[e.n335]

Hi,

Does boost pressure raise with ambient temperatures. Concrete, if a PROcede V2 user now sets user torque settings for a 15psi tune ( 94% ), will this user see more than 15psi on hot summerdays ?

Or is it the other way round. Colder ambient temps, more boost. This would be logical, because the air is more dense. The question is what does the ECU / PROcede V2.

Thanks,
Eugen

[sleepdoc]

I thought about that too... I had a 3rd gen tt RX-7. When it was cold out, my boost would go way up. Blew a motor that way.........

[cn555ic]

OH so if we are seeing boost of 15 during winter, summer it will be significantly less....If thats the case i guess there has to be a winter/ summer torque value adjustment!!!!

[OpenFlash]

Not quite. We've mapped the boost table to be somewhat self corrective below a certain User TQ value. Meaning that it will harder to induce boost pressures over 15psi even ambient temps were to increase significantly. Not something I've mentioned because I don't want people arbitrarily jacking up the numbers and thinking that they wont run any more than 15psi.

Shiv

[sleepdoc]

So, if ambient temp is high, say 90, you will see higher boost than at 50 degrees?

I remember seeing the opposite with my RX-7.....

If boost pressure is higher at higher ambient temps, why is the car faster when the weather is cool?

I suppose when I get my v2, I should set the TQ in warm/hot weather.

[e90AW335i]

Originally Posted by sleepdoc

So, if ambient temp is high, say 90, you will see higher boost than at 50 degrees?

I remember seeing the opposite with my RX-7.....

If boost pressure is higher at higher ambient temps, why is the car faster when the weather is cool?

I suppose when I get my v2, I should set the TQ in warm/hot weather.

I believe that is correct....Shiv explained it in another thread...

[e90AW335i]

Here you go..... (see I listen to you Shiv..)

Originally Posted by shiv@vishnu

What does all this stuff mean?
That the factory ECU is a lot smarter than we give it credit for with regards to controlling power output. It also means not to get so hung up on boost pressure. Yes, monitor it. Either through a boost gauge or through tuning software (if available). But realize that it does not equal engine load which is the real determinator of how much work an engine is doing. Boost will change as a function of charge air temp. Which means:

1) That during a 1st to 4th gear run, you will see more slightly boost in 4th gear than you see in 3rd. Slightly more in 3rd that you see in 2nd. And more in 2nd than you saw in 1st (ignoring throttle closure caused by traction control of course).

2) On hot days, you will see more boost than you do during cool nights.

3) That a good intercooler upgrade will actually lower your boost pressures based upon its ability to cool the air better.

4) If you idle your car for a while (which will increase charge temps due to intercooler heatsoak, heat saturation of ic pipes, etc,.) you will see more boost when you immediately take off and begin a run. Conversely, if you are cruising alone the highway for a while (intercooler and piping is nice and cool), you will see slightly less boost than normal when you jump the throttle. Boost pressure will then rise, during the run, as things get hotter and intake charge increases.
.

[OpenFlash]

Originally Posted by sleepdoc

So, if ambient temp is high, say 90, you will see higher boost than at 50 degrees?

I remember seeing the opposite with my RX-7.....

If boost pressure is higher at higher ambient temps, why is the car faster when the weather is cool?

I suppose when I get my v2, I should set the TQ in warm/hot weather.

yep.. the 3rd gen RX-7s ecu doesn't do what the BMW ecu does. It's no coincidence those cars are ticking time bombs. I had one, went through a couple of motors, sold it, bought a WRX and never looked back

Unlike the BMW, the RX-7 didn't lower boost pressures are air density went up (to compensate for the mass airflow reduction). In fact, it effectively did the opposite which caused the car to run nearly a full point leaner. Combined with hot temps which reduced knock resistance, and the tendency of boost pressures to spike during single to dual turbo transition, the engines went BOOM. Of course, having a fragile engine that wouldn't take even one solid ping didn't help matters either. Great car. Crummy motor.

shiv

[midlife]

Originally Posted by sleepdoc

I thought about that too... I had a 3rd gen tt RX-7. When it was cold out, my boost would go way up. Blew a motor that way.........

sorry to hear that... but our cars are pretty smart correct? the ecu will not allow overboost that would cause engine failure correct ? (unless your ecu tune screw up).

[zenmaster]

Originally Posted by shiv@vishnu

yep.. the 3rd gen RX-7s ecu doesn't do what the BMW ecu does. It's no coincidence those cars are ticking time bombs. I had one, went through a couple of motors, sold it, bought a WRX and never looked back

Unlike the BMW, the RX-7 didn't lower boost pressures are air density went up (to compensate for the mass airflow reduction). In fact, it effectively did the opposite which caused the car to run nearly a full point leaner. Combined with hot temps which reduced knock resistance, the engines went BOOM. Of course, having a fragile engine that wouldn't take even one solid ping didn't help matters either.

I also went through 2 13B-REW engines (and 1 set of turbos) on my '93 RX-7 (back in '95). First BOOM was due to apex seals going out - probably a knock event. Not very robust mechanically. 2nd BOOM was caused by water flooding into engine due to heat-weakened O ring. Those engines could last as little as 60K mi., completely stock.

[sleepdoc]

Thanks! Makes more sense now.