Internal engine stresses
Last edited by Wesleydaisy97; Jun 21, 2016 at 11:09 PM.
Not to be a dick, but if you use punctuation, break up that huge blob into a couple paragraphs, maybe some smart people will bother to read it and have some good info for you.
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There are many contributing factors, cam (dynamic CR), compression ratio (static), fuel quality, ignition, and even intake and exhaust airflow parameters can influence peak cylinder pressure. And dont forget water/methanol injection and intake charge cooling solutions.
The biggest contributor is the tune, the higher the boost the narrower the tuning window is for safe operation. Gasoline forces a tune closer to the edge as it make the best power just before meltdown, gasoline makes significantly less power at "safer" tune levels than alky. Conversely alky will make good power in a significantly overfueled "safe" tune.
Water injection helps control peak pressures by cooling and slowing down the burn.
Another area is spark control, it is too easy to dial up the spark advance for more power, which is fine and is a natural tuning tool. However the quality of the spark timing control becomes paramount when you get close to the edge. ANY timing scatter can cause significant damage to a random cylinder, while the overall tune might be safe. That single event can cause that one firing cylinder to fold up the rod or collapse a piston.
There are many contributing factors, cam (dynamic CR), compression ratio (static), fuel quality, ignition, and even intake and exhaust airflow parameters can influence peak cylinder pressure. And dont forget water/methanol injection and intake charge cooling solutions.
The biggest contributor is the tune, the higher the boost the narrower the tuning window is for safe operation. Gasoline forces a tune closer to the edge as it make the best power just before meltdown, gasoline makes significantly less power at "safer" tune levels than alky. Conversely alky will make good power in a significantly overfueled "safe" tune.
Water injection helps control peak pressures by cooling and slowing down the burn.
Another area is spark control, it is too easy to dial up the spark advance for more power, which is fine and is a natural tuning tool. However the quality of the spark timing control becomes paramount when you get close to the edge. ANY timing scatter can cause significant damage to a random cylinder, while the overall tune might be safe. That single event can cause that one firing cylinder to fold up the rod or collapse a piston.
You need proper tuning tools, like HP Tuner or an aftermarket ECU that you can get inside with a laptop and twiddle the settings.
In addition to the tools your hardware needs to be complementary to the setup. You need adequate fuel supply volume and pressure, ideally you need a return type fuel system and a boost referenced fuel pressure regulator (so your fuel pressure maintains a 3 bar difference above the manifold pressure). In other words with a non return system you have a regulated 43.5psi (3bar) and then have 20psi boost, you injectors now see only a 23.5psi difference and have to open twice as long to spray the same amount of fuel. For 20# of boost you need 63.5# fuel pressure to maintain the 43.5# difference.
Injector sizing is important as well to be able to provide enough fuel for max power without being oversized and causing idle problems, a manifold referenced fuel pressure regulator helps here too, by reducing the fuel pressure at idle and increasing it under boost.
A return system also helps by cooling the fuel rail and purging any air bubbles that may be present. Air bubbles in the fuel are really bad on a single line system as there is no way for them to escape other than through the injector (which displaces fuel and causes random lean misfires)(in a boosted motor tuned on the edge this means random intermittent detonation).
Fuel delivery is problematic for a car that is driven with sustained high G forces or more so with high G forces in all directions, you can somewhat combat this by keeping the fuel tank as full as possible, sometimes that is not practical especially on a street driven car. For the popular cars there are manufactured solutions replacement fuel tanks (cells) with trap doors, foam, and moving pickups, multiple pumps, and more expensive trickery. The simplest solution here is a swirl pot where the intank pump supplies fuel to a narrow and tall 1 to 2 quart sealed pot. That pot is vented (fuel is returned) back to the tank, this purges any air bubbles and provides a constant reliable supply to the EFI pump which is mounted inside the pot or is gravity fed from the bottom of the pot. This way there is a constant air bubble free, 1 to 2 quart supply of fuel to the EFI pump, and because of the tall & narrow orientation will not be affected by varying G forces.
Last edited by RixTrix; Jun 26, 2016 at 04:43 PM.
You need proper tuning tools, like HP Tuner or an aftermarket ECU that you can get inside with a laptop and twiddle the settings.
In addition to the tools your hardware needs to be complementary to the setup. You need adequate fuel supply volume and pressure, ideally you need a return type fuel system and a boost referenced fuel pressure regulator (so your fuel pressure maintains a 3 bar difference above the manifold pressure). In other words with a non return system you have a regulated 43.5psi (3bar) and then have 20psi boost, you injectors now see only a 23.5psi difference and have to open twice as long to spray the same amount of fuel. For 20# of boost you need 63.5# fuel pressure to maintain the 43.5# difference.
Injector sizing is important as well to be able to provide enough fuel for max power without being oversized and causing idle problems, a manifold referenced fuel pressure regulator helps here too, by reducing the fuel pressure at idle and increasing it under boost.
A return system also helps by cooling the fuel rail and purging any air bubbles that may be present. Air bubbles in the fuel are really bad on a single line system as there is no way for them to escape other than through the injector (which displaces fuel and causes random lean misfires)(in a boosted motor tuned on the edge this means random intermittent detonation).
*think, not thank.
If you want to slowly ramp in the boost, get a Centrifugal blower. They behave that way by design. Using multi-stage controllers and stand-alones that can do boost by speed/RPM/gear is only complicating it.
If you want to slowly ramp in the boost, get a Centrifugal blower. They behave that way by design. Using multi-stage controllers and stand-alones that can do boost by speed/RPM/gear is only complicating it.[/QUOT
It would get it done but i like being precise and boost by rpm gives me the chance to tune however i want the boost ramp to be








