Randy's post on crank counterweight and balance shafts

[Randy]

I agree entirely, unless you substantially lighten the pistons and then modify the crank to suit.

As I have already said... the setup I have is Vauxhall Z20LEH which has lighter pistons than the Z20LET or Z20LER as standard (about half the weight) and no balance shafts. Mine also has rods which weigh half the OE ones...

[steve_weegie]

the setup I have is Vauxhall Z20LEH which has lighter pistons than the Z20LET or Z20LER as standard (about half the weight) and no balance shafts. Mine also has rods which weigh half the OE ones...

Gotcha - I thought you'd removed the shafts from the standard engine like some Saab folk do, hence my interest

[steve_weegie]

I agree entirely, unless you substantially lighten the pistons and then modify the crank to suit.

On the proviso that no matter how well matched the crank / rod and piston assembly is, you'll always remove more 2nd order harmonics with the right crank / rod / pistons and a pair of balance shafts

[Randy]

the setup I have is Vauxhall Z20LEH which has lighter pistons than the Z20LET or Z20LER as standard (about half the weight) and no balance shafts. Mine also has rods which weigh half the OE ones...

Gotcha - I thought you'd removed the shafts from the standard engine like some Saab folk do, hence my interest

No, I took pretty good advice on the bottom end before making any changes... mostly from Steve @ Vibration Free. It's actually quite common to remove the balance shafts on the Z20LET engine though and this doesn't appear to create any ill effects. On the Z20LET it's the pistons and rods that are the weak link and not the crank and some people spin that crank to 8500rpm plus with a decent piston/rod combo.

[steve_weegie]

Sounds like a winner Randy... Fingers crossed it will bring you much success

I guess if you've retainted the standard turbo (K04?) You'll be able to dial in a lot of boost from around 2.5k to flatten the power curve. What management are you running the car on? Any tweaks to help spool rate, or is this not a problem?

Oh, and can you drop one into an Elise yet?

[mckeann]

Steve,

Randy did an excellent blog of his build and it lists all the specs:


http://www.hofmannsofhenley.co.uk/conte ... .asp?id=63

[steve_weegie]

Steve,

Randy did an excellent blog of his build and it lists all the specs:


http://www.hofmannsofhenley.co.uk/conte ... .asp?id=63

Aah

Cheers Neil

[Randy]

Sounds like a winner Randy... Fingers crossed it will bring you much success

I guess if you've retainted the standard turbo (K04?) You'll be able to dial in a lot of boost from around 2.5k to flatten the power curve. What management are you running the car on? Any tweaks to help spool rate, or is this not a problem?

Oh, and can you drop one into an Elise yet?

Already is a winner Quickest car in LOTRDC in 09 and since then I've upgraded to GT Cup where it finished 2nd overall in it's first outing... only beaten by a GT3 Dodge Viper.

No way would I run the stock turbo as is completely unsuitable for race use. I'm running a Garrett GT3071R with bespoke exhaust setup and chargecooler setup, running about 420bhp. Management is Solaris S6 and all the electronics were done by TDI in Thurrock.

[KingK_series]

I agree entirely, unless you substantially lighten the pistons and then modify the crank to suit.

On the proviso that no matter how well matched the crank / rod and piston assembly is, you'll always remove more 2nd order harmonics with the right crank / rod / pistons and a pair of balance shafts

Absolutely correct, but what some people don't seem to have caught onto was that Shafts can be used to counteract primary axial inertia forces too, and in the honda K20 that is very useful since it has such a very heavy piston, which in the K20A causes the crank to have to be extremely heavy - 17kg, and there are still massive secondaries - hence honda redesigning the engine as the Z4 which must go a lot better.

The downside to shafts is not so much dead weight, it's only an additional 5kg in the K20Z4 and you are losing 4kg from the crank , so there is only a 1kg nett gain in an already very heavy engine, but it is also the extra frictional losses - which some estimate at about 15bhp, though personally I am a bit skeptical about that, but the extra mass to rotate.

So in a race engine, it is not desirable, but these issues need to be considered, and they seldom are - much better to my mind in having a properly designed race piston and rod, and crank designed for that rod and crank, - that is what I have done.

I'll answer some of your questions about breaking cranks Randy in a bit, need to sort some pics, and my mother has just broken her leg again on the ice, so bit stressed here.

[Scotty C]

Quickest car in LOTRDC in 09 running about 420bhp.

I wonder why

Just need to sort out the corners and you be alright

[Randy]

Because I built the best car in the series? I know people around the the pits have there little rumors about the power I ran but I find that laughable, just look at some of the footage of the rolling starts. Considering on paper the 211's have by far the best power to weight and aero I don't think kicking your arses is two shabby? Even managed to turn quickest lap at brands with 'storm' setup and engine glitch caused max revs of 6250 down from 7750

[Scotty C]

Because I built the best car in the series? I know people around the the pits have there little rumors about the power I ran but I find that laughable, just look at some of the footage of the rolling starts. Considering on paper the 211's have by far the best power to weight and aero I don't think kicking your arses is two shabby? Even managed to turn quickest lap at brands with 'storm' setup and engine glitch caused max revs of 6250 down from 7750

lol

think you better look back the results. I don't see you FINISHING to many races ahead of me

My screen saver is a very nice pic of me going round the outside of you at silerstone in my first ever race meeting. I know you had car issues but i don't give a sh1te i was on cloud 9.

Don't get me wrong, I look up to you in so many ways and racing against people like youself is one of the reasons i went racing. Mucho respect to your race prep, car set up and car control. I wish I had the money to do the same.

all the best next year in the GT cup. I hope we race agian some day.

[Randy]

Because I built the best car in the series? I know people around the the pits have there little rumors about the power I ran but I find that laughable, just look at some of the footage of the rolling starts. Considering on paper the 211's have by far the best power to weight and aero I don't think kicking your arses is two shabby? Even managed to turn quickest lap at brands with 'storm' setup and engine glitch caused max revs of 6250 down from 7750

lol

think you better look back the results. I don't see you FINISHING to many races ahead of me

My screen saver is a very nice pic of me going round the outside of you at silerstone in my first ever race meeting. I know you had car issues but i don't give a sh1te i was on cloud 9.

Don't get me wrong, I look up to you in so many ways and racing against people like youself is one of the reasons i went racing. Mucho respect to your race prep, car set up and car control. I wish I had the money to do the same.

all the best next year in the GT cup. I hope we race agian some day.

Full respect for your performance in your first year. Would have loved to see what could have happened given the budget to chuck at the car on maintenance and upgrades

I'll have to strap you in the Europa at some point and show you how it all works, I imagine it's quite a different beast to the 211 and the lap time is arrived at in a very different way.

For what it's worth... my car actually cost less to build than it would have cost to buy a 211 but then I do appreciate I'm in a fortunate position when it comes to trade prices and good deals on parts (heads up to all my friendly suppliers ). Also, I would wager a bet that my annual budget isn't amongst the highest in LOTRDC by any stretch (remembering all the prep work is done by myself in my spare time). Perception is a funny thing, particularly in motorsport...