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Recommendations On Building 9+CR EA82T?


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15 replies to this topic

#1 NorthWet

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Posted 10 September 2004 - 03:31 PM

Anybody have suggestions/experience building an EA82T with higher compression-ration pistons than stock? I remember seeing someone that had around a 9.5CR.

I am not asking for info on pros/cons of N/A-level CRs with Turbos. I have a decent book-lernin' background.

I am wanting to know whether starting with EA82T block and using N/A pistons (and maybe crank/rod assembly) works. Can an EA82 N/A shortblock be used, or does it lack essential passages and/or mounting bosses? I have plenty of EA82T shortblocks to look at (and cracked heads!!!), but no N/A block to compare with them.

Also, someone had mentioned a possible source of studs to convert from headbolts. I think it was ARP, but they didn't have the exact size replacement. Any contact info?

Thanks for any wisdom that you can pass along!

Pat

#2 NorthWet

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Posted 10 September 2004 - 03:34 PM

I really did type "compression-ratio", not "-ration"! I am not ig-no-rant, just have a nasty papercut on my typing finger.

TTFN!

#3 calebz

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Posted 10 September 2004 - 03:48 PM

I am in the middle of an 8.5:1 Turbo build.. hoping to finish tonight or tomorrow.only thing the block is missing thus far is the PCV hole.. The boss is there, but not drilled thourgh. I suppose if you wanted o get real enterprising, you could drill it out, but I don't plan to.

I know if 2 others running 8.5:1 turbos(carb block)

only 9.5:1 turbo (SPFI block) I have seen went kaput

#4 All_talk

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Posted 10 September 2004 - 03:57 PM

only 9.5:1 turbo (SPFI block) I have seen went kaput


But wasn't that with higher than stock boost?

Its all a balance of CR, octaine, timing, boost and intake charge temp. Personal I think a 9:1ish CR should work fine with a good IC and prem fuel. I'd like to build an engine with SPFI pistons and hemi cut/unshrouded valve heads, target CR would be 8 to 8.5.

Oh the things I could build if I were rich with no job.
Gary

#5 NorthWet

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Posted 10 September 2004 - 04:17 PM

All_talk: I have one of the two commodities that you wished for... two guesses which one!!!

Actually, its all about management of endgas. I have read a lot of c**p about what causes detonation, and how much advance you should run, and what high octane fuel does. Although the real world makes a mockery of laboratory "facts", if you don't understand the fundamentals you end up chasing your tail.

Anyway, how about an air-to-chilled-water IC and supplemental fuel coming from liquid propane injection rather than larger/more standard injectors? If done right, intake charge temp could be brought down to just above intake icing temp.

Add some way to induce a little more combustion chamber turbulence...

#6 All_talk

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Posted 10 September 2004 - 05:10 PM

Anyway, how about an air-to-chilled-water IC and supplemental fuel coming from liquid propane injection rather than larger/more standard injectors? If done right, intake charge temp could be brought down to just above intake icing temp.


Now were talking... I like the way you think.

I know what you mean about factual information, you never get access to the factory engineering and so much of the aftermarket research is seat-o-the-pants/trial-n-error, not that it doesn’t work well, it’s just with out engineering data to work with its very hard to extrapolate from and build on what others have done.

As far as a hi-po bottom end for the EA82… I think there are a few tricks we can borrow from the air-cooled VW guys as the cases are a very similar design (and they squeeze up to 200hp out of a motor that started with 65hp). Forged pistons (affordable) are a real stumbling block, I think the stockers should be good for 180ish hp with a extended RPM range (8000ish), but forged sure would be nice. Has anyone looked at sourcing them from another engine, maybe with some mods?

Somewhere around Dec I should be getting some machining capability in my home shop… then things could get real interesting.

Gary

#7 NorthWet

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Posted 10 September 2004 - 05:41 PM

My underlying goal is to get the better thermal-efficiency (gas mileage and low-end power) that the higher CR can give, while still having the punch and altitude-mitigation of the turbo. Although it would be fun to talk about boosting to 20PSI, my daily driving doesn't need it (.... yet, my precioussss...). So I am willing to trade a little brag-boost for better everyday power. I also don't want the drawbacks of running hi-octane gas when it is unneeded for 90+% of my driving.

I think this is doable with proper charge-cooling, combustion chamber shape, mixture control, spark control... and maybe imaginative use of some EGR.

So, SPFI has the highest standard CR?

Any idea if combustion chamber shape is pretty standard for all EA82s?

#8 subaru_styles

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Posted 11 September 2004 - 01:31 AM

yes the spfi has the highest CR.


mudrat79 and I are both running carb blocks with all the turbo top end stuff. this setup gives you more low-end and more "power" with stock boost.as compared to having to jack the boost way up.

#9 All_talk

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Posted 11 September 2004 - 09:10 PM

My underlying goal is to get the better thermal-efficiency (gas mileage and low-end power) that the higher CR can give, while still having the punch and altitude-mitigation of the turbo. Although it would be fun to talk about boosting to 20PSI, my daily driving doesn't need it (.... yet, my precioussss...). So I am willing to trade a little brag-boost for better everyday power. I also don't want the drawbacks of running hi-octane gas when it is unneeded for 90+% of my driving.

I think this is doable with proper charge-cooling, combustion chamber shape, mixture control, spark control... and maybe imaginative use of some EGR.

So, SPFI has the highest standard CR?

Any idea if combustion chamber shape is pretty standard for all EA82s?


You and I think a lot alike.

And yes, as SubaruStyles said SPFI is the highest at 9.5:1, from what I understand CR changes were all piston changes and all the head volumes (and assuming shapes) are the same.

I have often thought about some type of on demand octane enrichment, through grade mixing or “booster” injection but nothing seem practical. You propane proposition may have merit in this train of thought, not as a true octane boost, but boost controlled charge cooling would work to the same end. I did a little research on the available systems use for turbo diesels but they all use dry injection and we of course need the phase change to happen in the intake stream to get the cooling effect, looks like we may be on new ground here. One potential problem is that propane stays liquid at relatively low pressures near ambient temperatures, assuming decent intercooling, it may be a real balancing act between charge pressure and charge temp to get complete phase change (time to dig out the thermo books). Though I’m sure there would be enough heat in the cylinder to complete the change and I suppose the end effect would be the same.

Thoughts?

Gary

P.S. NorthWet, did you receive my PM? Anyway, I would like to learn more on the subject, can you point me to any articles or maybe we could talk some time and you could share what you have learned.

#10 Myxalplyx

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Posted 11 September 2004 - 09:24 PM

only 9.5:1 turbo (SPFI block) I have seen went kaput

I believe WJM simply forgot to turn his timing down or something to that affect. He just recently made a comment about it in another post. *scratching head*

Where is that long post anyway when he was going the 9.5:1 turbo block? It was really interesting.

Ahh...here it is.

http://www.ultimates...highlight=9.5:1

#11 NorthWet

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Posted 12 September 2004 - 03:40 AM

All_talk: I did get your PM earlier, along with one from another person whom my swiss-cheese memory fails to recall (and I am too tired/lazy to look up). Long day, started yesterday.

It sounds like I may have come across as knowing more than I really know. I definitely do not know all of the answers; and I am positive that many of you folk have far more practical knowledge, especially with soob motors, than do I. But I have messed with cars for a few decades and learned a few of the right questions.

After reading through a lot of the threads having to do with power, tuning. detonation et al, I have decided that not many people understand what effects detonation. In the end, almost everybody seems to want to know how much timing advance they can get away with running, like lots of advance is a de facto great thing. AAAGGGHHH! Timing advance is a bandaid, a compromise, and the last item in the string of conditions leading to or effecting proper combustion or detonation.

At the risk of sounding like I am lecturing:
Every degree of advance that an engine requires subtracts from the power that the engine potentially could generate; every degree of advance causes some amount of combustion pressure against the rising piston. The slower the speed of flame propagation in the combustion chamber, the more advance is needed to cause peak pressures after TDC. Lean mixtures, a given fuel's combustion characteristics, lack of combustion chamber turbulence and low compression pressure contribute to slow flame propagation. Large distances from flame initiation (spark) and far side of combustion chamber contribute to total time to burn the entire charge.

Detonation (as distinct from pre-ignition) is caused by spontaneous ignition of end-gas in the combustion chamber. (End-gas is whatever fuel/air mixture has not yet been involved in the flame front.) The spontaneous ignition is caused be the temperature of the A/F mixture reaching its flash point (I believe that is the correct term; I had only a little Organic Chem... and that was a couple decades ago), the temperature coming from original charge temp, heat radiated from the piston/cylinder/combustion chamber, heat caused by compressing the gasses, and heat radiated form the approaching flame front; it is reduced by any quenching during combustion by the relatively cool piston/cylinder/combustion chamber.

In addition, the flash point of the end-gas is lowered because the heat "cooks" the complex hydrocarbons and breaks many of them into molecules with a lower flash point. The longer the end-gas is exposed to heat, and the higher the heat, the more the flash point is lowered.

So, for a given hydrocarbon, the higher the heat and the longer the end-gas is exposed to the heat, the more likely that some of the charge will detonate.

"Hi-Octane" gas is just a mix of hydrocabon molecules (and some additives) that have a higher flash point, lower breakdown rate from "cooking", or both. But usually to achieve this, the blend of hydrocarbons makes hi-octane gas burns slower, requiring more timing advance in order to get the most power. At low power settings, H-O gasoline is not just a monetary waste but actually could produce a little less power than cheap stuff. So, in the end, hi-octane gasoline is not the best thing since sliced bread, but just a compromise that forestalls detonation a little bit.

Timing advance added on to all of this effects when peak pressure is reached and how big the peak is.

Ok, so much for the technical crap. If you understand the causes of detonation, you can work to mitigate it.
a) Lower the intake charge temperature.
B) Run an A/F mixture that has optimum burn rate.
c) Induce combustion chamber turbulence.
d) Shorten distance flame front has to travel.
e) Cool the end-gas.
f) Use a fuel with high flame propagation rate, lower breakdown, higher flash point.
g) Raise the engine speed.
h) Other???

I don't think many people think past a), if they think about it at all. They (those THEY people!) reach for premium and their timing light. Maybe they try to use extra gasoline for charge cooling effect (though overly rich mixtures burn slower than a slightly-richer-than-stoichiometric mixtures).

So, ideally what I would want to do is lower the intake charge temperature to around 35degreesF. If the final cooling occurred near the intake port I imagine the charge temp could go lower without fear of icing. This should be possible with liquid propane. It might even be possible to allow it to enter the combustion chamber as a liquid to achieve an even greater volumetric efficiency and additional in-cylinder charge cooling. Since the propane would only be added at high power situations, there should be plenty of heat within the cylinder to vaporize the liquid propane.

In addition, propane has a rather high "octane" rating, if I remember right somewhere around 110. (Natural gas is even higher, but less available in any usable form for a car.) It is a mix of simpler hydrocarbons that I believe are less susceptible to breakdown by "cooking". (Commercial "propane" is not technically really propane, which is a specific organic molecule. The stuff we buy is more accurately LPG, liquid petroleum gas.) I can not remember if I have seen any figures for its flame propagation rate.

Running straight LPG is kind of a waste (unless you run a very high compression). It is also harder to ignite (higher flash point) than gasoline, doesn't vaporize well when everything is cold, requires a heavy pressure vessel for a fuel tank, and has a lower specific BTU.

I would use an air-to-liquid intercooler (can be smaller than an air-to-air for similar BTU rating), plus use chilled-water to further improve the BTU rating. I have seen discussions on using A/C to cool charge air; some think it might be worth it and others disagree. I am inclined to think (haven't thought about it enough to run any numbers) that it would work, especially if cooling a supply tank instead of being sized to cool "on demand".

I have only recently learned (from you folks at USMB!!!) about MegaSquirt. I am very interested in it, being an incurable dreamer. EDIS also interests me, but seems like there should be an easier way of mounting a tooth-ring/sensor. I would be tempted to just use a sensor to detect flywheel teeth; more accurate crank-angle measurements could be possible. Except that a one-sensor solution would require me to remove one of the flywheel teeth...

One last thought before my screen runs our of ink: Has anybody thought of doing a timing-CHAIN conversion for EA82? Just a thought. Could be made more durable than the Gilmer belts, though introduces chance of chain stretch. It might also make interesting sounds!

Hope this post is not too long. Also hope that I don't come off as a bigger jerk than I really am.

#12 NorthWet

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Posted 12 September 2004 - 01:40 PM

Addendum to above:

Oh! An hour after I went to bed (why sleep when you can dream?), I remembered one of the "h) Other" ways to mitigate detonation.

Reduce peak combustion temperatures.

This is actually what EGR is used to do, but EGR is intended to reduce NOx formation. I am curious to find our whether EGR could be turned into our friend. Like, What happens to flame propogation rate and combustion efficiency at high power settings when charge is diluted with relatively large quantities of cooled exhaust? With forced induction, you wouldn't have to worry so much about lower max power...

Also, another 2am musing: With proper charge cooling, there should be little difference in chance of detonation between an engine running "X"-psi with 7.7CR vs same boost with 10CR. If charge temp at time of ignition is equivalent, then both should have similar end-gas conditions.

#13 ogordon

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Posted 13 September 2004 - 11:08 PM

I am running a mpfi from an 88xt , now with turbo. I set base timing at 15 degrees and run 94 octane. I have it in a 90 loyal 4w-4sat running stock boost.
I tried it in a 85 wagon 4smt with 12 lbs boost ,it ate a head, ported itself around the exhaust seat. So far 12k miles no probs. Daily driver 64 miles rt to work.

#14 oddcomp

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Posted 14 September 2004 - 10:03 AM

i don't have a hi comp turbo yet.. i may in the future
but after my recent engine management system change over.. where before i had alot of detonation
i no longer have it now
at 10 psi
and actually running a bit more timing advance with cheap gas

one of biggest things to worry about is getting enough fuel under boost
and timing both of mine are programmable on the fly
btw i have a intercooler but its not installed
and as such my intake temps at 10 psi max at around 220
and i have a max ignition advance of around 25-30 deg btdc under load at 10 psi i forget the exact advane i am running i will have to look it up

for extra or correct fueling outside of ditching the suby ecu and going programable the only other semi cure is running a extra injector on a either pressure switch or off a circuit that reads o2 sensor output and add extra fuel when it thinks it needs it
not perfect solutions but they do work

#15 NorthWet

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Posted 14 September 2004 - 11:48 AM

Realistically, how much did the meagasquirt&edis route co$t you? I am really interested in going that (or a similar) way, at least partially 'cause I hate "black box" controls that I can't easily play with.

#16 oddcomp

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Posted 14 September 2004 - 01:35 PM

well i built mine
parts case and stuff 140ish..
new updated codes to do more nifty stuff
free w00t
edis ignition parts .. wel the junkyard stuff anyways like
coil pack,edis module,vr sensor, and the pulley with the trigger ring on it
about 35 ish depends on the the mood of the junkyard guy it seems down here anyways

custom pulley or modified stock one.. i suggest custom . i fought with the stock one to combat slipping problems i ended up pinning my pulley so it could not slip
well.. not sure how much the pulleys cost.. as i suspect from the various peopel who ahve been helping me i may have gotten a smidge of a price break just so i could prove it possible to do on subaru's
i may be wrong and those who are offering pulleys feel free to chime in on prices

then the last part is time. not as much as i spent figureing out everything and building it
but time now all teh "hard work" is done :)

oh as well as a custom pulley to fit the timing ring on you also need a mount for the sensor that reads the teeth on teh crank pulley ring thing
i do suggest you get ahold of me on aim or yahoo under oddcomp
or msn under oddballcomp@hotmail.com alot easier for me.. anyways to answer stuff.. i get confused easy and forget things
lol :)
plus i can send pics of my setup that way




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