Well this is weird...
Legacy TMS Member
Joined: January 6, 2006
Posts: 14,053
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From: Bay Area, CA
Shelby GT350 Member
Joined: July 16, 2011
Posts: 2,040
Likes: 52
Yes I agree. They were going to have something "shortly" 6 days ago! This whole incident just confirms why I don't trust tunes from any company except Ford Racing, and I'm not even sure about them!
Management is currently reviewing & editing the response.
Our senior tuner gave us the explanation on Friday & what makes sense in his world ... isn't as easy to interpret if you don't have a tuning background.
Best Regards,
TJ
Shelby GT350 Member
Joined: July 16, 2011
Posts: 2,040
Likes: 52
Okay ... this is coming from Steeda's head tuner, who has many years of experience:
"What happened?" Well, based on the description, it sounded like the car stalled when it was clutched at 90 MPH. The car had stalled, and then it re-started after letting out on the clutch in 4th gear.
Ford started to incorporate a Ram Air scoop on these cars and they have been doing good job of listening to the aftermarket and installing parts in their cars that they saw selling in the aftermarket.
When tuners have a fan blowing on a cold air kit, it creates turbulence across the sensor. Ford dealt with this by the way they designed the stock airbox and using a nice square filter. If you notice, the stock design, the Ram Air scoop is pointed in such a way to actually fill (or pressurize) the box.
It does not blow directly on the filter itself. Mix that with the restrictive stock filter, and it quite literally "filters" the air... in more ways than one. Yes, it removes particulates from the air, but it also straightens and stabilizes the air as it passes through it.
Here is where the CAI comes into play ... the cold air kits add power by using less restrictive filter elements, increasing the diameter of the tubing, getting rid of the resonators (that is more so that they sound better) and changing flow paths to the throttle bodies.
Now I have done a lot of testing with different cold air kits on the 5.0, and I can tell you 100% without a doubt that the Steeda CAI has the best drivability of any of the aftermarket cold air kits that actually add HP. The engineers actually spent time trying to make sure that problems like this do not happen, but it is almost impossible without compromising performance.
Remember how Ford fixed the problem, they used a restrictive filter element to "filter" the air before it hit the sensor. That is the main part we want to, or NEED to replace in order to make power. We need a high flow element, and we need to increase the diameter of the tube. The problem with that is that as you increase the diameter of the tube, you slow down the velocity of the air as it flows through the CAI.
Velocity is your friend as far as drivability is concerned. There needs to be a good balance here so that the intake is not restrictive at WOT, but the velocity is still high enough to provide stable airflow signal at idle. You will notice that the Steeda CAI is not the largest out there. That is because it was engineered to see how big they needed to go to get the performance, and leave room to grow with other supporting mods (like long tubes, Boss intake, ect), but small enough so that issues like what you are describing are not common.
So here is what causes the issue and why it is normally not a concern. When you are driving a car, it uses air. It takes roughly 1#/min to make roughly 10HP.
Driving down the highway, you will use about 2-4#/min to maintain cruising speed (in a Mustang). At wide open throttle, a Coyote (with bolt ons) will ingest about 44-48#/min. At idle, the beautifully engineered Coyote will only use about .5#/min.
This is a wonderful thing, but it is also part of the problem. Someone mentioned that the GT500 does not have this problem, but the Coyote does. This is not entirely true. It is just not noticed because the GT500 has a parameter in the software called "Dashpot". For those of you who know carburetors, you will recognize the term. It is designed specifically to prevent stalling in old carbureted vehicles when making big changes in airflow.
In essence, it does not allow the throttle body to snap shut. It closes to a pre-determined limit, then slowly lowers itself to its resting idle.
Oddly enough though, I can tell you that the GT500 DOES also experience similar issues. I worked for quite a while with a customer that has a GT500 that I tuned (with brand x) that was complaining of what felt like a lean surge as he would go over an overpass.
The issue was that when he let off the throttle (going down the back side of the overpass), and the engine went close to idle airflow, the MAF signal became so turbulent that fueling was affected.
The Coyote uses an incredibly small amount of air to idle, so ANY turbulence through the CAI is going to cause idle issues but at 90 MPH, there is an incredible amount of air coming through that ram air scoop.
If it is enough to give just a .25#/min swing, it is going to be enough to throw off the fueling by 50%, and will probably be enough to cause the stall.
"What happened?" Well, based on the description, it sounded like the car stalled when it was clutched at 90 MPH. The car had stalled, and then it re-started after letting out on the clutch in 4th gear.
Ford started to incorporate a Ram Air scoop on these cars and they have been doing good job of listening to the aftermarket and installing parts in their cars that they saw selling in the aftermarket.
When tuners have a fan blowing on a cold air kit, it creates turbulence across the sensor. Ford dealt with this by the way they designed the stock airbox and using a nice square filter. If you notice, the stock design, the Ram Air scoop is pointed in such a way to actually fill (or pressurize) the box.
It does not blow directly on the filter itself. Mix that with the restrictive stock filter, and it quite literally "filters" the air... in more ways than one. Yes, it removes particulates from the air, but it also straightens and stabilizes the air as it passes through it.
Here is where the CAI comes into play ... the cold air kits add power by using less restrictive filter elements, increasing the diameter of the tubing, getting rid of the resonators (that is more so that they sound better) and changing flow paths to the throttle bodies.
Now I have done a lot of testing with different cold air kits on the 5.0, and I can tell you 100% without a doubt that the Steeda CAI has the best drivability of any of the aftermarket cold air kits that actually add HP. The engineers actually spent time trying to make sure that problems like this do not happen, but it is almost impossible without compromising performance.
Remember how Ford fixed the problem, they used a restrictive filter element to "filter" the air before it hit the sensor. That is the main part we want to, or NEED to replace in order to make power. We need a high flow element, and we need to increase the diameter of the tube. The problem with that is that as you increase the diameter of the tube, you slow down the velocity of the air as it flows through the CAI.
Velocity is your friend as far as drivability is concerned. There needs to be a good balance here so that the intake is not restrictive at WOT, but the velocity is still high enough to provide stable airflow signal at idle. You will notice that the Steeda CAI is not the largest out there. That is because it was engineered to see how big they needed to go to get the performance, and leave room to grow with other supporting mods (like long tubes, Boss intake, ect), but small enough so that issues like what you are describing are not common.
So here is what causes the issue and why it is normally not a concern. When you are driving a car, it uses air. It takes roughly 1#/min to make roughly 10HP.
Driving down the highway, you will use about 2-4#/min to maintain cruising speed (in a Mustang). At wide open throttle, a Coyote (with bolt ons) will ingest about 44-48#/min. At idle, the beautifully engineered Coyote will only use about .5#/min.
This is a wonderful thing, but it is also part of the problem. Someone mentioned that the GT500 does not have this problem, but the Coyote does. This is not entirely true. It is just not noticed because the GT500 has a parameter in the software called "Dashpot". For those of you who know carburetors, you will recognize the term. It is designed specifically to prevent stalling in old carbureted vehicles when making big changes in airflow.
In essence, it does not allow the throttle body to snap shut. It closes to a pre-determined limit, then slowly lowers itself to its resting idle.
Oddly enough though, I can tell you that the GT500 DOES also experience similar issues. I worked for quite a while with a customer that has a GT500 that I tuned (with brand x) that was complaining of what felt like a lean surge as he would go over an overpass.
The issue was that when he let off the throttle (going down the back side of the overpass), and the engine went close to idle airflow, the MAF signal became so turbulent that fueling was affected.
The Coyote uses an incredibly small amount of air to idle, so ANY turbulence through the CAI is going to cause idle issues but at 90 MPH, there is an incredible amount of air coming through that ram air scoop.
If it is enough to give just a .25#/min swing, it is going to be enough to throw off the fueling by 50%, and will probably be enough to cause the stall.
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