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Discussion Starter · #1 ·
I'm considering the possibility of adding aero to my all ready heavily modified track car. I want to make clear that my primary objective is to improve air flow for cooling purposes by adding a splitter. I understand that adding the splitter will also require a wing in order to keep the car balanced. I am not planning on racing so my options are not limited by what is mandated, nor do I want or need aero that aggressive. Additional downforce is a secondary priority.
I am particularly interested in the opinions of those who have experience with OEM aero on 911 models vs. aftermarket aero in terms of performance and quality of build. Since we have never had (until the GT4 came along) significant aero on our Caymans, I have to look to those who have experience with this on other cars.

Option 1: Wait until the GT4 bumper and wing are available and install those. Bumper already comes with the center vent. (assuming everything fits of course)
Pros: Very well engineered, made for the car, and they look good.
Cons: Probably very expensive, and may have to wait awhile until available.

Option 2: Getty is coming out soon with a street/track splitter for the 981. Also a new RS wing. Add the GT3 bumper vent with ducting.
Pros: Likely far cheaper than OEM and available sooner.
Cons: Don't know of any. Performance vs. OEM? Quality of build?

One more thing: Since the bumper is coming off for either option, I am curious if anyone out there has removed the A/C condensers? Did you detect any difference in coolant temperatures?

The goal is to be as kind to my car as possible in terms of heat management. I have already added the diff. cooler and I think (assume) that oil to coolant exchangers are very efficient in dumping heat. The issue is, can the car's cooling system get rid of all that heat. I have been told by a couple of trusted techs in my town, that a good splitter and a properly vented center radiator will be a big help in the cooling department.
Now I just have to decide which way to go.
Thanks in advance for your input.
 

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Regardless of how it is set up I would say the center radiator would be the first big change. I would install one with the open center grill in the stock CS bumper and see how that changes things. Once that is done, I would think the GT4 bumper would be the way to go. Then again, if it is a dedicated track car, you may be able to go lower and more aggressive than the GT4 which was built around street minded compromise.
 

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Discussion Starter · #3 ·
I should have clarified that I already have the center radiator installed, but not the bumper venting.
It also appears that the GT4 bumper/splitter have been modified in order to increase air capture. I don't know if the openings are larger than the 981, or if it just looks that way because of the way the openings are framed.
The GT4 bumper certainly looks great as does the wing. I wonder though what kind of reinforcement might be required in order to attach the OEM wing to rear hatch.?
 

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I wonder if the GT4 openings have increased to balance out the reduction in airflow due to the mesh.

I should have clarified that I already have the center radiator installed, but not the bumper venting.
It also appears that the GT4 bumper/splitter have been modified in order to increase air capture. I don't know if the openings are larger than the 981, or if it just looks that way because of the way the openings are framed.
The GT4 bumper certainly looks great as does the wing. I wonder though what kind of reinforcement might be required in order to attach the OEM wing to rear hatch.?
 

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Discussion Starter · #5 ·
I assume that the mesh is rounded and not flat. If that is the case, it will have very little effect on air flow. It's the flat edges that restrict air flow. I'm not an engineer but I spent my youth growing up on a farm in Canada and have lots of experience putting up snow fences and windbreaks for cattle. Flat boards spaced about 30% of the width of the board apart, will almost completely keep out the wind. That is why I would never consider buying flat mesh for the grille, especially for tracking the car.
 

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The Aero on the GT4 was probably a compromise between drag/downforce and the ability to use the car on regular roads.

FWIW Getty Design was the shop that manufactured the splitter/wing for the 987.2 Interseries cars. Pretty good products for the price. They have been making parts for various 911's for years, prior to them getting into the Cayman/Boxster scene.

I have used them on my 987.2 CR and if I were building a 981 based track car I would not hesitate in using their products.

Folks who have gone with their bigger wing setup, go with their kit that allows the downforce load been generated by the wing to be transferred directly to the chassis via the uprights.
(The attached picture is Mooty's Cayman R that was been track prepped last year)

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As far as the opening for the radiators been larger on the GT4, folks have to remember that the car was designed as a track car from the ground up and that it has a 3.8L engine.

Cooling requirements for an engine that would be pushed hard almost all the time would be substantially greater than a stock 3.4L car for street use. Also keep in mind that the GTS also has much larger radiator openings relative to a regular 981S, part of that is probably due to the engine mapping been different allowing the 3.4L engine on the GTS to produce more power. Getting rid of those round lights (fog lights) on the 981S in the radiator area helps with airflow as well.
 

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Discussion Starter · #7 ·
Thanks 2slow2speed for that feedback. My car is street legal but only sees the street for driving to the track. It gets pushed pretty hard on the track, but I don't intend to start racing it. I wondered about the GTS bumper but it could probably still use a bit more splitter and it's lacking the center vent which I think makes the center radiator much more effective for the use I am giving it.
 

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BTW: The high elevation in CO with the thinner air probably is not helping with cooling on your car. At the same time I would have thought that your car would be down on power about 10-15% relative to sea level so the engine should not be generating that much heat.

Given the many mods that your car has, are you sure that your engine is not running lean and thus generating more heat than usual?

On the 987's the center radiator requires openings in the bottom of the front bumper. As Krokodril mentioned many moons ago, in order to use a top vent, a different part is needed to change the orientation of the air to be vented.

I have not looked at the PET catalog for the 981's, so not sure about differences in mounting brackets, shrouds, etc. Perhaps you could follow a similar approach.

Not sure how much time John at BGB has these days, he used to provide a wealth of information in the past, and helped companies like RSS develop parts for those folks who track their cars. Send him an email or call him up, maybe he can point you to the right direction or he might already have the needed parts to help with the cooling needs that you are looking for.
 

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Discussion Starter · #9 ·
BTW: The high elevation in CO with the thinner air probably is not helping with cooling on your car. At the same time I would have thought that your car would be down on power about 10-15% relative to sea level so the engine should not be generating that much heat.

Given the many mods that your car has, are you sure that your engine is not running lean and thus generating more heat than usual?

Possibly

On the 987's the center radiator requires openings in the bottom of the front bumper. As Krokodril mentioned many moons ago, in order to use a top vent, a different part is needed to change the orientation of the air to be vented.
I plan on adding the ducting if I install the venting.

I have not looked at the PET catalog for the 981's, so not sure about differences in mounting brackets, shrouds, etc. Perhaps you could follow a similar approach.

Not sure how much time John at BGB has these days, he used to provide a wealth of information in the past, and helped companies like RSS develop parts for those folks who track their cars. Send him an email or call him up, maybe he can point you to the right direction or he might already have the needed parts to help with the cooling needs that you are looking for.
I know John but am reluctant to ask him for information that his customers have to pay for. John is real good about providing information on this forum and others.
 

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if you look at the center radiator kit.. there is not much way to vent up.. the radiator actually seats in a 15 degree angle.. , the bottom to being wider.. hope that make sense? i got some pics in the other thread..

or you need to mount the mounting bracket upside down..but now you have a hose dilema.

just my 2 cents..
 

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Discussion Starter · #13 ·
I already have the center radiator installed. I know somebody with the R who installed the vent and had to do a little modification in order to install the duct that directs the air out the top. I would guess the 981 might require the same kind of treatment when installing the vent.
 

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Why are you so worried about the cooling? If you have the Dif cooler already then you shouldn't worry about more. The primary function of Aero is not to add cooling but to add downforce. If you don't plan to race, but maybe a few track events, then what is the advantage of all this cooling. I'd hate for you to spend 5 thousand or more on some modifications that in reality, you don't need.

these cars are very good at handling 20 minute sessions on a track, endurance racing....okay you'd need to modify your car for that...but just for a couple of DE events, its not necessary.

I've spent many hours on track with all kinds of stock sports cars, all of them do alright with short bursts on the track. All this really comes down to how you want to use the car.
 

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Discussion Starter · #15 ·
Why are you so worried about the cooling? If you have the Dif cooler already then you shouldn't worry about more. Maybe get a third radiator mod. The primary function of Aero is not to add cooling but to add downforce. If you don't plan to race, but maybe a few track events, then what is the advantage of all this cooling. I'd hate for you to spend 5 thousand or more on some modifications that in reality, you don't need.
Not worried but here is why I am exploring my options. I don't race but I spend a lot of time on the track. 2500+ track miles in 2014. My car is fast. I track at high altitude which is always a challenge. I have PDK which adds to the challenge. I agree that the primary reason for aero is for downforce, but we also know that splitters significantly increase airflow thru the radiators.
I hope you're opinion is correct and that I don't need more cooling but the main reason I posted this was to get feedback from others who have traveled this road.
BTW, if you read my earlier post you would know I already had the center radiator.
 

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Well, if you already have the center radiator mod, and the dif cooler, are you still overheating? still having heating issues? if anything I would imagine extra brake ducts would be necessary for a lot of track time.

I think a simple splitter (Carbon fiber panel cut to the shape of the bumper but extended by an inch or 2) might be all you need. No need to change the entire bumper. I mean...its up to you, but I just think that many options are very expensive with little gain.

something like this may suffice, even simpler would work.

http://www.renntechmercedes.com/www/sites/default/files/imagecache/product_full/red_sls_spl.jpg
 

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Discussion Starter · #17 ·
Well, if you already have the center radiator mod, and the dif cooler, are you still overheating? still having heating issues? if anything I would imagine extra brake ducts would be necessary for a lot of track time.

I think a simple splitter (Carbon fiber panel cut to the shape of the bumper but extended by an inch or 2) might be all you need. No need to change the entire bumper. I mean...its up to you, but I just think that many options are very expensive with little gain.

something like this may suffice, even simpler would work.

http://www.renntechmercedes.com/www/sites/default/files/imagecache/product_full/red_sls_spl.jpg
I haven't had a chance to run the car in real hot weather since I had the third radiator installed. One day at Pueblo about 85 degrees and the oil still got a little warmer than I would like.
After some more research, I am leaning towards the Getty street/track splitter and their wing. The splitter is smaller than the Interseries version. I am waiting for dimensions.
A local shop has custom fit carbon fiber splitter for the GTS but it's quite pricey and the 981S has a different shape than the GTS.
I have never gone into limp mode but I don' want to get that far either. I am hoping to drive the car as is at least thru June/July and see what happens. Then I will decide. I may get lucky and not have to do anything.
Thanks for the input.
 

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no problem, yeah these cars are very strong, the precautions you've already taken will probably help a bunch, but remember that with the added airflow, air exit is equally as important, opening up those exit gates will give an even greater amount of airflow I think. The bottle neck of the airflow may not be the inlet, but the outlet.
 

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You do realise that adding a front splitter would bring the centre of pressure forwards, and if not complemented with a rear diffuser then you're likely to affect the handling of the car?

If Porsche have done their work properly anyway (and you'd have to assume they have) then the entire cooling system should be designed to cope with this sort of usage in mind anyway. One thing you may wish to look at is a lower temp thermostat?
 

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Discussion Starter · #20 ·
You do realise that adding a front splitter would bring the centre of pressure forwards, and if not complemented with a rear diffuser then you're likely to affect the handling of the car?

If Porsche have done their work properly anyway (and you'd have to assume they have) then the entire cooling system should be designed to cope with this sort of usage in mind anyway. One thing you may wish to look at is a lower temp thermostat?
Yes I am aware of the effect of a front splitter and that the car needs to balanced by adding downforce in the rear as well.
 
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