Just wants to try and spur a discussion as to which is more beneficial if your had to choose between two options. The Z51 adds the ability to cool the oil via the factory radiator. This lead me to pose the following question to those who install the pricey Dewitts or Ron Davis radiators for high performance applications. It seems to me that if you can improve upon the Z51's ability to cool the oil then you may be able to get away with the factory radiator instead of installing a Dewitts or Ron Davis. By disconnecting the cooling lines from the filter housing and running them instead to a larger oil cooler with its own spal fan. Maintaining a cooler oil should keep coolant temps in check. This might be a cheaper cooling solution than a new high performance radiator. Thoughts....

 

I believe you are thinking from the position that your stock radiator will be sufficient to cool your modified engine. I say the stock radiator is barely adequate for the stock motor...especially true for those of us who live in the south and for those that might have a large supercharger intercooler in front of it. I think you need to address both engine cooling and oil cooling as part of the solution. For max benefit you'd want a better radiator plus a separate setup to cool engine oil. Done properly it won't be cheap by the time you buy the cooler/s, braided lines, AN fittings, adapter for the block, etc. I bet you'll have as much in your engine oil cooler as you do in buying a radiator. If it is in the budget, do both. If both isn't in the budget then get the better radiator with the built-in oil cooler. My two cents worth.

 

Well stated in any performance application you have to address both the oil & coolant temps. A issue that is sometimes over looked is insuring that your oil temp is in the normal operating range prior to mashing the "Go" pedal

 

Z51 manual cars have an external oil cooler, not an in radiator cooler. Maybe you're thinking about the A6 using the radiator to provide transmission cooling??

The Z06 oil cooler is even bigger than the Z51 and provides a lot of cooling. A 160 T-stat and factory passive external oil cooler provide enough cooling for most NA cars. Blower cars are a different story if tracked hard.

 

It is year and transmission dependent. The external Z51 oil cooler didn't start showing up until 2008 I believe. The few that I recall include a 2005 MN6 which had the radiator engine oil cooler plus the trans cooler, several 2006/2007 A6 Z51 cars that all had no engine oil cooler but of course had the automatic trans coolers and most recently a 2008 Z51 MN6 which had the external oil cooler and transmission oil cooler. I remember seeing a thread on this subject...going to go try and dig it up now.

 

For non modded cars the factory radiator can keep cooling temps reasonable if you have a separate oil cooler. There are very few instances where you need the extra cooling and running in traffic in high ambient temps isn't one of them. Where you run into cooling system capacity issues is running at Wide Open Throttle or near Wide Open Throttle for extended periods. A lot of racers or HPDE participants see high cooling system temps where they run on the track for 25 minutes or more at those throttle openings (power levels). On a base C6 without any extra oil cooling the cooling system temps will approach 230 and oil temps will be in the 300+ range when running in these conditions. An outside oil cooler can bring the oil temps down as much as 40 degrees and the cooling system temps down as much as 20 degrees. My 08Z runs around 205 coolant temp and 258 oil temp pretty much all of the time in ambient temps running from 40 to 90.

When I ran my C5 and then my C5 Z with a Ron Davis Racing Radiator with built in EOC I was able to bring the temps down from the C6 base levels mentioned above to 200 degrees coolant and 230 oil while using a stock thermostat. The year I got my 03Z and before I installed the larger radiator my oil temps hit 319 on one long session on a 90 degree day. When on the track I pay more attention to the oil temp and have it displayed on the DIC. The analog coolant gauge is hard to read and isn't as important so I don't focus on it much.

Bill

 

You are correct the 2005 Z51 does have both engine oil and transmission cooling built into the radiator. My thought process was that if you cool the oil down below 200 then the radiator will have less work managing coolant temps because the oil cooler is dissipating more of the heat.

 

You are supercharged right? Centri right? You'll want to consider the heat being dissipated by the large air-to-air intercooler sitting directly in front of the radiator.

 

Correct and correct, that is why I am looking at this. I have a bassani exhaust so the area where the cans usually sit in the rear are wide open for the addition of a large oil cooler with fans such as this.

http://www.prchotrod.com/media-cente...oil_cooler.jpg

 

Question: Can you plumb all the way to the rear and back and maintain good oil pressure without some sort of aux pump?

 

That's a good question, I don't see why a melling can't do it. Maybe someone can answer that one.

 

You might want to go browse around in the "Autocrossing and Roadracing" forum. Those guys probably have a hundred different ideas on oil cooler setups.

 

It is true that by moving the oil cooler out of the radiator you are taking some load off the cooling system, but I think the stock radiator is going to really be pushed to the limit with a bigger engine and a big intercooler blocking it. I had an external Z51 cooler that I needed to get rid of to fit my intercooler. I could have relocated it somewhere in the nose, but that would have probably required taking out the fog lights, adding new lines, and other things I really didn't want to do.

I ended up getting a DeWitt's with the built-in oil cooler. In addition to the added cooling capacity for the coolant, the Dewitt's has a 7 plate oil cooler plate inside. A factory '05 Z51 oil cooler only has a 3 plate.



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I'm one of those guys that thinks simple is better when it comes to most things. I'm not too into the idea of having a bunch of aftermarket oil lines running around my car that could leak or be damaged. I know my oil cooler isn't as effective as a big air-cooled unit, but works well and is simple. Plus, it helps my oil warm up much faster than it did with my old Z51 external cooler.