Jonny Hart

Sure, let’s talk about a few things. I’m already quite far ahead on the lightweighting but I’d appreciate your input. You are clearly thinking from the manufacturers point of view. I am coming from the driver perspective. For example I have spoken to LMP car builders and the homologated AC has a fundamental flaw so bad that the driver and crew hate using it. Mostly I get calls from drivers or their mechanics. We are supplying an AC system which is being fitted to a genuine factory 911 ST (raced at CLM). You would have thought that would be absurd.

Many weekend racers want a bit of heat to warm the feet and keep the screen clear. It’s our number one enquiry at the moment. Have you driven a 911 without heat? I have and it’s horrible. If it’s remotely cold outside it never gets warm through the rear bulkhead. Your feet especially are freezing. Everyone said AC for race cars was silly too. We’ve just done a low drag E Type, a BMW M3 touring car and GT40. Just yesterday had an enquiry about a Lambo Hurrican GT3 and Carrera Cup.

No problem. Read my first post on this thread. The battery has enough reserve to carry the extra demand for a limited time and the software we have developed maintains and controls the current so as to not out gun the alternator. When the engine picks up the battery is recharged. The first iteration is already on the DLS...

It’s mainly for people running headers. The US is the main market where race headers are very cheap (<$500) compared to say SSIs. It’s a lighweight thing too, SSIs are heavy and at the back. Electric heat is light and at the front. Lots of states (like Texas) are so hot in summer that heat is not factored into a build but there are still cold periods of the year. You then have the 914/6 brigade where their isn’t really a viable heat exchanger solution. The wider market is race cars in general.

@Busybee Let me translate into your world. I just googled that a tea candle generates 30W of heat. It should be quite apparent that 150W is not enough to heat a car. I now have an image of you sitting in a car with 5 candles burning! A 1600W heater is the equivalent of 53 candles. Apart from the fire hazard, you could imagine this making a difference but 5, not so much.

Can someone move this to a new topic? Electric Heat?

^ Conveniently, engines already have such a generator, it’s called an alternator!!! It’s kind of why I’ve spent the last 2 years of my life developing a decent one!!!! At the end of the day it’s energy. Any wheeze based on switching or storing to somehow get energy from nowhere is just as silly as a ‘perpetual motion machine’. Storing energy however has potential. It is a realistic option to have a mains powered storage heater in the car that is heated overnight for a cold morning but it will not last forever. I believe some electric cars may store heat whilst on charge. Btw: Any heater that runs off the cigarette lighter is limited by the cable rating which is 15A minus a safety factor so say 12A. 12A x 12V = 144W We are running 110A cable which is the same thickness as a typical jump lead cable. If you want to try an experiment, grab your missus hairdryer. Most are 1800W. If you put it on the LOWEST heat setting, that is usually 600W. Try sitting in a cold car with it.

6 years ago I ran 800W in my own car. Anything less than 10 degrees C outside was pathetic. If you devoted all of that to the screen that would demise but there is zero chance of any cabin heating. To put this into perspective. If you’ve ever been in a classic mini and remember the crap little heater. Well that is 2200W right there....

^ Because the the plumbing would look like a snakes wedding. There is a common misconception that you just ‘run the pump backwards’ and you get heat. Not so. Pumps don’t run backwards! What they actually mean is that you reverse the cycle of refregerant. The refrigerant has to be pumped the other way round the circuit Since the pump cannot actually run backwards this means a whole bunch of extra valves and hoses to switch over. Effectively, the evaporator and condenser have to swap roles. A secondary problem is that evaporator coils are designed to cool. If you tried to use an evaporator as a condenser (to emit heat) it would not be very effective. For this reason most reverse cycle heat pumps in cars (e.g. Prius) have both an evaporator AND a condenser in the blower box. There is no way you could fit both in the limited space of a 911. Here is the plumbing diagram of the Prius. Can you imagine having to install all of this lot? It would be a massive support headache for us also! This is what that lot looks like on a Pruis:

2.6 kg for Webasto 2000 STC unit when I last checked. Not convinced it is lighter than the electric heaters. I’m aiming for under 2kg.

Now that is funny! 😆😆😆

^ True. The ‘trouble’ with heat is that: electrical power in = heat power out.* We’ve worked out that the minimum acceptable heat in a small cabin is 1600W, so you’re looking at around 130A to have the heat on full chat. Even our 175A alternator ‘only’ puts out 80A at idle so we need to incorporate the self regulation similar to what we do on the electric AC. In other words, when the car is at idle, the heater will need to know if it is draining the battery and self limit. This means there’s a bunch of electronics to design and firmware to write... * with AC, a compressor has a 2x coefficient of performance. For every 1 Watt of electrical power you get 2w of cooling. P.s. I met the ‘other’ fuse panel guy in the US. There is no bad blood between us. Still don’t like the plastic screws on his version though.

Given that the ECU switches ground, I’m fairly certain all you need to do is wire the ECU to 85 and leave everything else as Porsche intended. Effectively the ECU output is the same as lifting the CIS airflow plate. This causes the pump to run with the ignition in the ON position which is what you want isn’t it?

IB gear linkage cover is under carpet. No hole. Only early cars have the cover on top Carpet goes over the handbrake. You’d normally have the autoheat unit or a rubber boot to finish. The boot in mine is from an earlier car with twin heat levers on the same side.

Proper nasty. Glad you found the issue.