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Some of this week's Letters to AutoSpeed!

6 April 2003

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Group B Blunders?

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Great article on the Group B rally cars but there were a few errors...

1 - Lancia Delta HF only ever (officially) produced around 300hp and even in Evo 2 guise was only ever around 320hp. These figures are derived from, amongst other sources, a book simply called "Rally Car" - Reinhard Klien is the author and he's very well regarded in rallying. Also, try for more info. Similarly (and I do stand correction here) I believe the Integrale was never a Group B Car - that was the S4, and the Integrale was the result of the intro of Group A as premiere category for World Rally (after banning of Group B).

2 - Audi quattro should always be written with small 'q'. Check any Audi site or any history of the car and it is always small 'q'. Part of the reason Alfa Romeo got away with the 33 Quattro was the uppercase Q.

3 - quattro 4-valve head was released with the S1, not the A1 or A2 - the earlier ones used the cast iron block with a 2-valve head. I think you will find the DOHC head (and for that matter the alloy block) that ultimately became the sport was probably tested in an A2 car - but I seriously doubt that Audi rallied it in that form as that would have required re-homoligation. It doesn't make sense when the 'short' sport was coming anyway.

4 - Torque of the S1 was reported as being approximately 500Nm - not way short of today's WRC cars, at around 480Nm for Subaru WRC or Corolla at about 510Nm.

5 - You failed to mention that the sub 3 sec 0 - 100 was also on dirt!

P.S. Yes, I am a rally nut.

Simon Brown

Ford Fan

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I'm a self confessed Ford man and after reading your articles on the Ralliart Magna, wanted to compare it to a BA XT falcon. Any chance of a manual, 3.45 LSD equipped XT performance test? Also, I thought you may be interested in investigating Powerchip's new BA 240T chip which, on its lonesome, nets 300kW and 562Nm. Anyway, that's what it'd like to learn more about... keep up the good work.

Travis Quarrell

Well spotted - the everyday BA six now has the same power as the Ralliart Magna 'hottie' - 180kW. We'll put the word on Ford Australia and see if they have a XT with a 5-speed and LSD for us. Meanwhile, hang out for our upcoming test of the XR6 (atmo version).

We're big fans of the XR6 Turbo and, for sure, we'll catch up with Powerchip regarding their chip when we're next in Melbourne. It sounds like the engine management hurdle has been jumped!

Flyin' Familia?

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My friend has a Familia GTX and no other GTX seems to beat it. One night, though, we were doin' some laps and another GTX pulled up to us at the lights - we gave him a go and he kept up with us! We both pulled over, popped the hoods and they were exactly the same - they both different to normal GTXs in that they had no ABS and the wiring was different. The guy we raced also said that he took his car to a mechanic and found out that Mazda brought out another GTX - a RS2 - that had a few more kilowatts and was built for rally. Apparently only 42 were made. Do you no any thing about it? Thanks.

New Zealand

We haven't been able to find any references to a RS2 version of the GTX - but, given it is difficult to dig up information on limited edition Japanese market vehicles, that's not to say such a vehicle doesn't exist... We'll see if some readers can shed some light.

The only step above the GTX we know of is the Familia GT-R - a bigger turbo'd 154kW version of the BP 1.8 turbo engine.

Oh, and - as an aside - if a turbocar pulls strangely well it's often a good idea to check boost pressure. It might be sailing a little higher than expected!

Fuel Reversion?

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I was reading in 'the free part' of article 152; "Holden V6s with Leon Vincenzi", he mentions fuel reversion. I don't know what fuel reversion is and I can't find any explanation of it; could you please tell me what it is? I checked in the inlet manifold of my VS Holden Commodore Exec and there were a few black runners in there, just like Leon said, caused by fuel reversion. Thanks.

Kris Thompson

Fuel reversion is a topic that relatively few tuners fully understand. Put simply, it's an air intake resonant behaviour that causes the injected fuel to travel backwards, away from the combustion chamber. Fuel is often deposited on the inside of the intake manifold during these conditions, causing the blackness that you mentioned. Fuel reversion is often related to the intake valve(s) opening and closing at specific load, rpm and throttle positions.

Aero Separation

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After reading "Aero Testing - Part 2" I wanted to offer my thoughts. Through my degree, I have done extensive work on aerodynamic flows. Having said that, I would suggest that a test of the WRX with its STi wing removed would produce very different results. Airflows are actually pre-emptive of obstacles coming and hence the flow down the rear window separates earlier (than no-wing variant) because it sees the flow ahead of it already heading up after the car (due to the wing). The best way to show this effect would be to do repeat the test on a car with an adjustable rear wing (ie GT-R). Using numerous wool strands on the rear window, the separation point could easily be monitored for different angles of attack on the rear wing. You can expect that, as the angle of attack reduces, the separation point will move further down the window for a given speed. Just a thought. Thanks for a great read.


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