Sicdatto1200- what type of carb and AFR meter are you using?

I in my ute (drawthrough, sc14 blower, d/d weber) I sometimes get pinging on transition from cruise to full throttle. the AFR meter clearly shows this to be a lean out problem-as the throttle plate opens the pump jets don't squirt enough extra fuel in.

people tend to report better results out of SU's than standard type carbies as they deal with velocity changes better.

WATER INJECTION-
somthing I am looking into so that I don't have to decomp.

Running a boost activated injection system on a drawthrough setup (with the water injection before the compressor) is conceptually flawed:

The manifold has achieved boost, the switch is triggered, water starts flowing into the carb/inlet manifold, through the compressor and finally reaches the inlet manifold....... how long after the initial signal? possibly only fractions of a second, but definatley a revolution or two after it was required.

to offset this I suppose you could set the switch a psi below where you need it.

Also, the guy at my local dyno shop assures me that running water through a turbo or supercharger will make atomisation worse, not better.

Sunnydaze,
you dont have to worry about total advance. The springs dont control this , they control the rate of advance. (Which is still important) There are stops in the dizzy to control the amount of advance. the vac advance wont be working under boost. Some of the 2lts escorts had dual diaphram dizzys. maybe use a Vac canister off one of these and get boost retard. its worth 10 degrees on the escort.

What about the vacuum advance mechanism? I have "heard" that the spring in the dizzy gets tired and can cause the mechanism to advance the timing too much.

Can anyone substantiate this vicious rumour?

Water injection seems to be coming up a bit..
The aquamist system was used widely by the WRC teams in the last few years until being baned this year!
A very good system but at about $1200.00, NOT cheap..
They will sell just the nozzles which are better than the finest of the agricultural (flojet) ones. They produce a very fine mist and are about $40 / jet.
The flojet type of pumps can be used. Use the 100 psi unit if the water is to be injected after the turbo. and should be just after the intercooler alowing the mist to fully vapourize before the maifold.
I`ll be using somthing along those lines when i get my engine finished. If anyone else sets up a system id love to here how they get on., Simon

(EDIT) sorry sikdatto, i looked at your links after posting, a link to aqua mist from there.

good info guys, ive done quiet a bit of research on this now (thanking google). It apears that the closed chamber heads have a better squish value/properties and if used in conjunction with a lower (8-8.5:1) compression ratio would work well in boosted applications. Sharp edges and points also create hotspots in the head promoting detonation, smoothing these out will help and drop comp. ratio a fraction.

Heres a couple of links on water injection and detonation i found

http://autospeed.drive.com.au/A_107970/cms/article.html

http://www.superchargersonline.com/content.asp?id=104

Zoom did a water injection technical article over a couple of issues a while back.
i have it here somewhere in my stack. ill try to dig it up today.

I sold some mags to a pommy bloke who told me about a magazine he saw back in pomgolia.
The gist of it was, They got a window washer bottle and pump, heated up a pair of side citters with a torch and cut/melted the end of the rubber hose. Then drilled threee tiny holes in the flat end. This was routed into the intake of the turbo. It was actuated by a hobbs switch, so it only pumped once the boost had reached (whatever level it was) He said that in the article, by doing just this, they were able to advance the timing by (I can't remember the figure) but it also gave them quite a respectable horsepower gain too. (can't remember that number either)
Its a bit of a third hand story, but you get the idea. Another bloke I know swears by using boost pressure to force water/alcohol out of a sealed resovoir, and into the intake. The inportant thing would be to use tiny delivery holes, or having the delivery tube/nozzle aimed closely at the centre nut of the turbo wheel. Thus the significant conrtifugal force would aid the atomisation of the injected liquid. Some folk proclaim that liqud into the intake of a turbo will anihlate the compressor wheel. Yet drawthrough turbo's don't seem to do this?

Sikdatto1200 - if you read the fine print on any bottle of octane booster it states that they are using a different points system. It's very sneaky but they somehow get away with it. Nulon Pro Strength octane booster is the one I use and, presumably, the one Wodie uses too and it is a very effective product but there is no way it lifts the octane rating of the fuel to 105.
Matty

Hmmmm, detonation eh?
Here's the way I remember it from my old days on the tools, & keep in mind, this is digging back about 35 to 40 years into my memory.
Accurate corrections are invited.

Definition.
Detonation is when the charge of fuel/air, or a portion of the charge of fuel/air, spontaneously combusts [explodes] or 'detonates' The fuel charge is supposed to 'burn'. It does in fact burn, almost at the same speed as the powder in a rifle round.

How does it happen?
This is when the fuel charge in the cylinder, compressed by the rising piston, is set alight by the plug. It starts to burn in a flame 'front' across the compressed charge, & as it burns, the rising pressure of the consumed fuel compresses the unburned fuel even more. There comes a time when the unburned charge simply reaches the point of self ignition & the whole thing just goes bang.

The fuel.
Fuels are like rifle powders, they are made with different burning rates. This is measured with an 'octane' number. The lower the number, the more volatile the fuel [the quicker it burns] & the more chance that it will detonate. Higher octane fuels burn more slowly. Low octane fuels are less costly to produce as they don't have as many additives to control the burn rate.

How do we control it?
Back in the days when petrol/gasoline was little more than kerosene, a brilliant engineer named Ricardo discovered that if you could agitate, or swirl the gas mixture, it would propagate the flame much faster & burn the fuel before it could explode. Up until then combustion chambers were little more than bowls over the piston & valves.
By placing a portion of the combustion chamber so that it covered a portion of the piston, leaving a very small gap between them [the thickness of the gasket in many cases] a portion of the charge would be squeezed in there, & it would jet out into the chamber causing a great deal of swirling. This allowed an increase in compression from something like 4 to 1 up to as high as 6.5 to 1 in some engines. This was on improved kerosene remember.
So high swirl can be a great help.

Fuel quality.
During the 50's fuel companies started adding Tetra Ethyl Lead to fuel & this slowed the burn rate noticeably, thereby raising the octane rating by a fair amount, but at a price. This is when 'Super' grade fuel was introduced & the increased octane rating allowed the Dodge hemi to go from 7.5 to 1 compression in '55 to 9.5 to 1 in 1956. That's two full points in one year. Other manufacturers did the same.

Timing
If the fuel is set on fire [ignited] too soon, with the piston still rising, it is trying to compress the fast rising gas pressure in the cylinder. This pressure can still rise high enough to cause the unburned portion of the charge to 'detonate'
Clearly, we want enough advance to ensure that the charge is lit & burning, but not so much as to overdo it. The faster the engine revs, the sooner in the cycle we need to light it as the burn rate stays fairly constant, but the time available to get it burning right becomes less.

Boost
Now this is where we have problems.
By cramming more air/fuel charge into the cylinder then it would normally hold, we push compression PRESSURES sky high, so we are already looking at the possibility of detonation by virtue of the higher cylinder pressures even as the spark plug sets it off.
The fixes for this are the same as before, but some are more practical.

REDUCE THE C.R.
By reducing the compression ratio, we actually get more fuel into the cylinder [more combustion chamber volume], but we do not face the potentially astronomic compression pressures that we would at standard C.R. The extra fuel in the cylinder still gives us more power, but with reduced chance of detonation. The lower the CR, the higher the permissible boost, but the more the engine becomes a slug when 'off boost'

HIGH SWIRL
While modern fuels have much better burn rates, the old high swirl rate still adds its measure of protection by propagating the flame front more quickly through the volume of the charge rather than needing to burn across it.

HIGH OCTANE
The higher the octane, the less chance of detonation.

BOOST RETARD
As the boost comes on, the compression pressures rise & the likelihood of combustion pressures rising too far during combustion also increase, so we need to set fire to it later than before to avoid excessive pressure rise & detonation.
We need to find a way to RETARD the spark from the position it would be in when normally aspirated while it is running & tie the amount directly to the boost pressure. This is the hard part & is, in my view, the single biggest killer of your carbureted, blown engines. With EFI, the timing map is tied directly to M.A.P. [Manifold Absolute Pressure] & the computer controls the timing, so all is well.
When the timing is right, the rise in pressure is also controlled by the fact that the piston will have gone past TDC before the critical pressure is reached & is moving away from the head, thereby increasing the volume in the cylinder & controlling pressure rise. [to a degree]

SUBSTANCE ABUSE.
Water injection is used to help cool the intake charge & also to slow the rate of combustion. The steam created assists in this regard while contributing to the pressure rise overall. Methylated Spirit also works I'm told, but I don't remember why. Octane boosters do the same thing, they slow down the burn rate [were talking milliseconds here] & allow a more controlled combustion.

CONTROL THE BOOST PRESSURE.
Yeah, I know, everyone wants 30 pounds of boost & an A15 becomes a V8 killer, for a few seconds. If your engine isn't built for that kind of power, then perhaps we should screw down the boost pressure.
The lower the boost, the fewer the problems & the longer it will live, so you need to strike a balance between power & engine life. That will be your call, but 5 to 6 psi is often a good starting point in a home built application, & work up from there.

Hopefully this overlong tome will provide some of the basics

Good thread idea sikdatto1200,
Here`s some thing to check and some remedies,
-ENGINE CONDITION, piston damage, ring wear, poor oil control .(will cause mixture contamination and lower octane rating)

-BLOCK PRESURE, water pump must be making fairly good block presure (about 25lb)
never run an engine without a thermostat or suitable restrictor to maintain good block pressure. otherwise you will be getting localised boiling (Hot spots) around exhaust valves and combustion chambers leading to higher combustion temps and detonation. Even tho the temp guage is reading normal!!!

-INTAKE AIR TEMP. This is probably the the most important one for turbo engines. I cant recall the exact figures but something like for every rise of ten degrees c in air intake the fuel octane requirement goes up by one point..(feel free to correct my figures here) Realising that a turbo compressor at at 65% eff. making 20lb boost on a 20 deg. day has a discharge temp of 120degrees!! This is where intercooling comes in!!
Draw through carb setups are the most handycapped here.. Increase the fuel octane or a very good water injection set up might get these setups out of strife unless you lower the compression, which can give you a sluggish engine off boost.

-OTHER CONTRIBUTING FACTORS, mixture quality, the shape of the combustion space(plent of squish).Igntion curve and total advance, plugs, the cars gearing, engine size v car weight ..

Or something like that,
Simon.