Some observations from the past year.

1. Ram air works. We saw this some at Nationals with Dave Dirks setup. Based on this, I tested this at Road America, a 4 mile track that puts us in 5th gear 3 times a lap, with speeds up around 120 MPH. To optimize the effect I ran a 4" duct from a high pressure area (left fog light), directly to the AFM. For the test, only a window screen was used for a filter, and compared it to my baseline cold air intake (an efficient set up that had dyno'd 137HP/141TQ on a previous car). Leaving the filter on or off that set up made no difference on the dyno. The TM data is fascinating. low speed acceleration is no different, but above about 90 MPH, the curves separate fairly dramaticaly, as the ram air effect starts to show up. It was worth about 4MPH at the end of the straight. Look at the graph below. The green is the ram air. There are 2 laps from my car without ram air (red), and 2 laps from another car with very similar HP, but no ram air. All the "control laps are similar, but the ram air test lap stands out. Conditions were similar throughout.


Larger version here: sterlingdoc.smugmug.com/Other/Nationals-...7758783_2GstHxP-O-LB

2. Most of the motors at Nationals were in the low/mid 130's in HP, and similar to a bit more torque. The strongest low compression piston we saw made 134HP, and 141TQ, with a head shaved near the minimums. This was actually the most TQ recorded by any motor, low, or high compression. The best high compression motors made around 137-139 HP, and similar TQ. Not all of the cars made it on the dyno, however. There was a suggestion that the '88 DME helped a high compression motor vs. a mid-year DME, but this was only one dyno, and not verified.

3. Milledge heads are very carefully built, standard heads. The only Milledge-head motor to make it to the dyno made competitive HP, but not the most HP, and this was reflected in its on track performance. This is not a class killing development.

4. It's good to be back on Toyos again!

5. 944 Spec Drivers are the best - Nationals proved that. 4 days of intense racing, often in the rain, that caused some classes to have more than 50% of cars out due to contact, saw NO car to car damage, and only one car damaged by an off track excursion (and still finished). Great stuff!

I tend not to read to much into the ram-air effect. Using 2 different cars, even if they are similar, is not much of a test. Different aero could account for this as with different weight cars. Using a window screen against some type of filter could also make this difference. Tests like this need to be made on the same car, same day, same temp. conditions and so on. Yes you have data but it is skewed.

Correct if I'm wrong but I read that differently. I think the test was done on two separate cars with and without ram air on BOTH cars.

Do you have pictures of the setup? Was the ram air directly into the AFM or into the direction of a cone filter? I'd be interested to see the setup.

Ken, yes there are variables, but I've made some effort to limit them. My day job involves interpreting a lot of studies, and expalinaing a away a lot of trash on the internet that comes from poorly done studies, so I'm pretty familiar with what makes a good test. Here's how I attempted to get as good of data as possible:

1. I used my own car as a baseline, so no aero variables there. Comparing it to Angel's car just further validated the baseline. Angel's curve is very similar to mine in acceleration, but my main comparison, is my own car, without ram air. With the enduro, we got a lot of laps to compare, and the acceleration differences at speed are pretty repeatable.

2. I eliminated the air filter variable by not using one in either scenario (baseline or test). I would not recommend this for long, and there was also no difference detectable difference with running a cone filter on my baseline cold air setup with and without a flter (both on track and on the dyno).

3. Also speaking to the ram air effect is where the difference happens. More basline HP, changes in air density or temp, etc. should make more power everywhere, not just at high speed.

There are some things that I did not control for:
1. Temperature
2. Fuel Loads
3. Barometric pressure

I did test each setup at varying times during the day, and saw little difference through the day. Temps were pretty steady, as was the weather, so those variations would seem minimal. A better test yet would have been both setups during the same session, but I could not get things changed over that quickly.

The effect seems too impressive, and repeatable, to be due to chance. Also, where the effect happens seems to fit the ram air hypothesis. We saw similar outcomes with Dirks' setup at Nationals. More testing would make this more solid yet, of course, but it's enough to be very interesting with what we have. Also different setups may vary. My setup was desinged to maximize the effect, to make any difference the most obvious, and is not practical for long term use. Some sort of in line (hopefully low restriction) filter would be needed, or plumbing the stock airbox, as Dirks and others have done. Rain can also be an issue here.

What to do about this is another matter. It's pretty cheap to plumb a hose from the foglight opening to the stock airbox, and that seems effective. Ram air could be "outlawed", but it may be hard to define a cold air setup from a ram air one, so we'd probably have to mandate stock airboxes, which could be more expensive than a simple, and effect ram air setup. I'm open to thoughts/discussion on this.

944Racer72 wrote:


Almost - we used two cars as the baseline, and only one to test the ram air (one of the two used for a baseline).

I don't have any good pics, but I can explain it. I used 4" smooth, rigid dryer ducting. Each section has 4 parts that can be rotated to go from straight, to a 90 degree bend, depending on how many of the 4 sections you rotate. This was plumbed directly from the foglight opening, to the AFM itself, nothing in between. A window screen cover the foglight opening, routing just in front of the alternator, and was the only filtration for purpsoses of this test (agian not recommended long term)

A 4" duct is a tight fit, but maximizes the effect. Once you neck it down, velocity incrases, but pressure decreases (I think this is Bernoulli's effect, but I'm not an engineer). You want maximal pressure (not neccesarily velocity) at the AFM. I rapidly pulling out the ram air duct to go back to baseline, I destroyed part of it, so pics now would be limited.

Sterling Doc wrote:


Seems to me that you opened this up last year with the addition to rules highlighted in red...

12.2 Air Filter
Any air filter or filtration system may be used. Air may be ducted to the air flow meter from any location inside or under the car including the fog light buckets.

16.1.1 The backing of fog light buckets may be removed
for cooling purposes including, but not limited to oil cooling and brake cooling, and for engine air intake.


Seems to me some people are looking for more power, or an advantage. I say take the items marked in red out. 16.1.1 should read....The backing of fog light buckets may be removed for oil cooling and or brake cooling only.