Phil99vette

iTrader: (11)

Here is my question. What difference does the power adder play in how much cylinder pressure your engine makes? Here's what I am trying to figure out...

Setup 1:
High Compression Big inch motor makes 900rwhp
Lots of cubes: 450+ CID + high compression

Setup 2:
Low Compression 340-360 inch motor that makes 900 rwhp
- turbo motor boost comes on progressive like any normal setup.

Setup 3:
Medium Compression 340-360 inch motor that makes 900rwhp
- Nitrous motor with a progressive controller to control cylinder pressure spikes, each stage is phased in over 1 second to mimic how a turbo comes on line.

Which setup would be more durable assuming the tune was dead nuts on and you bang on it all the time???
Phil

Beast96Z

iTrader: (21)

I would assume that the big inch motor would be the most durable due to the fact that it will see the lowest cylinder pressures. The power adders should signifigantlly increase the pressures in the cylinder, thus wearing on the rings or gaskets, thus making your chances for premature failure more iminent. Not sure if that was the answer you are looking for, but that's the way I would see it durability wise. I guess we could also do a comparison between your car and mine. My 454 CI/265 ET headed motor vs. your 346 No2 motor. First one to blow up looses. Literally.

white2001s10

iTrader: (4)

IMO big inch parts are much stronger, but you generally have to spin them faster to reach that kind of power level. The extra mass can become a liability, and lightweight parts can cost a fortune.

The power adders allow you to reach that power level at lower engine speeds, so it then comes down to a matter of heat management which one would survive longer.

Turbo engines are generally trickier to control the tune, and harder to manage the heat, but in practice tend to be fairly reliable. According to the books, they are easier on parts than any other power production method.

Nitrous engines are much easier to tune and manage the heat, but in practice people tend to find the mechanical limits of the engine quicker... maybe due to the massive torque production.

Phil99vette

iTrader: (11)

My thought is if you have one of the new nitrous systems that allows you to bring the nitrous on depending on the RPM it will make it more like a turbo or supercharged application.
Phil

Beast96Z

iTrader: (21)

That could be true, but a forced induction motor will still see much higher cylinder pressures than a N/A motor. It comes down to how well built and well tuned th ediffrent set-ups are as to how long they will last.

v8pwr

iTrader: (19)

The turbo engine would be the most durable . The other engines would definitely need rpms to attain those power levels . The big inch n/a engine is exceeding 2hp per cubic inch , considering any ls1 that size has been stroked you'll have some high piston speeds , same for the small nitrous motor but it has spray to account for what you can't make n/a . With race fuel the turbo motor will have a realtively easy time making the numbers and if built properly can lead a fairly long life . All of these engines would require special attention just to be a reality let alone "durable" .

Beast96Z

iTrader: (21)

That's a good point. I didn't consider the HP levels into the considering factor of durability. If you had a LSX based motor making 900hp N/A, you would probablly run into some durability issues somewhere. If it were my goal to obtain 900 hp, I would choose a turbo for longevity and driveability among other things.

Ben R

Cylinder pressure is torque, not horsepower.

treyZ28

MEP = Pressure on piston
VE = Torque
Torque at a given RMP is power.


As you can sea, pressure doesn't mean power. you can have two engines with the same pressure and one can make 5x more power depending on displacment and rpm.

Constant power, displacement and rpm engines will have roughly the same IMEP values (indicated mean effective pressure. BMEP, what it puts out. So I - L (losses like friction or pumping losses or a blower) = B

Ric

Good point, Ben. I've always contended that torque is what tears apart an engine, trans, read end, you name it. Not horsepower. Understood that stupid high rpm will cause an engine to fly apart... that aside, if you run into things like broken rods, failed main bolts/studs, or broken cranks, chances are, the torque output broke it, not the hp.

As far as banging on it all the time, why not a turbocharged big-inch motor? It would be able to make the big power of the NA big motor without having to go stupid crazy on things like wild cam, triple valve springs, and other things that would shorten the life expectancy of the engine. Simply put, given a specific power goal, a big turbo motor could use a milder cam, meaning milder springs, which means less wear on the timing chain, pushrods, valve stems, valve seats, etc. and make the same power as a big-inch NA race engine, and do so more reliably.

treyZ28

lets not forget other failure moders introduced with a turbocharger. You have oil and coolant that need to go in and out of the this snail shell shaped thing revving to 100,000+ rpm, more tubing, tighter packaging, things under positive and negative pressure, something that will be much harder to tune and a lot of other varriables.

depending on your goal, boost may not be the answer.

Ben R

IMHO, bad tune-ups brake parts. VERY rarely do parts just 'fail'. It's either due to improper machining/assembly or a bad tune-up. RPM will hurt parts faster than you could ever imagine. Turning twice the RPM results in 4 times wear.

Patrick G

iTrader: (14)

The high rpm that the NA motor will need to achieve 900 hp is also very hard on the supporting driveline parts...transmissions, driveshafts, rear ends, clutches, converters, etc.

I've seen 200-4R transmissions live behind an 800 hp Grand National (turning a max of 5500 rpm) and die behind a 450 hp LS1 (turning 6800 rpm). RPM is harder on other things besides just the motor. Keep this in mind when you're talking durability.

speedz06

cylinder preassure is fine,but where at?I think better power comes from how long you maintain cylinder preassure throughout the power stroke--how do you achieve this?I dont know.I have 80000 miles on a 550rwhp car the takes a beating like a *****.If I ever get a 900rwhp setup to beat the **** out of daily we'll see.

treyZ28

Very true. Bored? Make a graph.

Piston velocity vs rpm

Piston G's vs Rpm

Investigate fatigue in metals. Then check out the forces on a 327 con-rod at 9,000 rpm.

Pressure on a piston usually isn't too bad so long as its well distributed (ie, not detonation). Hydrolocked rarely crack pistons. Why? Hydrostatic pressure is very equal in its distribution. Check out metal strength and then measure a piston. you'll be suprised how bad *** metals are

go figure, numbers work out and physics wins