- One $50 carpet dryer fan 6-8 feet in front of the car, not even angled at the engine bay or set on top of the intercooler.
- No door or window in front of the dyno = no fresh air. The room will just keep getting hotter the longer the car is running.
- This car has a GrimmSpeed TMIC. One of the main benefits of the GS TMIC is the well built intercooler shroud that is sealed against the intercooler to provide maximum airflow directly through the core. Having the hood open and a fan that blows 1 mph (I’ve tested with my anemometer) completely degrades the intercooler’s performance and does not replicate the airflow the car will see on the street.
- This customer had my e-tune on the car for 2 years and never had a DAM drop or excessive knock. It only took 3 pulls on this dyno for the DAM to drop and throw a -8 FeedBack Knock count.
This customer had my e-tune on the car for 2 years and never had a DAM drop or excessive knock. It only took 3 pulls on this dyno for the DAM to drop and throw a -8 FeedBack Knock count.
Try doing this with a $50 carpet dryer fan.
How do companies come to the conclusion that not having an intake box is better than using a fully enclosed box? From dyno testing the intake setups on a dyno with the hood open and insufficient airflow.
1) INCORRECT TEMPERATURES BECAUSE HOT AIR RISES
- When the car is on the dyno with the hood open and no box around the intake, the hot air rises out of the engine bay and doesn’t get sucked into the intake. So the intake temperature data looks good.
- The coolant temp, oil temp, intake temp, overall engine bay temp, amount of heat soak, etc. are all incorrect if the car is dyno'd with the hood open and the amount of airflow is not even a close representation of the airflow on the street.
2) NO EFFECT FROM RADIATOR FANS
- When dyno tuning a car with the hood open and the radiator fans turn on, all that hot engine bay air just hits the front of the engine and goes straight up and out of the engine bay since the hood is open.
- However, when the hood is closed and the fans turn on, all of the hot engine bay air gets sucked directly into a no-box intake, which is one of the reasons they have high intake temperatures.
- Also, the airflow from the radiator fans can effect the readings of Mass Air Flow (MAF) sensors when they are one or off. Without a box around the intake, the airflow changes from the radiator fans turning on can cause the MAF to change so much that the AFR goes rich and causes the car to stumble or even stall.
3) FULLY ENCLOSED BOX + NO AIRFLOW = SUPER HOT INTAKE TEMPS
- Testing an intake with a box on a dyno with hood open and no airflow causes artificially increased intake air temps because the hot air can’t escape upward out of the hood like it can without a box.
- No fresh air is being forced into the ram air scoop like it would be on the street. This causes stagnant air inside the intake box, which will heat soak and increase in temp over time.
- Lack of airflow produces incorrect data due to improper test conditions.
4) DYNO NUMBERS WITH THE HOOD OPEN ARE INCORRECT & MISLEADING
- There are Intake air temp compensation tables in the ECU for boost, timing and fueling.
- The intake air temp compensations effect how the car runs and how much power it makes.
- If the airflow through the intake, radiator, engine bay, etc. is incorrect, then the temperature of the system will be incorrect, which means the intake air temp compensations will be used incorrectly.
- An intake without a box + hood open + low airflow produces artificially low intake temps, which causes the incorrect timing compensation to be used. Lower intake temp = less timing being removed = higher horsepower reading. ** THIS IS THE EXACT OPPOSITE OF HOW IT IS ON THE STREET **
- An intake with a complete box + hood open + low airflow produces artificially high intake temps, which causes the incorrect timing compensation to be used. Higher intake temp = more timing being removed = lower horsepower reading. ** THIS IS THE EXACT OPPOSITE OF HOW IT IS ON THE STREET **
- By testing various intake setups with the hood open, it causes the intake air temp data to completely wrong and essentially backwards to the actual temperature data on the street.
5) INCORRECT BOOST CONTROL
- The incorrect temp data causes the intake air temp target boost compensation, wastegate duty cycle compensation and all other temp based boost control settings to work incorrectly.
6) CONCLUSION
- The whole point of a dyno is to simulate a car driving on the street.
- The less accurate the simulation is, the less accurate the data is.
- Hood open = poor testing setup & inaccurate data
- Carpet dryer fan = poor airflow & inaccurate data
- Many Subarus have top mount intercoolers. Testing a TMIC car with the hood open completely removes the hood scoop, hood shroud and heat soak from the equation.
- Most shops will downplay the effect of having the hood open and carpet dryer fans.
- Most shops have poor setups and poor airflow.
- To me this is a very black and white issue. Any data gathered from a dyno test with the hood open is meaningless because the car will never be driving down the street in that configuration.
- Overall poor dyno setups and testing procedures with the hood open, insufficient fans/airflow, completely wrong under hood aerodynamics and completely wrong manifold temps lead to incorrect data which leads to incorrect conclusions which leads to a poorly designed part which leads to customers actually making less power from installing the part….higher intake air temperatures = more knock = less power and more engine wear.
