Genset injection timing moves the point where the fuel starts to burn, and the exhaust temperature moves with it. Read how timing shifts the heat and how it is checked on site. Tesla Power records the setting at the works test, so send the pump data sheet to our sales desk for a quotation.
- Ask for the timing figure in degrees before top dead centre, because a name alone says nothing.
- Check whether the pump is mechanical or common rail, since the two are checked in different ways.
- Look at the exhaust temperature at rated load, because a late setting shows there first.
- Ask what the coupling looks like, because a slipped coupling moves the timing without any fault code.
What does genset injection timing change?
Injection timing sets the crank angle at which the injector starts to deliver fuel, and that angle decides how much of the burn happens before top dead centre and how much after it. Advance the timing and the burn starts earlier, so the peak pressure rises and the exhaust leaves cooler. Retard it and the burn starts later, so the peak pressure falls and the exhaust leaves hotter.
Nothing about the rating changes and everything about the duty changes, which is why the figure belongs on the data sheet rather than in a workshop manual. Tesla Power Equipment records the timing at the works test and again at the first service, so a drift is visible as a number rather than as a symptom.
Why does retarded timing raise the exhaust temperature?
A retarded setting starts the burn later, so more of the heat is released after the piston has passed the point where work can be taken from it. The heat that was not converted into torque leaves with the exhaust, which is why a late engine runs hot at the manifold and produces less power at the same fuel rack position. The exhaust temperature is therefore the cheapest indicator of a timing problem that a site already measures.
The same shift raises the temperature the exhaust treatment sees, so a filter or a catalyst sized on a correctly timed engine runs hotter than its design point. A genset for a site where the fuel quality is variable needs the timing checked when the fuel changes, because a slower burning fuel behaves like a retarded setting. the fuel planning notes treat the two as one question, and Tesla Power asks for the fuel specification before it fixes a timing figure.
| Timing | What the burn does | What the site sees |
|---|---|---|
| Advanced by a few degrees | Earlier burn, higher peak pressure | Cooler exhaust, more nitrogen oxides |
| On the data sheet figure | Burn centred on the design point | The rated figures hold |
| Retarded by a few degrees | Later burn, heat to the exhaust | Hotter exhaust, less power, more smoke |
| Retarded by a coupling slip | Burn very late | Hard starting and a hot manifold |
| Timing not recorded | Unknown | Every comparison is a guess |
How does timing move the fuel burn?
The fuel needs a moment to ignite after it is injected, and the moment is roughly fixed, so the start of injection has to lead the desired start of combustion by that delay. Advancing the injection moves the combustion earlier by the same amount, and retarding it moves the combustion later. The delay shortens as the engine warms, which is why a cold engine needs more advance and why a cold start is the most sensitive test.
The delay also shortens as the load rises, because the cylinder is hotter, so a setting that is right at full load is slightly late at light load. That is the reason a standby set that runs at a light load for most of its life shows a hotter exhaust than its rated figure suggests. Tesla Power states the load the timing figure was set at, because a figure without its load is half a specification, and the 500kVA canopy set carries the figure on the engine sheet.
What does the data sheet state about timing?
The data sheet states the timing in degrees before top dead centre at a named load, the method used to set it and the tolerance the engine maker allows. Those three lines let a workshop check a setting against the same basis the factory used, instead of against a figure copied from a different engine family. A timing figure without the method is a number that two workshops will read differently, and the check against the pump curve follows the ISO 8528-1 rating chapter.
The tolerance matters as much as the figure, because a setting inside the tolerance is not a fault and a setting outside it is. A 400kVA set at 0.8 pf carries 320kW, so 400kVA × 0.8 = 320kW; at about 0.21 L/kWh the burn runs near 67 L/h, and 67 L/h × 4,000 h = 268,000 L a year, so a setting that costs one percent of fuel is a number a buyer can price.
How is timing checked without a dynamometer?
On a mechanical pump the check is a spill test, where the delivery valve is watched for the moment the fuel stops flowing and the crank angle at that moment is read from the marks. The test needs no load and no dynamometer, and it needs the marks to be clean and the procedure followed in order. A spill test done at the wrong rack position gives a figure that looks right and is not.
On a common rail engine the timing lives in the control unit and the check is a diagnostic reading against the commanded value. The two methods are not interchangeable, so a workshop that only knows one of them cannot check both. the standby set range states which frames use a mechanical pump and which use a common rail system.
Which records prove the setting?
Three records prove it: the works test figure with its load and method, the spill or diagnostic check at the first service, and the exhaust temperature at rated load on the same sheet. The first shows what was set, the second shows whether it moved and the third shows what the movement cost. A file with only the first describes a setting and not a duty.
The exhaust temperature record is the one a site can keep without a workshop, because the set already carries a gauge. A rise of a few tens of kelvin at the same load and the same ambient is the first sign that the timing has moved, and it appears before the smoke does. Yangzhou Tesla Power writes the reference figure on the handover sheet so the site has something to compare against.
What should the offer state about the pump?
The offer should state the pump type, the timing figure with its load and method, the tolerance and the check that proves it. Those four lines let a buyer compare two engines that carry the same rating and behave differently in service. Most genset manufacturers name the engine and leave the timing to the workshop manual, which is where a drifted setting stays unnoticed, and the service interval the check belongs on follows the NFPA 110 test interval table.
Chinese genset suppliers who print the timing figure make the comparison possible, and a genset for the first year of service shows the difference in fuel and in exhaust temperature rather than on the quotation. A genset in a market where the fuel is slower burning needs the timing checked against the fuel rather than against the manual alone.
What does the handover file carry for the engine?
The handover file carries the pump type, the timing figure with its load, the method and the tolerance, all on one sheet with the serial number of the engine. A buyer who reads it can tell whether the setting was made on the same basis the manual uses and whether the exhaust temperature matches. Tesla Power issues that sheet with the set, so the first service starts from a recorded figure.
The file also carries the exhaust temperature at rated load, because a timing check without it is a number with no consequence attached. Genset documentation for an injection setting is only complete when the figure and the temperature appear together, and the engine bay that records both follows the works and the test bay routine.
Send the fuel specification and the annual hours with the enquiry, and the pump type, the timing figure and the check come back as one answer instead of three items a workshop has to reconcile. Tesla Power writes that answer into the offer, so the setting is visible before the order rather than at the first hot manifold.
Frequently asked questions about genset injection timing
It can save a little fuel and it raises the peak pressure and the nitrogen oxides, which is the trade the engine maker already made. Moving away from the data sheet figure is a decision with two costs. Ask what the emission limit allows before changing it.
Because the ignition delay is longer when the cylinder is cold, so the injection has to start earlier to keep the combustion at the same point. That is why a cold start is the most sensitive test of a setting and why a retarded engine starts badly.
A coupling that has slipped retards the pump by an unknown amount and the engine runs hot with less power and more smoke. Nothing in the control panel reports it. The spill test finds it and the timing marks confirm how far it moved.
It does, because wear inside the pump changes when delivery actually starts against when it was set to start. The drift is slow and the exhaust temperature follows it. A check at every major service catches it before the fuel bill does.
The principle is the same and the method is not, because the control unit sets the moment electronically. A workshop that only knows spill timing cannot check a common rail engine. Ask which system the set carries before booking the service.
It does, because a late setting sends more heat to the filter or the catalyst than the design point assumed. A device sized on a correctly timed engine runs hotter on a retarded one. Check the timing before blaming the device, and Tesla Power states the figure the device was sized on.