace the distributor for those who move to a COP setup since AEM stopped making theirs.

Two other things on my list I plan to address. S1Built's design for the rear differential required it to be flipped upside down. I dont like that because of fluid transfer from the yoke area back to the rear, among other things like changing the fluid. So Im going to address that situation eventually.

The other thing is possibly a double fuel cell system that stays under the vehicle. Most people dont care about putting a fuel cell in the cargo area in the trunk because a lot of the awd swaps are used for drag racing. My shop focuses on road course. So we'd like to keep the center of gravity as low as possible and forward of the rear axle. Moving 10 gallons into the trunk area is not ideal for weight transfer.

Out of this I think I would be most interested in the fuel cell.

A lot of this is pretty specific to the 5th gen and SH.

Keep me posted. The fuel cell is likely something I'd be interested in down the line.

 

[Faulcun]

Count me in for the control arms! There's a kid on FB that's supposedly got Godspeed making some adjustable control arms for the 5G but I don't think they will fit the SH so we'd be out of luck again. His name is "Ron Cheesman" and he's on the Prelude Nation FB group. Here's a YouTube video of him reviewing the prototype.

You know I do recall somebody posting up on a group buy for godspeed making those. I forgot all about that. Anyways, we are doing a billet aluminum design with replaceable factory ball joints, and easier to reach and more solid camber adjustment.

Out of this I think I would be most interested in the fuel cell.

A lot of this is pretty specific to the 5th gen and SH.

Keep me posted. The fuel cell is likely something I'd be interested in down the line.

Yeah, most of it initially will be designed around the 5th gen/SH simply because.... well thats what i have lol. But im working on designs for other vehicles as well like turbo manifolds for a twin turbo setup on a tiburon, a lower intake manifold for a supercharger setup on a 3.5L R50 pathfinder, and.... probably my favorite..... a proper cup holder for the CB7 accords that fit in that big gap space to the left of the parking brake handle. Where you supposed to put your big gulp with those tiny soda can cup holders under the radio?

Its taking some time, but im investing in expanding my business to do stuff like this for all car communities.At the same time I still have to run my normal business. Im just tired of people getting screwed and having no place to turn to so im getting set up to try and make a difference.

 

[mooncaller]

Yeah, most of it initially will be designed around the 5th gen/SH simply because.... well thats what i have lol. But im working on designs for other vehicles as well like turbo manifolds for a twin turbo setup on a tiburon, a lower intake manifold for a supercharger setup on a 3.5L R50 pathfinder, and.... probably my favorite..... a proper cup holder for the CB7 accords that fit in that big gap space to the left of the parking brake handle. Where you supposed to put your big gulp with those tiny soda can cup holders under the radio?

Its taking some time, but im investing in expanding my business to do stuff like this for all car communities.At the same time I still have to run my normal business. Im just tired of people getting screwed and having no place to turn to so im getting set up to try and make a difference.

I've been running into various lack of support issues along my journey.

 

[Rodmunch]

The main parts Ive been designing are adjustable upper control arms for the 5th gen SH front and rear. The control arms are different between the base model and SH in the front. I know nobody makes them for the SH, and im pretty sure nobody makes them for the base anymore. So that was something important to me because the adjustable ball joints for camber are garbage and constantly move.

The second part in design is a tubular cross member in the front. If anybody wants to use the H22 awd bell housing on the 5th gen, it requires you to cut the cross member to fit. I dont like doing that, and Id prefer to have a clean build. I think we can add a little more strength and bracing and save some weight at the same time.

Also working on a new cam trigger to replace the distributor for those who move to a COP setup since AEM stopped making theirs.

Two other things on my list I plan to address. S1Built's design for the rear differential required it to be flipped upside down. I dont like that because of fluid transfer from the yoke area back to the rear, among other things like changing the fluid. So Im going to address that situation eventually.

The other thing is possibly a double fuel cell system that stays under the vehicle. Most people dont care about putting a fuel cell in the cargo area in the trunk because a lot of the awd swaps are used for drag racing. My shop focuses on road course. So we'd like to keep the center of gravity as low as possible and forward of the rear axle. Moving 10 gallons into the trunk area is not ideal for weight transfer.

Hi how are the control arms coming along? I would commit to buying a set in a heartbeat. Happy holidays!

 

[Faulcun]

Hi how are the control arms coming along? I would commit to buying a set in a heartbeat. Happy holidays!

I have some designs, but we havent cut metal yet. Still working on expanding the shop. It'll be this coming year before we're ready to prototype them.