Stock, stroker or ghetto capacity increase? ( supra 7m gte pistons bmw rods )

[Rusty]

You have to have the crank machined so you might as well increase the stroke a little. Cost wise, I can't see why it would cost that much more...

[s2_wot]

http://shop.afterbuy.de/public/print...%20Kurbelwelle ghetto price

[Rusty]

Nice. It would be interesting to know is a stock ABY crank could be used, as an ABY short block with worn bores is hardly expensive.

[K Simmonds]

Hmm, I'll have a spare NG 2.3 block and crank soon, better start looking out for the rods and pistons second hand.

[prj]

I built this engine for this red Audi S4 that was now tuned by PRJ.

In this engine there was used MC crank and it was just milled to fit the BMW rods. Stroke stayed the same 86.4mm. Also it uses BMW NA rod bearings. (I have used 1.8 golf rod bearing on my own engine that pushed about 400kW from wheels. So dont worry people so much about the rod bearings.) I think in this setup you can go up to 7500rpm as you can with the stock pistons.

It is possible to build small block stroker with these pistons, again with BMW rods and diesel crank. The crank has to be eccentricity milled to about 94mm. Even then the pistons must be modified to clear oil squirters, but you dont have to mill down the pistons. Then you can have an engine that has about 2.54L of capacity and 8.0 compression (83mm bore and 94mm stroke). But i would not recommend to go over 7000 rpm with this setup.

Thanks for the info, I was wondering when you would finally chime in

[Rusty]

I was searching and found that M54 rods at 145mm should have the same big end as an M50.

http://www.arrowprecision.co.uk/rod_stock.php

There are also 140mm rods, that should allow for a little more stroke on the Audi crank, due to a 48.01mm big end vs 50.61mm on the Audi ones) allows an extra 2.6mm stroke at the limit = 86.4+2.6 = 89mm... in theory.

[Mcstiff]

654hp 764nm in engine on e85

7a engine, std 7a pistons, std rings(old rings)
everything standard 7a except gasket, rods and fuel....

did i mention its from sweden


so i guess using std 7a pistons isnt a problem.. 10.5 in cr, just use e85..

I am going to need more info on this! CR lowered with thicker metal head gasket? I have been beating the 7aT drum for awhile now, I'm about to build one with a Holset and E85.

[rst]

I was searching and found that M54 rods at 145mm should have the same big end as an M50.

http://www.arrowprecision.co.uk/rod_stock.php

There are also 140mm rods, that should allow for a little more stroke on the Audi crank, due to a 48.01mm big end vs 50.61mm on the Audi ones) allows an extra 2.6mm stroke at the limit = 86.4+2.6 = 89mm... in theory.

That combo dosent work very well. Because then the pistons are about 3,3mm down from the block surface. The rough calculations say that the comp will be below 6,9 because i didnt take account the bigger piston dish that supra pistons have.

As i have noted, the best "ghetto" build is still leave the 86.4mm stroke IF you want the easiest rebuild. Usually worn blocks dont cost much. So you can make a new engine for a very small money. New pistons with rings incl shipping to Europe 100-120€, BMW stock rods 20-70€ from a junkyard, worn crank 50€ max.

Also a lot of people including me have used stock Victor Reinz head gasket with 82.5mm bore with 83mm pistons. The pistons must just clear from the top of the block at least 0.5mm. After examining the head gasket of one of these setups, it had no marks on it.

[Rusty]

The shorter rods were for a longer stroke... you could deck the block a little to make up the difference but things start to get a little more complex when you do things like that, as the cam timing needs to be corrected

Always a good idea to work through a solution and then you realise why certain decisions were made or why onhe thing work better than another

What do you think the the M54 rods? They're fractured instead of machined... must be some reason for it

[diesel des]

What about these in a long block tdi with tdi crank. You would just need custom rods but what length...

[Rusty]

Got to thinking a little more about this, so decided to actually do some more calculations about what was required to get what compression ratio etc. I've attached an excel sheet showing my calcs...

I've done 3 versions, so that one piece of information can be used to calculate the other 2 - compression ratio, piston skim & piston stick through (-ve = below deck).

The rest of the data can then be entered below. If the piston stick through is more negative than -0.5 then an 81mm HG could be used...

I see that FCP do 144mm rods with a 22mm little end bearing...

[Error404]

You've got the rod length as 145mm, is that as you have factored to offset bore the small end out to 22mm?

[Rusty]

Read the rest of the thread... BMW rods used with Supra pistons. BMW rods used are 145mm.

Of course, with the correct information, the spreadsheet can be used for anything.

[Error404]

lol, ok my bad I'll have a read

[Rusty]