Considering Mods: Aero Kit and 3rd (Center) Radiator

Hi All, I have been experiencing overheating problems at the track on days over 90 degrees (very bad over 95). I clean the radiators with the bumper removal process each yr. That does help, but it does not eliminate the problem. Thus, I am considering adding the third, center radiator as a (hopefully) permanent solution. This requires using a duct for the opening in the bumper to the new radiator. I am also considering an MK1 Aero Kit conversion for my 1999 C4. My primary question: Is the bumper duct the same for the Aero kit as the standard bumper? Secondary Question: For those of you that have done the 3rd radiator upgrade, did it make a major difference? With 122K miles on the car, could the original radiators just be "tired" and just need to be replaced? Thanks! Douglas

One more Question: Is there an advantage to the Aero kit at the track? ...of is it really just cosmetic? Thanks again! Douglas

the 3rd radiator is a good mod for the track... and I would also do the "fan mod" that allows you to turn on your high speed fans and bleed off heat.... if your tracking in hot temps then some good 50 weight oil will also work better than the 40 weight many use on the cars...

Yes the duct is the same and yes the radiator helps, when combined with the low temp thermostat. When the rad gets tired they leak but they don't lose cooling efficiency. Aftermarket rads may also have fewer cooling rows than Porsche rads.

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Do they get any type of sludge that forms inside them? Are they more prone to failure, cracking, etc from age, semi-abuse at the track? They have 125K miles, but overall seem to do a good job. Perhaps it is not necessary to replace them...maybe jut the hoses and rubber parts while installing the Center. That would save some money.

You can use radiator flush, but really leaking is not there only issue, fin damage would also be a consideration, but you would have seen that when your bumper was off. They would need to be quite bad to effect the cooling efficiency.

I'm also in a C4, and did add the aero kit, third radiator, and low temp thermostat. On the highway, coolant temperatures are much lower with this combination. On the track they're a little lower, but not a huge difference. I still get moderately high temperatures just as I end a run (104-106C). Scale inside heat exchangers (radiators) is a common cause for reduced efficiency but I don't think it's much of a concern in a closed system with DI water a coolant. Your more likely to loss efficiency from damage to the fins and random debris that collects in them. I doubt our normal cleaning and vacuuming removes everything lodge between the fins. I have heard of people seeing improvement in track temperatures with new radiators, but I haven't gone this route yet. The aero kit does a nice job of reducing lift and the consequential "floating" sensation you get in stock cars at moderate speeds. I definitely like it at the track.

Radiator Fan mod > 3rd radiator IMHO and much cheaper. Its about how much air you flow through your radiator at the end of the day. I never had my coolant temp exceed 93 C via climate control read out after a 30 min session on a 90 F day in my old aero at WGI. This is one of the best mods for 1st gen 996s. I would make sure the radiator fans are kicking up to high speed properly on both sides. Relays go bad on them.

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I'm not sure about the rocker panels, but the wing and front bumper combined do make a difference on the track. I've run both without it, and with it. As far as the radiator mod vs fans, I doubt very much that the fans do much at speed. Fans are for cooling in traffic and idling. Many racers completely remove the fans.

Regarding the Aero Kit and track use, what is the "trade-off" related to down-force vs horsepower/torque. It makes sense that there would be less "lift" as mentioned, which would affect "grip." However, does the down-force make the car "heavier," thus a little slower with the same horsepower/torque?

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No.

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Absolutely not. I'd say the kit is worth about 1/2 second. I put the Getty Spec 996 wing on my car (basically a cup car wing), and it was worth about 1 1/2 secs. These cars need less lift to really perform.

Well, in theory less lift does mean more drag. On most tracks you're limited more by grip than by power. The additional downforce will get you around most tracks faster but if you were to do a top speed run you might find you lost a couple of mph relative to a car without the it. Top speed is rarely a concern for most DEs...

Be sure to change your oil every 3-4 track days.

Any thoughts on what speeds the Aero kit starts to give an advantage? Here in Denver, our local track (High Plains) is not a very "fast" track; lots of fun with elevation changes, etc. ...but not much time over 100mph and couple tight slower turns.

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Can't say exactly, but at lower speeds than you might think. Hold your hand out your window at 60mph, and see what kind of force you feel. If you really want to get an aero affect at a low price, get the Getty Spec996 wing. You could bolt it on for track weekends, and swap back to stock for street use. It's only $1600 for the setup, which is what you'll end up paying for a taco wing. Only issue is that you will probably want a splitter also to keep the car balanced.

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That may be true but racers also remove AC condensers behind the radiators so air flows easier through. OP need to manually force air through to cool radiators to lower coolant temp unless he is going to remove the AC condensers. The problem is that cars get heat up during runs and cars start at higher temps during the day. When you start with higher temps, they only get higher as you sit around waiting for your next session. Hey, at the end of the day, its your money. Fan mod costs $10 for two switches at radio shack, some wires and sweat equity. How much does a 3rd radiator set up cost? Few hundred beans when its all said and done. Ferd and I did the fan mod and he runs a supercharger with the 3rd radiator as his IC. We have found the Fan mod is the best bang for your buck for dealing with controlling coolant temp in a DE car.

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What wing were you running before that Mike ?

OK, I am going for the Aero Kit. I 'll post some before/after pics. It will take a couple weeks, but the parts are ordered. ...still plotting on the heat management plan. Thanks for all the comments!

Hi All, Heat management plan completed: 1) Add Center Radiator 2) Clean Left and Right Radiators thoroughly while coolant was out of the car and inspect (look fine) 3) Fan Mod for High-Speed Fan only 4) Low-Temp Thermostat That should do the trick! I have only been able to drive the car from the Tech shop to the Body shop - where the Aero Kit is being installed. So, I wasn't able to test it. The car will get a good workout at the track next weekend at HPR (Club Race /DE). If you're in CO at the event say "Hi." ...I'll post some pics and results after the DE.

try a product called "Water Wetter"

Re: Water Wetter - I have heard that is does not work well with the Porsche Coolant - it works best with "Water" in the cooling system. ...I am hoping my fixes handle my heat problems without it.

water wetter mixed with pure distilled water did absolutely nothing for my temps; if you want something effective try removing the belly pans underneath your car to allow massive airflow to engine and tranny... I noticed a difference there...

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I actually heard the opposite... are you sure about this?

you order the front aero bumper yet? i might be selling mine.

^^^ Yes, I got a whole genuine MK1 kit on Ebay for a song. I hope to pickup the car with the upgrades done in a couple days. Heh, they listed as an "Arrow Kit" and it was unsold for months until I grabbed it a great price with an offer. ...F & R bumpers with diffusers, side skirts, wing; the whole kit.

OK, transition complete... More pics to come.

Classic. I miss my old car...

that looks good

Some pics from the track today... Hanging with the Race Car Cousins: Side view with 5-Spoke track wheels: Pic of the hex-grill mentioned above and why the "grille" matters:

BTW - cooling problem appears to be solved. I had no problems pushing the car for 25-30 minutes at 85-90 degrees.