EA81T high compression setups

[coronan]

Compression an Turbo motors have been discussed but i'm inquiring about the other details other folks have found to work.

 

I have a EA81 Turbo.  

Heads from Ram Performance with larger valves.

Polished heads, but not ported.

10:1 compression
Stock Turbo Cam

NGK BPR6EIX-11 Spark plugs.

Stock turbo

16lb radiator cap

New water pump

Stock boost (7psi)

 

 

I think that's it.

 

Hear knock at sustained full throttle.

I backed my timing down to 11*. It's reduced but I can still hear it.

Sorry, no wide band O2.(yet)

 

 

Should I move to a cooler plug?

That are other folks using?

 

 

Thanks!

Edited March 17, 2016 by coronan

[Crazyeights]

Compression an ....

 

I have a EA81 Turbo.  

Hear knock at sustained full throttle.

I backed my timing down to 11*. It's reduced but I can still hear it.

Sorry, no wide band O2.(yet)

 

Thanks!

 

Is it a "timing or detonation ping" or an actual knock? Why is it 10:1 compression if it's a real EA81T with stock dished pistons? It should be closer to 8.0:1 as I recall. I personally wouldn't operate an old EA81T at "sustained full throttle" for very long   Secondly you didn't mention what was done with the crank and rods? It may be about ready to throw a rod if the bearings haven't been looked over. Does it have new pistons and rings as well? These engines are over 30 years old by now. Keep us posted and good luck!

[coronan]

I had the top end rebuilt only.  Stock pistons.

The head was shaved to bring it up to 10:1.  

Only 100,000 mi.   on the motor.  Oil pressure is good.  

 

A rod knock should be constant.   No?

I  think its detonation because i only hear it after long on ramps or continuous driving at high speeds.  When i roll off the throttle and boost drops bellow 5psi the noise goes away.

 

I'd really like to hear from folks who are successfully running similar setups.   

How much timing?

What plugs?

Less than stock boost?

 

Thanks!

[86BRATMAN]

Stock ea81t compression ratio is 7.7:1, I don't think it's physically possible to have shaved enough for a 2.3:1 bump in compression.

[jono]

I know that compression pressures do not really indicates what a compression ratio would be , but be curious to know what compressions you get from either cold or op temp test.

 

I am guessing the EA81T dizzy has the vac cannister on it ? If it is same as EA82T S1 dizzy it is boost retard as well as timing retard from knock sensor and KCM. The cans diaphragm blow out and either need a rebuild or replacement. I bought new some years back for EA82T and drove better than one with a hole in it

I have an urge to merge an old EA81 with a turbo without any decompressing. I have an old engine with 300,000 miles on it with compression pressures of about 170 180 psi and another with a cam spec'd for turbo, 60,000 miles on since full rebuild with what I call compromise pistons that suit EA71,81 and 82 that give only 160 psi comp test. I have an EA82T that gives out 150 psi comp test even though turbos were supposed to only have 120 or 130 factory !

 

Word is from one experienced with turbing boxers on NA is that they dont last - but maybe if driven nicely it will ....

[john in KY]

Pull the spark plugs and look for black specks on the white porcelain.  If the porcelain is pure white but speckled with spots, go with a colder plug. 

[carfreak85]

Cronan, you're in uncharted territory here.  Over the years there have been a handful of members who have toyed with high -compression turbocharged engines, but most (if not all) of those were of the EA82T flavor.

 

As others have mentioned, I am 100% confident that you are closer to 8.0:1 compression, which isn't something that would throw this engine for a loop, the factory electronics should still be able to control the combustion event.

 

My guess is that you have inadequate fueling (clogged filter, injector with bad flow, etc.) or the base ignition timing was not properly set.  Also, be sure there aren't any cracks/leaks in the induction system that would allow unmetered air into the engine.  This could cause a lean condition that would promote detonation.

[coronan]

Thanks everyone!

 

I'll have a look at my plugs this weekend.

 

For the distributor.   If i put a vac pump on it and it holds vacuum the canister is good, right?  

Just want to be sure before I drop $200 in a new dizzy.

 

Compression Ratio Math.

Head volume per cylinder was machine to  40 cubic centemeters.

 

EA81 Displacement:  1,781 cc

Displacement per cylinder = 445.25  cc

 

40/445.25 = 11.13

But ratios need to be reduced to an equivalent fraction.

 

 

 40      =       1

------           --------

445     =      11.1

 

 

I tried to be meticulous when I had the heads off.  I let the injectors soak in injector cleaner.   Checked spray pattern and flow rates with a stop watch. (crude but better than not at all.)

 

They all flow the same.  And spray the same.   Although I have seen injectors spray better in the past. I know nissan injectors have higher flow rates.  but not i confirm i have a lean condition with wide band O2.

[86BRATMAN]

Your compression calculations are off. You have to know the compressed thickness of the head gasket, volume of the dish of the piston, piston to deck height, combustion chamber volume, and bore/stroke of the engine. Several of these variables are unknown to me. If you or anyone can chime in with these figures I'll be more than happy to calculate the ratio for you.

[carfreak85]

It is not physically possible on this engine to achieve a 10:1 compression ratio just by shaving the heads.  Period.  Full stop.

 

Also, the Nissan injectors are the same part, same flow.  Most manufacturers run about 43 psi of fuel pressure on non-DI engines.  FI Subarus of this vintage use somewhere in the neighborhood of 35 psi.  Crank that up to 43 psi and you magically get flow rates that match the Nissan part.

[jono]

i wish some of those who have had failed high comp turbo boxers would speak up !

I suspect that it may be possible the failures have been a case of a turbo slapped on an old NA and then run to see what happens, and likely pushed hard, maybe not had correct engine management and blown an old bearing or something as a result.

 

My thoughts could be swayed if someone came in and said they had a proper rebuild of a high comp turbo boxer, driven conservatively and still blown a big end or something .....

[coronan]

Compression is 105 psi each.

 

I spoke with someone who said if the EGR is not working EGTs go up 400 - 600 deg F.

My vacuum hoses were new but not fitting tight enough on the egr.  (NOTE: SMOKING GUN)

 

I pulled vacuum on the Egr actuator and it holds vacuum and i can hear it move.  

 

I cant see any metal flake on the spark plug porcelain.  I tried taking a pic but my phone wouldn't focus.

 

I am going to try running ngk b8es spark plugs.  Its one of the coldest plugs available.  The tech at NGK said if it knocks with that plug in the problem is not the plug.    

Vacuum Diaphragm in the distributor is bad.  (smoking gun #2)

[BratRod]

Good luck with the vacuum advance. I ended up buying a whole new distributor.

[coronan]

I found a few good threads dealing with the bad vacuum advance.

It should be considered an epidemic on our 30 year old cars.  This forum needs  "How to" section.

 

Someone figured out that the 82 honda civic still has this part available.  ($30.) while not cheap;  Its cheaper than a new dizzy ($170)

A slight modification is required.

 

This company rebuilds Dizzys

http://www.philbingr...istributors.htm

[BratRod]

There is a How To section. USRM (ultimate Subaru repair manual)its further down the main page.

 

I thought about rebuilding it myself. But it also retards timing under boost. I didn't want to take the risk with such a rare engine.

 

I'm the one who found the 82' civic part. Works great!

 

Also tried to contact Philbin multiple times. Never got a response.

Edited April 10, 2016 by BratRod

[coronan]

With the egr hooked up and cooler plugs my knock is gone.

 

 

BratRod,

Do you know what range of advance you are using?

Idle?

Rev?

on boost?

Edited April 10, 2016 by coronan

[BratRod]

I'm not sure on the EA81T

[coronan]

Is the Honda civic vac advance on a turbo car?

[BratRod]

The civic advance was for my N/A Brat. They both share a similar Hitachi distributor.

 

I could not find anything that looked remotely close to the turbo distributor.

[coronan]

So I got to talk to Philbin on the phone Yesterday.  I was not impressed.  He couldn't answer any of my questions.  Like what is the difference between Turbo and Naturally Aspirated Dizzys.

 

He quoted $175 to rebuild my Dizzy (2 days turn around once he had it.)  I told him i can buy a complete spare distributor for that much.

 

I said I just need a Vacuum Advance Actuator:  That's $75.  He would prefer to rebuild mine, rather that ship me a new one.  

 

Overall I was not impressed.

 

I get the Honda Civic Vac unit on Wednesday.  We will see how that works.  I"ll post up what i see in the way of Advance / Retard.  

 

If a Replacement Dizzy is nearly $200.  Why not go Distributorless Ignition????

I know this is where the EJ Preachers get on their soap box.   But an Aftermarket Ignition could grow with me, If i ever did a swap down the road.  (Did i take the wind out of your sales?)

 

Anyone done it on a EA motor?

 

This guy put on on his Legacy:

http://www.surrealmirage.com/subaru/mod.html

 

Quote:

MSD Dis-2 Ignition & Upgraded Diamond coil pack - I was pleasantly surprised with this addition. The word is that the MSD units don't produce much difference for the newer Subaru's, but for the first generation engines, they do. When I added mine I also upgraded to the Diamond Subaru coil pack. The Diamond coil packs come standard on the manual transmission equipped cars. They are supposedly able to handle a little more power.

Results, better throttle response in the low & mid range, as well as a little more power throughout the rev range. Would I do it again, you bet. Only down side is the cost, the MSD unit runs about 300 bucks. Check out pics in the image gallery.

Edited April 12, 2016 by coronan

[turbosubarubrat]

Look at ea82t setups people have gone to distributorless ignition setups with them.

[carfreak85]

I think the 105 psi of compression per cylinder would be a bigger worry than anything else.  I don't have my FSM in front of me, but I would expect 150-170 psi from a healthy engine.  130-150 for a tired engine and anything below that would need a rebuild.