Whose engine on the dyno?

[jimblockley]

Very interesting article about the Dyno.

But whose engine is it? Is Ray Rowan going to do Mono? Or is some young gun(from Brum) moving up from 1600 class to challenge Jeremy in the 2000 class, as is rumoured.

With that horse power he should be a race winner, anyone got any info on this mystery.

[Nick Harrison]

....................but a little lacking in the torque department?

[tristancliffe]

My advice would be to play with the trumpet lengths, and sacrifice a bit of the power for a bit more torque. Our engine was on the dyno recently, and although we couldn't match that peak power figure even with the shortest trumpets, the general shape of the curve is about the same.

I wonder if the driver of that car will be happy to or allowed to rev to nearly 8000rpm, because otherwise he'll be missing out. Plus he'll need to get the gear ratios spot on to get the most from it.

All the Toyota engines seem to lack a bit compared to the Vauxhall engines lower down, and (or perhaps because) they all seem to have a small 'hole' in the torque curve at around 4500rpm, even in road going form, so I presume it must be a dynamic trait to do with combustion chamber shapes or valve port geometry.

[jimblockley]

Yeah

But who is the driver? which is more important than your torque and bhp,s

[Nick Harrison]

Plus he'll need to get the gear ratios spot on to get the most from it.

Would be interesting to do a comparison at the wheels. One of the advantages of the torque of the VX, paticularly on 45s and 36mm chokes is that you can run as a four speed and indeed at Brands a three speed. This means you can replace rotating mass with spacers and claw back more BHP than is lost.

[tristancliffe]

I believe the car was originally being built for Tony Cotton. An F301 in a fetching shade of British Racing Green. I don't know if Tony is still the designated driver, or if Ray is driving it, or if they're sharing it, or if it's now someone elses project altogether.

Edit: Jim - I agree with your sentiment about the driver being important (I lie awake at night wishing I was as good as most in Mono), but there is no point giving the driver lots of power at a rev range he can't use for fear of it blowing up. No point giving yourself a power disadvantage for the sake of a set of trumpets.

It would be interesting Nick. All I know is that a peakier engine either needs more gears or more perfectly spaced gears (or both!). A torquier engine can cope with less gears or poorer spacing. I felt, from day one, that our engine was more powerful than the one in Neils car, but lost out for the first half of the straights. It was pretty much status quo by the next braking zone.

Only been to Brands once, so don't really know what to do about gearing yet. I don't think our engine is torquey enough to cope with running as a three speed, so if Neil is racing the yellow machine there we might be able to draw some conclusions

[tristancliffe]

Just had another look at the Startline graph, so that I can feed it into the various bits of analysis software I've been creating and using over the last few years (read: several Excel spreadsheets with lots of equations in them). That's meant I've looked at the Startline graph a bit more closely.

1. Actually, we have a very similar peak power figure, albeit ours is several hundred RPM lower down. This in turn means that at every point between 3500 and ~7000rpm we have, given the same gear ratio choices, we have more tractive effort at the wheels (our 'graph' is shifted to the left). This is why I suggested they played with the trumpet lengths.

2. The Startline graph is a bit odd - some of the values of power don't coincide with the values for torque that they should, albeit not by much. And what's going on with the last point? Only a 250rpm increase (7250) over the previous point (7000), yet the graph spacing is the same horizontally... Perhaps the data has been doctored so as to keep the actual results a bit secret, or perhaps the graph plotterer got a bit confused?

3. Although it depends on the exact gear ratio choices, this engine would need gear changes between 7300 and 7400rpm. I wonder if the dyno session took data at higher revs than 7250, or will 7400rpm be venturing into unknown (or even worse, unmapped) territory?

4. Changing to fuel injection wouldn't, it seems, change the peak power figure all that much (although we are not all that close to the 40mm butterfly limit imposed by the regulations, so perhaps more outright power could be achieved), but adds more 'midrange' oomph.

5. Overlaying the Startline data with our own data for carbs and injection (with the injection data also at a range of trumpet lengths), all on the same engine/exhaust etc shows a very very similar shape of curve, with holes and dips in all the same places. This, surely, points to the geometry of the standard engine, rather than choices in exhaust, inlet manifold or dry sumping arrangement, as being the defining aspect for the shape of the curve.

It's unlikely that Vauxhall engined cars would be willing to share their actual torque/power data with us, so that the two makes of engine could be compared. But if anyone does have a graph of their Mono-spec Vauxhall XE 2000 engine they would be willing to share then I would be very interested.

[tristancliffe]

Due to the wonders of the internet, I now have some Vauxhall XE Mono-Spec dyno information, from an unnamed source.

It seems to show what I felt (and what previous Toyota engined people, like Phil Moore, had stated). Comparing the Startline figures shows the Toyota being a few horses stronger above 6000, about the same between 4750 - 6000, and a few horses down below 4750rpm. The Toyota has a higher peak power, but the distribution of that torque and power is just as important.

....................but a little lacking in the torque department?

Yes, in comparison to this XE data I've been sent.

If there was a rev limit in Mono of something like 6500rpm, then the XE engine would be stronger overall, possibly by quite a margin (although both could be improved to suit that with changes to exhausts and inlet tract lengths etc). If a certain amount of tuning was allowed that could raise the rev limits (lightening the reciprocating stuff for instance), then the Toyota would probably be the stronger engine. As it is, with road car internals and hence similar-to-road-car-revlimits, the two engines are pretty much the same at the majority of tracks. If there were a lot of slow corners then perhaps the XEs would be favoured, whilst at somewhere like Thruxton maybe the Toyota is the better engine.

Of course, all of this is diluted by drivers of different abilities, tyres in different conditions, setup preferences, circuit preferences.... as Jim said to begin with.

But still, I think it's interesting comparing these things, even if they are ultimately not very useful out on the track.


P.S. The 'smoothed' polynomial curves on the Startline graph are useless. With discrete data like engine output figures it is 100% useless to use that sort of smoothing. If it was a trend of CO2 in the atmosphere, or number of Monoposto competitors over the drivers, or the number of cakes eaten by Mono1600 drivers over a race weekend, then you can use a smooth curve to 'spot a trend'. Which is why I'm taking the graph results with a pinch of salt.

Edit: Would help if I clicked on the right things! The first version of this post was comparing messed up data (i.e. a list of RPM values for one engine, the power/torque from another, and trying to graph them together. It was meaningless. Sorry. Now corrected and checked, and accurate (ish).

[jimblockley]

post removed

[andrewcliffe]

On the Christmas Quiz thread...
viewtopic.php?f=2&t=534

[jimblockley]

Thanks Andrew put it down to a senior moment