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Classic Retrofit AC Write Up

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13 hours ago, Jonny Retrofit said:

Here are the airflow measurements (made with a handheld anemometer).  

Max face level cooling:

Fan on full,  All other levers left.

Centre vent:  2 x 7.1 m/s

Small side vents.  2 x 7.0 m/s

Hidden vents.  0 m/s

Full body cooling:

Fan on full,  Top lever right.  All other levers left.

Centre vent:  2 x 5.5 m/s

Small side vents.  2 x 5.1 m/s

Hidden vents.  2 x 7.5 m/s

And some maths...

You can convert the air speed readings to volume of air moved based on the vent sizes and this gives the following for both settings:

Max face position:  78 CFM 

Full body position: 120 CFM

Jonny,

Have you ever done the same measurements in a modern car to create a benchmark to aim for?

I did some temperature comparisons between my first upgrade ('85 911) and a new Subaru Outback I had at the time on a reasonable warm day.  While I found the vent temperature to be comparable, it was the air volume that made the difference between just comfortable and nicely comfortable.  

 

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17 hours ago, Peter M said:

Jonny,

Have you ever done the same measurements in a modern car to create a benchmark to aim for?

Yes, we did back to back tests against a new car and a 964 in a climate chamber at 42 deg C.   The test report is on this page:

http://www.classicretrofit.com/electrocooler-complete-kit-for-911-1974--1989/

The testing was done before we improved the airflow and is indeed how we identified it as an issue.

It's all very well saying use a bigger fan etc but it's not that simple.  Quoted fan static pressures DO NOT equate to final flow rates due to variations in duct lengths and inlet and outlet sizes.  

There is a relationship between fan speed, air turbulence in the evaporator and vent temperatures.   Our vents run down to about 8 degrees in 35C ambient with full fan.  You'll see tons of threads on Pelican about guys with 1 or 2 degree C vent temperatures.   All that proves is that they have poor air flow.   Sure, if you turn our system down to fan speed 1 you'll get your vents cooler - meaningless without the flow.  My daily drive JLR box NEVER blows colder than 7 degrees even on max AC.

Packaging in our minuscule cars is also a massive challenge.  I have a VAG HVAC unit in the workshop, it takes up 3/4 of the dashboard, measuring 800mm x 300mm x 300mm.   Yes, it will blow your hair piece to kingdom come but there is no way it will ever fit in our cars.  

If you want to see an attempt to fit a complete OEM modern unit in a 911, here is one that got installed in Chris Harris's green 911 a few years back (FWD to 6.55) :

 

 

Beautiful isn't it?  :o (That car was built by Tuthill Porsche.  Btw, they never 'made it smaller' and now use our system).

We are happy that we have doubled the air flow of the original Porsche AC system within the constraints of the 911 bodyshell and without detracting from aesthetics.

Here's how we are looking :

rswerks.png

 

 

 

 

 

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Lol!  The car's grown a goitre!

Jonny, there is no denying that you have the most beautiful evaporator setup in the business.

Thanks for the informed discussion, appreciated.

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On 2/26/2018 at 10:05 AM, Peter M said:

Lol!  The car's grown a goitre!

Jonny, there is no denying that you have the most beautiful evaporator setup in the business.

Thanks for the informed discussion, appreciated.

lol x 2 there is a giant orange octopus under the hood!  Just to round things off, my car is back at Nineauto getting the engine tuned and getting the dash vent controls fixed.  I will read the AC operating instructions carefully in the mean time and report back once this step is complete. 

On 2/24/2018 at 10:07 AM, Jonny Retrofit said:

Nick,  I'm surprised about your blower comment so think something is amiss.

it is quite specific how to set the sliders to get the recirculation to work so please try this:

For max blower flow,  fan on full and ALL other levers to the left.  Jammed ain't good ;)

Then, just use the top left lever to blend between face and feet.  Fully left is all face which will have the most cooling effect, but I like a little on my feet to slide right just a tad.

Please also check that your heat 'flappers' are fully closed.  Easiest way is to feel the pipes in the front foot wells when you are driving.  If they are at all warm, then the AC is being fed hot air which isn't good.  Often they don't close fully so you could disconnect the hoses behind the carpet and block them if this is the case.

We have a car in Singapore right now and the customer is more than happy so I think you have a little bit of detective work to do.   Check that the air is not leaking out anywhere under the cowl.  Put the blower on full and have a feel aroind behind the blower cover.  

Let me know how you get on.   Btw, having the windows open won't help much!

P.s. See page 12 for lever info:

ac-setup-and-test-manual.pdf

P.s. Your wiring is a little untidy.  The jack should still fit in the car fine:

P.s.  The blue clips on the hoses are meant to be taken off after they are crimped.  Clip off very carefully with sharp side cutters.

Jon, can you do me a favour and email me a pic of your install (of the whole frunk area so we can have a template of what an ideal install looks like from a neatness perspective?  Also can you email me the instructions as the link above is broke / this forum won't allow you to display it.  Sorry being lazy :huh:.

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Approx how much frunk space do you lose with this?  I like the older porsches as I can fit two sets of golf clubs in there.

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11 hours ago, cafe_racer said:

Approx how much frunk space do you lose with this?  I like the older porsches as I can fit two sets of golf clubs in there.

None at all.  Eveything is under the carpet.

Will post up some wide shots of the frunk tomorrow.

Nick, there's a link to the page with all the manuals in my Chris Harris post above.

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Hi Jonny

I'm looking at buying an ex. tarmac rally car running extractors and no heater boxes. Can the system incorporate  hot air using some sort of electric heat source such as this? - https://www.ebay.com/itm/600W-12V-24V-Car-Truck-Fan-Heater-Heating-Warmer-Windscreen-Defroster-Demister/362179899302?hash=item54539aafa6:g:N14AAOSwz~paKORs&vxp=mtr

Cheers and thanks

Cam

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How many amps do you really need to run a decent heater?  Is it more or less than running a decent AC compressor?

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4 hours ago, Coastr said:

How many amps do you really need to run a decent heater?  Is it more or less than running a decent AC compressor?

You need more power for heat and ideally aroind 100A.

With heat, power in equals power out.  An absolute bare minimum is 800W per person which translates to 50A in practice.  To put this into context a small heater from a classic Mini is aroind 3000W.

With AC, the compressor has a 'coefficient of performance' of around 2, meaning that you get 2W of cooling for every 1W of power in.  We have looked at running the compressor as a heat pump but the plumbing and valves involved are way too complex.

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Wow ok.  I’m giessing any solution is going to be a case of ‘ok heat’ rather than truly replacing the blast furnace you can get from the heat exchangers if they are working propely.

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On 2/28/2018 at 8:18 AM, Pork Chops said:

Jon, can you do me a favour and email me a pic of your install (of the whole frunk area so we can have a template of what an ideal install looks like from a neatness perspective? 

img_5225.jpg

 

img_5224.jpg

img_5222.jpg

 

As you can see, I run my hoses inside the car.  I do get a bit of condensation, but I'm always tinkering with the car so this is better for me.  The hose from compressor to condenser goes through two factory holes.  First is the lowest grommet in the lower inner wing.  The other is a hole in the front bulkhead.  No extra holes drilled in my car at all.

The wiring goes up the inner wing with the original wiring.  You can shorten some of the harness to make a proper tidy job.

Carpet goes over the top.  We are forever showing people the AC so it never stays in for long!  At the front is a VW T25 washer bottle with built in electric pump.

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Thanks Jon. My heater controls are apparently fixed now and the car is currently being tuned. Things don’t move fast in the Porsche world...

I’ll update the thread soon as I get the car back and let’s hope there is still some hot weather left in our Autumn!

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Hey guys, I got my car back and the AC appears to work well.  All the dash sliders now work as they should and when set right the cool air flow nicely from the centre dash vents.  It was only a short drive so can't say how it cools the cabin overall.  My impressions of the system are that it's not on the same level as a modern AC unit (covered earlier in the thread) but that it's likely to be better than the factory AC and certainly a lot better if your system has not been well maintained.  If you're starting from no AC then the value proposition gets stronger as the install is so much simpler as it's all up the front of the car and it looks so much neater without the compressor in the engine bay.  I'll give more feedback once I've had more seat time which won't be for a few weeks now as I'm away from the car over the school holidays.

Happy Easter all.

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16 hours ago, Pork Chops said:

Hey guys, I got my car back and the AC appears to work well.  All the dash sliders now work as they should and when set right the cool air flow nicely from the centre dash vents.  It was only a short drive so can't say how it cools the cabin overall.  My impressions of the system are that it's not on the same level as a modern AC unit (covered earlier in the thread) but that it's likely to be better than the factory AC and certainly a lot better if your system has not been well maintained.  If you're starting from no AC then the value proposition gets stronger as the install is so much simpler as it's all up the front of the car and it looks so much neater without the compressor in the engine bay.  I'll give more feedback once I've had more seat time which won't be for a few weeks now as I'm away from the car over the school holidays.

Happy Easter all.

Excellent. Same as my thoughts after doing it on e9. Will be looking at it in next 12 months for 911!

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Thanks Mr Chops for what I think is a very fair and objective assessment, also in line with our test results.   Several 993/964 owners have said the A/C in my SC is better than their cars,  but I agree that totally modern levels of cooling are hard to reach.

Essentially, we have no problem cooling the evaporator (typical output being 8 deg C @ 35 deg C ambient with a full fan) and have improved the airflow as best we can within the constraints of the bodyshell without having to do major surgery or create 'Frankenaircon'.   I can't be doing with bolt on dashboard vents and other junk - not our style.

The remaining limitations are the vehicle itself.  It has next to no interior insulation and non UV reflective glass in a fairly big glasshouse.  There is a pretty impressive 'non gangster' UV film called 3M Crystalline in very light grey with 50% UV reflection.  I'd be doing that if I lived under your sun.

A special note to Mr Chops regarding cabin cooling:  Stop the elbows out posing and shut the windows already!  :D

 

 

 

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Looks like it is still a work in progress?  Has anybody else had any experience with the classic retrofit electric system?  

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1 minute ago, DJ said:

Looks like it is still a work in progress?  Has anybody else had any experience with the classic retrofit electric system?  

Hey DJ, not sure I'd describe it as WIP.  Essentially my situation was complicated by dash sliders that didn't work properly and an inadequate alternator.  The car needs to have both as a base before the system will work properly.  Mine is all good now, but of course the hot weather has now passed and seat time is limited.  I think the decision tree is like this.

Got factory AC?  Accept as is, upgrade / repair factory, or go something different

Got no AC?  Continue on, install trad AC system, install something different

I use the term something different as I don't know what the other options are so don't want to pretend I do.  I reckon the Classic Retrofit system does what it says on the packet, is very neat and unobtrusive, is all in the front of the car, leaves the engine bay without a dirty great compressor.  I'm guessing install costs are accordingly lower.

Better than nothing?  You bet.  Better than your factory system?  Almost certainly.  Better than a brand new traditional system retro fitted?  I'm not sure about performance but it's a lot neater and simpler.  Are there other electric cooling systems on the market?  Not sure personally as I've not looked.  Do your own research but take a good look at the hard data from R&D CR has, then compare everything else to it, assuming the other options have gone to the bother.  

All the best.

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Thanks Pork Chops.  I am at very early stages of research - all of your info is really helpful.  

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Looking at some air cooled beauty and one of the conundrums is AIr Con. It’s a box tick as the mrs won’t travel without it and I want to use the car both for SMT’s and weekend drives with the mrs (also helps get her on board the purchase)😏.

a lot of early cars and imports in the price range I want to spend don’t have AC. Reading all the threads there are a few options with kits etc but DIY is not my strong point from a time and space.

Keen to get feedback on your experience @Pork Chops a year or so on or others that have done the retro fit of an AC system in particular the AH kit or the Retro electric. I note that there is a 3 month or longer wait on the Retro electric kit. Outside if the kit can anyone give indications of what the install cost were if you had it done by a 3rd party?

My conundrum is do I go for the right car potentially with no AC and build in cost of retrofitting (have found a sweet 3.2 like this) or hold out for one with AC which still may need some upgrading. 

Keen on thoughts of those that have done either.

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28 minutes ago, Tips said:

Keen on thoughts of those that have done either.

My 2c

Buy a 996 as I strongly believe you will never have satisfactory a/c (for the Mrs) in the earlier models. 

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19 minutes ago, Tips said:

Looking at some air cooled beauty and one of the conundrums is AIr Con. It’s a box tick as the mrs won’t travel without it and I want to use the car both for SMT’s and weekend drives with the mrs (also helps get her on board the purchase)😏.

a lot of early cars and imports in the price range I want to spend don’t have AC. Reading all the threads there are a few options with kits etc but DIY is not my strong point from a time and space.

Keen to get feedback on your experience @Pork Chops a year or so on or others that have done the retro fit of an AC system in particular the AH kit or the Retro electric. I note that there is a 3 month or longer wait on the Retro electric kit. Outside if the kit can anyone give indications of what the install cost were if you had it done by a 3rd party?

My conundrum is do I go for the right car potentially with no AC and build in cost of retrofitting (have found a sweet 3.2 like this) or hold out for one with AC which still may need some upgrading. 

Keen on thoughts of those that have done either.

First up AC and power steering are 2 things you can improve or add to an older AC car that transform how useable they are.  I highly recommend both and good for you and the Mrs and relations generally.  I cannot compare the CR system with either factory or other aftermarket ones but I can say I'm very happy with the CR product which works very well. For my money I've no appetite to go installing trad systems with lines running front to back, multiple condensers tucked all over the place, evaporators in the passenger footwell, and an old knackered blower in the frunk.  Not to mention the ugliness and weight of the trad compressor in the engine bay.  I've just ripped out all this stuff out from my Rally Cab and have a 3rd CR AC system ordered to replace it.  CR also have a hypo high output alternator which would probably significantly improve the performance of their AC system as their system only draws the power it can, but I've not bought that yet.  If you're in doubt then consider that this system is used in the Singer DLS and by Ruf, among others.  Install time is estimated at 8 hours once the installer is experienced but I'd suggest you talk to the installer before budgeting that amount as they may disagree!  Lastly I like the idea of having some cool clever cutting edge stuff in my car.  Porsche people can be stiflingly conservative sometimes, so anything to break the mould....

2 minutes ago, P-Kay said:

My 2c

Buy a 996 as I strongly believe you will never have satisfactory a/c (for the Mrs) in the earlier models. 

A bit of 996 love!  I agree with the point that no matter how good any retrofit AC system is on an older car it's still no match for modernity.  But not everyone loves a 996 like you and me PK!

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Thanks PC and yes PK 996 acquisition is slated for daily duties and probably the easier buy atm. Thanks guys appreciate the feedback.

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