Increasing Compression

[Dessertrunner]

baza was I dreaming or did you tell me you have the standard cams in your motor?
Tony

[bazza]

Originally Posted by Dessertrunner

baza was I dreaming or did you tell me you have the standard cams in your motor?
Tony

That's right mate, standard cams at this point in time. They turn rather asthmatic around 550-600 bhp which from what I recalling Ecutune Mike saying it's mainly the exhaust cam.

[svxfiles]

OK, Tony,
On our stock 10 to 1 Compression Ratio engines we have 3318cc, or about 202.46 cubic inch displacement.
That should work out to 3.318 cc (or 20.246cid) above the piston at TDC.
You now have 11 to 1 CR on a 3.3L, or 202 CID engine, with a bore of 97mm, (roughly) or 3.815".
This has been done with different pistons. (As far as I know.)
So, the displacement, above the piston at TDC has to be about 301.636cc, (or 18.405cid.)
To get a 14 to 1 ratio the above the piston displacement now would have to be 237cc (or 14.461cid.)
Since there is only a reported 0.060" clearance,
and getting a thinner head gasket by say 0.030" would only increase the compression ratio up to about 12.384808 to 1 CR.
AND you still have the problem that Harvey mentioned that you have to "adjust" the cam sprockets to correct the timing.


No mate there is only 0.60" between the piston and the head, so you can't push them up any more. Shaving the heads is not the go as it will need adjustable cam pulleys to keep the timing right.
Higher comp pistons would be the best.

Harvey.

I have not heard of anyone welding the heads to increase compression, but it sure sounds more expensve than, and risky then a bigger bore resulting in both more displacement, and higher compression.

[Dessertrunner]

The reason I mention it is that it has been banned in some rules,

have anyone else heard of it being done?

[bazza]

Originally Posted by svxfiles

AND you still have the problem that Harvey mentioned that you have to "adjust" the cam sprockets to correct the timing.

Does anyone have any testing behind this with the EG33 NA motor and the results before and after dialing in the cams? Reason I ask is I don't think it makes any difference on our motors and if anything actually gains top end.

Reason why is I've done a fair bit successful AVCS tuning on the intake cam (02-07 STI heads). As most know it effectively advances the intake cam during low end RPM and you wind it back to zero as revs and air flow climbs.

The result is a massive improvement in low end torque. 0 advance gives the best top end (no bottom end) so theoretically a couple more degrees of retard will help with more top end. Also the exhaust AVCS works by retarding the cam as the rpm and airflow climb - retarding makes more top end power.

So in english, decking the head in an EG33 and the resulting timing belt effects which cause overall retardation of all cams should if anything make the car more powerful up top due.

[Dessertrunner]

Matt tried shaving the heads and had problems part because you can't buy adjustiable pulleys for the cams on our engines.

To get 14:1 how much has to be shaved off the heads?
Tony

[oab_au]

Originally Posted by svxfiles

OK, Tony,
On our stock 10 to 1 Compression Ratio engines we have 3318cc, or about 202.46 cubic inch displacement.
That should work out to 3.318 cc (or 20.246cid) above the piston at TDC.
You now have 11 to 1 CR on a 3.3L, or 202 CID engine, with a bore of 97mm, (roughly) or 3.815".
This has been done with different pistons. (As far as I know.)
So, the displacement, above the piston at TDC has to be about 301.636cc, (or 18.405cid.)
To get a 14 to 1 ratio the above the piston displacement now would have to be 237cc (or 14.461cid.)
Since there is only a reported 0.060" clearance,
and getting a thinner head gasket by say 0.030" would only increase the compression ratio up to about 12.384808 to 1 CR.
AND you still have the problem that Harvey mentioned that you have to "adjust" the cam sprockets to correct the timing.


No mate there is only 0.60" between the piston and the head, so you can't push them up any more. Shaving the heads is not the go as it will need adjustable cam pulleys to keep the timing right.
Higher comp pistons would be the best.

Harvey.

I have not heard of anyone welding the heads to increase compression, but it sure sounds more expensve than, and risky then a bigger bore resulting in both more displacement, and higher compression.

I did correct the 0.60" typo.

Yours is out a bit, I make it 42.5 cc for a 14:1 ratio.
Comp ratio is, swept volume, plus the clearance volume, divided by the clearance volume.

Yes welding the heads would be a huge job for very little return. There would be a big chance, that you would change the shape, to the detriment of the combustion turbulence, which would cost you a lot more than the 2% gain.

Harvey.

[bazza]

Originally Posted by Dessertrunner

Matt tried shaving the heads and had problems part because you can't buy adjustiable pulleys for the cams on our engines.

To get 14:1 how much has to be shaved off the heads?
Tony

Yeah I saw that Matt had some issues with the timing, but I'm keen to understand what the problems were... as I said my heads have also been shaved and the block shaved with no issues however as I said the turbo masks issues which might be far more prevalent in the NA. Of course if he won't over the Subaru limits then I'd understand it.

Also for your interest Tony, adjustble pulleys available on eBay.co.uk ... 400 pounds including delivery, just checked, search "EG33 pulley" or "EG33" etc.

[oab_au]

Originally Posted by bazza

Indeed - E85 is great stuff, however I've only played with turbo applications and don't have anything proven apart from my own theory in regards to NA applications. Also I've done quite a bit of research via SAE / engineering and university publications and it would seem that in the professional world E85 is accepted as a faster burning fuel in comparison to 98RON for engine combustion applications which is very widely mistunderstood through online forums it would seem.

Also the theory of E85 making more power is good, high compression + E85 will make more power. 98RON is such a nasty fuel that its very hard to get near the engines true potential due to detonation. Stock Subaru tunes are unbelievably aggressive. A mate of mine couldn't run more than 14 psi on street 98RON for example with the stock ecu running timing - major detonation. We put in E85 and a microtech to control fuel only and it was clearing 30 psi without a hint of detonation - car was absolutely ballistic. Timing was around 25 degrees at peak power. I think we could push it even harder and get close to 30 degrees and make a bit more. It actually snapped a rod it had so much torque. Engine now rebuilt to 2.2L with forged rods and running 25 psi with 25 degrees timing... madness!!

So I think trying to bump up the compression is a great idea. My own engine has had the block and heads shaved, a cometic head gasket and stock pistons. I'd assume the compression is a touch higher than stock. One thing in turbo applications is to actually use E85 and reap proper benefits you need high compression - something I've noted is the low compression turbo engines don't get the gains as the high compression ones.

Also did a 2 second image search for E85 vs 98RON in NA applications - this is a random V8 I found:

Giday Bazza, good to see you over here.

E85 is a good fuel, if full advantage is taken of it, but it is a case of what is the engine going to be used for?
Like I can't imagine Tony using it, as he couldn't carry enough to get to the next pump.
For circuit racing, especially if the regs only allow, 'pump gas', you would use it. In your case it is almost essential to allow the boost that you use.
As I said before, it depends on what fuel you are going to use, and build the engine to suit. There is no real point in chasing a number, just to use it.

Harvey.

[Dessertrunner]

Were is Matt, would be good to see if he thinks shaving the heads has any futur?
I sent a email to Mike about high compression pistons but did not hear a single word back.
Tony

[svxfiles]

Originally Posted by oab_au

.

Yours is out a bit, I make it 42.5 cc for a 14:1 ratio.
Comp ratio is, swept volume, plus the clearance volume, divided by the clearance volume.

Sorry for the confusion, Harvey,
but I was speaking of the combined head volume,
for all six cylinders.

[svxfiles]

Originally Posted by bazza

Does anyone have any testing behind this with the EG33 NA motor and the results before and after dialing in the cams? Reason I ask is I don't think it makes any difference on our motors and if anything actually gains top end.

Reason why is I've done a fair bit successful AVCS tuning on the intake cam (02-07 STI heads). As most know it effectively advances the intake cam during low end RPM and you wind it back to zero as revs and air flow climbs.

The result is a massive improvement in low end torque. 0 advance gives the best top end (no bottom end) so theoretically a couple more degrees of retard will help with more top end. Also the exhaust AVCS works by retarding the cam as the rpm and airflow climb - retarding makes more top end power.
So in english, decking the head in an EG33 and the resulting timing belt effects which cause overall retardation of all cams should if anything make the car more powerful up top due.

Wouldn't it be retarded on the right bank and advanced on the left bank?
Or do you believe that the tensioner would equalize the timing?

[bazza]

Originally Posted by svxfiles

Wouldn't it be retarded on the right bank and advanced on the left bank?
Or do you believe that the tensioner would equalize the timing?

Prolly, I drew it all up before on paper but then confused myself again lol. Need to spend more time figuring it out.

[svxfiles]

Actually I gave it a little more thought and I believe that the right bank would be a little retarded, and the left bank would have double the amount of retard because all of the slack,
(Due to a shorter distance from the crankshaft to the camshafts)
would be between/after the left camshaft and the crankshaft.
Left cam is 0.030" shorter,
Right cam also 0.030" shorter,
ALL belt slack is adjusted out after the left cam


SO, get custom pistons to up the compression ratio if you like,
cuz shavin heads won't do it.

[Dessertrunner]

Two questions
If shaving the head is the way to go how much needs to be shave to increase it to 14:1.

Does any one know were to get the piston if thats the way to go.

Harvey the higher compression is for the race car.
Tony