11rubiwannabe

Mines an auto.....don't have 35's though

demtek9

Yeah the 35s added a bit of width. I think I could do it with the stock rims and tires...no way with these new tires. 35s cost too much to be burning them up though..lol

VEGASROBBI

Chrysler refuses to run an airflow (MAF) based OS so your Jeep is dependent on speed density(MAP intake pressure). SD works OK but is dependent on mathematical calculations for airflow. A MAF system is more stable and accurate.

Narrow band O2's are good at what they do - target stoich. 14.7:1 for gas, 14.2(which most of us run) for gas with about 10% alcohol and in the 9's for pure alcohol. NBO2's base feedback on O2 content in the exhaust - about 1.5% is stoich regardless of fuel(HC).

The NB O2's main function is feedback for closed loop operation. CL operation is most of the time you drive your JK. Exceptions would be cold start, performance enrichment(WOT or heavy load), lean cruise(no longer available in NA), hot mode and some others.

Manufacturers spend millions on calibrations for 1 or 2 bar forced induction engines. The trick is to go from vacuum(actually negative pressure) in the intake, cross over 0 psi and enter boost as seamless as possible. When faced with a SD OS this can be tricky and the result is surging, hesitations, flat spots, unstable A/F ratios, poor cruise control operation, etc.

I believe a roots style SC has an advantage over a turbo or centrifugal SC for tuning purposes.


A wide band O2 is a powered AFS which can read a wide range of A/F ratios unlike a NB. Using a WBO2 you can watch actual A/F ratios in CL and OL, especially PE which SC's run in a lot of the time. You want to stay in CL most of the time for MPG, drivability, cat protection and to reduce the risk of damage. When you get on it and you cross over from intake vacuum to boost A LOT of things change and many calibrations do not respond well. With GM LS engines 1 and 2 bar MAF based OS's are readily available which help tuning blown engine.

So what it comes down to is making a normally aspirated tune believe it can manage a boosted engine. Some tuners are very good at it. I suggest logging AFR using a WBO2 using intake vacuum(MAP) and rpm as the chart properties. You will see the AFR all over the place as you go from CL to OL to PE cross over 85 kpa(approximate value for the start of PE) then crossover 0 psi(100kpa) and into boost. Fuel control over 1 bar (atmospheric) is also critical so you don't go lean or rich and damage the engine or cat.

Real time tuners can help correct the anomalies; however, I do not think there are any available for Chrysler. Using a logged WB chart you could assign a BEN(base efficiency number) to each cell and correct and fine tune AFR over the operating range while in OL. You would have to disable CL operation to get this base AF tune. I am a CMR tuner and I feel there is a lot to gain but it will take some effort. It's too bad one tune does not work for everyone like with a NA engine.

Sorry for the ramble.

fredrok

Excellent and accurate post. When we started putting SCs on Mustangs back in the late 80s, we had tuning fits a plenty with the stock SD systems. Fortunately, in 89 Ford introduced MAF systems in all subsequent Mustangs and things exploded. For race applications, SD was still preferred for many of the "race only" rides but you couldn't beat the MAF conversion and subsequent aftermarket parts availability for everyday driving. Of course the EEC-IV Ford engine management systems were "DOS" simple compared to Chrysler's latest, but it would sure be nice to have it cracked and MAF conversions introduced.

11rubiwannabe

WOW ! More than I could understand .....but I believe you...so what it comes down to is I should get rid of the JEEP.....now abf find some other V8 equipped vehicle...and leave it stock

AdvJeep

The wideband o2 is a success! I will keep my numbers private until Jon has looked at them. I definitely think I'm running a little bit rich but we shall see.

I had my battery unplugged for the install and it seemed to fix a bit of the surging but it is still there on the flats and inclines.

Thanks robbi for the input as well! Great rant it explains a ton!

fourxfourjeep

My question is which has the advantage... Roots style or the twin screw style?

The root pushes the air out and around the lobes whereas the twin screw pushes it between the lobes.

11rubiwannabe

Isny the roots style same as s twin screw? If you mean centrifugal I e turbo style like a ripp...the the ripp style makes more HP but at a higher rpm....for me I don't drive much higher than 3500/4000 rpm at the most..I like the twin screw pull off of idle.

AdvJeep

Today was the first time taking the sprintex and my jeep up to 5k rpm and holy cow it just keeps pulling!! I believe the tune is almost 100% now! No surging and my fuel eco is becoming much better I can hit 18mpg on the highway now!

Jon is absolutely amazing!! He is definitely making the blower kick ass!!

fourxfourjeep

They are very different Below is a Twin Screw Similar to the Sprintex:



This is a roots:


the difference is how they route the air, the roots forces the air out and around towards the housing where the Twin screw routes air in inward between the screws and compresses the air.

roots air direction:


Twin Screw air direction: