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Old 20 Mar 2013, 17:28 (Ref:3221814)   #1
andy97
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andy97 should be qualifying in the top 10 on the gridandy97 should be qualifying in the top 10 on the grid
Turbo equivalence

Can anyone tell me definitively please when the equivalence factor for turbos changed from being 1.4 to being 1.7? ie what year?

Was there any specific reason or example car that was responsible for this? Any reference material?

Thanks
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Old 20 Mar 2013, 19:19 (Ref:3221861)   #2
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Assume you mean in club racing. In F1 it was 2:1 from late 70s.
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Old 21 Mar 2013, 06:27 (Ref:3222105)   #3
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Andy, although it doesn't answer your exact question this article is an interesting read (if you haven't seen it already)- although reference to the 917/30 having a V12 engine suggests the writer wasn't around at the time.........
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Old 21 Mar 2013, 08:24 (Ref:3222138)   #4
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Whatever it is or was its not enough which is why the BTCC is where it is today sadly.
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Old 21 Mar 2013, 10:31 (Ref:3222219)   #5
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Thanks all, we've not found the answer yet, though. My recollection (which may be faulty!) is that companies like Renault specifically produced turbo engines of 1.4 litres capacity so that cars like the R5 Turbo (and later the mid engined "R5" Turbo) would be in the up to 2 litre class of world rallying and the like. Porsche even built a one off 1.4 litre turbo version of it famous 935 to take on the opposition away in the up to 2 litre class of Group 5 (at that time dominated by F2 engined cars).

At some point (not sure when) the FIA decided that the x1.4 equivalence factor was not enough and upped it to 1.7 meaning that these types of cars were now less competitive in the usual 2 litre to 3 litre classes.

The reason I'm interested is because turbo engined cars of the 1970s and early 80s are fairly crude beasts and can't give the massive power that todays turbo cars can reliably or without electronic control. If these cars are ever going to be used in historic motorsport, as they will eventually, if they are not already, then I just wonder what the cut off year may be and whether a x1.4 (as was originally applied) or a x1.7 (as applied now) equivalency factor should apply.

As an example, take a Porsche 924 Turbo - it was produced in 1979 and was a fairly crude turbo installation delivering 177 Bhp in non intercooled road form and the 924 Rally version was only 180 Bhp. However, compare this with a Sierra Cosworth which was introduced in 1986 & which had 204 Bhp as standard and much more in routine motorsport trim. Nominally they are both 2 litre turbos and could therefore be in the same class unless, say, a x1.4 equivalence was applied to the924 and a x1.7 equivalence factor to cars turbo that were post 1981 (or whatever the date was that the FIA changed its rules).

Note that things like Sierra Cosworths are now being used in "classic" rallies on the Continent

Is it fair that different rules may apply now than applied then? Discuss!
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Old 21 Mar 2013, 15:24 (Ref:3222335)   #6
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terence should be qualifying in the top 10 on the gridterence should be qualifying in the top 10 on the grid
Stop off in a scrutineering bay before a big "FIA" event and then decide on whats "fair".
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Old 22 Mar 2013, 05:39 (Ref:3222568)   #7
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The FIA used 1.4 for Group A Touring Cars from 1982 to 1987 and switched to 1.7 for 1988 onwards.
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