My brother just got headers on his charger. He is going to the dyno and will have the A/F charted. I believe headers will make a speed density system run a little leaner but from what I've seen these cars need to be leaned out some.marlinspike said:Bugszrt, it's cause he's got aftermarket headers on.
What A/F ratio do you consider the onset of problematic, and what A/F are you aiming to achieve?JMatt said:Let's pretend that with cold air intakes, and/or performance exhaust systems, that the air/fuel ratio leans out - perhaps even leaner than ideal. How would I trick the car into running richer?
It is possible that Hennessey has ways to work the PCM, but I am skeptical on that. All the tuners I have contacted and the info I have read points to a very difficult PCM. However, it is also very possible that very few enthusiats have come onboard with DCX products to really push the aftermarket. LT1 edit was kind of the starting point for GM tuning as we see it today and my understanding is that a couple of skilled computer guys got involved with F-bodies and started looking at the code. It just kind of exploded from there. Maybe some skilled computer boys/girls will get into the LX platform soon and want some modsmarlinspike said:Speaking of getting the 6.1 flowing, musn't Hennessey have been able to mess with the computer in order for his 392 stroker to work? Is he holding out on us on the computer front?
Is that all? I have a mechanical injection car that runs at 45psi, I would have thought by now they'd be much higher pressure, especially in these high hp engines.John Hennessey said:most fuel injectors are rated at 3 bar or 43.5 psi.
I am speaking of WOT operation and as you admit yourself "leaner if you have the octane to support it." I have to run FTP 3 bag sim tests and do specific grav tests on pump gas and I will tell you that OCTANE fluctuates nearly a whole point from tank to tank or brand to brand for the same "91" octane fuel. CA fuel sucks to say the least. If you are talking engine dynos and constant load 13.7 is not a bad number to achieve BUT we are talking street cars where they are exposed to non-spec fuel, four passenger loads 15% inclines and sudden changing load conditions (spinning tires @ 4500-6000 then getting traction.) A street vehicle tuned @ 13.7 for WOT is careless tuning when what you are trading is 5-6 HP for substanitally higher risk to detonation. Race cars are an entirely different game-controlled environment, controlled fuel, purpose built car.marlinspike said:14.7:1 is stoichiometric so how can leaner than 13:1 be problematic? Besides, leaner gives you more upper end as long as you are still burning all the O2. This engine is what 10.5:1 compression? I don't think you'll gain anything going from 13.5:1 to 12:1, maybe down low but you'd lose enough to more than counter that up top. Max power is typically around 13.7:1, leaner if you have the octane to support it.
What he said was injectors are RATED at 3 bar not that it was the pressure most cars run at. All my recent cars (GM) run 52-65 psi depending on whether they have bypassing fuel systems or static pressure. My carbed Nova is a standard 12-15 psi.Is that all? I have a mechanical injection car that runs at 45psi, I would have thought by now they'd be much higher pressure, especially in these high hp engines.