Larger Intercooler = Higher EGT's ???

[cieranc]

I've finally got round to installing my new intercooler today. It's a full width twin-pass type, and a good bit thicker. My plan was to fit the intercooler to reduce EGT's, so a bit of mild tuning can be undertaken. My plan was to up the boost from standard (Def spec 200TDi) to 1.0 bar at the inlet manifold, and a slight increase in fuelling.

However, with this intercooler fitted, the EGT's have increased slightly. There is a noticeable difference in driveability, better acceleration and less smoke (wasn't much to begin with), but it's the EGT's that have got me puzzled. At tickover it used to be around the 100 - 110 deg C mark, now nearer 130?

Hard acceleration in 4th up a long local incline used to earn about 520 deg, now nearer 550-570.

I don't get it, nothing else has been altered.

I havn't checked the boost yet, as my gague is temporarily installed in an Iveco for diagnostic purposes. But the gain in acceleration suggests there's no loss of pressure.

Am I missing something obvious?

[Philip Tonkin]

EGT are related to the combustion of the fuel not the temperature of the inlet air. Intercoolers allow cooler, denser air to the engine giving more oxygen by volume so the engine can burn more fuel and give more power. This will lead to higher EGT.

[mateyboy]

nice looking thing.

[Steve H]

It is my understanding that the best way to minimise high EGTs is to fit a larger bore exhaust, to get those temps away from the head as quick as possible. Not sure what you've got but 2 1/2" seems to be a popular size for moderate state of tune.

Steve

[cieranc]

Thanks Mateyboy, the pic above is with the intercooler just sitting in place and not installed properly.

Running a standard exhaust at the moment.

Seems my understanding of how this works is all wrong. I was expecting to see a reduction in EGT's with just the intercooler, and the EGT's raising back to original or slightly higher with a pump tweak and mild boost increase.

So short of fitting a bigger bore exhaust, which I wasn't planning on doing, is there anything else I can do to reduce EGT's prior to tuning?

The most I've seen with the standard cooler is 680 deg, towing our 3.2 ton airbag trailer up a long hill.

My original plan was to fit a full width intercooler for half the price of the AliSport kit, keeping the 110 as original as possible. By modifying the intercooler to suit the standard 110 pipework and hoses, everything can be reverted to standard quickly and easily. The only modifications to the stock 110 are 2 holes in the slam panel for the rubber bobbins, horn relocated and bonnet catch modified. Full thread to follow WHEN I'm happy with it (happy with the installation, and it's in budget, but not happy with the end results as yet).

[nicks90]

you said in your original post that you were getting a bit of smoke before you fitted this intercooler - black smoke is unburnt diesel! So now you have a bigger better more efficient intercooler, you are getting more dense cold oxygen in the cylinders and that unburnt diesel is now being burnt.

more burny burny = more hotty hotty!

This will explain the slightly better performance you are getting as well, because if your engine 'under fuels' and you get no smoke at all and complete combustion - fitting a bigger intercooler wont actually give you any extra performance.

550-570C isnt that bad. 700C seems to be the nominal threshold for safety from what i have read. So seems you still have a nice safety margin.

[cieranc]

550 - 570 isn't too bad no, but that's unladen without any alteration to boost or fuelling. I dread to think what it will make with the trailer on and more fuel and boost!

So it's possible that this engine was running rich to begin with?

By smoke, I just mean the puff of smoke on start-up, it smokes very little whilst running.

One thing that did cross my mind: Would the intercooler being placed in front of, rather beside the radiator make a difference?

I mean, is it possible for the heat of the radiator to radiate forwards whilst driving, actually heating the intercooler?

I would expect the airflow to carry any radiated heat rearwards into the engine room.

I don't know the history of this engine by the way, I bought it to replace my 2.5 petrol, and just assumed it was stock.

So what effect should I expect from upping the boost to 1.0 bar, higher EGT's again?

If it comes to it I can make a new exhaust, but it really wasn't on the cards.

But would it help if I removed the middle exhaust box?

[David Sparkes]

I mean, is it possible for the heat of the radiator to radiate forwards whilst driving, actually heating the intercooler?

Yes, very much so. Obviously it is affected by how close the two are together, but if you ever monitor the air temperature at the intercooler outlet, or in the inlet manifold, you will see a significant rise after you have changed from high to low speed travel (the two are relative). I have easily seen 40C in the inlet manifold, when the ambient air temp has been ~20C. Remember the radiator will be at 80C or more, once the engine is warm.

If this becomes a concern, consider having small electric fans blowing all the time once the engine has warmed sufficiently to open the thermostat. This won't cool down a hot intercooler, but it minimises the heat soak of the intercooler from the radiant heat of the radiator. Arrange these fans to blow or suck directly onto the intercooler. I use two side by side fans coupled in series, which minimises the current drain while covering the full width of the intercooler. You really need these fans at low vehicle speeds, or while queing in traffic. Engine and alternator speeds are low under these circumstances, so you do need to keep an eye on the current draw.

HTH

[cieranc]

This does help, thanks. Though my 110 is rarely used for hard going low speed work, it's generally just towing.

There's a gap of at least an inch between cooler and radiator.

So I'm in a bit of a dilemma now, I had considered (but didn't want to fit) cooling fans for the intercooler.

I currently have one large electric fan (Mondeo) on the radiator only.

Do I:

1, Go ahead with the tune and hope for the best, just see what happens,

2, Go ahead with the tune, remove the electric fan and re-fit the dynafan (I like the space the electric fan gives),

3, Go ahead with the tune and refit standard intercooler,

4, Do not tune and just enjoy the extra power of the intercooler alone?

[David Sparkes]

Don't do low speed work? You mean you never get stuck in traffic, never drive in congested conditions?

You tow but only at high speed? I didn't know the opportunities for that sort of driving still existed in the UK :-)

From your description I'd say your engine normally works fairly hard. While moving the heat goes backwards, but drop to 30 ish and it will radiate in all directions. I'd estimate that 3 to 5 minutes of 30 mph after a good tow and the intercooler will have jumped 10C at least.

Start with 4, when you get bored in 12 months or so go to 1.

Hold a decision about the fans until you find out whether or not the engine goes 'soft' when it gets warm. If it does you need them, if it doesn't you can manage without - unless you fit a dual gauge to monitor air temperature and turbo pressure, say, because then you won't have to guess, or rely on someone elses's opinion, you will know what happens when (and whether I'm right or wrong)!!

[66gaza]

Put your boost gauge back in and a before and after comparison might be interesting. Are you sure you are not just enjoying the extra power? If you are getting better acceleration and less smoke the bigger intercooler must be doing its job. Put a new air filter in and a new fuel filter as a slightly blocked fuel filter reduces fuel pressure and by default retards timing slightly which increases EGTs. Your tickover EGTs are low anyway.

Gaza

[GL88]

EGT are related to the combustion of the fuel not the temperature of the inlet air. Intercoolers allow cooler, denser air to the engine giving more oxygen by volume so the engine can burn more fuel and give more power. This will lead to higher EGT.

I agree with this.

The reason for having an intercooler is because compressing a gas raises its temperature and a turbo is a blooming hot compressor. The intercooler cools the air back down to a degree which means more oxygen for any given volume.

Your larger intercooler is the only change made and because it is more efficient it will result in cooler (denser) air entering the combustion chambers and a leaner burn as a result (more oxygen/same amount of fuel). Further raising the boost pressure with no other changes will result in an even leaner and hotter EGT.

So you need to find a balance between your cooler air supply to the engine, increasing the fueling and (if you go that route) higher boost. I'd have thought that as you have an EGT gauge using that to settle the best balance coupled with the seat of your pants was a good place to start. Then maybe a run on a dyno (though before and after would be better for each change - one by one).

I'd leave the exhaust out of the equation. They have far less effect on turbo engines - unless your exhaust is blocked (or for the wrong engine) its main impact will be on the speed the turbo spools up (ie lag).

The other point about your intercooler is proximity to the rad. I'd ignore this too. The intercooler is largely irrelevant at low revs/speeds because you are running low boost then. Once you get a decent move on there is inevitably going to be plenty of air flow to render heat transfer from the radiator irrelevant.

[Aragorn]

GL88: More boost without extra fuel can reduce EGT not raise it.

If for instance you turn your pump up to the point its black smoking lots your EGT's will skyrocket, increasing the boost pressure can allow the fuel to burn quicker and more completely and therefore the EGTs will drop.

Dervs run cooler when they are lean, think of driving at half throttle compared with on the boards. Half throttle is much much leaner (the same quantity of air is always in the cylinder, as there is no throttle plate) yet runs much cooler.

Also, saying its nothing to do with the exhuast is carp. If the exhaust is restrictive (ie does it have a cat? standard mid box?) you WILL see higher EGT's.

I suspect its a function of the engine producing more power, or the boost pressure dropping slightly due to the longer intercooler pipe run etc?

[David Sparkes]

The other point about your intercooler is proximity to the rad. I'd ignore this too. The intercooler is largely irrelevant at low revs/speeds because you are running low boost then. Once you get a decent move on there is inevitably going to be plenty of air flow to render heat transfer from the radiator irrelevant.

This has NOT been my experience.

It's not so much the transfer by radiant heat while moving at "a decent rate" (just what is that speed, 50 mph?)

Rather it's the fact that the Intercooler soaks up the radiant heat when the car is moving below "a decent rate".

The warm intercooler is a less effective cooler when the engine airflow increases.

I also think it's false to equate low road speeds with low boost.

The OP is towing, probably using high boost in 2nd and 3rd while accelerating. This action will heat the engine (radiator) and throwing hot air into the intercooler, while the cooling airflow due to forward motion is low.

I'd also recommend a free flow exhaust system, by removing cats, silencers etc. The faster flow of exhaust gasses that results not only reduces the transient time for the turbo to speed up, but also ensures it spins faster at any given engine speed, thus the boost is higher at any constant engine (road) speed, compared to a restrictive (standard) exhaust system.

It seems to me that sometimes you are pulling across petrol experiences / generalisations into a diesel application, and they don't always apply.

Cheers

[GL88]

Aragorn,

I own up to being wrong about fueling! There is some useful stuff here: www.thermoguard.com.au/FAQ.pdf which confirms what you say about diesels being the reverse being of petrol engines.

But I didn't say EGT was nothing to do with the exhaust - see my second sentence in that paragraph.

But what you say about boost pressure dropping is interesting given the connection between boost and fueling in the TDi engines. If the intercooler has cooled the air so far that the boost has dropped (ie below the level where the wastegate operates) that might have an effect. http://www.stonefisk.com/doc-arc/def_man/ThermoGuard_Tdi_Tuning_Rev.2.pdf

[cieranc]

Thanks gents, some good reading there. Some more observations from today:

Started up from cold, EGT's higher at idle than with the standard IC with the radiator/engine cold.

Drove for a mile or so until the water temp gague read 86 degrees (can normally 'see' the stat open on the gague) rad still cool, EGT's still that bit higher than normal.

Ran it through town, stat open, water temp 90 degrees, rad warmed up, EGT's higher than normal but only by 15-20 degrees, same as before.

So although I'm aware of the potential for heat soak, I'm ruling it out, for now.

Towing through towns/congestion for me usually means light throttle, reducing road speed rather than increasing revs, and a lot more gear changes to keep the rev range right. Changing hi/lo on the fly if necessary to avoid labouring the engine.

Pressure drop due to increased pipework, there is very little extra pipework, about 3" each pipe. The pipes on the new intercooler have been formed to sit exactly where the original intercooler pipes did, but in front of the rad frame rather than in it.

Exhaust restrictions, I think I'll knock up a bypass pipe for the centre silencer. As with all my mods I'll make it so the ends are the same as the silencer and it'll be a straight fit. Then if the increase in noise bugs me, I can always bolt the silencer back in

Am I sure I'm not just enjoying the extra power? Well, yes I'm enjoying the extra. There is a definate increase in useable power, and a negligable decrease in somke. At top speed (thats about 60mph for me) the engine seems to run smoother. But the whole point of fitting this intercooler was to reduce the EGT's prior to tuning, and the EGT's have risen.

We've proven the fault with our Iveco today (suspect weak spring in the wastegate actuator), so I'll get my gague back and start experimenting.