Is high compression on the cheap possible on an A20? (pump gas)

[POS carb]

I'd like to raise the compression on my motor but I don't want to spend $$$ on custom pistons. The car is cheap and so am I.

I've heard of shaving the head but I don't know if it's possible on this car with valve clearance and the timing belt length.
Anyone gone this route?

Maybe pistons can be used from another Honda, or crank/rods to make a stroker (stroking a motor raises the compression with the same pistons)

I've heard of people using Vitara pistons in Civics to drop the compression for high-boost applications, I'm trying to go the other way because the car is carbed

[Oldblueaccord]

Interested as well. I want to do a full e85 build.

[2drSE-i]

Longer rods is a good possibility. B18C1 rods are .7mm longer, which won't make a huge difference. You could always look into some custom rods, the next available OEM length is 141.5, which will probably be too long. Either way, you will either need a matching set of pistons, or have your OEM ones modified to accept the larger wrist pin.

[2drSE-i]

I take that back, according to Zealautowerks calculator, a 137.7mm rod length would put us about .5:1 higher. Makes almost 0 difference in Rod/Stroke ratio, but definitely effects compression.

[MessyHonda]

you can weld the combustion chamber so the head only has room for the valves. use fuel injected pistons as they are 9.3

[POS carb]

How can longer rods change your compression?
I understand rod/stroke ratio but if your piston starts higher it will just travel the same distance down the cylinder with the same crank giving you the same compression but worse piston to valve clearance

As for welding the combustion chambers that sounds like something a very experienced machine shop would have to do but I'll keep it in mind

If I look up replacement pistons for this car they are all the same part number no matter the year or submodel. I guess I would have to get them out of a junkyard LXi/SEi

[derolph]

How can longer rods change your compression?Seems obvious to me. If the pistons come up higher in the cylinder when they reach top dead center, that compresses the air/fuel mixture into a smaller space.

I'd say using the technique to increase compression carries some risk, such as greater chance of blowing a head gasket. I think I'd look for other ways to tweak performance. I can't give examples because this is not an area I've delved into. Some other members here may have some tips on this.

[cygnus x-1]

Using longer rods might work but I bet it won't be cheap. And adding 0.7mm to the rod length will only get you about 0.5 compression points.

By far the cheapest option is to mill the head. My experiments indicate that you should be able to mill up to 2mm off the head without running into problems with the coolant passages. It should still be safe with the valves too but so far this is just theoretical. I've never heard of anyone that actually tried more than about 1mm off. Milling the head will alter the cam timing a bit so you might want to get an adjustable pulley if you want to push it very far. You wouldn't have to though, it won't change a lot.

If you start with A20A1 pistons the stock compression ratio is about 8.8:1. Taking 1mm off the head will get you to 9.4:1. 2mm will get you 10.2:1.
If you start with A20A3 pistons the stock compression ratio is about 9.1:1. Taking 1mm off the head will get you to 9.9:1. 2mm will get you 10.8:1.


Welding up the combustion chambers is a decent way to go too as it doesn't affect cam timing or valve clearance. The question though, is how much difference can you make with this method. I only know of one instance where it was done on an A20 (the old Open Loop car had a welded up head. There may even still be pictures somewhere), but I don't recall there were ever any measurements taken. It would need to be done by a professional but it's not an especially exotic thing to do. The casting I'm planning to use for my big valve head (whenever I get around to finishing it) had some pitting corrosion around the coolant passages that had to be welded up. It wasn't any big deal for the shop that did it. Combustion chambers would be more difficult since you have to be careful of the valve seats, but it's not that big a deal. Probably the harder part will be grinding the chambers back down again to get them evened out to all the same volume.


Another option is to put in some domed B series pistons and rods. Not going to be very cheap though.


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[AccordEpicenter]

Using longer rods might work but I bet it won't be cheap. And adding 0.7mm to the rod length will only get you about 0.5 compression points.

By far the cheapest option is to mill the head. My experiments indicate that you should be able to mill up to 2mm off the head without running into problems with the coolant passages. It should still be safe with the valves too but so far this is just theoretical. I've never heard of anyone that actually tried more than about 1mm off. Milling the head will alter the cam timing a bit so you might want to get an adjustable pulley if you want to push it very far. You wouldn't have to though, it won't change a lot.

If you start with A20A1 pistons the stock compression ratio is about 8.8:1. Taking 1mm off the head will get you to 9.4:1. 2mm will get you 10.2:1.
If you start with A20A3 pistons the stock compression ratio is about 9.1:1. Taking 1mm off the head will get you to 9.9:1. 2mm will get you 10.8:1.


Welding up the combustion chambers is a decent way to go too as it doesn't affect cam timing or valve clearance. The question though, is how much difference can you make with this method. I only know of one instance where it was done on an A20 (the old Open Loop car had a welded up head. There may even still be pictures somewhere), but I don't recall there were ever any measurements taken. It would need to be done by a professional but it's not an especially exotic thing to do. The casting I'm planning to use for my big valve head (whenever I get around to finishing it) had some pitting corrosion around the coolant passages that had to be welded up. It wasn't any big deal for the shop that did it. Combustion chambers would be more difficult since you have to be careful of the valve seats, but it's not that big a deal. Probably the harder part will be grinding the chambers back down again to get them evened out to all the same volume.


Another option is to put in some domed B series pistons and rods. Not going to be very cheap though.


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i really think welding the combustion chambers is the way to go. its the most cost effective. Changing pistons and rods is a total waste for a modest increase in compression ratio. Just how much more power do you guys think you are gonna make with this? The only way to realize any potential hp gain is to go obd1 and get a tune, and even that wont be much unless you add a intake, header/full exhaust and possibly cam...

Openloops LX-i coupe is a perfect example

[POS carb]

I have the intake carb and full exhaust. I'd definitely put a cam in there, they're cheap. I just didn't want to run into a shitty weld job that causes hot spots in the combustion chamber, I figure any shop can mill a head easier/cheaper.
I just want to add some grunt the old fashioned way. This car is not worth the expense of a turbo or even an efi conversion
How much advance/retard can I get by just moving 1 tooth on the stock cam gear?

[POS carb]

http://carphotos.cardomain.com/ride_images/1/3036/2781/7588890055_large.jpg
It looks like there are 42 teeth... so 360 divided by 2 (cam spins at 1/2 speed) divided by 42 equals about 4.3 degrees???? sounds like too much
not sure how many degrees a mill would retard

[lostscotiaguy]

Did someone say cam? :)
http://www.paeco.com/Honda%20Cams.htm

[cygnus x-1]

I have the intake carb and full exhaust. I'd definitely put a cam in there, they're cheap. I just didn't want to run into a shitty weld job that causes hot spots in the combustion chamber, I figure any shop can mill a head easier/cheaper.
I just want to add some grunt the old fashioned way. This car is not worth the expense of a turbo or even an efi conversion
How much advance/retard can I get by just moving 1 tooth on the stock cam gear?


1 complete tooth would be 360/42 ~= 8.5 deg. The crank spins twice the cam speed so that would be about 17 crank degrees. That's a lot, which explains why peoples engines run badly when the timing belt if off even 1 tooth.

I measured the cam pulley at ~4.75" diameter, so after converting to mm that's about 380mm circumference. 1mm off the head would be 1/380 * 360 = 0.95deg, which would be about 2 crank degrees. Not enough to matter a whole lot, although it might be measurable on a dyno if you took a bunch of runs.


After welding you would have to go after the chambers with a grinder to smooth everything out and equalize the volumes. Done correctly it can give a fair amount of improvement. But you're right, it takes more skill (and therefore cost) so milling will be cheaper.


Incidentally, if you wanted to build an engine for E85 only you would want to be in the 12-14:1 range. I was toying with the idea awhile back and figured out that you would need to weld up the chambers and mill about 2mm off the head to get into that range. Or use custom domed pistons. It would be an expensive project and now you're stuck running E85 or race gas only.


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[Oldblueaccord]

Yes I'm thinking with Al heads 12.5 compression would be a start. it would be nice to flip back and forth between gas and e85 but be hard to do and have a nice e85 build.

[gfrg88]

Make it a true Flex-fuel car :)

http://proefi.com/info/applications/honda/

[2drSE-i]

1 complete tooth would be 360/42 ~= 8.5 deg. The crank spins twice the cam speed so that would be about 17 crank degrees. That's a lot, which explains why peoples engines run badly when the timing belt if off even 1 tooth.

I measured the cam pulley at ~4.75" diameter, so after converting to mm that's about 380mm circumference. 1mm off the head would be 1/380 * 360 = 0.95deg, which would be about 2 crank degrees. Not enough to matter a whole lot, although it might be measurable on a dyno if you took a bunch of runs.


After welding you would have to go after the chambers with a grinder to smooth everything out and equalize the volumes. Done correctly it can give a fair amount of improvement. But you're right, it takes more skill (and therefore cost) so milling will be cheaper.


Incidentally, if you wanted to build an engine for E85 only you would want to be in the 12-14:1 range. I was toying with the idea awhile back and figured out that you would need to weld up the chambers and mill about 2mm off the head to get into that range. Or use custom domed pistons. It would be an expensive project and now you're stuck running E85 or race gas only.


C|

Or you could get longer rods :)

141mm Rods would put you at about 14.5:1. Assuming we have room for rods that are 4mm longer

[Legend_master]

Or you could get longer rods :)

141mm Rods would put you at about 14.5:1. Assuming we have room for rods that are 4mm longer

14.4:1 sounds like a valve smasher!

[AccordEpicenter]

14.4:1 sounds like a valve smasher!

milling will work fine, yes. But you can forget going E85 with the stock carb type setup. Youd need a seriously modded carb to account for the e85. To support the same hp level on 85 youll need about 40% more fuel than gasoline (richer mixture) to make the same hp. So if you just want a little added kick, get a reground cam, and have the head milled to up the compression, then set the timing back to stock and rock it as is with the exhaust/setup you already have. I wouldnt even bother for e85 plus itd prolly corrode the carb badly.

[cygnus x-1]

Even if you had a totally flat top piston and ran it all the way up to the head surface you would still only get around 11.5:1 compression. The combustion chamber is just too big. You would need some big carbs to support it too (if you want to stay low tech).

Somewhere around 10.5:1 is probably a good target for regular pump gas.


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[rjudgey]

Other option is my route, A20A3/4 pistons oversized to 83mm, then skim the head 1mm (1.5mm is fine too I've gone that far), deck the block .5mm then look around for a rare A18 head in good condition (that's the hard part!) this should get you easily to 11-11.5:1 higher if you go further on the head skimming to 1.5 - 2mm off. If your not running huge lift this should be fine my engine has 33mm inlet and 37mm exhaust valves currently and the pistons are stock A20A3/4 without pockets increased in size run a 285 degree cam with 10mm lift and I've had no issues what so ever with valve contact happily revs to 8500rpm all day long! :) But you do need to check clearance with what ever you go with using plastigauge or similar because every engine is different and so are the parts depending on when they were made etc.
Instead of wasting good money on aftermarket rods I'd say just make up some custom pistons for the stock rods with flat tops and only 3 valve reliefs per piston this combined with bit of head skim and deck skim should get you high enough CR ration I don't like domed pistons as they don't put a nice even spread of combustion on the piston and also added stress on our already weak choice of head gaskets.

[rjudgey]

BTW having longer rod means you'll have to chamber match the head to the bores and make sure it's perfect because anything sticking out will get clouted by pistons coming up, I know the head gasket is thick but .7mm with a deck to the block to flatten it square for rebuild could be a close call. Although when cold the difference is ok when the engine has heated up and at maximum revs you could end up a lot closer than you think! Plus all the aftermarket rods are much heavier, if your using as N/A engine better off with stock rods, have them balanced, polished and stress relieved new lighter wrist pins and re torque the stock bolts to 35lbft instead of 25lbft and use loctite. I've only had one instance of rods failing and that was due to a mate of mine that missed 5th gear and planted it into 3rd gear at 140mph the rods or bolts stretched and after a few hundred miles two of them failed and went straight through the side of the block :( Other than that every other stock rod I've used and have been many have been fine on a N/A engine and all revved happily to 7500-8000rpm.

[MessyHonda]

you will need a head to flow really good to get the motor to spin up got 8.5k. also he has carb trans so the gears are long. i had teg gears in my trans and the motor used the powerband much better. personally i would not rev the a20 more than 7500rpm

[Oldblueaccord]

1 complete tooth would be 360/42 ~= 8.5 deg. The crank spins twice the cam speed so that would be about 17 crank degrees. That's a lot, which explains why peoples engines run badly when the timing belt if off even 1 tooth.

I measured the cam pulley at ~4.75" diameter, so after converting to mm that's about 380mm circumference. 1mm off the head would be 1/380 * 360 = 0.95deg, which would be about 2 crank degrees. Not enough to matter a whole lot, although it might be measurable on a dyno if you took a bunch of runs.


After welding you would have to go after the chambers with a grinder to smooth everything out and equalize the volumes. Done correctly it can give a fair amount of improvement. But you're right, it takes more skill (and therefore cost) so milling will be cheaper.


Incidentally, if you wanted to build an engine for E85 only you would want to be in the 12-14:1 range. I was toying with the idea awhile back and figured out that you would need to weld up the chambers and mill about 2mm off the head to get into that range. Or use custom domed pistons. It would be an expensive project and now you're stuck running E85 or race gas only.


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Was thinking if you used a reground cam you could tell them you wanted it reground 2 degrees advanced.

[rjudgey]

You can easily modify the stock cam gear to cover that if you wish but a ally one would be better as you can easily adjust the range and find the sweet spot of the cam for the most power.

[rjudgey]

Accord gears aren't that bad 1-4 are ok just 5th is pretty tall always splash a bit of NOS on! :)

A20 that's blueprinted can handle 8500rpm easy mine kinda proves that! But we weren't talking about revs was just using mine as example of what you can achieve on a ghetto build. As all my engines use stock OEM parts just everything is hand assembled and blueprinted. Only thing that isn't stock is the inlet manifold, carbs and a few custom valves you can use old exhaust valves as inlets and have 4 new custom stainless big valves done.

I suppose if your increasing valve size this will decrease chamber volume size so you can't rule it out! lol! especially if you have no dish in the valve heads so they're nice and flat.

[gfrg88]

What about destroking, using an a16 crank? Wouldn't that be a lot more rev happy without much problems? Has anyone tried that?

[cygnus x-1]

What about destroking, using an a16 crank? Wouldn't that be a lot more rev happy without much problems? Has anyone tried that?

The idea has been brought up before, but I've never heard of anyone trying it. It would be interesting to try, but I'll keep my low end torque thank you. :)


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[Oldblueaccord]

What chamber cc,s are you using for your compression calculation?

[rjudgey]

No replacement like displacement and at the end of the day the rod stroke ratio is way better than B20A it's also pretty similar to B18 which has no issues revving away! and we have extra 200cc to boot! Plus my engine definately has no issues with high revs and it picks up revs so quickly compared to modern engine with their heavy counterweighted cranks, double cams, and extra 4 valves plus vtec valve train. With a custom header I'd easily expect peak power to increase in the rev band as well as overall probably to something like 7800-8000 rpm and power to be at 210-215bhp. With a decent camshaft with more lift and little more duration I'd expect to see 220-230bhp at 8000-8200rpm with a still a decent torque figure of around 170-180lbft at 5750-6000rpm.

Even as it is I have lots of low down power and with the car weight being so low it picks up really quickly from lower revs it's quite driveable on the road just in traffic it's tricky with lightweight flywheel so can hop around a bit.

I think with a nice set of forged pistons oversize in 83.25mm with titanium wrist pins, possibly titanium rods from Eagle for B series, coupled with the header, camshaft and some better designed titanium valves and retainers this engine could potentially get near 250bhp mark. Although I'd still kill to find out what King motorsport did to get 340bhp!!

[hatch88lxi]

Still a bit confused on the b18c1 rods! can we use them and still mill the head? can we use them at all without any mods? and will they bolt right up?

[cygnus x-1]

What chamber cc,s are you using for your compression calculation?



I'm using 47cc. This was measured on an A20A1 head I rebuilt in 2006.




Still a bit confused on the b18c1 rods! can we use them and still mill the head? can we use them at all without any mods? and will they bolt right up?

Not directly because the wrist pin diameter is 1mm too big. You could is you used B18 pistons.


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[hatch88lxi]

sorry to thread jack, but is it possible to mill the head 2mm and use the b18c1 rods and pistons without have any interference or valve issues?

[cygnus x-1]

sorry to thread jack, but is it possible to mill the head 2mm and use the b18c1 rods and pistons without have any interference or valve issues?

Umm, maybe? This is kind of getting into an area where no one has gone before. 2mm off the head will mean that the valves are protruding below the head surface at max lift, so piston shape and valve timing are going to matter a lot. What goal are you trying to achieve with this? There may be a better way to get there.


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[rjudgey]

You can't just drop B18 rods and pistons in it's not that simple, you need to make sure you have the engine bored to the size pistons your getting that you have the correct clearances for either stock cast pistons or aftermarket forged ones, forged pistons need more clearance as they expand more when hot. Also you need to check rod big ends clear the block castings especially if they're aftermarket as they'll be alot chunkier, and then also make sure that the bearings you use the correct size for your crank journals. You'll need to get rings that are preferably oversize and have them gapped to each bore size by hand, with 2mm off the head and B18 pistons your valve reliefs will be in different places to stock, with the pistons sticking out a tiny bit more than stock the valves are going to need to be clearing those, you may well have to machine a tiny bit off the valve relief pockets to make sure they clear, also you need to make sure that the chambers are bore matched as you could run risk that when engine gets very hot that the piston crown could hit the edge of the chamber walls. They'll be lot's of test fitting and using plastigauge to make sure things clear and there should allways be a little extra clearance nothing should just clear or it will end in disaster on a engine that's just run in and then warmed up fully. You'll also have to factor in what type of cam you'll be using, howmuch lift and duration, upgraded valve springs make sure the valve don't float at high rpm etc. Engines that are just chucked together tend to last minutes rather than years.

[gfrg88]

Just to clear things up, it's LS(B18A/B1) rods that we use. Not GSR ones. They're too long I believe

[Strugglebucket]

Welding up the combustion chambers is a decent way to go too as it doesn't affect cam timing or valve clearance. The question though, is how much difference can you make with this method. I only know of one instance where it was done on an A20 (the old Open Loop car had a welded up head. There may even still be pictures somewhere), but I don't recall there were ever any measurements taken. It would need to be done by a professional but it's not an especially exotic thing to do. The casting I'm planning to use for my big valve head (whenever I get around to finishing it) had some pitting corrosion around the coolant passages that had to be welded up. It wasn't any big deal for the shop that did it. Combustion chambers would be more difficult since you have to be careful of the valve seats, but it's not that big a deal. Probably the harder part will be grinding the chambers back down again to get them evened out to all the same volume.


Another option is to put in some domed B series pistons and rods. Not going to be very cheap though.


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Pic of Open Loop head. 44cc
5075

[cygnus x-1]

That's the one. ^^^^^

I wonder what ever happened to that head?

EDIT: Wait, is that 44cc the combustion chamber volume? If so that's only about 3cc less than stock, which is barely any difference at all. It has been reshaped though. Hmm.



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[Strugglebucket]

It's been a LONG time, but 44cc was the title I had saved the picture as.

I think that adding the quench zones would be as much of an improvement, if not more, than the moderate increase in compression.

[lostforawhile]

i like this thread, so basically shaving the head two mm would give you a decent bump in compression without too much trouble? Im going to be working on another engine eventually anyway

[cygnus x-1]

It's been a LONG time, but 44cc was the title I had saved the picture as.

I think that adding the quench zones would be as much of an improvement, if not more, than the moderate increase in compression.

Yeah, that could be. I think I would still mill a bit off that head just because.



i like this thread, so basically shaving the head two mm would give you a decent bump in compression without too much trouble? Im going to be working on another engine eventually anyway

Pretty much. The cam timing will (probably) have to be adjusted (it would be 4 degrees off). The valves should be ok but it would be a good idea to clay the chambers for confirmation. The only other potential issue is that the intake manifold might hit the coolant tube with the head 2mm lower. I mention this because the Manifold for my ITBs had really big bolt hole tabs on the under side, and would hit the coolant tube
even with an un-milled head. It might just be that particular manifold but it's a good thing to check. Grinding down the tabs helped but I also ended up modifying the coolant tube to sit lower on the block.


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[lostforawhile]

Yeah, that could be. I think I would still mill a bit off that head just because.




Pretty much. The cam timing will (probably) have to be adjusted (it would be 4 degrees off). The valves should be ok but it would be a good idea to clay the chambers for confirmation. The only other potential issue is that the intake manifold might hit the coolant tube with the head 2mm lower. I mention this because the Manifold for my ITBs had really big bolt hole tabs on the under side, and would hit the coolant tube
even with an un-milled head. It might just be that particular manifold but it's a good thing to check. Grinding down the tabs helped but I also ended up modifying the coolant tube to sit lower on the block.


C|

the intake manifold is not an issue in my case lol , I know when I was doing the timing belt and valve springs, with the piston on TDC the valve would go all the way to the retainer before it hit the piston, it might be different on the BS vs the later A series though, so add an adjustable timing gear and you are in good shape, do you think the 2mm will affect the head bolt torque or will you need shorter head bolts? something to ponder

[lostforawhile]

this brings up the methanol/water injection theory, normally you would use it on a boosted car, but this also would allow you to increase the octane rating of regular pump gas, and allow you to increase the compression without needing premium, I was looking at the technical setups in the snow kits, they have a stage one boost kit, which can also be triggered by any input, in non boosted applications, you can use an rpm switch, this would allow me to run 87 with high compression, and anything above about 4000 rpm,which is where they recommend spraying, no lower rpm, if it was setup to just above normal cruise rpm, it would prevent detonation when you were on the gas. it's a pretty simple setup, you can also adjust spray pressure up or down, it's not a power adder, it just cools the charge and effectively raises your octane rating. the tank can also be mounted at the rear of the car, the only issue I saw, and I will have to ask them, my intake splits into two Y runners after each carb, so i would need two nozzles one just after each carb. i dont mind running premium on a car that wont be driven every day, but the problem is, it's often not available here, when gas prices go up, a lot of the stations just dont order anything but 87

[gp02a0083]

the intake manifold is not an issue in my case lol , I know when I was doing the timing belt and valve springs, with the piston on TDC the valve would go all the way to the retainer before it hit the piston, it might be different on the BS vs the later A series though, so add an adjustable timing gear and you are in good shape, do you think the 2mm will affect the head bolt torque or will you need shorter head bolts? something to ponder

should be negligible and require the same torque. Nitro guys swap in / out different thickness head gaskets all the time to raise or lower the compression ratio. 2mm would affect the valve / piston clearance and timing as mentioned before.

[gp02a0083]

this brings up the methanol/water injection theory, normally you would use it on a boosted car, but this also would allow you to increase the octane rating of regular pump gas, and allow you to increase the compression without needing premium, I was looking at the technical setups in the snow kits, they have a stage one boost kit, which can also be triggered by any input, in non boosted applications, you can use an rpm switch, this would allow me to run 87 with high compression, and anything above about 4000 rpm,which is where they recommend spraying, no lower rpm, if it was setup to just above normal cruise rpm, it would prevent detonation when you were on the gas. it's a pretty simple setup, you can also adjust spray pressure up or down, it's not a power adder, it just cools the charge and effectively raises your octane rating. the tank can also be mounted at the rear of the car, the only issue I saw, and I will have to ask them, my intake splits into two Y runners after each carb, so i would need two nozzles one just after each carb. i dont mind running premium on a car that wont be driven every day, but the problem is, it's often not available here, when gas prices go up, a lot of the stations just dont order anything but 87


there is always debate in this area. People have the common misconception that a water / methanol injection kit is a power adder like N2O. To me it does not increase the octane rating. if anything it has a similar effect as a inter-cooler with compressed CO2 passing through it. You are putting combustion byproduct (water aka H20) in addition to a low / "cooler" burning alcohol. The reason this works is a thermodynamic and enthalpy characteristic. The water mainly serves as a anti-knock agent, the transition from a liquid state to a gaseous state can "absorb" a bit of thermal energy, allowing higher compression ratio's and / or boost. The alcohol mainly serves as a carrier for the water and anti corrosion agent to the injection system internals and helps atomize the water better to produce a uniform charge ( note injection nozzle style and spray pattern are other considerations). In our A20s with a 9:1 something compression ratio, i would say benefits of this are minimal if anything, unless the compression ratio is bumped to 10:1 or greater.

[lostforawhile]

thats my plan, one of the ways to build power is to increase compression, the reason for me wanting to add a system like this is if premium wasnt available, I could still run 87 with the system at higher RPM and not have to worry about knock, octane is nothing but knock resistance, and a system like this increases the effective octane of whatever is in the tank

[gp02a0083]

yes in that sense lost, octane rating is related to the knock characteristic, specifically the how well controlled the burn is. Hence why they add ethanol to most gasoline blends around 10-15% are common now. The ethanol does raise the octane rating, however it decreases the energy per unit significantly. At 20% ethanol the energy is nearly cut in half from pure Iso octane. So say an average of 12.5% ethanol is now used is roughly a 29% reduction in energy per unit. In your case Lost, you may have access from the
aviation field to chemicals such as MTBE (methy-tert butyl ether) which has been phased out and replaced with methanol / ethanol and was a really good anti-knock agent but it caused environmental issues. So going back to the water / methanol and or ethanol injection system. You are starting out with a fuel with 10-15% ethanol as it is, adding more ethanol and or methanol to the cylinder will effectively help with knock, but ultimately reduce the effective energy. I think that de shrouding the valves, properly gaping and indexing the spark plugs, welding up the combustion chamber, shaving the head, and domed pistons ( as other have mentioned to check valve clearance at TDC) should give a really good bump in compression , however this doesn't resolve the knock issue. Timing adjustment was always one way GM addressed the knock issue with their 80's cars.

In my honest opinion, i think the injection is more of a hassle than it is worth, you might as well just add ethanol to your gasoline or run E85, Or jsut keep adding toluene to your tank.

you also have to think of the compression ratio, you are mainly discussing about a static compression ratio not the dynamic ratio which is very different and always lower than the static compression due to a full air / fuel charge in the cylinder