Recently i converted my mazda rx7 fd to single turbo, and when i took it to a local tuner he experienced a lean fuel spike from the begging of the tune. The lean fuel spike happened randomly on different gears 1st - 4k rpm, 2nd 3.8k, 3rd 4.5k, after the spike happened the car continued like nothing ever happened ...its not a constant issue on same rpm.

We changed the spark plugs to new ones and checked if the spark is working well.Checked the injectors and they are working fine too.

On the logs of the tuner the lean fuel spike happened when the injectors are open, and fuel pressure is 60psi constant since i made a pump re-wire, and there is a constant 14v current.

Modifications done are as follows,
Haltech elite 1500, bosch 550cc primarys, bosch 2200cc secondarys, hks twin spark, dm motorsport fuel rail, oil metering pump delete,
Garrett t3/t4 turbo, aftermarket manifold, hks wastegate 50mm , haltech boost solenoid, tial dumpvalve, AEM fuel sensor in aeromotive fuel pressure regulator, AEM oil pressure sensor.

Any help or what can it be PLEASE?

 

Recently i converted my mazda rx7 fd to single turbo, and when i took it to a local tuner he experienced a lean fuel spike from the begging of the tune. The lean fuel spike happened randomly on different gears 1st - 4k rpm, 2nd 3.8k, 3rd 4.5k, after the spike happened the car continued like nothing ever happened ...its not a constant issue on same rpm.

We changed the spark plugs to new ones and checked if the spark is working well.Checked the injectors and they are working fine too.

On the logs of the tuner the lean fuel spike happened when the injectors are open, and fuel pressure is 60psi constant since i made a pump re-wire, and there is a constant 14v current.

Modifications done are as follows,
Haltech elite 1500, bosch 550cc primarys, bosch 2200cc secondarys, hks twin spark, dm motorsport fuel rail, oil metering pump delete,
Garrett t3/t4 turbo, aftermarket manifold, hks wastegate 50mm , haltech boost solenoid, tial dumpvalve, AEM fuel sensor in aeromotive fuel pressure regulator, AEM oil pressure sensor.

Any help or what can it be PLEASE?

 

Is there a pulsation damper in the rail? A lot of people end up with fuel line pulsation that is hard to pick up with analog gauges or low speed/smoothed digital logging with injectors that size without a pulse damper.

 

Thanks for the information but I already talked to the tuner about the pulse damper, but he told me that he didn't pick up any pulsation in the logging from the senors, and never used a pulse damper for any of the single turbo conversions, should i install one and see if this issue clears ?

Today i changed the secondary injectors to same cc ones and im getting really bad hesitation at 4k-5k revs and it stalls there doesn't go further up in revs, it seems like it got worse.
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do you have a log?

 

What is the fuel pressure doing when you have the lean spike? Most likely it's going to be fuel and not a spark thing.

You say 60psi constant fuel pressure - that is REALLY high. Is it boost referenced? Any reason why you're running that much fuel pressure?

Dale

 

Yes, my tuner has the log

 

When this lean fuel spike happens the fuel pressure is at 60psi at around 4k-5k and boost start to kick in and secondary injectors are already open ... Its not happening always the same rpm

 

Try lowering the injector staging and make sure you are running the newest Haltech firmware. It also sounds like your base fuel pressure is way too high. Set it at 43.5 base.

 

fuel pulsation damper?

 

Not a soul can tell you what the issue is without seeing the ecu file, and logs.

High chance its just a tuning issue, maybe a secondary injector transitioning issue.

 

Make sure you have been logging Injection Stage 1 and 2 Duty Cycle - watch the Wideband output shortly after the secondaries stage and see if that is when the issue has been happening. Myself and many others have had issues on the official Haltech firmware that does staging in a really stupid and roundabout way (drops the primary flow and raises the secondary to meet and they continue to flow upwards together) instead of the tried and true method that most other ECUs use (primary injector climbs until a set %, holds, and the secondaries come online and climb steadily to pick up the slack). Haltech has an "alpha" firmware that has been in testing most of the year and it seems to have all but cleared up this issue for myself and many others.

Previously, most tuners got around the issue by overcompensating by the boatload in the VE map (sometimes as high as 160%+) curve but it always results in semi-unstable fueling if conditions change slightly. Unsure when that firmware will be officially pushed out but I have not seen any downsides to it yet. It did require a re-tune, however.

 

Thank you, I'll try that!

 

Im going to install one on the fuel rail from radium performance.

 

Ill show this to my tuner thanks

 

Ill try to get the logs and post them later on

 

Can that spike be corrected with more fuel?

My setup had a rich spike around 5000k which varies in strength and rpm by gear. I ended up just reducing fuel at the rpm it occurs.
It appeared after going single from non-seq.
I determined mine is nothing more than a difference in air flow caused by resonance in either the intake or exhaust.

 

Thanks for the tip il check !
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Problem solved, it was a faulty injector issue.