jonbill

I think thats a significant difference. Adjusting the throttle stop on that carb will move the others. Have you got a pic of how the throttle bodies are linked? I balance them by disconnecting the linkage and using air bypass to get each pair in balance with themselves and the throttle stops to get the 3 three balanced with each other. Then connect/adjust the linkage so they're still flowing the same at idle. They should then stay in balance as you open them.

There should be adjuster like this between each, to make each pair flow the same, and the bleed screw is to balance flow within a pair. If the bleed screws don't have enough, then hold the throttle body up to the light with the throttle closed. You'll probably see the butterfly isn't perfectly centered because they weren't assembled very carefully. So they flow different amounts of air. You can slacken the two fixing screws and recenter the butterflies to balance them. But.... Why does the first need more air on yours? That doesn't sound right.

I don't really remember I'm afraid, but I know there wasn't a lot of adjustment available. Have you looked at recentering the throttle plates to see if you can get more consistent air flow when closed?

Yes I did on the FAJs, I just about got the amount of adjustment I needed.

It's a welded p90a. I think the ports are 38mm. I think they must be as big as they can be since the head bolt holes broke through when we drilled them for m12 bolts.

the most valuable tuning tool for me has been this MLV histogram - I can drive around all day logging, and then load this and in one view I can see how close the tune is to where I want it to be.

yes, Speeduino uses Tunerstudio too - I'll share some screenshots and the tune. I'm switching to 50s because this engine doesn't rev out like my previous 2.9 did - it would zip round past 8000 but this one is more powerful below 6000 but isn't so keen to rev past 7000 at all. It might just be the longer stroke, but it could be the 45s are too small so I have to find out. on the motorway it does about 35 mpg (UK gallons, so prob 30mpg US). and I'm confident it's well more than 300bhp (but never proved it, because that costs money :)) VE table: Spark table: AFR table I only use closed loop o2 control at low throttle openings. Above that, it does hit the target AFRs quite well, after years of logging and histogramming with MLV. CurrentTune.msq

I run pure Alpha-N on my engine with Speeduino. 3.2 stroker with a diesel block. FAJS 45 ITBs. I have it working very well everywhere. Idle is managed with Speeduino's ignition advance idle control. It starts on the key from cold and hot without touching the throttle and idles at 1100 throughout. Its in bits at the moment, but when it goes back together it'll have 50mm Sherryberg ITBs.

What kind of a car and engine is "this beast"? If you're idling an l6 in an s30 with an unvented bonnet and no heat shielding on the exhaust, the injectors may well be heat soaked. But then again, if as you say you can add fuel until it stumbles and it still reads lean, then it sounds like a duff sensor or an air leak in the exhaust. Is it a genuine Bosch LSU4.9? Where did you buy it?

What sensor and wb controller is it?

Sounds like a duff sensor.

Thats almost invincible.

A couple of things that might help: When a cylinder doesn't fire, then the wbo2 reads full lean because the gas passing over it is atmospheric air. None of the oxygen has been used to burn fuel. This happens whether the misfire was because the mixture was too lean or because it was too rich. So when you're at 11 afr and go richer, it wont burn and so it shows lean. Telling TS that you have bigger injectors when you haven't changed them will make it leaner, because the calculation assumes that it can deliver the required fuel in a shorter time. Assuming your injectors are big enough for your power level, when you're maxed out on the VE table values (as your are) a larger required fuel value will give you more head room.

Pull the cam out and get it reground to a more aggressive profile. You'll get more power (maybe) and more lash clearance. Win win.

50s ftw.