LIGHTENED FLYWHEEL

[John McCormack]

My recently acquired 1956 TR3 is a very stock motor with the only modifications being slightly larger inlet valves and 9lbs off the flywheel.

The car performs significantly better than my TR2s which have 86/87mm pistons and one has a mild cam and is balanced. The TR3 accelerates better and has more power on hills at 110-120 km/h.

It does have slightly smaller diameter tyres, 195/65 compared to 175/80 on the TR2s

I'm wondering how much difference the lightened flywheel will make to overall performance. 

 

[Drewmotty]

How much does the flywheel weigh John. Early TR3 flywheels we’re 21 lb as standard, about 9 lb lighter than the later ones. 

[Lebro]

Surely the mass of the flywheel cannot have any effect on horsepower, at best it may enable faster acceleration in 1st gear, after that the inertia of the whole car will determine acceleration performance.

Bob

[Hamish]

As Bob says 

I love my clutch carrier type flywheel. Very quick acceleration response  - award winning in fact.

but I also find it very useful for high speed driving down gear changes less back axle lock ups even with the same throttle blip on the down change.

Ticks over well too. My previous was a lightened TR3a flywheel machined down to 8.9kg. 
so not far off the early 3 flywheel as I learn from Drewmotty 

[Andy Moltu]

Ultimately a lightened fly doesn’t affect power significantly but does impede acceleration as the engine has to spin up a heavy mass. The 4 pot flywheel is heavy so say the least. Reduces the risk of stalling, however is a hefty weight hanging off the back of the crank has been considered a possible contributing factor in broken cranks (Is that purely down to mass or imbalanced mass is a matter for speculation) On a low revving tractor application this is probably unimportant but at higher revs in the TR application it may be more of an issue and presumably even more so in higher revving tuned and race engines.

A light flywheel makes a big difference to pick up and makes a more pleasing drive. Careful weight reduction on the standard fly is worthwhile. Ideally by someone who knows where to remove the weight without weakening it (flywheel disintegration is probably an unwelcome thing at 5krpm)! If you want a lot of weight reduction there are alternative after market options. “Spider” steel or alloy with a steel insert for the clutch. I picked up one of the former on eBay from one of the TR suppliers and am very happy.

[roger murray-evans]

Maybe has a 4.1:1 diff?

Roger M-E

[Hamish]

6 hours ago, roger murray-evans said:

Maybe has a 4.1:1 diff?

Roger M-E

Good point !!!

[iain]

6 hours ago, roger murray-evans said:

Maybe has a 4.1:1 diff?

Roger M-E

Good point and one that makes a considerable difference.

[Drewmotty]

8 hours ago, Lebro said:

Surely the mass of the flywheel cannot have any effect on horsepower, at best it may enable faster acceleration in 1st gear, after that the inertia of the whole car will determine acceleration performance.

Bob

On tight tracks where overtaking is difficult and the start is extra important touring car teams have been known to fit heavy flywheels to aid getting off the line. They have also been used to help maintain momentum on short rises and maybe save a gear change on certain corners.
The point is that a light flywheel will change the characteristics of the car but won’t be an advantage in all situations, especially on the road. 

[Motorsport Mickey]

Just now, iain said:

Good point and one that makes a considerable difference.

Standard Vanguards ran a 4.3 diff, still available, even better… definitely needs an overdrive though.

Mick Richards

[John McCormack]

Thank you all.

I have just confirmed it has a 3.7 diff. The diff has never been out of the car. A benefit of having acquired the car from the owner who bought the car as a near new 2nd hand car in early 1958, and who kept all his records, is you do know what has been done to it.

The TR3 does have 195/65 tyres which gives a 10% smaller diameter than the TR2s which have 175/80 tyres.

I think it is a combination of the engine mods, smaller diameter tyres and that the car has done less than 50,000 miles are the reasons for its performance.

 

[iain]

Those tyres would near enough give you a 4.1:1 ratio?

[roger murray-evans]

The other thing that may influence the difference is that the standard TR3, as far as I can make out, has 1 3/4" SUs and developes more torque  and at a slightly higher rpm than the TR2 on it's 1 1/2" SUs and pretty much around the 70mph mark in top gear. Plus it was advertised as having the extra 5 bhp! This, in conjunction with the smaller diameter tyres may well  make a noticeable difference? 

Roger M-E

[John McCormack]

3 hours ago, roger murray-evans said:

The other thing that may influence the difference is that the standard TR3, as far as I can make out, has 1 3/4" SUs and developes more torque  and at a slightly higher rpm than the TR2 on it's 1 1/2" SUs and pretty much around the 70mph mark in top gear. Plus it was advertised as having the extra 5 bhp! This, in conjunction with the smaller diameter tyres may well  make a noticeable difference? 

Roger M-E

Yes it does have what was called the Le Mans head. This was a modified low port head following the le Mans experience, in this car further modified with enlarged inlet valves, and with the 1 3/4" SUs.

It isn't easy to compare the performance of these cars, they all have different states of modification, tyres/wheels etc.

My long door TR2 has the low port head and 1 1/2" SUs but being a former race car has a mild cam, 87mm pistons and balance. It is a better performer than my other TR2, a short door, which has 86mm pistons, a high port head and 1 3/4" carbies but is otherwise stock.

The TR3 outshines them both in performance.