What'll she do, mister? - Rolling Road results

[campbell]

I think you said 160 ... or was it 150

Good ol seat of pants Dynamometer!

[Lawrence]

I actually guessed 153 but rounded down to avoid any disappointment

It is however a most enjoyable engine tune with no vices whatsoever.. highly recommended.

well done BTW and a very nice report

Did FD run his car?

[campbell]

Ta.

No FD didn't make it and we had to scarper to do some real work

[campbell]

Good stuff Campbell nice to here some of your tweaks are having great effect.

But next, it's time to upgrade the driver...and that takes a lot, lot longer

Meantime, looking forward to TT07 as I think that's the next opportunity I'll get to properly stretch the car's legs...suddenly the straights seem so much shorter

And I have started to think about KH in Sept maybe...might need to sell a kidney...

[GregR]

I'm just miffed you beat me to it

Cracking result Campbell - thanks in no small part (as you've said) to the nouce and efforts of the resident Jedi Master

Watch this space for a similar thread in the not too distant...

[campbell]

No need for miffery, it's not a race to the bhp finish line by any means

I had to make a choice of cracking on, or potentially never getting around to this, owing to imminent arrival of Ford Junior #2. So Donnie was our deadline, and in true project delivery style, we made it ... just!

You now have the benefit of the lessons we (well, FBF!) learned, when you come to apply your chosen developments.

Whatever happens, you will not be disappointed. But I do recommend before and after Dynos...just look what Robin learned about his fuelling for example!

Good luck and keep us posted.

Campbell

PS - apparently my fuel pump has a 20A fuse

[ed]

Nice one Campbell!

[robin]

I posted all the results to dyno-plot

My car:

http://www.dyno-plot.co.uk/dyno/dynoplo ... -Heads.htm

Campbell's before & after:

http://www.dyno-plot.co.uk/dyno/dynoplo ... /index.htm

Cheers,
Robin

[GregR]

[campbell]

Out of interest Robin, despite your slightly lower torque, will you get better on-road results due to CR gearing? Never quite understood that bit...

[robin]

Forget torque - it's all about power - you need to integrate (= add up) power over time to get energy - energy is used to provide acceleration by increasing kinetic energy of car and powering friction losses. It does this irrespective of gearing; gearing is just a way to make the power more accessible by always having a gear that will allow you to rev the engine harder and so be further up the power curve.

Gearing aside my car has more power at the top end, so eventually there will be a speed I can reach that you cannot, and so on an unlimited length run my car will most likely win.

In the real world, it's all about what speed you can reach over what distance (corner-to-corner).

It's not hard to calculate the effect of the gearing - pick your starting speed - say 30mph - say that's about 3,000rpm in 2nd in both cars.

Now you want to accelerate up to 100mph, changing up at the optimal point (rev limiter for both cars as power is still climbing or at least flat).

From 3K to 7K in 2nd both cars will be the same as the gearing is identical (near as matters) and what I gain in top end power I give up in power below 5750 - (i.e. the area in the section between our curves is about the same below 5750 as it is above).

Now we both shift into 3rd. My 3rd gear is lower than yours, so I am going to switch into more revs (=more power) than you and so I will start to pull ahead - effectively my engine will always have ~20-30BHP more than yours as our revs climb.

But then I will hit the rev limiter and will need to shift up to 4th, while you will have another 1000RPM or so to run in 3rd (and this will get you to 100mph I think). At that point you will be running at around 140BHP while I have dropped to around 100bhp, and I will have had the ~0.25s penalty of changing gear, so you will catch up. My guess is that 30-100mph our cars will be almost identical.

But when we then drive on to 120mph you get a different story - my car will continue in 4th to 120, but you will have run out of 3rd at 95-100mph, so you will pay the shift penalty and you will drop back to 80-90BHP while I am in the 120BHP zone.

When I can be bothered I'll knock up a simulation program (sure there are plenty already, but always fun writing another one ) and will plug in our power curves and gear ratios and see what happens ...

Cheers,
Robin

[Rich H]

There is one kocking about called cascade. Also gearbox man have one on their webside but it's a bit crude

[campbell]

LOL Robin, really enjoyed that trip into the unknown!

Yep I have seen approx 3-figs' worth of Tuts in 3rd gear for first time in UJI's history and it was pretty mental. I would be able to go considerably faster under the Bridge at KH on that basis alone.

Reason I asked the question is I seem to recall that bike engines, even though they can rev to stellar heights, are not that high on torque and yet are v v quick...even when in a car like a Se7en, hence weight penalty doesn't hit as hard as you might have thought. So I always assumed that because you had CR boxes to enable use of those revs at relatively lower roadspeeds, that was how the "low torque" got converted into "high acceleration".

Clearly claptrap, so will read your explanation again and then dig out a book about relationship between power and torque

[mckeann]

my understanding is that a gearbox is basically a torque convertor. A bike that has half the torque of a K series but can rev twice as high, will produce the same torque at the wheels due to the gearbox, and being able to hold onto lower gears for longer.

Might be wrong though

[robin]

Just forget you ever heard about torque - it's very important to engine and gearbox designers, but irrelevant to drivers of cars; all you care about is power output of engine at whatever RPM you are driving at.

Kilowatts out => Kilowatts of kinetic energy + hot molecules (friction losses in transmission, tyres, air).

Cheers,
Robin