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Hybrid System - How much oil?

byrden on Wed August 27, 2008 8:57 PM User is offline

Year: 1993
Make: Mazda
Model: RX7
Engine Size: 5.7
Refrigerant Type: R134a
Country of Origin: United States

I building a "hybrid" system. I'm using a compressor (and engine) from a 2001 Camaro in a Mazda RX7. I'll be using the Mazda evaporator/expansion valve, and universal condenser/drier. Does anyone have any input to help me decide how much oil to put into this system. I'll be using R134a and flushing out the mazda evaporator. The factory specs for the two systems are:

Mazda:
Denso TV14
21.2oz R12
3.4 to 4.7oz Mineral oil

Camaro
Delphi V-7
24.0oz R134a
9oz PAG

The camaro definitely has much more oil per volume of refrigerant than the mazda (about twice as much). I'm guessing the compressor dictates the amount of oil for the most part. Since the hybrid system will most likely take less refrigerant than the camaro I think I should also put in less oil than the 9oz. Should I make a guess at the amount of refrigerant it will take and keep the same proportion of oil that's spec'd for the camaro?

Thanks

mk378 on Thu August 28, 2008 10:45 AM User is offline

The V-7 has an oil sump. Most of the system's oil stays in there instead of moving around with the refrigerant like the non-sump Denso system would. So I'd say stick with a full 9 oz of oil.

Do not try to flush thru an expansion valve, disconnect it from the evaporator to flush the evaporator.

94RX-7 on Thu August 28, 2008 11:54 AM User is offline

How big is your aftermarket condenser in relation to the stock RX-7 condenser? Is it a parallel flow unit like the stock condenser? If if is the same size and type then I would suggest you put in just a hair under 2 cans and see what the pressures look like, and what the performance is like, then adjust up or down.

When you have it up and running, let us know how it performs versus the stock setup. The stock system in my '94 is on the weak side, IMHO.

byrden on Fri August 29, 2008 8:30 PM User is offline

Quote
Originally posted by: mk378
The V-7 has an oil sump. Most of the system's oil stays in there instead of moving around with the refrigerant like the non-sump Denso system would. So I'd say stick with a full 9 oz of oil.



Do not try to flush thru an expansion valve, disconnect it from the evaporator to flush the evaporator.


Thanks for the input. I didn't even realize that the Denso system didn't have a sump, but that makes sense now. I already have the evaporator out of the car, and txv removed. I'm going to take it to a local shop to flush.

byrden on Fri August 29, 2008 9:25 PM User is offline

Quote
Originally posted by: 94RX-7
How big is your aftermarket condenser in relation to the stock RX-7 condenser? Is it a parallel flow unit like the stock condenser? If if is the same size and type then I would suggest you put in just a hair under 2 cans and see what the pressures look like, and what the performance is like, then adjust up or down.



When you have it up and running, let us know how it performs versus the stock setup. The stock system in my '94 is on the weak side, IMHO.

I got a hold of a universal parallel flow condenser, 12x24 inch core. The stock is 11x24 , as I'm sure you know there's not much room in there so it looked like 12x24 is about as large as I could go. I can't compare it to well to the original system because I don't think it worked very well. I have this sneaking suspicion though that the heater box isn't sealed off to well now with the 16 year old foam in there. I think I'm going to set up a bypass valve so that coolant isn't always flowing through the heater core. I'll get the a/c hooked up first to get a baseline, then work up the bypass and see if it has any effect.

I can't see how it could hurt. Pumping 200 degree F liquid through a radiator (in a non insulated box) in a compartment your trying to cool just doesn't seem like a great idea.

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