Hydra 2.7 lean AFR and LTT
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Hydra 2.7 lean AFR and LTT
I have been attempting and failing to wrap my head around the software on my new FMII install. The AFR at idle is a solid 14.7 at idle. but when driving it is running too lean, about 2 points too lean consistently. I have not gone far yet and have stayed out of boost for the most part, but on one of my runs today, I did go into boost. At 7 psi, it was 14.1. I should have been 12.2. will the long term trim take care of this, or do I start adding fuel to the base map across the board? I just want to get it safe, so I can drive it to get it tuned by someone who knows what he is doing. By the time I am confident to floor it summer will be over....
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Newb
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From: North of Shelburne Ontario, Canada on 100 acres
Added 25% more fuel everywhere above 1250 rpm. Brought the AFR to within a point? ie; 13.2 when the AFR table wants 12.2. Next question is how close does it have to be for LTT to take effect? All FM says is "in the ballpark", a fine statement, but essentially useless to a noob. I can't find it in the ECU manual either.
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Added 25% more fuel everywhere above 1250 rpm. Brought the AFR to within a point? ie; 13.2 when the AFR table wants 12.2. Next question is how close does it have to be for LTT to take effect? All FM says is "in the ballpark", a fine statement, but essentially useless to a noob. I can't find it in the ECU manual either.
I'd rather let the ecu correct by removing fuel than adding it. Add more fuel.
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You only want the long term trim to be +/- 1-2%. The better your fuel table, the lower the long term trims. So if you’re targeting 11.8 at 7psi, you should be 11.6-12.0
fyi, you can devide your actual afr by target for a percentage. So using the above 11.8 example, if you’re at 12.8, 12.8/11.8=1.085, multiply the fuel table by 108.5%.
fyi, you can devide your actual afr by target for a percentage. So using the above 11.8 example, if you’re at 12.8, 12.8/11.8=1.085, multiply the fuel table by 108.5%.
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From: North of Shelburne Ontario, Canada on 100 acres
Thanks curly, working on it. Should I zero the long term trims every time I change the fuel table? If I have it correct the datalogged AFR's will include the LTT trims assumimg the LTT is active, introducing an error in the correction factor, albeit a small one.
Last edited by Robin-42; Jul 9, 2018 at 02:10 PM.
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Just to update. In the stupidity awards, I should get an honourable mention. I decided to pull the plugs to check on them 1-3 looked normal, 4 looked like it had never seen combustion. It hadn't. It was sparking, but no fuel. There is no continuity in the wire from Hydra to the injector. There is one splice in there, made by me, with the harness on the bench. In other words, ideal conditions. Now I get to take the fuel rail out to repair it. A smart man would have bench tested it. Once I have a four cylinder engine again, I will zero the long term trims, put back in FM''s base map and start over. Still surprised at how well it idled, considering. No longer surprised how sucky it was under load.
Last edited by Robin-42; Jul 9, 2018 at 02:10 PM.
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Wiring fault was not my splice. Problem was at ECU. The wires are quite fine and the connector had been crimped with too much enthusiasm, breaking the wire. Fortunately I had ordered spare connectors and the tool, as earlier on in the build as FM had not included a wire for the VICS. I know....., I should have ditched the VICS.
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<div style="text-align:left;">Wiring fault was not my splice. Problem was at ECU. The wires are quite fine and the connector had been crimped with too much enthusiasm, breaking the wire. Fortunately I had ordered spare connectors and the tool, as earlier on in the build as FM had not included a wire for the VICS. I know....., I should have ditched the VICS.</div>
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From: North of Shelburne Ontario, Canada on 100 acres
Not sure why post 8 turned into a funky 9, but anyway, I now have all four cylinders getting fuel. Went back to original base map, zeroed all trims and started over. All the AFR's that I checked are within a decimal point or two. My weak defence on not picking up of fuel problem, was an all new exhaust, and my zero experience with turbo's. Now I have to learn how to drive a Miata that actually does something when you floor it.
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