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Old 08-23-2006, 02:01 AM   #1
aspera
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Default DIESEL EJ20 redline?

Assume for a minute that Subaru makes a diesel EJ series engine.

Audi has proven that an aluminum block diesel engine is do-able and the R10 is proof. Banks Power is also road racing a diesel...a truck! Banks is also trying to up the redline of diesels and trade torque for horsepower. The editor of Hot Rod magazine is calling for somebody to drop a Duramax into a muscle car.

I'm wondering if the EJ doesn't already have most of what it needs to be a diesel. First, it is already turboed. Second, it can be made to survive high cylinder pressures. Third, the heads flow really well.

Now, if the EJ engine gets redesigned diesel parts it might make an ideal tuner engine.

First, no knock. Diesel is metered by fuel, not air. So boost until the EGT guage says stop. Second, Diesels have long life. Shortening the life by modding the engine would still leave you with a durable engine. Third, pitch the throttle body, blow off valve, TGVs, and port fuel injectors. No more cussing just to change spark plugs anymore, either. Throttle-by-wire, coil-on-plug, and maybe variable valve timing all go bye-bye.

What's left is boost and rev.

So, we already know that the valvetrain is reliable well over any redline a diesel engine could do. What's left is to figure out how many RPMs the diesel bottom end could take.

Then, after Subaru makes a 6000 RPM diesel EJ, we can inject crazy amounts of nitrous and propane.
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Old 08-25-2006, 03:23 PM   #2
Master2192
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The problem is the valvetrain has to incorperate a cam lobe for the injectors. The incredible pressures (up to 28k PSI) aren't created in the fuel system, but actually in each injector. Infact you've got to use certain oils that won't push out from in between the injector plunger and the cam from all that pressure.

Then you've got the problem of the diesel's lack of ignition advance. Since its compression ignited, it has to be later in the compression cycle, depending mostly on the engines total compression ratio. Turbo charging pushes this to about 5-10 degrees earlier than normal, but its still very late for high rpm performance.

Also the high compression ratio leaves less room for rod stretch at high rpms, high rpms could cause the piston to hit the cylinder head.


Not saying it isn't possible, but there is alot to engineer around to get up to those kind of rpms. But I really doubt Subaru is going to try to push the limits on diesel. The whole point of diesel is way higher fuel economy and torque. Higher rpms = higher fuel consumption
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Old 08-28-2006, 07:54 AM   #3
aspera
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Originally Posted by Master2192 View Post
Not saying it isn't possible, but there is alot to engineer around to get up to those kind of rpms. But I really doubt Subaru is going to try to push the limits on diesel. The whole point of diesel is way higher fuel economy and torque. Higher rpms = higher fuel consumption
Good points. I'm still pretty new to diesels.

It seems like diesels already have better partial throttle fuel economy and low end torque. All they are lacking is high RPM horsepower. It seems that all that is needed is stronger parts and more boost to come closer to those power goals. That's the oppposite of most gasoline engines. They can already rev to 6K, but solving for low end torque and partial throttle fuel economy is much harder than adding stronger parts and more boost.

Maybe the solution is a better transmission to keep the diesel in the powerband.
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Old 08-28-2006, 10:25 AM   #4
SparkysJDMSpeedWagon
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Quote:
Originally Posted by aspera View Post
Maybe the solution is a better transmission to keep the diesel in the powerband.
You just answered your own question. Don't expect a normal diesel to go more than, say, 4000rpms. But with good gearing, it can stretch out the powerband and convince you that you don't need 8000rpms to be happy. Plus, don't most diesel trucks run like 35psi of boost from the factory, with the "chipped" ones running over 50psi? There's your boost fix, maybe that will help compensate for the rpm thing.
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