Interesting. But I must also stress that the test and comparison cannot alone be judged upon a journey of each. Simply because all units perform differently within the class. Some 317s taking into consideration maintenance and wear, load etc (all be it a handfull these days) absolutley fly and others act like they are towing a whale. Same applies for the 315s. You would need to do several journeys and perhaps work out an average of each. If you did this already my appologies.
To echo what O L Leigh has said, on the inner suburbans timing wise there is next to no difference. You dont get above 60 on the inners and what you loose in a 317 from pulling away up to 20-30ish you make back up to 60mph where 315s generally say thats your lot around 30-40 and then continue on a pretty shallow accel curve any higher. In the rain as A-Driver pointed out there will only be one winner (although 315s cannot be subnotched) Dwell times I cannot notice a difference. Although again too many variables. Door runner dirt, number of passengers number of doors actually opened etc can all affect how long I spend in a station.
This is in no way to discredit your test I'd in infact be intrested to know your findings if you intend to dig deeper as it is something alot of drivers who drive both units have differing opinions on.
You are right, there are a huge number of variables, including driver technique mentioned in another post. The only way to eliminate these as much as possible is to do a considerable number of runs, which is what we tried to do, and then average it out. No need to apologise, and yes we need to be sure the unit(s) are in reasonable nick. Usually the driver would comment on their performance, but no one said they were also towing a whale
. As with all exercises like this, the more data the better, but any signal check en route invalidates that particular timing, as does any unit with motors cut out. The whole exercise can be very time consuming for those with a day job as well.
At the end of the day the results were a little academic because even if we wanted to slacken out the running times a little, the turnround time at Cheshunt made if very difficult. In fact I'm slightly heartened by the comments from drivers on here that the problem may not be as big as those that asked us to investigate thought.
Reading back on previous posts I am prepared to accept I may have overstated things by saying 317s were "not at all suitable", but my money is still on a 315. Anyway it provoked a decent discussion.
Drivers who have driven both 313s and 315s together when there was a mixed WAGN fleet have often shown their love for them having that ability.