On my Miata-Turbo swapped Triumph Spitfire project, the car is running rich and fouling the plugs. I am in the early tuning stages but don't want to make major changes to the fuel map until I am sure that there is not something else causing the problem. Here are the specs and then more on the problem.
1999 Miata 1.8 engine
Stock Red injectors
T2 Turbo
Intercooler
MAF Delete (replaced with GM Intake temp sensor)
Hydra 2.7
Wideband O2 sensor
Flyin Miata Turbo tune for stock injectors
Hydra is reporting all sensors working, did the calibration for the TPS and O2 sensor. Car starts and runs but is obviously running rich and will eventually foul the plugs with fuel.
Any ideas as to what is causing it to run so rich out the gate? This engine was a JDM unit, but I have used a US wiring harness. I also replaced the Throttle body with a used unit as that would replace the TPS and Idle Control Valve as a test, but still running rich.
What's the Hydra report as the AFR?
We have a tune for stock injectors?
I would tend to think that as long as your fuel pressure is pushing what it should be, not more, then it's probably something in the tune.
Injectors pretty much just open and close when they are told to, so fuel input is some formula of what their flow is, along with the pressure of the fuel. So unless there was a blockage preventing enough air from coming in, I would think it's something in the tune. Like Keith was getting at, make sure the tune is set for the correct injectors.
(Just thinking out loud here, I'm certainly not an expert!)
If it's running rich, that usually implies the injectors are too big for the tune. But stock injectors are not big. At idle, the injector response time does become a factor - a fast-acting injector will deliver more fuel at short pulse widths than one with a slower response, and this needs to be incorporated into the programming. What's the AFR like if you up the revs or under load?
I have the plugs pulled and battery out, so will put it back together and let you know the AFR at idle and under load.
And yes, you do have a tune for stock injectors :-)
Upgrades will be coming later, but I am not looking for max power, car is quite light so 200 HP or so is more than enough for this stage.....
I will put it all together over my lunch break today and let you know the AFR. But was thinking it through this morning also noticed the post on rebuilding fuel injectors. I had originally purchased new injectors, but did not have a map for them, so reverted back to the stock injectors. Assuming one or more of the stock injectors are not up to spec (dripping, etc...) this would also likely be the cause of the problem? Thinking I need to send out my used injectors as I have no idea if they are all flowing correctly and are evenly matched.
If one injector is sticking open, then you'd foul a plug a on that cylinder. I highly doubt all 4 are sticking, but there are ways to check by watching fuel pressure drop off with a fuel pressure gague after the engine stops as it should stay for quite a while before bleeding off, open injectors will drop fuel pressure quickly.
Also there is the factor of what temperature plug you're running. For a turbo car, colder plugs are generally recommended, but they can have issues with fouling. Stick with stock temp plugs initially until you get into tuning under boost.
I would look at what the AFR is at idle, and try to set it to remove fuel until it is idling at something reasonable (AFR at idle isn't as important as idle quality) as that won't impact anything except fueling at idle. Once you start tuning the rest of the fuel map is where you want to be careful about AFRs and not running too lean or too hot, etc.
