Air induction kits are alwys a tricky thing to dyno. Usually, that is because they are designed for a moving car and you arenít going anywhere on a dyno. So, many times it is difficult to tell if an induction system helped you just by putting your car on the drums. In this case we have a 1997 Ford Mustang Cobra with a MAC cat-back exhaust and a 2-cat gutted h-pipe (from the previous article). Our baseline run yielded 257 rear wheel horse power and 260 lb-ft of torque. Then we threw on the MAC induction and got, wait a minute, what? 250 HP, we lost power! No way, this sytem removes the stock air box and puts the air filter into the wheel well which is much cooler than the engine bay, plus it can suck in air from all around it now. Whatís going on?
We thought about this for a while and then started retracing our steps. We went through the installation, everything ok there. No error codes from the car. The dyno was working fine for all the other runs that day. Wait a second, the car was sitting in the sun for the last two hours. But so what, once we started the car the engine temp was fine once the coolant kicked in. The only difference in configuration was the induction, so that had to be where the problem was. And it was. When the car was sitting in the sun, the chrome pipe that the kit uses got hot. I assume Mac used a chrome pipe for looks, but what is the point if performance is degraded? So even though more air was coming into the engine, it was hot air which lowered the power output. Normally, the car would be moving and the chrome would be cooled. In this case it wasnít. So, we put the car in the shade for a while and then touched the pipe to make sure it was cool.
Next dyno run, 263 hp and 260 trq. Thatís more like it. So, the car gained about 6hp which makes sense. Again, there will be no way of telling what it gives when you are moving at 70 mph unless you have a wind tunnel somewhere. Some people use a fan right at the induction opening, but that is tricky. There is really no way of telling what kind of speed you are actually simulating so the result doesnít mean anything.
Letís look at the curves. As you can see, you only start gaining around 4000 rpm. Before that there is really no difference. So, donít expect any seat of the pants improvement. If you have thrown in a high rear end ratio (like this car) and keep your car at the higher rpms then this is a nice little boost. Plus, when the car is moving and you are getting more air you may get a little more.
There are a couple of things to remember from this modification. First, we gained about 6 hp on the top end which is acceptable for $157. Second, temperature can affect other things besides the engine. Third, if you have done this mod keep in mind that you may be loosing hp if your car was not in a cool place like in the sun in the middle of a parking lot. So be careful if you race someone coming out of the lot!
We will continue to examine this induction system (air filter used, 90 deg turn that the pipe makes etc...), so check back for updates to this article.