Engine balancing & lightening

[edc]

What sort of gains and benefits can be achieved by balancing and lightening the engine eg crankshaft, flywheel conrods, pistons etc??

I gather it will allow a freer and higher revving unit (not really sure if that's what I need).

What might this cost for a 2.0 16v and do you think it's worth it??

[LDoR]

Well your right, it will be more free reving and should rev higher, this will result in more HP and give you very good throttle response. As for cost, i think i once saw an ad for around £500 but it's more likley to cost a few grand.

[max_torque]

Think the issues of "balance" and "weight" are slightly seperate as far as engine reciprocating masses go:

A std engine is usually balanced well enough for ocasional use at peak power rpm and say 500rpm more. Sustained high rpm use - ie racing (or where you've tuned car and peak power is now at a higher rpm) will require a better level of balance. The better ballance components are the more even the acceleration forces will be and the smoother and less friction the engine will have. (can be critical at high speed for bearing life etc.)

As for the weight loss. this is tricky for major engine internals without changing components or spending major money. Crank counter weights (the biggest mass) have to balance piston / con rod mass, so unless you loose weight from these you can't really touch crank (unless you go to a higher grade material crank that can have smaller bearing / sections for the same strength). You can lighten con rods quite easily, but by the time you have polished them up and equalised there masses (inc mass distribution ideally) you could easily spend 5 hrs on each one, and if you're paying someone to do this then your getting close to the £160 or so that forged H beam race rod will cost, which are both lighter and stronger!
For pistons it would be a brave man who starts machining any bits of your standard pistons, so again you up to forged pistons (circa £150 and up each)

The easiest and most noticable thing is a lightened flywheel, it improves acceleration bhp (not steady state so you can't measure it on a rolling road)(but you can calculate the power it absorbs)and may make gear changes faster etc. (could also lead to horrible idle drive / tip in low speed oscilations as well!)

If i was having my engine apart i would go for a lighter flywheel, and get engine balance to cope with say 500rpm above Pmax rpm. A typical balance for pistons / rods/ crank / flywheel / front pulley will be around the £500 mark, depending on how much they have to do to get it balanced and what balannce tollerance they use.

[edc]

Thanks guys,

So worth doing if the engine's already in bits (ish) for gas-flowing.

:cheers:

[RobT]

Until you already have head and cam work done, its not worth the agro. Even then, I think I would wait until the engine died first and then rebuild it to higher spec. Or start with a second engine in the first place which is negligible cost in relation to the mods cost.

For a proper blueprint from a race engine builder (and not Fred down the road who renovates taxi engines) I would think £2K. It should be done as a total engine rebuild IMO. Blueprinting I believe gives you perhaps 10% over std but that depends how good the manufacturing tolerances are on the original.

Further than optimisation of std parts, upgrading starts to get VERY expensive and quality building more important (and quality building dont come cheap !). I was pricing up fancy bits at Autosport international this year - steel crank £1K, steel rods £700 a set, forged pistons £700 a set, special piston pin, total seal rings, steel flywheel thats dowelled onto crank, head modified to take solid lifters (£320 a set for a 16V), dowelled cam belt wheel, titanium valve caps, etc etc etc. This could give you a 9-10K rev monster and would perhaps end up costing £5K plus.

Question is, how fast do you need to go and is there a better way of doing it - 1.8T transplant for eg with jabbasport big turbo - perhaps similar money.

Or buy a faster car.

Ave it

Rob

[edc]

Originally posted by RobT

Or buy a faster car.

Ave it

Rob

True, but that sort of sense doesn't always prevail - look at your car.

I was just trying to find out what could be done within a given budget (figure seems to fluctuate in my head),to optimise most of the standard fare without resorting to upgrading parts and ending up with a unit that resembles nothing like the one I started out with.

I like the revvy nature but I think 10k rpm is a bit excessive for me. A sensible 7.5k ish should suffice, but I don't want to lose out mid-range. When re-mapped I'll be looking for more punch in mid-range over big numbers up top.

[max_torque]

For big power on a road car i'd always go for a transplant, after all you get OEM driveability / durability for a reasonanble cost.
(and if it goes wrong parts are easy to get!)

If the engine was apart anyway i'd deffinately get the balance checked - you could weigh rods/ pistons your self (+ or - 1 gramm should be good enough) and get crank / flywheel re balanced (less that £200)

Mainly for piece of mind, after all if you've tuned up your engine then your going to be using that extra rpm!

[edc]

I'd agree in the main. My idea is to keep the mods vaguely sensible whilst the car is on the road. But there will come a point where it will be a second car ie when I have another one too / when next round of mods make it too harsh on the road or more suited to track days.

I realise that if I want big power then it would be sensible to get a forced induction unit. However, the fun for me is being able to thrash your car and throw it about and not risk too much serious injury with silly speeds.

ps did anybody see that program on BBC1 about speeding on the M25? The camera showed the speedo going beyond 200mph with various rear shots of a Skyline. What sort of power is in that!? Even a 600 bhp Skyline / 300ZX would struggle to get there, and this speedo was pulling cleanly and easily - loads left in it!