Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

Injector dead time

General Tuning Discussion

Forum Posts



Tech Articles

Discuss all things tuning in this section. News, products, problems and results. 

= Resolved threads



recently i have received a Nissan rb26 engine for tuning car has denso 800cc low impendence injectors, stock fuel regulator, motec m800 ecu and upgraded turbo’s.

we have started the car it idles perfectly, what got me confused is that as soon as i hit wot car goes lean which makes the car backfire after a sec or 2 it goes back to my target lambda ( tried to give it alot of acceleration enrichment but that only made the car richer after the backfiring) i have also checked if there are any fuel trims but non were applied.

could it be related to the dead time of the injector? Currently my dead time is set as the following,

16v 400

14v 600

12v 900

10v 1450

8v 2500

Did the voltage change when you hit WOT? What about fuel pressure? Perhaps the fuel pressure regulator can't respond to the increase in manifold pressure fast enough. What happens to the MAP? Is there an overboost condition?

Either something in the above or possibly rich misfire on initial enrichment? Does it run cleanly on boost?


voltage drops from 14v up to 12.8v as i hit the full throttle, boost pressure is steady at 1 bar, regarding the regulator issue i think if i disconnect the vacuum pipe going to it and keep it at a steady pressure it might help?


car is clean as it goes into full boost

The vacuum pipe to the regulator must be connected to the intake manifold. The increase in manifold pressure will cause an increase in the fuel pressure (relative to atmosphere), but the differential fuel pressure (rail pressure - manifold pressure) will remain constant -- which is what you want. Make sure you don't have a vacuum leak such as a crack in your vacuum line to the regulator.

On the M800, I believe there is an ignition compensation when accelerating -- what happens to the ignition timing when you go to WOT? Since you say there is a backfire, perhaps there is a bad ignition timing event. Are their any diagnostic error that occur at this time? (say a ref/sync error?)

Gold box accel enrichment is a blend of 3 tables, usually all have to massaged independently and each will have an impact on eachother so when I hear something like 'gave it a lot of accel enrichment' I get a bit of a red flag. You could also be creating an uncombustable event with too much fuel, hence the lean condition and backfire backfire.

Clamp is the amount of fuel based on a percentage of IJPU that was input on setup, so depending on how you had to set that up, you may be over or underfueling.

Sensitivity is often overlooked when I've helped folks in the past, they just jack up Clamp and get weird transients when in reality the ECU is just acting sluggish in adding fuel because that's what it's being told to do.

Decay rarely causes problems other than fuel consumption (and flames on a rotary) I've found but since you're saying or lean event lasts a full 2 seconds look there.

Last but not least, I don't particularly subscribe to Motec's suggestion that MAP be used as the accel table, I use TPS and sometimes use the Clamp Comp table. Your mileage may vary.

We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?