What is boost?

[sergei]

My latest setup made 195kW with 540cc injectors (still gen1 block) at 16psi, with plenty of fuel (safe tune, which would be on richer side).

what dyno? i made 200kw on 21psi and maxed my 540cc injectors with gt2860rs on soichis dyno. Originally 220kw but dialed back since it knocked when heatsoak set in

Torque Performance.

[sergei]

power gain = P2T1 / P1T2 where P2 boost+1bar after increase, P1 boost+1bar before increase, T1 is inlet temp before increase, and T2 is inlet temperature after increase. Here is an example:

P2 = 2.3bar
P1 = 2.0bar
T1 = 70'C
T2 = 100'C


The power gain is = (2.3 * 70) / (2.0 * 100) = 0.8 (or 80% of what you are started with), even though you are increasing boost, due to extra inlet temperature you are in fact losing power.

And yes, it is possible to go from 70'C to 100'C inlet when the turbo charges falls off efficiency range. The over spun turbos can push out temps as high as 160'C

I think you've got that wrong. Temps should be in °K not °C so the result is;
(2.3*343)/(2.0*373) = 1.06, i.e. a 6% increase.

You are very right.
But that shows that 30% increase in boost != 30% increase in power.

[gt4dude]

My latest setup made 195kW with 540cc injectors (still gen1 block) at 16psi, with plenty of fuel (safe tune, which would be on richer side).

what dyno? i made 200kw on 21psi and maxed my 540cc injectors with gt2860rs on soichis dyno. Originally 220kw but dialed back since it knocked when heatsoak set in

Torque Performance.

I don't understand why you made the same power with significantly less boost and more fuel in reserve.

Did you have cams or what?

[sergei]

My latest setup made 195kW with 540cc injectors (still gen1 block) at 16psi, with plenty of fuel (safe tune, which would be on richer side).

what dyno? i made 200kw on 21psi and maxed my 540cc injectors with gt2860rs on soichis dyno. Originally 220kw but dialed back since it knocked when heatsoak set in

Torque Performance.

I don't understand why you made the same power with significantly less boost and more fuel in reserve.

Did you have cams or what?

stock cams, Gen1 engine with TVIS removed (as it was broken). Probably CT20b is more efficient in the flow/boost range I was using it compared to GT2860rs (there no compressor maps available for CT20b to compare).
What ECU are you using? Switching to Link from random Blitz chipped ECU gave me extra ~15kw or so.

[Lith]

My latest setup made 195kW with 540cc injectors (still gen1 block) at 16psi, with plenty of fuel (safe tune, which would be on richer side).

what dyno? i made 200kw on 21psi and maxed my 540cc injectors with gt2860rs on soichis dyno. Originally 220kw but dialed back since it knocked when heatsoak set in

Torque Performance.

I don't understand why you made the same power with significantly less boost and more fuel in reserve.

Did you have cams or what?

Remember you made 220kw, and it was dialled back - that "dialled back" is more likely to be timing than fuel, so going from what you have said your car is actually moving the air and fuel required to make 220kw and if it weren't octane limited that's where it would sit. It intrigues me that they felt they needed to pull 20kw out of it, it makes it seem like either they pulled it back more than it needed to be - or they pushed it way harder than they should have during tuning to reach that 220kw in the first place.

[gt4dude]

My latest setup made 195kW with 540cc injectors (still gen1 block) at 16psi, with plenty of fuel (safe tune, which would be on richer side).

what dyno? i made 200kw on 21psi and maxed my 540cc injectors with gt2860rs on soichis dyno. Originally 220kw but dialed back since it knocked when heatsoak set in

Torque Performance.

I don't understand why you made the same power with significantly less boost and more fuel in reserve.

Did you have cams or what?

Remember you made 220kw, and it was dialled back - that "dialled back" is more likely to be timing than fuel, so going from what you have said your car is actually moving the air and fuel required to make 220kw and if it weren't octane limited that's where it would sit. It intrigues me that they felt they needed to pull 20kw out of it, it makes it seem like either they pulled it back more than it needed to be - or they pushed it way harder than they should have during tuning to reach that 220kw in the first place.

I made 168kw on 13psi, 180kw on 16psi and thats in a couple rows before the one that got dialed back. I dont understand where your 15kw came from, my figures are pretty consistent with tuned st205s running ct20b with the difference being my garrett is happy going over and beyond 1.2bar without blowing out an exhaust wheel

[Lith]

As I specifically said, I was purely going from the numbers in the post I quoted - which only mentioned 220kw and 200kw, and was just pointing out that it meant your boost level and fuel requirements would be off from your power figure as a result... but forget I said anything, as you were.

[sergei]

My latest setup made 195kW with 540cc injectors (still gen1 block) at 16psi, with plenty of fuel (safe tune, which would be on richer side).

what dyno? i made 200kw on 21psi and maxed my 540cc injectors with gt2860rs on soichis dyno. Originally 220kw but dialed back since it knocked when heatsoak set in

Torque Performance.

I don't understand why you made the same power with significantly less boost and more fuel in reserve.

Did you have cams or what?

Remember you made 220kw, and it was dialled back - that "dialled back" is more likely to be timing than fuel, so going from what you have said your car is actually moving the air and fuel required to make 220kw and if it weren't octane limited that's where it would sit. It intrigues me that they felt they needed to pull 20kw out of it, it makes it seem like either they pulled it back more than it needed to be - or they pushed it way harder than they should have during tuning to reach that 220kw in the first place.

I made 168kw on 13psi, 180kw on 16psi and thats in a couple rows before the one that got dialed back. I dont understand where your 15kw came from, my figures are pretty consistent with tuned st205s running ct20b with the difference being my garrett is happy going over and beyond 1.2bar without blowing out an exhaust wheel

[RedMist]

Seems to be the thread to pose a quandary.

VQ35, stock engine in both instances.

240rwhp NA
537rwhp on 12.4 psi of boost.

If we ignore the flow restrictions, (which will be greater in the boosted application as there is a greater mass of air and no changes to porting), and the obvious temperature increases, which will decrease density, on a turbo engine.

How does considerably less than twice the mass of air, make well over twice the horsepower?

Constraints: I believe the NZEFI dyno (turbo) to be accurate if not a little low reading. I've stuck a high estimate of the dyno plots for NA engines I've seen on the internet. I am running E30 in the turbo, which will account for some, but I don't believe all of the increase in power.

And No, the answer isn't Helmholtz.

[Lith]

Are you assuming it isn't moving twice the air mass because of boost level, or by calculating the actual air mass which has been moved?

Also, pumping losses are an interesting thing.

[RedMist]

Are you assuming it isn't moving twice the air mass because of boost level, or by calculating the actual air mass which has been moved?

Also, pumping losses are an interesting thing.

Ideal gas law. PV = nRT

Given temperature (T), volume(V) and gas constant (R) are constants. Any increase in pressure is a directly proportional increase in moles. Double pressure, double moles.

[Lloyd]

A little bit hard to compare an estimated standard tune on standard exhaust/intake setups from a production car to a turbo version in an offroader with a completely different tune (A/F, timing etc) running different fuel and assuming "boost is the only factor" changing anything.

Ideal gas law is wonderful in a lab, and more of a rough guideline in reality.

[fielderz]

Are you assuming it isn't moving twice the air mass because of boost level, or by calculating the actual air mass which has been moved?

Also, pumping losses are an interesting thing.

Ideal gas law. PV = nRT

Given temperature (T), volume(V) and gas constant (R) are constants. Any increase in pressure is a directly proportional increase in moles. Double pressure, double moles.

No, temperature is very unlikely to be constant, pv=nRT is only applicable to isothermal conditions, and unless the system has a VERY good intercooler then pv^n= constant applies. Also the friction ("restriction") is proportional to the square of the velocity of the air...

[gt4dude]

maybe torque's dyno is just more optimistic than soichi's?

[Lith]

Ideal gas law. PV = nRT

Given temperature (T), volume(V) and gas constant (R) are constants. Any increase in pressure is a directly proportional increase in moles. Double pressure, double moles.

I am very familiar with all of the above, but thanks for re-re-iterating. So you actually know why your car made proportionally more power than "P" and just sharing the brain teaser, or you don't know why but aren't willing to explore the option that if you are getting results you aren't expecting then it is inevitable there are parts of the puzzle you are missing?

[sergei]

maybe torque's dyno is just more optimistic than soichi's?

Do you know why do you have drop in torque at ~4500rpm?

[RedMist]

No, temperature is very unlikely to be constant, pv=nRT is only applicable to isothermal conditions, and unless the system has a VERY good intercooler then pv^n= constant applies. Also the friction ("restriction") is proportional to the square of the velocity of the air...

Pointless. I stated it was a constant only because it can only have a negative effect on density and hence mass. i.e. it makes it even harder justify the HP I am making.
I'm attempting to make this simplistic only because the figures simply don't add up even by hugely disadvantaging the turbocharged installation (with such things as calling T a constant).

[RedMist]

Ideal gas law. PV = nRT

Given temperature (T), volume(V) and gas constant (R) are constants. Any increase in pressure is a directly proportional increase in moles. Double pressure, double moles.

I am very familiar with all of the above, but thanks for re-re-iterating. So you actually know why your car made proportionally more power than "P" and just sharing the brain teaser, or you don't know why but aren't willing to explore the option that if you are getting results you aren't expecting then it is inevitable there are parts of the puzzle you are missing?

No, I simply have no idea. It defies my logic, hence my logic is wrong. It's an interesting quandary, one that I'm happy exists, but still haunts me. I'm certainly willing to explore options, however your answer is also not logical. I'm not discounting it on any other basis than the only options for your answer to be correct is for either the gas constant to change or for temperature to fall in the turbocharged installation.
Pressure is set (at two values), volume (of the stroke) is set, lets assume the gas constant is set, T, n are the only values you can change and they are not independent. Change one, and you must inversely effect the another.


I believe that there is an external force in act. That being fuel. Either I'm getting significant amounts of O2 from the fuel (E30) or the fuel is supplying a more constant torque force to the piston head. Both of which are true to a minor extent however given stoichiometric, and Octane values for E30. However I simply can't see that is true for the amount of power I'm getting over and above less than a bar of boost.

[Lith]

I am very familiar with all of the above, but thanks for re-re-iterating. So you actually know why your car made proportionally more power than "P" and just sharing the brain teaser, or you don't know why but aren't willing to explore the option that if you are getting results you aren't expecting when it is inevitable there are parts of the puzzle you are missing?

volume (of the stroke) is set

So you believe that the engine is operating at 100% volumetric efficiency regardless of situation? Ever tried modifying the intake or exhaust on an NA car? P or T (as measured at the intake manifold) doesn't tend to change there either

I believe that there is an external force in act. That being fuel. Either I'm getting significant amounts of O2 from the fuel (E30) or the fuel is supplying a more constant torque force to the piston head. Both of which are true to a minor extent however given stoichiometric, and Octane values for E30. However I simply can't see that is true for the amount of power I'm getting over and above less than a bar of boost.

The fuel used will certainly be a major part of that equation, yes. The air content is fairly insignificant, with E30 you are probably only introducing about 1.5% more air to the combustion process if you were on straight petrol previously. The more consistent gas expansion is a good thing to be thinking about, and and is not just because of the fuel type There is more to consider than that too.

Boost is awesome, especially when you get ethanol involved!

[RedMist]

So you believe that the engine is operating at 100% volumetric efficiency regardless of situation? Ever tried modifying the intake or exhaust on an NA car? P or T doesn't tend to change there either

.[/quote]
Nope, I'm assuming that the NA is only 100% volumetric efficiency at peak HP. And yes I'm fully aware of Helmholtz, have heavily modified many an NA engine. My last NA 4age (miniature port) put down 178whp before running out of flow... because we designed it that way.
However after your last post I had considered that there may be a negative P in action on the NA (after all 300hp, crank from a 3.5ltr may not be 100% VE). This combined with an oxygenated fuel of higher octane (slower burn), may be the discrepancy I'm seeing.... but it still looks odd. What appears to be well under double the O2 creating well over double the HP.