914-6 air conditioning, Advice on compressor choise Options

[turboman]

Hi, I am in the process to install an original 914 VPC system in my 914-6.
Like all my projects, I work on a budget.
First I bought all the parts about 5 years ago, then I refurbished all parts, (professional cleaning, expansion valve) installed the condenser in the front trunk as designed, temporary installed the evaporator console under the dash, and start the preparation process for the compressor installation.
I want the installation to be as close as possible to a factory one.
For me, is not an option a compressor under the engine, a serpentine belt or similar. I prefer to work extra time, and reach a perfect end product.
I used a double pulley from a 74 911, in order to install the pulley and have space for the dual belts, I have to shave a bit the original engine support and the engine cover (see photo).
I fit a 2.2 or 2.4 bracket. So far no problems, the end result looks very nice
Now I need to choose the compressor.
The York is out of question, due to size and efficiency. My options are a Sanden, a Denso or a Panasonic. Any one fitted with a one groove pulley
Not being familiar with the air conditioner compressors, and the way you need to calculate cooling capacity vs cabin volume, I would like to ask help form all of you.
1. Which compressor will suit my needs the best?
2. Which compressor is the smallest one?
3. The best compromise?
I will keep all of you posted of the progress on the installation and the need or not of a firewall modification.
Thanks
Francisco

[JawjaPorsche]

I thought it did not get hot enough in France to need AC?!! It got to 106 F. here on Saturday! Drove the teener early then parked it rest of the day. Nice looking teener!

[Al Meredith]

George Hussey at Auto Atlanta has Peter Greg's 916 that I think has factory installed AC . The pulley of the AC compressor must go through the firewall. On George's car there is a hump in the firewall behind the drivers seat.

[mepstein]

George Hussey at Auto Atlanta has Peter Greg's 916 that I think has factory installed AC . The pulley of the AC compressor must go through the firewall. On George's car there is a hump in the firewall behind the drivers seat.

I'm pretty sure George's 916 has a crude, covered up hole in the firewall. I also remember reading it was not factory installed but added on when the car was brought over from Germany. There is no "factory" installed a/c in a 914-6 and so far, very limited success with aftermarket installs. The factory a/c mount on the six causes the compressor to hit the firewall.

I wonder if an electric compressor might work. Like something used on an electric car.

[IronHillRestorations]

Hopefully Clay Perrine will chime in here. He's done a very clean install on a 6 conversion using a serpentine belt set up.

[mepstein]

Hopefully Clay Perrine will chime in here. He's done a very clean install on a 6 conversion using a serpentine belt set up.

It did look good but didn't work in the long run. I think the compressor bracket was bolted on to the valve cover and broke the studs or something. I am hoping he comes up with a solution.

[veltror]

Hello,


talk to michale at mittelmotor, they have just done AC in a 6 for some guy

Roman

[Larry.Hubby]

I used a Sanden 505 compressor because it was the smallest unit I could find at the time I was looking, although I didn't look at the Nipondensos. Here's the way I solved the firewall interference problem:





As you can see, I used a jackshaft to offset the belt drive toward the rear enough to clear the compressor, which had to be mounted as high as in the stock location. The Sanden 505 is short enough that there is room to do this. The clearance in the car is tight, but the compressor clears the firewall without requiring the latter to be cut:



I've seen several other 914-6 AC installations that use some sort of jackshaft arrangement similar to this one.

I too considered an electric compressor, which would be attractive because it could be mounted almost anywhere. The one in the Prius (at least the one in the early Prius) ran on 12V even, but it draws 100A! That's a lot more than the maximum output of my alternator, so you'd be discharging the battery steadily when running the AC.

[ClayPerrine]

I actually solved the AC bracket problem. When I built mine, I used the serpentine belt, and made the compressor bracket mount to the smog pump mounts on the timing cover. That caused too much load and the timing chain box cracked. My plans are to extend the bracket to the engine mount, and use aluminum to build the bracket to lighten it.

Here is the picture of the compressor mount.

(IMG:http://www.914world.com/bbs2/uploads/post-1143-1155171242.jpg)

The bracket in the front of the picture needs to be extended to the motor mount.

More info HERE

[rgalla9146]

I used a Sanden 505 compressor because it was the smallest unit I could find at the time I was looking, although I didn't look at the Nipondensos. Here's the way I solved the firewall interference problem:
As you can see, I used a jackshaft to offset the belt drive toward the rear enough to clear the compressor, which had to be mounted as high as in the stock location. The Sanden 505 is short enough that there is room to do this. The clearance in the car is tight, but the compressor clears the firewall without requiring the latter to be cut:

I've seen several other 914-6 AC installations that use some sort of jackshaft arrangement similar to this one.

I too considered an electric compressor, which would be attractive because it could be mounted almost anywhere. The one in the Prius (at least the one in the early Prius) ran on 12V even, but it draws 100A! That's a lot more than the maximum output of my alternator, so you'd be discharging the battery steadily when running the AC.

Is the other accessory drive PS or an air pump ?
How effective is your AC installation ? Are you using other components as found in 4 cyl. installations ?

[GeorgeRud]

I don't think the layshaft arrangement would work with a carbed car. Clay's solution may be best once a bracket that attaches to the motormount is perfected.

I always wondered if there would be a way to drive the compressor from a CV joint on the axle. It obviously would only work with the car moving, but may be a viable alternative.

I think that the -6 just wasn't engineered to have AC!

[Larry.Hubby]

The other accessory drive on my engine is for power steering. The pump mounts where the smog pump used to, like Clay Perrine's compressor mount, only the pump is much lighter than an AC compressor and not hung out as far as Clay had his.

I don't have my whole system running just yet, but no, I'm not going to use any of the usual 914 AC components. I'm using a condenser coil from a Honda Civic and making a custom evaporator using a 911 coil that replaces the stock air box. I'll post the result when (and if) I get it all finished.

Not sure about GeorgeRud's point, since my engine has the stock CIS FI. There is room to hang the compressor out farther to the side than I have it, and If you go far enough with that you can lower it enough that my solution sort of turns into Clay's.

[ThePaintedMan]

I always wondered if there would be a way to drive the compressor from a CV joint on the axle. It obviously would only work with the car moving, but may be a viable alternative.

Thats a good idea! I had an idea in high school that you could do the same thing with a turbo, using the exhaust gases to run a compressor. At least it wouldn't pull HP from the engine, but getting it to spin slowly enough and not burn out the compressor bearings. Wish I had been an engineer.

How do hybrids like the Prius run their AC? Must be some sort of electric compressor, otherwise you wouldn't have AC when the gas engine is off. Could one be sourced from a junkyard?

[turboman]

Hi,
thanks to all of you that share your ideas with me.
I follow Vectror advice, and got in touch with Michael at Mittelmotor in Germany.
Michael and his team successfully installed a Cool VPC system from a 914-4 into a 914-6, without any modification at firewall level.
Michael sent me some photos of the compressor, and the bracket they build.
Now I will buy the same compressor Michael and his team used and keep all of you posted with as many photos as possible. Hopping my experience will help other owners wishing to ride cool.
Again thanks
Francisco

[pcar916]

On running an axle pulley as a power take-off. It's been used on various cars to power the alternators and I don't see any reason it can't be used on the AC as well. I was going to use it that way except that it would have taken up trunk space. The rear trunk space is all I have left in my 914 so I give it up reluctantly. But to make that work...

I would want to design an electric cutoff to disengage the clutch below a certain rpm (to keep flow through the the expansion valve from getting too low) and that would depend on the relative pulley sizes. The only way to keep it running while below that rpm would be a fairly large electric motor and a differential clutch/pulley. That's a lot of weight for a light car, not to mention the complexity, and there's a maintenance cost for the latter that I'm not willing to pay.

I haven't jumped in on this but may next year since I have most of the bits. Too many projects to worry about it this summer. Hmmm

Ice/water box and a small electric pump for a cool-jacket, or an RV / AC box on the roof!?

Wouldn't that be a sight... (IMG:style_emoticons/default/beerchug.gif)

[ClayPerrine]

an RV / AC box on the roof!?

Wouldn't that be a sight... (IMG:style_emoticons/default/beerchug.gif)

Typical Arkansas redneck way of fixin stuff...

Use lots of duct tape.

And keep an eye on your steering wheel.

[pcar916]

And keep an eye on your steering wheel.

Hey! Don't start with me dude! (IMG:style_emoticons/default/beerchug.gif) I know exactly where my steering wheel is and as long as you and JT aren't around I generally do, with a very few senior moments notwithstanding. And I didn't date any cousins... mostly... that I know of.

The axle-powered compressor would work fine most of the time but I would never do it to a city-bound car. There are no critical failure modes I can think of with one exception. Changing belts would be an itch.

Does anyone have any numbers about how much power it takes to run some typical compressors at speed and 85F or some other milestone? To be fair I haven't looked into it yet. Just being lazy.

I know, it depends but a broad stroke is ok here. I'm thinking a system in good condition would probably such up 15-20 hp or thereabouts but that's a wag without doing any calculations. Anyone? All of my best AC contacts are commercial HVAC guys who's compressors are always run at a constant speed and with different refrigerants. My steam tables are old!!!!

I'm not factoring in any clutch-type LSD issues here. Gotta keep it general-case at first.

[turboman]

As I mentioned I got in contact with Michael at Mittelmotor in Germany http://www.mittelmotor.de they made an instalation of a VPC Cool A/C into a 914-6.
No modification was made to the firewall.
Look at the photos.

[turboman]

Mikael used a DELPHI SP10 compressor.

[turboman]

Look at the modification on the engine support and front engine plate.
Thanks to Mittelmotor for the help.

Next week I will start my instalation, will keep you posted.

Francisco (IMG:style_emoticons/default/evilgrin.gif)