Help in tuning a stock 03 GT w/ Vortch V2 Supercharger

[03SCGT]

This is a carryover from this thread:

http://www.stangnet.com/mustang-forums/799014-testing-fuel-pressure.html#post8057232

Basically, I have Vortech V2 supercharger setup that came with larger injectors(38lbs), a piggyback chip, a 80mm MAF housing that you put the stock MAF guts into and 255gph fuel pump. I bought the car recently with the whole setup already installed. Everything looks new, even the motor. The car has full length headers, no cats, and a BBK intake and larger throttle body. The injectors that came with the kit(38's) had been swapped out with 42 lb injectors.

On the dyno, the car was running dangerously lean, too lean to even make a full pass. Using a handheld scanner, the computed fuel pressure values always stay around 40lbs and do not drop off at full throttle.

I can't seem to find anything else really helpful on this scanner(Actron cp9185) to help watch for a lean condition. I was told to watch the MAF sensor readings to see if they pegged at 5V early which would show that the MAF wasn't up to snuff for the setup. Unfortunately, the MAF value that the scanner shows is something listed as LB/M and is going up to around 14-15 while accelerating through 2nd gear.

At this point I really don't know what to do. I have confirmed with Vortech that the piggyback chip installed in the car is the correct one for the kit. The only real unknown at this point is whether or not the 255gph pump from the kit was installed. I'm figuring it was since everything else from the kit appears to be installed correctly.

My first question for anyone who knows these Vortech kits would be this:

Should the computed Fuel Pressure values(from the fuel pressure sensor) go UP under full throttle ?

I tested a stock 03 GT and it stayed around 40 lbs all the time, even under full throttle. When I tested an 03 Cobra(factory supercharged), the fuel pressure values jumped from 40lbs to 60lbs immediately under full throttle.

 

[bhuff30]

If the air meter is showing 14-15 lb/min at higher rpms, then you found the problem. As an approximation, moving 1lb/min makes 10hp, so 14-15lbs/min is equal to around 140-150hp. If this reading is at low to mid range rpm, then it is reasonable, but if it is under boost or at higher rpms then, it is way too low. You would likely be seeing 30+lbs/min at high rpms in boost.

Have you tried cleaning the air meter with cleaner? It may have collected some debris or oil. It may also just be a very poorly designed setup. I've never heard of putting the OE guts inside a larger air meter. It may require a different calibration curve, which would just require some dyno time and someone knowledgable about tuning.

Anyway, stop driving it if it is lean, and definately don't go WOT. A single lean event can cost you an engine.

On the fuel pressure side... it will vary with the pressure in the intake manifold. If you are idling, it will be around 30psi. At WOT without boost, it should be around 40psi. If you are running 10psi, then it should be 50psi. For each psi of boost, your fuel pressure should be 1psi higher. Long as the fuel pressure can keep up with the boost pressure, then the fuel pump is not the issue.

 

[03SCGT]

I wasn't hitting it too hard and didn't go WOT. I didn't want to push the car too hard since I know it's lean. The dyno operator said it was probably safe to hit the gas a little in 1st and 2nd but not to try to full throttle it through 3rd gear.

Question: How does the computer know how to richen up the fuel mixture at the rate of 1psi per lb of supercharger boost ? It's possible that could be my problem, something not wired/vacuum hosed correctly.

Let me ask you this, if I 3/4 throttle the car in 2nd gear from say 2000-5000 rpm, what should I expect to see on the MAF LB/M reading ?

 

[the98stang]

either buy a full tuning program like SCT pro racer or have a a shop tune it before the engine goes BOOM

 

[trinity_gt]

I wasn't hitting it too hard and didn't go WOT. I didn't want to push the car too hard since I know it's lean. The dyno operator said it was probably safe to hit the gas a little in 1st and 2nd but not to try to full throttle it through 3rd gear.

I wouldn't gas it in any gear until the fuel issue is sorted.

Question: How does the computer know how to richen up the fuel mixture at the rate of 1psi per lb of supercharger boost ? It's possible that could be my problem, something not wired/vacuum hosed correctly.

It doesn't have to. It knows the mass of air entering from the MAF and computes the fuel shot required knowing the flow rate of the injectors across a roughly 40psi pressure drop. As long as the MAF isn't saturated (i.e. its output is pegged and it's unable to report any more airflow to the PCM) the PCM is good to go.

The system maintains a pressure drop across the fuel injectors "automatically" by using the feedback from the fuel rail pressure sensor which is referenced to the manifold pressure. The PCM adjusts the fuel pump driver module (FPDM) duty cycle to ensure a 40psi drop across the injectors (fuel rail pressure minus manifold pressure.)

Do you have any information about the fuel pump? Keep in mind that the 03 GT has a returnless system Fuel pressure is not adjusted at the rails by a pressure regulator but rather by varying the duty cycle of the voltage applied to the fuel pump. Not all pumps are compatible with this system. Can I assume that the pump that's in there now is the Focus SVT pump you mention in the other thread?

Let me ask you this, if I 3/4 throttle the car in 2nd gear from say 2000-5000 rpm, what should I expect to see on the MAF LB/M reading ?

Rough guess from 1st principles:

Air density is ~0.071lbs/ft^3 at 100oF. At 3500RPM, the 4.6 (281 cid) is ideally displacing 3500/2*281/1728 or 284.6 ft^3/min. Assuming a 100% VE that's about 0.071*284.6 or 20.2 lbs/min. I don't know what the actual, real-world VE would be under boost, at that RPM and air temp, throttle angle etc so consider 20.2 as a "nominal" value: YMMV.

 

[wmburns]

Here is my question. It is my understanding that the Votech system uses the stock MAF in a larger tube. Because the tube is larger, a 5 volt output would mean more air is actually flowing.

Does the Vortech tune re-index/modify the values reported by the MAF? In other words, is the 15 LB/M actually 15 LB/M or is it still referenced to the stock diameter intake tube?

If it is referenced to the stock tube, then the actual air flow would be much greater.

Suggestion, graph the raw PID value from the MAF. Your scanner will do that. The trick is to find the number for the parameter we are interested in.

A better PID to go after is the O2 sensors and Fuel trim.

 

[MustangLife]

Bro, you don't want to be running a piggyback mail order chip on a s/c application. Its good you've had the tools to find out the lean condition prior to banging thru the gears. Makes me think about all the poor guys that didn't have a way to test fuel pressure, lean/rich conditions, etc because if you didn't take it to the dyno and you redlined it you probaly would have blown the engine up. But you of course know that.

I will get the car to a dyno/educated tuner and get a perfect tune in it. Its a good time time of year because a winter tune is a good thing vs just a standard tune. Not sure about your climate. Definately do this, not only are you gonna get max hp/torque out of your setup but your gonna be safe.

Josh

 

[wmburns]

In other posts, the OP stated that the piggy back chip was supplied by Vortech. So one would expect that the tune should be in the around the ball park.

 

[Rickyll7]

This is a carryover from this thread:

http://www.stangnet.com/mustang-forums/799014-testing-fuel-pressure.html#post8057232

Basically, I have Vortech V2 supercharger setup that came with larger injectors(38lbs), a piggyback chip, a 80mm MAF housing that you put the stock MAF guts into and 255gph fuel pump. I bought the car recently with the whole setup already installed. Everything looks new, even the motor. The car has full length headers, no cats, and a BBK intake and larger throttle body. The injectors that came with the kit(38's) had been swapped out with 42 lb injectors.

On the dyno, the car was running dangerously lean, too lean to even make a full pass. Using a handheld scanner, the computed fuel pressure values always stay around 40lbs and do not drop off at full throttle.

I can't seem to find anything else really helpful on this scanner(Actron cp9185) to help watch for a lean condition. I was told to watch the MAF sensor readings to see if they pegged at 5V early which would show that the MAF wasn't up to snuff for the setup. Unfortunately, the MAF value that the scanner shows is something listed as LB/M and is going up to around 14-15 while accelerating through 2nd gear.

At this point I really don't know what to do. I have confirmed with Vortech that the piggyback chip installed in the car is the correct one for the kit. The only real unknown at this point is whether or not the 255gph pump from the kit was installed. I'm figuring it was since everything else from the kit appears to be installed correctly.

My first question for anyone who knows these Vortech kits would be this:

Should the computed Fuel Pressure values(from the fuel pressure sensor) go UP under full throttle ?

I tested a stock 03 GT and it stayed around 40 lbs all the time, even under full throttle. When I tested an 03 Cobra(factory supercharged), the fuel pressure values jumped from 40lbs to 60lbs immediately under full throttle.

It depends on what the scanner is telling you. Rail pressure or pressure across the injectors.

The pressure across the injectors should be about 40psi all the time (unless it was tuned to be different from the stock fuel pressure which is also fine if it was done propperly)

The rail pressure should be 40 psi (again, unless it was tuned to be otherwise) +manifold pressure (gauge pressure). So at 10 psi of boost, the rail pressure at that time should be 50 psi. Under vacuum (idle or cruising) the rail pressure will be less than 40 psi by an amount equal to atmospheric pressure minus manifold pressure (actual pressure, not guage pressure). Typicaly in the 30s during idle and cruise.

It sounds like your scanner is telling you the pressure across the injectors and 40 psi is perfect (if the tune was made for stock fuel pressure which it may be). But, if your computer thinks the manifold pressure is always atmospheric pressure because the reference line is missing, cut, or routed incorectly, then the 40 psi that your scanner and computer thinks is across the injectors is not actualy there. This would cause exactly what you are experiencing, a climbing A/F ratio with rpm at WOT. You have a centri blower so your boost climbs with rpm steadily and so will your A/F ratio if your computer is wrong about fuel pressure.

Check your manifold pressure reference line.

 

[Rickyll7]

03SCGT,

Any updates?

 

[03SCGT]

Update:

I took the wheelwell all apart and pulled the MAF. The correct Vortech supplied larger housing was definitely installed. It is now 83mm on the inlet and 90mm going into the Vortech supplied big K&N cone filter. I took the MAF apart and cleaned it with electronics cleaner.

We took the car out over the weekend and did some careful data logging. We also hooked up the scanner to a 2003 Supercharged Cobra just to see what the FRPS reading would be on the Cobra as it boosted up. The Cobra uses the exact same FRPS as my 2003 GT. The Cobra idled at 40psi but as soon as we hit the gas the FP immediately jumped up over 50 psi and up close to 60 under WOT.

We then hooked the scanner up to my car. The first thing we did was some careful 80-90% throttle in 2nd gear without getting too crazy. We now see the MAF readings go up and over 40 so I'd say the MAF is just fine. The FP readings were always around 40 psi at idle and cruising speeds. If I was in 2nd gear at say 2000 rpm and hit the gas to say 80% throttle, the FP would go up a bit to about 43 psi and then drop back down to 37-40 as the rpms went up.

If my system should act like a 2003 Cobra, I would expect the FP readings to rise with boost. Right now the car is supposed to have a Walbro 255 gph pump that came with the Vortech kit. I'm just about ready to yank the tank and install the Focus SVT 255gph pump I got and change the filter. What do you guys think ? I'm getting conflicting info from "the experts" as to whether or not my FP reading should go up under boost like the 2003 Cobra does.

 

[wmburns]

I don’t see any conflict with what you have been told. It depends upon the car, the tune and the strategy used by the tuner.

It has been mentioned several times that a custom tune can change how the PCM behaves. Some tuners can for all practical purposes turn a MAF PCM into a speed density strategy in the interest of getting maximum horse power. With this comes some of the trade offs (needing retune when changes are made ect).

If it is basically a STOCK tune, the delta fuel rail pressure should be around 40 PSI for a GT Mustang. Note, that FRP of 37 at WOT may be getting marginal. That is after all a 10% reduction in fuel pressure.

Note, the absolute pressure DOES raise at WOT. If you need to see it for yourself, measure the fuel pressure via the rail test port. I am positive the atmospheric fuel pressure will rise above 40 PSI at WOT.

The comparison between the two cars can not be made until the differences are understood. For example, if the method of measuring fuel pressure (delta vs. atmospheric) is not consistent, comparison is meaningless. Further if the Cobra is using a highly modified tuning strategy where as Votech is using the stock strategy, the behaviors will be different.

Even in bone stock trim, the 2003-2004 Cobra is a very different car. It has a completely different PCM (much faster/stronger to enable a more complex engine management strategy to work). Which is important when trying to draw comparisons between the two cars. Votech designed their kit to work with the stock GT PCM.

Congratulations on learning how to use the data logger. IMO, you are getting closer to how to diagnose the problem. If I may push the point, take it further. The data logging needs to look at the effective air fuel ratio as well as the FRP, TPS, load, MAF, ect. This should be over laid graphed in a time line. Only then will a true picture of what is happening emerge.

Another point. The post did not say what units were reported by the MAF. 40 what? 40 lb/min? 40 micro volts? 40 volts?

Also, how can replacing a Walbro 255 GPH pump with a Focus SVT 255 GPH pump make any difference? Aren't they both are 255 GPH? So unless the base operating pressure of the two pumps are different, one may conclude they will give nearly the same results.

 

[Rickyll7]

Before you change the pump, call vortech and ask them if it will work with their tune.

 

[03SCGT]

Testing

Got some time to do some testing today with the scanner. The first thing I learned was that the Actron scanner takes PID readings at approx. each 1.1 seconds which makes it really difficult when you're trying to accelerate thru only 2nd gear. It would be nice if the scanner took readings every .1 seconds.

Anyway, these readings may be helpful but like I said, when you're only getting readings every 1.1 seconds, it's really hard to tell much. I'm afraid to do it all the way through 3rd gear, higher chance of hurting something.

This is what I set the scanner to record:
1. TPS %
2. RPMs
3. Load %
4. MAF lb/m
5. Vehicle Speed
6. Fuel Pressure
7. O2 Sensor Bank 1, Sensor 1
8. O2 Sensor Bank 2, Sensor 1
9. Time in seconds

I could not find a PID for A/F ratio.

I'm going to try to type this out in a meaningful format, hope you can get an idea from this. 0-5 is each frame set of readings, approx. 1.1 seconds apart

Frm TPS% RPM Load% MAF Spd FP O2-1 02-2 Time

0 22 1642 22.7 2.01 16 39 .755 .725 0
1 25.5 2524 89.8 16.64 29 39 .460 .350 1.3
2 89.4 3680 99.6 31.02 43 34 .950 .885 2.4
3 86.3 6178 96.1 40.25 60 38 .595 .495 3.5
4 62.7 4417 89.4 27.42 57 32 .935 .910 4.7
5 22.4 4573 5.9 10.46 68 39 .590 .620 5.8

Frame 0 is right before hitting the gas. I didn't want to get too crazy, just accelerate through 2nd gear at almost full throttle and then a little of 3rd gear at 2/3rd throttle.

Frame 1 is just starting to hit the gas
Frame 2 is almost full throttle in 2nd, 3680 rpm
Frame 3 is the top of 2nd gear, tires started spinning at high rpm, 6178 rpm
Frame 4 is probably just shifting into 3rd gear, just starting to hit the gas
Frame 5 is letting off the gas in 3rd, didn't want to go too crazy.

 

[wmburns]

Am I reading frame 4 correctly? 32 PSI fuel rail pressure? That is down 8 PSI. Mostly likely just at/after max boost. IMO, the fuel pump maxing out bears a closer look.

Will the scanner take more frequent scans if fewer PID's?

I am about to suggest something real strange. Can you put a larger pulley and lower the boost slightly? Trying to see if a small decrease in boost might enable to fuel/air system to catch up. The resulting package may be overall better (think of it this way, a working motor is faster everyday than a broken motor).

 

[03SCGT]

Don't have a way to do a bigger pulley but I might try the less PID's thing to see if I can get more readings than just every 1.1 seconds.

At this point I'm just about ready to yank the fuel tank and change out the pump and filter.

 

[Rickyll7]

Call vortech about that fuel pump you have. You won't find a pid for a/f because mustangs don't have a wide band sensor. You cannot do this without a wide band o2 sensor, better datalogging equipment like sct and a tuning software like sct pro racer and some serious tuning knowledge. I recommend you get a profesional dyno tune.

 

[wmburns]

Try logging the injector pulse width and raw MAF. We still haven't confirmed if the MAF is maxing out.

We also need to know what long term and short term fuel trim is doing. Esp when going from idle to higher RPM. I think some of this logging could be done in the driveway with no load.

Note, some of the O2 values show rich (> 0.450). Lean is < 0.450. Some of the readings are almost Stoichiometric (0.460).

Rickyll7 is correct. The O2 sensors can not display AF ratio. Only rich or lean. A wideband O2 is needed for a numerical AF ratio.

Rickyll7, the Fuel pressure values are data logged from the PCM. The PCM would only care about a manifold referenced FP. Nothing else would make sense. If the manifold vacuum reference was disconnected, the FP would stay a constant 40 PSI from idle to WOT. However the AF ratio would go from crazy rich at idle to crazy lean at WOT.

One way to confirm is to log the long term and short term fuel trim values. The switch from rich to lean will be plainly visible in the trim values.

Another way to confirm is to monitor the FP via the test port. The FP should be less than 40PSI at idle and climb above 40PSI as boost builds. If the reference was disconnected, the test port FP would stay at 40 PSI.