silent running

Now that I'm thinking about different options for rebuilding my EJ20 engine I need to get a better understanding of what's what, so here's some simple 'FAQ' style questions. They may seem obvious but everyone's got to start somewhere:

• I understand (or think I do) that forging components rather than casting gives you better material density but how are they actually made? Say a forged piston - I'm imagining a lump of red hot alloy almost solid but still a bit molten on the outside, then a bloody great press that bangs it into the shape needed, then it's quenched and a CNC milling machine comes along to do final cutting of the exact shape. Correct, or way out?
• What is the benefit of a forged component over a standard cast one? Why would bottom end build favour one particular component being forged with the others left as standard?
• Are all strengthening measures within an engine basically to do with the increasing loads at high revs, rather than outright boost? Or heat dispersal?
• When a crank is ground to fix say big end damage, are we talking about turning down the journal part (I think that's the right term?) by a mm all round then fitting a thicker bearing? Is a bearing the same as a shell?
• I've heard about 'drop in' pistons. What are they?
• How do you build a totally bulletproof EJ20 engine? What would be on the shopping list and why?

Lots there, so take your pick!

olliecampbell

iTrader: (3)

Some good questions...shame I cant answer them...

Welloilbeefhooked

iTrader: (3)

Silent,

The forged components have more stength than cast due to the materials grain structure that is altered during the forging process. Cant explain it any better than that even though I studied mechanial engineering.

The best 2.0 block would be a closed deck from the early cars (STI's, RA's).
It has the bores held more securely than semi or open deck blocks. Have a look at the 2 pics here for the difference.

Most of the builders on here will say brand new crank, forged rods and pistons. The STI heads would also allow for a higher rev range than the stock WRX heads and valve train.

Index of /Scooby Pics/Engine

I think I would consider the short engine rather than rebuild. A new crank is £350 ish and maybe vat on top too.


The crank needs to be new rather than reground. You are right about the grinding process, although its a matter of a thou or 2 rather than MM's.
The bearing is then thicker by the same amount to maintain clearances.

From what I have read the subaru crank has a surface hardening process applied to the journals that is only a few thou thick. Grinding removes this and sometime in the future you are in the same boat you are in now.

Wayne.

silent running

Well interestingly enough, I *can* get hold of an early closed deck block. In fact it's a complete short engine and I'll be able to get my hands on it fairly cheap too. I was thinking about having the crank out of it. Didn't really consider the whole thing as I wasn't sure on the condition of the bearings/rods/pistons, and of course there's no way to tell for sure without pulling it apart and then rebuilding. I do want to build a bulletproof engine but at the same time I don't want to buy a new gearbox. My target is 300-350bhp really, but I want it to be making this easily rather than having to stretch every component to the limit. This gets me to thinking maybe the time is right to use STi heads so I can make more power more easily. I'm not a big fan of using more and more boost and heat management to achieve power.


A new set of STi rods and pistons would be £750 AFAIK, then £150 for bearings, £300 for gaskets, and already I'm over a grand without the cost of the short block itself. How can you generally tell if rods and pistons are knackered? Do they gradually wear like many other components so you can tell how much life they have in them, or do they look perfectly fine then one day suddenly fail catastrophically?

olliecampbell

iTrader: (3)

Just out of interest where did you source it..I'd quite like to start a second engine build...

PS good pictures

silent running

A local garage that has various bits in and out. If you're interested I can find out exactly how much he wants for it.

Welloilbeefhooked

iTrader: (3)

If I was spending anything over a grand just for parts then I would go for an EJ257 which will see 400hp easy. It will run quite nice on a TD05 with early spool and loads of torque.

Wayne.

jasonius

iTrader: (1)

This is something I'd really love to do, purely as a building project, not because I necessarily need one at the mo..

However, I also believe a fully built forged CDB bottom end is way over-kill for a max target of 350 of each

Fir that level I'd have gone for one of the EJ257 short blocks that were in the GB section recently, possibly with some drop in forged pistons..

That would be very capable of handling 400 of each safely.

The only thing is you're not building it from scratch yourself, which in my case might not be such a bad idea.. Although this would be my reaon for giving it a go..

The money saved 'could' go towards a stronger box..

silent running

Yes I too just really like the idea of building it myself. When you talk of 'drop in' pistons what do you mean? You'd not need to take the block apart?

The other thing that's at the back of my mind is how straightforward this really is to substitute an early WRX classic block for a 2.5 - I have a phase 1.5 (centre coil) inlet manifold, early WRX heads that aren't that good I don't think, then surely it will all need some kind of mapping to get it timed up right? What about compression, valve lifts etc etc. It can't be as simple as dropping in a 2.5 block and it just fires up because it looks almost the same on the outside? Can it?

And what about buying parts from the States. If I had the money I would have no hesitation in getting API to do a build for me, that's still on the cards in fact. But if I'm forced to go down the DIY route because I'm 'time rich' and 'cash poor', why not buy a set of forged CP or JE pistons from the US for £300 delivered and no doubt a similar amount, or less for steel rods?

MY,k436suy

Silent,
Just out of interest where abouts on the east coast are you?

silent running

Lowestoft/Beccles area.

MY,k436suy

Just a few miles from me then really, 20 maybe.
Like you i'm time/rich and money/poor (till i start new job in about a month!)
So i would be quite interested in finding out a bit more about our lumps, if you need a hand.

silent running

I love it when a plan comes together. I will definitely take you up on that when the time comes. My problem is that I'm SO poor at the moment that I can't buy any parts until I've saved up the money, hence why I'm borrowing my mate's 205 GTi for a few months!

MY,k436suy

Cool, have not had my poor girl on the road for over six months due to lack of funds and only done 13k in her in 6 years but it would break my heart to sell, she maybe 15yrs old but still a dam tidy car. Running an escort diesel van at the minute just so i stay well out of the red. Planning a build myself sometime soonish so it would be great to find out lots of info just like yourself.

olliecampbell

iTrader: (3)

Hmm I like the sound of a bench built 2.5....but what about the other parts...ECU, engine mounts, gearbox connections etc etc....I can see this getting more expensive!

Henrik

iTrader: (5)

Aren't the 2.5 block dimensions (external) exactly the same as the 2.0 dimensions? In that case, it should just mate up to all ancillaries as the 2.0 blocks.

stoneface

iTrader: (6)

Yes they are, it will all bolt up fine.
You would need to get a new ecu though.

silent running

Ah, that's the problem, I'm running a v4 Power FC at the moment. Is it that the ECU can't control it, or that the wiring's all different/wrong? That would rule it out straight away as I'm happy with my Power FC.

olliecampbell

iTrader: (3)

Good point...wiring loom. Damn its getting worse!

stoneface

iTrader: (6)

Sorry i presumed you had std ecu-which if v4 can't be mapped.
Apexi will be fine, use your heads inlet manifold etc and all wiring remains the same.

Welloilbeefhooked

iTrader: (3)

Silent,

I'm willing to help out if you do decide to build your own or buy a short block.

I have an engine hoist and can get over at weekends if needed to lend a hand.

I also have datalogit/fcedit and can map PowerFC's. I'm no expert but I have wideband and will be looking at getting/making some det monitoring equipment very soon. I can do a safe map until Zen could remap it for you. If Paul can supply a safe map for the EJ257 and your spec I could load that for you too.

As has been stated above, the EJ25/7 is only a block swop and your heads and everything else should fit. You can do a DIY modification to the heads the get a better combustion chamber. I think there is more info on 22b.com.

Wayne.

silent running

Nice one, this is what Scoobynet's all about. But I wouldn't dream of asking you to come over from Sheffield to help me out! What I will definitely need if I go down the route of a self build is lots of technical advice because this will be the first time I'll have tackled one. The main worry is not following instructions, but knowing what I'm looking at when I get it all apart - to an amateur like me, a knackered crank may well look very similar to a good one. Heads full of swarf may look clean to me. BTW I've found no debris whatsoever in the oil I drained from my rattling engine.

I've helped a mate out with his 205 GTi and even managed to cobble together a 1.9 lump from various bits and pieces and got it into his car, it even runs fairly well, so that gives me confidence to get started on it. Put it this way, if I didn't think I could do it, with a little help, I would just sit tight and leave it to an expert.

Welloilbeefhooked

iTrader: (3)

Just a thought, have you had a second opinion on your engine? The reason I ask, as you probably know, is that the 98 engines are very slappy anyway. Mine actually sounds, and always has done, like it has little end knock (the end of the rod that connects to the piston). 5 years on and its still the same but ok.

Wayne.

PS I would like to help with a map if you like. Not wanting to go to extremes, but just get it up and running. If you do go 2.5 then bigger (550cc) injectors may be better than the 440cc's you have now.

silent running

Good thought, but no, it was 'rebuilt' by a bunch of local crooks 15k miles ago, and since then has been running nicely although it was always a bit squeaky/tappy on one side. It's never made the numbers on the rollers even though mapped up by Zen for 1.45 bar boost off a TD05 16G with an FMIC and every bit of heat management known to man. I suspect there's something not quite right in there, whether heads or block.

Regardless of that, it ran quietly and well until last week when driving it I suddenly heard a gradually worsening tapping, then quiet rattling then a loud rattling and I went to my local specialist who really does know his performance cars and it took him all of 2 seconds of listening to say that the engine would have to come out to look at the crank/big ends. I'm absolutely certain it's knackered plus I've already drained the oil and coolant in preparation to pull the engine.