Kugelfischer Injection Competition/Performance Tuning Tips
A properly operating Kugelfischer injection system can produce as much as 35 horsepower more than one that is functioning improperly. And many drivers don’t even know that their tii is not running properly. If you intend to use your tii for more than hauling groceries, you will want to pay some attention to the following areas.
An excessively rich mixture will not improve performance. A lean mixture, even slightly lean, will hurt performance considerably. Maximum performance is obtained only when the mixture is just right. And that means at full load, high RPM—not just at idle. The proper calibration of a Kugelfischer pump requires a proper test bench and cannot be done* without one. But there are several things you can do to avoid unnecessary power losses due to poor fuel delivery.
Check your injectors: Injectors deteriorate with use and abuse (rust, fuel gum, crud, etc.). Check them regularly for opening pressure and spray formation. Check injector installation for proper torque using fresh copper washers.
Check your fuel pressure: Low fuel delivery pressure causes fuel starvation at high speed, full load operation Fuel pressure deterioration has several causes.
First, check the electric supply pump for proper delivery pressure. Disconnect the fuel supply line to the injection pump at the inlet banjo. Test delivery pressure with the ignition on and the engine not running. Pressure should exceed 50-60 psi. Low pressure indicates problems with the supply pump. Excessively high pressure indicates that the pump pressure relief valve is not operational. Correct as necessary.
Second, check operation of the pressure maintenance valve. Re-connect the fuel supply line the pump banjo. Connect a pressure gauge to the fuel supply at the cold start connection and turn the ignition on with the engine off. Line pressure should not be less than 28 psi. Start the engine and blip the throttle to 5000 rpm. Fuel pressure should not drop below 25 psi.
Third, check fuel supply volume. Disconnect the cold start fuel line and turn the ignition on with the engine off. Measure the volume of fuel delivered into a calibrated container. Volume should be (pick one) 29 gal/hr, 1.83 liter/min, or 0.46 liter/15 sec.
Check your linkage: Loose, sloppy linkage must be replaced and any binding or lack of full travel must be corrected. Check to be sure that the throttle plate (butterfly) opens fully when the accelerator is fully depressed. Check to be sure the throttle lever on the pump contacts the full load stop when the butterfly is wide open.
Replace your fuel filter: The standard tii fuel filter is a little small and since it filters out very small particles (5 microns), it may easily partially plug, reducing both fuel pressure and volume. Consider replacing the filter with a larger 3-series (non-CIS) fuel filter.
Synchronize the air/fuel proper: At full load, high speed (and even part throttle) settings are much more important than idle conditions. Yet too much time is wasted chasing a smooth idle while sacrificing full load performance.
Depending on the specific engine configuration, a CO setting of 2.5-4.5% at idle is an appropriate target but even more important is the CO reading at full load, wide open throttle. Even when the idle speed CO values are achieved, there is no assurance that the air/fuel synchronization will not go either too lean (<2.5£) or too rich (>5£) at other throttle positions.
This of course is where a dyno comes in very, very handy. Lacking access to either an engine or chassis dyno, good mixture ratios can be achieved through the use of a portable, on board CO meter. Space prohibits a complete technical discussion of this topic. Call use for details or for Tech Bullet *7: Power Tuning the tii.
Fuel quality: The til engine requires high (93) octane premium fuel (octane defined as [ RON* MOM]/2). If engine modifications have been made (i.e. cam lift, compression ratio, etc.) then even higher octane fuel (95-100) should be used. When a fuel with lover than required octane rating is used, ignition timing must be retarded to prevent detonation. The result is a loss of power. Most street ignition advance settings are somewhat conservative (due to fuel limitations) and additional performance can be achieved with a slightly increased ignition advance—but onl y if detonation is avoided.
If racing gas is not available in your area you can use a blend of pump gas and aviation gas. Increase the avgas content until knock is eliminated. If avgas is a problem, a blend of 15-20% toluol (an aromatic used by refineries to raise octane rating) can be used. Don’t overuse toluol since it burns rather sooty at high blend levels and most pump gasolines already have some in it.
Knock control: In order for an engine to make maximum power and stag together it is absolutely necessary to control detonation—under all operating conditions. This means running right at the brink of destruction and yet never crossing over the detonation threshold. Contributing factors to knock are numerous and each must be controlled. Motronic does it with a pre-programmed ignition map in memory.
We do it by use of a knock sensor which automatically controls ignition advance. By being adjustable, it permits tuning for maximum power using a range of fuels without destructive detonation. Engine knock can either be audible or inaudible. The kind you can hear can be easily avoided if you pay attention and listen carefully. Inaudible knock is more dangerous for it goes unnoticed until damage is terminal.
For more information, call us and ask for Tech Bulleting #6: Knock Control for PoWer Production.
Heat control: Better combustion produces more horsepower and more heat. Excess heat produced by high performance engines, if not properly controlled, becomes a major destructive factor which quickly leads to engine disaster. Heat control is essential for several reasons:
1. Reduced temperature (cool, but not cold) cylinder heads produce more power by reducing the temperature of the incoming air/fuel mixture thus increasing charge density (an improvement in volumetric efficiency).
2. Higher coolant temperatures result in higher oil temperatures. Excess oil temperature produces oil film breakdown (piston ring and bearing wear), oil deterioration due to oxidation and high oil consumption (due to evaporation and crevice creep-age). By controlling the coolant temperature you may avoid the necessity of an oil cooler.
3. High coolant and head temperatures produce nucleate boiling in the cylinder head. The downside effects are localized hot spots (steam pockets), increased thermal stress (head cracking) and of course the inevitable dragon—detonation. Detonation also cracks heads, breaks piston ring lands, piston rings, connecting rods and can cause erosion of the piston tops and combustion chamber wall surfaces. I’ll tell you, it’s not a pretty sight.
Follow the cool ing maintenance procedures outlined in the maintenance section. If overheating persists, and you have a stock engine, find the cause and correct it before terminal damage is done. If you have a modified, high performance engine consider fitting a larger radiator or scoring with a core that has a higher fin count (fins not tubes are what count). If your car overheats only at autocross events, try running with the heater on to remove additional heat. Given the choice between an oil cooler or an improved radiator, go for the radiator. Lower coolant temperatures will lower the oil temperature too.
Marginal cooling systems always produce marginal, short lived, performance engines.
Original article by:
Precision AutoResearch • 901 Hillside Drive • Bensenville, IL 60106 • (630) 766-4402 • [email protected]