Outer Limits 4x4 Board

i've got a Toyota Surf with the 2.4L Turbo Diesel engine, which isn't intercooled, and i have picked up a stocko intercooler from a Mitsubishi evo...

what effects should i expect if i install it and is it worth it...

the effects is it will bring your intake temperatures down

should you install it? probably only worth it if you intend on increasing the boost above standard.

what about more lag? it already has hardly any power up until 2000rpm, will this worsen?

Fitt the cooler than add more fuel

Intercoolers only make a (edit: significant) difference if you are running 10psi or more
If the pressure sensor for your wastegate is straight after the turbo (like many), adding an intercooler may decrease performance (because of the extra pressure drop) if you do not adjust the boost (or better still move the sensor to after the intercooler.

If you plan to increase boost/fuelling, it is a very good idea to fit an EGT.

ISUZUROVER wrote:Intercoolers only make a difference if you are running 10psi or more.

No. That may be your opinion, but I think you're simplifying this a little too much.

An intercooler cools the intake charge, making the air denser and effectively increasing the amount of air pumped into the cylinder at any given boost pressure.

A turbocharger can get hot under load, and therefore heat the intake charge, regardless of the pressure the system generates.

A properly installed intercooler WILL make a difference in systems running less than 10psi boost - it's a matter of whether or not the difference it makes is worth the hassle and expense. For low boost systems there are normally other avenues to explore first; like better exhaust, more boost and the right amount of fuel.

Everything else, I agree 100% - as usual.

MITSO wrote:what about more lag? it already has hardly any power up until 2000rpm, will this worsen?

Yes. The intercooler means there's a greater volume of air between turbine and inlet to pressurise when you want more power. This larger volume requires more time to compress, so you'll notice more lag.

An intercooler will probably only make it's best improvement under conditions of sustained high load, when the turbo will get hottest. That's why you should improve other areas first, because, for a typical recreational 4wder, better throttle response will be more use than more power at high revs.

My 2c.

Scott

edited to remove drivel... see last post

ISUZUROVER wrote:No, not my opinion, it is what the automotive engineering textbooks say. It is not worth intercooling an engine running under 10psi, as any increased air density gained through cooling is offset by the increased pressure drop through the intercooler. For an extremely efficient intercooler with very low flow resistance this may not be the case, but it is for most intercoolers.

Which will only apply if your pressure sensor is upstream of the intercooler rather than downstream - where it belongs.

NJ SWB wrote:A properly installed intercooler

Scott

edited to remove drivel... see last post

ISUZUROVER wrote:Not really - gains through increased charge density are offset by "pumping losses". It is a well known rule of thumb in engineering.

OK.

Turbocharged engine running (say) 8psi boost with boost sensor at the inlet manifold.

Install intercooler.

The 8psi intake charge is now cooler and therefore more dense.

This doesn't "make a difference?"

Please explain.

Scott

edited to remove drivel... see last post

Perhaps you should forward the info to Ford too. The XR6 turbo is running an intercooler with only 6 psi.

Idiots!

Scott

ISUZUROVER wrote:

NJ SWB wrote:

ISUZUROVER wrote:Intercoolers only make a difference if you are running 10psi or more.

No. That may be your opinion, but I think you're simplifying this a little too much.

No, not my opinion, it is what the automotive engineering textbooks say. It is not worth intercooling an engine running under 10psi, as any increased air density gained through cooling is offset by the increased pressure drop through the intercooler. For an extremely efficient intercooler with very low flow resistance this may not be the case, but it is for most intercoolers.

I understand where your comming from but your that is not true.The 10psi rule that you mention is a joke,it all depend's on size of pipeing/size of cooler/how long the cooler pipes are etc.

I can take any vehicle petrol/diesel running stock boost(let's say 6 psi)install a small cooler 2inch cooler pipes and i garantee the vehicle will make more power and use less fuel.Yes the vehile might lag a little more but it is worth it and of corse the cooler size should/must be in accordance to the turbo size/boost.


Throw that textbook away.

edited to remove drivel... see last post

what psi does the intercooled 1HDFET toyoto motor run?

dont think it would be more than 8psi

it is what the automotive engineering textbooks say

it is a well known rule of thumb in engineering.

it has been a while since I have looked at the theory behind the 10psi rule of thumb. When I have a moment I will look it up to provide a better answer...

ben, you know a lot about nothing. or was that nothing about a lot! the dude has a cooler already. let him install it and find out how it works in the real world. i've actually built an exhaust system for a turbo diesel. and i will actually be putting an intercooler on it. i've learnt a lot from this thread and it wasn't from any of your posts.

gtfoh

Ben,
Look up in your "engineering textbook" if cooler air is more dense and has more oxygen to burn than hot air. As you might also find, is compressing air raises its temperature, and depending on the adiabatic efficiency of the compressor (the turbo in this case) the air can rise to different temperatures. It is generally true that compressed air above 10psi is hotter than air below 10psi, but the benefits of an intercooler do work regardless of the psi, and it is not just psi that gives the engine power, as higher compression (or psi) creates a higher initial charge temp and even thinner, less dense air, hence the need for a bigger intercooler to bring the temp back down close to ambient. Like hienuf said, the core size and tube length should be worked out for the turbo efficiency and engine size.

Edit - god I posted some crap the other day - don't know what came over me.

Damian - I agree with everything you say. It seems the "rule of thumb" I quoted was a bit off - However - the relative benefit of an intercooler is proportional to the boost that the engine is running. And thanks for reminding me of some of the thermodynamics so I could check what the real relationship was (see below).

Here is a useful intercooler design spreadsheet I posted a link to a few days ago.
http://www.outerlimits4x4.com/PHP_Modul ... hp?t=67402

Now - I have finally gone back over the thermodynamics I had forgotten so I can explain what I was talking about in the first place.

The adiabatic heating of air during compression is approximately:
T2=T1*(P2/P1)^0.283

where T1 is the compressor inlet temp, T2 the compressor outlet temp, and P1 and P2 the inlet and outlet temps respectively.

The final Temp of the air leaving the compressor is:
T3=T1+(T2-T1)/CE

where CE is compressor efficiency. The coolling provided by the intercooler is basically the same equation.

If the wastegate is controlled by a pressure sensor on the inlet manifold, the peak boost pressure reaching the engine can be assumed to be constant, only the temperature changes. But the intercooler induces an extra pressure drop on the system, which means the turbo has to work harder to maintain the same boost pressure at the manifold.

If you run through the calc above for the same system with and without a charge cooler (intercooler), you can work out the temperature difference in the air reaching the engine (with and without an intercooler), which is proportional to the mass difference in the air, which is proportional to the increase in engine performance. Anyone see any problems with that so far???

So, to see how much difference an intercooler makes, I picked some typical values for the calcs:
T1 = 373.15K (30°C)
P1 = 1 atm
delta P for the intercooler is 20% of the boost pressure (not really realistic for 15psi and above)
Compressor Efficiency = 70% (typical range 55-95%)
Intercooler Efficiency = 65% (typical range 50-90%)

If you look at the graph below, you can see that for a reasonable efficient intercooler setup you get about a 5% inlet temperature decrease over the same setup without an intercooler at 10psi. Naturally if you had a more effective intercooler (e.g. water to air) with a lower pressure drop you could get more of an increase. But I think the numbers are reasonably representative of what happens in reality. If you work out the power and torque increase for an intercooler with equivalent pressure drop in the intercooler design spreadsheet above, you get about a 5% increase in power and torque (for a 4L diesel at 2500rpm).

The bottom line is - if your setup is running reasonably low boost, bolting come random (probably inappropriately sized) intercooler on is unlikely to make a noticeable difference. But if you already have a free intercooler, why not suck-it-and-see.

Thanks Ben. I was under the impression the more significant temperature increase in the incoming charge was due to the heat of the turbine housing. e.g. exhaust gas heat causes exhaust turbine housing to heat, conduction causes inlet turbine housing to heat, hot inlet turbine housing causes intake air to heat.

This is not significant?

Scott

That is a definitely a factor, but usually a lot less significant than adiabatic heating. For the sake of the simplified comparison above, I assumed they were both the same for the intercooler and non-intercooler case, which is not too unreasonable.

To further add to the discussion - if you chose a really inappropriate intercooler, let's say one that has only 50% efficiency and also has a high pressure drop (4psi in this case) - then you can actually have hotter air reaching your engine at low boost levels than if you didn't have an intercooler (see graph - temps in Kelvin subtract 273 for degrees - but are only representative values). The relationship would be the same regardless of temperature. If you had an even more restrictive intercooler it would make the situation even worse.

So plumbing in some random (inappropriate) intercooler COULD DECREASE PERFORMANCE.

One last graph...

This one shows the possible ranges that you are likely to see in most setups with and without an intercooler. The red region means that the engine performance would be worse with an intercooler.

NJ SWB wrote:Perhaps you should forward the info to Ford too. The XR6 turbo is running an intercooler with only 6 psi.

Idiots!

Scott

Yes they are only 6 PSI, but remember this is a petrol engine not a Diesel.
1/2 the compression ratio.

kempster1 wrote:

NJ SWB wrote:Perhaps you should forward the info to Ford too. The XR6 turbo is running an intercooler with only 6 psi.

Idiots!

Scott

Yes they are only 6 PSI, but remember this is a petrol engine not a Diesel.
1/2 the compression ratio.

Less than half, probably. But I fail to see how this fact is relevant to the discussion here.

Would you care to explain?

Scott

Petrols just do not need as much air.

Intercoolers with give added preformance no matter what the boost pressure is, as it has been stated cooler air = more oxygen content = more power

kempster1 wrote:Petrols just do not need as much air.

Intercoolers with give added preformance no matter what the boost pressure is, as it has been stated cooler air = more oxygen content = more power

Did u read any of the above

kempster1 wrote:Petrols just do not need as much air.

So, let me see if I understand you here. You're saying that a three litre petrol engine running 10psi boost doesn't need as much air as a three litre diesel engine running 10psi boost?

I'm afraid I'll need you to explain this to me.

kempster1 wrote:Intercoolers with give added preformance no matter what the boost pressure is, as it has been stated cooler air = more oxygen content = more power

jeep97tj wrote:Did u read any of the above

He may have read it, but I don't think he understood it.

kempster,

Ben has explained how an incorrectly sized intercooler can INCREASE the temperature of the intake air. Wrong intercooler = HOTTER air = less oxygen in the cylinder = less power.

If you can find an error in what he's posted please feel free to set us straight.

Scott

quick60 wrote:Ben,
Look up in your "engineering textbook" if cooler air is more dense and has more oxygen to burn than hot air. As you might also find, is compressing air raises its temperature, and depending on the adiabatic efficiency of the compressor (the turbo in this case) the air can rise to different temperatures. It is generally true that compressed air above 10psi is hotter than air below 10psi, but the benefits of an intercooler do work regardless of the psi, and it is not just psi that gives the engine power, as higher compression (or psi) creates a higher initial charge temp and even thinner, less dense air, hence the need for a bigger intercooler to bring the temp back down close to ambient. Like hienuf said, the core size and tube length should be worked out for the turbo efficiency and engine size.

I should have quoted this staement from Quick60, it is just about spot on.

Most of the heat raise in the intake air is heat is from the air being compressed by the turbo.

god I posted some crap the other day - don't know what came over me.

too much time in Deutschland (and Italy wityh Michele) swigging too many excellent brews, I'd say....

hmmm
All this has made me throw up, thinking back to my thermodynamics studies etc...
Actually it has made me more determined to find the time to measure my upstream and downstream-of-the-intercooler temps.

I hope I was right with my plumbing and diameters, cos I'm not going to change it unless it really have to!!!

JC

hmmm
All this has made me throw up, thinking back to my thermodynamics studies etc...
Actually it has made me more determined to find the time to measure my upstream and downstream-of-the-intercooler temps.

I hope I was right with my plumbing and diameters, cos I'm not going to change it unless it really have to!!!
BTW, I'm running 10psi at the manifold.

JC