Fitting a second intercooler

I brought brought a second intercooler a few months back for my 156 2.4, never got round to fitting it and got a 147 1.9 now, so I m going to fit it to that (1.9 and 2.4 use the same intercooler). Thing is I m not sure whether to mount it in series or in line-ie should I split the pipe and send the air to both intercoolers and then use another splitter to join the pipe again just before it goes into the manifold or whether I should just add the second into the intake "circuit". The first way seems best as I think the second might make it feel less responsive as there would just be extra pipe work and further so for the air to travel. Any one agree?

Won't it really be more dependant on where you can fit the second intercooler?! Where are you planning on fitting the second one?

Cheers,

Mark

Originally Posted by typos1

The first way seems best as I think the second might make it feel less responsive as there would just be extra pipe work and further so for the air to travel. Any one agree?

I don’t think that the serial or parallel installation of intercoolers makes much difference, the question is the location of the intercooler and if at least one of them has a direct airflow through the bumper. My guess is you will have a little more turbo lag and less responsive reaction because you double the air volume between the turbo and intake manifold. So when you press the pedal, turbo has to build up pressure in much bigger chambers and the reaction will be slightly slower. My 2 cents...

Originally Posted by gotcha

I don’t think that the serial or parallel installation of intercoolers makes much difference, the question is the location of the intercooler and if at least one of them has a direct airflow through the bumper. My guess is you will have a little more turbo lag and less responsive reaction because you double the air volume between the turbo and intake manifold. So when you press the pedal, turbo has to build up pressure in much bigger chambers and the reaction will be slightly slower. My 2 cents...

Yeah, thats what I was getting at, so surely splitting the hoses before and after the intercooler will cause less lag as oppossed to just putting them one after the other which would cause more. I keep thinking of 2 straws-if you join them together end to end and suck liquid through them you ll get a slower response than if you put them side by side, but overall the same amount of liquid will be drawn through. That was the theory anyway

Depends what you are trying to achieve with the 2 intercooler solution; reduced pressure loss (parallel) or increased heat transfer (series). Do you know what intake temperature you are getting at the moment? Might help you decide which way to go. Also need to think about if you will upset cooling flow through the radiator.

I m going to try and mount it near the current intercooler, not in front of the radiator, so not expecting cooling probs. I want the benefits of a larger intercooler (increased power/torque/efficiency)without the expense or hassle of fitting one (think it ll be a lot easier to fit another alongside the existing one). You reckon the air will loose more heat in series than parallel, then?-Whys that? I would nt have thought it would make a difference to the heat transfer

Heat transfer rate is affected by path length, and surface speed / turbulence. If you have 2 coolers in series, the air speed is twice as fast as in parallel so you get a higher heat transfer rate; and you have twice the path length so even more cooling. But, you get twice the pressure drop....

Right, but parellel will still masively increase cooling compared to having just one intercooler, surely?

Originally Posted by typos1

Right, but parellel will still masively increase cooling compared to having just one intercooler, surely?

I'm tempted to take the fifth ammendment; without knowing anything about the cooler spec to start with I don't know, I expect it will make a difference, but not neccesarily massively.

Do you know what temperature you are getting at the moment? If the cooler is sized for the 2.4, then I think it will be more than big enough for a 1.9 unless you are running extra boost.

They both use the same intercooler, it is is an air to air radiator (as I m sure you know!). Either way it'll decrease the temp of the intake air but, from what you say, mounting them in series would maximise the cooling effect and in parallel would give faster response. But we're still talking increasing intercooler size by 100% if I do it in parallel.

It might be worth looking at another car that has a twin intercooler to see how they are set up. I have a feeling that's the difference between the Audi S3's or Seat Leon Cupra R's, they went from a single to a twin intercooler and that's where they jumped from 210 - 225bhp I believe. I'm not sure about diesels, but on a petrol turbo, a rough rule of thumb is that if you can lower the intake temps but 10 degrees, you will get roughly a 4% increase in power.

Originally Posted by typos1

They both use the same intercooler, it is is an air to air radiator (as I m sure you know!). Either way it'll decrease the temp of the intake air but, from what you say, mounting them in series would maximise the cooling effect and in parallel would give faster response. But we're still talking increasing intercooler size by 100% if I do it in parallel.

Just to try to put the physics into context; which cools your hand more; putting it under a tap for 10 seconds, or sticking it into a bucket of water for 10 seconds? The bucket contains much more water, but is less effective. If you make the intercooler too big, that's the effect you get. I suspect you'll need to remap it if you modify the intercooler using eitehr approach if you want to gte maximum benefit; I'd strongly advise finding out what your max delivery temperatures are now on a dyno (or ask someone who has tuned one) to see whether it is already big enough....

If you do go down the route of fitting the second i/c, make absolutely sure that you have got the ducting sorted out to actually get cold air through it.

Originally Posted by Mark_JTD

It might be worth looking at another car that has a twin intercooler to see how they are set up. I have a feeling that's the difference between the Audi S3's or Seat Leon Cupra R's, they went from a single to a twin intercooler and that's where they jumped from 210 - 225bhp I believe. I'm not sure about diesels, but on a petrol turbo, a rough rule of thumb is that if you can lower the intake temps but 10 degrees, you will get roughly a 4% increase in power.

Should be the same % for diesel as it's all about air density change with temperature.

Fiting a twin intercooler system in your car would be pointless, your theory is seriously flawed and droping the temperarure of the charge air too low will only cause other problems (spark blow out, misfires, etc), mainly though it will damage the turbo, the increased volume of air at lower pressure will allow the turbo to overspeed easier, if you want to go ahead with it though, you need to think about a lot more things and have far deeper pockets than you expected.

Not sure how the wastegate works on these engines; but I would expect that the reduced pressure loss of a parallel set-up would be 1-2psi max, so it's not a million miles from where the compressor map is designed to operate? I suspect the main consequence would be that there wouldn't be noticeable extra power, and it would feel laggier

Spark blowout?-We re talking diesel here not petrol. All I ll be doing is increasing the density of air and therefore the amount of oxygen in it, which will, surely mean more complete combustion, less smoke, improved efficiency etc. There are a variey of companies that specialise in fitting larger intercoolers to turbo diesels to increase efficiency for towing etc. Its not my theory, its a well known theory that has lead to the fitment of an intercooler in the first place.

Hope you don't get the idea I'm not enthusiastic about your ideas; I've spent lots of time playing with turbo and intercooler setups trying to get the right compromises; but it's easy to change one thing and have a detrimental effect elsewhere. Having gone down the road of a big intercooler and ended up with low intake charge temperature but lots of lag and high water temperatures, I've currently reverted to a standard setup and much better ducting / heat shielding. I've realised that to get the performance I want, I need to junk the air con radiator because its in the way of the main radiator, and there's just not enough airflow under the bonnet to feed engine, radiator, intercooler, and air con rad. Something's go to go....

You can have dual intercoolers but its completely pointless unless you're running BIG power and/or BIG boost.

It won't really make the turbo more "Laggy" like people have suggested. Turbos shift massive quatities of air a second, so increasing the path by a realistic amount doesn't really affect this noticably.

On a side note, lag isn't actually what most people think it is, i.e. waiting for the turbo to "come on", this phase is spool. Lag is the time between being on boost and being on full boost, usually not a problem on a road car.

You're cooling will of course be improved but you will lose boost pressure between it leaving the turbo and it entering the engine due to the extra obstacles it has to pass through. The second IC won't have to be in direct airflow as the charge will be cooled sufficiently by the first cooler. As long as SOME air gets to it it will be fine.

I don't know how large your IC's are, but commonly, dual ICs are wide but not very tall IC's stacked on top of each other, with boost pipes splitting and entering both.

To sum up i think the idea is totally pointless on your road car as it won't increase performance noticably, may reduce drivability and will be a waste of time/money. The best idea for you is to buy a single uprated intercooler and use that, it will be more than able to cope with what you have.

Ic's fitted in series:



Note the car above runs 900 to over 1000bhp so twin Ic's are feasible. Anything less doesn't need this cooling. Stick to one, thick cored front mount. I cannot find a picture online of the stacked type of dual IC's but look at the above picture, imagine an intercooler identical to the horizontally mounted one attached above it with a boost pipe entering each, then on the exit a single combined pipe.

Originally Posted by Smaky

Fiting a twin intercooler system in your car would be pointless, your theory is seriously flawed and droping the temperarure of the charge air too low will only cause other problems (spark blow out, misfires, etc), mainly though it will damage the turbo, the increased volume of air at lower pressure will allow the turbo to overspeed easier, if you want to go ahead with it though, you need to think about a lot more things and have far deeper pockets than you expected.

Just to clear this up a bit:

Yes it would be pointless.

Dropping the temp of a compressed charge by using IC's will still give an inlet temp of warmer or equal to ambient air, you're not going to start freezing things hahaha! Do you realise how hot turbines get? Have you seen one at full chat, the metal glows, so theres no worry of going too cold there.

I can't see how this would damage the turbo in any way whatsoever... it can only spin as fast as the exhaust gases permit, having a longer inlet tract has nothing to do with how fast a turbine spins, as i mentioned they flow massive amounts of air a second. All that will happen will be a cooler charge being delivered into the engine at a lower pressure (Pointless) at the same turbo speed.

Yes he would need deep pockets.

Originally Posted by Sam O'Keefe

I can't see how this would damage the turbo in any way whatsoever... it can only spin as fast as the exhaust gases permit, having a longer inlet tract has nothing to do with how fast a turbine spins, as i mentioned they flow massive amounts of air a second. All that will happen will be a cooler charge being delivered into the engine at a lower pressure (Pointless) at the same turbo speed.

?? The wastegate system is what controls the turbine max speed, but indirectly through limiting compressor delivery pressure. If you change the relationship between speed and compressor delivery pressure, then you can potentially increase the compressor speed. For example, if you are trying to run high boost and lose one of the hoses, you can quickly overspeed the turbo because the delivery pressure drops through the floor...

The standard intercooler is not bad in its size or cooling capabilities, but like the VW golfs etc, its been put in the most inefficiant of places, in the wing!
Extra cooling after the turbo will lead to more dense air and more power.
The 8/10v JTD's air temp sensor was integrated in the air mass meter, the 16/20v was integrated into the map sensor. - Hope that clears that one up.
Rather than fit another in line IC, you would be better off ditching the IC in the wing and fitting a FMIC, such an an IC from a saab 900 turbo NG 94-98, this will fit in the bumper of a 156 with just a few mods, front mount so loads of cold air.
Now moving to FMIC is only half of it, the real benifit is you now have loads of room to take a straight pipe (intake) from the turbo and fit a decent filter in the inside wing away from the heat of the engine with its own cold air supply through the front bumper.
If your going for a remap, then go for a larger (an 80mm for 2.4) intake with larger air mass body for your standard air mass sensor to sit in.
if you have an 8or10v, then change the map sensor for a 3 or 3.5 bar sensor, the 16/20v are 3 bar anyway, so you could go 3.5 to run extra boost.
the 3.5bar sensor will need chipping in as it works from 1v base, rather than 2v base, the larger air mass will need a little chipping to spool up quicker, but it will get the throttle back to something thats linear and progressive if your chipping the thing.
The best intercooler will only get close to atmospheric cooling, to go beyond that you will need water injection, this will allow you to run serious boost levels. If you go for this you may as well run a 50/50% mix water & methonal for its octane, it will help keep the smoking down at high rpm.
Just remember, you need the boost higher up the rev band, let it all out low down and the gearbox and clutch will not last long at all.
If you have the 140 2.4 with the Gt2256, you will be good for 1.9bar boost at 4800rpm.
the turbos on the 1.9's are much smaller, but it is a very tunable engine and a few harware mods should see 200bhp, with drastic mods seeing 250bhp

I have the 1.9 16 valve. I fully intend to heat shield the intercoolers as I dont like the idea of obscuring the radiator. I m going to fit a 2.4 airbox with a K&N filter, and heat shield/insulate the airbox, I m also going to change the indicators from their current position so I can make the whole in the bumper bigger so more air flows through it. I m simply fitting another intercooler as a cheaper and easier alternative to fitting a larger one. Its currently got an adjustable tuning box fitted (I ll remap when I can afford it) and I m hoping to be able to turn the box "up" without getting smoke as I do now, after fitting new IC (although it only seems to be under load when cold that I get smoke, but turned box down a bit currently). Some manufactureres mount the IC on the top of the engine (Subaru, Peugeot), which I reckon is daft (hot air rises etc), but I dont understand whats wrong with in front of the wing-its at the front of the car for maximum cold airflow but it DOESNT interfere with the radiator.