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Some of this week's Letters to AutoSpeed!

10 August 2003

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Meaner Manifold

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I've got at atmo six Holden Commodore VL that I'm rebuilding and I can't for the life of me find an upgrade intake manifold for it. I've been told that the factory one is very restrictive - this is why I'm searching. I know of one aftermarket one, but they want big bucks. Can you help me? I've got everything else except the intake manifold and I really don't want to put the original one back on. Your help will be really appreciated.

Nick Moffatt


Depending what sort of power you're shooting for, the factory VL intake manifold might not be THAT restrictive. We'd first suggest testing with the factory manifold fitted - at full power, manifold vacuum should be a close as possible to atmospheric (1 Bar absolute).

Note that the RB30ET intake manifold has shorter runners than the atmo engine and it might make a worthwhile cost-effective bolt-on change. You might also want to look into swapping the throttle body (if it is measured as restrictive), porting or Extrude Honing your existing manifold. Any aftermarket replacement manifold will likely be expensive.

Kei Power!

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I loved the article on Kei Cars ("Kei Fun"). I have been a fan for a very long time and have always lamented the lack of Kei presence in Australia. If only one of the big Japanese Kei guys (Suzuki especially) had the guts to release some in limited numbers in turbo form I'm sure there are other wackos out there under 5'8" (like me) that would jump in one in an instant.

Cameron Bell


Glad you liked it. And Kei CAN be enjoyed by taller people - how 'bout the topsy Daihatsu Move turbo, for example?!

Super Swede!

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Thanks for an excellent online car mag - keep up the great work! I really like the mentioning of the SAAB 900 Aero in your recent article "Sub-10k Supercars - Part One".

The SAAB 900 Aero/SPG is really a hidden performer that many people do not really know much about. It's fun to see it 'pop up' here and there.

Richard Lageren
( webmaster)

Flat Line Boost

My mates have two-stage aftermarket boost controllers (of the bleed variety) in their Nissan 180s, however I am lucky enough to have a Blitz electronic boost controller. In reference to your recent article on ironing out boost spikes ("Shooting the Overboost"), I wonder whether this could be applied to their boost control systems to control existing boost spike problems. My electronic boost control shows a maximum spike of 10% in 1st gear and remains constant in 2nd and 3rd, however up to 40% fluctuations have been recorded in their cars. Can we apply this in-line valve to their application and solve this problem?

PS - I loved that R33 Skyline ("FLYNLO")! Can't believe he was only making 450hp at the treads, though - with that much boost and such a big displacement the figure should have been closer to 600!

Andrew Seward

The same airflow and pressure principles are involved regardless if the needle valve is bypassing an aftermarket bleed valve or a pulsed boost control solenoid - we can't see any reason why it won't work given careful adjustment of the needle valve.

Re Skyline - the Rigolis were pretty casual about its power output, so it's likely they're not leaning on the engine too hard in terms of timing or AFRs. They'd already gone past the owner's power target after all!

Waiting, Waiting...

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Excellent Feature Car articles but I keep looking for a modified Magna/Verada story. Regards.

John Nesbitt

We'd love to cover a well modified Magna/Verada - any takers?!

Wants to be Part of the Revolution

I have read your article about Kevin Davis' exhaust revolution ("Pure Pipe Perfection 2 - Introducing the Secret Weapon..."). Besides the telephone number you have advertised, please be so kind to give me Kevin's email details if you have them. Kind regards.

Erez Rothem

Kevin Davis can be emailed at

Maybe I Can Help...

Regarding David Wilson's enquiry about VAG (Volkswagen Audi Group) 1.8-litre 20-valve turbo engine modifications, I have recently been involved in several modifications to an Audi A3 fitted with the naturally aspirated engine and an A4 2WD fitted with the turbo motor.

In the case of the NA engine, the large factory rear muffler and pre-airbox intake snorkel were found to be the biggest restrictions to power. Replacement with a 2.5-inch straight-through muffler and free-flowing cold air duct to the airbox provided an increase in power and throttle response, particularly after 4000 rpm when the 20V motor begins to really wind up.

For the turbo motor, the factory bypass (blow-off) valve was found to leak under boost and replacement with an aftermarket "plumb-back" style valve improved boost response. Then, after fitment of a boost gauge, the factory boost level was found to peak at 5 psi trailing off to about 3.5 psi as the cams started to come on. The plumbing was removed from the factory boost control solenoid (leaving it plugged into the loom or else the computer will give a fault code) and an aftermarket bleed type boost controller was fitted. The bleed valve was tuned to peak at 10 psi and only trailed off to 9.5 psi as the car reached redline. The factory boost cut did not step in at this level on the A4, but this may be different on other models or in other regions. The performance improvement with just the boost raised has been excellent - the car now comes on boost sooner, pulls stronger through to redline and scrabbles for traction off the line.

Note that at elevated boost pressure, though, Audi has tuned it quite rich - this has resulted in slightly elevated fuel consumption and the expectation of better performance once the mixture has been leaned out. More power and quicker boost response are also expected once intake and exhaust restriction is lowered. In all, this motor in turbo form represents an excellent base for further modification.

Cary Wintle

Detonation Detector Version II

Unfortunately, the Whisper 2000 personal amplifier recommended in your DIY Detonation Detection article - "DIY Detonation Detection - Part 1" - is no longer available. Do you have an alternate product that will fit the build in that article?

Paul Elliott

Have a look at "DIY Detonation Detector - Mk II" - this version uses a new amp.

AFR Meters For All!

After reading article 217 ("Cheaply Monitoring Air/Fuel Ratios") a few times, I was wondering whether it would be possible to use the Jaycar kit with a carby car; fit a EGO probe/oxygen sensor to the carby car's exhaust manifold and hook it up to the sensor?

Alan Mears

Sure it can be done - we did it on a 1984 Daihatsu Charade turbo we used to own!

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In the Charade's case, there was a post-turbine cast iron elbow available from the Japanese-spec turbo engine that bolted on and it already had an oxygen sensor fitting incorporated (actually, the fitting appeared to be for part of an Japanese-spec emission system, but it had exactly the same 2-bolt mounting pattern as a Daihatsu Mira oxy sensor!).

In most cases, though, you'll probably need to have your exhaust manifold (or dump pipe, if the engine is turbocharged) modified to accept a fitting for the sensor.

Note that the Daihatsu sensor was a single wire version, so it was dead easy to hook up - it was soldered straight to the 'signal' input of the mixture meter and that was it! It worked great (while running premium unleaded fuel, of course).

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