Having a FI C5 myself, I'm pretty impressed that I can get ~500 RWHP from a basically stock 5.7 L motor. Here's my dilemma...how is it that the import guys are getting 800-900 HP out of six cylinders? There's a Lexus SC300 that runs 9.xx runs with a stock bottom end...WTF?

Here's a dyno chart of a turbo supro. The freaking thing is making over 1300 HP!! From a 6 cylinder!! Granted they rev the **** out of it, but look at the HP at 6K RPMs (about where our redline is at) it's making over 750HP.





I love the C5 to death, but am still boggled at how the 6 bangers are doing this...

 

I know what you mean, I also wonder why its so much easier to make more power on thoes cars, I made almost 50 hp with exhaust and a tune on a WRX, its crazy.

 

It might have something to do with 30-40psi boost?

 

yes but look at the tq below 4500rpm <250

thanks but I will stick with my little bitty 500rwtq at 3k rpm.

I would not like driving that car on a daily basis.

More Than Zero

 

30psi

 

Any idea why the import 4 and 6 cyclinders can handle 30 and 40 PSI of boost? I love driving the torqueee LS1, but wonder what is so different between the motors that prevents us from running that much boost without blowing pistons or head gaskets. There's a guy running a Lexus SC300 on stock internals at around 38 PSI. Supposedly been drag racing this way for a year or so before the motor let go. BTW, he's in the 9's in a 3800 # car with a 6-speed. All I can say is WOW. Not that I'd give up the C5 to drive a Lexus, but it might be fun for a little while

 

Those rice burners make so much power for a simple reason. They are short stroke engines. It's the same reason the 68 302 SBC Camaro made more power than the 69 396 BBC car.

The shorter the stroke, the higher the RPM you can get- as a general rule (there are exceptions). The reason Indy cars or F1 cars make so much power and go so fast with such small engines is because they are running 14000 to 20000 RPM! They are running something stupid like 1.5 inch strokes! They have virtually no torque (or power) when at a stand still which is why you see them stall out all the time. Remember the goal- make as best an air pump as you possibly can.

If your stroke is short, your rod has less mechanical advantage on your crankshaft- which means it isn't stressed as much at a same hp level as a long stroke engine. This means that your piston can make more force on that crankshaft without the fear of breaking it. As long as your valve train can handle the RPMs, your rotating assembly will be able to withstand more abuse than a long stroke motor. Also, with the shorter stroke, a higher boost level can be used because there isn't as much air being shoved into the cylinder- so to speak. At high rpms, your volumetric efficiency goes way down, so you need to increase the boost significantly just to get your VE back to 1.

Now, this seems to fly in the face of the rule (bigger is better). That's true. With a short throw crank, you won't be able to have as much power downstairs. As stated earlier, your mechanical advantage on a short crank is much less than a long one, so the same piston pressure on the crank will result in less torque (and power) than a long throw crank.

Ok, now that you are confused, I'll throw this in. The reason a high rpm motor makes more power than a low rpm motor is the one thing almost all engine builders forget or don't even think about. The biggest friend for performance engine builders is Newton's first law- and object in motion will tend to remain in motion. What that means for us can be stated in one word- momentum.

Think about this, lets say we spin up a corvette motor to 3000 rpm. Now lets shut it off and force the engine to stop instantly. Imagine the massive amount torque generated from suddenly stopping that engine. Now lets spin it up to 6000 rpm and do the same thing. Ah ha! Lots more torque, right? Now lets spin up a 4 cylinder rice burner engine to 9000 rpm and stop it suddenly. You can begin to see why higher rpm motors generally make more power- free power through the momentum of the rotating parts.

Now, generally speaking, with longer stroke motors, getting them up to high rpm requires extremely ballanced parts and very solid mains. But with short stroke engines, the crankshaft forces are less, and therefore able to withstand these rpms. Also, with the higher rpms, there is less time for the induction system to fill the cylinder with air (1/150 of a second at 9000 rpm)- and we have the ability to use much more boost without worrying about getting too much air in there. So, now we have an engine that is getting a good VE at high rpms producing a ton of power.

But, that being said, let's do the same thing to a Nextel Cup engine. These engines are longer stroke, but precisely ballanced and very very stout. They are already efficient enough to turn 9000 rpm normally aspirated. What if we put in some boost to get it to a VE of 1 or better at 9000 RPM? I'm guessing we'd first get the engine to turn about 12000 rpm. I'm also gussing we'd get 1500 hp without much problem. On 350 cubic inches.

So, the rules still apply, we just have to look at it and realize what they mean:
Cubic Inches rule, and The Best Air Pump rules.

If you have a smaller engine but a much better air pump, you will win. It's up to you to gear your car so that you can take advantage of HOW your engine pumps air (what rpms, etc.)

Hope that makes sense...

 

The supra and the sc300 have forged motors from the factory...... that is why they can make so much hp w/ boost.

 

Don't ever forget that those guys bombed Pearl Harbor. They will do anything for some attention.

 

its all about the internals.. no stock car would be able to take 30psi.. or 25 for that matter.. they build theirs up the same way we build ours up.. if you put all forged internals in an ls1 and sleaved the block.. im sure you could run a high ammout of boost.

 

No - a bone stock 2JZ can take 30 psi all day long with the proper fuel.

Also - the stock rods are forged - the pistons are cast... but coated as well. Anything over about 700 rwhp and the rods will be the first to check out.

 

Holy Irrelevant Bull****, batman!!!!!

Anyway, Muncie, youre not exactly comparing apples to apples here. Ditto to what the poster above said, the supra motor is strong as hell from the factory. My friends car laid down 800+ rwhp on a stock block and the damn thing had 115k miles on it!

BUT.

The car made boost at 5k rpms. His redlined at 8k so it was that bad of a powerband once rolling (I never saw him lose to anyone) but nonetheless, decide for yourself if you want no action under 5k, and them BLAM! hit in the back by a freighttrain at 4900rpms. Plus this excitement always happens on unobtanium type octane, and these cars are RARELY driven even 10% of the time in "full kill" mode. More like 15lbs of boost driving around, and then 200lbs on the dyno of all places. Many of the really wellknown high hp supra guys like to build a hugely powerful car, lay down an enormous number, and park it right back in the garage or sell it.

There are definitely exceptions like Ryan Woon, Saad, Marko D, who build and race incredibly fast supras etc, but its a very different ball game and for you to just look at a dyno sheet and say "omg they are doing it right and we arnt" is doing yourself a disservice.

 

Except I thought that was Newtons 3rd law of motion!
BTIBWB

 

What they said....the bean counters took a vacation when the lead engineer on that engine program picked out their parts.

It is overengineered to the nth degree.

Personally I'd love to get a Lexus of a vintage that motor would fit in and put a smaller BB turbo on it to make around 500rwhp, get a better spool out of and make it a DD.

Not it doesn't spool hard but even in the ramp up its making good torque.

 

No its the first...The third law is every action hasa an equal and opposite reaction. And for kicks the second law states that when a force acts upon a body it creates an acceleration proportional to the force and inversely proportional to the mass. And for all the ferrari owners out there, back to your regular red neck Corvette talk

 

Nobody seems to have realized that the engine in the vette is a V-8 and the others are in-line motors. The 4 cylinder motors have the same number of main caps and bearings as the V-8, and the 6 cylinder has 2 more mains! All the forces are balanced in the in-line 6, while the V-8 is neither balanced nor does it have enough mains to keep the bottom end strong. Against all these odds, there are still plenty of LSx motors making 1500 rwhp.

 

It's all about the 30+ boost levels and the high RPM's.

 

You may want to check out turbobuick.com. Some of those guys are doing the same thing with a little old 3.8 V6. It's all about boost.

 

Dude, the reason a high rpm motor makes more power than a low rpm motor has nothing to do with momentum. It's because there are more combustion events, and more fuel-air is being burned, assuming that volumetric efficiency still remains reasonable at high rpm.

"Momentum" is only a factor when engine speed CHANGES. At a steady rpm on a dyno with a brake, power is no different whether your flywheel weighs nothing, or 500 pounds.

Rotating mass or inertia will affect measured power on a dyno if the engine is accelerating or decelerating, but only then. In some racing situations, acceleration can be improved by reducing rotating mass.
On the drag strip though, most of the energy used to accelerate the engine is recovered when you shift. Uh, that's why you feel that jerk when you shift. If you run through the traps at the same rpm as you launch, engine rotating mass or engine inertia means little except it adds to the total weight of the car.

No free lunch, no "free power".

 

Except for turbos.