Inter-Cooler??????????

[Ian D]

Right I understand what one does (ish) I read the tread on the saab FMIC, and now am very confused! Is this a cheap replacement or a cheap upgrade? how does it fit? whats needed? sorry about the question but a wise old man once told me, it costs nothing to ask!

[geoff_s14]

If you've followed the recent threads,you'll know that the intercooler functions to cool the air charge once it has been compressed by the turbocharger. It is necessary because the act of compressing a gas causes it to gain kinetic energy (heat), which makes it expand, and so become less dense. In an engine you want the incoming air as dense as possible, so it can carry more fuel. The optimum ratio of fuel to air at normal engine temperatures is I think 14:1, by mass, (anybody?), so the more air you can push into the engine, the more fuel you can also get in, therefore a more powerful combustion. An additional concern with hotter air is that of detonation, which is the premature combustion of the charge in the cylinder before the spark is discharged, which can be exacerbated if the temperature of the gases entering the cylinder get too high.

The intercooler itself is just a radiator, through which the intake air is ducted once it has been through the turbo. It is just like the radiator for the coolant, only drier since it flows air rather than water. The 200sx, beit s13 or s14 is cursed with an incy wincy little intercooler set at the front end of the engine bay, tucked in front of the nearside wheel. It does an adequate job of coping with the normal boost temperatures of a standard car, but once the loonies on this board start wanting to jack up their boost pressure (a relatively simple job in itself), air temperature rapidly becomes a crucial factor in deciding whether the engine will run properly or blow itself up. This is when it makes sense to start thinking about ditching the standard IC and replacing it with one of higher capacity. Most of these are designed for specialist racing applications (read expensive), but these cheapskates have tracked down cheaper, higher capacity intercoolers from standard production cars. Enter the SAAB unit. Fitting one of these in an s13 is pretty straightforward, the ideal location is just in front of the radiator, which, with the fan cowling removed, can be mounted a few inches further back towards the engine. In this location it is perfectly placed to receive an ample sufficiency of fresh cold air without (apparently) compromising the function of the radiator. Fitment requires a couple of strips of ally with 3 holes drilled in, to act as brackets for the IC and rad, and a couple of bits of pipe. As for the fitment on the s14, I haven't a clue. In fact, I'm not really in a position to comment at all since I've not fitted an FMIC in either. I'll just get my coat....

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Geoff
Emerald S14a, with God's Own Transmission.

http://www.animfactory.com/animations/transportation/cars/mirror_md_clr.gif

http://www.mpz.co.uk/cwm/ups/kamikaze/smilie_groupflip2.gif

[matt_j]

just an enquiry for the s14 lads....how many of you have coolers and for those that have...which one do you have? i understand the HKS one is like £1000!!!

what options are there fo u guys as it looks like the s13 has a few more, doesn't norris do on for ya??

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Apologies to any cars i have accidentally flame-throwered with my exhaust, can u at least see the funny side? no? oh well hard luck then...

[Papa Lazarou]

I've got a couple of questions on this - hope you don't mind Ian if I ask 'em as part of this thread!!

1: Does a large FMIC require an uprated radiator? I've been advised it might depending on how big it is etc..

2: Would an aftermarket front end be a good idea for fitting an FMIC? I know you can get by with the standard bumper - can it be modded easily to give better airflow properties?

3: Would you recommend fitting mesh over the FMIC or is it generally OK to leave it open t the elements? I wouldn't want my £1K+ intercooler being stone chipped!

Any thoughts on this?

[Billy]

Originally posted by Papa Lazarou:


1: Does a large FMIC require an uprated radiator? I've been advised it might depending on how big it is etc..

2: Would an aftermarket front end be a good idea for fitting an FMIC? I know you can get by with the standard bumper - can it be modded easily to give better airflow properties?

3: Would you recommend fitting mesh over the FMIC or is it generally OK to leave it open t the elements? I wouldn't want my £1K+ intercooler being stone chipped!

1 and 2 are a definite maybe, depends on the IC.

3 is a definite yes. ICs are tougher than water rads as they have to handle higher pressures, and engines don't normally backfire thro' the cooling system. (I'm sure someones heard different!)

If you do mount it in front of the rad, get it as close as possible (to the rad) for best airflow...

[Matt_S]

Ian D, the Saab IC is now regarded (on this board at least)as a cheap upgrade over the OE IC. Although the OE IC has a good position (as opposed to being located on top of the engine ala GTiR/Scooby) it is pretty small and has a strangling effect owing to it being restrictive, giving losses of 3 psi over and HKS FMIC/pipework (when I tested on my S13).
The Saab jobbie is however, like I say, better than the OE one (at least on the S13 anyway). Paul_s13 is now doing something to improve over the Saab IC, by installing a racing spec Saab IC, but still at roughly a third of the price of the HKS jobby which Papa speaks of. The choice is yours, ultimately matey!


Papa,
In answer to your questions:
1) The rad SHOULD be OK, even when stressing it more with extra boost etc and blocking the airflow to it! (Altough Id like to upgrade mine in the future with a high flow core - been quoted about £130 by a local rad place).
2) Aftermarket front ends aren't required for the FMIC fitment, but ultimately would allow more air flow to the cooler. The FMIC's (should) come with all the fitting instructions, telling you what you have to cut out of the metal/skin of the original front end.
3)Deffo want fit mesh over the front. HKS (and as far as I know) Bltz come with nice stencils so you can spray their logo on the cooler. You can still see this with mesh fitted. Me and SteveC have used some stuff from Jewsons (i think) which was about £3.50 for a massive 4ft x 6ft sheet - PLENTY nuff!

Hope this helps

Matt

[Tom_S14]

Goeff, 14.7... is the ratio for obtaining the most energy from the fuel per mass of fuel (ie the most efficient ratio)... I believe about 16:1 is the ratio to go for to generate the most heat (but not the most kinetic energy), and depending on the engine if you don't care how much fuel you burn but want more power than 14.7:1 gives you, anything up to about 10:1 can be used, depending on how the engine cokes up etc.

Air comes in to the system, mass of air is measured.
Air goes to turbo charger (compressor)... heat increases, pressure increases
(volume ? probably doesn't change much).
Air goes into intercooler (big radiator).... heat decreases, pressure stays
the same (volume ? must go down)
Air goes into engine where fuel is added.

Right then, the fuel is added according to the mass of air measured going
into the system.
The question is, the point of the intercooler is to reduce temperature,
increase air density and allow more fuel to be added for a given volume of
air to generate more power.
But, in reducing temperature PV=nRT.... nR is constnat.... in order to keep
pressure constant (this is the boost pressure)... the volume must go down.
But in a closed system, if the volume goes down, the mass stays the same
then the density goes up (which is what we want to happen).

Every stroke the engine takes it draws in a given VOLUME of air+fuel, but
it's the MASS ratio of fuel to air which is important, hence having a higher
density is a good thing. So really.... by having a more efficient
intercooler to reduce temperature and volume, a greater mass of air is drawn
into the engine on each stroke. This mass is measured at the
start (where the air comes into the AFM) and everything works hunky dory, bob's your uncle, fanny's a rude word.

Tom

[geoff_s14]

I bet he's sorry he asked now.... http://300zx.co.uk/200sx/ubb/smile.gif

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Geoff
Emerald S14a, with God's Own Transmission.

http://www.animfactory.com/animations/transportation/cars/mirror_md_clr.gif

[Papa Lazarou]

Thanks very much for the advice Matt, Billy.

I want a new intecooler now..