Some of this week's Letters to AutoSpeed!

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Boost Controllers v Boost Controllers

Could you tell me the differences between a "gated" boost controller (Turbosmart) and the GFB Atomic Boost controller? Which is better for low rpm boost and reduced lag? Do electronic controllers basically work the same way as the bleed valves?

David Tenace

According to their website, the GFB boost controller doesn't appear to be gated like the Turbosmart item. An un-gated controller is unlikely to build boost as quickly as a gated variant.

An electronic controlled system works on the same concept (ie it bleeds air from the wastegate line) but electronic control allows more precise control over boost pressure..

Check out e-Boost Evaluation , Low Buck Boost , Project EXA - Part 3 - DIY Boost Control. , The Audi's DIY Boost Control - Part 1 and Bumped Up Boost for related information.

Gave Up Too Soon?

Fantastic article on the Peltier Intercooler Water Spray but I think you gave up TOO SOON.  I wonder if the answer was lying right under your nose - the hint appeared in the article itself. As you say, the heat transfer to air through the external heatsink is insufficient. Why not transfer heat to a second, larger  water store?! There will still be a small efficiency loss but a larger water volume and larger heatsink should balance this out. This could be a static store of larger volume in a metal container to maximise heat transfer out. By using a larger volume of water, the temperature rise in this store for a given measure of heat transfer will be minimised. The trick, I imagine, will be balancing the benefits vs the weight and volume of the system.

One question before going any further with development: Is there a benefit gained in intercooler function with cooler water spray temperatures?

Michael Linton

Interesting idea, but it raises the problem of then needing to cool the water. This adds even more weight, complexity and cost. Re the benefit of using a cooled intercooler water spray, we know the theory, but - since we were unable to go ahead with our own on-car testing - we can't give you a definite answer.

Epic Error

Re your Aussie Engine Epic 2004 Engine Epic - Aussie Engines - quite an informative article overall, except for a glaring error regarding the 5.4-litre 4V engine, as used in XR8 and GT. I'll quote:

”The first bent-eight engine we must tell you about is the all-alloy, DOHC, 4-valve per cylinder, 5.4-litre XR beast. In its ultimate 290kW guise (fitted to the BA GT and GT-P), the Boss 290 engine uses a balanced forged steel crank, revised rods and domed pistons to achieve a 10.5:1 compression ratio. Each of the VCT quad- camshafts has a pretty aggressive profile and the intake arrangement is a beauty - tuned-length trumpets, a large cast alloy plenum, 75mm throttle body and a low restriction airbox. It's no wonder 290kW and 510Nm are on tap!”

The quad-cam 5.4 V8s are NOT VCT. They are the only engines in our current range not featuring VCT. I hope this clarifies any misunderstanding! Thanks, as usual, for the interesting cross-section of articles!

Tyrone Smith

You're absolutely right. Article now corrected.

Damn Drone

I drive a '96 Nissan S14 200SX with 12 psi boost, K&N pod filter and a 3-inch mandrel exhaust. My problem is that I can't find the right compromise between noise and power. The exhaust system runs from the turbo, through two small mufflers and then to a quite large offset muffler at the rear. The diameter of the exhaust remains constant throughout the system. I have tried replacing the rear muffler with a reverse flow unit - but it just kills the power. I did quite a bit of reading on your site and found that maybe I should add a fourth muffler to the system (due to the fact that I do not run a cat converter, as it is not required here).

Should I try adding the original cat converter into the system? All I want to achieve is remove the drone form the car. I've been to most of the good exhaust shops in the area and they have no experience on my vehicle. Any help or suggestions would be greatly appreciated. Your site is the best auto resource I can find to date - thanks for the great mag.

Gordon Pieterse
South Africa

Try fitting a high-flow cat and/or larger-bodied mufflers - these will take out more noise and drone. Also, note that long, straight lengths of pipe tend to cause drones and resonances.

Rich Rex

My '94 Subaru WRX is running very rich fuel mixtures - 11.2:1 at idle and 10.2:1 at full power. I'd like to plumb a bleed valve into the fuel pressure line as seen at Mixture Modifier Two questions... Which line coming out of the WRX manifold should I use? Can a TurboSmart bleed valve be used since I want to lean it out all through the rev range?

Scott Akins-Sellar
New Zealand

Assuming your WRX runs the standard management system, air-fuel ratios should be arund 14.7:1 at idle - this is a function of its closed-loop fuelling. Based on what we've seen on WRXs (including our own) it's normal to see high load mixtures in the 10s with an engine that’s slightly modified.

We’d strongly suggest using the dedicated Mixture Modifier – not a boost controller - to lean out the mixtures when the engine is running in open-loop (at high load). The Mixture Modifier features an adjustable set point and is designed exclusively for that purpose.

If you’re unsure about which hose to insert the Mixture Modifier we suggest buying a factory workshop manual - or take the car to somebody with WRX experience.

Note that we'll be covering a new electronic interceptor soon. This will allow you to adjust mixtures - and ignition timing - by altering the output of the airflow meter.  The unit has been designed by Silicon Chip magazine - stay tuned for our coverage!

SR20 Turbo Down but Not Out!

Contrary to your comments in the recent "Nissan SR-Series Engines" article The Nissan SR-Series Engines the SR-series engine is actually still in production. The Japanese Domestic Market Nissan X-Trail uses a NEO VVL version of SR20VET developing 206kW and 309Nm - and it meets current Japanese emission standards.

Kevin Kwan

You're right. Thank you very much for revealing that!

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