Supersport Power

[Shalders]

Has anyone rolling roaded a standard 1.6 supersport Caterham? Just interested in what the power was compared with Caterham's claims....(I've seen figures of 133bhp and 138bhp, is this exhaust differences??)

[CB]

The answer I got from Caterham was the power increases to 133bhp @ 7000rpm, peak torque going from 107bhp @ 3000rpm to 110lbft @ 7000rpm.

 

p12 of July's Lowflying has a plot taken from a 1.6 Supersport which isn't too far from this...

[jamesm]

worried about that dodgy engine of yours shalders!! too fast for the competition?

[cbglos]

I have a near standard supersport 1.6K and recently put in on John Wilcox's rolling road and saw 129bhp.

 

Don't forget that rolling road figures are not the same as dyno figures (taken at the flywheel) and are not absolute. They will vary with the rolling road used, tyres, gearing, ambient temperatures......... you name it. There isn't even a 'rule of thumb' figure for power loss between the flywheel and the rear wheels or so I am told.

 

The difference between Caterham's 133 and 138 figures is likely due to the non cat race exhaust the Raodsport 'A's run.

 

Chris

[drB]

according to Chris Rees' book, Caterham revised the figure from 138 to 133 "..to reflect it's genuine output with catalytic converter in place."

 

Action! in Orpington, Bromley Pageant and Keevil

[Super_Rich_Bernie]

I have a dyno curve for my standard 1.6K supersport prior to upgrade by Minister. These were taken on their engine dyno rather than a rolling road.

 

It made 129bhp, running a 4 into 1 exhaust.

 

Jonathan

[Peter Carmichael]

The answer I got from Caterham was the power increases to 133bhp @ 7000rpm, peak torque going from 107bhp @ 3000rpm to 110lbft @ 7000rpm.

 

I know the rpm figure for the peak torque is wrong.

[oilyhands]

Indeed, 110ft/lb @ 7000 is 146.6BHP.. Shurely shome Mishtake.

 

Oily

[CB]

No doubt - not least because when I first asked CC they said they didn't have any torque figures for a 1.6 SuperSport...

 

See the plot in Low Flying was rather more reassuring though (peak torque nearer 5000rpm, at 7000 it seems to have dropped off to just above 100).

[Richard_E]

. In the mean time I went to Emerald to pick up an ECU and have a power run. Peak BHP was 134 at 6750rpm. Peak torque was 114 ft/lb at 5250rpm.

[Peter Carmichael]

Point 1...

 

For all the praise I heap on Emerald's rolling road, accuracy in producing torque figures/rpm figures is not their strong suit.

 

Accurate torque figures require accurate rpm readings. That is the single most difficult thing to achieve on a rolling road compared to an engine dyno. The power figures can be spot on (apart from the rpm at which they are produced), yet the torque figures can be out by a factor.

 

If the rpm @ 60mph figure taken by Dave W is inaccurate by 4%, the result can be the difference between peak power showing up at 6750 "revs" or 7000.

 

The torque would also be scaled up by ~4%. So in your case figures of 114lbft @5250 would translate into ~109.5lbft @ 5460 and the power figure neatly slot in at 134bhp @7000rpm - much closer to book figures (in fact, astonishingly close).

 

I don't necessarily believe either set of figures to be accurate. I have previously achieved some corroboration for this through datalogging on the road.

 

The datalogging guarantees an accurate rpm reading, but introduces other errors: humidity and temperature are not corrected; headwinds/tailwinds; inclines; aerodynamic and rolling drag. The main purpose of having your engine produce power is to achieve acceleration on the road and with datalogging it is possible to measure exactly this.

 

The experiments I have performed with a Supersport have been to drive through each gear at full throttle. on a flat, open, straight stretch of road. Start with 3rd gear. Accelerate until the limiter kicks in. Back off to a speed clearly below the peak power speed. Slot 4th. Accelerate again, through to the limiter. Repeat for 5th and 6th if you don't value your licence.

 

With the datalogged results, overlay the runs for each gear. The acceleration in 3rd gear is greater than the accleration in 4th - a steeper line on the speed trace - but it falls away quicker as we run out of revs. What we need to do is find the point at which the speed and acceleration are the same in the two gears. You align the overlay so that the speed curve for 3rd gear just touches the speed curve for 4th gear at a single poiny. This gives a point just beyond the power peak. Experimentally, with a Supersport, a six speed box and on the 3rd to 4th gearchange this happens at about 7400rpm. For 4th to 5th it is a bit lower. For 5th to 6th it is lower still at ~7200. In the shorter gears it is a bit higher. All this is in line with the theory, shows that the standard change up lights are about right (7400) and the rev limit at 7600 is also about right for optimum performance. The gearing on the six speed box (as with most boxes) gets tighter in the higher ratios, explaining the reduction in optimum change up revs as you go up the box.

 

This doesn't tell you the exact revs at which peak power is achieved, but it does suggest that peak power is just a little below 7200 rpm. 7000rpm sounds realistic and at least now you know when to change gear.

 

Can't remember point 2...

 

Edited by - Peter Carmichael on 14 Jul 2004 15:08:36

[Shalders]

Just to complete this thread, my car made 109bhp at the wheels at 7000rpm (as did another 7 of the same spec on the same day), a third made 120bhp also at 7000rpm (again same 1.6 supersport spec). This was done at Aldon Automotive nr. Birmingham (and was quite cheap, £40+ dreaded a go...). SO they're good'uns and bad'uns.........

 

(Agree with Peter's views on the change lights....)

 

(The guesstimates to flywheel power were 145 and 155bhp for 109 and 120 at the wheels respectively).