Deep Singh

Can someone please explain why different scoobies of the same spec put out different amounts of power.Also,when having your car 'chipped'one is told that power increases will differ greatly from car to car(of the same year,spec etc).I presume that the cars use the same parts put together in the same way.If the difference is in the ECU why d'ont these differences become irrelevant when reprogrammed by aftermarket 'chips' My apologies if this subject has been thrashed to death before.Cheers in advance.

Hoppy

I'm sure that if two identical cars are driven in identical conditions the performance would be, erm... identical.

Getting genuine and meaningful test data on Scoobs is very difficult because Subaru have produced so many slightly different models over the years, they have all been run differently, been modified differently and then, to top it all, any rolling road test will be different according to the dyno used, the operator, air temperature, barometric pressure and many other things. Even tyres, pressures and tracking will have an influence.

Richard

mutant_matt

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by Boost II:
<B>The first one had less body roll and brakes felt better. The second one has less understeer and the engine feels significantly free-er and returns better fuel economy.[/quote]

Handling/Steering differences are more than likely down to the fact that the factory set geometry is a bit hit and miss and dealers don't check this before selling the car.

When I was as Powerstation getting the Bump Steer Mod done, the factory settings (2K miles old) were <B>WAY</B> out. The improvements made by Powerstation were therefore amazing......(well more amazing than the changes alone would have been )

Some will be close to "factory settings" and some won't so some will feel better "out of the box" than others....

As for Power differences, most "identical" cars/bikes suffer from this as vehicles built on a production line are built to "tollerances" which has the effect mentioned above.

Matt.

Boost II

iTrader: (1)

I have owned two supposedly identical unmodified MY00's and there are definately subtle differences. The first one had less body roll and brakes felt better. The second one has less understeer and the engine feels significantly free-er and returns better fuel economy. There are even minor differences in some of the cars components.
Never had a power output measured but I percieve my current one as a bit but not much higher.

Deep Singh

OK that all makes sense but why then do ECU modders like BR Developments/Powerstation say that power gains after Link/Unichip will vary significantly from car to car(of the same spec,year etc)Minor accepted tolerances in production does'nt really wxplain this.

AlexM

Hi,

I think that the production tolerences that Subaru apply are probably much closer than they used to be in the bad old days.

Dynamic balance and dimensional tolerences are night and day compared to what they were even 10 years ago, and blueprinting consequently returns much less of an advantage in smoothness and power than it would have done then. If you are competing in motorsport, then half of one percent gain is going to be worth going after. For the road, you aren't likely to notice.

Compression will be very similar between engines (faults notwithstanding)- not enough to affect power output at all. There may be minor differences in frictional losses, but not more than one or two percent at most probably. In factory tune, you wouldn't really notice a huge difference assuming testing back to back under the same conditions.

Where these cars do seem to differ is that there seems to be a significant variation in boost pressures, probably due to peculiarities of the boost control system, pipework etc. This is probably by far the most significant factor overall - one PSI extra held boost is worth about 8-10bhp.

Some samples are better than others in their resistance to detonation and can run more advance as a consequence if you're using an aftermartket ECU. Some head castings are better than others, but again, not by very much.

A car which has the best held boost, lowest frictional losses, best inlet/exhaust port shapes etc WILL be better than a car with the worst of each, but the bulk will be pretty close to the median in terms of power.

You can see this from standard cars at Dyno days - they are usually pretty consistent to within 5-8 hp or so.

Cheers,

Alex

Alex Clydesdale

I reckon that the effect of all those minor tolerence differences mounting up are more likly to show in relativly small, highly stressed engines such as the scoobs, - Turbo ect amplifying the effect
Im sure if you took a standard run of larger/lesser stressed engines, the power/torque/response figures would be much more consistent, model to model.
I wonder if other manufactures of relativly small highly turbocharged Engines exibit these differences model to model?

Willo

These variances in manufacture are the very reason why manafacturers spend so much time and money "blueprinting" the engine, transmission, etc for Group N (in theory they should all be the same anyway??)