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[Emperor]

SRY for the Noob question but i really want end a fight with my friend

when i use a charger that provide more air with less pressure i put less stress on the rods, right?

the idea behind
when i use two small t25 instead of one big (on a 2liter inline6) i pump more air with less pressure (can only boost 5psi)

and bevor talking BS
i safe already money for a set custom rods/pistons but its a along way down to 5000$

[ratcityrex]

Say you have 2 t25's and at 5 psi, the combined make 200 cfm

Say you have 1 hx35 and at 5 psi you make 300cfm


Now you tell me at 5 psi, witch one will make more power? the one that will make mor power will make more stress.

[Emperor]

ahh snap, youve right my thinking was wrong

just was thinking that that i can reduce abit stress when i flow more air with less psi


i hate those custom rods

[patsmx5]

ahh snap, youve right my thinking was wrong

just was thinking that that i can reduce abit stress when i flow more air with less psi


i hate those custom rods

Tensile stress into the rod is purely a function of RPM. While compressive stress in the rod is a function of cylinder pressure during the combustion process (IE-POWER). Generally speaking, an engine with a big turbo running the same boost as an identical engine running a small turbo, the big turbo engine makes higher peak cylinder pressure, higher average cylinder pressure, more HP.

Take two identical engines, one with a relatively small turbo, one with a relatively large turbo.  Say the engine with the smaller turbo is running 12 PSI and making 250HP. Where the engine with the large turbo is running 9 PSI and also making 250HP.

If the the turbine and the compressor efficiencies were identical between turbo's at their respective boost levels (not likely, but an assumption for illustrative purposes) , then the mass flow rate of air through both engines would almost be the same. (the smaller turbo engine would have a higher thermal efficiency from the higher dynamic compression ratio, but this is only advantageous if the engine can be tuned reach peak pressure ~14*ATDC) Both would have about the same AVERAGE peak pressure, but the engine with the smaller turbo will have a higher peak pressure, hence, a higher peak compressive loading on the rod. While the big turbo engine will have a lower peak pressure to make the same Average pressure. THIS is what you want.


Oh yeah, and this is just a sweeping generalization. It's a lot more complicated because you have to consider how each subsystem affects the other systems around it.

[Emperor]

thats why i love RMHT
always someone here that know all the shit ;D

and bevor i open a new threat
i want ask/tell the story behind

i want copy at beginning the output from a Eaton m45 with two small chargers for the simpel reason that toyota sold in past a SC kit with the m45 and its proven that the engine hold that power (LOOOOL 50hp more) easy.
My thinking
I copy the kitsettings ->5PSI+XXXccm Mass airflow(dont have the comp. map to hand),with Turbos and on the day X i can easy upgrade (bigger TUBESS and a AEM FIC) when i have my rods/pistons.
the TTE SC kit even runs without a piggyback (just a fuelcut defender and some resitor to enrichen the whole mix)

[confUsed]

I like this thread

Tensile stress into the rod is purely a function of RPM. While compressive stress in the rod is a function of cylinder pressure during the combustion process (IE-POWER). Generally speaking, an engine with a big turbo running the same boost as an identical engine running a small turbo, the big turbo engine makes higher peak cylinder pressure, higher average cylinder pressure, more HP.

Take two identical engines, one with a relatively small turbo, one with a relatively large turbo.  Say the engine with the smaller turbo is running 12 PSI and making 250HP. Where the engine with the large turbo is running 9 PSI and also making 250HP.

If the the turbine and the compressor efficiencies were identical between turbo's at their respective boost levels (not likely, but an assumption for illustrative purposes) , then the mass flow rate of air through both engines would almost be the same. (the smaller turbo engine would have a higher thermal efficiency from the higher dynamic compression ratio, but this is only advantageous if the engine can be tuned reach peak pressure ~14*ATDC) Both would have about the same AVERAGE peak pressure, but the engine with the smaller turbo will have a higher peak pressure, hence, a higher peak compressive loading on the rod. While the big turbo engine will have a lower peak pressure to make the same Average pressure. THIS is what you want.


Oh yeah, and this is just a sweeping generalization. It's a lot more complicated because you have to consider how each subsystem affects the other systems around it.

So say if you have two identical systems, both producing the same power. One is tuned with 2 degrees less timing than the other, but 2 psi more, to make up for it. The engine running the more aggresive timing map will be easier to rods/piston/bearings because of less peak pressure?

[patsmx5]

I like this thread

Tensile stress into the rod is purely a function of RPM. While compressive stress in the rod is a function of cylinder pressure during the combustion process (IE-POWER). Generally speaking, an engine with a big turbo running the same boost as an identical engine running a small turbo, the big turbo engine makes higher peak cylinder pressure, higher average cylinder pressure, more HP.

Take two identical engines, one with a relatively small turbo, one with a relatively large turbo.  Say the engine with the smaller turbo is running 12 PSI and making 250HP. Where the engine with the large turbo is running 9 PSI and also making 250HP.

If the the turbine and the compressor efficiencies were identical between turbo's at their respective boost levels (not likely, but an assumption for illustrative purposes) , then the mass flow rate of air through both engines would almost be the same. (the smaller turbo engine would have a higher thermal efficiency from the higher dynamic compression ratio, but this is only advantageous if the engine can be tuned reach peak pressure ~14*ATDC) Both would have about the same AVERAGE peak pressure, but the engine with the smaller turbo will have a higher peak pressure, hence, a higher peak compressive loading on the rod. While the big turbo engine will have a lower peak pressure to make the same Average pressure. THIS is what you want.


Oh yeah, and this is just a sweeping generalization. It's a lot more complicated because you have to consider how each subsystem affects the other systems around it.

So say if you have two identical systems, both producing the same power. One is tuned with 2 degrees less timing than the other, but 2 psi more, to make up for it. The engine running the more aggresive timing map will be easier to rods/piston/bearings because of less peak pressure?

Nope, the opposite. But let me adjust your numbers a bit to make my point. If you have two identical engines, both running the same turbo, both making 250HP. One is running 26* total advance and 14 PSI, the other is running 24* total advance (the two degrees of retard like you mentioned), then that engine will probably need to run 14.25 to 14.5 PSI to make up for the 2 degrees less timing. It won't take 2 PSI more is my point. Now the motor with 26* is more efficient, and will have slightly lower EGT's, but it will have higher peak cylinder pressures. It's a tradeoff. However, the motor with 24* has a bigger safety margin from detonation. That's the one I'd rather daily drive and beat on 200 miles from home, knowing it's safer from detonating AND has lower peak cylinder pressures.

This is why I run 11 PSI and a retarded timing map. Keeps peak pressures down as these BPs are bad about spitting out connecting rods around 300whp, and it's usually from silent detonation. People get carried away with spark and they break their shit.

[Emperor]

to say it simpel

ignition at piston down movement = less stress on the bearings
right?

[patsmx5]

to say it simpel

ignition at piston down movement = less stress on the bearings
right?

Yeah.
Less advance  + more boost to compensate = X hp with a lower peak pressure
More advance + less boost = X hp with a higher peak pressure

So more retard and more boost is easier on the connecting rods for the same power. But you'll get higher EGTs, and overall a less efficient cycle, so don't go pull 10* from your map and crank the MBC. The lower efficiency means higher temperatures throughout the engine, and places more strain on the cooling system.

[confUsed]

I've been learning new things every time I log on lately. RHMT FTW!

[patsmx5]

I've been learning new things every time I log on lately. RHMT FTW!

Some of the fundamentals to boosting are largely misunderstood. There's a lot that goes on that most never understand.

[92CXyD]

One of the best books I've read on turbocharging is Maximum Boost by Corky Bell.

There are some PDF copies of this book floating around on rapidshare.

I like how the book is tech. but not trying to bog you down with large amounts of formulas and theory.

In my Thermo I class I learn one really important eq. and that is {m_in}={m_out} , where m = mass flow

And when you aplly this to turbocharging or supercharging an engine it makes more sense than some the crap explanations on sizing turbos and S/C.

[patsmx5]

One of the best books I've read on turbocharging is Maximum Boost by Corky Bell.

There are some PDF copies of this book floating around on rapidshare.

I like how the book is tech. but not trying to bog you down with large amounts of formulas and theory.

In my Thermo I class I learn one really important eq. and that is {m_in}={m_out} , where m = mass flow

And when you aplly this to turbocharging or supercharging an engine it makes more sense than some the crap explanations on sizing turbos and S/C.

Indeed, this is fundamental. Yet many people never understand this. IE-how you can have different sized turbos, same boost, but they make different power.

I'm in Thermo II and this class rocks. 

[92CXyD]

I may take Thermo II next fall not sure yet b/c I'm still in the process of transfering to UND for ME degree.

[snarf]

to say it simpel

ignition at piston down movement = less stress on the bearings
right?

Yeah.
Less advance  + more boost to compensate = X hp with a lower peak pressure
More advance + less boost = X hp with a higher peak pressure

So more retard and more boost is easier on the connecting rods for the same power. But you'll get higher EGTs, and overall a less efficient cycle, so don't go pull 10* from your map and crank the MBC. The lower efficiency means higher temperatures throughout the engine, and places more strain on the cooling system.

You keep saying "the setup with less advance will have higher EGTs"  But if the you keep the fuel the same when you retard timming won't that extra fuel lower EGTs?