Scottish Elises

randy:SELOC
Member




Posts: 87
Registered: 5-8-2008
Location: Henley on Thames
Member Is Offline


posted on 4-1-2010 at 04:19 PM


As you can see the ladder bolts to the back of the bearing caps and adds some stiffness to the bottom of the block. Only the more recent turbo engine run this ladder and plenty of people just remove it as general consensus is that it's only to help NVH but I feel that if you have over 400lb ft of torque out of a 4-pot engine then you need all the block stiffness you can get!

We run 1.6bar of boost and in GT trim and rev to 7500rpm. In Lotrdc trim the boost varies continuously so we can straight line the power graph and also I rev it to 7750rpm when If it helps me save a gearchange.

Running the stock pressure stage doesn't really complicate things... In fact it probably make things simpler. I'm expecting to loose weight out of the system as the crank ladder and wet sump are heavy and the oil/air separator allows me to keep the oil volume down to 5/6litres. Pumping losses aren't an issue for me...



[Edited to correct image tags]

What's your point caller??

I don't know how much work you have done to assess the counterweighting on that crank?, So forgive me if this is treading familiar ground;-


That crank has very wide cheeks, and not the biggest counterweights either, the engine I am guessing has very heavy pistons too? 400g+?

it may well be very undecounterweighted because of space/production limitations, but it is common practice to use balance shafts to counteract primary forces of axial unbalance as well as secondary forces of unbalance.

Take a look at the 2 honda K20 cranks

this first from the K20A


this second from a K20Z4



you can see the newer engine has fewer counterweights -

honda have done this to reduce the very considerable weight of the k20 crankset to improve responsiveness - obviously, but they have offset the [primary] axial inertia forces with the use of the balance shafts, which ALSO act against the secondaries caused by the very heavy honda piston mass. This is a costly [ balance shafts obviously are a big cost add on in a production engine] but has the advantage of making the K20As successor a much much smoother but also freer revving engine. Trouble is if you remove the shafts, not only will you reintroduce the vibration that happens at a frequancy twice that of the engine speed, but you introduce primary vibration that will cause the engine to bounce - unless of course you fit very much lighter pistons.


So looking at that set up I think you are right to want as much stiffness in the block as you can get, I am not sure the balance shaft frame is going to contribute much, but replacing the caps with an integrated sump/crank carrier would be a very neat solution. There are the machining issues to consider but they are not insurmountable. Millington made a casting like this for their 2L, and it is common practice in contemporary F1 where of course undercountereweighted cranks are the norm - generally 30%.

As you know I am not an advocate for the absolute necessity of running ideally counterweighted cranks in a track engine or road engine, there has been a great deal posted on seloc that is misleading on the subject concerning K series, and some of the early empirical work done to modify these cranks was badly flawed, but hanging onto the crank is the most important thing and the further you move away from ideal counterweighting the more stiffness you need, plus at 7750rpm you are using some revs too.

Anyway maybe this is all well trodden ground for you, but if not I hope it helps

These spambots have managed to become a bit more sophisticated and on topic

am i the only one to think this is all a bit random?

r055 wrote:am i the only one to think this is all a bit random?

It is an attempt to continue a perfectly civil and I hope useful conversation that got stymied elsewhere - in part for being unable to post pics

Probably best to do what Robin suggested for the spambot threads.

Dan

Probably the only forum left that Simon Erland (King K) hasn't been banned from. As the info may be of some use to Honda owners or those of us running hairy Ks, then it's welcome.

However, the mods are aware of King K previous posting history on other forums - which have almost always led to bans from these sites for flaming. The Mods will be monitoring this thread very carefully in case Simon's old 'style' surfaces again. Please read the guidelines for the expected behaviour in this forum, Simon.

I personally hope that action won't be necessary.

KingK_series wrote:

r055 wrote:am i the only one to think this is all a bit random?

It is an attempt to continue a perfectly civil and I hope useful conversation that got stymied elsewhere - in part for being unable to post pics

This isn't a proxy forum - if you are interested in contributing to the Scottish Elise scene, then you're welcome here, if it's just to use the forum as a picture resource, please don't let the door hit you on the way out.

If you think this is going to be a suitable site to continue one of your infamous 'debates', you'll be disappointed.

Damn, I was hoping for a fight, it's been fairly quiet with all this snow stuff getting in the way.

kenny wrote:Damn, I was hoping for a fight, it's been fairly quiet with all this snow stuff getting in the way.

whose fighting?

I see this thread has been resurrected on the Elise Trophy twitter, might be worth locking it before it kicks off!

Completly Random but interesting.


Alan

Gourlay83 wrote:Completly Random but interesting.


Alan

That has to be one of the rudest (mis)uses of a community forum I've ever seen.