The Horsepower Sine Wave
Jun 27, 2008, 12:17 PM
#1
The Horsepower Sine Wave
I've been tweaking on cars for almost twenty years. I've been tuning them in some capacity for eight years. I've had a little experience with several kinds of racing: Drag racing, autocrossing, a track day, dyno racing (LOL), and sadly, bench racing.
One thing that I always notice is that there are people with wildly varying results and different interpretations as to why. When driver skill is the best it can be and his/her potential is maximized, its time to look closer at equipment.
At the start of the millennium, I started "tuning" with an Apex-i V-AFC (and I use that term really loosely, since they only controlled fueling), shortly after selling my 2G DSM and having a little experience with friends SAFCs. I drove a 2000 Honda Prelude at the time, and it is pathetically slow by today's standards. But I did basic breather bolt ons and tweaked the V-AFC on the dyno to see gain that was acceptably better than stock for an NA-4 that had few tools to make faster. It came to 176whp. I also drag raced the **** out of that car and learned how to cut the best 60 foot I could on street rubber with an open diff front wheel drive. Anyway, I pulled out a little ahead of my other Prelude friends and broke into the 14s. I finally got the car to 14.54@96.16mph with a 2.0 sixty foot and backed it up with a nearly identical run.
My friends and people on the Prelude Yahoogroup were all fighting to hit 14.99s, and I was a member of a well known Honda web board. Well, some guy in Jersey, who remains an online buddy to this day, ran a 14.6x@94.x in his 1999 Civic Si. He was making claims that his car was a Prelude destroyer, and page after page of useless chest beating over slow-as-***** cars ensued.
We went way too deep into the data, and started comparing several other cars from our tracks. It turned out that his track just flat out had quicker AND faster cars, and I wanted to know why. I'm sure you all know where this is going, but it ended up being track conditions. His timeslip came from racing at E-town at dang near sea level in a cool 40 degree night in Jersey. My best timeslip came from racing in the Southeast at 80 degrees and like 95% humidity.
The BS stops at the track where the rubber meets the road, but if you aren't at the same track in the same conditions, there's more BS to contend with.
This is an apt comparison for dynos. Thank goodness for correction factors, because if you added mods on certain hotter days, it could look like you lost a ton of power.
So imagine your actual (uncorrected) power as sine wave, going up and down. You're right near zero on a comfortable spring of fall day, you're car feels ***** to the wall fast in the dead of winter, and it feels lethargic and sluggish in the heart of summer. Super low humidity and cold, dense air have a profound effect on horsepower.
I think we forget about this often, because the seasons change very slowly, and its kind of like bring an egg to a very slow boil- the change is so subtle that you don't notice it. Now this is not a terribly big deal, because the other cars on track with you are all ingesting the same air your car is.
So where's the point in all of this? The point is that the horsepower sine wave for turbocharged cars realize higher highs and lower lows. You can minimize those lows a bit with an efficient intercooler. You can minimize potentially dangerous highs with a stable boost control method that does not spike badly in the cold. I've seen many engines lost in DSMs, Evos, and Subies from the owner with an unreliable boost control method going WOT in twenty degree weather only to achieve 28psi in fifth gear on 93 octane in a car that was tuned for 23psi.
My point of this thread is to open up a discussion of how we can help each other think of how to maximize the safety of the highs and improve the power of the lows.
Happy motoring.
One thing that I always notice is that there are people with wildly varying results and different interpretations as to why. When driver skill is the best it can be and his/her potential is maximized, its time to look closer at equipment.
At the start of the millennium, I started "tuning" with an Apex-i V-AFC (and I use that term really loosely, since they only controlled fueling), shortly after selling my 2G DSM and having a little experience with friends SAFCs. I drove a 2000 Honda Prelude at the time, and it is pathetically slow by today's standards. But I did basic breather bolt ons and tweaked the V-AFC on the dyno to see gain that was acceptably better than stock for an NA-4 that had few tools to make faster. It came to 176whp. I also drag raced the **** out of that car and learned how to cut the best 60 foot I could on street rubber with an open diff front wheel drive. Anyway, I pulled out a little ahead of my other Prelude friends and broke into the 14s. I finally got the car to 14.54@96.16mph with a 2.0 sixty foot and backed it up with a nearly identical run.
My friends and people on the Prelude Yahoogroup were all fighting to hit 14.99s, and I was a member of a well known Honda web board. Well, some guy in Jersey, who remains an online buddy to this day, ran a 14.6x@94.x in his 1999 Civic Si. He was making claims that his car was a Prelude destroyer, and page after page of useless chest beating over slow-as-***** cars ensued.
We went way too deep into the data, and started comparing several other cars from our tracks. It turned out that his track just flat out had quicker AND faster cars, and I wanted to know why. I'm sure you all know where this is going, but it ended up being track conditions. His timeslip came from racing at E-town at dang near sea level in a cool 40 degree night in Jersey. My best timeslip came from racing in the Southeast at 80 degrees and like 95% humidity.
The BS stops at the track where the rubber meets the road, but if you aren't at the same track in the same conditions, there's more BS to contend with.
This is an apt comparison for dynos. Thank goodness for correction factors, because if you added mods on certain hotter days, it could look like you lost a ton of power.
So imagine your actual (uncorrected) power as sine wave, going up and down. You're right near zero on a comfortable spring of fall day, you're car feels ***** to the wall fast in the dead of winter, and it feels lethargic and sluggish in the heart of summer. Super low humidity and cold, dense air have a profound effect on horsepower.
I think we forget about this often, because the seasons change very slowly, and its kind of like bring an egg to a very slow boil- the change is so subtle that you don't notice it. Now this is not a terribly big deal, because the other cars on track with you are all ingesting the same air your car is.
So where's the point in all of this? The point is that the horsepower sine wave for turbocharged cars realize higher highs and lower lows. You can minimize those lows a bit with an efficient intercooler. You can minimize potentially dangerous highs with a stable boost control method that does not spike badly in the cold. I've seen many engines lost in DSMs, Evos, and Subies from the owner with an unreliable boost control method going WOT in twenty degree weather only to achieve 28psi in fifth gear on 93 octane in a car that was tuned for 23psi.
My point of this thread is to open up a discussion of how we can help each other think of how to maximize the safety of the highs and improve the power of the lows.
Happy motoring.
Jun 27, 2008, 04:30 PM
#6
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My answer to this quiz is very simple.. Move to South Fl where it's always 85 degrees, even in the winter, tune ur car, and leave it alone!!
The we can all have the worlds largest BBQ with tons of beer and women!!
The we can all have the worlds largest BBQ with tons of beer and women!!
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Jun 27, 2008, 05:51 PM
#9
This reminds me - it's too bad the EMS only has a barometric pressure dependant adjustment for boost control and not an air temp dependant adjustment 
I guess with a well set up air temp correction for fuel and ignition, the aftermarket ECU guys have it pretty safe. Does the stock ECU have provisions for that? (I stopped using ECUflash like 2 years ago)
I guess with a well set up air temp correction for fuel and ignition, the aftermarket ECU guys have it pretty safe. Does the stock ECU have provisions for that? (I stopped using ECUflash like 2 years ago)
Jun 27, 2008, 06:18 PM
#10
This reminds me - it's too bad the EMS only has a barometric pressure dependant adjustment for boost control and not an air temp dependant adjustment
I guess with a well set up air temp correction for fuel and ignition, the aftermarket ECU guys have it pretty safe. Does the stock ECU have provisions for that? (I stopped using ECUflash like 2 years ago)
I guess with a well set up air temp correction for fuel and ignition, the aftermarket ECU guys have it pretty safe. Does the stock ECU have provisions for that? (I stopped using ECUflash like 2 years ago)
For this hot weather, I am thinking bigger intercooler.
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