Engine Issues

Setting the Engine mixture and throttle response
The setting of the second jet can only be done once you have set the main jet.The throttling of the engine is relatively unimportant until you’ve got top speed right.
Run the car, not with its wheels off the ground, physically run it and keep leaning the engine by screwing the main jet in very gently, 10 degrees at a time on the needle, until it cuts out. Then back it off, 20 degrees or so.

Once you have got the car running at top speed with the mixture right, then you set the bottom mixture, secondary jet.
The second needle controls throttle response. With throttle response, it is identifying what is happening which is the most important thing. If you open the throttle and it stutters and coughs and there’s lots of smoke, it’s rich, which means you have got to screw it in, the same as you do with the main needle.

Again, do it in 20 degree increments. Check the throttle again, and if the engine is rich you’ll have to clear it out before you check it again. You keep doing that until when you open the throttle, the engine gasps and there’s no smoke. That means it’s lean and you back it off a little bit until you get the optimum between the two; you can throttle it cleanly and it doesn’t gasp.

Then set the idle speed controlled by that screw with the spring. All that screw does is control the physical movement of the barrel so it is a throttle stop control. It has nothing to do with the mixture. Once you have the mixture right, all you are doing is adjusting the speed which it idles at.

N.B
The settings can vary on different days. On hot days you need to run a little bit richer. On damp days you can sometimes run a little bit leaner.

Here are a few extra tips to help you avoid the most serious disasters!

Fuel
Must have 18% oil content. Suitable oils include:

Model Technics
- Castor Straight
- GX
- Expert mix GN
Formula Irvine

After running in engines you can use Duraglow

Exhaust
Must be connected or richen up the mixture. Engine depends on back pressure from exhaust, ensure pressure pipe is connected and that fuel tank is pressurised, ie check to see that filler pipe is sealed after filling with fuel.

Questions sent to us regarding Engine issues:

Q Do we have to run the engine in as it currently has a very piercing note to it! from Team Stoic
A No real running in is required but they do have a high tone! Keep the revs down a bit and run a little richer rather than leaner. You could build the Dynamometer described in 'Engine' to tune and bench run in.
Look into the design of the exhaust system as the basic one is just that!

Q My engine won't rev
A See if you are starting it backwards. It may be too rich.

Q I am having problems starting the engine, the fly wheel is coming lose but the starter is turning the right direction to start the engine. How do I overcome this?
A This may be caused by a hydraulic-lock with too much fuel being in the combustion chamber. Let it run out by removing the glow plug and turning upside-down. Better that the clutch comes free than the crank or con-rod break.
The standard tightening procedure is usually enough to ensure the flywheel does not come off, i.e hold the flywheel in a vice or clamp and use a 7/16 AF ring-spanner. Do tighten as much as you dare without stripping the thread but don't use lock-tight as this gives problems later.
There could be the possibility of the clutch adaptor (part 82) not being threaded deeply enough. If this is the case clean out the thread with a ¼ UNF plug tap
Assembly drawing

Q How loud is the engine in the starter kit?
A This is impossible to answer as there are many factors that affect the level.
1. RPM (idle, full etc)
2. Silencer design
3. Silencer extensions
4. Mechanical noise(transmission etc)
5. Sympathetic vibration noise (rattles).
6. Carburettor noise (air filter or not and its design)
The only way to find out is to measure it with a db meter with 'A' scale weighting. Quite a few aircraft clubs have them as the UK tries to work to an 82dbA limit. It is more important for aircraft, as the 'cone of noise' is far more of a problem. Cars at ground level have obstacles around them to dampen the sound out. I hope this is of some use.
Best regards, Mark Wood Irvine Ltd


If you have any questions about your engine, please mail us

Setting up the carburettor and Trouble Shooting

Apologies for those experienced schools that can set up their engines to a tee but this is for those new folks that need some assistance.
By now most of you will have suffered the problems of engines not running reliably, too fast, too slow, no throttle response etc.
Check the basics first:
That you have compression.
That you are trying to start it in the correct direction; anticlockwise (looking from the front of the engine)
That your glow plug glows bright orange.

With the above you should be able to get your engine running like a sewing machine; however life is not always like that! Air leaks can cause problems that are hard to track down, to overcome this use silicon sealer on the 'O' ring and fixing screw heads.
Then set about tuning to the following:
Run in the engine in the car or on a test bench. Set the primary jet by screwing home then back out 2 ½ turns then keep leaning the engine by screwing the main jet in very gently 10 degrees at a time, until it cuts out. Then back it off, 20 degrees.
The second needle controls throttle response. If you open the throttle and it stutters and coughs and there's lots of smoke, it's rich, which means you have got to screw it in; a few degrees at a time.

Check the throttle again, and if the engine is rich you'll have to clear it out before you check it again. You keep doing that until when you open the throttle, the engine gasps and there's no smoke. That means it's lean and you back it off a little bit until you get the optimum between the two; until you can throttle it cleanly and it doesn't gasp.
Then set the idle speed controlled by the screw with the spring. All that screw does is control the physical movement of the barrel so it is a throttle stop control. It has nothing to do with the mixture. Once you have the mixture right, all you are doing is adjusting the speed which it idles at.
N.B. The settings can vary on different days. On hot days you need to run a little bit richer. On damp days you can sometimes run a little bit leaner.