So, Im driving with HP Tuners hooked up and watching how my car looks on the computer. Im running a turbo 2002 WS6 with a built 370ci. Ive got the boost turned all the way down. I make a pass then look at the data. My MAP is pegged at 105 KBA on the lap top. What does that mean. Do I need a three bar MAP sensor. Also my injectors are reading at 94% duty cycle at the end of each gear. I am a little rich, should I lower the injector duty cycle. Am also sitting at 17 degrees timing. Thanks guys.

 

when you say "boost turned all the way down" how much is that (psi)?

 

Define rich.
You probably need more injector, that duty cycle is too high unless your way rich and can lean it out a lot.
Assuming you are running a 1 bar MAP sensor and using the MAF your MAP is reading exactly what it should. It can't read any higher than atmospheric pressure.

You can go to a 2 or 3 bar MAP and ditch the MAF if you go to a 2 or 3 bar OS.

 

I don't want to come across as a dick, but you need to understand what you're looking at.....because everone's in the same boat when they begin to learn tuning.

#1 Of course your MAP is pegged at 105kPA. 100kPA is atmospheric pressure which equals 0PSI. 105 is only about 0.4lbs of boost. I can hit that consostently on my car NA with the current cam setup.

If you're running less than 14PSI, you only need a 2-bar MAP sensor (which reads to 1-bar, or 2x ambient pressure (which is 14.7PSI). If you are making boost above 14PSI, then go for the 3-bar sensor.

When you change the sensor (the 2-bar is the Cobalt SS sonsor), you also need to change the operating system. HP Tuners allows for this, but the car will now be Speed Density and not MAF, which isn't bad (I run Speed Density now NA and also ran it boosted), but you need to know the pos/cons of doing so.

#2 Injector duty cycle of 94% is more than you want to see, but isn't a sign the engine will explode. Ideal duty cycle is 80% to leave room for the injectors to add fuel under extreme circumstances.

What size injectors are you running? For FI I'm a big proponent of going straight to 60lb injectors. Might have some dissenters on this statement, but I'd rather have 60's running at 60% than 42's running at 90%. You can tune the pulsewidth as needed, but at WOT it should be the stock 1.227. Shortening the pulse width at low RPM will allow for running bigger injectors with lees boost/ NA. I still run my 60's with the NA motor. total overkill, but I already had them and reduced the pulse width to 1.1x to compensate. Car runs happily with those changes.

#3 What's your definition of rich? For FI "ideal" is 11.6 to 1 AFR. I personally feel this leaves no room for error and ran my car at 11.1 AFR. I did bump the timing as a result to 20 degrees total advance (17 at the torque peak). This was on a STS @ 5PSI. If I was running more boost I would have decreased the timing accordingly.

Less than 11.1 AFR is rich and can be compensated for by adjusting the Ve tables (increasing the value richens theAFR while decreasing the value in a given cell leans the AFR.) Over 11.6AFR is lean. Whatever your value is, go from there.

I will add that if you are running MAF mode or 1bar SD, you WILL notice that the car runs richer in 1st and 2nd gear than 3rd-6th. The reason is that as the gear ratio decreases (higher gears), the load on the engine increases, thus more fuel is required. So, dyno tuning 1bar MAF or SD (where the car's in 4th gear) will show as a rich condition in 1st-3rd. The only way to compensate for this is to use a 2 or 3bar SD setup where you can calculate the Ve table for "part boost" conditions (105-210kPA depending on the final boost setting.)

I think without knowing anything else that 17 degrees timing is correct........


This is an elementary overview. If you have Q's feel free to PM me. I'm a test pilot by trade, but have tuned a couple FI cars (mine included) and if nothing else can steer you in the right direction to get the answers you need.

Take care.

 

Well, Im running the Siemans 60# injectors. I have the manual boost controller turned all the way down. Not sure what PSI that is on the STS kit. The car has the MAF removed and was tuned for spped density.

 

you might want to get a boost gauge on there

 

Unless the spring was changed, the F-body STS wastegate is set to 5PSI. With the manual boost controller "all the way down, that equals the wastegate spring.

On a 370 you should not be seeing 60lb injectors at 94% duty cycle at 5PSI. +1 on getting an accurate boost reading. I was running 58% injector duty cycle with 60's/heads/cam on my 346ci STS @5PSI with a speed density tune.

 

smart guy hes got this one covered ^^^^^^^^

 

Some basic questions to get out up-front...

Running rich? Are you running a wideband and logging it? How much too rich?

How much boost?

Are you logging knock retard? Was there any?

Do you have an intercooler? What was the IAT (intake air temp)?

To put a finer point on it, what is it are you wanting help with? Is it about everything (logging/scanning and turbo tuning in general)? Or just about what map sensor you need? Or validation of the three numbers you gave us -- afr, timing, and kpa numbers? Well actually we don't have a afr number yet. Or something else?

 

im at 8 lbs of boost. no knock retard during the passes, no, im not running a wide band but i was lookin at the o2 sensors and they were both in the 850 and 900 range.

 

get a wideband, you should not use narrow band o2's for tuning, especially for FI.

 

Ok guys. I installed the new Walbro 255 and the idle fuel pressure is sitting at 55lbs. Which is better then the 45lbs it was before the pump change. Anyways I just took the car and made a pass. The boost never got above 8psi. But the fuel pressure dropped to 35lbs. And according to HP Tuners that was datalogging the pass, my injector duty cycle sky rocketed to 112%. What now, I need a second fuel pump...???? Bigger injectors...????

 

Reading the posts you have a couple things going on.

#1. The O2 sensors are supposed to read 850-900+ at WOT. That tells you the car is actually transitioning to WOT the way it's supposed to. The O2's cycle in closed loop during idle and part throttle, but at WOT they "max out" and place the car into open loop. The fueling calculations are then a product of the Ve table modified by the PE (power enrichment) table.

In short, the car could be running lean as a$$ or rich as hell. You need a wideband to accurately log the AFR.

#2. You're losing fuel pressure, which causes the injectors to lean out. You stated that you're running one 255GPH pump but the pressure is 55PSI. Pressure should be 58PSI. You can run higer rate injectors, but high impedence injectors only go up to 72lbs or so. Ater that you need to convert to a BigStuff3 or similiar system to run larger low impedence injectors.

Suggestion......check your fuel filter to ensure it's not clogged. Also, if able, check the pump and ensure that the pick-up tube is secured properly. Racetronix pumps use a replacement factory connection tube, while Walboro's use rubber tubing if I believe correctly. The latter sometimes works loose from the pump and thus doesn't deliver the specified volume of fuel.

Good luck.

 

I dont know if I read over this being said but you have to set you scanner up for it to read boost properly. The car could be tuned sd with a 2-3 bar map, but if you dont have the scanner set-up it will max at 105 kpa.

To fix this you go to the table display with the car disconnected and delete the map sensor pid, then you right click on an open box, insert> engine>airflow>manifold absolute pressure (kpa). Also make sure that you are not logging any pid's that you do not need like the maf sensor.

Get a wideband, stock sensors and not accurate enough!

 

There are two Walbro 255 lph pumps. One is designed to flow that much while also maintaining high pressure, and costs a few dollars more than the other one. It should say "high pressure" in the description somewhere. I don't have part numbers handy though.

55-58 psi sounds about right. You could check the voltage at the pump and see how short of 13.8volts you get with the car running/charging, and decide if you want to run a kit to add volts if you're only seeing 10-12 volts back there. I have a KB boost-a-pump on mine, dialed up just enough to see right at 14v.

Definitely need a wideband. 850 is most likely too lean. But it's just guesswork trying to use a narrowband.

I run a single Walbro pump feeding a set of the 60 lb injectors. They run around 80% duty cycle at 500-540 hp on 10-11 psi to 6500 rpms. Pressure is stable throughout the run.

17 degrees of timing, if you're not seeing any KR, is probably ok. If the IAT's start climbing you may want to pull a little more out. Depends on how long you stay in boost and if you're intercooled or not.