That insatiable 'need for speed'

[Deleted]

Hi guys

Now, this has nothing to do with model engineering per se but does involve some specialist knowledge which I'm sure can be found here. This, of course, relates to my car and my constant mission to improve performance. I have an idea which I have since found out that it has been done by Dodge in their Demon and was also done by Ford in the Mustang Mach 1 concept car, so it's not that crazy an idea.
I have recently been looking into improving the cooling of the air charge from the intercooler, the intercooler fitted to my car in standard form was good enough for 400bhp, I can testify to this during my experience with modifying these cars, for those who don't know I drive an '86' Porsche 951. Ok, so the intercooler, being a Porsche it's not just a matter of bolting on a great big rad and sticking it in a big hole in the bumper, Porsche are much more refined than that. The 951 body shape has been designed to create a low pressure point on the nose panel and just below the front apron, in between this are two openings, one for air to the Radiator and the other to the intercooler through a very well designed ducting, such a design is known to be up to 50% more efficient than the traditional, big rad in a big hole approach, ala, most intercooler designs.
Ok, so moving on, I have then looked at 'water spraying' the intercooler to make it even more efficient, this is a proven way of reducing the charged heat and in fact, is fitted to some cars and indeed was used by F1 in their early turbo days with 1500cc engines producing over that number in BHP. There are a number of universal kits out there with full control units to automate the use of the spray.
I have bought a cheaper kit with no controller or temp sensor which I plan to make myself, or should I say I hope my son will design/make it. I have already arrived at where to install the two nozzle jets and then gave thought to the water tank. A tank comes with the kit and the most obvious place to put it would be in the boot where it would remain cold and then route the hoses around the part of the engine bay with the most airflow to get the coldest water possible when sprayed.
At this point, I thought what about utilizing the A/C, could I run the water through the A/c in a way that didn't freeze it or effect flow too much. If I did this I could drop the idea of fitting a separate water tank in the boot and use the washer bottle which is very large on the 951 (944 turbo) and of which the bottom section sits very low and could have cool air directed to it easy to begin with the cooling process anyway.
It was at this point while researching suitable components that I discovered the Dodge Challenger Demon with it's 'Chiller' system which basically does the same thing, runs water through the A/C to cool the air, whether this is water onto the intercooler or through the inlet I didn't look deep enough into. There are many ways of using water to greatly improve engine performance, both inline with an intercooler, direct into cylinders or indeed in through the air inlet direct onto the turbo, such ideas were first used during WW2 for fighter aircraft.
Now I am already aware of inlet charge coolers which basically push air through a barrel which water passes around to reduce the air temp and thus increase the density of the air resulting in a bigger 'bang'. On looking at these reasonably small items, instead of air being passed through the middle could I route the A/C gas through it thus reversing the charge cooler principle, that is I am now cooling the water passing around the barrel with the gas through the middle.
So to you enterprising engineers, can you foresee issues in freezing the water and if so can you suggest the best way of avoiding this, are there existing A/C components that I could adapt for my purpose?

To show the overall layout, this picture shows the space available...the A/C pipes can be seen just to the left of the coolant tank on the right as we look at it. They can be seen going along the top inner edge of the struct tower and disappear into the cabin. Forward from here they go down and come out below the coolant tank (under the large inlet pipe seen disappearing into the wing) where they connect to the drier, there is some space under there although part of it needs to be kept clear for when the headlights pop up. The tank on the left-hand side is the washer bottle, this is massive, it drops down very low into the car feeding both the windscreen water jets and also the headlight washers fitted in the bumper, this would be an ideal water feed if I can keep the water cool. In general, though there is still a lot of space still available to play around with under the bonnet.



Ok, not ME per se but still something that I think can be resolved and perhaps of some interest to you learned folk...any suggestions on what i need to design this 'chiller' tank would be most welcomed...over to the panel...

Pete

[andyhigham]

Before complicating things with the A/C. I have worked with industrial sized versions known as "Adiabatic coolers"
The water itself does not cool the intercooler, the evaporation of the water does the cooling "latent heat of evaporation"
This is one of several we installed last year, the pipe along the centre carries the spray nozzles, the air is drawn upwards through the heat exchangers by the fans on top
20190525_172016 by Sigma Projects, on Flickr
20190526_174840 by Sigma Projects, on Flickr

[Deleted]

Hi Andy

Yes I spoke with my son after posting and he's been trying to explain this to me... he said that I don't need the A/C...just the water mist alone will reduce the temp, yes some racers throw ice in the tank but I don't need to worry about that. I'm not experiencing any detonation and not racing so WOT is not going to happen often on the road. Just sprayed water will be good enough for my use, it will reduce the charged air temp. He reminded me of the test by blowing on your hand, it will feel warm, now wet the hand and blow again...no warm feeling...theory proved...

Pete

[andyhigham]

For even more cooling use a water / alcohol mix, injected after the intercooler

[andyhigham]

Liquid nitrous oxide also cools the charge but you need to inject more fuel. Downside is your combustion chamber temperature increases, upside is MORE POWER. How much more? Depends on how much Nitrous you put in, up to 250+ BHP extra

[Deleted]

Yes NOS can add big power...pretty safely too. My son has a friend with an old 924 with a V8 swap, twin turbo, charged cooler and 200bhp NOS jets. .it's a proven 10 sec 1/4 mile car, bright yellow with the GTR body kit...last time I saw it was some years ago at a Porsche meet at the Ace cafe...he left lots of rubber on the tarmac that night...

[JonL]

I think its the phase change from liquid to gas that really drags the temperatures down. I did some experiments with my turbocharged MX5 and injecting water (which I clumsily did using a standard injector just after the throttle butterfly slaved to one of the existing injector drivers to give variable flow depending on engine speed and adjusted the pressure for overall control) and it allowed me to run much more advance and therefore get a big leap in power. Out of interest I also tried this on a normally aspirated MX5 and found although I could run lots more advance the amount of power remained pretty much the same. I've since been told its quite possible the water vapour was "taking up space" that could have been used by combustable gases, something which forced induction overcomes.

[Deleted]

Jun 6, 2020 19:41:00 GMT JonL said:

I think its the phase change from liquid to gas that really drags the temperatures down. I did some experiments with my turbocharged MX5 and injecting water (which I clumsily did using a standard injector just after the throttle butterfly slaved to one of the existing injector drivers to give variable flow depending on engine speed and adjusted the pressure for overall control) and it allowed me to run much more advance and therefore get a big leap in power. Out of interest I also tried this on a normally aspirated MX5 and found although I could run lots more advance the amount of power remained pretty much the same. I've since been told its quite possible the water vapour was "taking up space" that could have been used by combustable gases, something which forced induction overcomes.

I think that's more ' direct water injection' which would require a bit more work in tuning. IIRC water cools 6 times more than petrol, with direct water injection there is no need for an intercooler.
The next method is spraying water into the inlet and thus ditectly into the turbine blades, this also can have a big affect on keeping things cool. After that there is spraying a water mist in the front of the intercooler which has a pretty big affect on the charged air going into the throttle. This is the method that I will be using, my car has a very efficient ducting that directs the air from the opening above the number plate into the intercooler, this is a 'ram air' as it's at the lowest pressure point on the car, this greatly increases the intercooler's efficiency in it's own right.
I plan to fit two water jets, one either side of the intercooler ducting which will generate a mist directly in front of the intercooler which will bring the charged air temp down significantly.
It's other job is to stop the heat soak that occurs each time the throttle is closed, this will improve
throttle  response . The heat that is generated each time the throttle is closed after a hard pull is the highest that the intercooler sees, perhaps as much as 20c.

And then there's gas as Andy stated, NOS/CO2,, I want to avoid those as they don't last long before needing a refill, plus water is free...

Pete

[andyhigham]

Tractor pulling with diesel engines take water injection to the max
They inject a similar amount of water as fuel, it cools the charge and boosts compression. It's a fine line to tread, too little water and the engine melts, too much water puts out the fire

[andyhigham]

A guy near me drag races a land rover!! YES A LAND ROVER!!
It has a 6 cylinder Cummins diesel engine with 2 stage turbo charging. manifold boost pressure is 80PSI

[andyhigham]

His manifold pressure is the same as most of our model loco boilers yet it does not need a hydraulic test

[Deleted]

Jun 6, 2020 21:25:00 GMT andyhigham said:

Tractor pulling with diesel engines take water injection to the max
They inject a similar amount of water as fuel, it cools the charge and boosts compression. It's a fine line to tread, too little water and the engine melts, too much water puts out the fire

Yep, hence my comment on it needs more tuning....my mods will be very amaturish in comparison. I have been reading a lot about the first use of water in engines...very interesting stuff, all dating from WW2 and the need to improve fighter aircraft performance at high altitude. All old school stuff, keep pushing the envelope until things stop blowing up,
It seems car engines have taken things much further, from dragsters and hot rods to production cars like the Dodge Challenger Demon...840bhp from what's basically a big saloon is crazy power...

[andyhigham]

My Kawasaki 1400 has 200BHP at the command of my right wrist. It is a pussycat, the most sensible bike I have ever ridden. The power is controllable, riding around town is a doddle, country roads are effortless, give it a handful and from a standing start 200mph comes up in a mile.
My favorite car I ever had was an old 1990 Lexus LS400, 4 litre dohc V8, floor it and it threw me back into the seat, I could get 29.5mpg on motorway. When I sold it 22 years old with over 300000 miles on the clock it was still taut and smooth with a silent engine. Lift the bonnet and all that could be heard was the ticking of the injectors

[simplyloco]

Jun 6, 2020 22:02:50 GMT andyhigham said:

My Kawasaki 1400 has 200BHP at the command of my right wrist. It is a pussycat, the most sensible bike I have ever ridden. The power is controllable, riding around town is a doddle, country roads are effortless, give it a handful and from a standing start 200mph comes up in a mile.
My favorite car I ever had was an old 1990 Lexus LS400, 4 litre dohc V8, floor it and it threw me back into the seat, I could get 29.5mpg on motorway. When I sold it 22 years old with over 300000 miles on the clock it was still taut and smooth with a silent engine. Lift the bonnet and all that could be heard was the ticking of the injectors

My old SL500 was similar. There ain't no replacement for cubic displacement!
John

[andyhigham]

I also at one point had a 4.6 litre Rangy best mpg I ever achieved was 15, around town it was 10-12

[Deleted]

I think you might enjoy driving my 951 Andy.. she is very quick, pins you to the seat. Needs little throttle used to be accelerating very quickly. Being an 80's car there's no limiter...I haven't driven her flat out, was close going to Le Man some years ago, back then she had less mods and only 280bhp..GPS still recorded 174mph and we were still acceletating hard at the time, backed off as a lorry was joining the mototway from a slip road. Today, she is at least 400bhp at the rear wheels and will redline in 5th...In the US there are cars with a similar power output to mine that have been recorded at 200+mph. The Porsche 951 is a very special car, a true throughbread, stated by Porsche race engineers as one of the best cars they ever made, in fact Porsche West London when awarding my car best in the show at their concores offered to buy it from me. It's also one of the few cars that was designed as a race car before being produced as a road car. My particular year model 1986 is homologated certified, the only year which qualifies it for historic racing, she's the lightest too, 100kg lighter than the later models.

In case you hadn't guessed, I love my car...

Pete

[Deleted]

Oh..talking mpg, I can only give you what's in my official handbook...44mpg at 56mph and 48mpg at 70mph...of course she won't be anywhere near that economic today, hell, the injectors are more than double the flow...