Greg H.

This is related to Kevins Motronics tuning options thread. Kevin and TB state that one of the limits to power is intercooling. Esoteric and expensive aftermarket intercoolers are a continuing source of discussion. What I want to know is why no one ever considers intercooler misters. I hang around Audiworld.com a bit too much but the Audi boys, who run a lot more boost than we do, run intercooler misters quite sucessfully. They have proven that it works and can keep intercooler temps very close to ambient. There are even controllers on the market that can cycle the water mist according to boost pressure or intake temps. Unless someone reply to this thread that I'm crazy, this is going to be my next mod.

Greg H.

TB993tt

Greg
I am assuming you mean spraying mist over the top of the core (rather than into the intake)
The only real use for this is to maintain the power which you have eg if your car puts out 408PS DIN and you run in 35degC heat, the intake charge temp would naturally increase to a greater level than at DIN (20degC ambient) so your actual power produced would be lower. Enter the spray which should reduce the charge temperature to some degree and increase the power output compared with a non spray motor under the same elevated temp condition - but you obviously still won't see more than or even close to your 408PS at these ambient temps.

To actually take advantage of a proper more efficient I/C like the ridiculously expensive Secan, the engine must be mapped accordingly - the problem with the spray system is IMO if you try and map the motor under DIN conditions with the spray activated all the time then yes you could gain some power using the extra efficiency, but what happens if (in your spray mapped car) you are flat out in 5th running up through the revs and you run out of water - suddenly the I/C efficiency drops back to stock and best case your motor retards the ignition and drops the boost, worst case you start melting things

If anyone can come up with a system for our cars I would be interested in having one

Geoffrey

Can we maybe define what we mean by an intercooler not being efficient enough? There are two main things to be concerned about with an intercooler and that is the pressure drop across the intercooler, and the cooling efficiency. Does anyone have a range of temps that is acceptable? Obviously, the lower temps are better for more dense air, but when do you consider the intercooler to no longer be able to properly cool an engine?

I have a significant amount of data logging from various turbocharged engines, mostly Porsche race cars and they all tend to have air intake temps be in a range of 100-120 degrees F. Here is the logging for air temp from 1 3.6l engine producing 576hp@1.0bar to the wheels on a Dynapack dyno (call it whatever you want in terms of power). This was on a 90 degree day at Summit Point race track and it had a custom intercooler that wasn't even ducted and didn't look all that nice. It is showing a constant 103 degree F temp. Is that bad? Does it need a Secan intercooler?

Obviously the cooler, the better, and I begin to shut an engine down when the air intake temp reaches 140F by retarding the timing so the engine no longer runs properly to prevent driver's from damaging the engine. I don't get concerned when I see 120F, or even 130F. So help me out in understanding the concern over a $17k Secan intercooler when a poorly ducted, generic, nonspecial intercooler on a 575hp to the wheels engine can cool the air to within 15 degrees F of ambient air?

The only time I've seen much better is on a marine application where a water to air intercooler is used and then, depending on the water temp, the air temp into the engine can be below ambient.

TB993tt

First thing readers must know is that Porsche Motorsports comissioned the Secan intercooler to be developed and that ALL the race teams used it - these people could use whatever they want and surely they could have saved themselves some cash and designed something similar ?

I am struggling to understand the graphs posted, they appear to show a constant 50degC over time ?
If this is the case then this doesn't match my experience when observing via the car's port the intake temperatures which the Motronic is seeing. It will rise to higher levels than these ~55DegC very quickly then as soon as the throttle is shut it will fall quickly (regardless of I/C) - The only time the intake temp will stay constant is on a steady throttle which apart from WOT in 6th is difficult to achieve so what's going on - or is the time scale very small ?

TB993tt

To address the first part of Geoffrey's question "what do we mean by an intercooler not being efficient enough ?" (think that's what he meant )

OK forget chassis dyno and aftermarket tuners/club racers for a moment. Manufacturers and the best race teams use engine dynos and have protocols in place. The differences in protocols together with the facilities available and finally the ingenuity of the engineers are what differentiates these top teams.

Experience of track data and engine dyno data for a specific type of engine lead to experience which when a certain level of expertise is reached means that the engine dyno can be set up and used to produce engines which will perform in a known way on the track (more or less)

For Porsche turbo engines, Rheinhold Schmirler is acknowledged (by those who know - not me) to be the best with the most experience and most meaningful facilities which have proven themselves again and again where it counts. They recently worked with Bosch in developing the latest engine for the Alzen race 996tt.

Through this experience they know very precisely how hot the intake air can get on their rig (which is unique to them) before the engine will have problems. So although getting to this level is difficult and complex, actually sticking to the limits they have set is probably relatively simple and the stock 993tt I/C has a limit which I am at or thereabouts and they tested numerous other I/Cs before the Secan came out - I have seen first hand their I/C "graveyard" - AGAIN they are not watching some data from the track they are on their proven rig under identical controlled conditions and only the SECAN will allow more power (RS power that is - another can of worms which is the other half of this question )

The combination of components to go above this ~ RS 550PS level is again relatively complex and expensive but the I/C is the key and as Kevin alluded to before, specifically the cores - AND they are going to be $27K US unless someone can suss out how to copy them

Kevin

Greg, the "Stock" intercooler is very good. However, it does need some help. Heat soak with the car idling produces a time delay or transistion period when the car starts to move and clean cool air starts to flow into the wing. When I put a turbo car on a dyno, I will always have a garden sprayer near by. I will hose down the intercooler prior to a run to minimize/cancel the heat soak. One can immediately see the water evaporate from the core. I have a nice IR heat gun and note the temps. I like the Aquamist pumps. I would recommend installing a mister system since you track your car. I'd set the pressure switch at .7 or.8 bars and see how long you can keep the fluid in the stock windshield tank. I'd also wire up a manual switch to turn the pump on to knock the heat soak down prior to a race.

This is a bandaid approach, however, until data can be finalized for a better intercooler this is definately a positive step in the right direction. The only negative is, if as a driver you are pouring it on to win the race, the mystery question is has the tank run dry. A simple solution would be to wire in a float switch to tell you when the tank is low or dry..

Jean

For some reason I cannot see the links or pictures posted by Geoffrey.
I will be soon installing temperature sensors on my engine for my MXL datalogger, I made sure I got sensors for the intake, cylinder head, throttle position, boost pressure etc.. and I will be posting what I learn. This test can obviously be done on a dyno but the running conditions might be more applicable, especially in our hot weather here (still 40 degrees C today!)..
Also, for more candy, I am going to install the aquamist system (spray on the intercooler cores), more in theinterest of testing and out of curiosity rather than because I truly believe it will help.
I will be mpore than happy to share all the datalogged data, it will be maybe in month's time. That will be tested on the track and under normal driving conditions, and at different boost levels and octane.

Geoffrey

Ok, I changed the scaling on the above graph and included all of the channels I have on this particular MoTeC Interpreter template. The scale at the bottom is the number of seconds of logging.

I get the point that there are many people out there who are smarter than me and who have sophisticated test equipement and have performed controlled tests. I am also not disputing the quality of a Secan intercooler, in fact, I've never seen one to comment. However, my question still stands. Furthermore, for a primarily street driven/club track car, how much do you need?

As I give more thought as to your question of why isn't the temperature moving around much I think I know the answer. I checked the Air Temp Sensor setup on this particular file and the air temp sensor is a standard Bosch NTC air temp sensor, not the Bosch high speed air temp sensor I would normally use in a turbocharged application. So, I suppose it is more an average than direct data.

Here is a second piece of data from my 911 Turbo on a similar day. My fresh air intake is in the back of the engine compartment with no access to clean fresh air so the incomming air is much warmer than the above data. You can seen the much faster response of the Bosch high speed air temp sensor in this data.

NineMeister

Misting the intercooler core utilises the latent heat required to convert the liquid water into vapour. The downside as mentioned above is that the only reason to use it is if the intercooler is not capable of cooling the intake charge sufficiently in the first place, which leads on to the discussion about intercooler efficiencies, i.e. flow efficiency and heat transfer efficiency.

Without access to design data for specific cores it is pointless trying to prove which is better than whatever because we are not in a position to quantify the differences. Making the assumption that TB suggests that the Secam is the most efficient core available, does this mean that all other intercoolers are not up to the job? No, of course not, it's just that you have to compensate for the alternative core's inefficiencies.

Looking at charge air flow first, if core A is more restrictive for a given core area, at some finite larger area the flow restriction will be reduced to that of the Secam core. Similarly if the cooling efficiency is lower, again at some finite larger size the heat capacity of core A will be the same as the Secam. The conclusion is that the Secam will be the smallest intercooler that you could use for any given requirement, however IF you have the space available to fit a larger intercooler, it can do the same job as a Secam, period. I agree though that if space is strictly limited (which is the case with most 911 applications) then using the most efficient core possible makes the most sense, which is probably why Porsche and others choose the Secam core.

So how do you know if your intercooler is working correctly? The only measure of a radiator is its ability to reduce heat levels, so simply looking at the difference between ambient and intercooler outlet temperature is the only measurement required, but since no radiator is 100% efficient there has to be an acceptable temperature gradient. In my experience maintaining a 10C (approx 15F) raise with flash increases of up to 15C is as good as it gets, so if your data supports this you can rest assured that your intercooler is working well enough for the requirements of your engine.

Jean

Colin, this is surprising, or you forgot to mention pressure drop! You want an intercooler with the largest needed area WHILE maintaining pressure drop to a minimum, one way to do that is through very efficient flow in the cores, which is were the strength of the SecaN lies, in getting both together.

When you mention maintaining differential under 15F, under what conditions do you mean? RPM, load and time (in seconds)?
Thanks

NineMeister

Intercooler pressure drop is the measurable result of internal flow efficiency, so I did not mention it as I thought it would be a pretty obvious association, sorry if this was not the case.

My take on core flow efficiency or pressure drop if you prefer is that if you have say a 2psi drop across your existing core and would like to reduce this you can simply fit the same make of core with perhaps a 50% greater area, possibly reducing your measured PD by your target 1psi.
Of course although a low pressure drop is most desirable, reducing PD may not always help performance, because if your engine is running at your required boost in the intake manifold, increasing the available boost can have no direct effect other than bringing in the wastegate control earlier.

Naturally, in principle, it is better to run the turbo as efficiently as you can and so a low back pressure (high flow) core is preferable, but don't assume that unless you use the most efficient core available that your engine will not make power, it will, it's just that the turbo will have to work a fraction harder to produce the same manifold pressure.


As for maintaining the temperature differential (intercooler outlet to ambient temp), flash readings through the gears on the track (perhaps 20F for less than 1 second) is acceptable provided that the overall (mean/average/w.h.y.) temperature difference is maintained at 15F or less.

Possibly the opposite is probably true for you guys with fast road cars where (in theory) you could hold the car flat in 6th for 50 miles (would that be 15 minutes on a 20 gallon tank with a 700bhp engine?) whereby any heat soak in the core would be potentially disasterous for the engine. This is where all standard 911s suffers in having the intercooler above the engine at the back of the car which is not exactly in the air stream and relies on the ability of the engine fan to get enough air through the core.

K24madness

Colin,

I just want to say that I enjoy reading your posts. Always fact driven not hype driven. On this one I really like how you put the "real" world driving into perspective.

Geoffery that goes for you too.

Tom