Originally Posted by Jim-SR
Approximately 3.5% power loss per 20C raise in charge temp......
If you start with 200hp @ 20c, you'll only get around 175 @ 100c.....
(or something like this.......saw it on some sort of Audi sport website a year ago......?:thumbsup:)
Jim, i think if you had an intercooler that protruded from the boot of the car you'd be able to get enough air to pass over it to keep the intake temps low enough without any 'added' weight to a stock turbo setup. Mine has a boot located intercooler. I'm running a standard-ish rev 1 3sgte at 15 psi and when i give it some constant welly on the motorway i'm not noticing less performance as the intercooler warms up.
The mk1 is not exactly the most aerodynamic of cars so i don't think an external intercooler will be introducing any noticeable drag. Have you decided on the engine you want to go for yet and the setup?
There's plenty of ideas yet.
Greg
Have you considered running no intercooler at all, but with water injection instead?:hidesbehi
A well designed water inj system would give ample cooling and the lack of IC piping would give snappy NA-like throttle response!
Granted, you need a reservoir for the water/methanol, but you can place the weight where you need it, i.e. in the frunk or passenger foot well to offset the driver.
I'm sure compressor efficiency is a factor too, I could be wrong, but +100 deg temps would imply the turbo is running outside it's peak efficiency 'map'.
Most of the off the shelf systems make use of a high pressure (expensive) pump, boost switch, high pressure nozzle etc, but what about using the venturi effect from a good old carburetor? Compressed air exiting the turbo passes through the water fed carb and an increase in air speed (boost) picks up more atomised water. Simple and adjustable.
BTW I've ditched my heater too mate, but it's a bloody long winter you have over here!
WI is a much misunderstood beast.....!
I removed my IC on the 4AGZE and used a WI setup (Aquamist).
I just fitted a 0.7mm nozzle initially, but did some experiments with high-speed soleniods, etc, later.
Also tried H2O, and various Methanol / water mixes.
TBH, this is a way forward: the amount of heat absorbed by the evaporation process is huge: adding methanol only improves things (up to a point: then you NEED a standalone ECU......but thats a different ball-game!)
I have had HUGE arguments on various forums on this subject (and CBA to get into any more! lol)
...but the bottom line is it worked for me: the steam cleans deposits from the chamber, the combustion process benefits immensely, and you can advance the timing more, giving more power.
IMHO, injecting a very fine water mist BEFORE the turbo / SC is the way to go...sort of emulates the "driving-in -the-early-hours" effect...!
You could have a 2 stage system: a pre TC/SC spray, and a "det-controlling" stage for when you're pushing the limits......
Most of this needs a programmable ECU, but its all doable..needs mapping, but you CAN ditch the IC....
Mind you, in front-engined applications, where you have the luxury of being able to fit a large FMIC, you're probably better off using one: a properly-specced A2A can be very good, light, etc.............and you'll never run out of H2O......!
(not that thats a problem...when was the last time you ran out of petrol..??!)
a few more interesting replies. if the 3.5% per 20degC thing is correct (its obviously just a generalisation) then in theory id probably only lose 10-20bhp through running a chargecooler off the stock cooling system
so far as running any kind of intercooler or radiator protruding into airflow at the rear, it just isnt very feasible. i wont have anywhere at the rear of the car that i can stand to disturb the airflow, so its essentially front or nothing. the only area at the rear is going to be inside the engine bay with minimal airflow, and what flow there is will be quite hot
water injection may be an option, il be standalone on the ECU anyway, but its a question of whether something that can control the water injection will be within my budget. plus theres the issue of carrying the extra water, it could potentially weigh as much as a chargecooler setup, but also potentially be more effective. a "venturi" system may simplify things to within budget, so that only weight would be an issue
How about a vent on the side akin to the one for the engine, but to allow more air into the boot and onto the intercooler. Then vents at the back of the boot to allow airflow out.
Am interesting to see what you come up with as you are looking at a lot of options and seem open-minded as to a solution. Plus like that you have been so rigorous in keeping weight down. :thumbsup:
Greg
Here's what I meant about a venturi WI system.
I'm sure everyone knows how a carby works, but i found a good diagram. Then I hacked it into a "Hydurettor" WI system haha.
I agree that weight is the enemy. But maybe well-placed ballast can be your friend. I've always thought the AW11 could do with a bit more weight over the front tyres.plus theres the issue of carrying the extra water, it could potentially weigh as much as a chargecooler setup
Alternatively you could use the existing washer bottle with a separate pump (a little methanol on the windscreen won't hurt, will it) so it would be weight-neutral!
Do this...then stick a Spal fan on the core...
Then you'll be able to control the airflow over the rad....
As long as the cold air has a good route into the boot, and the hot air is ducted out efficiently, it'll be very efficient.......:thumbsup:
The other Greg.!
windscreen washer fluid already has methanol in it :)
I've wondered what is the best way to mount an IC fan - push cold air down or extract hot air? both have their pros & cons i guess.
Heatshields and thermo-wrapping the exhaust would help in either case.
a fan will use as much if not more electricity than a pump, but used with an intercooler would mean no water on board so would save on weight. a problem i see with using a carb for feeding water is the surface tension of water, i think it would cause major problems with the water release, it would feed out in droplets as more water collects at the nozzle, as opposed to a constant stream. i can see that causing some pretty major problems. running methanol or another additive would then make it pricey in the long term.
so far i think the options available are....
front mount intercooler - too much pipework, wouldnt work
rear mount intercooler protruding from bodywork or vented - disturbance to airflow, so wouldnt work
rear mount intercooler in engine bay with fan blowing air - possibility. fan will drain power, but intercooler will save weight
chargecooler with rad up front and own pump - pump drains power, adds lots of weight
chargecooler with rad at rear - will disturb airflow, so wouldnt work
chargecooler using engine coolant system - no power drain, wont be as efficient as separate system
water injection with ECU setup - probably the most effective setup. but expensive and adds weight
water injection with carb - potential problems but might be doable. adds weight
i think those are all of the options thus far. its a question of weighing up the pros and cons of each and figuring out which one hinders me the least. they all have major drawbacks, but theres always a compromise somewhere
so far as using water as ballast goes - im space framing most of the car and running double wishbone suspension all round. so what works on stock AW11 is pretty much irrelevant lol. im more concerned with having the absolute minimum of weight without spending a fortune
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