Everyone says a tune isnt required, but the fact remains it will lean the tune, and no one has posted saying they have dyno tested or used a wideband O2 to even see what the a/r ratio is, so until someone actually tests it they have no way of knowing.
Here is what I know. Dodge stock tune at redline 11.5:1, DiabloSport tune at redline 12.5:1 Fully optimized (on my car, Diablosport dyno sheet for proof)
When I installed JBA headers (independant dyno tests show 9-10hp) it leans the Stock tune to about 12.5:1 (tested with my wideband O2)
The srt-8 6.1L cars have been dyno tested by Solo saying +20hp. Something that delivers double the hp of a header that leans the tune from 11.5:1 to 12.5:1 is going to lean it even more.
SRT-8 engineers says the cats are the most restrictive part in the exhaust flow from heads to exhaust tip, so its reasonable to assume a high flowing cat would deliver 20hp.
DiabloSport has done testing and says cai, cat back, or both are acceptable with the same tune, but ANY other high flowing mod (headers, ported heads, high flows, strate pipes, camshaft, etc.) requires custome tuning.
The truth is, we need to see a/f ratio from a dyno to really know, but anyone saying something that delivers double the hp of an item that does require tuning, is being nieve.
Ask anyone who has done tuning if 13-14:1 at full throttle is a good idea.
If simple shortie headers on the 5.7L lean 11.5:1 to 12.5:1, then what is something that delivers double the hp going to do, on a 6.4L?
Can you run lean? yes
can you use 87 octane fuel on a car tuned for 91, or 93? yes
can you run 5psi on a stock engine not built for boost? yes
can you live with 250 collestoral, and smoke 3 packs/day? yes
is any of that a good idea, or is any of that safe? NO.
Look for tuning threads and you will read everyone screaming 13:1 is crasy unsafe, and will gernade the engine.
I can tell you on a 5.7L going from stock exhaust manafolds to jba shorties you need to add 3% fuel, so if this mod has double the hp, then I would start at 6-7% fuel. 6.4L?
Its true, Im the only one saying you need tuning, but if you look at my resoning, and ask any other person, and read any other thread you will see why I am warning you.
The custome tunes do a couple things to get hp, advance the timing for 91 or 93 hp, remove the torque limiter, and lean the a/f ratio for peek hp. With a custome tune, B&G, or DiabloSport your allready lean to the limit. Adding any mod that leans it more and its going to far. No it wont auto tune. The comptuer is designed to provide a fixed amount of fuel at full throttle, its called open loup. In closed loup / non full throttle, the front oxygen sensors provide info about the burt fuel, and the comptuer adjusts a/f ratio for a constant 14.7:1. When at full throttle, it is pre-programmed to use a fixed amount of fuel regardless to mods, this is where custome tuning is needed. The custome tune leans the a/f ratio to a fixed amount of fuel and does it blind. Its set to a fixed amount and if you open up the front or back end it doesnt get more fuel, but does get more air, and that makes it lean out. Leaner tunes get hotter, and can cause pistons to brake, etc.
non full throttle auto tunes to reasonable levels with the o2 sensors, full throttle is fixed, and requires custome tuning.
When you do any change like the following you need to get another dyno tested custome tune, headers, high flows, camshaft, ported heads, bore, storke, bore and storke, turbo, or super charger. Any of those parts that are changed require a custome tune after each mod.
The fact you allready have a tune is saying you are allready lean to the max, adding anything that leans it more is bad.
If you for example had a 5.7L and the stock tune, and added shortie headers, then your ok, because that leans it to where the custome tuners lean it. Your allready there, and going to go further.
07 3.5L Charger K&N CAI, Magnaflow Cat back, JBA shorty's, DS 93 tune, sold, 2010 Challenger R/T 5 speed. 180 degree Thermostat, fan settings lowered, CC, ceramic brake pads, slotted rotors, red and black caliper paint, Challenger label for calipers, Corsa Cat back, functional hood ducts, and hood struts, 93 DiabloSport tune, Mopar drop in filter, JBA Shorties, Wideband O2, custome tweaked tune, Anti-sway bars front and rear, end links, strut brace, 12" subwoofer with amp.
Last edited by Challenger370; 08-25-2012 at 11:18 AM.