38 replies to this topic

[Winstar]

for completness I finally found the link to the Hofmann Europa build clicky

[chris]

Thanks for this link.

The pb with Hofmans Europa preparation is that basis of this preparation was a Z20LET engine
Crankshaft is heavier than on the Z20LEH, and when you remove (by machining) the gear which drive the balancing shafts, you badly dammage the "balancing".

Moreover installation of Z20LEH oil spray under piston on Z20LET block "is not easy", but this solution is better than "to improvise" adaptation of Diesel engine oil spray on the top of the existing bearing as we can see on the web.

IMO Z20LET engine is not the best basis for Hi-power preparation it is the reason why I have choosen a Z20LEH.

As written in my first post of this topic, I have removed the difference of the rotating weight part of the conrods on the counterweights of the crankshaft by machining.
I have "lightly polished" it, Then it was sent to specialized company in order to be balanced.
It was not necessary to add tungsten weight, only 5g and 10g was removed by grinding in two plans to balance this modified crankshaft.



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Now I can re-assemble the engine.

(despite the fact that Courteney don't answer anymore to my questions)

[coople]

I think in allot of cases this extra balancing effort is overlooked. You are basically creating a fully blue printed engine by doing this. Nice work.

Balancing

[cnrandall]

Thanks for this link.

The pb with Hofmans Europa preparation is that basis of this preparation was a Z20LET engine
Crankshaft is heavier than on the Z20LEH, and when you remove (by machining) the gear which drive the balancing shafts, you badly dammage the "balancing".

Moreover installation of Z20LEH oil spray under piston on Z20LET block "is not easy", but this solution is better than "to improvise" adaptation of Diesel engine oil spray on the top of the existing bearing as we can see on the web.

IMO Z20LET engine is not the best basis for Hi-power preparation it is the reason why I have choosen a Z20LEH.

As written in my first post of this topic, I have removed the difference of the rotating weight part of the conrods on the counterweights of the crankshaft by machining.
I have "lightly polished" it, Then it was sent to specialized company in order to be balanced.
It was not necessary to add tungsten weight, only 5g and 10g was removed by grinding in two plans to balance this modified crankshaft.

Now I can re-assemble the engine.

(despite the fact that Courteney don't answer anymore to my questions)

The design of the LET/LER(europa engine)/LEH crank and block are virtually identical. The LET/LER crank has additional metal where the ring gear is and removing it doesn't damage the balancing at all. It's nice that the spray jets on the LEH block are there although they aren't *that* hard to retro fit and there are also more ways than one to skin that particular cat. I've heard from a friend involved in the casting industry that the LEH is made in a different foundry and the quality of the parts aren't so good, not sure how significant this is although I do know that my engine is reliable at 480bhp and 7800rpm with the LER block and crank. One part of the LEH that I do believe is a benefit is the head, which has better cooling and hence better knock resistance.

[Jon]

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 !

Hi Chris I might be a bit late, however I saw this at the weekend which was good timing as we changed a set of roads on an LEH last Thursday, so here are the weights you needed.

LEH Rod inc Bolts 697g
LEH Piston inc Pin and Rings 454g

Total 1151g

Any other info drop me an email @ jonshield@courtenaysport.co.uk, regards Jon

[chris]

Weight of Cosworth piston + Conrods assy : 1049 g => 100 g x 4 saved :



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Edited by chris, 20 December 2010 - 11:49 AM.

[chris]

Thanks for this link.

The pb with Hofmans Europa preparation is that basis of this preparation was a Z20LET engine
Crankshaft is heavier than on the Z20LEH, and when you remove (by machining) the gear which drive the balancing shafts, you badly dammage the "balancing".

Moreover installation of Z20LEH oil spray under piston on Z20LET block "is not easy", but this solution is better than "to improvise" adaptation of Diesel engine oil spray on the top of the existing bearing as we can see on the web.

IMO Z20LET engine is not the best basis for Hi-power preparation it is the reason why I have choosen a Z20LEH.

As written in my first post of this topic, I have removed the difference of the rotating weight part of the conrods on the counterweights of the crankshaft by machining.
I have "lightly polished" it, Then it was sent to specialized company in order to be balanced.
It was not necessary to add tungsten weight, only 5g and 10g was removed by grinding in two plans to balance this modified crankshaft.

Now I can re-assemble the engine.

(despite the fact that Courteney don't answer anymore to my questions)

The design of the LET/LER(europa engine)/LEH crank and block are virtually identical. The LET/LER crank has additional metal where the ring gear is and removing it doesn't damage the balancing at all. It's nice that the spray jets on the LEH block are there although they aren't *that* hard to retro fit and there are also more ways than one to skin that particular cat. I've heard from a friend involved in the casting industry that the LEH is made in a different foundry and the quality of the parts aren't so good, not sure how significant this is although I do know that my engine is reliable at 480bhp and 7800rpm with the LER block and crank. One part of the LEH that I do believe is a benefit is the head, which has better cooling and hence better knock resistance.

When I have written that the machining of the "ring gear" damage the balancing of the crankshaft, I mean that it is more difficult to restore it. The evidence is that you have added a tungsten weight to restore the balancing of your crankshaft.
Of course, your crankshaft is "globally" perfcetly balanced, but I am sure that cylinder which correspond to ring gear you have removed is "unbalanced" and this particular point is very difficult to correct.

Regarding the cylinder head, according to the references in the Opel EPC software the number for standard exchange is the same for the two engines type.
Externaly there is no visible difference, so in my opinion the heads should be the same for the two engines, to be confirmed.

Edited by chris, 21 December 2010 - 12:06 PM.

[cnrandall]

I've not added tungsten to my crank because of the cost... may as well get a new crank designed and built! Interested to know how you worked out how you needed to remove weight from your counter balances? The way I did it was to get a donor crank and cut off one part of it to run single cylinder tests and we found that the crank was under weighted. The saving grace is that the cast Vauxhall block is very stiff and can clearly cope with the bending load created by the inbalance.

[chris]

As a rule, the crankshaft counterweighs are designed to counterbalance the force of spindle and of the "rotating part" of the conrods, during the rotation of the engine.

If you replace conrods by lighter one, and if you wish the keep an equivalent "level of initial intrinsic balancing" of your crankshaft, you have to remove "some weight" on the counterweight
(to be calculated with the help of some complex softwares models or estimated with more simple empiric models)

Of course you could remove completely the crankshaft counterweight, (some crankshafts of plane engine don't have counterweights) but despite the fact that your crankshaft (without counterweights) can be perfectly balanced, you induce some local force which distort the crankshaft itself.

According to this principle, I have choosen to limit the deformations of my crankshaft (despite the fact that Z20Lex block is "very stiff")

In consequence, I have removed weight to on the counterweight, with the help of a lathe.



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Then, The crankshaft was balanced.

As you can read on the balancing certificate, a removal by grinding, of only 5 and 10 g was necessary to restore a good balancing level of this crankshaft.




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Edited by chris, 22 December 2010 - 05:50 PM.

[cnrandall]

OK... so you made the assumption that the counter weights were correct to start with... you know what they say about assumptions ;-) Remember that this basic engine design goes back for more than 30 years and was, first conceived as a lower capacity unit. Remember also, that manufacturers design to a cost and the basic crank design is shared over many different models and engines so isn't exactly ideal for our particular application.

[alanoo]

Randy is right about this, the only way to get an accurate secondary order balance is get a crank on a mono cylinder bench and learn

[chris]

Alanoo, I think you mix the matters. The "secondary unbalancing order" is linked with the "alternative movement" of the conrods and pistons. But you are right regarding the method to determine the balancing factor of this crankshaft and its associated internals, but unfotunately I don't have a crankshaft to sacrify. Randy you made also some assumption regarding my purpose for this engine. I don't want to make a 1/4 mile race car, and I will never install a big Garett turbocharger on it. I think there are another ways to get a reasonable power (saying 350 Hp) without to make an on/off engine with a nominal power up to 7000 rpm and with a torque curve wich begin to increase only @ 3500-4000 rpm. But may be I am wrong, but its my choice (today) ...

Edited by chris, 23 December 2010 - 03:48 AM.

[cnrandall]

That's not an assumption I made. My engine is very progressive and has 480bhp... it's all possible.

[chris]

Do you have a Power/Torque curve to show us ?

[siztenboots]

[cnrandall]

Do you have a Power/Torque curve to show us ?

This is power @ the hubs: http://www.dyno-plot...HofmannsTDI.htm

And here is a vid of it so you can see from the cockpit

She is a pussycat!

[chris]

Your curve is a typical curve of big turbo, with a max torque @ 5000 rpm and max power @ 7000 rpm !

My purpose is to get that :



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Of course there is less power, but torque curve seems to me, more interesting.

Edited by chris, 23 December 2010 - 05:18 PM.

[cnrandall]

suggest you buy a diesel ;-)

[chris]

It is not possible, diesel engines are too heavy !