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Some of this week's Letters to AutoSpeed

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DFA for MAP?

First, I'd like to say great job on your articles - I am a regular reader and look forward your updates. Relating to article The Digital Fuel Adjuster, Part 1, you refer to using this device with an airflow meter. Can cars with MAP sensors use this device or do we have to upgrade to airflow meters?

Colby Au

Yes, the DFA can be used to alter mixtures on a car using a MAP sensor load input. However, as is the case with all interceptors used on MAP systems, the results won't be as good as in an airflow meter car.

Injector Bleed

I previously designed an electronic boost controller using PWM but until now couldn’t find a cheap source for a suitable valve. I was looking through some old parts at my father’s workshop and saw a set of RB30 injectors that I had salvaged from a blown engine. Suddenly it dawned on me that they could be an excellent as a variable flow valve for all sorts of boost/vacuum devices. Do you think they would handle the flow for a boost controller?


We doubt a fuel injector will flow sufficient air – but there’s only one way to find out! If you give it a try, please let us know how it went.

Stuff Ups x2

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Just a couple of minor corrections to the Beemer story this week Bent-Eight Beemer – first, "lightning quick" instead of "lightening quick" (the electrical bolt as opposed to making something lighter) and was I wondering if you meant "high-paid executive types" instead of "executive tyres".

Keep up the great mag.

Michael Machin
Republic of Korea

Thanks for that – well spotted. Article fixed.

IEBC Coverage

I just stumbled across the new Do-It-Yourself electronic boost controller project (IEBC) at Jaycar and your site - are you guys going to do a test on it soon?

Kerry Novak

Yes, we do plan to do a series on using the unit - stay tuned!

IEBC Problem

I am looking forward to your review on the IEBC (Independent Electronic Boost Control). I have purchased one and have it installed but have come up with a small problem... When changing the duty cycle setting, the IEBC sometimes (actually more often now) jumps it up to 127% for no reason and then it proves very hard to step the duty cycle down again in either single or 4 step modes. I am able to select any load point with ease; the problem only seems to lie with the DC. At the moment I cannot reduce load point 32 below 90% DC (it keeps jumping back up to 127%), so the IEBC has been disconnected. I have checked all connections and components bar the ICs and was wondering if you were able to shed some light?

Jon Stow

The first IEBC kits had a problem in the PICs - take it back to Jaycar and they'll give you new PICs. (If you purchased it from the AutoSpeed shop, contact them for exchange PICs.)

Ohms Fix?

I am enquiring about the Digital Fuel Adjuster. I have a Holden VL Turbo Calais and have brought Skyline GT-R injectors. I have been told that these injectors run at a different ohms to the RB30 ones - I was wondering if, using this kit, I could change the signal so that it runs the GT-R injectors correctly?

Lars Copcutt

No, the DFA won’t get around the problem of different injector impedance.

Laptop Programmable DFA?

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I have a question about the Digital Fuel Adjuster. In your article The Digital Fuel Adjuster, Part 1 it is said repeatedly that there is no need for a laptop. My question is would you be able to use a laptop if you chose to? Larger screens allow for faster changes and better monitoring. It may cut down on your handheld controller sales, but it would be a lot more convenient for a consumer like me.

Kyle Bateman

No, the DFA is not designed to run with a laptop – it’s the hand-controller or nothing. Note that the hand-controller is very simple to use and the display is high quality.

Uniden Unit Upgrade

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In your story Testing the Uniden GPS301 you say:

"The over-speed warning has zero tolerance (not a bad thing) but on one section of road insisted the speed limit is 100 when in fact it is 110 km/h.”

This is not a speed limit warning - it is merely a warning based on a pre-fixed (by you, the end user) speed, which makes it a bit less useful than a speed limit warning. I bought one of these units as soon as I read about them on newsgroups and found that, with the serial cable connected, you can actually plot your trip as you go (it uses NMEA protocol). I am using Oziexplorer with high resolution satellite maps downloaded from NASA - and the results are pretty good. A screen dump can be found at

Basically, I drove around for a few weeks with my laptop on the passenger seat hooked up and capturing my various routes to work, etc. One thing that was disappointing with this unit was when I upgraded the database just before Xmas and drove to Brisbane - it didn't warn me of about 5 speed cameras and warned me incorrectly of another (where the RTA moved it to the other side of town).

Overall, I guess this unit will be handy in states/territories where they don't have warnings for fixed speed cameras. It was also handy to know my exact speed, rather than the WRX chosen displayed speed. I'd say - apart from the databases not being very up to date, apart from a black spot warning taking priority over a red light camera warning and that it doesn't have a database of speed limits - I am reasonably happy with this unit. Especially given its NMEA stuff that can turn it into a data logger for speeds, distances, elevation, etc.

Anthony Hamlyn

Temp Switch Load Capacity

I am interested in using your neat little temp switch (AutoSpeed Shop). Question - can it handle 20 amps at 12 volts? What cycle life can we expect at this amp load? Can we mount it to a surface with epoxy?

Bill Heath

For high loads, we suggest running an automotive heavy duty relay that’s triggered by the unit’s onboard relay. Try to avoid mounting the unit using epoxy - it fits into a standard 'jiffy' box.


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I own a 2003 Toyota Corolla with a 3ZZ-FE 1.6 litre 4 cylinder engine. I would like to find out if the Twin Turbo Zet would fit my car and whether the engine will remain good even after hard driving. Also what would be the cost of the part?

Omar Tiwana

If you haven’t already, see The Twin Turbo Zet - this article details cost and everything you need to know. The effect on engine life would be minimal – if any.

Left Out!

Just a quick note regarding what I think is an omission from the Cheap Cornering Contraptions - Part Two article. The Ford KF-KHII Laser (1990 - 1994) - any model featuring power steering and the 1.8 litre BP engine - is a car with a great ride/handling compromise and sharp steering together with an engine with lots of flexibility and low rpm torque (relatively speaking). Okay, so it's not an obvious choice but it's more fun than it would seem!

AutoSpeed is great, I’ve just renewed by subscription again!

James Whitbourn

Smart Steering Wheel Mod

Regarding your Investment in Mods - Part One article - you mentioned how you can't alter the steering wheel on an airbag equipped vehicle...

I actually changed the airbag wheel on my old airbag equipped Soarer GT-LTD (SC400) to an airbag wheel from a later model. The steering wheel from the Soarer wasn't particularly sporty, but I wanted to retain the 'factory' appearance with a replacement 'sports' wheel. Also, I wanted to retain the airbag for safety.

What I did was I purchased a steering wheel from the latest model SC430, which is a slightly smaller diameter wood grain, three spoke wheel (which also gives steering wheel stereo controls, which I had to wire myself).

I then ran into the difficulty of fitting an airbag. The SC430 airbag has dual stage power inputs while the SC400 runs on single stage. To get around this, I did some research and found another model Lexus had single stage inputs and a triangle shaped wheel. The service manual and wiring diagram confirmed that the electrical current to the airbags from the Soarer and the other model were the same - so I did some hunting and found the appropriate airbag and connectors and fitted the wheel. It was very easy with the new steering wheel sharing the same spline as the old one and all the new airbag required was a new connector to ensure the airbag didn't deploy and I wasn't stuck with an annoying 'AIR BAG' warning light. However, it took me months to find the right parts as there was only one model ever made with the specific airbag I needed.

The result was fantastic - a much sportier wheel while still retaining the airbag. I did have to get the wheel and airbag recoloured to match the interior trim, but after this was completed it looked great and totally factory. While I used different models, for other vehicle applications it might even be possible to change wheels from later - or 'Sports' - models. I never had an accident in the Soarer, so I never 'tested' the airbag – but, then again, it never inflated while driving either...

It’s not an 'inexpensive mod' but a way to get around the problem of factory air bag steering wheels. The cost isn’t so bad if you chose to use second hand parts like I did.

Tom Eastlake

We stand corrected! Congratulations on your creative upgrade – we’re very impressed.

New Fuel and Boost Controller Results

From the Skylines Australia Forum:

Just finished tuning the Stagea with the Jaycar Boost Controller & Digital Fuel Adjuster. There was a half hour window where the 4wd dyno and the operator were both free at the same time. Tuning took all of 20 minutes on the rollers with Dyno Dave running the Dyno Dynamics and yours truly pushing the buttons on the Jaycar Controller.

With ZERO mechanical changes (std exhaust, std intercooler, std airfilter etc), just the 2 Jaycar electronic controllers fitted, we managed 132 4wkw at 10 psi running a nice and safe 11 to 1 AFR's. At midday on a 30 degree plus day, with no temperature correction applied. That's a good 30% improvement over standard, for an all up cost of AUD$380 in parts and dyno time. That's what I call good bang for my buck.

As well as making more power, I also leaned out the AFR's to a more fuel economy friendly 14.5 to 1 at the lower rpms (off boost). The standard AFR's were 12 to 1 off boost and went as high as 9 to 1 on boost, not good for power or fuel economy. I would have liked to go a little leaner than 11 to 1, but the ignition timing was getting a bit advanced as I pulled more fuel out of it with the DFA lowering the AFM voltage. It was the usual piggy back compromise, no doubt exacerbated by the standard exhaust, compliance cat and standard intercooler. I could trick the standard ECU just so much, then it would pull ignition timing and dump a whack of fuel in.

My biggest single observation with the Jaycar DFA was how easy it was to get rid of the usual RB25DET power dip around 4,250 rpm. With 100 settings at 128 load points I could fine tune it so easily. There is simply NO DIP, and anyone who has tuned an RB25DET will tell you that is hard to achieve with piggy back controllers.

Next step is to fit the cat back exhaust and I am expecting to pick up a good 20 4wkw with that.

For the rest of the thread, see

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