^^ you may some valid points for sure.

You would be correct in also saying someone could bend rods at one bar of boost:
with crappy gas and way too much timing and lean condition.

Pump gas, high boost, lean fuel mixture and advanced timing certainly is a recipe for disaster and on the other hand I have run my car wide open in 6th gear with the foot flat to the floor for 15-25 seconds many times with no (apparent) engine damage at
1.4 bar +.

I credit that to a good fueling system (Protomotive), good programming
(appropriate combo of air/fuel/timing/boost, etc) Protomotive, and good fuel (MS109 or Sunoco GT260+). I do not know if my VERY GOOD intercoolers also help this or not.

 

All of the above sure helps...But lets say that in my setup,k24/18g with 60lb injectors,I am running 1,35 with 100octane fuel and A/F ratios alittle rich in order to avoid fuel starvation...How can i tell if i run in danger?

 

IMO, I don't think there is any way to know. All things have their own fatigue failure point. Your car may run fine on 1.5bar on pump, mine may blow up at 1.3 on race fuel...never know.
Justin is right. 1.4bar on K16's is waaaay different than 18G's at 1.4bar, forget about fuel for a minute. Same boost pressure, but MORE fuel (because you have put more air in (at the same pressure (boost). More fuel, more "boom", more cylinder pressure, more pressure on rods and rod bearings. Now factor in fuel and the potential for detonation with pump gas, and your rods and/or rod bearings are outa here...

 

There is no way of telling when you are in danger. There is no rule of thump as how much boost you can run on pump gas or certain fuel. As Justin had stated it is a big different on K16 at 1.2 bar and Gt35 at 1.2 bar.

Its all up to the tuner as he tunes that setup and know how much boost and timing he can puts in.

This is when a good tuner counts. He knows wheres the border line to stop on boost and timing for that setup on certain gas, which will make the most power and still safe.

You should ask your tuner for that max boost you can run on pump gas!

 

Finally someone on here who understands the difference.So many people on here do not understand this but should.+rep

 

First of all, much respect to all, but I think I have to disagree. Unless I'm missing something, boost pressure is DIRECTLY related to cylinder pressure, as in "pounds per square inch". When you put 15 or 20 PSI in a cylinder, you are increasing cylinder pressure. Add to it the fuel that is added with the pressurized air and the incoming spark, and you have created pressure, that I'm sure Porsche NEVER intended for that cylinder to have.

Obviously, as Justin said, the "incidentals" have a huge factor in how much power an engine makes. Not trying to start a p*issing contest, just trying to understand the logic.
M

 

You could also bend the rods on a perfect running one with just more power than the rod can handle.Put a set of tires on a car that dead hook and launch it hard and you have a good chance of bending rods if they aren't up to the task.It can be done without detonation.lol

 

Absolutely without a doubt. I eluded to that ealier in that every single part has it's own failure rate. You could bend 1 rod, could bend 6, never know...

 

Boost pressure is a measurement of restriction in the intake plenum that the engine cant process. Boost pressure has no direct relation to cylinder pressure. Cylinder pressure are more related to how much timing.......

 

I know Justin knows boost like Papa John knows Pizza...It's what he does for a living.

1bar boost on a turbo making 500 hp will have higher intake temps generally then compard to a turbo running .7bar boost making 500hp. That's why a lot of guys want to get the best supporting mods so the turbo doesn't have to work so hard to make that 500hp.

 

Am I getting this right??? Why would there be a reason a bigger turbo at same "bar" would make more power? Because of cooler air charge since the turbo it at better efficiency? I'd imagine at a given BAR the air volume is the same with both.

 

Bigger turbo compresses more air, with more air, more fuel, bigger boom. Pressure is not the same as volume.

 

The air VOLUME is different. The efficiency points have changed. Where you make the power has changed.

The more you compress air, the hotter and less dense it becomes. Intercoolers can only do so much, but if you can get a higher concentration of oxygen in PRE intercooler, then imagine what you are getting POST intercooler.

So everyone understands... the boost pressure can remain the same, let's say 1.2 bar, but the volume of air(and molecules of oxygen within a given unit of air) has increased with a more efficient setup, due partially to the fact that the air is not being superheated(there are other reasons also, but this is the easiest to compare ). This is also why I mentioned your incidental items must be capable of doing their part as well.

DEpending on where your engine is meeting its efficiency with the turbos(and pressurized air), the amount of flow through the engine changes. Therefore the amount of backpressure at the intake manifold changes. This is why you have a solenoid to regulate boost pressures. example, I removed my boost regulation solenoid from my Turbo, and hit .5 bar all the way to 6k, then it dropped to .4 bar. With the stock solenoid in place, it is constantly varying the duty to maintain the .6 -.7 number. Change your cams, and the duty cycle changes... change the turbos and the duty cycle changes.... change the head(porting, squish, etc) basically, anything affecting volumetric efficiency, and the duty cycle changes(just to be clear, turbos do not directly affect VE, but do affect the duty cycle ).

Justin