[88cr-rex]

According to most of the big name tuners, running much over 12:1 on a street engine has diminishing returns. You have to pull so much timing to run pump gas that you'd make the same power with lower compression.

Not quite. Static Compression is like 30% of the equation, if someone tells you just by static compression if you can run pump gas, they probably either don't know what they are talking about or don't feel like taking the time out to know all the parameters first.

Dynamic compression is the actual measure of pressure within the cylinder, only this can tell you if you are within reason to run pump gas.

Valve event timing has a heck of a lot more to do with pressure than static compression does.

 

[88cr-rex]

I prefer to stay with Honda engine builders and tuners. It amazing who you can talk to on Honda-Tech.

So do you think there is nothing to learn from a v8? Why exactly is their bigger air pump different than your smaller air pump? I would tend to believe people that build pro stock motors (the pinnacle of naturally aspirated) over some guys on ht.

Seriously, hit the All-Motor forum over there and start asking those guys what they think of high compression in anything other than a race engine. They'll all tell you to run less than 12:1 and get a quality port and polish...for a street engine.

So why again is the magical number 12:1. What happens at 12.5:1 that was so different? What if I build my a6 to 11.9:1? Am I safe to run on pump gas?

In the world of internet forums, there are those that do and those that listen to people that haven't done.

I heard the same thing about stock fuel lines in a foxbody cannot support more than 450rwhp. I saw them support 800rwhp on a twin t3/t4 352" windsor. I heard that the stock TFI distributor cannot run past 7000 or support 600fwhp. I saw a car make over 900 to the tires (On 93 octane!) with a 363 and a precision 88mm turbo and a FAST xfi. Just recently someone told me that ported stock mustang heads (E7TE) cannot flow enough to make power past 4600 rpm, regardless of what was done to them. I built a very budget 347 that made 300rwhp from 4700 to 5800 and 360rwtq off idle with only $2800.

The point is this: if it is within reason, and is mathematically sound, then why does someone's brother's cousin say it cannot be done?

 

[88cr-rex]

Those guys sucks.

I'm going to repeat something I've said before, why don't you go talk to some professional head porters if you want a greater understanding.

Hmm . . . okay.
Let's see, I work at a 3 man shop where all we build are mustangs (please flame). The guy who owns the place ports cylinder heads for Brad Brand (700" Outlaw 10.5 car which has gone a best of 6.79 @ 209), Tim Matherly (4.6 2v NMRA/FFW Real Street, been a best of 9.1x @ 141), and numerous local guys. His personal car went a 6.0 ( 1 / 8 ) at 114 on the motor. Plan is to run faster than 5.39, which is what the old car went.

So maybe I don't know anything because it isn't a honda. Or maybe its because my first porting at a honda head only went 227 I and 200 E.

So not only that but I have known Barry at Proline Race Engines for a couple of years now and he does measly heads for Tim Lynch's Outlaw 10.5 (best of 6.66 @ 215) and numerous other race cars given they build a ton of motors and Steve Petty tunes in-house.

Not once did I say it wouldn't work. Not once. You jumped way off the deep end there junior.

No, here is the issue you have had. You imply that since someone online said it couldn't be done, it can't. And here is the major problem, you never once said that these people knew your exact combo and therefore made a blanket statement on the internet. [email protected] was exactly right, a lot of inexperience people read/sift through honda-tech and if someone on there said to run 12:1 on pump gas with no tuning or research, they would be getting phone calls from kids saying they blew their motors up.

So do whatever you want, run 11.9:1. After last time, I am over arguing on here so I just try to mess with my ebay/junkyard junk and post the results.

edit:
Jesus fucking Christ guys, there are actually people outside of this forum who know what they're talking about. Believe it or not.

The compression vs VE thread left a lot of holes:
The rule of all rules is #1. This is the key to understanding compression.

1. If static is already near the detonation limit for the fuel being used, further increases in the static compression may hurt engine output and/or reliability.

With a typical n/a motor, the VE is often not much more than 87-89% (for a bolt-on motor) maybe slightly more for a well-built (heads/cam etc). These types can almost always gain from compression being that the motor cannot fill every last space of its cylinder given that the VE is under 100%. Compression allows an underachieving motor to use its incoming intake charge to the fullest extent. When you are above 100% VE is when reducing combustion chamber size is a bad idea. It is true that you reduce VE when you decrease combustion chamber size because total swept volume is less that it was before.

So, as stated before, without knowing #1, you have no perspective. You have rumors that increasing compression all the time is a good thing and its also a bad thing. The point is, you have to know what your motor is doing now to have any idea of how it will respond.

 

[88cr-rex]

None of you have a clue how much time I've spent talking to these guys

And transzex and I haven't? Further more, the people on here WITH ACTUAL REAL-WORLD EXPERIENCE have posted their ideas and you ignore them because the gods that be on honda-tech have said its improbable.

The porting of the cylinder head puts your engine at or above 100% VE before even adding the compression into the equation.

Here you go again with your blanket statements. I am convinced this is your main problem. You regurgitate other people's comments out of context and then apply them to any situation. Do you even know how to calculate VE?

Do you honestly think there are many n/a engines on the street that even approach 95%. Even on honda-tech? An n/a motor that sees 100% VE is one very well built motor. Have you built one?

 

[88cr-rex]

Crossroads says that you can run lower compression w/ a properly ported head and acheive the same numbers as an engine w/ higher compression and less VE?

I am not even sure what he is saying. His first post said that other people said it couldn't be done and now is on here saying he knows it cannot be done. He likes to make reading comprehension comments (which ironically I have been guilty of) given that he himself leaves entire statements from other posts out.

I don't remember saying anywhere that it wasn't safe. I said you'd make the same power with lower compression because you wouldn't have to pull as much timing.

The problem with this post and all of Crossroads posts is the fact we have no clue of the motor in question and what the current situation is on it, as far as in its static compression vs chamber size and its current VE. He makes statements such as these as if every motor on earth should increase combustion size and advance the timing regardless of its current static compression. The fact of the matter is, when a motor is operating under 100% VE it will always make more power when decreasing the combustion size to increase VE and moreover increase thermal efficiency. It is now using more of the gasoline it already had coming into the chamber more effectively. A smaller combustion chamber vs more timing will 99% be more effective given a situation wherein the motor can take more compression given the fuel is not at its detonation limit. Milling a cylinder head is a good thing. Unshrouding the valve is worth its weight in gold.

Everything is relative and this is what crossroads conviently leaves out every single time.

With that said, wouldn't it make the most sense to have a properly ported head w/ the max. VE possible as well as high compression? Then wouldn't you then get the max benifit of the compression and VE?

Yes. That in itself is another argument (quality vs. quantity) but typically a head is ported to clean up problem areas (guide, shortside, throat) and if needed enlarged the port. They are two different arguments, we started with if over 12:1 can be supported by pump gas and now its turned into a VE flame war. Then a static compression is choosen for the ideal chamber size/camshaft/detonation limit of fuel being used.

Regardless of what anyone has posted: 12:1 on a d-series honda motor can be run on pump gas and probably should be for certain camshafts provided you tune the car. It really should have ended halfway down the first page.