New 818 Configurations Windtunnel Tested

[longislandwrx]

yup bump for FFR updates.

[Sgt.Gator]

Bump! Any update on these side scoops?

[AZPete]

Gator, I'm not sure which side scoops you are asking about, but I have the FFR ducts that collect/direct air from the side vents in front of the rear wheels. I like them on my street 818C and they are available from FFR. Here's my thread about the ducts:

http://thefactoryfiveforum.com/showt...18+Intercooler

[Sgt.Gator]

Thanks Pete. Good read.
I'm trying to figure out if the fiberglass scoops I can order from FF are the same design as Jim tested in posts #24 and #25 in this thread.

[AZPete]

Gator, in #24 and #25 Jim seems to be showing that the knife-edge of the vent increased flow. In #41 he is thinking of a duct and in thread #131 he shows the duct they made for the inside of the side vent. The 2 ducts Jim sent to me to test look just like the fiberglass duct in thread #131. I believe those are the same ones now offered on the FFR web site. Also in this thread about aero, I forgot who, but someone said the 2 side vents have a combined area of 65 sq. in. which is about the same as the OE WRX hood scoop. So, pulling air from both side vents plus the roof vent, I'm getting lots of air to my A2A intercooler as shown in the dual IAT gauge. Again, however, my 818C is a street car so WOT is brief.

[Sgt.Gator]

Thanks Pete!

[alpine227]

My current thinking based on what we have seen testing intercoolers seems to be pointing to different solutions based on the intended use of the car. Testing the air to water systems on the track has shown that with no recovery time they tend to gradually increase in temps over the course of the longer runs, whereas on the street the recovery time at either cruising speeds or idle allows them to stay cooler than either the top mounts or relocated air-to air units still in the engine bay. The two W2W systems we tried were different in that one used a large reservoir and a medium sized cooler and exchanger and the later system used a bigger cooler and a full sized radiator as the heat exchanger with no reservoir. The second system worked better and was overall lighter than the one using the extra tank.

For air to air I still think the top mount is viable for stock and mild builds, on both street and race cars, and that is where we concentrated our street car efforts in the tunnel trying to find the best spots to pull and from and exit air to. The plan going forward for ducting to the top mounts is to use four inlets to feed the intercooler. The two side inlets are effective if they are cut out correctly (the cutout shape made a HUGE difference which was something we missed in our first trip to the tunnel) and either the decklid vents or the roof scoop ducts for the other two depending on which model it is.

During our track testing we also tried several different very large scoops feeding the intercooler from in between the humps and this was not as successful. Even with a large top mount (Turbo XS) the temps were not as low as we would like them to be and the drag/reduced downforce was not good at all. Airflow in that area is just very turbulent and the cockpit itself is a low pressure so air will actually flow backwards into it.

As far as air exit goes the best place is the lower section of the car, the upper vents still allow air to exit but the flow is much slower and more chaotic. The rear trunklid vent is somewhat variable, with the spoiler in place you get air flowing in, but with the wing in place there is not much flow through that vent at all. I still think the vent is useful, particularly for escaping heat when the car is sitting still, but it isn't a good place to get reliable air entry or exit from. Cutting additional vents on either side of the low vent seems to make the most sense for someone needing to get additional air out of the engine bay.

The front mount in the race car is really just going to come down to testing turbo lag. This setup will only be a real possibility for R models as the tubes run through the top of the doors, but the plumbing was actually pretty straightforward and the amount of tube relative to a WRX with a front mount is not that different (maybe 50% more but not 2 or 3 times as much). We stayed with a fairly small inlet tube to try and keep the overall volume down but we still have testing to do to see if this really is the best solution for big power track only cars.

Also on the R, the windscreen makes a big difference, improves drag, downforce, and cooling and running without it does not improve flow into the rear decklid area.

Good afternoon, have you folks done any testing on sidemount configurations?

[fastzrex]

Gator, in #24 and #25 Jim seems to be showing that the knife-edge of the vent increased flow. In #41 he is thinking of a duct and in thread #131 he shows the duct they made for the inside of the side vent. The 2 ducts Jim sent to me to test look just like the fiberglass duct in thread #131. I believe those are the same ones now offered on the FFR web site. Also in this thread about aero, I forgot who, but someone said the 2 side vents have a combined area of 65 sq. in. which is about the same as the OE WRX hood scoop. So, pulling air from both side vents plus the roof vent, I'm getting lots of air to my A2A intercooler as shown in the dual IAT gauge. Again, however, my 818C is a street car so WOT is brief.

Hey Pete, what do you use for 'cold air' source to the inlet for the engine? I was anticipating use of the roof duct for inlet air and the side scoops (with FF inserts) for oil cooler/compartment cooling.

[AZPete]

Mark, I'm still drawing intake air from the duct inside the right side vent. This right-side vent also feeds air through a 3-inch flex tube to the intercooler plenum, however. Most of the time cool air is sent to the intercooler and to the engine intake filter, but at WOT the engine sucks so much more air that it causes the flow in the tube to the intercooler to reverse, thus sucking air from the intercooler. I haven't changed it yet because I don't know what's best. Plus, this is a street car with only occasional WOT, so I wonder how bad this is.

I think the roof ducts would work well for your engine intake since the OE intake is 3-inch and the roof ducts are two 3-inch ducts, fed by the roof vent of (?)sq.in. I assume you have an A2W intercooler.

See Post #3 in this thread:
http://thefactoryfiveforum.com/showt...rcooler-Plenum

[fastzrex]

Mark, I'm still drawing intake air from the duct inside the right side vent. This right-side vent also feeds air through a 3-inch flex tube to the intercooler plenum, however. Most of the time cool air is sent to the intercooler and to the engine intake filter, but at WOT the engine sucks so much more air that it causes the flow in the tube to the intercooler to reverse, thus sucking air from the intercooler. I haven't changed it yet because I don't know what's best. Plus, this is a street car with only occasional WOT, so I wonder how bad this is.

I think the roof ducts would work well for your engine intake since the OE intake is 3-inch and the roof ducts are two 3-inch ducts, fed by the roof vent of (?)sq.in. I assume you have an A2W intercooler.

See Post #3 in this thread:
http://thefactoryfiveforum.com/showt...rcooler-Plenum

Thanks again, Pete, for your input. I want to run A2A IC in the stock position, just trying to reduce complexity where possible (and weight). Like you, this is a primarily a street car, and WOT will be a rarity for more than a few seconds. Having a single plenum is attractive as it also reduces complexity; I have followed your experiments in airflow and it is interesting that the engine sucks so much air when 'on full song'.

Are you running an oil cooler? How are you ducting air to it?

And one more time, thanks for the A/C install documents. It removed a lot of routing/location mysteries!

[AZPete]

Mark, I'm not running an oil cooler other than the stock cooler/heater/whatever at the filter. Thousands of WRXs seem to be fine driving streets in lots of conditions, so I don't know why I would need any other oil cooler.

I was stupid to install 2 fans in my intercooler plenum, and will remove them. I put them in thinking I'd need them to move air when stopped or in stop-&-go traffic. But, at those times, the turbo is not heating the intake air and the engine is sucking ambient air through the intercooler, so having the fans push ambient air is useless. When my 818C is moving, I've got plenty of ambient air coming through the roof and side ducts to cool the intercooler.

Regarding appearance, I like the suggestion by ben1272. He said to make 2 narrow plenums, each leading from the roof ducts back to the intercooler. They would look sort of like the intakes on bigger engines. Good idea for another project.

[frankc5r]

Pete,

Think u are headed in right direction.
I have talked to turbo experts who
can prove with math/modeling/tests
that you only need about 30 mph air
speed for full cooling on air/air ic.
Of course higher is better especially for racing but
30 works for a strong street setup.

[fastzrex]

Mark, I'm not running an oil cooler other than the stock cooler/heater/whatever at the filter. Thousands of WRXs seem to be fine driving streets in lots of conditions, so I don't know why I would need any other oil cooler.

I was stupid to install 2 fans in my intercooler plenum, and will remove them. I put them in thinking I'd need them to move air when stopped or in stop-&-go traffic. But, at those times, the turbo is not heating the intake air and the engine is sucking ambient air through the intercooler, so having the fans push ambient air is useless. When my 818C is moving, I've got plenty of ambient air coming through the roof and side ducts to cool the intercooler.

Regarding appearance, I like the suggestion by ben1272. He said to make 2 narrow plenums, each leading from the roof ducts back to the intercooler. They would look sort of like the intakes on bigger engines. Good idea for another project.

Thank Pete for your input. I will monitor the oil temp in the sump and see what happens. And thanks for the update on the plenum fans, with all your experimental data, you are helping us all about air through the A2A IC on top.

You talk about two narrow plenums from the roofs ducts, and can not visualize the result. I am getting close to first start and then will need to manufacture plenums.

[Sgt.Gator]

I'm bumping this 5 year old thread because there are a lot of new builders who have never seen it and can benefit from what's in here.