Rod ratio is the only plus I see of any benefit making the engine more square.
Its an improvement in that respect but such a small percentage increase that I can't see the benefit of losing 200cc of displacement worth while.
All this good stuff and not even mentioned combustion chamber design yet

 

I'm sorry I'd be totally unable to add any value to that discussion at all

 

Me neither

 

ian, what are you doing with your heads chamber wise?

 

New Bosch fuel pump landed today. This should feed plenty to the motor

 

I've got Zak's old MY05 JDM sti heads from the blob TA car so they have been matched to the 2.5 bore already, other than that stock...1mm oversized inlet standard I believe. Love to go super-tech and port\polish but I really want to drive it again and tbh its gonna scare the googlies off me with the 18g its been so long since I've driven it

 

Destroked as Ians you don't lose 200cc and there's a hell of a lot more to it than rod ratio.
I asked a UK company back In 2007 if they could source me the parts for a destroked build similar to Ian's; my request was as good as laughed off as it wasn't based on the 97mm/79mm and with time restraints for TA looming I opted for the 2.5 route. Mid 2009 I tried again from UK sources with no joy, seems certain parts to complete this route are now available although my engine's components were sourced further afield.

Should Ian ever decide to purchase the 'correct' turbo for the application, if there is such a thing, I feel the results will speak for themselves.

Re heads, I'd select the right cams before worrying too much on chamber design.

 

gearbox first big boy

 

Ian,

Appologies for not doing any calc when I was quickly typing a reply on a Blackberry. Your block being linered combats the obvious limitations of the stock 257 block of which I was refering to yesterday.
The difference in cc of the destroked motor is indeed less than 200cc.
The capacity of the stock 257 is 2.457l with a rod ratio of 1.652. The Crower longer rod gives a ratio of 1.667

The destroked 2.5 using a 99.5/75 arrangement gives a capacity of 2.332l and a rod ratio of 1.740. Indeed only a capacity drop of 125cc.

The stroked 2.2 22B block gives us a capacity of 2.359l

As for combustion chamber design. You only have to look at Duncan Grahams, Shaun fennings (worked heads but stock chambers) 2.5 motors to see the difference. Both use the correct 2.5 head and combustion chamber.
The chamber affects the tuning, power and flame front control over the entire rpm range. You gain in 100% of the powerband.
Its consistant to see that 2.5 motors built using the correct chamber design making more power much more efficiently and safely than any build just shoving stock 2ltr heads on a 2.5 block.
I don't belive that the cams at these levels are holding the motor back as much as the chamber is creating efficient power and burn.
I'm also more than happy with my cam choice for my targets.

I guess I'd best leave the engine design to the tuners who know far better than I to discuss engine geometry.

Best of luck with YOUR build Ian, I'm sure it will work very well indeed

 

I keep forgetting yours is a cdb 2.2 to 2.35 Rossy, really is an awesome machine a real credit to you. Have you got that harness bar in yet

That's mahooosive

 

gotta love the never ending debate over which engine is best in a scoob.......

 

on the money I reckon and just to confuse things a bit more mine is a 2.0 CDB bored and sleeved to 2.5 not a sleeved 257

Frayz I've got your catch can...swap it for a book you have

 

Should be suitably stronger than a stock 257 block then. Ripe for loadsaboost.

 

I'm still a bit confused about why you would liner a CDB...I've asked Steve so hopefully should find out soon. Gonna be gentle with the boost i reckon, once I get my proper blower-probably a billet GT30R-its going to raise my heart rate considerably at modest boost levels

 

.....a bit confused

Factory CDB was only available in 92mm (2.0ltr) and 97mm (2.2ltr) bore, you need a 100mm bore to reach your 2.4ltr target.

 

IMHO, you can't beat a 2.5ltr based road car, they need a 5speed or Hawkeye 6speed to extract the very best experience from them but the grunt, and therefore drivability make them an awesome experience on the road.
For circuit use I'd rather closely stacked gearing to match so all gears are used and an engine that will produce peak power at high rpm

For someone that wants both it's a question to selecting something suitable from the many engine configurations out there

 

That's why you are building the engine and not me...well allegedly anyways Seriously though, why sleeve a CDB

 

the rings need something to seal against or you'd have a distinct lack of compression. Enlarging a 92mm bore by a further 8mm would have your pistons swimming in the cooling system

 

makes sense, should have asked you earlier

Apologies for thread hijack Frayz

 

Tonight I managed to get 5 min to spend on the motor. So the cylinder heads have been fully assembled. Rewashed, final inspection, measure of all valves and guides and final cc check and then assembly of the valvetrain.

Everything was in spec and the final cc of the chambers came in at 54cc dead for all 4 chambers.

I'll post up some pics when i can, nice to get em done to be honest

 

53cc would have been better

Gonna order some of this to finish off a set of wheels I have, if your Speedlines/discs need a session when your done

http://www.cleanyourcar.co.uk/index....&productId=726

 

I've told you before you need to warn us before posting actual progress!
You know the shocks not good for me old ticker

 

Haha, w@nkers!

Neil, i thought you might enjoy the fact that i have actually started the engine build. maybe i should have text you to per-warn you beforehand.

they look lush, i'll get some pics up soon

 

looking forward to seeing the pics

 

Frayz - good to see the progress - if the heads only took 5 minutes then the bottom end should only take 10 minutes.. ish..

Ian - sounds like yours will be able to handle big power! And yes, when you get back in it after a long absence it will blow your socks off (even before your 'proper' turbo)!

Cheers fella.. taken way too much money and frustration but that's what happens when you end up paying for things to be done twice .

Not yet with the harness bar, haven't even picked it up yet . Going to try some matt black wrap on the boot lid this weekend instead of the carbon as I still haven't the funds to have it painted properly what with said expense - will post some pics up when done. Let me know how the Iron Cut product goes, PB rate it highly!

 

Lol bottom end could be more like 15min

 

Pre warning for Neil, expect a substantial update tomorrow

 

Thanks, don't like shocks at my age, look forward to tomorrows update

What time shall I pop round to hear it fire up?

 

Well lets just say im working lates this week but will be having a very early start tomorrow

 

cant wait to hear & see all this come together