salvator_rizzo

iTrader: (7)

So for the next swap I do I think I want to do a 2.0 stroker with a decent size turbo on there, maybe shooting for around 350whp ideally.

I was going to do an sti swap, but its just going to cost a lot more money.

I was thinking something along these lines;
2.2 stroker pistons (not exactly sure about displacement though)
STI rods
Race bearings
??? crankshaft
2.0 heads with ??? work?
big 16g or 18g turbo
FMIC
255 fuel pump

thats just the basics. I haven't thought this completely through yet. Throw in your thoughts, I want to get some ideas for this build

thanks

Shayhan27

iTrader: (4)

Buy a 2.5L shortblock for 1900 bucks slap on your 2.0 heads with a cosworth headgaskets and call it good.

"disclaimer" 2.5L shortblock price subject to change.

03'EyeBug

iTrader: (17)

I would be pretty surprised to see a 16g or 16g make 350+.

03'EyeBug

iTrader: (17)

Errr, make that 18g...

Concillian

iTrader: (2)

You REALLY want to make sure your heads can handle 8k RPM if using a stroker. If you do this, a stroker is essentially exactly the same as a 2.5L STI engine with lower torque.

It will hit peak boost at pretty much the same RPM as the 2.5L and it will hit peak power very close as well.

I can hear people calling me crazy right now, but it's true. The design of a 2.1 stroker has the same rod:stroke ratio of a 2.5L The VE curve is pretty much exactly the same.

Check this Gruppe-S chart from a while ago. It shows the stroker vs. 2.5L with a pretty large turbo (55 lb/min, about 25% larger than a 20G)



Note the torque curve is flattening at nearly identical RPM. The 2.5L gets a little advantage due to having AVCS in this comparison, if you take that away, they'd be at almost exactly the same RPM.

Peak power is identical, and when either motor reaches peak power, torque drops along the same line.

So neither engine is really better than another from the standpoint of power. Some would consider having lower torque, but 8k RPM capability a bonus on the stroker, and others would consider the low end torque of the 2.5L advantageous. IMO when considering an upgrade for a WRX (which will have a 5MT,) the stroker is a significantly better match.

At redline, if the stroker is 8k and the OEM 2.5L is 7k, theoretical airflow at the same boost pressure is only about 1% different. These engines are essentially the same in terms of capability, and turbo sizing should be considered pretty much exactly the same for the 2.1L stroker as OEM shortblock 2.5L 16G is going to be pretty small for this engine. You want something in the 18g range minimum, but don't expect 350WHP on pump with an 18G, even E85 is pushing it for 350WHP. 20G with 8cm TD05 or TD06 is a very good match IMO, and is a good turbo for 350WHP goal, possible on pump, easy to get 350 WHP on E85. It shouldn't feel laggy on a stroker. The 2.0L engine's rod:stroke ratio is more aimed at high RPM. The stroker rod:stroke is a LOT better for an average daily driver / weekend warrior type enthusiast, and allows a significantly larger turbo without feeling laggy. Coupled with the 8k redline, it's a nice engine for DD, better mileage than a 2.5L and every bit as capable on any "normal sized" turbo.

All that out of the way this is how my stroker would go if I build it:
- Mahle 'off the shelf' 8.0 CR stroker pistons
- Eagle rods (cheap, potentially STi rods for even cheaper, but 8k RPM will stress the rods most in the bottom end)
- new 08+ STI crank ($330ish at subarugenuineparts.com)
- have all those bottom end parts balanced
- ACL bearings
- aftermarket valve springs / retainers
- stock 2.5L cams modified for non-AVCS use or mild ej205 non-AVCS aftermarket cams
- stock valves if valve guides aren't worn. Aftermarket with slightly thicker shafts and guides honed to larger shaft if guides are too worn for stock valves.
- bore / hone block for 92.5mm pistons (Mahle off the shelf pistons are 92.5mm)
- deck of the block about 0.005"
- deck the heads about 0.005"
(end result is compression ratio around 8.35:1)

Displacement for 92.5 bore x 79mm stroke is less than 2125cc, but some still call it a 2.2L stroker. I call it a 2.1L stroker. Whatever. Not many are talking about an 83mm stroke stroker, as that's TONS more expensive due to custom crank and pistons (and potentially rods, don't really know).

If a shop is doing the work, the Bore + Hone + balancing + labor for building the engine will easily push the cost well over the cost of a stock 2.5L shortblock + machining your heads to match the 2.5L bore. However, the stroker is a lot more compatible with the 5MT, and if you consider that you can get good power by spinning out to 8k without huge torque, then you potentially save money, becaue a 2.5L @350WHP will likely have PLENTY enough torque to kill a 5MT.

If you're assembling yourself and you're familiar with that kind of thing, then it will potentially be cheaper or similarly priced compared with an OEM 2.5L shortblock.

04caliwrx

iTrader: (6)

you will need a big 20g to hit 350 whp on a mustang dyno

silverbullet415

iTrader: (12)

2.0 is open deck

Concillian

iTrader: (2)

But has thicker cylinder walls than a 2.5

At the 350WHP the OP is talking about, block differences are a complete non-issue, you're not even close to any HP point where open / closed / semi-closed has any relevance at all. I doubt there's much relevance until at least 500 WHP. Which is a pretty serious engine build target.

silverbullet415

iTrader: (12)

doesnt cosworth make the 2.2 stroker kit

vodka

Eric, we should talk mang. If you're talking about building a motor to rev to 8krpm, I have a couple suggestions.

Concillian

iTrader: (2)

They make a stroker kit. But buying one with an aftermarket crankshaft means it's super pricey.

Cosworth kit -- $2700 +shipping in just crankshaft, pistons & rods
STi crankshaft, Eagle rods, Mahle pistons -- <$1300 shipped + ~$250 in balancing for a machine shop.

over $1k cheaper and both will perform about the same for a 350 WHP setup. The Cosworth may be slightly more efficient due to the lighter crankshaft, but it's not worh $1k more IMO. $2700 is a ton for a stroker kit IMO. The stock STi crank is fine for 8k. Once everything is balanced, it should be okay at 8.5 - 9k, but piston speeds are starting to get pretty high at that RPM with a 79mm stroke. No reason you couldn't run a 75mm crank out there, though. At least one guy is using a balanced OEM WRX 75mm Crank with a 2.5L block (2.35L displacement) and running 9k redline. Insanity right there.

EQ Tuning