Is there a good 12v ac compressor? I thought most of the automotive ones were 48volts.
Is there a good 12v ac compressor? I thought most of the automotive ones were 48volts.
In reply to Gammaboy :
That sounds right. I have an 80A that I know is about at its limit and then some with all the stuff I've added or upsized. Fuel pump is 20A vs 10A, 40A to the coils (and I run wasted spark so it used double the power, but my ecu only has 10 spark channels) vs 10, the electic throttle is 15A, 50A on the electric PS I added. I'm pretty marginal and probably using battery if I want high rpm, throttle and steering all at the same time 
The amazon compressor is 600W, at 13.7V that is 44A and I saw a similar looking system on amazon that said 75A on startup.
Then the question in my mind is if its enough AC to be worth the bother? Reading a bit, OEM systems in most cars are 12k-24k, SUVs more which seems crazy but there is a lot of glass and people like the car to cool down quickly. 600W input should output 5-6kBTU (a 5k window unit draws 530W). I guess in a small 2 seat cabin it SHOULD be enough? I guess?
Problem for another day but I might upgrade the alternator knowing its marginal at best.
mke said:OEM systems in most cars are 12k-24k, SUVs more which seems crazy but there is a lot of glass and people like the car to cool down quickly.
....600W input should output 5-6kBTU
Wait, so run 2 and have a 2 speed system! Low/high 6/12k btu
In reply to mke :
Interesting. That compressor lists a cooling capacity of 1800W, which calculates (BTU = W x 3.41) to about 6100 BTUs, which should be enough to cool a relatively small 308 cabin.
Would the plan be to reuse the original 308 A/C condenser? Did that have an auxiliary fan?
Ian F (Forum Supporter) said:In reply to mke :
Interesting. That compressor lists a cooling capacity of 1800W, which calculates (BTU = W x 3.41) to about 6100 BTUs, which should be enough to cool a relatively small 308 cabin.
Would the plan be to reuse the original 308 A/C condenser? Did that have an auxiliary fan?
308s are pretty notorious for poor AC.....lots of heat leaks in everywhere I guess but 6k btu does seem like it should be enough. I still have the original evaporator and the AC has its own fan for the cabin though.
I changed the radiator size/mounting angle and at the time bough but never installed a matching condenser from vintage air so that can be installed in front of the radiator.
Originally switching on AC would turn on 1 of the 2 radiator fans but they are gone now and I have 1 large fan controlled by the ECU (of course :) ), but I can tell the ecu to turn it on if AC selected and is speed under whatever mph I guess, that would be easy enough to add to the programming.
I was just trying to figure out what size/capacity the evaporator might be and recalled its pretty similar design to the vintage air slimline setup and while trying to figure out what that setup delivers I found this article that basically say just don't, 5-7k btu is not enough.
Vintage air Electric compressor thoughts
but that brings me back to 2 units if one proves inadequate I guess
Ian F (Forum Supporter) said:In reply to mke :
Interesting. That compressor lists a cooling capacity of 1800W, which calculates (BTU = W x 3.41) to about 6100 BTUs, which should be enough to cool a relatively small 308 cabin.
Would the plan be to reuse the original 308 A/C condenser? Did that have an auxiliary fan?
I thought automotive A/C was usually on the order of 20-40k BTU.
Cars are a worst case scenario, poor insulation and heavy insolation (see what I did there?). A house is relatively well insulated, and has fairly low glass to volume. Unless it's a greenhouse, which is the most carlike of houses.
Pete. (l33t FS) said:I thought automotive A/C was usually on the order of 20-40k BTU.
Google told me 12k - 40k, vintage air says "NOTE: Vintage Air system capacities range from 14,000 to 20,000 BTU, depending on the model."
I think anything over 20k is SUV?
Ian F (Forum Supporter) said:In reply to mke :
Interesting. That compressor lists a cooling capacity of 1800W, which calculates (BTU = W x 3.41) to about 6100 BTUs
I kind of wonder about converting like that. 600W in, 1800 out is a system COP of 3 which pretty ok and a little better than the cheap GE 5k but wall unit.....but system numbers are probably more about the heat exchangers than the compressor. My home units are 2 speed compressors, I assume 1700 and 3400 rpm, that yields 2.5 and 4 ton, so a much better COP on low where I assume it's optimized.
Anyway, my thought was the 308 system is mostly designed to fit not really optimized and they probably sized the compressor to get the most out of an undersize evaporator with poor air flow so a smaller compressor should yield a higher COP and 600in my get me 2400 out? and only be 1/3 undersize instead of a full 1/2 undersize 
Keith Tanner said:DaewooOfDeath said:Pete. (l33t FS) said:In reply to DaewooOfDeath :
Bars don't convert roll to weight transfer, lateral load vs. the center of gravity creates weight transfer, playing with bars converts how much of that happens at each end, by altering the lateral load dependent spring rate.
So he's sort of right, but also wrong in the Herb Adams way, when he would say that antisquat can create over 100% load transfer. Maybe momentarily but not steady state.
I'm familiar with the traditional view, and yeah, I don't know for sure. The argument he presented was that a Segway would roll less and transfer more weight with a swaybar. This is supposed to be the case because the bar transfers what would be roll and literally presses down on the outside wheel to resist it. Almost everyone I've talked to with a math/physics background has given me a different answer on this.
I do know that F1 tries to make every mode of motion go through its own set of springs and dampers separate from the rest, so I'm not sure if that plays by either the traditional or the Hoelscher rules.
Roll is a manifestation of weight transfer, not a cause. The sway bars increase roll stiffness, so there's less roll for a given amount of weight transfer. On a two-axle vehicle, the weight transfer is also distributed as a function of the relative front/rear roll stiffness but the total amount remains the same.
Sways allow for the suspension to separate two-wheel bumps (dips, crests, etc) from one-wheel bumps and roll. This also has an effect on how you'd tune low speed damping. They're also the easiest way to adjust steady state handling balance and - unless you go crazy - seem to offer more overall compliance for a given level of roll stiffness.
Roll is a manifestation of weight transfer, not the other way around. Relative stiffness front/rear causes front rear weight transfer differences. I understand this.
As for the rest, you might find these interesting.
https://www.mr2oc.com/threads/sts2-mk1-suspension-setup-w-host-xhead.298272/
https://www.mr2oc.com/threads/sts2-mk1-suspension-setup-w-host-xhead-part-2-0.313691/
In reply to mke :
Yes, I would imagine with the 308 it'll be a case of "what can you make fit" vs. "actually designed to modern standards." I'm in a similar boat as I ponder stuffing A/C into my Spitfire and GT6 - two cars that were never offered with A/C and with extremely limited space.
In reply to Ian F (Forum Supporter) :
The 308 system is quite strange. The AC is basically stand-a-lone and looks like an after thought..the 246 Dino didn't have AC I don't think so in the 308 it probably an after though and probably why the cooling system is so marginal. Then for heat there are 2 separate heater cores and blowers, but only 1 blower switch.
It's all starting to come back and I remember why I knew vintage air has an under dash setup much like the OEM 308....I was so frustrated with how poor the AC was was I was looking at replacement options...before I did the big blower engine and then V12.
I have way more thoughts in my head than money or time......back to sanding floors for a few more days....but I'll probably keep looking at 12V compressor options to see if something a big larger can be found.
In reply to mke :
I'm sure when Ferrari started designing the 308 in the early 70s, A/C was not considered a mandatory feature and certainly was an afterthought.
But yes, that's how a lot of vintage car A/C systems were done - add-on units separate from the heating system. Makes the system a compromise as they often don't connect to the defrost ports so you lose that function modern HVAC has. The Volvo 1800 system is like this - just an under-dash evaporator unit completely separate from the heater system.
My plan is to replace the existing heater box with the smallest vintage air combination box I can get and then fabricate or 3D print ducts to go from the outlets to the various points in the car. I also plan to add more insulation where possible. It will definitely be a challenge in all aspects.
Ian F (Forum Supporter) said:My plan is to replace the existing heater box with the smallest vintage air combination box I can get and then fabricate or 3D print ducts to go from the outlets to the various points in the car. I also plan to add more insulation where possible. It will definitely be a challenge in all aspects.
Sounds like an excellent plan. It seems like their website is less helpful than it once was, I don't see outputs on any system or even dimensions on most :(
This might be the right size compressor, looks like 3 speed 66A on high
Edit: I see they also have a smaller 14cc unit, also 3 speed and appears to be higher output than the amazon unit
I still don't think it will work all that great but it will at least work better than nothing.
Which, to be fair, is probably about as well as the original A/C worked, so it's period correct.
I'd use the biggest MODERN condensor you can fit - something from a newer small car. Condensor tech has come a long way since the 1970s, there is a lot of surface area in the tubes compared to the old stuff that was more or less a high pressure radiator, and anything you can do to extract the maximum heat from the condensor means there will be less load on the compressor.
Older to newer. They get even finer than that, like human hair sized passages!
In reply to Pete. (l33t FS) :
I have a vintage air 14x 22 superflow condenser on the shelf...its one of the larger ones they sell..with out cutting it it looks like design 3 or 4 from the left.
I spent a bunch of down time during the pandemic looking at building my own equivalent to the Classic Retrofit system that is quite popular with the Porsche guys (hell, even Singer are using it on their DLS cars).
Big thread here:
Using a modern evaporator in the AC box, and getting enough modern condenser into the system seems to be a big help.
Gammaboy said:I spent a bunch of down time during the pandemic looking at building my own equivalent to the Classic Retrofit system that is quite popular with the Porsche guys (hell, even Singer are using it on their DLS cars).
It is a long thread, which I will read, but can you share here what compressor you used and how the system is performing for you?
mke said:Gammaboy said:I spent a bunch of down time during the pandemic looking at building my own equivalent to the Classic Retrofit system that is quite popular with the Porsche guys (hell, even Singer are using it on their DLS cars).
It is a long thread, which I will read, but can you share here what compressor you used and how the system is performing for you?
I got through most of it. To me the biggest takeaway was CR uses an ECU to vary compressor speed to maintain system voltage. I saw amp draws of 40-85 in various places and the original development system was pulling 40A I think it was and working fine...with a good condenser and evaporator, also recirc is required even with OEM engine driven systems to work right.
This piece I think was interesting
"Here's a typical Sanden compressor rated at 14400 BTU (4.2kW).
The output is around 1.4 kW at 1000 RPM which is 4776 BTU"
The ebay compressors seem to be right in the same ranges they talk about. I also noticed there are 3 speed and variable speed version. The 3 speed is 3000, 3500, 4000 rpm which says it draws 580W(42A)/670W(48A)/780W(57A) with cooling capaciies of 1.43/1.69/1.94kW. The variable is 490W(36A)-1170W(85A) with cooling capacities of 1.16-3.16kW so this one looks very similar to the CR amperage numbers, but needs a PWM signal to set the speed. Both units will provided as much cooling as a standard engine driven unit at idle/low revs.
I bought a 180A reconditioned denso alternator for $115. This LOOKS like the bits CR is using in there 175A upgrade 911 and 308 alternators so I figured it was worth having a look at. CR says 75A at idle
With that alternator I could easily run the compressor on low at idle. From there the question is how fancy to get.....I do have an ECU that would be happy to vary the compressor speed and/or engine idle speed to maintain system voltage or AC discharge temp or ????.
A project for another day, but hopefully the new alternator will fit so I'm ready when the day AC tops the to-do list arrives.
I would love to upgrade the A/C on my Mondial. It was converted to 134 in the 90's but I'd be thrilled to retrofit some modern pieces to it and I don't care what they came off of. I've always heard on r12 to r134 cars the old style condensers and evaporators aren't as efficient running it.
I'll be interested to see how you integrate stuff in.
The 308 V12 conversion that started it all is for sale:
Last night I hit the contact seller and inquired about the asking price but no response yet. It looks like a nicely done restoration, I saw an article about 2017 (?) that is was in Germany and being or had been restored, it looks like the owner is ready to move on.
Another is shown in this video post 3 months ago
He says its being prepared for BaT, but I've not seen it pop up there yet.
If mine counts, there are 5 V12 308s. One with a complete 400i and RHD and looked decent, although the engine bay looked a bit messy with all the CIS stuff and market in 2017(?) and sold for like $40K which seemed very low. Then there are 3 365 conversions, one sold last year or the year before and is in Atlanta. Now the very 1st conversion is being sold in germany and the remaining 365 conversion appear to be heading to market soon.
crankwalk (Forum Supporter) said:I would love to upgrade the A/C on my Mondial. It was converted to 134 in the 90's but I'd be thrilled to retrofit some modern pieces to it and I don't care what they came off of. I've always heard on r12 to r134 cars the old style condensers and evaporators aren't as efficient running it.
I'll be interested to see how you integrate stuff in.
I just saw a thread on 134a conversion that might interest you before you go down the electric path that I'm heading toward mostly because fitting a compressor to my engine would be quite a challenge.
They are asking €475.000,00 for the goldsmith car. Its had a recent restoration but that's quite a number. I tried to find a price for a single cam 365 engine but couldn't.....I THINK 50-150 depending on year and condition but it's mostly a guess.
mke said:Gammaboy said:I spent a bunch of down time during the pandemic looking at building my own equivalent to the Classic Retrofit system that is quite popular with the Porsche guys (hell, even Singer are using it on their DLS cars).
It is a long thread, which I will read, but can you share here what compressor you used and how the system is performing for you?
Unfortunately I haven't progressed the project. In the meantime I moved from Germany back to Australia, extended a shed and (still) fitting it out, ongoing maintenance/tweaking on a E55, Cayenne GTS and the Alfa GTV, plus trying to find time to work on restoring a Bimota SB6, plus work and family commitments means that the electric AC is really on the back burner.... There's another bike project that hasn't even made it home yet from storage!
I had identified a Alibaba supplier for a compressor that appeared to be the same unit used by either classic retrofit or Rencool, but beyond identifying what I needed and figuring out roughly where everything went (and buying a spare factory heater box to figure out if I could get the evaporator in there neatly), I just haven't got there. My use of the car has changed a lot since I started investigating too.
You'll need to log in to post.
