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Old 08-08-2011, 11:04 PM   #1
Crystal_Imprezav
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Default High Compression, E85, and a Big Turbo - Experiences

So I just went from an effective 8.5:1 .030" quench Wiseco piston, cosworth cam setup to a 9.2:1 .038" quench high compression Manley pistons and Kelford 272/268 setup...

All things being equal, HTA3586 + FIC 1680 (at 53 base pressure); I am making 80-100whp less than before... This does coincide with what I have seen previously with high compression setups so I am not really shocked... I was hoping with E85, it would be different from C16 which is what I have dealt with in the past HC setups...

The car will take almost as much timing as before. It likes a little less down low around peak TQ but will take as much as before up top and not knock. However, it makes more power with 1-2* less than the previous setup which means it is at MBT at 1-2* less timing but it is still 80-100whp underpowered than my previous setup...

That being said, I really have yet to see someone prove that high compression in a Suby will make more power than the standard 8.2-8.5:1 compression we typically run even on E85 which should theoretically really optimize a higher compression ratio. Just a bunch of unproven hearsay of the typical "oh it spools faster" "oh it has better off boost" yada yada.

Let the discussion begin... No newb or unbacked data/opinions allowed
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Old 08-09-2011, 07:02 AM   #2
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What are the differences in torque? What I have always been told is you go higher compression for higher torque and it shouldn't have that bog at lower rpm. You are still low on comp but you are basically moving into the boosted N/A sector with the boost on higher comp. I will be slowly piecing together my build with the 9.8:1 CR manleys in my forester so I can put as much psi as possible from my also coming m90 supercharger build. It's all about what your using it for that makes the difference, just like building a drag or autox car, they are two completely different setups.
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Old 08-09-2011, 08:44 AM   #3
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I have no data to share as of now… I am still piecing my build together, but I do have lots of questions.

How does it feel now compared to before?
Is the off boost power difference noticeable?
Also, can you post some comparison graphs?
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Old 08-09-2011, 11:51 AM   #4
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Off boost is a little peppier but not much really. Retuning the off boost was a PITA but I guess that means I picked up some off boost response.

Torque is a function of power therefore less power means less torque. It does not spool any faster than before but this could also be due to my cam switch. Although given that I did a cam change plus the higher compression, I should easily be making more power. Theorectically that is...
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Old 08-09-2011, 12:03 PM   #5
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ok, a little fuzzy on the fuels for what?

Are you saying that you used C16 on the lower CR piston and made 80-100 hp more than higher CR on e85? OR was the C16 comment only for past high CR setups?

Are you listening for knock on e85 via the stock knock sensor or what are you using?

Why did you change quench height as it is a factor and also what is the difference in piston dish design?

Are you running the same boost levels for the two?

Now you're stating cam changes too...How many changes are their between your two setups? List the cams and AVCS timing changes too, please.
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Old 08-09-2011, 12:47 PM   #6
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E85 used on both setups. I was just saying I have played with high compression a few years ago with some ARFab stuff but that was on C16.

I have two knock sensor looking for knock.

Car made 80-100whp more on the older low compression E85 setup.

Piston dish design is similar. Just went from -19cc to -10cc (Wiseco to Manley pistons). I went to a .038" quench instead of the usual .030" from before because I was using a larger cam and wanted to make sure I wouldnt have any rod strech or AVCS issues.

Same boost levels for both.

Only changes to setup were the HC Manley pistons (from Wiseco's), went from stock to a .030" Cometic HG, went from standard to L19 head studs, and went from Cosworth Cams to Kelford R-199-C cams.
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Old 08-09-2011, 12:59 PM   #7
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199C 272/268 duration, 11.30mm/10.50mm

Cossie 278/274, 10.7mm/10.0mm

Really wish I had cam cards and actual lobe profiles for these
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Old 08-09-2011, 01:08 PM   #8
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I can take some pics of the cam cards when I get home later today.

The compression is definitely higher as well. Compression test yeilds 40psi higher per cylinder than the previous setup. The starter gets worked trying to start the car.
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Old 08-09-2011, 07:15 PM   #9
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Maybe a trade off between the ability of the IC to cool the boosted charge vs the amount of additional heat caused by the raise in c/r? The c/r jump is counterproductive to the effeciency of the IC/air charge into the cylinder to the point of deminishing returns? So if a 1 point increase c/r should net a 3% increase in power, maybe the additional cc heat is worth a 6% loss, for a net 3% loss?? IDK, but this is interesting to the point that it makes my head hurt thinking about it. Please keep this going, thanks for sharing.
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Old 08-09-2011, 10:44 PM   #10
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^^^Huh? I think you might be thinking about this wrong. Higher Comp Ratio should have nothing to do with how hot the turbo blows or how much the IC cools.

OP can you share a pre and post data log????

Interested in following the cam conversation
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Old 08-09-2011, 11:15 PM   #11
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Quote:
Originally Posted by gotsugg View Post
^^^Huh? I think you might be thinking about this wrong. Higher Comp Ratio should have nothing to do with how hot the turbo blows or how much the IC cools.

OP can you share a pre and post data log????

Interested in following the cam conversation

You misunderstood me or I failed to make my thought clear. The IC and its ability to cool x charge into the cc at x-cr will obviously not diminish as cr goes up. The efficiency, given the same IC set-up, environmental factors, and turbo, will be constant. Thats kind of what Im thinking about, the cr should improve power, but will increase cc temp. The IC has no control over this. So maybe there is a threshold where the increased power given from added cr coupled with the increased cc temp is detrimental to the pre-cooled intake charge to the point of netting a loss. Just looking for a logical 100hp loss, the vitals on the cam selection are above, Im not sure thats worth 100hp either way, but by themselves Im skeptical. Maybe the idea is way off; just throwing some gas on the fire.
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Old 08-09-2011, 11:16 PM   #12
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I'd still like to see the timing curve and boost curves on these.
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Old 08-09-2011, 11:46 PM   #13
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Ill get some logs up in a bit. Basically I hit 20psi in 3rd gear with the HTA86 at 4700-4800 rpm's with a pull starting at 3000rpm's. Timing has been tested everywhere from 6-14* at peak TQ to 14-22* at redline. The sweet spot is at 10-12* down low and 18-19* up top.

The car runs a minute bit warmer judging by coolant temps on the HC setup however IAT have not changed a bit. Temp's should not be an issue either way being I am running E85 and two step colder silver plugs.

What else you all got? Come on "professional" shops and race teams??? Someone prove me wrong and fuel the fire. I am as confused and disappointed as everyone else. If you google "high compression e85 turbo" you actually can't find any data besides opinions and butt dynos... Honestly the car feels fast but according to the data it is not as fast as before.
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Old 08-10-2011, 12:00 AM   #14
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Well, I was supposed to get my near 10:1 compression motor with cosworth 280 cams, big valves and 70lb/min turbo tuned today but couldn't due to a conflict. I will post up more info when I get it so check back in a few weeks.

As for Pros, Element Tuning is all about high compression. Moore Performance is too but they have only been building race motors for a year.
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Old 08-10-2011, 12:18 AM   #15
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IAT wont change with cr but egt and cc temp should be higher at the same AFR/boost/load points.

^ Yea call Ed and then tell me what he says (pending 9.5:1 E85 build).
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Old 08-10-2011, 12:21 AM   #16
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I'd honestly say put on more pressure and pull a bit of timing and see how things go. For a senior project engine, I was running 19 psi and 11.5:1 CR without an intercooler...of course then I was also up to 20k RPM with that engine. So det is more or less a non-issue over 14k or so with the rod ratio on that engine. The other issue with knock sensors is they are designed/calibrated for certain ranges of operation/monitoring.

Most all of my in-depth Subie experience is in the long rod/destroker realm which inherently likes higher CR.


I'm honestly not surprised that the lower duration exhaust cam isn't holding power out as well.
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Old 08-10-2011, 12:51 AM   #17
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I have experience with a small turbo a VF39 .

1- My stock engine EJ255 compression ratio 8.55:1 use to make 340-350whp on E85 with 30* of timing and redline. Trap speeds in the 1/8th of the miles were consistent in the 93-94mph.

2- The second engine was put together with JE slightly higher compression forged pistons that brought the compression ratio up to 9.0:1. Also adding to the mix BC 272 cams and ported heads. I was only able to make 320-330whp. Only making 330whp on really cold days running more timing and leaner. Most 1/8th trap speeds were in the 92mph.

I was disappointed about the peak power and the car felt the same down low to me.

and..


Quote:
Originally Posted by TopSpeed View Post
The cosworth pistons are expensive, but they are also the best we have used.

I can try to get exact weight savings for you, but I honestly don't know that off the top of my head.

The motor in Doug's old car is running great. The car has been sold, but we just tuned it again for the new owner a few weeks ago and it sounds great. No oil consumption and still running strong.

We absolutely do NOT offer high compression Subaru motors. It doesn't matter what type of fuel you are using high compression Subaru engines do not work well. The reasoning has to do with the size of the bore with the combination of how short the stroke is....it doesn't work! We have tried tons of different variations of them, and none of them make as much power as the factory compression.

Thanks for the questions.

~Cicio
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Old 08-10-2011, 01:02 AM   #18
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I don't think TopSpeed took all factors into account when making that statement...I'd be curious to see what engine platforms they tested the pistons on. Knowing them, I'm willing to bet it was only on EJ25 and stroker engines...

Wonder why Subaru was so dumb as to put higher CR on the Spec C which had the shortest stroke they make?

Once again I'll declare not being a fan of the EJ257 engine
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Old 08-10-2011, 01:30 AM   #19
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I think your doing something wrong to make 80-100whp less on E85 over C16, though I'd hardly call .7 higher in compression "high compression".

Although I have no experience with race gasses because I'm not going to pay $10 plus a gallon when I can get E85 for $3.19 and make the power I need to. From what I've seen on the evo side of things all the big name tuners IE AWDmotorsports, english Racing, Buschur, GST, and a handful of others say there is only one fuel better then e85 and that's VP import.

Have you tested the content of your fuel to verify that its infact e85 or better first off?
Second how are you tuning, with knock or with a dyno? Because tuning by knock on e85 is just plain stupid. You won't find true MBT at all. So either tune with street logs in VD or airboy or use a real dyno.

One car that I helped tune along the way with 10:1 compression did make 540whp DD 1.15 CF on a ATP 35R with a T3 hotside on e85 @ 26 psi, which was much higher then any other 35R setup subaru in the state could have made at the same level.

Otherwise I have no dyno sheets to backup claims with yet. There are two very large builds in progress that I'm going to be tuning that are both 10:1 on e85 so I'll be sure to report back with what they can do and possibly see what C16 does for reference.
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Old 08-10-2011, 12:17 PM   #20
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if you would have used the same cams, it would be a more fair comparison...so, it's merely conjecture.

I acutally made a thread on low compression, I don't think subaru's are lacking out of corners, so why high compression anyway? Our tuners have a lot less experience tuning high compression as well...
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Old 08-10-2011, 04:03 PM   #21
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Quote:
Originally Posted by project_skyline View Post
I think your doing something wrong to make 80-100whp less on E85 over C16, though I'd hardly call .7 higher in compression "high compression".

Although I have no experience with race gasses because I'm not going to pay $10 plus a gallon when I can get E85 for $3.19 and make the power I need to. From what I've seen on the evo side of things all the big name tuners IE AWDmotorsports, english Racing, Buschur, GST, and a handful of others say there is only one fuel better then e85 and that's VP import.

Have you tested the content of your fuel to verify that its infact e85 or better first off?
Second how are you tuning, with knock or with a dyno? Because tuning by knock on e85 is just plain stupid. You won't find true MBT at all. So either tune with street logs in VD or airboy or use a real dyno.

One car that I helped tune along the way with 10:1 compression did make 540whp DD 1.15 CF on a ATP 35R with a T3 hotside on e85 @ 26 psi, which was much higher then any other 35R setup subaru in the state could have made at the same level.

Otherwise I have no dyno sheets to backup claims with yet. There are two very large builds in progress that I'm going to be tuning that are both 10:1 on e85 so I'll be sure to report back with what they can do and possibly see what C16 does for reference.
I did not say I was making 80-100 less on E85 vs C16. I am making that on E85 vs E85. I was just throwing in my expierence with previous high compression motors. This motor has not seen any c16 yet.

As for tuning experience with HC. This is probably the 10th or so HC tune I have done. It is also however, the first time I have been able to compare it on my own car vs a lower compression.

BTW, I wouldn't say stock compression is best. From my test, 8.5:1 is the sweet spot :P . 8.2:1 is stock

Also, I am not tuning based on knock. I am tuning based on MBT and power. After a certain point it was not making more power, it was actually making less so I know where the MBT on this setup is. I am using AEMlog with a custom road dyno plug-in and all pulls are always done the same way on the same road so it is apples to apples and 100% accurate for me.

I have only gotten up to 27psi for now but I seriously doubt it just going to magically start making power with more boost around 30psi just because it's HC.
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Old 08-10-2011, 04:10 PM   #22
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Quote:
Originally Posted by soon2bblackongold View Post
if you would have used the same cams, it would be a more fair comparison...so, it's merely conjecture.

I acutally made a thread on low compression, I don't think subaru's are lacking out of corners, so why high compression anyway? Our tuners have a lot less experience tuning high compression as well...
I would guess it would actually be making even less HP with Cosworth cams. If you think I am making 80-100whp less by switching to a larger cam...

Why did I choose HC? For this exact purpose. To see if it would actually make more power like everyone "claims" but can't backup. Most people who do, did not try the same setup at a lower compression so they can say all they want but they have no idea if it would be faster at a different CR.
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Old 08-10-2011, 04:23 PM   #23
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I should have some real data here in a week or so. Same exact set up just switched to cp 9:1 pistons and differant tuner. Set up is a ej257 on a 20g e85 and bc272 cams. If I make the same power ill be happy but ilike the OP I would expect more, not less
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Old 08-10-2011, 04:27 PM   #24
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You also didn't try the same seetup on 'high' compression and then on 8.5:1. You went to a taller lift but narrower duration intake and exhaust cam. Don't you know top end power tends to like a long exhaust duration?


All I'm saying is that cam switch may be the cause of your loss in power. Bigger doesn't always mean better. I do have my cam card from my old cossie cams...just need the one for the 199-c. Still won't solve everything as lob profiles aren't dictated by duration, lift, evo, evc, ivo, ivc....lets see them ramprates

To truly dork and match cams, we'll want the flowbench data too...but now I'm just being a nerd.
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Old 08-10-2011, 05:06 PM   #25
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Quote:
Originally Posted by Crystal_Imprezav View Post
I have only gotten up to 27psi for now but I seriously doubt it just going to magically start making power with more boost around 30psi just because it's HC.
My car seemed to be down on power in the 25-28 psi area on the dyno also, we almost started to think something was wrong. When we got into the 30-33 psi range it really came to life, it gained about 20 whp per every pound of boost in that range. Im anxious to see how it performs in the upper 30's.

Im a little higher on compression then you at 9.8:1, and use Q16 instead of E85.

Id say up the boost a little and see if it starts to pick up power better before everyone starts filling your head with ideas. If it doesnt pick up power at higher boost then its time to dig into things and see whats wrong.
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