Increasing compression

[Cincy]

Just wanted to post some info on this topic since its starting to arise more often



- More power off psi

- More power with less psi and/or timing (have to reduce one of them if octane dependent aka pump)

-- ^ lower temps out of the turbo and great efficiecy from the turbo

- More tq and sooner

- Better throttle response

- longer powerband



On the dyno the different compressions made very little changes in power what it did change was where it made power and how broad of a power curve, low compresion made a narrow high rpm curve while the high compresion made a longer power curve and much closer to the peak torque curve.



- Burns at a lower temp since its more efficent

- ^ above also results in better gas mileage

- - ^ i can atest to that. 33mpg on the move to FL with GF and another 250+lbs in the hatch and with another 228cc motor

- spools the turbo faster



Higher compresion creates higher combustion preasures and temps in exchange creates higher velocity of exhaust gas traveling through the port wich would spool the turbo faster. We had the very same B16 honda turbo setup with a .63 ar exhaust housing with stock compresion at 10:1 and it spooled 300 rpm sooner in the logs then the same motor does now with 8.8:1 pistons.



- Only downside is less room for error on a tune and octane dependent. With more octane or w/m, more psi and timing can easily be added, same as a lower compression motor but with a broader powerband.



Not sure why anyone would want to run less than 9.5:1 on a street motor with a turbo that actually has lag. Of course, this is my opinion

[ImTheDevil]

I wouldn't be surprised if many of those impressions (ie, higher CR automatically means a lower peak psi) stem from opinions and results formed several years back, before higher precision engine management became available. With the cruder systems back then, you really had to err on the side of caution when it came to boost vs compression ratio. Now, with the advent of greater precision in engine management, and even moreso with the direct-injection engines now emerging, high CR and high boost are not mutually exclusive. I have ridden in a Civic with a fully (and I mean FULLY) built motor - custom cams, spec'ced internals, tubular manifold, full top-end build, GT35R turbo - running 30psi on an 11.3:1 CR. That car spent dozens of hours on the dyno dialing in its delivery and control, and the time paid off. He's more or less streetable and capable of a nine-second pass at the track. Lag time is still significant of course (it takes quite a bit more than 1.6L to spool a turbo that big) but once the boost comes on, it's pure lunacy. The car has been running with no issues for over three years now (no issues since the final bugs were worked out - it was defnitely not a first-time success). Control it right, and a lot of boost can happily coexist with a high CR.

[Cincy]

Tuning makes for a huge help. The most limiting factor is fueling. You can only prevent detenation so much on 91/93oct. The higher the compression, the sooner it will knock. If you look at drag cars making HUGE power and running ALKY as fuel, they all run super high compression and psi higher than most deisels. The new mkv 2.0T's all come with FSI which helps them since they all now run above 10:1 c/r stock.

I personally just love the great off boost i have with a 2008cc motor and 10.16:1 compression. I can go from 60-80mph in just a blip of the gas and no psi. If anyone takes the time to compare Evos (8.8:1 2L) spool ups compared to a 1.8t using the same turbo, they will notice that we spool up a few hundred rpms faster with smaller motors due to both compression and timing.

[AudiTurbo]

What do I have to do to build my car to a 2.0L? I know I should know more about this, but I would want more information before I did it!
Thanks guys!

[Cincy]

For your engine, you need a ABA crank from an old 2.slow, stock drop in rods )IE, scat, etc) and 83mm stroker pistons that have the pin moved up for the added stroke. This will give you 2008cc motor

[AudiTurbo]

How much would I make with a k04 and other mods with that motor setup?

[l88m22vette]

qedpower and inaengineering both sell stroker kits, and you can also use an AEG crank. There has been debate about using an FSI crank, and really its wasted money, the $300 crank (ABA, AEG) has not broken. An FSI is $800, and for that difference you can get rods and bearings ;) With a K04 you could probably expect 260+whp (vs 220 with the 9:1 comp 1.8t). Still, like cincy's k03, its all spike; neither K03/4 can flow enough air for nice, sustained powerbands

[Cincy]

totally not worth the cost for a ko4. No real point in doing so unless you want to make 400whp+

[Cincy]

qedpower and inaengineering both sell stroker kits, and you can also use an AEG crank. There has been debate about using an FSI crank, and really its wasted money, the $300 crank (ABA, AEG) has not broken. An FSI is $800, and for that difference you can get rods and bearings ;)

He has an 058 block, so he can only use the ABA crank

[AudiTurbo]

So what turbo should be used for this setup? I'm keeping my car for a while and about to buy a new motor, so I just wanted the info! Thanks guys!

[Cincy]

depends on what you want to make powerwise. I have a nice thread in the TT section sticky that you may want to take a look at.

[AudiTurbo]

OK what setup do you have cincy?

[Cincy]

im currently on a stock turbo and will be going with a much larger BW turbo here in a few months

[ImTheDevil]

From the sounds of it, a GT28RS dbb turbo would probably be ideal - nasty spoolup and some good top-end head room. A T3s60 could make some noise too...

[AudiTurbo]

Perfect thread in the TT section. Everything I need to know

[l88m22vette]

With higher comp a 2871R would be better than an RS, great spool and top-end

[ImTheDevil]

Yeah that'd work very well too.

[Irish*TT*]

For your engine, you need a ABA crank from an old 2.slow, stock drop in rods )IE, scat, etc) and 83mm stroker pistons that have the pin moved up for the added stroke. This will give you 2008cc motor

so u dont need to bore or the head/block ?
iv found kits for $1600 but im betting u can do it cheaper then that ?

if u dont need to bore , id much rather do this then a big turbo , for now

[Cincy]

you cant fit 83mm pistons in a 81mm cyl w/o a bore. You can get 10:1 stock 81mm pistons if you dont want to bore the block, just rebuild

[KrissrocK]

i would really love to take my car to 2.0 as well.. but i'm hesitant to take the CR too high since the temperatures go up too, and we don't have iron blocks right?

So i'm thinking of going form 9 to 9.5 ... eeef phuk it, might as well go 10.

my question is how much of the other stuff is needed when stoking and assuming going BT later. Like these stroker kits don't come with caps and journal bearings n the like....but should one have those upgraded/replaced when doing a stroker?

[Cincy]

We have cast iron blocks. When stroking a motor, you are going to replace everything that wears. Both the main and rod bearings get replaced, along with all the seals. The pistons come with new rings so you basically need a top end replacement kit along with a NA 20v head gasket if you go with 83mm pistons. If you go with a 82.5mm piston, you can keep the stock headgasket which about $40 where the NA 20v is $95.

9-9.5:1 is still plenty of compression if you wish to keep it more conservative.

[KrissrocK]

so when replacing the bearings, must you upgrade, or stock are ok, just need to be new?

[Cincy]

Stock is fine. Thats what i have. You can get coated bearings which help with starting but not needed at x2 the cost. Also, im using all stock bolts, if you plan on going nuts with your build, you may want to move to ARP head bolts or studs for the head and mains. Since my car will be mainly a pump gas car in the 425-450whp range, i didnt see a need. I may move the ARP head studs if/when i do a AEB head and cams when the need for more power arises.

[KrissrocK]

so what do you think the power/tq difference may be if one were to just increase the compression(1.8), versus increased compression and displacement (2.0) as many of us are talking about.

[Cincy]

It all depends on which model we are talking about (.5 vs 1 gain in compression) and on what setup. Best way to describe it would be the general rule is 2% gain/full point NA. Wont really be able to calculate that with a turbo, but about 5% at the same psi level would be a decent guess for a 225. But the main reason to do it would be for the list in post #1