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[Joseph Davis]

I keep having people say to me that they want higher compression than a 7.5:1 CR Vitara build. 

Stock CR, the common 9:1 CR forged motor, and 7.5:1 Vitara engine all make the same power for a given camshaft, in my experience.  With stock Z6/Y8 cam, 300whp at 17-18 psi.  More power per psi with a cam, but all comparable across CRs.

Why ask for trouble?  It blows my mind.

[350WHPorBUST]

[jabberwock]

People worry about quench, as if we didn't have engines with aluminum heads and round chambers.  Y engines excluded.  Low rpm drivability is achievable by tweaking timing.  If i can do it anyone can

[Joseph Davis]

What quench?  The only 90s Honda motor that had that was the 1G GX, and most people have never seen one of those driving down the road.

[PhilStubbs]

99.45% of honda people dont understand quench. most of them want high compression cause they think the car will be super slow out of boost. they have obviously never driven a vitara/stock rod length car. i DD'd one with the super low comp and couldnt feel the difference between that and stock z6 in vac.

[snm95ls]

What quench?  The only 90s Honda motor that had that was the 1G GX, and most people have never seen one of those driving down the road.

Y8 and B18C1 need not apply?

Guess I fall into that 99.45%.

[Joseph Davis]

Y8 and B18C1 need not apply?

Having quench pads, and having quench, are two different things.

[snm95ls]

Fair enough.

[PhilStubbs]

I didn't give that statistic trying to claim I fully understand it. I think I have an idea, but could be way off

[Joseph Davis]

It occurs to me that I'm expect others to read my mind.

Vizard did a lot of work woth quench, much of it published as layman's tech in Hotrod when he was employed there.  Much of that is online, and solid fucking tech.

The question is a matter of clearance - quench pads require a critical clearance to work.  Ths is not present in the distributor Hondas, and I am mechanically out of touch with the newer stuff for the most part.  If you ever get the chance to see a rod knocker WRX motor torn down, do so.  Those motors have quench, and the sound you hear is the piston hittong the head long before the bearing otself is sloppy enough to make a considerable noise.

[PhilStubbs]

That vitara statement is inline with what I think quench is all about. Maybe I'm not as think as I dumb.

[crxvtec91]

Poor mans 500hp and a ton of miles, what more do people want from $100 pistons............

[snm95ls]

It occurs to me that I'm expect others to read my mind.

Vizard did a lot of work woth quench, much of it published as layman's tech in Hotrod when he was employed there.  Much of that is online, and solid fucking tech.

The question is a matter of clearance - quench pads require a critical clearance to work.  Ths is not present in the distributor Hondas, and I am mechanically out of touch with the newer stuff for the most part.  If you ever get the chance to see a rod knocker WRX motor torn down, do so.  Those motors have quench, and the sound you hear is the piston hittong the head long before the bearing otself is sloppy enough to make a considerable noise.

Pretty sure I have read Vizard's work several times.  Maybe memory is failing me, but I think the critical distance is somewhere between 0.030" to 0.040". 

Unless the published specs for compression height, deck height, and headgasket thickness are quite a nit off, I always thought that stock and most off the shelf pistons for at least C1 applications fell within that realm.  Admittedly, I haven't run the numbers recently, and I may be thinking of LSV/B20V applications with R comp height pistons and the shorter non-VTAK deck height.

Speaking of Subaru motors...  Thoughts on making an EJ255 last?  Plan for now is to leave it stock.

Lol!

EDIT:  Just ran the numbers.  Yep, even the stock C1 and the LSV/B20V using R comp height pistons fall out of the effective deck clearance range.  Both are 0.050"+

[Joseph Davis]

Speaking of Subaru motors...  Thoughts on making an EJ255 last?  Plan for now is to leave it stock.

No.  I like driving Subarus, not a big fan of the drivetrain.  Fragile.  STI and bolt ons with the boost turned up on the stock turbo is my level of interest, well, except for paying STI prices.

[snm95ls]

Speaking of Subaru motors...  Thoughts on making an EJ255 last?  Plan for now is to leave it stock.

No.  I like driving Subarus, not a big fan of the drivetrain.  Fragile.  STI and bolt ons with the boost turned up on the stock turbo is my level of interest, well, except for paying STI prices.

Eh, it's a comfy DD that is just quick enough to be fun.  I'll probably leave it alone for quite a while minus a few things to keep it from breaking.  Catless UP, and maybe an AOS.  Supposedly the OEM 05/06 LGT tunes are more conservative than the later ones/

[Joseph Davis]

Get the EGT probe out of there, they just break and kill turbos.  Substitute a 2.2k resistor.

[snm95ls]

Get the EGT probe out of there, they just break and kill turbos.  Substitute a 2.2k resistor.

Yeah, that will be part of the catless UP swap.

[ratcityrex]

Idk why people think that low comp motors are dogs out of boost either. My ls made more power @ 8.0:1 than a stock 9.2:1 ls does. Stock obd0 exhaust mani and all stock obd0 cams, stock obd0 tuning, only difference was no cat and it made 125whp. So go figure.

[Joseph Davis]

Get the EGT probe out of there, they just break and kill turbos.  Substitute a 2.2k resistor.

Yeah, that will be part of the catless UP swap.

It was a FYI if that shit isn't hopping on the car immediately.

[92CXyD]

With vitara in my builds I had 0.020" decked of the block and with y8 heads I run 8.0:1.

Which seems to work perfect for me w/ stock cams and some mild porting.

JD remember the setup w/ only s/c on it up in Seattle that was exactly what I had.

Remember it was very responsive.

[Joseph Davis]

Yeah, it didn't suck with the blower off.  Off boost it was the fastest stock cam SOHC I've ever been in, aside from mine.

[92CXyD]

Yeah, it didn't suck with the blower off.  Off boost it was the fastest stock cam SOHC I've ever been in, aside from mine.

Wow, that surprised me, thanks JD.

You should ride in it now, it is even faster. 

[jabberwock]

This thread got homoerotic

[PhilStubbs]

JD is Russ' cougar, let it be. Everyone news to bang a cougar at least once in their life.

[HiProfile]

I think the problem is few people alter vac timing on a low-CR turbo Honda, or they do it incorrectly.

TDC is not where peak cylinder pressure occurs, its usually between 10-20* ATDC. From what I've seen & experienced, the new timing is the square root of the compression change multiplied against that "overall" timing value. I use the word overall to describe the degree value between spark and peak cylinder pressure, I'm not sure if there is a proper name for it. That means you take the timing value, add ~15*, multiply it by the change in compression's square root, then subtract ~15* to get your new btdc ignition timing value.

If someone with a 10.5:1 forged d16 w/turbo was to reduce vac timing thinking it was actually 12:1, the motor would feel just as sluggish off-boost as a similar vitara d16.

[92CXyD]

JD is Russ' cougar, let it be. Everyone news to bang a cougar at least once in their life.

LOL I'm older than JD... 

[PhilStubbs]

Stupid iPhone auto correct

"Russ found a cub... Let it be"

Lol

[Joseph Davis]

I hate everyone in this thread.

[flat_black]

My Rb25 cluster fuck is 7.6:1 and it doesnt feel any different than the 9:1 it is stock.. however this motor does have quench pads