alperx

Can you please help me on making clear one point ?

There's an ls/vtec engine with two options: (for example)

1. gtx2863r turbo, 20 psi boost, 350 HP
2. T3 60-1turbo, 12 psi boost, 350 HP

if the rest of the engine is the same, do these two setups create the same amount of stress on engine sleeves ?

thanks..

Muckman

iTrader: (2)

In my opinion, yes.

dcmatt

iTrader: (7)

The way I've understood it (this amount of air)+(this amount of fuel)=(this horsepower). So just because they are running a differant psi its still the same volume of air. Look at how much boost the EVO guys have to throw @ their setups to achieve the same horsepower as a Honda with the same turbo. Hondas are more efficient flow wise so I might take 20psi with (x) turbo to reach (x) HP and 35psi to due the same thing on an EVO. I'm sure someone has a more technical answer but thats my understanding of it.

JDMAF

The term your looking for is volumetric efficiency.

2000CTRSi

If engines are the same, take the cfm of each turbo and use that to determine your answer.

You can also use the efficiency charts made by the turbo manufacturer to determine if the smaller of the 2 is outside its efficiency range. A turbo operating outside its range may cause more stress than a larger unit blowing colder air.

TheShodan

iTrader: (14)

Correct. How a turbo behaves makes a big difference whether or not it is within its best compressor "island" or not. A big turbo to the left of its range (accounting for turbine wheel efficiency of course) will be unresponsive and unsatisfactory when it barely gets into its efficient boost pressure range, even if it makes good "peak" power on a dyno. This is why you see it reach its efficient area of full pressure at a higher rpm (lag) than a smaller turbocharger using a bit more pressure to do the same thing.

the problem that specifically the Honda world has is the notion that most believe that if they get the same "peak power" desired from a dyno at a low boost pressure, that they're being efficient and have lower cylinder pressures than one that uses a bit more pressure within the efficient part of the "island". Cylinder pressure is cylinder pressure. Whether you're running 8psi or 18psi, your engine is either going to be able to handle it with the internal components inside, or it won't (within reason, of course). there's nothing wrong with 2-3 more psi of boost pressure to be within in the better part of the island and have a much better "powerband" than some peak number.

To simply say "I'm using a 6262 at 12psi on a stock block" is not efficient. It just means the stock block is handling the same cylinder pressures as one that's using a couple more psi of boost pressure with a smaller turbo, and the smaller turbo is actually more fun, because its not as "laggy" as the larger one.
I'll take a Surfer or Predator at 5-8psi more, and stomp the monkey out of that 6262 because I'm using 4000-8000rpms, and not just 7000-8500 where the 6262 would just START to get efficient.

Same goes with people wanting 450whp w/ 91 octane on a 1.8-2.2 litre. you may not get the highest "peak power", but you'll have a better powerband with 50whp less, and wipe out the "peak power" person.

dcmatt

iTrader: (7)

Predator? Is that a new one? Don't recall hearing about that one.

TheShodan

iTrader: (14)

Got a few of them now. PM me.

2000CTRSi

Dang... silver surfer... haven't heard that in a while.

Spot on answer from the shodan as expected.

Billspec

gabocastano

Everybody wants to know about the predator

TheShodan

iTrader: (14)

PM me. I'll have public info about it in a few days.

cruizinmax

iTrader: (2)

You also have to look at the torque number as well. The smaller turbo will make boost faster and produce more torque in the lower rpm range. The cylinder pressure could very well be higher than the larger turbo that makes less torque but carries it out farther.

TheShodan

iTrader: (14)

Absolutely.. And if the cylinder pressures are slightly higher, its really to the point to where the engine will either handle boost or it won't. You've either built the car for turbocharging or you haven't. cylinder pressures would be more of a constant, not a variable.