darkblueturbo

more brain picking...

Stop me if I go wrong anywhere:

the intercooler make the air cold before the turbo compresses it and stuffs it into the cylinders to burn the petrol.
The bonnet scoop is where all this fresh air comes from, before going through the panel filter and down into the intercooler.

What advantage does a front-mounted intercooler give you? Looking at the prices of them they're not cheep. Do they really make THAT much difference?
Are they in addition to the existing unit, or do you end up with a big space in your engine bay (like mum's Swift) and a pointless air-scoop on the front of your car?

Thanks for the info guys.

LG John

Close but no cigar As far as I know the air is sucked in through the plastic duct at the front of the car where it goes through the panel filter and then into the turbo. I say, sucked because the turbo will be drawing it through at more than atmospheric pressure. It then goes through the turbo where the compression process heats the air up (not good) This then goes through the intercooler pipework which had air from the outside moving through its fins which cools it down. The nicely cooled and compressed air then goes into the cylinders, etc and the exhaust goes back into the turbo (at the other side) to power it. I'm pretty sure the above is correct

A front mount is better because it has a greater area exposed to the flow of outside air and doens't require a scoop to change the direction of the air. I'm thinking of an intercooler spliter which is a metal contraption you fit on your top-mount to redirect the air through it better.

Phew, hope that helps

darkblueturbo

thanks for the reply saxo boy. Still got a couple of questions though so I've got it clear in my head.

plastic duct at the front of the car. what's this? Are these the little orange bits under my front inidicators?

so the air scoop is only to help cool the intercooler, and is not actually an air intake for the engine. Which is why the FMIC is better as more surface area is exposed to the air.

Does the front mounted one make that much difference in power/torque? i.e. How much cooler is the air before it goes into the engine? Is it worth the cost, extra piping and installation time?

uxg

Saxo Boy. Any more info on this spliiter thing. I am also concerned about the Top mount thing but don't really want to spend £££'s on a FMIC unless I absolutely need to. I also hate the idea of having to chop up my front bumper as the FMIC's make the car look odd IMO. I have a 98 Type R with about 300bhp. I was thinknig about getting a larger Top mount from a later version STi or maybe form another manufacturer but will this splitter be any good.

Any info would be much appreciated.

LG John

Lift the bonnet and you should see a black plastic pipe leading from the front (near the headlight) of the engine into the airbox via the driverside wheel arch!!! This is the air that goes into the turbo, through the intercooler and then into the cyclinders complete with spark and appropriate amount of fuel (hopefully!!). The air that goes through the scoop and then through the intercooler never makes its way into the cylinders it's simply to cool the pressurised air in the intercoolers pipework.

Not sure if front mounts are worth it, I can't afford one so haven't really looked into it - I'd guess they probably are if your going for bit power. My MY99 has about 275bhp but I'd never want to go much above 300 so I'd probably make do with an upgraded top mount and a bigger/better turbo.

If you do a search under 'intercooler splitter' you should find Devils Refugee's thread from a week or so ago about it...had a link to a website.

Pavlo

Inlet temperature is critial for high performance.

So an FMIC can give improvements in torque and power even on a basic spec car, but the best gains come when you are looking at higher boost and generally better breathing.

To compress the air, which is being supplied at some flow rate, means you must do work on the air, so you will be increasing it's temperature even if you supercharged it (no hot exhaust involved). Obviously the higher power you seek, you need more airflow, and generally this means more boost, so you will add to the heating on both counts.

Now, in terms of actual power/flow loss due to temperature, you can use the ideal gas law. Basically the pressure is proportional to the temperature in Kelvin (ie absolute). Or it means for the same volume (flow) that mass of air is inversly proportional to the temperature.

To put some numbers on this, if you were running 1.2bar on a top mount, you might expect to touch 55'C (328K) inlet temps. If you fitted a good FMIC, you might get this down to 35'C (308K), a drop of 20'C.

328/308= 1.065 so an increase in mass airflow of 6.5% could be had for the same boost pressure, which is 6.5% more power in simple terms, or 21.5hp if you were at 330hp.

Or 308/328 =0.94 so a decrease in manifold pressure of 6.6% for the same mass flow, which means you could get the same power at 1.13 bar, plus a bit more from additional ignition advance.

However, when you start to push closer to 1.5 bar, the temperature problem becomes prohibitive in terms of ignition advance, fuel octane requirements and ultimately power.

Engine with an FMIC that doesn't blow up is also going to make more power than one with more boost on a TMIC an a hole in the piston....

Paul

darkblueturbo

Pavlo - thanks for such an in depth response. Fantastic!

The figures you're talking about are one's I probably won't reach. I want to get the power figures up near 300, but have no plans to go over that, so a front-mounted wouldn't be as vital for me as I'm not thinking of bigger turbo's or very high boost.

Thanks again. I love the people on scoobynet. Everyone's so damn helpful (and knowledgable with it!)

Pavlo

An FMIC does give an extra element of safety, but plenty of people are getting around 300 on the TMIC.

A compromise might be to get an STI TMIC s/h, there's one for in the for sale forum for £150.

Paul

Devil's Refugee

I'll join in here by saying that I'm about to fit next week an uprated TMIC from APS, which is larger than the STI (and a bit more expensive, but less so than a FMIC) so I'll try to post results asap. This is getting fitted alongside a larger VF28 turbo.

In the words of Dr Banks, having a FMIC is "like a cold day, every day"

darkblueturbo

Devil's Refugee (erm, nice handle!),

"like a cold day everyday" that makes PERFECT sense to me now. Those cold mornings where she's that little bit snappier and wanting it that little bit more. Oh yes!

Will keep an eye out for results on your new TMIC.

Saxo Boy, please post when you've got your splitter too!


I that dim and distant future when I have more mods than just a new back box and I'm 280-300 (my sensible target) I'll probably go for a splitter (if it works well for Saxo boy) or the Sti item rather than a frontmounted simply for ease of fitting and cost!

Thanks everyone. Be quick and be safe.

uxg

I also second that. I ain't really planning on going above 300bhp so I can't really justify the price of a FMIC. What are they, about £1000??

I already have the STI intercooler so would be interested in the splitter or an uprated TMIC if there are any which are better than the STI jobbie. Anyone have any ideas roughly how much a TMIC would cost?

I have also heard that you can angle the intercooler to better direct airflow to it. Can this be done on a 98 STI.

Sorry for all the questions but I'd like to improve the cooling efficiency without spending to much if possible, not so much for power gains more to improve reliability

nom

A note on the APS TMIC which I've had for a couple of months now - I found there was quite a difference between the standard (MY00) TMIC & this one. From figures (except not very usefully I don't measure inlet temp ) I'd say the difference it makes is that it is more free-flowing, but heat-exchange efficiency is similar. So, the turbo doesn't have to run as hard to produce the required boost, so it (the turbo) is running more efficiently, so its outlet temps are lower, rather than the TMIC cooling it more. Anyways, a great (not so)little box .

madou

uxg

I have a STi V5 TMIC on my MY98 UK. Assume dimensions in this area are the same as MY98 STi

Bolts straight on to existing mounting points, but you need to fit a take off pipe to the front right of the STi V5 TMIC. Ian at Hayward and Scott has made several of these ( ask him to keep the length of the straight section to 1 inch, this will make a gentler bend for the piping down to the dump valve )

Did help during mapping, to the degree it can with UK internals, injectors and hair dryer turbo

[Edited by madou - 10/10/2002 6:10:39 PM]