[JamesAllen]

So a comment made by TurboPhil in another thread and my first day out in 70°+ weather made me wonder:

Is the difference between my morning commute in 40° weather and my drive home in 75° weather going to impact the performance of my REV300 in a discernable manner?

I know it will in theory, but more curious about the real-life impact.

Along the same lines, are the power increases in the REV400 fully attributed to lower air temps (and therefore more air and more fuel), or are there other important factors as well?

 

[oldmansan]

So a comment made by TurboPhil in another thread and my first day out in 70°+ weather made me wonder:

Is the difference between my morning commute in 40° weather and my drive home in 75° weather going to impact the performance of my REV300 in a discernable manner?

I know it will in theory, but more curious about the real-life impact.

Along the same lines, are the power increases in the REV400 fully attributed to lower air temps (and therefore more air and more fuel), or are there other important factors as well?

Yes and yes. All things being equal lower intake temps will always have the potential for more power. An intercooler will help to further decrease intake temps (again, all other things being equal).

San

 

[komiko]

as i understand it, the ic gives you the extra (edit: POTENTIAL) 100 hp. It's the same blower/injectors etc.

 

[JamesAllen]

as i understand it, the ic gives you the extra 100 hp. It's the same blower/injectors etc.

That's sorta my understanding as well, but if it's that simple can I drive my car on a 0° morning and expect REV400 performance for the day?

 

[oldmansan]

That's sorta my understanding as well, but if it's that simple can I drive my car on a 0° morning and expect REV400 performance for the day?

No, the IC gives you more potential for power, not an extra 100hp as Komiko implied. Cooler IATs give you the potential for more power,.

When you compress air/fuel it becomes heated. Forced induction usually relies on an intercooler to reduce the heat in the air/fuel mixture before it enters the combustion chamber. Lower IATs allow you to make more power as timing isn't pulled as much as at higher IATs.

San

 

[turbophil]

Temperature impacts air density. higher temp=less density. Less density=less fuel. less fuel=less power... You can estimate power pretty accurately with enough inputs and the right equations. Here's what the math says. I can say from experience, the math is pretty darn close to reality as well...

With 40F Ambient with the TVS on the rev300, the ~10psi boost, fully heat saturated, your IATs will be about 147F.

With 70F, the IATs will be about 185F all else equal, you'll be down about 15whp.

With 100 degree ambients, the IATs will reach 222F, and that will drop the power another 15whp.

It's not perfectly linear that way though, as 130F ambients would only drop another 12whp or so... not quite 15 like the prior 30 degree bumps

130F ambient isn't really that far fetched either, as the air hovering above the pavement is typically quite a bit warmer than the air under shade tree on a 110F degree day...

So it's not unreasonable to see 30-45whp change from a cool day to a really hot day...

-Phil

 

[addertooth]

And then there are the poor slugs like me who are at high elevation, and high temperature.
My car pulls much better at sea level.
On the plus side, all the cars on the road with me are more or less equally affected.

 

[turbophil]

And then there are the poor slugs like me who are at high elevation, and high temperature.
My car pulls much better at sea level.
On the plus side, all the cars on the road with me are more or less equally affected.

Not only the elevation, but that overdriven M62 with no IC too!

I kid, I kid...

.... sorta

 

[addertooth]

Actually, somewhat apt Phil. I suspect IATs are worse for a given amount of boost at elevation. A percentage of the supercharger "work" produces heat; with less dense air, there is less heat carrying capacity in the air. This results in a higher IAT relative to the ambient. There is an age old discussion about MP62s being used beyond the true sweet spot (unlike the tvs1320 for the 2zz application).
I fall into the camp of people wanting a TVS, if I had the spare cash to do the TVS, Plus Clutch, plus e-153, plus E-85 conversion to put a pretty bow on it all.

 

[oldmansan]

Actually, somewhat apt Phil. I suspect IATs are worse for a given amount of boost at elevation. A percentage of the "work" produces heat; with less dense air, there is less heat carrying capacity in the air. This results in a higher IAT relative to the ambient. There is an age old discussion about MP62s being used beyond the true sweet spot (unlike the tvs1320 for the 2zz application).
I fall into the camp of people wanting a TVS, if I had the spare cash to do the TVS, Plus Clutch, plus e-153, plus E-85 conversion to put a pretty bow on it all.

Not sure where you're at in AZ, but elevation (and heat) does suck for forced induction.

In 1992 I had a 1992 Eagle Talon AWD TSI (turbo 2.0) in Colorado Springs. I drove it to Phoenix AZ and after the ECU acclimated overnight I drove it to a friend's house the next morning (cool weather) and it felt like a race car comparitively. The drive from Phoenix to Flagstaff (and then Colorado Springs) was great. When I got back to Colorado Springs and it acclimated to the elevation it felt sluggish again (comparatively).

San

 

[turbophil]

Well assuming assuming sea level, it's just back to the equations... Can always compensate for altitude of course...

For the sake of discussion, let's say you had the 62 cranked up to 10psi to make the comparison easier. They're normally ran at 7ish...

On the same 70F inlet temps as above, the 62 would be pushing out about 254F degree air vs the 186 degree air of the TVS1320 prior mentioned. All else equal, that means a delta of about 42whp between the two blowers at the same 10psi boost... fully heat saturated, no IC, and true 70F inlet temps...

IME, the math is pretty close to representing reality...

-Phil

 

[ee.engineer]

Well assuming assuming sea level, it's just back to the equations... Can always compensate for altitude of course...

For the sake of discussion, let's say you had the 62 cranked up to 10psi to make the comparison easier. They're normally ran at 7ish...

On the same 70F inlet temps as above, the 62 would be pushing out about 254F degree air vs the 186 degree air of the TVS1320 prior mentioned. All else equal, that means a delta of about 42whp between the two blowers at the same 10psi boost... fully heat saturated, no IC, and true 70F inlet temps...

IME, the math is pretty close to representing reality...

-Phil

does the disparity in the temperatures reduce once an IC is introduced?
Is anyone familiar with what conditions factory cars are tested with?
Also when people say that 300whp should not be exceeded on stock motor/trans, is the possible decrease at time of testing factored into that number?

 

[Nessal]

Isn't a turbo much less affected by elevation?

 

[turblow]

Isn't a turbo much less affected by elevation?

Well, the turbo is affected, but a turbo car can compensate far better than a NA car and lose less performance comparatively.