numpty question......

[iab]

Hi,

 

This will show my complete technical incompetance, but what is the benefit of a lightweight flywheel??

 

I was told that this is one of the most important upgrades to get for a VX, is this true??

 

thanks.

[Subaru Blue SV]

A lighter flywheel has less weight and so accelerates faster meaning that the car will reach max RPM faster.

The down side is that the flywheel gives the cranshaft momontum and smoothes out the firing of the pistons. thus at the same tickover a car with a lighter flywheel will be "lumpier" on tickover and if its really light the tickover may need to be raised or else the car may frequently stall

 

I think !

[Paul McKenzie]

Better throttle response and engine pick-up due to lowered inertia.

 

This was one of my first mods and we've also just done it on Smiffy's VX...he'll be able to report back this afternoon when the engine's back in 😬

 

The later pot-type flywheel (late '93 on) is massively heavy and they take a hell of a lot of weight off this (mine). Smiffy's is the ealier lighter one, but this is still lightened about 25%. You need to get this done by a good professional engine tuner and engineer because it is absolutely critical to get the flywheel and clutch expertly balanced for smoothness and safety.

 

Done properly the lightened and balanced cast flywheel will make a very noticeable difference to engine response, and is safe up to 8000 rpm. For tuned engines operating consistently above 8000rpm you need to buy a steel flywheel from SBD or QED etc.

 

Paul

[I reply to every thread]

Having seen two flywheels explode & the photos of the German VX Caterham that it happened to I wouldn't fit a lightened wheel. I went to a steel wheel.

 

I saw an Alfasud flywheel explode in the Paddock at Brands when the driver was waiting to go out for a race. One lump came through the bulkhead & exited through the roof about 8" from his head.He was OK but I suspect that his overalls went on a hot wash that night.

 

For the sake of £an extra £100 or so is it worth the risk?

[Joe 90]

As always, there is a right way and a wrong way of doing things. Hacking weight off a standard production flywheel is risky unless it is a well known application. There should be no worries with a proper race flywheel.

 

Does anyone know if reducing flywheel inertia raises or lower crankshaft stresses. I had a big arguement about this a while ago, but we could never resolve it.

 

SEP field working, not spotted in 101,600 miles. Some photos on webshots, updated 10 June

[Gambo]

I put a lightened flywheel and 7.5" clutch on my car (VX). certanley improved pick up . It did hit the drivability a little, it now protests if i put my foot down in fith at 1500rpm . it did save 8kg's. the original was 16kg's. so infact it halved the weight. and also moved it to a 7.5" diameter. the ring gear is on spokes you see. so the rotational mass has been greatly reduced. mind you it will not idle below 1300rpm. it's tooooo lumpy. I think It does reduce the strees on the crank as the end has less weight to accelerate or decellerate. I also can get away with out heal and toe down changes without locking the rear wheels if I am feeling lazy.

[free amp easy]

Hi Paul,

you said that the lightened flywheel was the first mod you had done, what else have you had done and were the benefits noticable/beneficial?

 

 

[Bare]

In my experiences a Lightened Flywheel makes a slight but noticeable difference in 1st gear acceleration, a bit less in 2nd gear and damned little to none at all in 3rd and 4th.

A usefull "mod" if yer going after every reasonably easy to get bit of power, but no major increases by any stretch of one's credibility.

But onna Rad Car? I won't waste my Time and Money on one of those again :-)

[Paul McKenzie]

Windswept,

 

I've had the engine moderately tuned by Dave Brookes Engines at Crewe. The objective was to build a powerful and flexible engine that would run on the original 45's (to avoid the extra expense and fiddle of going to injection).

 

Very briefly this involved forged pistons; 11:1 comp. ratio; new Kent non-hydraulic cams; solid lifters; Iskey springs; steel oil pump gear; baffled sump;extensive work to Caterham inlet manifold; 3D ignition; wasted spark; DTA programmable ignition ECU; lots of small items, gaskets etc.

 

The most important part is putting all this together properly, followed by rolling road tuning to optimise the ignition and carb. set-up. Result in this case was 220bhp. and a strong, fast, smooth engine that sounds great.

 

The beauty of the VX is you can get decent power without going to extensive head work. In fact breathing on the standard head is said to be good right up to 235 bhp, above this head work is definitely required. Although it's relatively "easy" to get good power from the VX, don't let anyone fool you that it's cheap....tuning any engine costs money (usually more than you originally envisaged) if it's to be done properly.

 

Paul

 

 

[Smiffy]

Still waiting for rain to stop to get out for a decent blat since engine went back in yesterday. I had a short drive in the car and my mate Clayhead (who has a well sorted X Flow) drove it the half dozen or so miles home.

 

Lightening the flywheel a little but more importantly balancing the whole flywheel / clutch assembly appears to have totally transformed my car. (Clutch cover balance was a bit out making the car quite "buzzy" at higher RPM. Clayhead was raving about the difference it has made and the fact that the engine rev's through the range so much more cleanly so I can't wait to get out for an hour or two myself. Seems to be a well spent £60 ! Having the engine out also allowed me to tidy a few bits n bobs up.

 

Having had my first 18 months of 7 ownership, in my humble and amatuer opinion, I would suggest you maximise your existing set up before even thinking about more power. With a not inconsiderable 175bhp as std, you can make your car much more enjoyable by just sorting out the fairly cheap and easy things. I've fitted uprated dampers and springs, bigger front ARB, rear ARB, Yoko 032 tyres.

 

My next planned upgrades are proper ratios for the gearbox (got the original crappy rations which make 1st almost unuseable - although lighter flywheel seems to make this less of a problem) and big front brakes. Only once I've done this, am I going to think about yielding to the temptation to go for more power.

 

Hope this helps - there is however no cure for the dreaded upgradeitis virus !