38 replies to this topic

[chris]

I look for the weight of the Z20LEH rods and piston (with axle and rings) in oder to balance a crankshaft.

[zebwach]

I will know the weight of the Z20LET rods and pistons in the next few days as they are being removed from my car. Is that of any use? Zach

[chris]

I have got a Z20LEH block without rods and pistons. I will install new Cosworth pistons with lighten conrods. In order to balance correctly the crankshaft, I have to remove some weight from crankshaft couterweight. So, I would be grateful if somebody could give me this information

[alanoo]

In fact you'll have to add some weight to the crank Check randy's Europa build blog

[Winstar]

In fact you'll have to add some weight to the crank

Check randy's Europa build blog

however I don't think the build blog is still up

[alanoo]

True, it does not seem to be completely migrated on their new website maybe there's a mirror somewhere...

[Duncan VXR]

As Zac has stated, I will have his LET stuff out very soon to fit the new cosworth bits and could confirm. I have some oe LEH rods in the garage I could weigh but tbh who ever is balancing it all should be able to confirm what is needed DG

[Nev]

When I stripped my Z20LET block, I specifically weighed a single OEM piston + con-rod + 2 rod bolts. This came to 1.145 Kg (with minimal variance between each of the 4 cylinders). However, as the Z20LEH pistons differ both in manufacturer and fabrication technique they will most likely be of slightly different weight. Regardless of this, I also have heard that you will need to ADD weight to your crank counterweights in order to achieve neutral balance. Nev.

[Nev]

Chris, Do you realise that if you install the Cosworth forged pistons, they require a far larger piston to bore clearance (approx double the OEM pistons)? This is like putting partly worn pistons into a brand new engine and will reduce the lifespan of your engine. In other words you can expect piston slap and compression blowby far sooner if you use forged pistons. A lot of people simply dont realise this fact (I didnt 2 years ago), and it is for this reason that I am using the 'semi-forged' items that Mahle make as I only want approx 420 BHP. The Mahle ones have been proven to cope with 450 to 500 BHP in several cases that I know of, and in Klassen's case have been taken to over 600 BHP. In short, buying forged pistons for a Z20LEx block is a BAD thing unless you want to run crazy power. Nev.

Edited by Nev, 10 November 2010 - 11:52 AM.

[Winstar]

In short, buying forged pistons for a Z20LEx block is a BAD thing unless you want to run crazy power.

It depends what your going to use your car for, the reason they need a bigger clearance is that the material expands more when it gets hot so if you treat the car right (i.e.let everything warm up at idel before giving it some) then the pistons will have expended to the correct size. But you can't just fit forged pistons and treat it like a production engine.

Edited by Winstar, 10 November 2010 - 11:59 AM.

[siztenboots]

In short, buying forged pistons for a Z20LEx block is a BAD thing unless you want to run crazy power.

It depends what your going to use your car for, the reason they need a bigger clearance is that the material expands more when it gets hot so if you treat the car right (i.e.let everything warm up at idel before giving it some) then the pistons will have expended to the correct size. But you can't just fit forged pistons and treat it like a production engine.

is this still the case, with the forged pistons now adopting the same silica plus nickel alloys, don't you get a lot of the thermal expansion benefits that cast pistons have?

Yet, but its nature a forged much be much heavier than its cast item, to its advantage its cheap to manufacture as a generic blank then machine down to order.

[chris]

My engine block is new (less than 1000 km) and the bores are within the tolerance given for the Cosworth pistons 86,000 to 86,010 mm.
My measures for the 4 cylinders are between 86,002 to 86,005 mm, so it is
not necessary to rebore the engine.

On the other hand, I don't want to install a "big" turbo (with significant lag) on my car 310 hp with 840 kg is enought for me. (A big power need also an increase of the piston clearance)

To be clear today I know the weight of my new piston and conrods:

Piston : 318 g + 50 g (estimative to axle + ring)



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Conrod : 552 g



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ARP screw : 2x28 g

Total 976 g (to be accurate I will weight axle and rings)

today, I need to know the weight of the same OEM piston + conrods installed in the Z20LEH, in order to know the weight to be removed on counterweight of the crankshaft.

So if somebody could give me these exact Z20LEH weights I would be grateful to him.

Edited by chris, 10 November 2010 - 12:17 PM.

[Winstar]

is this still the case, with the forged pistons now adopting the same silica plus nickel alloys, don't you get a lot of the thermal expansion benefits that cast pistons have?

All depends on the material spec of the pistons I was assuming Nev had researched the cosworth pistons.

today, I need to know the weight of the same OEM piston + conrods installed in the Z20LEH, in order to know the weight to be removed on counterweight of the crankshaft.

So if somebody could give me these exact Z20LEH weights I would be grateful to him.

Chris

What Alanoo was saying above was that when the Hoffmans Europa (using arrow rods and LEH pistons) was dynamically balanced at vibration free then found that they needed to add tungsten inserts to the counter wieghts to improve the balance and even then they could not add enough

Edited by Winstar, 10 November 2010 - 12:26 PM.

[siztenboots]

is this still the case, with the forged pistons now adopting the same silica plus nickel alloys, don't you get a lot of the thermal expansion benefits that cast pistons have?

All depends on the material spec of the pistons I was assuming Nev had researched the cosworth pistons.

CS quote 2618 alloy

The 2618, highest strength for the most serious race applications, has less than .25% silicon and a high expansion rate. The 4032, for milder applications, has 11 to 13.5% silicon and has an expansion rate similar to standard cast pistons. Hypereutectics, which typically have 16.5-18% silicon, are among the lowest rates of expansion. This amount of silicon is not used to make the aluminum stronger. It is used to reduce expansion by rejecting heat.

[chris]

is this still the case, with the forged pistons now adopting the same silica plus nickel alloys, don't you get a lot of the thermal expansion benefits that cast pistons have?

All depends on the material spec of the pistons I was assuming Nev had researched the cosworth pistons.

today, I need to know the weight of the same OEM piston + conrods installed in the Z20LEH, in order to know the weight to be removed on counterweight of the crankshaft.

So if somebody could give me these exact Z20LEH weights I would be grateful to him.

Chris

What Alanoo was saying above was that when the Hoffmans Europa (using arrow rods and LEH pistons) was dynamically balanced at vibration free then found that they needed to add tungsten inserts to the counter wieghts to improve the balance and even then they could not add enough

If you remove weight from piston and conrods you have to remove some weight (to be calculated) on counterweight.

It was the case of the Hoffmans Europa, I have photos which shown that some weight has been removed from cranksaht counterweights.
But may be they have removed to much and they need to put inserts to balance the crankshaft ...

Someone who knows the weight of the OEM Z20LEH piston and conrods ?

I don't care the strenght of these "tuning" pistons I just use this car to buy my bread !

Edited by chris, 10 November 2010 - 01:31 PM.

[Duncan VXR]

Winstar are you able to give you views based on the material used by cosworth after Steve's comments? It all makes sense to me but interested in exact info before boring the block. No LEH pistons my end will try to get the rods weighed if I have time Do we have any proof of these pistons actually causing issues and if so were they installed correctly? I think its a good point made by Winstar about the importance of warming up the engine and in my experiance the more you get involved with precission parts and different materials the more important this becomes Same as running an engine in - sitting at 3k for 1k miles is not running in and if anything glaze the bores there are correct ways of bedding things in and running engines and this does change when you start to move away from full oe spec DG

[Duncan VXR]

If you believe my kitchen scales they state 645g Need to get it on some super scales to be 100% sure though DG

[alanoo]

Chris, Your piston pin will be a lot more than 50g alone A good N/A pin is around 80g, a boosted one has more wall thickness and I'm sure it will be around 110g 318g is not bad for a forged boosted piston. Cosworth and almost all other forged piston makers uses 2618 alloy which yes expands a lot and gives a lot of slap on cold starts (which wears the liners, the skirs, the rings...), but this is honestly not as bad as you think (especially with coated pistons) if you do not use your car on a daily basis (or bread buying trips ). EDIT : for anyone running forged pistons, NEVER use less than 100µm piston to bore clearance. Yes you will hear audible slap on cold starts, even if you use a 2618 piston with OE bore to piston clearance... do not forget more bore clearance = more power too

Edited by alanoo, 10 November 2010 - 05:09 PM.

[siztenboots]

there was a good and heated discussion about this going on over at LoT, with Randy, KingK etc. Sadly we never got to the end. But there are bits of it scattered about. http://www.scottishe...t&sd=a&start=15

[chris]

Chris,

Your piston pin will be a lot more than 50g alone
A good N/A pin is around 80g, a boosted one has more wall thickness and I'm sure it will be around 110g

318g is not bad for a forged boosted piston.

Cosworth and almost all other forged piston makers uses 2618 alloy which yes expands a lot and gives a lot of slap on cold starts (which wears the liners, the skirs, the rings...), but this is honestly not as bad as you think (especially with coated pistons) if you do not use your car on a daily basis (or bread buying trips ).


EDIT : for anyone running forged pistons, NEVER use less than 100µm piston to bore clearance.
Yes you will hear audible slap on cold starts, even if you use a 2618 piston with OE bore to piston clearance... do not forget more bore clearance = more power too

You are right I have underestimated the weight of the axle, the real weight is of 101 g :



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I have also to add the weight of the rods bearing : 154g /4 = 38 g





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And the rings : 73g /4 = 18 g



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The total of Conrods + piston + ARP screw + axle + bearing + ring = 317 +552 + 56 + 101 + 38 + 18 = 1082 g


I already have asked the question to Courtney who sold me these item, but there are unable to answer me, It is very stange that nobody make this exercice before.
It seems to me important to know what is the difference of weight between OEM items and these tuning item (especially for the reputed tuner who sold them !)

It is a technical devices !