Ive trapped 101.5mph with 17psi and 102.3mph on 14psi...the car feels the same to me

 

yeah that guy defenitley doesn't get it.... the reason the mustang walks on u is cuz he keeps the same amount of boost and he just gains power with the cooler weather... u don't loose any power it just stays the same because the pcm LIMITS the power to the stock 260 doesn't let it go less doesn't let it go more unless u have a tune.

 

I have the Hahn's Tune and boost is the same regardless of temp. Way cool!!

 

Hes not on the stock file

 

Something must be wrong with you're car I've driven in 100 degree heat with the hahn tune 25 lbs of boost just earlier this week 32 degrees 25 lbs of boost no change no drop whatsoever I am extremley happy with the hahn tune there is no loss of power ever.

 

do all you guys with the hahn tune have A/F monitoring, or knock monitoring?

i sure hope so.

 

A change in boost corresponding to atmospheric and/or elevation changes is perfectly normal. It seems a few people may be a little too worried or concerned about their cars and are getting too caught up in the "boost = power" mentality. It does not. Boost pressure does not tell you the air mass that is going into the engine and that is what's truly important. The number of oxygen molecules in the combustion chamber will determine the amount of fuel you can burn and therefore how much power the car will make.

By definition, boost or boost pressure to be more precise is just a force exerted over a surface area. In the case of a turbocharged engine the boost pressure tells you how much the air molecules are pushing outwards against the intake tract but it doesn't tell you the density of that air, or in other words how much oxygen molecules are in that pressurized air. Without getting too far off on a scientific tangent just remember that hotter air is less dense and therefore has less oxygen content than cooler air. When you pressurize air that remains the same and a cooler charge at the same pressure will have more oxygen.

Like many modern turbocharged applications the Bosch Motronics ECU used on the LNF cars uses a torque-based engine management scheme that attempts to provide the same engine torque output (i.e. power) under all operating conditions. It can do that by altering not just boost pressure but also by making changes to things like fueling and timing. Like I mentioned a moment ago, too many people think that the boost gauge is like a "power meter" or power gauge and it's not. If you're driving at the top of a mountain range at 6k feet elevation the atmospheric pressure of the air is less and the computer will read that on it's barometric pressure sensor. It then knows that to increase wastegate duty cycle to allow the turbo to build more boost pressure to compensate and for the thinner, less oxygen dense air by shoving more of that less dense air it into the engine, hence the higher boost pressure.

The same idea applies to temperatures. In the desert where I live, during the summer months with 105°+F ambient temps I would see up to 20-21 psi of boost. The hotter air was less oxygen dense and therefore the computer had to run more boost to get the same air mass into the engine (e.g. to provide the same amount of oxygen to burn). Now that it's cooling off into the 50's and 60's at night I see under 15 psi but the car is still making the same power.

You request a certain amount of torque from the engine depending on how far you push down on the accelerator pedal and the engine responds by trying to provide that desired torque. If you go wide open throttle (WOT) and you weather has cooled off the air had higher density and it doesn't need to and won't pressurize the intake charge (boost) as much. In addition to the air being denser to start with (denser air going into the turbo equals denser compressed air coming out), the cooler charge temps also affect the intercooler efficiency. If the computer sees that the IAT (intake air temp) sensor is reporting cooler charge temps it's probably also programmed that it knows cooler air is less prone to detonation/knock and it can run slightly higher timing which when combined with the denser air (even at a lower boost pressure) will make the same power. Boost is only one piece of the puzzle.

As for aftermarket tunes, without examining the actual code the processor is using, even with a tune such as BSR's PPC or a custom HP Tuners calibration you should only be altering parameters of the engine cal and not completely running a different code. That means the same torque-based engine management algorithms are being used but some of the parameters it is shooting for have been altered or tweaked. (An analogy would be your car's computer is like your home computer. You might be able to install a different operating system such as Windows XP, Vista, Linux, or some other OS on your PC, but that's not like what happens when you use a custom aftermarket tune on your car's computer. It would be more like you're still running Windows XP but have just tweaked some setting and parameters, such as changing the screen resolution or font size, but the software itself hasn't changed and still works the same).

The seat of the pants "testing" can be highly deceiving and I know more than a few people over the years that claim their car is faster during part of the year when it hotter, colder, etc. Truth is there are a lot of factors and if you really want to tell then take the car to the track and see what the trap speed is doing or if you have an accurate dyno that can apply an SAE correction factor do a few pulls on the rollers. If you want to have a better understanding of how the car works I'd also invest in a scan tool/gauge and start monitoring things to include not only manifold boost pressure but the air mass grams/sec, ignition timing, injector pulse-width and so on.

There is a chance some cars will experience seasonal changes in power such as being due to different oxygenated winter blend fuels used in some parts of the country. And if you have a tune that is pushing the car to the limit of certain stock components under hotter/colder weather you might be able to make slightly more power than is possible under different conditions (for example on some cars they might run too lean or have too much know for the octane fuel they are running). But in the case of a near stock SS Turbo with a quality aftermarket flash or even a stock car, it may not be running as much boost and may not seem to be as fast but I bet if you do some instrumented testing the calibration of your seat pants is probably what's off.

 

My car gets no lower than 20 to 21 psi even in colder temps. It feels like a rocket in the cold weather, but as soon as it warms up i can feel it slow down, especially in traffic when the cooler gets heat soaked with no air flow over it.

That is why I can't wait for hahn's cooler to be released. should make the car as fast when its 85 in traffic as it is at 60 and on the highway!