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Some of this week's Letters to the Editor, discussion group posts and other feedback!

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Water/Air Intercooling

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Having just read your article entitled "Frozen Facts", I was interested to find out if you have ever conducted testing with water/air intercoolers using a liquid other than water. I run a Spearco water/air intercooler on a Nissan Z18 turbo and I find it to be quite effective, having reduced the inlet charge to about 22-23 degrees Celsius under load (14psi). The current fluid is a mixture of standard automotive coolant and water. This has resulted in consistent dyno runs of 116kW at the wheels. It has been suggested that I could replace the coolant with something that can be cooled more efficiently to improve the power further, but I am unsure as to what liquid would be suitable. Alternatively, I wonder how effective the freeze spray would be if sprayed onto the heat exchanger? Just curious if anyone has undertaken this kind of testing.

Jeff Burns

The efficiency of a water/air intercooling system depends on a number of factors, but one of the most important is the heat-carrying capacity of the fluid. In this respect pure water is the best commonly-available fluid - its thermal mass is actually downgraded a little by the addition of automotive coolant. However, the use of a corrosion inhibitor is recommended. The major advantage of a water/air intercooling system over the more common air/air design is that the system is slow to change in temperature - making it better able to absorb the temp spikes that come when the engine is on boost. However this same characteristic makes the system fairly unresponsive to short term cooling sprays.


Gday firstly great magazine, great articles. Could you guys get into more depth on turbochargers ie Japanese, Australian, American brands, hp ratings, specs, etc Thank you.

Nick Ristuccia

We could do an article on that topic but in the real world, the usefulness of that information isn't all that great. Very little information is available (eg compressor maps are very rare) and anyway, the best matching of a turbo to an application almost always requires trial and error assessment on the road.


Just a quick note to let you know that after so many issues of AutoSpeed, I still look forward to the next one to "arrive". I'm also looking forward to the changes that are soon to take place, change is always good, even if nothing is broken.

Thanks again, all the hard work is appreciated.

Craig Stampfli


Noisy FTO Engine

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Can someone in your technical department help with this one? Is it normal to place much weight on the sounds heard inside an engine at idle using a stethoscope?

I am on the brink of buying a Mitsubishi FTO GPX with 80,000kms on the clock. I had it checked over today by a garage that specialises in imports and received a slightly concerning report.

They said that despite performing and idling smoothly, the engine is tappety at idle (something I had noticed). For that reason, they put a stethoscope on the heads (presumably at idle). The front bank of the V6 sounded fine apart from the aforesaid tappety sound. But the rear bank had a "rough" sound coming from the cams, which was noticeably different as tho' something was worn or otherwise amiss.

The garage concerned doesn't really know FTOs (no-one in Brisbane seems to know much about them) so I informed them that the engine (which is the MIVEC version) has adjustable tappets/valve clearances, unlike the non-MIVEC V6, which has hydraulic tappets.

Together, we therefore speculated the following possibilities:

1. The tappet adjustment is out and causing some unusual friction induced sound (highly unlikely I would have thought);

2. The rear bank of the V is the "torque" producing (?) bank and therefore under different loads (his suggestion - I have never heard that one bank of a V configuration produces or undergoes different torque loads. Is it possible, particularly in respect of the cam drives?);

3. The wrong oil is in the engine (I spoke to the guy who complied the car recently and he uses Shell Helix 20W-50. I would have used a fully synthetic oil in an engine like this, however, is it really possible that a 20W-50 oil could produce weird noises in (part of) an engine?

4. The engine has been thrashed with an inferior (or dirty) oil in it or is suffering oil starvation to the rear head and has therefore worn a cam or both cams;

5. Some combination of the above...

All in all, pretty off-putting. Can you guys shed any light on the above?

Mark Northage

We can't think of any good reason why the two cylinder banks should be making different noises. Many Japanese import cars have had bad maintenance and have tired engines - especially for the distance that they have travelled. Unless the seller is prepared to offer a cast-iron long-term warranty, we'd suggest that you don't buy the car. After all, you've had it checked to see if there are any problems - and it appears that there are!

Wild Sprite

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I have Julian Edgar's book - 21st Century Performance - and find it really informative, well done!

I thought you might get a kick out of my own project, my road/race '58 Bugeye Sprite.

I have just finished installing a Datsun A14 engine, to full race spec, but with 9:1 compression and an Eaton M62 4th generation supercharger running at 1.7 x normally aspirated volume. This gives 200hp at 7,500 on the engine dyno. Sequential injection, Commodore coils, and an Autronic SM2 ECU also used. (I'm a transplanted Kiwi hence use of Down-Under gear.)

Amongst a bunch of other mods I have also installed a modified MX5 rear end, narrowed by 340mm, turned 180 degrees back to front and with a Nismo R180 competition diff.

Here's a couple of pictures.

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I plan to intercool it over the (Canadian) winter, but to me intercooling by itself would not give an immediate performance increase when using a positive displacement blower, or am I wrong?

It seems to me that the blower will pass a fixed volume per revolution, regardless of what happens downstream, therefore the engine will see only that weight of air.

Temperature and hence pressure in the manifold would be affected by intercooling and any power increase would have to be due to being able to:

a) run more advance

b) lean out an overly rich mixture

c) run the blower at a higher volume

I know you're busy but a quick comment would be very welcome.

Also, I haven't done the numbers to see if it makes any sense, but do you know of anyone who has installed the evaporator section of an airconditoner in a plenum as an intercooler/chiller, using of course the rest of the a/c system as normal?

Richard Paterson

Hey, looks like a fun car! We would expect intercooling to give an immediate improvement in performance, not only because you could run more advance (and a Roots blower on an old engine design with 9:1 compression must mean that you have it pulled back a long way!) but also because the density of the air will be increased and so the blower efficiency will be effectively improved. We think that using the air-conditioning system as part of an intercooling system has huge potential. People tend to dismiss this idea, believing that the power draw of the compressor will more than offset the potential engine power gains, but they lose sight of the fact that you don't have to have the compressor running at the same time as you are making use of the temperature reduction that has been generated. The best approach that we have seen is the one covered in our article: "The Patent Files: Refrigerated Intercooling"

Fords Too?

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After reading your article on tuning the Holden V6 ["Holden V6s with Leon Vincenzi"] , I was wondering if you had done anything similar for the Ford 4L, or if you might be doing that any time soon?? Apparently there was a Ford/Holden show over there in Adelaide recently (my brother went to it) and some guys were saying that the 4L has huge potential with only minor mods (much more potential than a 3.8 V6 so they said, not that I'd argue about that with anyone...)

I'd be very interested in any info you might come up with in that regard. Thanks for a great site.

Geoff Pryde

Unfortunately, there is no equivalent of the Kalmaker software available for Fords. We've shown some of the engine management changes that can be made with Fords in the article "Real-time Chip Tuning" and we have another story coming up on the gains made by real-time chip-tuning a current Tickford V8. Probably the best result we have seen on the Ford six we covered in the story "Lesson Dealer".

Subaru vs. Aftermarket Filters

Guys, you may already be aware of this - but I will tell you anyway. A friend of mine who works as Supervisor in a Subaru dealership has received an emergency bulletin from Subaru Australia in relation to non-OEM air filters. It seems that the oil from the air filters is destroying the airflow wire in the meter. Subaru Australia is NOT covering warranty claims for these meters. I am now personally not happy because I have a K&N filter pad in the original airbox on my Subaru and now have to replace it with an OEM filter at something like $38 a pop. Handy.

Have you guys heard anything similar??

Shane Fisher

We have mentioned something similar in an article, but thanks for bringing it to everyone's attention.

Hi-Flow Cats

I was interested in upgrading the cat on my Nissan Skyline R32 GTS4 to one of those so-called 'high-flow' types. I've done a search through your site, in the hope that you may have done a comparison on the available models, but couldn't seem to find such an article.

Would appreciate your input into my decision.

Greg Brown

We haven't done any cat converter comparisons, but an easy and effective rule of thumb is to select a cat converter one size larger than the pipe diameter being used for the rest of the system. For example, use a 3-inch cat with a 2?-inch exhaust, making sure that the pipe size transitions are through tapered cones. Taking this approach almost guarantees good cat converter flow.

West Australia?

AutoSpeed is fantastic!!

You have done a great job with the publications you have done so far except....

There has not been much from W.A.

I know it's a long way but it would be great if you could do some stories about West Aussie cars and people. One person in particular who I would love to see an article about is Bill Lee. This guy is an absolute Holden performance guru!! I know you have just run a story about Leon Vincenzi and all but what the hey, it will probably take you guys a while to organise flights, accommodation etc....

Keep up the good work

Marcus Towner

It's always a juggling act when selecting the destinations for editorial story-gathering trips, but we have been discussing a Perth visit.

Intercooler Water Spray

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I've heard some great things about the Intelligent Intercooler Water Spray unit and have read over your article. [Series starts at "Intelligent Intercooler Water Spray, Part 1" ]

I have a Pulsar GTiR that suffers from the old heat-soak problem and would prefer to try the water spray solution rather than the front-mount (overkill) solution. One thing your article didn't seem to address was which type of pump and nozzle to use.

Any advice you may have would be most appreciated.

Sean Rainey

We're very proud of the Intelligent Intercooler Water Spray Controller and are pleased that you have heard it praised. Part 2 of the series ["Intelligent Intercooler Water Spray, Part 2"] recommends a VDO/Holden pump (Part No GM90058691) and its accompany grommet (Part No GMVS20344) being used with a Spraying Systems TX-4 ConeJet spray tip. It also suggests that this nozzle should be used with a Spraying Systems 4193A combination filter/check valve. In Australia, ring Spraying Systems direct on 03 9318 0511 for your nearest stockist.


I'm looking at a front mount intercooler for my Japanese import Version V STi Impreza WRX. I'm not sure whether to go bar and plate or tube and fin. Both cost similar amounts and are the same size. I know tube and fin cools better than bar and plate (which flows better) but when we are talking sizes this big: core surface area 1848 cm2, core measurements of 660 x 280 x 75mm, then I was wondering if the bar and plate will be the better choice. The STi is running a VF28, Unichip, full 3-inch exhaust and about 17 to 18psi of boost. The car is used 99% on the road, maybe one track day a year. It is used for mostly urban driving as daily transport, with a good high speed run through the windy hills roads a couple of times a month.

Thanks for any opinions you can provide.

Roger Canty

Because we have never seen any detailed comparison testing of two intercoolers identical but for their construction type, we can't answer your specific question. We're also curious as to how you have reached your conclusion about the advantages and disadvantages of each design - if you have seen good quality testing, we'd love to also see the material.

However, it seems to us that the first thing that you need is some information about how well your current intercooler is performing. Is the STi cooler working satisfactorily? This can be assessed for less than $30 and with little effort, driving the car as you do normally.

Firstly measure the peak boost pressure in front of the intercooler, and then do the same by tapping into plumbing after the intercooler. For example, in your case the boost after the intercooler might be the 17-18 psi that you are measuring in the intake manifold, while the boost in front of the 'cooler might be (say) 19-20 psi. While any boost loss is a performance negative, a few psi is fairly typical of all intercoolers and is not of great concern. If you have an assistant who can study the gauge closely, also see if you can detect a different rate of boost increase at the two test points.

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Next, measure the intake air temperature. A cheap and easy way to do this is to use the Thermometer Module available from the AutoSpeed shop, placing the probe somewhere into the intake system after the intercooler. We have covered how to do this in a story - "LCD Temp Display!". Make sure that you monitor the temperature over a long period - weeks if possible. Just temporarily stick the display on the dash and occasionally look at it during your normal driving. In almost all road-driven turbo cars, the highest temperatures that you will ever see are when you are stuck in city traffic on a hot day - not on any boost at all! This is especially the case with an underbonnet intercooler like that found in the WRX.

When you have collected your information, then you can make a logical decision. If the pressure drop across the intercooler is high, fit the aftermarket unit. If the intake air temp is always way above ambient (eg 20-40 degrees C higher), then fitting a front-mount will bring that down a bit as the core won't be being exposed to underbonnet heat. But if the intake air temp is reasonable (eg as soon as you get moving - even when on boost - it drops quickly) and the pressure drop is also low, then you're simply wasting your money buying a front-mount. Fitting a good quality water spray will help the underbonnet intercooler drop in temp quickly once you start to move, and the AutoSpeed Intelligent Spray Controller is ideal for this because it monitors actual intercooler core temperature as one of its inputs.

It's always horses for courses - and in the case of a car driven as you say your car is, then it could save you a helluva lot of money to do some simple measurements first. There's no magic power in intercoolers - it's just the lowest intake air temp at the lowest pressure drop, that's all.

Er, Yes...

Can someone tell Mr Cremer that is it aks not ask!

Ben Adcock

Is that so?

Engine Management Load Sensing

I would like to start by congratulating you on providing a great resource! Since joining, I have scoured your site for knowledge and found a bountiful supply. I have also bought "21st Century Performance" which I love. I do have a question relating to engine mapping that I cannot seem to find a clear answer to. Could I suggest it as the subject of one of your technical features?

The aftermarket EFI systems that I have looked at (as well as the OE ones, I would assume), all contain (amongst others) maps for Fuel and Ignition which are calculated against Engine Load. My question is, on a Turbocharged Engine, how do you accurately obtain Load? Looking at the MoTeC configuration options, they provide five methods of obtaining a Load (or Efficiency) value. These are:

  • Throttle Position
  • MAP
  • MAF
  • (EMAP=MAP sensor measuring atmospheric or exhaust back pressure, BAP=manually entered barometric pressure, MAF=mass air flow).

The most accurate option would seem to be (2) as this would provide a barometrically corrected (ie absolute) value for the pressure in the inlet manifold. What I am not clear about is: what is the relationship between the pressure in the inlet manifold and the engine's load? As soon as the turbo has reached full boost and the wastegate is in operation, would the pressure in the inlet manifold not just be the maximum boost pressure? If this is true, how would you differentiate your fuel map between say 4000 and 6000 RPM? Would you need to? All very confusing.

Matthew Knight

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The most accurate way of measuring a steady state engine load is with a mass airflow meter. However, many engine management systems (some original equipment and most aftermarket systems) do not use mass airflow meters. Instead, they measure three parameters and from this calculate the assumed mass flow. The parameters are: manifold pressure (positive or negative with respect to atmospheric - it doesn't matter); intake air temperature; engine speed. Using an internal model that takes into account the volumetric efficiency variations at different loads, the program can then approximate the mass airflow.

So in your specific example, the ECU 'knows' the temperature of the intake air and the manifold pressure (and thus its density), and the rpm of the engine. It therefore can assume with a fair degree of certainty that the mass of air being breathed will be higher at 6000 rpm than 4000 rpm. The tricky bit is that you can have a boost pressure of (say) 15 psi with an intake temp of (say) 50 degrees C and an engine speed of (say) 4000 rpm - but at half throttle there will be less flow into the engine than at full throttle, even with the other factors being the same. So in pretty well all factory management systems using a MAP-sensing approach, throttle position is another input. All factory cars that use MAP sensing measure atmospheric pressure at least on start-up; some also measure it occasionally during vehicle operation.

Note that as you have pointed out, some aftermarket systems get away with just throttle position, rpm and intake air temp inputs. There are even factory systems with just these parameters. However, very extensive mapping is needed if the engine is to be happy when undergoing transients - for example the throttle position sensor has to be accurate and have sufficient resolution that its speed of opening, for example, can be assessed. In fact in transients, a MAP sensor provides a better signal than an airflow meter - which is why some factory systems use both approaches simultaneously.

So in summary MAP sensing alone isn't used to determine load, it is used along with engine speed and intake air temperature.

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