understanding Lightened Flywheel combined with larger tires

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Abra-Cadaver
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understanding Lightened Flywheel combined with larger tires

Post by Abra-Cadaver » Tue Dec 04, 2018 9:16 pm

If I understand what I've read correctly, lightening the flywheel will increase engine revs quicker, resulting in better performance at speed, climbing hills etc, but will be harder to take off from a dead stop- since the revs will drop quicker with a lighter flywheel as clutch engages.
This seems like a lightened flywheel would be an issue with oversize wheels/tires, as it is already heavy and slow to take off from a dead stop, however the trade off of better rpm holding at highway speeds and hills sounds nice.

Taking what I know from the world of offroad Suzukis/Geos and bigger/heavier tires, Would it be beneficial to:
- use a mild stage 1 clutch with heavier off road tires on the T4wd with (or without) a lightened flywheel??
- Keep clutch stock and lighten FW?
-Don't lighten FW and go a mild step up on clutch for heavier wheels and tires?

I had a sprung over lifted '85 Tintop SJ410 on 33's with heavy duty clutch and built 8V motor before my Tercel, it's a completely different world, but kind of the same cult forum folk. The stronger clutch benefits bigger heavy tires, but I don't know if that is the same story for the T4wd/lightened flywheel.
Lots more experienced people here, so I figured I'd ask for community input before I get into the big job i have ahead of me. :?

- Noah

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Re: understanding Lightened Flywheel combined with larger tires

Post by The Professor » Wed Dec 05, 2018 7:57 am

If you're putting on larger tires, just keep the stock flywheel. I have lightweight flywheels on my turbo wagon and WRX and while it does free up some existing horsepower that was previously accelerating the extra flywheel mass, there are tradeoffs with drivability, comfort, etc.
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Re: understanding Lightened Flywheel combined with larger tires

Post by Abra-Cadaver » Wed Dec 05, 2018 12:56 pm

The Professor wrote:
Wed Dec 05, 2018 7:57 am
If you're putting on larger tires, just keep the stock flywheel. I have lightweight flywheels on my turbo wagon and WRX and while it does free up some existing horsepower that was previously accelerating the extra flywheel mass, there are tradeoffs with drivability, comfort, etc.
from the offroad world, we put heavier flywheels on to avoid stalling while climbing over things... I've only heard of people putting lightweight flywheels on their Tercels, but I'm not (and nobody else is, let's be honest) street racing their 60hp 4wd Tercel. I think the flywheels were heavy from the factory because the car was designed for areas where there would be in snow and mud. A heavy flywheel helps keep the engine from stalling against the added resistance/strain from sloppy/messy surface conditions.
E.G. with my built Suzuki, I could put it in 4Low, let out the clutch from a dead stop in snow/mud in 2nd gear on an incline, and I would get out and walk up the muddy/snowy hill next to my rig while it idled and crawled up hills. If it had a stock or lighter flywheel, I am certain it would have stalled trying to do that.

Since these wheels and tires feel just about as heavy as the 33" muds felt on that rig, wouldn't it seem a mild HD clutch would benefit a Tercel running more rotational mass. :? :?

(ps has anyone ever considered the 8v 1.6L suzuki sidekick/geo tracker motor? Looks very close to the 3AC. I have this huge desire to see how hard it would be to put axles and running gear from a track/kick into a tercel- the wheelbase and width is almost identical too.)

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Re: understanding Lightened Flywheel combined with larger tires

Post by Petros » Wed Dec 05, 2018 5:18 pm

sounds like you are getting a lot of bogus speculations from those that do not know exactly what they are talking about. All 3a engines have the massive flywheel (heavier than any other Toyota engine at the time), it was designed to go into their entry level FWD car. Almost all of them went into 2wd cars, so whatever their merits for rock crawlers or off road use, that was NOT the motivation for Toyota with the 3a engine.

Lightening the flywheel does not give you more hp. It allows the engine to rev up faster which is important for performance shifting, be it on or off road. It will also reduce the weight of the installation overall, a benefit to pursue no matter what other benefits it offers.

for use in the Tercel model, their entry level cars, most likely bought by a beginner driver, it makes the engine more stall resistant from botched shifts or poor clutch/throttle skills. I think this is the motivation for toyota to put them in the tercel, rather than offering a higher hp engine, like Honda, Nissan and Mazda offered at the time for their entry level car. It was cheaper (less development investment) and easier to use a small lower hp engine with a heavier flywheel. Particularly since the ever increasing emissions restrictions, the heavier flywheel is a simple and attractive approach to getting easy shifting/drivablity without the complex wizardry that Honda used with their CVCC engine, or going to EFI like the others had done. Toyota was always more cautious and conservative than their competitors. So when a new driver goes to test drive a Honda or Nissan, but finds the Tercel results in less stalled engines (it is more forgiving of poor clutch technique), they are more likely to buy the Tercel. I suspect it was a marketing decision.

Although a heavier flywheel might be better for low speed rock crawling, I do not see any advantage to a heavy flywheel if you use proper clutch technique. The tercel4wd was never intended as an off road machine, their target market was bird watching according to their internal documents. In the tercel, once you have good clutch/throttle shifting skills, the extra weight just slows the throttle response and adds useless weight to the car. Tuning the engine to get a few more hp completely does away with the marginal amount of stall resistance the heavier flywheel offers.

There is one other benefit to heavy flywheels, it allows for less precision in the balancing of the engine parts, and mitigates the vibration it causes. but toyotas engine in my experience have highly balanced engines compared to the older crap that came out of Detroit. The heavy flywheel meant they did not have to reject as many parts that were out of tolerance in a big cast iron engine. Competition, regulations, and performance demands have eliminated that approach for manufacturers now. But that does not seem to be Toyota's motivation, particularly when all of their other, higher hp engines, had lighter flywheels.
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Re: understanding Lightened Flywheel combined with larger tires

Post by Abra-Cadaver » Wed Dec 05, 2018 6:27 pm

well yeah- heavier fly wheel = harder to stall, engine revs don't fall as fast as clutch grabs, compared to a lighter flywheel. But since I'm running heavier wheels/tires, I'm curious if keeping the stock heavy flywheel and do a mild bump up the clutch grab with, say, 1 stage up from stock (is that stage 1 or 2??) would help get me moving from a stop since gearing doesn't seem to be an option. Seems that a lighter flywheel with heavier tires would not help from a dead stop even though it would rev up faster, because a lighter flywheel would not transfer as much torque to the drivetrain as the clutch engages as a heavy flywheel does. ??

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Re: understanding Lightened Flywheel combined with larger tires

Post by Petros » Thu Dec 06, 2018 1:42 am

I do not think there would be much difference with a lighter or heavier flywheel on larger heavier wheels and tires if you use proper clutch technique.

A heavy duty (more heat resistant) clutch will serve you well if you intend to do a lot of off roading. What you need to keep heavy wheels and tires moving from a dead stop is more power/torque. flywheel will not make a difference. the heavier flywheel only helps from a dead stop where once rolling the car keeps moving (on a smooth paved surface), I can not see this as your off road model. if the car is not moving after the initial clutch engagment the engine will stall. That is best accomplished with a smooth and steady clutch engagement, with a bit of slip to start out.

That being said, if you have the 4.11:1 final drive it should handle the larger tires well, without issues. certainly better than the earlier 3.73:1. Coaxing a bit more low end torque out of the engine will make a noticeable difference, more than a heavier flywheel.

what improvements to the engine/exhaust have you made, or are planning?
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
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Re: understanding Lightened Flywheel combined with larger tires

Post by Abra-Cadaver » Thu Dec 06, 2018 4:54 pm

Petros wrote:
Thu Dec 06, 2018 1:42 am

That being said, if you have the 4.11:1 final drive it should handle the larger tires well, without issues. certainly better than the earlier 3.73:1. Coaxing a bit more low end torque out of the engine will make a noticeable difference, more than a heavier flywheel.

what improvements to the engine/exhaust have you made, or are planning?
as always, thanks for engaging in informative neutral discussion Peter! That's part of what I love about this forum compared to most others.
Yes I have the 86 year w/ 4.11 gears. Would love something lower for hills. 5th and 4th gear are essentially the same torque on the HWY, 5th gear just makes the engine quiet down 400rpms :lol:

I think I have a smidge larger exhaust than stock from cat back. I actually should have measured it last week when I had the new cat-back installed. This is my second cat-back on this car in 5 years, I think they just replaced what was on there before from PO (who bought this car new in 1985, I am the second owner.)
On the engine I don't have any real mods (and can't run a weber thanks to CA smog,) just have advanced the timing, I ran a K&N air filter but my butt-dyno told me it was actually worse than stock. Went back to a paper filter. Clamp on style cone filter on valve cover breather. Six months ago my timing belt slipped and broke some ribs off the belt (which you may have remembered that post) so I replaced the timing belt, cam seal, crank seal, water pump, thermostat, radiator, hoses, fuel filter, spark plugs, wires, distributor coil, cap, rotor, distributor O-ring, alternator belt, power steering belt, A/C belt, timing cover seal, valve cover gasket, halfmoon and grommet gaskets, valve stem seals, and adjusted the valves.
I've been trying to source a 4AC lower end locally, since I will be replacing trans as soon as I get a chance, but having no luck. Any other ideas I could try to help get some oomph from the 3AC are welcomed.

2 Other things I want to check are:
1) the torque on the exhaust manifold bolts. The exhaust sounds a little louder up front than it does in the back (not sure if that's just normal for these cars,) and I've never touched the manifold bolts since I've had the car. Can't say if the 75 year old guy I got it from ever did either. At the same time, I am also afraid to shear off a manifold stud :?
2) the oblonged rubber seal under the air filter cover. I think it sits on the air filter enough to be ok, but I also think its 30+ years old and just whooped and may be allowing some extra air to pass by over the top possibly causing a lean condition. My plan is to seal the air box with 1/4 inch weather stripping the way I did on my 1983 Suzuki GS850 motorcycle, only it should be much easier to find a circular rubber foam insulator with adhesive on one side that will have the same diameter as the Tercel air filter, to stick onto the underside of the cover. Custom cutting each strip for the weird shaped airbox on the bike was a PITA.

My car diesels every now and then after turning it off (maybe once a week or less) .. last week it dieseled for about 20 seconds. I've had cars diesel before, but that was ridiculous. I was laughing but I wanted to cry a little bit too :lol: Need to determine if it's just the timing advance, running lean possibly from air cleaner cover rubber, or if my EGR system needs some love.

Noah

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Re: understanding Lightened Flywheel combined with larger tires

Post by Petros » Thu Dec 06, 2018 5:49 pm

the 4ac low end will help, more displacement. when you rebuild it you can also mill the head to raise the compression ratio a bit as well to add a bit of power, but do not go too much. And you can overbore the cylinders to get a bit more displacment, this will require oversized pistions (if you were going to replace the pistons anyway, this is a good thing to do). you may have to switch to premium fuel or you will have head gasket problems with the higher compression.

You can install a Delta Cams street performance reground cam shaft. it is a fairly easy installation, and I think they are about $59. (exchange price) last time I checked. Delta Cams is in Tacoma WA

Along with the advanced timing, these will give you the extra low end power you will need for the larger tires and wheels. with the 4.11:1 final drive ratio it will work fine, and neither of these are too costly. And from the outside of the engine, both of these will pass the visual inspection and still pass the emissions test as well.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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Re: understanding Lightened Flywheel combined with larger tires

Post by Abra-Cadaver » Thu Dec 06, 2018 7:44 pm

Petros wrote:
Thu Dec 06, 2018 5:49 pm
the 4ac low end will help, more displacement. when you rebuild it you can also mill the head to raise the compression ratio a bit as well to add a bit of power, but do not go too much. And you can overbore the cylinders to get a bit more displacment, this will require oversized pistions (if you were going to replace the pistons anyway, this is a good thing to do). you may have to switch to premium fuel or you will have head gasket problems with the higher compression.

You can install a Delta Cams street performance reground cam shaft. it is a fairly easy installation, and I think they are about $59. (exchange price) last time I checked. Delta Cams is in Tacoma WA

Along with the advanced timing, these will give you the extra low end power you will need for the larger tires and wheels. with the 4.11:1 final drive ratio it will work fine, and neither of these are too costly. And from the outside of the engine, both of these will pass the visual inspection and still pass the emissions test as well.
How long is the turn around on the Delta cams? I saw a company called Schneider that shows a range of grinds for specific rpm ranges- the first one being 1500-5500 which is right where ours run. I think Delta has a better price if it is still ballpark of the $59 you mentioned, though they have nothing listed on their site. Also: Iskenderian cams is right up the road. I had an Isky cam in my old 4x4 Zuk. Not sure what they have for 3ac motors. Ideally, I hope I can find a 4AC nearby and rebuild it over time with all these improvements and install it. Need to deal with what I've got right now.

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Re: understanding Lightened Flywheel combined with larger tires

Post by Petros » Fri Dec 07, 2018 3:10 am

as I recall the Schneider cams are new billet and fairly costly. Forum member Synth used a Schneider on his rebuild with a weber carb, but went back to the factory cam as it was way too much cam for a street engine. though I do not know what grind it was, if they offer a more mild grind they may be okay (if it was not for the price).

Delta has the 3ac/4ac grind in their inventory but you may have to call them to order it. they will send you the cam and charge you a core charge. you get refunded the core charge when you return to them a good usable core cam shaft.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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Re: understanding Lightened Flywheel combined with larger tires

Post by The Professor » Fri Dec 07, 2018 7:40 am

You have to call Delta Cams to learn the options for your application, their website hasn't changed in at least 15 years. They are affordable, reliable and trusted in the old school Subaru world. They can also do custom grinds outside of what they normally offer.
1975 Subaru SuperStar wagon
1984 Subaru Turbo-Traction wagon
1984 Subaru Turbo-Traction coupe
1987 Subaru RX coupe
1987 Toyota Tercel SR5 wagon
1987 Subaru RX Type-RA coupe
1999 Subaru Forester S
2002 Subaru WRX sedan

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