This is an extract from the LSOC forum and written by me, it is a little disjointed as I've edited out the questions it raised and isa little odd to read.
I have for some time tried in vain to find a good reason to fit an FMIC, and just on looks alone I have decided against, so I thought today that I would do a bit of number crunching and what I found has surprised and delighted me.
First, do you know how an IC works?
Bet you think you do!
You are wrong, cos unless you are 'au fait' (whats the French for 'au fait'?) with thermodynamics then you are almost certainly wrong!
It is all to do with mass, if you wanted you could replace the plastic pipes that connect the existing IC to the car with some nice Copper ones, the total mass would actually be 25% greater than the special HKS pipes and FMIC!
It would also be 20% more efficient!!!
Air-to-Air IC's behave very differently to the way they are portrayed by the Tuning Companies.
They are really only heat sinks and dissipation is not a problem on road cars, infact on the TT the existing IC can be made to cope with about 70% more than standard power (480hp) before the through put would fail to cool the greater mass of the metal pipe work!
So I propose to do the following, I am gonna get some copper/alloy pipes of quite large diameter and insert a few straight lengths into the rubber bits of my inlet tract, the convoluted 'S' behind the Air filter will be remain untouched, (I'll try to 'slot in' some bits) and the pipe behind the rad will be replaced with a complete length of copper/alloy, the mass of this is 15% greater than the HKS FMIC with all its pipe work, according to thermodynamics my £30 mods will make my system 12% more efficient than that hugely expensive and ugly mod!
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Ken, you are spot on there the overall heat build up is quite rapid but using 20C as 'perfect' intake temp and calling it '0' and using 60C as being the point where the efficiency of the intake system falls off that 'plateau'. And calling it 0.9166. (That is thermo-dynamic measure) what we are looking for is the time it takes to flood (0.9166) the IC sys. And the time taken to recover to '0'.
That huge FMIC will recover much more quickly than our smaller faced unit, but do you actually want this to happen? Heat and power and handmaidens, power needs heat to give efficiency to function and use.
When we 'back off' the accelerator, do we want the system to cool so rapidly? Well Yes and No.
Yes, 'cos we can then go poking the car into the next straight at ultra high speed, No, 'cos a rapidly cooling trailing throttle will drop revs 'like a stone', making speed build up a longer winded affair when the opportunity next arises! (This is one of the effects that fools the average owner of the newly acquired FMIC into thinking it must be 'working really well' take your foot off the accelerator and the car slows rapidly, therefore it must have been working really well to begin with, this is the first thing road testers used to be trained to stop, this 'reverse function' effect makes fools of even the most wise.)
I have tested to find just how long I can keep my foot to the floor on my nearby road, (remember that even taking the foot off slightly will drop the 'mass heat' quite a bit) the best I could achieve taking 40mph as my norm and calling it 0.2(that’s about 33C IC Sys. temp.) was 22 seconds, that took me to about 160mph and I had to slow down just to stay alive!
So yesterday I calculated that to flood the existing IC to 0.9166 it would take the car 29seconds, I was happy with this figure (I had used the 'worst figures' to achieve it) because of the Rolling road thing of doing each run and ensuring that no more than 30 seconds is taken for the 'process' enshrined somewhere must be the principle of '30 seconds heat sink capability'
The next 'big' question is; How long does it take for the system to recover to 0.2?
Well using Steins therm tables and those adapted by Bendix-Colston Research Inst. it takes...5.4 secs, yep it shocked me too, and the figure for that HKS unit I looked at was 2.1 secs! I used figures based on car averaging 100mph during that braking manoeuvre for 'our car' and 120mph for the HKS unit, both figures are VERY conservative! All figures based on an ambient temp. of 20C
On open roads, the biggest problem for all but the most rarefied road/racers is not size of cooling it is HEATSINK CAPACITY. That is just MASS. For almost every car out there when they fit an FMIC they are buying WEIGHT this is what gives them all their gain!
It is difficult to 'work out' where the point is for changing to a HI-RATE inverter might be, as it depends on the driving style to some extent, but as a guide unless your motor is kicking out 180hp+ per Litre then 'just the bits of copper and a little thought' will do the job perfectly!
One other thing, in town on a hot day, mass is superior to 'flow' every time, so that FMIC may actually work against you in an Urban environment!
These tuning people.....artists....real artists!
Where is this leading?
Well Bill and I agree about one thing on this matter we don't like water spray coolers 'cos they can't do their job correctly, but I now believe they can, but they have to be controlled' by a fairly complex programme, I'll try to describe what would seem to me to be a perfect control system, it is based on the additional 3000grams of copper placed in the inlet tracts.
Imagine a timer, when the car is not boosting more than 0.3 bar the timer is stationary at zero seconds above that on a sliding scale to 1 bar it the seconds tick more quickly so that at 1 bar the clock is ticking at 'real time' above 1 bar it actually ticks the seconds off 'pro rata' when the pressure drops the seconds are counted backward at a ratio of 3 to 1 so the clock runs backward 3 times faster than forward for any given pressure, when the clock reaches 20 seconds then a water atomiser is activated using 40cc per second, this also sets the clock back but again due to the chill effect of evaporation at 6 times quicker than the forward tick at any given speed!
Basically after 20 seconds is accrued the atomiser sprays for 3/4 secs. That will reset the clock!
In addition you can set the unit to spray a 1 sec burst after every 10 secs of full throttle, lowering the build further.
3ltrs(3kilos) would last quite some time and would out perform any FMIC that is currently available.
My design My copyright as of this date, but Harry, you have Electronics Guru stamped all over your posts so you do it, sell it Worldwide send me a freebie and if it makes serious money then we'll talk about it again but go to it if you want! It is only the control circuit that needs making the rest is off the shelf.