Turbo Equivelancy

[andy97]

Can anyone remember when turbo equivelancy was changed from x1.4 to x1.7 please?

What effect does/ will this have on historic racing. ie cars that raced in era with a 1.4 equivelancy many have raced in a 2 litre to 3 litre class but if the more recent 1.7 equivelancy is applied they would now have to race against over 3 litre cars that traditionally were not there class rivals. has thisbeen anissue anywhere?

[chunterer]

That's actually a pretty good question andy.

In 1983-1985 the BTCC class system was:
Class A 2501-3600 cc (In everywhere else under Grp A; Class A was for cars above 2501 cc....)
Class B 1601-2500 cc
Class C upto 1600 cc

Frpm 1986-1989 the class system was:
Class A: above 2500 cc
Class B: 2001-2500 cc
Class C: 1601-2000 cc
Class D: upto 1600 cc

1990 onwards was just over 3000 and upto 3000 classes.

From 1988 the RS500 cubic capacity was rated at 3389cc (the cars standard capacity of 1994 x1.7) in race programme entry lists for the BTCC, and I think it was the same in the ETC.

I have a feeling that this was changed for 1989 or 90 because when that car was homologated in 1986 under x1.4 factor equivalency it's 'race' cc was rated as 2792cc.

Another point is that in 1984, the Colt Starion 2.0 Turbo had an equivalency cc of approx 2800 which slotted it into Class A (above 2501cc) and the Bluebird 1.8 Turbo and Metro 1.3 Turbo both into Class B (1601-2500cc) so they can only had an equivalency of x 1.4 to fit into that class. In fact I think the Bluebird would've been very close to slotting into the over 2500 cc class at the time but there was some interesting standard CC rating being issued fot it?

[racer69]

As far as FISA regulations were concerned, the Group A turbo equivalency factor was changed for 1988, from 1.4 to 1.7

There were also other regulation changes, which took rubber off the smaller cars (affecting the likes of the BMW), and i think it also added weight to the bigger capacity cars, stuffing the Holden's even more (or it could have been taking tyre width away also, have to look it up)

[chunterer]

That's it r69, I couldn't quite nail the year.

But, with those added measures taken, you have to wonder why those changes took place when it so obviously was going to favour the RS500, and quite probably the M3 even further over any class rivals, as these 2 cars were already streets ahead before the changes

[KA]

Originally Posted by racer69

As far as FISA regulations were concerned, the Group A turbo equivalency factor was changed for 1988, from 1.4 to 1.7

There were also other regulation changes, which took rubber off the smaller cars (affecting the likes of the BMW), and i think it also added weight to the bigger capacity cars, stuffing the Holden's even more (or it could have been taking tyre width away also, have to look it up)

As I remember, another car stuffed up by the reg changes was the Alfa 75 Turbo - it might have been affected by other parts of the regulation changes as well, but I think the new turbo equivalency factor just put it into the over 3000cc class with the RS500s....?

[Jesper OH]

Originally Posted by KA

As I remember, another car stuffed up by the reg changes was the Alfa 75 Turbo - it might have been affected by other parts of the regulation changes as well, but I think the new turbo equivalency factor just put it into the over 3000cc class with the RS500s....?

The Alfa 75 Turbo is a special case regarding engine displacement. The normal production model had a 1779 cc engine while the Evoluzione had a slightly smaller 1762 cc engine.
With the 1987 turbo coefficient of 1.4 both engine sizes fits nicely into the 2.5 catagory/960 kg/10" rims in direct competition with the BMW M3. With the new 1.7 coefficient for 1988 the Evo has a 2995 cc compared to the normal versions 3024 cc. With new minimum weights for '88 as well the Evo would weigh in at 1020 kgs compared to 1100 kgs for the normal version.

The Volvo 240 Turbo was a car that was penalised heavily with the new coefficient. At 2127 cc it slotted in just under 3 litre/1035 kgs under the 1.4 rule, but at 3616 cc/1180 kgs with the 1.7 rule. It mattered little as the car was ancient by then anyway.
In the Nordic countries cars homologated before 1st January 1987 (before the Ford Sierra RS Cosworth and BMW M3) was allowed to run to the old regulations after 1st January 1988, keeping especially the best Volvos in the hunt.

Cars like the MG Metro Turbo and Toyota Starlet Turbo (both 1.3 litre) would end up in direct competition with the BMW M3 E30 under the 1.7 coefficient were previous they had a 2 litre class at least in the BTCC.

Jesper