Bit ahead of you :-|

You can stay there fella I'm happy with that

surely there must be a sensible priced stroker kit as 400cc per cylinder is a weak base from which to get power unless you are hunting a revvy engine, unsuited to everyday driving?

If sufficient interest was available and a suitable stroker kit could be compiled at favourable terms and a specialist could treat the job as a stack em hi and price em low part of their business to do conversions in any 'free time' / sub con it ..then wouldnt say 500 cc / cylinder (assuming practical with std bore) provide better drivable power, especially low rev torque response for easy overtaking - whilst maintaining safer boost levels on a smaller more responsive turbo - Also help maintain performance off boost, giving more efficient economy with everyday driving.

I am sure on boost power would not disappoint, even with modest breathing enhancements

I appreciate I talk from the position of a complete novice, however I would be interested to hear from those involved in performance engineering, particularly those abroad who may have better access to sensibly priced components / machining - custom crank + aftermarket rods do the job? - Rods neednt be too long as cr could no doubt be dropped a little due to capacity compensating off boost and adequate boost applied to make use of lower cr on boost (again lower cr off boost enhancing economy further?)

All very theoretical as I know nothing about the intricacies of perf tuning but very keen to see if above has any mileage if sufficient interest - eg cost of initial custom crank shared out across say ten customers placing deposits, with cheaper re-order pricing offsetting need for orders of tens - with modern CNC machining a small engineering co. would probably be happy with twos subsequently with parameters stored and unit tested.

More thoughts along these lines / above would be useful as not everyone wants to chase megahorses at considerable cost with road unfriendly characteristics.

I guess most would be happy with say c 390 bhp and wide powerband with near max torque other std components can take (excl clutch) available from say 2.5-6k - incidentally what are the limiting areas for say 310-360 lb ft and can any be addressed cheaply when above work carried out?

OK, I shall stop waffling now...

No need for a stroker kit to achieve that

Name me any engine where you can get a stroker kit cheap - except maybe the Beetle which being air cooled doesn't really count (less complex)

Thing is, if you have a crank with a larger stroke, you need shorter rods. Cranks are expensive to make, especially if you have to design and make the tooling as well, so the Stilo/kappa 2.4 crank (as in "here's one Fiat prepared earlier" gets used. Still costs silly money for custom rods - and even thjough we use 5 at a time, the market isn't going to get past 20 sets (which again in terms of recouping tooling costs is nothing)
Much of the exense for most who can't do it themselves, is the labour for the engine rebuild, so might as well go forged for what little extra it costs
And you won't take any advantage of the extra capacity running everyelse (injectors/turbo/ecu especially) as stock - so another byundle of money needed
Which is why those of us who have gone to 2.4/2.5 are still few and far between and have invested far more than we want to own up to

Just my thoughts - if we all drove round in something properly common, like a Fiesta, there might be a market for something, but when did you last see a Coupe that wasn't yours? These days Astom Martins are more common spot

It's a nice idea but as mentioned the likely hood of getting the numbers together to make a big enough purchase would be a struggle.
If, and it's a big IF, there was as many as 10 sets the price I'm sure could be got considerably cheaper. I'll recklessly throw a number out of £2000 region for custom crank, rods and pistons. These would be for top quality parts and no messing about with unknown materials and manufacturers, you could get creative and make a special setup. You could sell your soul to china for a fair amount less but not a great idea IMO. You'd need full payment for all products ordered, no room for sitting on the fence in that type of a group buy.

Unless your into a dedicated build (more money than just a crank setup) I'd believe the best improvement would be seen in the intake system (one part upgraded means the rest need it to achieve the potential).

I suspect most people wouldn't consider £2k as "cheap", and you'd still need to factor in as least as much again in ancilliary bits to take advantage

£2k isn't what some people would consider cheap but they might well be the same people who haven't bought parts for an engine build of ambition. It'd be a struggle to buy standard parts for much less I suspect. I don't mind paying strong money for stuff as long as I'm getting what I consider to be real quality and enhancing features, source them personally and sometimes the price is pretty good. I don't think we'll find anyone with an upgraded engine build who hasn't sunk more money than they first thought they would, it's an expensive task no matter how you do it.

The gist of the thread I originally responded to was bemoaning the lack of a cheap option

Think I've spent more than enough money destruction testing Coupe engines to be very au fait with prices :-(

The thing is - you don't need a stroker kit to get a reliable 400bhp with a half-decent power band.

With the right turbo, you can get boost from 3,000 rpm all the way to 7,000+

yes - the 2.4 engines are producing monster bhp, but unless you're looking for 500+ bhp, there's just no need (unless you're also looking for other characteristics, such as better off-boost driving, or even earlier spoolup)

most wont need over 400 bhp, however if the engine is coming apart to strengthen for 350 + bhp, perhaps the hi-cap crank and rods, if inexpensive enough could provider a nicer torque band and less gutless off boost driving? - Again, personally it is much more useful for road driving to extend the power / torque band down 500 rpm at lower end than up 1000 at the upper?

The lower rpm performance can be worked on and improved without going to a larger stroke. Cr, improved breathing on either side of the cylinder, turbo's, camshafts would be as big an influence. Build it right and there'll be no worries about the lower rpm I believe
Stroke to the bigger capacity and get other areas wrong and you'll not see the benifit, you still have to fill the cylinder no matter how big it is, need to empty it too....
It's not a bad thing a bigger capacity but I'd say it's just a small part of a bigger picture that can easily be hindered by components that have nothing to do with capacity, don't ignore the whole.

^^ ^^

Cam choice and timing in particular has a HUGE influence on size and breadth of the power band. I think people in turbo circles often tend to get all hooked up on what turbocharger to buy and completely forget about cams. To me camshafts are the heart of an engine - and even more so on a turbo car. You can build the sweetest spec'd engine ever but get the cams wrong, or don't spend time fine-tuning the cam timing to match the engine -and the driving style- and you'll end up with an car that's just 'not quite as good as it coulda/shoulda been'. That goes for any engine - no matter what the cubes.

Proper proper.

I believe it's important to lay out the targeted power/rpm and gather as much flowbench data as possible and hand this over to a trusted cam designer to grind what he is qualified to design (guy's that can do whole engines including camshaft design are very few in number, it's a specialist field). It's all too easy to have duplicate/generic camshafts that have no sympathy for the finer details an individual engine has. Even small changes on either side of the cylinder make for big differences in recorded infomation and the valve event can be tailored to complement ....

call me naive, but if cams can give a much broader power band in a stroke (scuse pun) then wouldnt every engine have a 2-7k power band for sporty road use? - As I understand it the profile/ overlap /duration etc mainly moves the powerband around in orchestra with valve / head and breathing design synced to timing?

eg this, put crudely typically results in pushing power band up rev band if hunting bhp and down if searching torque? - I dont see you appreciably expanding 'power' band and raising all - the black art of profiling / timing / breathing clearly brings some improvements in all areas through greater efficiency however, keeping capacity std (and for simplicity the turbo out of the equation) can you really re-profile to bring far greater power in at 2.5k whilst also giving free breathing and sensible improvements at upper rev end (under 7k)

Wouldnt a modern efficient quick spool low boost turbo linked to a 2.5 and modestly worked over head give far more pleasing results for road use - ie not having to drop two gears and re-spool for those rare brief overtaking opportunities on the narrow twisties?

Merely forwarding a possible tuning pathway for conjecture / debate not to be argumentative, as I mentioned I know nothing about engine design, but happy to explore different avenues if it opens up improved road performance for more individuals perhaps already faced with a re-build & turbo upgrade...

Sure, improving breathing in the intake and exhaust is the best route. As you say, the cams move the power band about (duration does anyway) and you can't have it all ways but that's not to say you can't improve lower rpm performance on an engine that has a cam that can breath at higher rpm too. Getting the air velocity in the inlet ports to a decent level at lower rpm will help a lot, grind out ports too big or bad shape and you'll need to wait longer for the main event. It's no single component that will make a great engine, it's the sum total of the whole that matters and tayloring it to suit your expectations/ambition, the valve event plays a big part in that, more so than capacity I believe. You could have a 2.5 and louse up the cylinder head, manifolds or systems leading too and from them or fit crazy big cams and you still have a lag laden engine. It's a good idea IF you achieve the balance.

I know next to nothing about the parts available for the 20vt, is there much in the way of choice when it comes to cams? Or is it just a select few profiles that are available? That was the problem with the 16v engine I like and why I scoured the earth for cam cores to grind bespoke.

Griffster:
In addition to the above: Cam timing also has a huge effect on when the turbo spools and how much torque is made when it does spool.

As an example, check out the little writeup I did on the my findings on the effect of timing on torque & power (bottom of the page). Note that it's exactly the same setup, exactly the same boost, the only thing that changes is the cam timing. Pretty significant as you'll see.

I should add that in the end I chose timing somwhere between that of runs 3 and 4, on that setup.

http://www.fiatcoupeclub.org/forum/ubbthreads.php?ubb=showflat&Number=1191994

So my hope for 2013 is that people will start thinking about their engines as a whole, instead of just getting hooked up on turbochargers and boost.

Sometimes it can be very difficult to get through to some folks that, just having some nice forged pistons and a big turbo does not automatically mean that their engine will make a bajillion bhp. Sure, these are important, but they're just 2 parts in a system. Without all parts working together, complimenting each other all you can hope for is disapointment - whether it's 2 litres or 2.5 litres

iNRO:
Pretty much the same selection as the 16VT, so it seems - C&B and Cat Cams. Personally I've never really been impressed by C&Bs on the 16VTs I've seen or tuned - Perhaps they were just bad examples; others not custom timed and the one's I tuned were Race Min on a road car - definitely not a good road setup!

Anyway, I'm going to be stocking Cat Cams for 20VTs and 16VTs.

BTW did you ever find 16VT cores? I just happened to also have done some searching for the same a few months ago and it seems they don't exist, so all 16VT cams have to come from blanks - hence the high price relative to other makes.

so, what your saying is, apply a little voodoo?!

Yes, I see how profile and timing can feed more air to turbo earlier and encourage it to spool earlier - I reckon closer to 2.5k rpm for road use would make a big difference to road driving - the number of times we run sustained rpm over 5.5k on road is clearly minimal by comparison - I dont want an engine to choke up before 6 pref 6.5, however the usable power band needs to be focussed 2.5 to 5.5k?

So, that is pretty much what a standard 20vt does for it's powerband

In which case, stick to standard cam timing - just with more boost, some headwork and inlet/exhaust work if required.

having only driven one modified example I assumed 3k was full boost onset with a turbo upgrade - can you get full boost from 2.5k with say a 310 lb ft and 350bhp envelope?