Stock Flywheel vs. Fidanza Aluminum for Turbo L20B

[qwik510]

Hi everyone,

It has been a while since I have been on here. Did you miss me? Lol.

I have an old school L20B CarTech Turbo that will be going into my 510. It will use a Weber 38/38 carb. It will be backed by a dogleg 5 speed. It will be used as a street car. This setup will replace my stock L20B with SU’s.

I had Eiji at Datsun Spirit rebuild the engine to stock specs. We built it for reliability. My plan is to run low boost pressure (5-7psi max) so hopefully no intercooler or water or alcohol injection.

I have the stock 225mm steel flywheel and I also have a 240mm Fidanza 240Z flywheel.

For a street car, which flywheel would be a better choice for the turbo motor and why?

Thanks for your help.

PFA

[datzenmike]

Either is fine. Stock L20B is about 93 hp so 7 PSI boost is (theoretically) about 50% increase. So just under 140 hp. A 225mm will hold that and so will the 240mm.

225mm pressure plate. All 550 kilogram clamping force.
'79-'83 280zx non turbo coupe.... 30210-N4210
74-78 620 and 80-82 720.......... 30210-PO100 and YO100
'73 240z and '74 260z.............. 30210-N3100

240mm pressure plate
300zx non turbo.................... 30210-P9500..... 550 kg
'84-'85 300zx turbo................. 30210-P9600..... 600 kg

I think the 240mm pressure plate from the KA powered D21 Hardbody might be even better but they rate in foot pounds of torque handled and not clamping force. (apples and oranges)

[qwik510]

Either is fine. Stock L20B is about 93 hp so 7 PSI boost is (theoretically) about 50% increase. So just under 140 hp. A 225mm will hold that and so will the 240mm.

225mm pressure plate. All 550 kilogram clamping force.
'79-'83 280zx non turbo coupe.... 30210-N4210
74-78 620 and 80-82 720.......... 30210-PO100 and YO100
'73 240z and '74 260z.............. 30210-N3100

240mm pressure plate
300zx non turbo.................... 30210-P9500..... 550 kg
'84-'85 300zx turbo................. 30210-P9600..... 600 kg

I think the 240mm pressure plate from the KA powered D21 Hardbody might be even better but they rate in foot pounds of torque handled and not clamping force. (apples and oranges)

Thanks Mike. I think I should have clarified my questions better.

I am trying to decide if the lighter flywheel will be better or worse for a street driven car. I know the lighter flywheel will allow the engine to rev faster but will there be a sacrifice to the inertia that will keep the engine turning and also how will it effect turbo spool up and on/off throttle response?

[funwithmonkeys]

In my car I put in a 13lb chromoly flywheel and I have no problems at all on the street. I can just ease out on the clutch at idle and it crawls away. Once you know where the bite point is on it it is pretty easy. My total rotating mass is 22lb. Go with the lighter one.

[iceman510]

What are the weight of your two flywheels Dave? I would probably go for smaller diameter and lighter myself for first try, mainly to aid spool-up. I don't think the lighter will affect cruising inertia.

[Byron510]

I would agree with iceman on this. My race car has an Fidamza aluminum 200mm clutch running a roadster PP which is lighter than my 14lm steel 200 mm flywheel combo and it’s still no issue for lack of inertia.
In the end the clutches are so heavy, I’d think going with the lightest flywheel possible is still a solid choice.
Byron

[icehouse]

I installed my first lightened flywheel on one of my cars. It's a S15 SR20DET and it's annoying! I would pay to have the stock heavy unit back. I was one flywheel short and ended up with a lightened flywheel for super cheap. All it does is make it harder to start in first gear. Maybe with a stock clutch it would be that bad but with a upgraded clutch its beyond annoying. You have to rev the engine more and its just not smooth. Also every car I DD is an old datsun rust bucket with a 5 or 6 speed so I'm not rusty at shifting.

I vote cash the aluminum flywheel in and run the stock guy.

[bertvorgon]

For what it is worth, my steel flywheel is 17lbs, with the roadster pressure plate and SPRUNG 4 puck ceramic disc. I have never had a clutch issue, traffic is no problem, it handles my 250 RWHP and almost as much torque and 16 PSI boost.

It has been a good balance between response and real world drive-ability.

[qwik510]

What are the weight of your two flywheels Dave? I would probably go for smaller diameter and lighter myself for first try, mainly to aid spool-up. I don't think the lighter will affect cruising inertia.

The Fidanza flywheel is 10 pounds. The stock is 28 pounds. I’ll be running an Exedy OEM replacement clutch kit.

After reading Icehouse’s comments, I am leaning towards going with the stock flywheel. Change my mind.

[datzenmike]

Flywheels store kinetic energy that can be used to get a heavy car off the line and moving. A lightened wheel will need to be spun faster to store the same energy, there's no way around this. This energy is not wasted and is returned when you let off the gas to slow down. A lighter wheel will slow down faster. The 510 is just over a ton in weight and a lighter wheel probably won't be as noticeable as a 3,000 pound car or truck with the same engine. But removing 18 pounds? yeah I wouldn't do that. This is more like a 'racing' thing where you are moving all the time and rarely stop. A lot of 'racing' things just don't work on daily driven street cars. The young don't mind too loud, too stiff, too hard to steer, a lot of work to drive. I'm older and like to enjoy driving.

[bertvorgon]

It has been a long time since I have seen one of the old draw through systems, very cool.

5-7 lbs will be just great on a stock motor. My original permutation of my kit, was for a stock engine and the first 5 lbs got the job done well. Bonus round back in the "old" days was our pump premium was 98 octane.

What is the best octane in your area? We have Chevron 94 here.

[qwik510]

Flywheels store kinetic energy that can be used to get a heavy car off the line and moving. A lightened wheel will need to be spun faster to store the same energy, there's no way around this. This energy is not wasted and is returned when you let off the gas to slow down. A lighter wheel will slow down faster. The 510 is just over a ton in weight and a lighter wheel probably won't be as noticeable as a 3,000 pound car or truck with the same engine. But removing 18 pounds? yeah I wouldn't do that. This is more like a 'racing' thing where you are moving all the time and rarely stop. A lot of 'racing' things just don't work on daily driven street cars. The young don't mind too loud, too stiff, too hard to steer, a lot of work to drive. I'm older and like to enjoy driving.

This helps a lot. Thanks Mike!

[qwik510]

It has been a long time since I have seen one of the old draw through systems, very cool.

5-7 lbs will be just great on a stock motor. My original permutation of my kit, was for a stock engine and the first 5 lbs got the job done well. Bonus round back in the "old" days was our pump premium was 98 octane.

What is the best octane in your area? We have Chevron 94 here.

We get 93 octane here.

Thanks

[Byron510]

A lot of 'racing' things just don't work on daily driven street cars.... I'm older and like to enjoy driving.

Mike - I would agree with you much of the time on this statement. It boils down to preference, really.
David, I would also agree that Keith has the right balance at a 17 lbs - it's right in the middle of what you have got on hand.
10 lbs is pretty light, and you'd be shifting fast to keep the RPM's before they drop. At 28 lbs, the synchros will be getting a workout when driven in a spirited way. It really comes down to what you want as a driver.

BTW - cool vintage turbo kit - what's this going into?

Byron

[datzenmike]

Preference, yup you can never say for sure what someone else will prefer. This is why I mentioned age as a rule for selecting just how much you might be comfortable with. It's a sliding scale and the younger you are the more you put up with irritation, discomfort and doing things the hard way. If older this shit get old really fast.