Blew my motor!!!

[Jaden]

Originally Posted by guybo

I have been watching these threads where FI motors get blown. I see a common thread among them- more than 8 psi of boost. From my observations from around this forum, anything over 8 psi is a ticking time bomb. It's not a definite and there have been a couple I have read about running less boost, but almost all of them run more.

No stats, no proof. Just observation.

Stock block 8 psi on pump, 12 psi on E85 is about what is safe on the FA20.

Jaden

[Ultramaroon]

Originally Posted by jsimon7777

The other day, I used my toaster as a space heater. The damn thing broke! Cheap piece of crap.

2, or 4 slice? The little 2-bangers aren't designed for high duty cycle. Ribbon elements hold up better than the coils.

[Harey]

Originally Posted by Tcoat

The stock engine is designed to make HP through high compression and revs. People blow it up by adding more compression and adding torque at lower RPMs. Then complain/wonder about how cheap the engine is built when it can't take the complete reversal of it's design criteria.

Why do people not seem to understand this very simple point?

Really good point. I spend a lot of time reading about the FA20DIT in the latest model wrx. Common advice when increasing power is to hold big torque numbers back until over 4000rpm.

I'm guessing this would be even more important on this engine.

[EAGLE5]

PSI is a terrible way to measure safety. All things being equal, 10 psi at 1500rpm is far more stressing than 10psi at 7000rpm. An excellent tuner for the FA20 would only put lots of torque at low rpm with a built motor.

10 PSI can happen at different temperatures measured at different places with different amounts of back pressure with different fuels and mixtures and timing of spark and fuel and valve opening and closing and so on. PSI seen alone is pretty meaningless.

Basically, 90%+ of what you've read about turbos and superchargers on the internet is bullshit. Just like 90%+ of what's there on the internet is bullshit. Info on turbos and superchargers is especially stupid. Took me a long time to figure it out, but I'm not an engineer.

Also, if you want to be faster on the track, invest in driver training, not car mods.

[Harey]

Originally Posted by jsimon7777

PSI is a terrible way to measure safety. All things being equal, 10 psi at 1500rpm is far more stressing than 10psi at 7000rpm. An excellent tuner for the FA20 would only put lots of torque at low rpm with a built motor.

10 PSI can happen at different temperatures measured at different places with different amounts of back pressure with different fuels and mixtures and timing of spark and fuel and valve opening and closing and so on. PSI seen alone is pretty meaningless.

Basically, 90%+ of what you've read about turbos and superchargers on the internet is bullshit. Just like 90%+ of what's there on the internet is bullshit. Info on turbos and superchargers is especially stupid. Took me a long time to figure it out, but I'm not an engineer.

Also, if you want to be faster on the track, invest in driver training, not car mods.

Completely agree.

Can you post in the do I need to build an engine for fi thread? They are trying to argue with me that torque down low is safer than up high!

[gtengr]

Originally Posted by jsimon7777

PSI is a terrible way to measure safety. All things being equal, 10 psi at 1500rpm is far more stressing than 10psi at 7000rpm. An excellent tuner for the FA20 would only put lots of torque at low rpm with a built motor.

Agree. It doesn't get mentioned often enough. And I would be wary of high boost low rpm torque even with a built motor, since most of the additional stress is due to the oil pressure at the rod bearings being much lower.

[EAGLE5]

Originally Posted by gtengr

Agree. It doesn't get mentioned often enough. And I would be wary of high boost low rpm torque even with a built motor, since most of the additional stress is due to the oil pressure at the rod bearings being much lower.

What fails depends on a lot of things. Lower oil pressure, yes. Long periods of stress on the con rods, too, as the power stroke and pressure happens over a longer period of time while moving away from the pressure at a slower speed.

[Cal3000]

Originally Posted by Tcoat

The stock engine is designed to make HP through high compression and revs. People blow it up by adding more compression and adding torque at lower RPMs. Then complain/wonder about how cheap the engine is built when it can't take the complete reversal of it's design criteria.

Why do people not seem to understand this very simple point?

This right here X100.
I've been running boost for over 130k+ miles (209k+km) and my motor is at 155k miles. My peak torque is at 6.5k rpm at 250wtq with 308whp. Most of the rev range lingers below 220 wtq which is only +90tq over stock peak. Just did a compression test in cylinder 1 and it was sitting at 190psi, basically like new.
308whp is enough to gap V8 camaros and 392s

[Irace86.2.0]

Originally Posted by Harey

Completely agree.

Can you post in the do I need to build an engine for fi thread? They are trying to argue with me that torque down low is safer than up high!

I dont agree with that, there are more forces on the rods/pistons at low rpm as there is more time under stress. A turbo running at 10psi at 4k would have more forces acting on the rods/pistons than an N/A setup at redline.

High rpm introduces other issues such as valve float etc but not higher forces on rods/pistons.

We were focusing more on the 2nd paragraph because it was a more absolute statement and because we didn't have the equations to calculate forces vs forces in your 1st paragraph.

Here is a good article:

https://blog.wiseco.com/how-a-stroke...-and-inertia.-

The force of inertia is a function of mass times acceleration, and the magnitude of these forces increases as the square of the engine speed. In other words, if you double the engine speed from 3,000 to 6,000 rpm, the forces acting on the piston don’t double—they quadruple.

This probably has to do with the fact that kinetic energy equals one half of mass times the square of velocity (E=1/2mv^2), such that, a small change in velocity results in a large change in energy.

I concede that I don't know which puts more stress or forces on the moving components, but the way I see it, an engine is more likely to survive doubling atmospheric pressure in a cylinder to 14 psi, or doubling power on the motor than trying to double the rpms. Think about it, 400hp seems easier than 14,500 rpms.

We know rpms are also valve train, flow, friction dependent, but consider this, a 2017 Kawasaki ZX10R might have a high redline of 14k rpms, but the mid 90's ZX2R had a higher redline at 20k rpms. Is this because the valve train components were so much better made in the 90's, or was it because the pistons were small and light, and most importantly, the stroke was so short (33mm)?

Also, consider the developments over the years in engine power compared to the developments in redline. It is easy to see that smaller engines are making much more power than previously, but what about rpms? I am not ignoring all the factors that go into raising the rpm of an engine. I'm simply trying to illustrate a relationship between the forces of combustion and the forces of revolutions.