Jump to content
SAU Community

Recommended Posts

It takes a few (like low single digits) horsepower to drive a car AC compressor. If you can gain more than that few HP back, it should be nett positive. It would seem like an interchiller should be able to be worth more than a handful of horsies.

Most importantly, it should be run when the engine load is less than 100% (ie, when there is spare power available, going unused at the tyres, when whatever power is used to run the AC won't take away from thrust.

 

I can see it being logical for pre-cooling the intake charge before it's actually being used. Kind of like dumping dry ice on an intercooler directly....

I.e waiting in line for your start at the drags, or driving around before you want to chop someone on the highway lol, and it would be a net benefit for @mlr's use.

However for say some dickhead who decided to supercharge his LS in a skyline, then wanted to do 30 minute hotlapping sessions, at 100% throttle for extended periods well and far beyond a drag run, in a very limited packaging situation with IAT's being extreme, (70+++). 

I can still see the subjective benefits of generally keeping IAT's lower rather than higher which is more than just pure power tbh. Keeping it lower makes sense. But I'm still curious as to whether it would actually increase RWKW in the long run and/or actually still _work_ when the engine is under load like that. Would the motor just generate too much heat for the AC system to overcome?

On 18/03/2022 at 10:11 AM, Kinkstaah said:

I can see it being logical for pre-cooling the intake charge before it's actually being used. Kind of like dumping dry ice on an intercooler directly....

I.e waiting in line for your start at the drags, or driving around before you want to chop someone on the highway lol, and it would be a net benefit for @mlr's use.

However for say some dickhead who decided to supercharge his LS in a skyline, then wanted to do 30 minute hotlapping sessions, at 100% throttle for extended periods well and far beyond a drag run, in a very limited packaging situation with IAT's being extreme, (70+++). 

I can still see the subjective benefits of generally keeping IAT's lower rather than higher which is more than just pure power tbh. Keeping it lower makes sense. But I'm still curious as to whether it would actually increase RWKW in the long run and/or actually still _work_ when the engine is under load like that. Would the motor just generate too much heat for the AC system to overcome?

For NA I couldn't see the cost being justified, you are just dealing with ambient temp and "possibly" a small bit of heat transfer 

But, I've done a little reading into IAT, CAI and heat transfer 

The IAT varies greatly dependant on the sensor location, and I cannot really see the air being "heat soaked" for the fraction of a second that the air is travelling from the CAI to intake valves of an NA engine.

5.7 x (6000 rpm ÷ 2) = 17100 litres of air a minute at 6000rpm (very roughly) #efficiency 

Thats 17100 ÷ 60 = 285 litres a second is getting sucked down its throat 

These rough calcs do assume 100% efficiency though, but even at half the volume, that is still near 150 litres a second.

What size is your intake and how long is it?

I'm guestimating that the air speed is exactly "really really bloody fast", too fast to heat up the ambient air to any noticeable degree....

 

For reference my post blower AIT goes up pretty much with the coolant temp, to settle at around 50°c, when its sitting in traffic or after a pull it gets to around 70°c, but after I shut the car down, it goes from 50°c to 70°c fairly quickly, but once the car is running and moving again it slowly comes down to 50°c

See pic for where my IAT sensor is in relation to the engine, it is basically bolted to the head, and this is why the spacers "lower" the IAT temp, it is really only stopping heat soak from affecting the sensor, actual IAT hasn't changed at all, from my research spacers alone seems to lower IAT between 10 - 20°c, the interchiller can get another -20° c

20220318_112254.thumb.jpg.ab6a47604b8e25f254062e1cf8d8640d.jpg

Meh, math and science make my head hurt

 

  • Like 1

With respect, if you can get more power our of colder intake air than the heat pump takes to drive, lots of racing classes would be doing it.

Also, while I'm feeling a bit ranty, you don't get "4kw" of heating or cooling power for 1kw input on a heatpump. You get 1kw. It's just that a radiator is only 25% efficient as a heater. Someone in marketing just decided to compare an apple to an orange

On 3/18/2022 at 11:36 AM, mlr said:

The IAT varies greatly dependant on the sensor location, and I cannot really see the air being "heat soaked" for the fraction of a second that the air is travelling from the CAI to intake valves of an NA engine.

In my experience, this actually does matter - The position of the IAT sensor doesn't matter with regards to the temperature when I have tested. I've tested it in the tube next to the TB, in the tube at the start. In the airbox, inside the pod filter, as well as in the manifold!

The biggest change was ducting cold air from the outside and making a sealed system. I agree - The air will not get heat soaked by the time it gets through the motor, but it will suck already hot air from the engine bay as a preference if it can, because that hot air is closest to the filter/intake.

(this is in N/A land). You can't duct your already compressed/hot air to overcome this, because well, it's hot due to the fact it is boosted. I now reguarily see air temps that are 0C hotter than outside. Went for a drive recently and my IAT's were about 12C while beating the hell out of the car. Ducting really does work. Removing the duct and letting it grab heat from the wheel well resulted in 38-40C air because oil cooler is hot, brakes are hot, and it'll grab the nearest air it can (round headlights and shit which is semi-engine bay hot)/through the rad hot.

Again not super relevent to your boosted setup 😛

On 3/18/2022 at 11:47 AM, Duncan said:

Also, while I'm feeling a bit ranty, you don't get "4kw" of heating or cooling power for 1kw input on a heatpump. You get 1kw. It's just that a radiator is only 25% efficient as a heater. Someone in marketing just decided to compare an apple to an orange

No. Not true. The physical work put into the compressor is not converted into heat. It is converted into the transfer of heat from a cold location to a hot location. The heat comes from the environment around one of the heat exchangers and therefore violates no laws of thermodynamics. The work is sneaking the heat past what you think are the laws of thermodynamics because you're drawing your energy balance boundary too close to the heat pump.

Quote from: https://www.eec.org.au/for-energy-users/technologies-2/heat-pumps

Quote


Heat pumps can seemingly defy the laws of thermodynamics, because they can deliver much more than one unit of heat (or cooling) per unit of electrical energy consumed. This is because they are extracting heat from around the evaporator and dumping heat to the environment around the condenser. Electricity is being used to concentrate and shift heat, not to produce heat directly as in a resistive electric radiator or fan heater.

 

 

I wasn't at all suggesting that a chiller would be good for NA applications. Boosted applications are obviously even more sensitive to IAT and are also able to create more IAT so it makes sense to consider chillers for boosted applications first. I rather explicitly said that they would have to be useful at times when you are not using 100% of the engine's available power (ie do not need all the available power, owing to traction limitations, braking into corners, etc etc) and therefore they would likely be useful in more applications than people would give them credit for, because most people only think about the WOT case. They are certainly used in drag racing in the pre-WOT time, for exactly that reason. There's no reason why they could not be similarly applied in circuit or rally or some other types of racing, provided there is enough time off WOT to gain some of that power gap.

 

So, look at the math. If a car AC compressor takes about 3kW to drive, and can yield (conservatively) 4x that in cooling power, and you have air post intercooler (assuming a reasonable boosted application already) at say 50°C ....bugger it, let's say it's bad and you really need to think about a chiller, so.... 80°C, and you're making say 500 engine HP and using 350 cfm to do it. That 350 cfm is about 0.2 kg/s. Air spec heat capacity is about 1 kJ/kg.K (nice and easy). So, 12kW will decrease that air temperature by nearly 60°C. So, from 80°C to 22°C. ON A CONTINUOUS BASIS.

So, even if the car AC comp's leverage is only 3:1, you still get like ~45°C drop. And if it's better, like 5, you get really cold air.

On much more powerful engines, you would need a much bigger AC system. That's obvious. But at 500HP it already seems feasible with what's already lying around.

The real question becomes, how much more power can you make from air that is 50+°C cooler in a 500HP engine? It only needs to be >5HP to be positive, but you wouldn't consider all the weight and complexity for almost no extra power. You probably wouldn't even consider it for ~10HP. But, if it were worth say, 10% of the 500HP base, then it's probably looking attractive. And with the detonation threshold at 80°C being pretty scary, that might actually be possible. It would be even better if the system were well managed and could run the compressor more when there is spare power available and bank it in cold coolant so that you can actually use even more cooling power than the system produces naturally for short periods.

I think there's something in it and it just requires some dev work to make decisions about how big and how controlled and so on it needs to be.

  • Like 3

For me it isn't about making more power, it is about keeping the power I have

I believe my ECM starts pulling timing from 50°c IAT and over that it pulls more pretty hard

I'm stagging at the drags with 70°c IAT, at the big end I'm at 80°c

Hence the car goes like a cut snake below "around" 50°c IAT, from 60-70°c IAT it pulls timing that hard that it is obviously noticeable from the drivers seat that the power has dropped its showbags

I don't believe a interchiller would be on any use on a circuit car, maybe, I don'tknow, and for "big" powered drag cars a reservoir is required to ensure that there is enough low temp coolant available for a full run

A Interchiller is just like an ice box, the benefit of this is you don't need to replace the ice, just idling down the return road will bring the coolant temps back down

For the street, it will always be super cold.

There are also ways to add efficiency to my 20 year old AC system by replacing and adding modern condensers, this also helps drop the intercooler coolant temp, and is relatively cheap to achieve 😀 

  • Like 1
On 18/03/2022 at 2:56 PM, Kinkstaah said:

In my experience, this actually does matter - The position of the IAT sensor doesn't matter with regards to the temperature when I have tested. I've tested it in the tube next to the TB, in the tube at the start. In the airbox, inside the pod filter, as well as in the manifold!

The biggest change was ducting cold air from the outside and making a sealed system. I agree - The air will not get heat soaked by the time it gets through the motor, but it will suck already hot air from the engine bay as a preference if it can, because that hot air is closest to the filter/intake.

(this is in N/A land). You can't duct your already compressed/hot air to overcome this, because well, it's hot due to the fact it is boosted. I now reguarily see air temps that are 0C hotter than outside. Went for a drive recently and my IAT's were about 12C while beating the hell out of the car. Ducting really does work. Removing the duct and letting it grab heat from the wheel well resulted in 38-40C air because oil cooler is hot, brakes are hot, and it'll grab the nearest air it can (round headlights and shit which is semi-engine bay hot)/through the rad hot.

Again not super relevent to your boosted setup 😛

Cool ambient temp air is king 🥶

I would assume that my OEM, slightly modified, airbox would be getting near on ambient temps from just behind the headlight and where there is a hole in the body work for clean air and some plate blocking "most" engine bay heat, there are some improvements that I'm looking at, but it's got a pretty clean fresh air flow

The tricky thing with a top mount blower is getting an accurate IAT reading, actual IAT may be, say 40°c post the blower, but because of packaging and the resultant heat soak of the sensor, the ECM is seeing 60°c from the sensor....

Fun times 🥴

On 18/03/2022 at 5:26 PM, Dose Pipe Sutututu said:

You could chemically intercool the karnt, meth spray dis dat.

Cheap, but logistically troublesome with refilling and stuff, I would put in the same boat as an ice box

Possibly fine for turbo, or centrifugal front mount, but not for a top mount PD blower, shooting a mist at rotors isn't recommended

  • Like 1

Wendsday: Drove to Goulburn to visit daughter for a few days, nice

Friday AM: Drove from Goulburn to Canberra to do some training, nice 

Friday PM: Went to Costco in Canberra for fuel for the trip back to Sydney.......cranks over fine but car wouldn't restart......pushed car away from pumps.....still wouldn't start......popped bonnet....looks good.....wobbled wires..... still won't start.....got angry....rang NRMA who I am not a member of......$560 later NRMA arrive......maybe Crank Position Sensor......called "mobile mechanic" no LS1 CPS in Canberra.....of course......NRMA tow car back to local military base to park it up and await the new day....and over night parts from Sydney...

Today: Awaiting mobile mechanic to arrive sometime today with new a CPS

Now: Hoping that it is a CPS....

SYMPTOMS 

Cranks fine

Tries to fire, but doesn't 

No tachometer signal

Thank god for mobile mechanics

It was a simple fix

Remove starter motor, R&R CPS

Put it back together 

Pay stupid amounts of 💰 for simple fix

Win

Sydney, here I come

Well soon.....the car spent the night under a tree where all the birds who have diarrhoea live, so it will need a trip to the wash point first

20220326_093617.jpg

  • Like 1
  • Haha 1

Nope

Car didn't start, the new "tridon" sensor is faulty

Mechanic went off looking for another CPS and luckily found another, different brand though, which could be good, or bad...at least it cannot get worse, knock on wood, I probably shouldn't have said that....

The funny thing is the car started before he started working on it

When the CPS sensor dies it stops working when the engine is hot, then works when it has cooled down, for a while anyway, I didn't want to risk a hwy run and possibly get caught out in the middle of nowhere when it fully dropped its showbags 

Meh, what can you do

In other news Jackie seemed a tad cranky after I told her the news this morning

Meh, life would be boring if it was rosey all the time, simple, but boring

Meanwhile 

images.jpeg-2.thumb.jpg.b6e5fd602df859e18602173177762f55.jpg

On 26/03/2022 at 1:25 PM, Duncan said:

hell of a thing not to work out of the box. makes you wonder if it is a wiring issue in the car with an intermittent break...

Na, apparently the sensors are exactly the same, but, they wire the sensors differently for different makes and models

Well, that's what the googles say anyway, and it seems getting the wrong, right sensor is a common issue.

All is well now, it got back to Sydney and is all parked up.

What an epic adventure that was

On 26/03/2022 at 2:33 PM, robbo_rb180 said:

Damn old holdens. Good its sorted and home.
Sure you could write a good book with all your adventures

 

LOL, it's a 20 year old car, stuffs gonna break

If I did write a book you could call it "how to waste money on cars and motorcycles in 999,999 easy steps"

  • Haha 1
On 3/18/2022 at 2:33 PM, GTSBoy said:

No. Not true. The physical work put into the compressor is not converted into heat. It is converted into the transfer of heat from a cold location to a hot location. The heat comes from the environment around one of the heat exchangers and therefore violates no laws of thermodynamics. The work is sneaking the heat past what you think are the laws of thermodynamics because you're drawing your energy balance boundary too close to the heat pump.

Quote from: https://www.eec.org.au/for-energy-users/technologies-2/heat-pumps

Youre confusing differences between amount of energy moved in terms of heat, and power gains here.

 

Just because youve gotten 12kw of cooling from 3kw of input, doesnt mean youre going to gain 12kw of power at the crank. And THIS is where the laws of thermodynamics will come into play.

 

The other part not directed at your comment, more other peoples logic, as everyone above is yacking about, IF the tubing in your air intake has the air go flying past and it doesnt have time to heat soak, how will it have time to cool soak...

 

 

This more goes into actual usable power gains

 

https://buildingspeed.org/2012/04/23/temperature-and-horsepower/

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • See if you can thermal epoxy a heatsink or two onto it?
    • The other problem was one of those "oh shit we are going to die moments". Basically the high spec Q50s have a full electric steering rack, and the povo ones had a regular hydraulic rack with an electric pump.  So couple of laps into session 5 as I came into turn 2 (big run off now, happily), the dash turned into a christmas tree and the steering became super heavy and I went well off. I assumed it was a tyre failure so limped to the pits, but everything was OK. But....the master warning light was still on so I checked the DTCs and saw – C13E6 “Heat Protection”. Yes, that bloody steering rack computer sitting where the oil cooler should be has its own sensors and error logic, and decided I was using the steering wheel too much. I really appreciated the helpful information in the manual (my bold) POSSIBLE CAUSE • Continuing the overloading steering (Sports driving in the circuit etc,) “DATA MONITOR” >> “C/M TEMPERATURE”. The rise of steering force motor internal temperature caused the protection function to operate. This is not a system malfunction. INSPECTION END So, basically the electric motor in the steering rack got to 150c, and it decided to shut down without warning for my safety. Didn't feel safe. Short term I'll see if I can duct some air to that motor (the engine bay is sealed pretty tight). Long term, depending on how often this happens, I'll look into swapping the povo spec electric/hydraulic rack in. While the rack should be fine the power supply to the pump will be a pain and might be best to deal with it when I add a PDM.
    • And finally, 2 problems I really need to sort.  Firstly as Matt said the auto trans is not happy as it gets hot - I couldn't log the temps but the gauge showed 90o. On the first day I took it out back in Feb, because the coolant was getting hot I never got to any auto trans issues; but on this day by late session 3 and then really clearly in 4 and 5 as it got hotter it just would not shift up. You can hear the issue really clearly at 12:55 and 16:20 on the vid. So the good news is, literally this week Ecutek finally released tuning for the jatco 7 speed. I'll have a chat to Racebox and see what they can do electrically to keep it cooler and to get the gears, if anything. That will likely take some R&D and can only really happen on track as it never gets even warm with road use. I've also picked up some eye wateringly expensive Redline D6 ATF to try, it had the highest viscosity I could find at 100o so we will see if that helps (just waiting for some oil pan gaskets so I can change it properly). If neither of those work I need to remove the coolant/trans interwarmer and the radiator cooler and go to an external cooler....somewhere.....(goodbye washer reservoir?), and if that fails give up on this mad idea and wait for Nissan to release the manual 400R
    • So, what else.... Power. I don't know what it is making because I haven't done a post tune dyno run yet; I will when I get a chance. It was 240rwkw dead stock. Conclusion from the day....it does not need a single kw more until I sort some other stuff. It comes on so hard that I could hear the twin N1 turbos on the R32 crying, and I just can't use what it has around a tight track with the current setup. Brakes. They are perfect. Hit them hard all day and they never felt like having an issue; you can see in the video we were making ground on much lighter cars on better tyres under brakes. They are standard (red sport) calipers, standard size discs in DBA5000 2 piece, Winmax pads and Motul RBF600 fluid, all from Matty at Racebrakes Sydney. Keeping in mind the car is more powerful than my R32 and weighs 1780, he clearly knows his shit. Suspension. This is one of the first areas I need to change. It has electronically controlled dampers from factory, but everything is just way too soft for track work even on the hardest setting (it is nice when hustling on country roads though). In particular it rolls into oversteer mid corner and pitches too much under hard braking so it becomes unstable eg in the turn 1 kink I need to brake early, turn through the kink then brake again so I don't pirouette like an AE86. I need to get some decent shocks with matched springs and sway bars ASAP, even if it is just a v1 setup until I work out a proper race/rally setup later. Tyres. I am running Yoko A052 in 235/45/18 all round, because that was what I could get in approximately the right height on wheels I had in the shed (Rays/Nismo 18x8 off the old Leaf actually!). As track tyres they are pretty poor; I note GTSBoy recently posted a porker comparo video including them where they were about the same as AD09.....that is nothing like a top line track tyre. I'll start getting that sorted but realistically I should get proper sized wheels first (likely 9.5 +38 front and 11 +55 at the rear, so a custom order, and I can't rotate them like the R32), then work out what the best tyre option is. BTW on that, Targa Tas had gone to road tyres instead of semi slicks now so that is a whole other world of choices to sort. Diff. This is the other thing that urgently needs to be addressed. It left massive 1s out of the fish hook all day, even when I was trying not too (you can also hear it reving on the video, and see the RPM rising too fast compared to speed in the data). It has an open diff that Infiniti optimistically called a B-LSD for "Brake Limited Slip Diff". It does good straight line standing start 11s but it is woeful on the track. Nismo seem to make a 2 way for it.
    • Also, I logged some data from the ECU for each session (mostly oil pressures and various temps, but also speed, revs etc, can't believe I forgot accelerator position). The Ecutek data loads nicely to datazap, I got good data from sessions 2, 3 and 4: https://datazap.me/u/duncanhandleyhgeconsultingcomau/250813-wakefield-session-2?log=0&data=7 https://datazap.me/u/duncanhandleyhgeconsultingcomau/250813-wakefield-session-3?log=0&data=6 https://datazap.me/u/duncanhandleyhgeconsultingcomau/250813-wakefield-session-4?log=0&data=6 Each session is cut into 3 files but loaded together, you can change between them in the top left. As the test sessions are mostly about the car, not me, I basically start by checking the oil pressure (good, or at least consistent all day). These have an electrically controlled oil pump which targets 25psi(!) at low load and 50 at high. I'm running a much thicker oil than recommended by nissan (they said 0w20, I'm running 10w40) so its a little higher. The main thing is that it doesn't drop too far, eg in the long left hand fish hook, or under brakes so I know I'm not getting oil surge. Good start. Then Oil and Coolant temp, plus intercooler and intake temps, like this: Keeping in mind ambient was about 5o at session 2, I'd say the oil temp is good. The coolant temp as OK but a big worry for hot days (it was getting to 110 back in Feb when it was 35o) so I need to keep addressing that. The water to air intercooler is working totally backwards where we get 5o air in the intake, squish/warm it in the turbos (unknown temp) then run it through the intercoolers which are say 65o max in this case, then the result is 20o air into the engine......the day was too atypical to draw a conclusion on that I think, in the united states of freedom they do a lot of upsizing the intercooler and heat exchanger cores to get those temps down but they were OK this time. The other interesting (but not concerning) part for me was the turbo speed vs boost graph: I circled an example from the main straight. With the tune boost peaks at around 18psi but it deliberately drops to about 14psi at redline because the turbos are tiny - they choke at high revs and just create more heat than power if you run them hard all the way. But you can also see the turbo speed at the same time; it raises from about 180,000rpm to 210,000rpm which the boost falls....imagine the turbine speed if they held 18psi to redline. The wastegates are electrically controlled so there is a heap of logic about boost target, actual boost, delta etc etc but it all seems to work well
×
×
  • Create New...