New pistons/rings for EA82Turbo 1800 ?

[discopotato03]

Hi all , does anyone make decent oversize pistons for the 86' EA82-T ?

I'd prefer a little higher than 7.7:1 compression ratio as well .

 

Thanks , Adrian .

[Gloyale]

Good luck. I think one of the only places I''ve been able to find turbo pistons is from RAM engines. NA pistons are thinner decked, so removing a bit of meat to drop them to 8.x compresion seems scary. Maybe aftermarket NA pistons would be thicker? Perhaps you could do a tub like the Turbo pistons but shallower on a set of them?

 

I have really been thinking about making some "low compression" heads by removing a bit of material. Perhaps this would allow using the NA pistons reliably in a turbo?

[GeneralDisorder]

EA81 pistons are 8.7:1, and RAM does offer forged units for both engines. The price is extreeme - you could do an EJ22 swap twice over with the money.

 

Besides that you'll blow the HG's or crack the heads on the EA82T's without serious management and o-ringing the block. Not worth the thousands of $$ it would take.

 

GD

[discopotato03]

Actually you'll find if you use propper twin scroll turbos (IHI make a few) the exhaust manifold pressure and temperature is reduced without the response penalty . Need propper dual pipe header like some late WRX/Legacy's use and the turbos have a divided turbine housing and separate wastegate vent paths .

We have 98 and 100 octane pump fuel her in Crikey country (Aus) so we can use a bit more ignition advance without the detonation problems as long as the AFR's are suitable . I think this is the way to get good performance from this engine without stressing the thing with high temps/pressures .

 

Just need pistons with fair CR ie 8.5-9:1 and good ring lands .

 

Cheers A .

[daeron]

hrmmm.. sounds like we might have a member who can go to some extremes, given your fuel situation.. and I take it that you are not unfamiliar to turbo engines (skyline R33?)

 

Check the "similar threadS" listed at the bottom of the page, and search around, there are alot of ea turbo opinions that are well formed at this point, so youre definitely going to hear people say that its a waste of time playing in EA land when EJs are easier cheaper and better.... BUT you don't need to let that discourage you. your fuel can help make a significant difference.. but if you are not familiar with these engines in particular, be forwarned that they EAT HEADGASKETS for lunch if you dont keep them well cooled, and do NOT let it go lean!!!

 

good luck finding what you want, I personally kinda like the idea of reshaping the combustion chamber, maybe a thick headgasket, and using NA pistons. reshaping the combustion chamber attracts me because with better swirl patterns, you just might be able to help the detonation THAT way.. and improving combustion qualities of the chamber as a whole. giving you more advance to play with, and more power.

[discopotato03]

Yes no stranger to hair dryers . I have not actually seen in person EA82 pistons so I have no idea how good/bad they are ie drilled or slotted oil returns and how the ring lands look . You may actually be able to tell me if the Turbo/NA rings are interchangable on NA pistons .

I had not thought about NA pistons with modified chambers but thats not such a bad idea . What was the NA CR ie 9.? to 1 . Also are the EA 81 8.7:1 pistons direct fit ?

 

Thanks Adrian .

[ZRX Doug]

I'll be the first to confess that I'm not particularly well versed in the world of Subaru..but have you given any thought to the other end of the assembly? Perhaps you could have a set of connecting rods resized (off-center boring on either the big or little end) to move the piston a tad further up into the combustion chamber.

Not sure if Subaru gives you enough meat on the rod ends to work with, just thought I'd toss a different angle out for ya to think on.

Failing that, any possibility of moving the wrist pin further down on the piston with a little welding & reboring?

[Gloyale]

I'll be the first to confess that I'm not particularly well versed in the world of Subaru..but have you given any thought to the other end of the assembly? Perhaps you could have a set of connecting rods resized (off-center boring on either the big or little end) to move the piston a tad further up into the combustion chamber.

Not sure if Subaru gives you enough meat on the rod ends to work with, just thought I'd toss a different angle out for ya to think on.

Failing that, any possibility of moving the wrist pin further down on the piston with a little welding & reboring?

 

You can't make the piston travel any "higher" in the cylinder. It already goes right to the top Turbo and NA. The Turbo pistons are not shorter overall, they just have a "tub" cast into the middle. But the outer edge is just as tall as a NA piston. Externally they have the excact same dimension, with the exception that the Turbo piston skirts are longer.

 

As far as piston construction, they have slotted oil return, both Turbo and NA. The rings appear to be the same. But I think there is a slight difference in the type of top ring use. Carb pistons are 9:1, SPFI and Non-turbo MPFI pistons are 9.5:1. Someone else will have to answer the EA81 question, I'd love it if they are a direct fit.

 

The rods are beefy enough but minimal. I think modifying them would be questionable, and expensive probably

[ZRX Doug]

Nah, it's actually pretty cheap to resize rods if you can find a shop that'll do it..but if what you say about the deck clearance is true, there's no point in it. From your description, it sounds like the cheapest way out (machine shop-wise, rather than aftermarket parts-wise) would be to add material to the dished area of the turbo pistons and then machine to the CR you're trying to achieve.

[ZRX Doug]

Ah. Had one of those blinding revelation thingys while driving home..if the naturally aspirated piston has more compression than you want, but the compression face is too thin for cutting, why not just drop it further below the deck to get the ratio you want by "shortening" the rod? Assuming it's not too dramatic a drop, it'd be a simple matter to mill X amount off the parting face of the rod and have the milled rod honed true, effectively moving the big end up X amount.

[daeron]

Ah. Had one of those blinding revelation thingys while driving home..if the naturally aspirated piston has more compression than you want, but the compression face is too thin for cutting, why not just drop it further below the deck to get the ratio you want by "shortening" the rod? Assuming it's not too dramatic a drop, it'd be a simple matter to mill X amount off the parting face of the rod and have the milled rod honed true, effectively moving the big end up X amount.

 

Thats gonna be changing the entire throw of the piston. It changes the BDC location as well as the TDC location; might you not wind up not losing any static compression ratio due to the increase in swept volume from the shortened rod?

 

I can't think of the formulas and everything now.. but I think adding material to the dish and moving it might be more viable than playing with the rods. Have at it, though; if you feel you can forge new ground it would be fresh air to be sure.

[ZRX Doug]

No, the stroke length doesn't change, only the volume of the combustion chamber with the piston at TDC will. In other words, the "9" part of a 9:1 ratio would stay the same. Changing center-to-center length on a con-rod has the same effect as milling the head or running a thicker gasket, only you're doing it from the other end.

As I said, I'm not real familiar with Subaru engines, but this isn't exactly "new ground" for the rest of the racing world. Resizing rods to get proper center-to-center measurement is a standard part of blueprinting an engine..this is just "blueprinting" to your specs rather than the manufacturers'.

I wouldn't expect him to be shortening the rod enough to show any real-world effect on the bottom end of the engine as far as rod ratio & thrust face issues are concerned..maybe a few milimeters?

I'd love to mess with this stuff in the real world, but for me the Soob is just my daily driver when it's too crummy out to ride a motorcycle..this is just mind candy for me, trying to give you guys a different angle on an old issue.

[discopotato03]

Guys I would not attempt to drop the CR by "lowering" the pistons or using thicker gaskets . I'd like a slightly higher static CR but not at the expense of altering the quench or squish zones . If I could see a pic of a turbo and NA piston side by side I could get an idea of any differences to ring lands .

ATM I'm contemplating alterations to the chambers (weld and reform) or NA pistons and opening out the chambers without altering quench zones .

 

Thoughts ?

[ZRX Doug]

Anything done to lower/raise compression MUST alter the quench area. Well, anything short of a stroked crankshaft that features the the same TDC height of the piston but a longer stroke, that is.

Not knowing the particulars of this engine, I really don't know how much of a change it would take to get the compression you desire..but seriously, if you choose to do the math I think you'd discover it doesn't take much "drop" up/down the hole for significant compression changes.

For instance, with my own Kawasaki engine ('99 ZRX-1100) we discovered another factory piston (ZX11) that features an identical dome design, but a wristpin that's 1mm lower on the piston, resulting in a 1mm increase in dome height at TDC. The 1mm diff is sufficient to raise static compression a full point (from 10.9:1 to 11:1) by itself, using a thinner head gasket and deleting the cylinder block base gasket results in a net gain closer to 3 compression points, or 11.25:1 or thereabouts. This is on an engine with a comparatively small bore diameter of 76mm..obviously, the larger the bore the greater the change. It's very nice "poor man's" solution for us ZRX guys desiring a tad more compression (or those ZX11 ones looking for a tad less)..

 

This is a fun discussion! At least for me..

:-p

I can see where you'd be hesitant to try whacky departures from the norm on YOUR engine (I'd be hesitant to risk my investment on the say-so of some yo-yo on a message board also), but keep it in mind and do a little exploration of the concept..ya may be pleasantly surprised.

[Gloyale]

 

Here is a pic of the two pistons. You should check out the "splitting headache" thread in the retrofit forum. It has some good pics of the pistons( an NA one sawed in half) long thread but the piston pics, and a sketch of my head idea are there starting on the 3rd page or so.

[Loyale 2.7 Turbo]

...

This is a fun discussion! At least for me..

:-p ...

 

Well... for me Too!

 

You can't make the piston travel any "higher" in the cylinder. ...

 

That´s Exactly what I wanna Say: You Can´t. Not only for the Said Reasons, also: They can hit the Valves... Don´t Forget that!

[joostvdw]

Well... for me Too!

 

 

 

That´s Exactly what I wanna Say: You Can´t. Not only for the Said Reasons, also: They can hit the Valves... Don´t Forget that!

 

hitting the valves is one of your least problems, it's an non-interference engine so you can change ALOT before you hit the valves

[idosubaru]

RAM will customize their pistons for you. talk to them if their price range is within reach, they do excellent work.

[GeneralDisorder]

Your fuel isn't any different than ours - the fomula they use to calculate the octane is.

 

Doesn't matter anyway though - EA82T is an excersize in futility.

 

GD

[ZRX Doug]

Doesn't matter anyway though - EA82T is an excersize in futility.

 

GD

 

There's no such thing..300+ horsepower air cooled VeeDub engines that originally were built to make 40 hp are proof of that..if ya throw enough time & money at ANYTHING, it'll make power. We're just trying to brainstorm a way around the "money" part of the equation, lol

[mikeshoup]

We're just trying to brainstorm a way around the "money" part of the equation, lol

Pick Two:

1 - Cheap

2 - Powerful

3 - Reliable

[ZRX Doug]

I've been playing long enough to have modified the "cheap" part of that equation a wee bit..lots of valid modifications are "cheap" when speaking purely of a cash investment, but expensive in terms of sweat equity (either skull-sweat or the real kind)..as a group in general, motorsports enthusiasts are slowly devolving from a buncha guys who hand-ground their own flathead Ford camshafts into a buncha guys who purchase stuff and say "it can't be done" if the thing they want isn't already sitting on a shelf somewhere.

[discopotato03]

We will have to agree to differ over quench zones but judging by the piston crown pics the turbo ones are better because of the wider "flatwasher" section on top . The "dish" is pretty crude but functional I suppose .

 

Yep the price bit is hardest to beat , can get just about anything made with enough money but as it gets closer to EJ20 Turbo budget the EA starts to look pretty sad .

 

In off the shelf stuff (if its still available here) I guess EA82-T or if the N/A EA81 piston is suitable and still 8.7: static CR - possibly better .

 

I don't remember how the Mon/Ron equation runs with pump fuel in Australia but I can tell you that we started out with glorified mouthwast 89 octane ULP in about 1985-6 and 95 , 98 and E5-100 "oct" is now available through Shell . Its called VP Racing 100 . People I know who've tuned turbo engines with this stuff reckon you can add heaps more on load advance in before the engine detonates . More everywhere actually .

 

Night all , cheers A .

[GeneralDisorder]

Those flathead V8 guys would have jumped at the chance to drop in an engine twice as powerfull that can be had for the price of a performance carb.

 

Besides that there's quite a difference betweent flathead tech, and the engines of today (or even of 20 years ago). Not the least of which is material sciences, and manufacturiing techniques that cannot be duplicated easily by the average modifier.

 

It's not a matter of *if* it could be done - sure it could. New rods, pistons, and heads/studs (biggest problem by far) would easily bring the EA82T up to snuff quickly - to the levels of performance seen in modern engines. We all know that. The issue IS the cost, and there is NO way around it. People have hashed this out many, many times. When you can build a decent EA82T for the price of an EJ22 then maybe it will be viable - till then it's acedemic - arm-chair B$ that will never come of anything. Spare us yet another long thread about what you *think* can be done, and what you could *theoretically* get out of it. Get out there and DO IT if you think it's such a viable option.

 

GD

[Gloyale]

Spare us yet another long thread about what you *think* can be done, and what you could *theoretically* get out of it. Get out there and DO IT if you think it's such a viable option.

 

GD

 

Spare us the "EA82 is the devil, and the EJ is your savior" bit. You don't want this thread to get longer? Don't post in it. EJ swaps are cool and great, but not everyone is going to do a conversion. It's alot more than most people want to tackle. this thread is about modding an ea82. If you wanna talk about that then please do. But I personally don't need to hear again why the sky will fall if I don't get an EJ.

 

"oops, the headlights busted, better do an EJ swap":lol: