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Does anyone know what the stock air fuel ratio is for the Magnum engines? I want to get a computer program (B&G) done because I believe that is the only way to set that perameter. The reason being is that when I manipulate how my fuel management reads the boost on my ProCharger I can get 25mpg on the highway. I come across this strictly by accident so I am trying to find the proper way of going about it. I did not have an air fuel ratio meter hooked up at the time so I was unable to see how dangerously low my mixture had been. It could not have been to bad she moved right on down the highway.

 

I'm not positive on this but I think stock is like 13 or 14/1. You can take it down to 9 to 10/1 and be safe. But the motor won't last as long I would say.

 

I though I remembered HankL posting 13.2:1.

Isn't the theoretical perfect ratio 14.7:1?

 

13.2 or 14.7 either one is extremely safe and plenty rich. ProCharger recommends 11.5 anything less can be damaging under boost. I would have to say that 11.5 or 12 would be fine under stock performance. Not to mention increase your gas mileage. 25mpg would be great to have on the highway.

 

Correct. If you're looking forthe term, it's stoichiometric combustion, which is defined as all the air and all the fuel burned completely.

You're thinking is a little backwards here. 11:1 is about as rich as most computers will ever trim under heavy acceleration. If you're running that ratio cruising, yourPCMis gonna get really pissed and throw P0172 & P0173

 

I was seeingstoich or richer (14.5-14.7)when cruising with the MP PCM. (no flash) With the SMT6 piggybacking itI leaned it out a bit morefor cruising (15.0) to try and get a bit better mpg. WOT I shoot for 11.3-.5 with boost or 12.8NA.
Those numbers were read threw both the stock narrow band o2& smt6/laptop and from my AIM digital a/f gauge with a wide band o2.

Id pass on the B&G and go with an SCT tuner instead. I dropped the SMT6, DFMU and inline pump for areturn fuel system (650LPH/65lb inj) & the FAST stand alone.

 

Puzzled[&:]

The lower the number the leaner the mix. My motorcycle is too rich at 14 should be 12.5 13.This made me wonder about some of the comments. The guy down the street who runs ProCharged strip Camaros says that 11.5 is good and that twelve is real safe (assumed he meantrich). Different for motorcycles?

 

Well ok! It seems for instance lets say 13 to 1 13 parts air to 1 part fuel , compared to, lets say 16 to 1. 16 parts air to 1 part fuel. The more air the leaner it is. Correct?

 

I stand corrected. Thanks

Why not the B&G but the SCT? ? What brand on the return? How does the Fast override the PCM for the fuel sending? Ease of install and programming. Seems like an awesome product.

 

A/F ratio is the same for a truck, car, boat, motorcycle, atv, snowmobile whatever. Smaller number means rich, bigger number means lean.

The B&G is a one tune deal, have to send it in to get flashed. Sometimes has to go back more than once. One guy I know, 3tunes and still wouldnt run right so he pulled it.(mild level na 360) SCT tuner plugs into the OBDII port and comes with 2 tunes and can hold 3. (if you buy from hemifever) You can get updated tunes emailed so no down time. Costs more but you get what you pay for. Guys are seeing better results on dyno's/dragstrips with the SCT. Not sure how big an injector they can control (came out after I got my fast)

As far as the FAST stand alonegoes, 2 of the connectors that go into the PCM plug into the FAST instead. Only the trans is controlled by the pcmif you have a FAST. Need to modify the wiring harness a bit, think KRC will mod the harness for 250. With a stand alone, need a laptop for tuning. Most good dyno shops will already have fast software in their laptops for tuning purposes so you dont have to buy one. If you do have one though you can tune on the fly. Any changes you make, hit load/enter and your on the new tune or go back to a prior saved one(unlimited # of tunes). With the FAST there are 144 sites for various rpms/engine loads for both fuel and timing that can be adjusted +/-. Havent tuned with it myself yet but watching buddy tune his pretty well identical to tuningwith thesmt6 (124 sites per) I was using before. The FAST can handlehighimpedance or low impedance injectors up to 96lbs. 50lbs was the max with the SMT6 cause it couldnt handle low imp. injectors.
You can monitor all sensors,including a/f from the supplied wide band o2,do diagnostics and data log to see how the changes have affected things while say making a pass down the dragstrip Downfall of stand alone engine management is the cost. With harness my bank to bankwas 2250, the newer xfi version starts at 2600.

One buddy put down 356hp/399trq at the wheels with his B&G flashed NA408. After he swapped from Moparheaders to long tubes and added/tuned with the FAST it put down 401hp/457trq. Headers would help a bit (maybe 15rwhp) but no where near what he gained with the better tune.

My fuel system is KRC billet rails, Summit 20gall alum cell modded for 10an return, FAST 65lb low imp inj (all 2.5 ohm) with Aeromotive Eliminator fuel pump (12an in/10an out), controller (must have for continous duty on street) 100 & 10micron filters and their Pro regulator. The reg. has 10an return and is boost referenced on a 1:1 ratio so Ill be running fuel pressureat 45psi na and with boost 52-59 psi (7lbs to 14lbs boost)instead of the 100psi I was seeing with the dfmu and inline & 7lbs. Pump is ratedto support1100hpfi & 1600hp na (new one now 1400fi/1900na) though the 65lb inj. willlimitmineto 1000hp.