Launch technique?

Well, mine would be considerably less with a person on board...

Lazy git!

Ok, as I'm nice (not to mention blistered, having done the whole tube network yesterday), I'll do it for you:

Buggy is 714.3 bhp/tonne.

Truck is 583bhp/tonne.

I can see how this whole radio control car thing could be fun. I was vaguely into the plane thing when I was younger, but only got as far as a cheapo polystyrene powered glider that you did a quick charge on an instant charger, which lasted about 30 seconds, and building a balsa-framed rubber-powered Hyper Cub. Then I lost interest and started playing lots of music instead.

What I always did fancy was to get into radio controlled choppers, but back then 4-channel radios were way too unaffordable. In fact, given my current financial situation, they probably still are at the momentito :-(

You learn something every day. I'd assumed that, at high-RPM idle, there'd be enough exhaust flow for the turbo to generate full boost. It wouldn't need to turn particularly fast since the boost isn't going anywhere. Once the throttle is opened, the boost would almost instantly disappear into the engine, the wastegate would shut and the turbo would spin up for real. It all seemed so plausible...

Is the wastegate actuator normally plumbed in before or after the throttle?

Cheers,

Colin.

Opens a bit before full boost. It's linear from some pressure that starts to make the actuator move to whatever pressure opens it fully. It depends on diaphragm size, preload of spring and spring rate.

Turbo works on gas flow. Power = gas mass flow rate * heat input from fuel so it only spools when motor is making power. Little T2 needs gas flow that will make about 40bhp, T25 45bhp, T3 55bhp, T4 70bhp to start to spool. Even redline at no load is naff all power and thus naff all gas flow. That's why Burgerman says load it on the brakes and clutch, power absorbed by clutch means gas flow is high enough to spool turbo but at cost of clutch. Once spooled the power rises quickly as turbo increases gas flow, which drives turbo faster, which makes more gas flow...getting the balance between no turbo spool and runaway boost that causes clutch burnout is a skill.

Before but after gains a few psi at the expense of boost spikes which could damage the turbo

Presumably these figures are for turbos producing boost with the throttle wide open and the engine sucking for all it's worth. How much gas flow do they require to make full boost pressure against a nearly closed throttle? Incidentally, this boost won't show up on a boost gauge since that will be after the throttle.

Of course, all this is academic. Even if there is enough boost to open the wastegate, the turbo would still be spinning fairly slowly and the pressure will drop as soon as the throttle is opened.

Actually, it was me that first came up with that particular hair-brained scheme.

That's what I'd always assumed. So maybe there's hope for my theory yet and there could possibly be pressure in the pipework high enough to open the wastegate whilst idling at very high revs.

Cheers,

Colin.

About the same as a moped.

Wastegate opens at x pressure sensed from the plenum chamber normally, so it opens at say one bar of boost to stop overboosting. When anything less than full throttle at x rpm, there isnt enough exhaust to do anything to the turbo.

I wasnt the one that said that but its true. Or fit nitrous! Instant gasflow, instant power boost comes along extremely fast!

Once spooled the power rises

Before? Not on any of my turbo bikes, etc. Always at the widest slowest gas flow part of the plenum (low gas flow = highest pressure)

Only if you fitted a tiny turbo like a diesel uses, but then as gas flow increases it is actually in the way and the turbo itself becomes the restriction.

No you need a huge low compression engine, with a HUGE turbo and enough nitrous to make it boost!

To get an idea why my V8 needed a stronger clutch consider that the clutch has to not slip at a given torque level. Here is a torque curve from my own stock quiet bike (136bhp) with a 50bhp nitrous system added. Notice I didnt hit the nitrous button until 7400 rpm, for very good reason! Look at the torque (acceleration - seat of pants same thing!) curve increase oner the stock curve. Remember that this is only a 30 percent boost on a stock engine! Imagine how this increase feels on the road on a bike that already does 100 inside 6 secs. In second... Imagine how the clutch felt! Worse, imagine in your head looking at the graph how much torque it would produce at say 4000 revs if I was daft enough to try it!

My previous bike had 2x 50bhp stages, and a huge T4 turbo at 30psi...

Power curve from the same bike should you be interested.

Extremely? Heh. Not really, unless I can ride in or on Dan's RC car.

Just looked up my car - it's before the throttle. I dimly recall my old S13 200SX was the same.

Cheers,

Colin.

Yep my GFs car is too. Thinking about it it would have to be on a road car really. They need to be a bit sensible!

Real fun was when i dropped the .28 3.5bhp truck engine into the buggy. Which is 3.5kg, 1 speed, 4wd with front, centre and rear diffs (all set up with different thickness oils). Whats THAT power to weight then ;) ?

On street tyres on tarmac, it would 4 wheel drift, properly, and killed the tyres in about half a gallon of fuel :)

And 6 hours to waste whilst you sit there twiddling your thumbs waiting for the turbo to spin up.

No as usual wrong again.

It spins up fast, very fast, because the Nitrous initially makes a load of power at any rpm and loads of exhaust gas to go with it.

Nitrous gives almost instant boost, and no noticible lag even with a huge turbo - REGARDLESS of revs..

Impressive, although not necessarily part of the question. If you can get big increases in power then the clutch will become inadequate, but that's at the end rather than a worthwhile early modification.

Er... how come it has three peaks? Two I understand is usually a resonance chamber / dual inlet thing, but three?