hi comp pistons

[Aluxes]

So I have been searching for some hi-comp pistons for a 2.2 build but seems like no one makes them for this engine. Only the 2.5. So, and this might be a crazy question but, since the 2.2 bore is 96.9 mm(3.815 in) if the block was bored .10 over then the bore would be close to that of the 2.5 of 99.5 mm (3.917 in). So would a 2.5 piston fit in a 2.2 block bored .20 over? Would the .002 be too much of a difference? I know some would say just do a frankenmotor, but I already have a spare 2.2 block and I want the reliability of the 2.2.

[987687]

Why not just have the heads decked to raise the compression?

[86BRATMAN]

Svx pistons, same bore as ej22e. I can personally vouch that they work as I am running them in a 22e shortblock with 25d heads. With a pair of ej22t head gaskets my calculated compression ratio is 10:1, you could go higher with a thinner gasket as well.

[carfreak85]

I'm not sure if the EJ22T has the same piston dimensions as the N/A engine, but Google is your friend in either case...

 

 

http://www.jepistons.com/Catalogs/Sport-Compact/Subaru/ej22.aspx

http://6starspeed.com/su2peenbukit.html

 

There are tons and tons more piston companies out there, you just have to search...

[Aluxes]

Ok cool Ill check out some of this info!! Im not sure if decking the heads is a good idea with a overhead cam. I read on the Paeco website that decking the heads shortens the distance between the cam sprocket and the crank sprocket and this throws of your valve timing. Dont know if this is a problem but it makes sense.

[Aluxes]

BTW 86bratman, how much hp and or torque do you think your getting from the increase in compression. Is there a estimate or equation pertaining to hp/tq gain comparable to compression increase?

[86BRATMAN]

with my set up there is more gain in horsepower than torque over a standard ej22e. Not saying it didn't made a noticeable change though. My car has a 3.90 final drive, a modded intake system, header and full exhaust as well. But it will stretch it's legs and walk away from my friends gt with similar mods and a 4.11 trans. So it's no slouch.

[Aluxes]

Cool!! I just did a search and found a few different answers. One was a 15hp gain. Another claimed 20. But the one that resonates with me the most is a 4% increase in hp with every point of compression increase. I dont know how much I could realistically go with a 2.2, but a gain of 6-8 hp doesnt seem that worth it. For the same price I could bolt up a small boost turbo and gain more hp than that.

[86BRATMAN]

I'd have to say that between the compression bump, and the much better flowing heads I've gained more than a few hp. I could have gone higher in cr but I wanted something that would still run safely on regular octane fuel if needed. With a 0.8mm gasket instead of the 1.5mm I could have gotten around 11:1. Which isn't out of the question for a future build. If I had to estimate I would say I'm in the 180-190hp 150-160tq range at the crank.

[Aluxes]

I'd have to say that between the compression bump, and the much better flowing heads I've gained more than a few hp. I could have gone higher in cr but I wanted something that would still run safely on regular octane fuel if needed. With a 0.8mm gasket instead of the 1.5mm I could have gotten around 11:1. Which isn't out of the question for a future build. If I had to estimate I would say I'm in the 180-190hp 150-160tq range at the crank.

Hmmm thats good to know. Is the 0.8mm gasket made by cometic? Is there more of a chance of loosing a HG with it being thinner? What octane fuel are you running? What octane would you run if you were at 11:1? At that hp are you running a piggyback or have some kind of engine management besides the stock ecu?

[86BRATMAN]

The 0.8mm gasket is available oem subaru for the 99-01 ej222, it's a multi layer steel gasket and is very reliable. It's been my experience that thicker MLS gaskets are more prone to failure (not just in subarus but across the board). Take the ej25d for example. But that's another discussion. I am currently running a stock ej25d ecu on my engine, and normally run 89 octane. I can run 87, and have on many occasions with no sign of detonation. I have no doubt the car would run better with some sort of tuning whether it be an s-afc or something more sophisticated I simply haven't came across a deal that I felt was worth it yet. At 11:1 compression I would run nothing less than 93 octane. I do have plans to change the gaskets for the thinner set I have, but it will be after I decide on something to tune with. I am researching the esl daughterboard that is marketed for the overseas turbo cars of this era as I don't want to go full standalone because I enjoy my cars driveablility with the stock ecu, but have not had much luck on their use with na ecus. If I can make use of one of those boards (probably having to swap to a jdm ej20d ecu to use it) I'll definitely be going for some more bang from this little engine.

[Aluxes]

Oh I did not know we could use a different ecu. If you dont mind me asking, do you know an alternate ecu I could run in my 97 Imp OBS? Is it a plug and play kinda thing, or is there more involved? Ill def go with the .08 HG since its oem. Thanks for that bit of info!!

[86BRATMAN]

the ej25d ecu is straight plug and play, the jdm ecu I was speaking of requires a decent bit of wiring changes. More than most people would do for a daily driver.

[Aluxes]

Nice!! I think I found my ECU up grade....for now. What improvements happen with this upgrade? More fuel to the injectors, better timing curve? Where is the ECU located on the 97-99 Legacys? Thanks again for this!!

[86BRATMAN]

The rev limiter is higher (7600) and has more aggressive timing curve. I'm not sure about the fueling, but I'm sure it's better as the ej20d is a 150hp 2.0 stock. The ecu is in the passengers side foot well, pull up the carpet and you'll find a metal plate, the ecu is under it. You will have to get a jdm ecu pigtail to wire in to use this ecu.

[Bushwick]

It'll mainly be more timing. If your revs are uncorked and allowed to 7600, your hp will increase on the top end. A compression ratio of 10:1 is near perfect for a street car. It'll compliment the cam you are going with, but you MUST run premium 93 if you get both an ECM and comp. bump. Keep in mind, a 10-15 hp bump is probably a V8 engine. Figure 5-7.5 hp for a 4 cyl. The engine will be more responsive. And also, don't think of it as a "peak" hp number. 5 hp and maybe 10 tq across the entire range will be noticeable, especially with all the other mods. By itself, probably not worth it. But with cam, el header, exhaust, open element air filter, compression, and ECM,  even if every "mod" nets 5 hp each and 5 tq EACH, that's 30 hp and 30 tq total when combined. Obviously that's conservative, but you get the point. Increasing your average Hp/Tq figures across most of the rev range will be where it's at when you punch it and want to move. If you ever want to turbo the car, don't mess with the compression, or make sure it stays around 9.5:1 to 9:1. 

[86BRATMAN]

Don't forget the biggest difference in my build, the heads. The dohc ej25d heads alone are a massive improvement over the crap flowing ej22e heads. You won't see the improvement I did without them, I'd put my little 2.2 build against a high comp frankenmotor any day of the week.

[Fairtax4me]

the 25d heads will flow better and make more power on the top end.

I wonder how a similar block build would perform on the bottom end with 2.2 heads since the smaller ports help with bottom end torque.

[Aluxes]

the ej25d ecu is straight plug and play, the jdm ecu I was speaking of requires a decent bit of wiring changes. More than most people would do for a daily driver.

So I got the EJ25D ecu, installed it. At first when I started it there was a slight hesitation when barely touching the throttle, but after a few minutes it went away. Took it out for a test drive and WOW!!! What a difference! Revs quicker and smoother and pulls a lot harder. Low end torque is definitely better too! Also added a new 140 amp alternator and a grounding kit from Flex innovations, which by the way is very good quality. Plus they supplied me a free kit for measuring out my car which they didnt have a kit for. Anyways thanks again 86Bratman for the tip on using the 2.5 ecu.

[Bushwick]

Wait, is the ej25 ecm compatible with every-day ej22's? Are you saying I can install an ej25 ecm in my Legacy and get the rev limit increased along with more aggressive timing which should equal a couple hp? If so, is the fuel pump capable of running this long-term? Does the mixture go too rich from more gas being dumped in?

 

 

 

@Aluxes  You should have just grabbed a 3.6l 130 amp Tribecca alternator. It needs a tiny amount ground away from a bracket but otherwise fits as-is. Can either run the wider pulley (which lines up but leaves one set of ribs unused). Been running mine for almost a year now and so far so good. Cost $35 and came from an 11' mode;

 

Also, since you are building a "performance" setup, a 140 amp alternator is going to steal MORE hp when charging than a 65 or 80 amp will. Unless you running a really demanding Class A/B amplifier to a sub(s) in the 600-900w bridged range, you don't need that big of an alternator as it'll actually slow the car down. Another old racer's trick that can help out is installing a a switch in between the charge "on" wire on the alt. Not talking about the wire that runs to the battery directly to charge, but talking about the alt's "on" wire that's attached to the 2 or 3 prong plug up top. It essentially acts the the same way as an amplifier's "remote 12v+" "On" wire. If you start the engine with the alternator belt OFF, grab the alt pulley and try turning it with that plug up top disconnected. The pulley will spin effortlessly. Now, connect the plug and try spinning the pulley again. It will feel as though as it's "locked up". That lock up is what the engine has to overcome in order to get the alt to charge the battery and run electronics. A 140 amp needs more effort to charge than a smaller alt. Reason why you still see 35 amp alternators for "race or drag" cars as it's not as demanding to power. If you were to try and use an electric motor to run the alternator, you'd need around 2hp to get it moving. A really high torque motor like what's found in a 120v hand held drill can typically turn them (run a chuck in the drill that can allow a 20 something mm socket to fit) but it's extremely demanding. Anyways, adding a switch to the signal "on" and turning it "off" when tromping on the gas pedal, will free up 2-3 hp across the entire rev range. Think of it as the same thing that AC compressors do when you stomp on the gas pedal to increase MPG by disengaging the AC clutch. If you know how, install an interrupter switch on the accelerator pedal to break the circuit when doing WOT. That way, every time you mash the gas pedal, it should stop the alt from charging and thus free up 2-3 hp, but remain engaged during normal driving and stop light sitting. Could make a bracket or alter a brake light switch and bracket from a donor car (shy's the limit with options here) and use that on the accelerator pedal, or possible source something from a Nitrous kit

[86BRATMAN]

The ej25d and ej22e have the same fuel injector flow ratings and the cars use the same fuel pumps. The difference is in the timing and fuel curves, that's what really transforms how the engine runs. My high comp is actually more fuel efficiency on the 25d ecu than it was with the stock ej22e one. I got around 33mpg highway on a recent trip, with a draggy brake caliper.

[Bushwick]

The ej25d and ej22e have the same fuel injector flow ratings and the cars use the same fuel pumps. The difference is in the timing and fuel curves, that's what really transforms how the engine runs. My high comp is actually more fuel efficiency on the 25d ecu than it was with the stock ej22e one. I got around 33mpg highway on a recent trip, with a draggy brake caliper.

 

So you are saying it's improvement? I've never heard of this before, but will gladly drop $20 for used ECM if it improves timing advance and raises rpms. Not that my car is any thing close to be a performance car, but I'd gladly take a slightly stronger timing advance and increase in redline for the few times when passing is needed. What year/model/engine are you suggesting then? Is this a Legacy Outback deal, or is it a WRX or Forester deal?

[Aluxes]

Wait, is the ej25 ecm compatible with every-day ej22's? Are you saying I can install an ej25 ecm in my Legacy and get the rev limit increased along with more aggressive timing which should equal a couple hp? If so, is the fuel pump capable of running this long-term? Does the mixture go too rich from more gas being dumped in?

 

 

 

@Aluxes  You should have just grabbed a 3.6l 130 amp Tribecca alternator. It needs a tiny amount ground away from a bracket but otherwise fits as-is. Can either run the wider pulley (which lines up but leaves one set of ribs unused). Been running mine for almost a year now and so far so good. Cost $35 and came from an 11' mode;

 

Also, since you are building a "performance" setup, a 140 amp alternator is going to steal MORE hp when charging than a 65 or 80 amp will. Unless you running a really demanding Class A/B amplifier to a sub(s) in the 600-900w bridged range, you don't need that big of an alternator as it'll actually slow the car down. Another old racer's trick that can help out is installing a a switch in between the charge "on" wire on the alt. Not talking about the wire that runs to the battery directly to charge, but talking about the alt's "on" wire that's attached to the 2 or 3 prong plug up top. It essentially acts the the same way as an amplifier's "remote 12v+" "On" wire. If you start the engine with the alternator belt OFF, grab the alt pulley and try turning it with that plug up top disconnected. The pulley will spin effortlessly. Now, connect the plug and try spinning the pulley again. It will feel as though as it's "locked up". That lock up is what the engine has to overcome in order to get the alt to charge the battery and run electronics. A 140 amp needs more effort to charge than a smaller alt. Reason why you still see 35 amp alternators for "race or drag" cars as it's not as demanding to power. If you were to try and use an electric motor to run the alternator, you'd need around 2hp to get it moving. A really high torque motor like what's found in a 120v hand held drill can typically turn them (run a chuck in the drill that can allow a 20 something mm socket to fit) but it's extremely demanding. Anyways, adding a switch to the signal "on" and turning it "off" when tromping on the gas pedal, will free up 2-3 hp across the entire rev range. Think of it as the same thing that AC compressors do when you stomp on the gas pedal to increase MPG by disengaging the AC clutch. If you know how, install an interrupter switch on the accelerator pedal to break the circuit when doing WOT. That way, every time you mash the gas pedal, it should stop the alt from charging and thus free up 2-3 hp, but remain engaged during normal driving and stop light sitting. Could make a bracket or alter a brake light switch and bracket from a donor car (shy's the limit with options here) and use that on the accelerator pedal, or possible source something from a Nitrous kit

Yea I am running a fairly large sub woofer amp, 1500w, and a smaller amp for the door speakers. I dont get a drop in idle or a slight dimming of the lights when i turn my fan on high. Cant wait to take the car on a road trip to see the improvements in power and fuel mileage.

[Aluxes]

So you are saying it's improvement? I've never heard of this before, but will gladly drop $20 for used ECM if it improves timing advance and raises rpms. Not that my car is any thing close to be a performance car, but I'd gladly take a slightly stronger timing advance and increase in redline for the few times when passing is needed. What year/model/engine are you suggesting then? Is this a Legacy Outback deal, or is it a WRX or Forester deal?

Its a definite improvement in my case. I got the ecu from a 97 legacy outback, for the ej25D.

[Bushwick]

Yea I am running a fairly large sub woofer amp, 1500w, and a smaller amp for the door speakers. I dont get a drop in idle or a slight dimming of the lights when i turn my fan on high. Cant wait to take the car on a road trip to see the improvements in power and fuel mileage.

Unless it's a "Class D" amp, I doubt it's 1500w rms. Class A/B from reputable companies that follow the 2006 guidelines and are putting out actual wattage numbers as listed, 900w is about the largest for an A/B amplifier. Class D are typically needed for 1000w and higher unless running multiple A/B amps bridged. Fuse rating can help ballpark it. Example: if the amp has 2 x 30 amp fuses or a single 60 amp, it's probably a 600w rms at the most. 1200w rms will need around 60 amp x2. If running really low impedance, the current demand will be higher so that same 1200w amp might draw 70 amp x2 at lower ohms. What amplifiers are you running?

 

Its a definite improvement in my case. I got the ecu from a 97 legacy outback, for the ej25D.

 

I'll have to give this a try. Can someone list best years to use? And the ej25d means from a DOHC, correct? I'm betting the timing advance was done to improve the low-end power loss typically seen in DOHC from the increased flow. Probably best to run premium grade to avoid detonation and get the most from it. Can't wait to try this!

 

I'll have to pull a TON of items from the car to get back to a sensible curb weight, but would be willing to do a before and after showing the tach/speedo on a flat section of road with a timer so show what if any difference there might be. If no one is willing to do the spark plug mod, I'll be willing to install basic plugs and compare against my modded ones to put the skeptics to bed to if any one is interested?