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Backfire on throttle transient.

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I have Suzuki Swift 1.5L M15A engine with 8PSI turbo kit.

The ECU is Haltech Elite 1500.

The tuning done step by step according to your video guides.

The engine start and runs fine but I have some issue with the tuning.

The main problem is Backfire on throttle transient.

When full acceleration 100% throttle up to 5000-7000RPM then throttle down to 0%.

At this point if I touch the throttle (doesn’t meter how much 1% Or 100% throttle) I will get backfire.

No backfire on deceleration at all, no backfire on any other state.

I think it because of unburned fuel, I can see the AEM wideband O2 show very rich mixture on deceleration.

Please help me to prevent this, try multiple solutions including configure the DECEL (injector cutoff) but nothing solve it or even change the backfires so far.

On my personal car i will add alot of deceleration fuel to the free rev and also the heavy vac sections on my map the pull all the timing out in these area's to cause the heat from the exhaust to ignite the fuel in the exhaust causing it to pop and crackle on free rev and decel when cars hot

Maybe turn ur map trace on and watch ur fuel and timing map were its happening try pulling fuel and adding timing to see if it stops it

Have you confirmed the decel cut is going active?

Is it intake or exhaust?

Sequential or waste ignition?

The decel cut is going active but not enough, don't understand why, i can see very rich mixture on hard DECELS, AFR 10 .

The explosion is from the Exhaust side.

wasted spark ignition system.

one more thing comes in my mind, if it was fuel issue and the cutoff wouldn't work then the explosions will Occurs during DECELS but It happens immediately as I try to accelerate and just one explosion (big) per event.

I'd say it is too rich or lean to fire on the first cylinder that fuels on the transient fuel reintroduction but lights off when mixing in the hot exhaust, possibly assisted when waste sparking on overlap/exhaust stroke. You will probably find if you get transient enrichment/wall wetting right it goes away although with the waste spark there is potential to still get a bit of injector phasing sees fuel go through it on overlap into a still hot exhaust with a bit of fresh air in there from the overrun.

It's a bit of a long shot, but have your injectors ever been cleaned/serviced? They can drip a little bit on fuel cut.

Given the evidence you've provided, I'd also be suspicious of an injector leaking. If the fuel cut off is functioning correctly then there should be no fuel to ignite when you get back on the throttle. It certainly isn't normal and you will typically see the wide band move lean during DFCO.


Thank you all, your advises help me solved the problem.

I change the head cover from the original M15A(waste spark) to M16A(direct fire).

use the four ignition coil from the M16A.

configure the haltech to direct fire and no pops and booms any more.

One important thing, the firing order is upside down from HALTECH wiring, it give me hard time to find the solution.

injector configured 1234 and ignition 4321, that is the only thing.

Glad you got it sorted.

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