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Old 09-12-2006, 04:58 PM   #1
MPREZYA
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Default Project '06 WRX Part 2's missing dynographs...

Okay here's a long overdue couple of dynographs that were referenced in the second article in the magazine but didn't make it in but before that allow me to refresh people about the MAHA 3000 LPS dyno:


Quote:
For those unfamiliar with dynamometers, there are two basic types of dyno's:


The first being the Engine Stand dyno, which requires bolting a complete engine to a horizontal engine stand and measuring how much resistance it can overcome or how much work (measured in torque or horsepower) it can produce. While this is the most exact measurement possible, it means removing the engine from the vehicle and after testing, reinstalling it again. Obviously the downtime and expense do not make this a practical option for most owners. The advantages are the engine is being tested in a controlled environment and there are no driveline loses to compensate for in calculating the engines output. However, for development work where many options are to be tested before the engine goes into the vehicle, it can be an invaluable tool.

The second type of dyno is a chassis dyno, which merely requires driving the vehicle onto the rollers and strapping the vehicle down, so it doesn't run off the dyno, and then measuring the amount of resistance/work it can overcome.

There are 2 main obstacles when using a chassis dyno, the first is airflow. Most fans used on chassis dynamometers are taken from contractor suppliers and struggle to simulate a 10-20 MPH road speed, which is equivalent to your doctor asking you to submit to a fitness test while in a sauna. Needless to say, your score will be low. The MAHA approved custom built, "AIR 8" fan on the AMS MAHA dyno, flows over 80,000 CFM (cubic feet/minute) or a road speed of 60-70mph!

The second obstacle, is that most dyno's only measure "wheel horsepower" - that is the power that isn't sapped away by everything located after the clutch (transmission, differentials, driveshaft, axles, even the wheels and tires themselves!). And since wheel
horsepower readings are dependent on the temperature of your transmission and differential oils (cold oil is like molasses and warm is like water, warm oil eats less power) and tire temperature (cold tires offer less resistance than warm sticky tires) so driveline loss can be inconsistent or as an expert referred to it "a moving target"!

Many people simply add back a "guesstimate" of the parasitic drag of these components anywhere from 10-20% for FWD or RWD cars and 25-40% for AWD or 4WD cars. The final flywheel numbers are only as accurate as the tuner's best guess.

The inherent beauty of a dyno system like the MAHA LPS 3000, is that after it has measured the wheel horsepower, it measures the resistance of the entire drive train from the clutch to the tires by letting the car "coast" down while in gear, so instead of dynoing a vehicle with a reported 200 horsepower and measuring only 150HP at the wheel, and assuming that 50hp was eaten up by the drag of the drive train and wheels The LPS 3000 actually measures the drag loss during the coast down phase. In fact, if the drag loss is only 30hp , you know beyond a "guesstimate" that your engine only made 180hp, or if the drag was 50hp, you will know exactly how much power your vehicle is really making. However, with a drag measurement you can rest assured that you have isolated only the engine's horsepower and not the engine's power minus an unknown amount of drag. The system also corrects for environmental conditions such as humidity, air density, and temperature.

Now onto the missing dynographs:




This right here shows the bad timing dip we had from a bad tank of gas which was seen throughout the @20 dyno runs during testing that day. You can see where the OL/CL change over is and that is not what affects our timing. We did various datalogging and troubleshooting to verify it wasn't the intake or anything else causing the issue. The graphs would show gains up to where the timing event occurred then would follow the baseline graph we had set to the rev limiter.



This right here shows a side by side comparison of the stock filter, STi drop in filter and aFe intake on the MAHA dyno. Unfortuneatly the seperation of all the dyno's colors didn't come out well but the aFe performed well with the STi drop in adding alittle bit more power over the stock baseline. The numbers at the bottom of the graph are for the aFe. All testing was done with the SPT exhaust on the car and everything else stock. The ECU was reset after each intake and ran 3 times each.



These numbers are "crank" horsepower not wheel horse power. Also the conversion factor for Nm to lb-ft is .73nm = 1lb/ft .


I will post more graphs as I sort through them all.
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Old 09-13-2006, 06:34 PM   #2
Kostamojen
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20ft-lb loss at 2100 rpms? Wow, didnt expect that...
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Old 10-13-2006, 07:43 AM   #3
pucho
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Quick question: I keep reading about issues with using intakes on WRX's but it seems this information is based on older models (02+) Is this the same for the 06's or do the changes to the 06 negate these issues, have you seen any negative effects using the intake. Thanks for any info you can pass along.
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Old 10-13-2006, 04:29 PM   #4
MPREZYA
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Default

So far I've noticed no ill effects with the intakes I've tested. It's still reccommended you get tuned for one but Dan@harmanmotive was quite suprised he had zero issues when tuning the car last with the aFe (usually mild maf issues or idle with some intakes.).

Most the intakes on the market now are much better developed and designed then the first ones developed back when the WRX debuted. Plenty of great ones to choose from (aFe, injen, prodrive, spt, etc).
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