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Some of this week's Letters to AutoSpeed

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I have a 2.2 litre ‘99 Subaru Impreza and was wondering if the electronic blow-off valve (The All-Electronic Blow-Off Valve!) will work on it? Also, what is the price and shipping cost to USA ?


Blow-off valves are designed for use on engines with a turbo or supercharger - don’t bother if the engine is naturally aspirated. But let’s assume you’ve already fitted an aftermarket turbo or blower kit to your Subie... Note that you’ll also need to find a suitable electronic valve – details are discussed at The All-Electronic Blow-Off Valve!

Varying DC Motor Speed

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I read with interest you article on modifying the DC motor speed controller to take a 0-5V input from an engine sensor (Motor Speed Control Module - Part 1). I want to automatically vary the speed of a motor from the signal of a temperature sensor - do you have any ideas how to do it? I need to run the motor faster as temperature increases. The sensor I have has a voltage that decreases with increasing temperature - it's about 3.3V at 20 degrees Celsius, 2.2V at 40 degrees Celsius and 0.5V at 100 degrees Celsius.

Scott Elliott

We don’t have any practical suggestions to help with this one.

Closed-Loop Control on IEBC?

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I've read and enjoyed your articles on the Independent Electronic Boost Control (The Independent Electronic Boost Control, Part 1) but was left with one question... You mentioned that the system was not strictly speaking a closed-loop system. However, I was wondering if there was a possibility that the system does end up closed-loop with positive feedback? Assuming the boost controller is programmed to increase boost with increasing load, then as load increases so does boost - this in turn increases load, which in turn further increases boost and so on (like a microphone held near a connected speaker). Obviously, implementation factors will always govern whether this happens in any particular installation.

Peter Bodon

The IEBC is more intelligent that a normal wastegate bleed, but it isn’t closed-loop because it does not have feedback from a boost pressure sensor.

Compression Ratio Issue?

In all of your recent articles about turbo charging and supercharging you never mention anything about lowering the compression of the engine. Isn’t this a necessary part of the conversion?

Andrew Del Carlo

Lowering the compression ratio is not essential when adding forced induction. However, when the standard compression ratio is kept it becomes even more important to have accurate control of ignition timing and mixtures, efficient intercooling and relatively modest boost pressure.

How Fast?

I am wondering what the world record for quarter miles are - particularly Top Fuel dragsters. I don't know where else to go for this info, so I hope you can help out. Keep up the good work!

James Williams

Can anyone share some figures?

Electronic Boost Control for Me?

Just wondering... Could I use the Independent Electronic Boost Controller on a diesel engine? It has a mechanical injection pump but I could get TPS and rpm data out of it. I was thinking about using rpm pulses for the boost controller, what you think? By the way, the engine I plan to fit it to is part of a project that can be found here -

Timo Tammeslehto

No, the IEBC can’t be used as you’ve described - it needs a variable duty cycle signal as the load input. Thanks for the link – it looks like you’re a busy person!

More on Sensational Silvia

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Re Silvia Story - Part One... Good to see an article on the full range of Nissan Silvias. They have to be one of the best series of cars for keen (and money conscious) car modders such as ourselves.

Just a few notes on the S12 series... The S12 came with both the CA18ET and CA18DET in its lifetime. The CA18ET was a SOHC 1.8 litre motor with a non-intercooled T2 turbo and made 90kW (quoted from one US website) or 101kW (quoted from a UK website). This engine isn't highly regarded in some circles due to its fragility, but it has a small cult following in the US (where it was available ‘till the release of the VG-powered 200SX) and Canada (where it was available for the entire S12 lifetime). When fitted with bigger turbos, intercoolers and injector upgrades (along with mapping from an A’PEXi SAFC or similar) they have been known to put out around 150 – 157kW at the flywheel and run as fast as 13.3 seconds down the quarter mile.

The later CA18DET (DOHC) is a rarer beast and, as far as I can tell, it came out in 1987 as a replacement for the venerable FJ20ET (which I believe came with a small side-mount intercooler in its last iteration in both S12 and R30 models) in Japan only. The engine, although appearing almost identical to the S13 motor, has no intercooler and the throttle faces across the rocker cover connecting to the turbo via a fluted cast tube (very similar to a RB30ET one). The motor uses Nissan's NICS management rather than the later ECCS and makes 108kW (not a great deal more than the CA18ET) but a fair amount more torque. In comparison, the later S13 CA18DET makes 131kW and 225Nm. Just out of interest, possibly the fastest S12 in the world resides in Queensland , Australia – a FJ20 turbo Gazelle hatch that has posted a 9.63 @147.24 mph. It's a Japanese market model sourced from New Zealand - a lot of life still in the old girl!

Jarich van Horck

Super Product?

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I was wondering what you thought of a product I’ve seen selling on the web... It’s an engine management upgrade that delivers better performance without any need to access the ECU – it’s a tiny electronic component that you connect to the intake air temperature sensor wiring.


Adding a resistor to alter the signal of the intake air temperature sensor is quite a common mod. See DIY Modification of Car Electronic Systems - Part 2 for details. It can be used for some minor tweaking of the mixtures - and produces nothing like the power increase claimed in some of those ads! Also be aware that we’ve seen some of these products which replace the signal from the air temp sensor (a fixed value resistor is used to replicate a temperature sensor signal). This is quite a dangerous approach because there is no longer any signal variation – as a result, engine damage may occur.

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