There is so much conflicting information about these things, hopefully we can get some real facts established in this thread that can lead to some clarity among the community about what what's needed and what's not.

A LOT of people are under the belief that you must install a 3mm HG in high boost applications to avoid grenading the motor. There are more than a few examples of setups being done on the stock headgasket/bottom end that disprove this theory. All of those setups have two things in common - GREAT tuning and efficient setups (well designed manifold, large turbo, more than enough fuel, conservative timing, etc). I think the reason why the HG trend caught on was because people weren't getting the best tuning to support longevity + efficiency with their setups and all we heard were the horror stories of failed motors. The tuning options for the S2000 have improved greatly in the last two years and there should be more knowledge spread of what the stock motor is capable of.

This is not a thread to disprove the need for a HG. It is a proven "upgrade" to support more horespower, but it is also proven that you achieve the same power (to a degree) with the stock compression using less boost. A HG just give you more room for error in tuning by lowering the ceiling on detonation. Fuel octane, manifold design, turbo sizing, injector sizing are all other very important aspects that should be considered when choosing to run an aftermarket HG for your desired power goal.

At this point in time, I'm convinced that whatever goal I end up choosing for my future turbo goals for street duty can be achieved on the stock, untouched longblock. Past that, I'll skip the headgasket and build the bottom end for lower compression. Post up your thoughts, and lets argue this thing out. My hope is this can be a productive thread that gets added to a new Turbo FAQ that is in desperate need of updating.

- The Spectacle

 

Most of the people running high hp on a completely stock motor are running race fuel. Its really not a question of can the stock motor handle the hp, but its the limits of the pressures created in the combustion chamber...Once you start going over say 10-12 psi on a stock motor with the stock headgasket, the pump gas is condensed and heated enough to spontaneously combust causing detonation.

You can only tune the car so well and retard the timing so much until you reach the limit of the fuel you are burning where it will ignite even without spark well before TDC trying to force the piston back down before it reaches TDC on the compression stroke and this is when detonation begins.

So to avoid this problem people are running race fuel which has burns cooler and depending on the octane, has a higher tolerance to heat and pressure to avoid detonation.

 

Some people have made 500+ on a stock motor but I have yet to hear of one put any significant mileage on it with that much power.

The reason we use headgaskets is to increase the overall life of the motor. Anyone can make power for a short burst, its a different story to make it last.

 

Most people who are running high hp on a stock motor are also building a motor.

 

Huh? You're on the right track but not quite there yet.

10-12 psi on what turbo? Turbo size makes ALL the difference here.

"Condensed"? What does that mean lol

This applies to all motors, no matter what headgasket or compression you're running. Pretty much irrelevant to this thread.

 

Wow I can't believe I am about to say this, but for once spectacle we ARE talking about PSI instead of CFM.

UNLIKE YOUR POST ABOVE, turbo size has squat to do with what we are talking about here. Someone reads the forums well but doesn't apply the physics idea's properly.

You seem like a bright guy so I will not question your understanding of the difference between flow and cylinder pressure, but just know that your commented question is not correct. WE DON'T CARE what turbo a person is running, we are talking in terms of cylinder pressure ratio's getting to high.

If you need further explanation I will go into it.

J. R.

 

[QUOTE=flexer,Mar 2 2009, 01:11 PM] Wow I can't believe I am about to say this, but for once spectacle we ARE talking about PSI instead of CFM.

UNLIKE YOUR POST ABOVE, turbo size has squat to do with what we are talking about here.

 

I use a stock HG with a GT3076R at 8-9psi and made 371whp and 249 ft/lb. It uses a log manifold and has a very conservative tune. I dont plan on ever opening the engine to put a 3mm HG in it. I am going back to run 16psi soon, but will be using race gas to achieve numbers over 10psi. I am not going to take the stock engine with pump gas past 10psi. Im sure it can be done, but 11.0:1 CR has its limits, its just physics. There comes a point when you cant squeeze any more pressure into the cylinder on pump without it detonating.

10psi on a GT35R and 10psi on a T28 are different yes, but i dont think the engine is gonna care. The GT35R isnt gonna heat the air as much, but will flow a ton more cfms. I still dont think you could push a T28 past 10 psi on a stock engine stock CR because the compressor on a T28 would get SO inefficent that its going to superheat the air. so 10psi is the SAFE limit for stock block no matter what turbo you run....on pump gas. Race gas is a different story!!

 

That's the type of information I'm trying to prove and/or disprove with this thread. Mainly disprove. It just makes no sense.

 

10psi is just resistance to flow i understand that, but there is just a limit to 11:0:1 CR on pump gas. I dont understand why you would want to risk engine failure trying to run more than 10-12psi on pump gas. Run good gas if you want more power on a stock CR engine. 10psi on an efficient setup will be near or over 400whp, thats asking a lot of a stock engine stock CR with pump.

Im sure you could run more boost on stock CR 15psi ish, and it may last and it may not. Depends on how well its tuned and how efficent your setup is.