In for the long haul Ultimate NA build thread.

[fika84]

Originally Posted by churchx

It's easy to get such compression. Just swap in cummins diesel

If they made a boxer diesel, I would be allllll over it.

[coryandy]

Originally Posted by fika84

If they made a boxer diesel, I would be allllll over it.

They do make a boxer diesel. Although getting one from overseas is probably not easy.

Sent from my P008 using Tapatalk

[Irace86.2.0]

Originally Posted by cyde01

Even if 14:1 or 15:1 comp were possible, you gotta ask yourself how much more hp you're even gonna make over an already sky high 13:1 or 13.5:1 ratio. You're risking a lot for minimal gains imo.

Why minimal gains? The motor is compressing more air and fuel.

Granted the Civic was like bore n stroked n sleeved to 2.5L n had a motec system n valve work n e85 n everything, but doing 11.3 @124 and 330whp is good stuff. Could it be done with less money with FI? Yes but if someone wants to pony up the cash then it is their build, and I wouldn’t mind seeing it.

[cyde01]

Originally Posted by Irace86.2.0

Why minimal gains? The motor is compressing more air and fuel.

Granted the Civic was like bore n stroked n sleeved to 2.5L n had a motec system n valve work n e85 n everything, but doing 11.3 @124 and 330whp is good stuff. Could it be done with less money with FI? Yes but if someone wants to pony up the cash then it is their build, and I wouldn’t mind seeing it.

I'm saying minimal compared to an already sky high comp like celek's 13:1 ratio, and minimal compared to the extreme risk you're subjecting your engine to. That civic makes a lot of hp, but dare i say it would still make a lot of hp with the comp lowered to 13:1. Most of the gains it's making are coming from elsewhere.

[Irace86.2.0]

Originally Posted by cyde01

I'm saying minimal compared to an already sky high comp like celek's 13:1 ratio, and minimal compared to the extreme risk you're subjecting your engine to. That civic makes a lot of hp, but dare i say it would still make a lot of hp with the comp lowered to 13:1. Most of the gains it's making are coming from elsewhere.

He over-bored the k24 from an Acura TSX to 2.5L. Unless he went with super light pistons and rods to get the redline significantly higher, it was likely low compared to the k20, which is why horsepower was about the same between the k20 and k24 (just the torque significantly improved). I feel like most of the gains are coming from the compression and e85 then flow of the head/cams, larger throttle body and exhaust, which is why he needs to rev it out so much to extract that peak hp. He probably did raise the redline because vtech doesn't kit in until 6800rpms, but I would still argue it was in the compression ratio.

[cyde01]

Originally Posted by Irace86.2.0

He over-bored the k24 from an Acura TSX to 2.5L. Unless he went with super light pistons and rods to get the redline significantly higher, it was likely low compared to the k20, which is why horsepower was about the same between the k20 and k24 (just the torque significantly improved). I feel like most of the gains are coming from the compression and e85 then flow of the head/cams, larger throttle body and exhaust, which is why he needs to rev it out so much to extract that peak hp. He probably did raise the redline because vtech doesn't kit in until 6800rpms, but I would still argue it was in the compression ratio.

i still doubt that lowering that specific build from 14:1 to 13:1 would decrease the power by much. but you know what it seems like neither of us are familiar enough with this k24 build anyway and even if we were it's an apples to oranges comparison.

but back to celek's build. celek is already running an extremely high 13:1 ratio. 14:1 is not that high of a bump compared to 13:1, even though detonation risk is significantly higher. on top of that, you got the law of diminishing returns due to heat and friction. putting the civic aside, if celek raised comp from 13:1 to 14:1, do you really think that he would make anything more than minimal gains? for that much more detonation risk?

[Irace86.2.0]

Originally Posted by cyde01

i still doubt that lowering that specific build from 14:1 to 13:1 would decrease the power by much. but you know what it seems like neither of us are familiar enough with this k24 build anyway and even if we were it's an apples to oranges comparison.

but back to celek's build. celek is already running an extremely high 13:1 ratio. 14:1 is not that high of a bump compared to 13:1, even though detonation risk is significantly higher. on top of that, you got the law of diminishing returns due to heat and friction. putting the civic aside, if celek raised comp from 13:1 to 14:1, do you really think that he would make anything more than minimal gains? for that much more detonation risk?

I don’t know what the detonation risk is on E85 to comment.

[Voltwings]

So first and foremost i do not have have an 86 twin, i have just been lurking this forum and trying to learn what i can about this platform as i consider an 86 for my next HPDE car.

Without getting too off topic, i do have years of tracking and recreational tuning experience and this seems like a fun topic to become involved in.

With regards to compression, we're going to do some ricer math here. All else equal, 1 point of compression is going to give you about a 4% bump in power. Assuming this build will make 250 whp peak at 13:1, you could expect about 260 whp peak going 14:1. Now, keep in mind, that is a percentage gain, which means given the very linear power band of this engine i would expect curve gains to be minimal in the majority of the powerband? Yes, 3, 5, 7... over the whole curve is nothing to scoff at, but that "all else equal" is a very big caveat, and increasing compression brings in some other draw backs as others have mentioned.

Now, onto the E85 issue. I have DI tuning experience and on my personal vehicle went down to as little as 2 gallons of E85 in a 16 gallon tank and still had impressive knock resistance. E85 in direct injection applications has an effective octane of about 160, which is why you see a lot of times DI cars are tuned on E85 blends. You do not need large amounts of E85, really anything over 25% (common referred to as E30 or E33) is unnecessary, so you may as well use as little as needed and keep the head room.

At any rate, that is my .02 to this discussion, i'll go back to lurking.

[churchx]

Octane number of 160 for E85? Wasn't it rather around 110?

[nikitopo]

Originally Posted by fika84

If they made a boxer diesel, I would be allllll over it.

Originally Posted by coryandy

They do make a boxer diesel. Although getting one from overseas is probably not easy.

Subaru is not developing the diesel engine anymore.

[200hp/tonne]

there are heat of vaporization benefits to E85, which would be more significant in a DI engine compared to PI, but i doubt they are as drastic as an effective octane number of 160

[Voltwings]

A computational model is used in
this paper to determine the knock resistance and effective octane number of these alcohol
fuels when they are directly injected. The model indicates that the effective octane
numbers are around 160 for ethanol and 180 for methanol.

Taken from:

https://energy.mit.edu/wp-content/up...-08-001-RP.pdf


I started tuning in ... 2011, so it has been several years since i have read this article.

[Code Monkey]

Originally Posted by Voltwings

So first and foremost....

Hello stranger.

[Voltwings]

Originally Posted by Code Monkey

Hello stranger.

Oh shit haha, sending you a PM.

/threadjack