Piggyback computers

[dwg86]

I am thinking about installing a piggyback computer on my stroked Jeep. I don't know how much power I can gain by using one. I have never used or done any kind of tuning with a piggyback computer. For those out there that have used them...any opinions on what to by?(unichip, split second psc-001, or have my stock computer reprogammed). I still need to install a AFR gauge. I want to get one that I can download data from, any suggestions on what AFR guage to run?

If I see the fuel trims are good after I install the AFR gauge using the stock computer, would I benefit from adding a piggyback computer? I am really showing my ignorance when it comes to computer controlled fuel injection systems.

Oh yeah, info on my Jeep...2003 Wrangler, 5 speed, and I need to pass smog test every year.

[Cheromaniac]

The amount of power you'd gain from a piggyback computer will depend on how far away from optimum your stock computer's fuel and timing tables are. Since the '00+ computers are less adaptable to performance mods than earlier generations, I'd say you probably have quite a bit of power left under the table.
I suggest you contact Bennie at Hesco about the Unichip. It won't be cheap but the results will be worth it.

[SilverXJ]

Power? Not sure, but it will help your engine. Using stock injectors, you are most likely running lean on WOT (Open loop). Or if using larger injectors you could be running rich. I run an Apexi and a mod'd PCM. The PCM was sent off to be reprogrammed and I told them to remove fuel from the program in open loop. They removed some but wasn't enough. If I didn't already have the Apexi I would have sent it back for a reprogram. However, I still like it for all the other things the re program did.

As for the Apexi, its basically a MAP adjuster with multiple points, and it does work well to bring the AFR to where I want it. It only makes changes in open loop, and I don't know of anything that would make the PCM change from 14.7:1 afr in closed loop.

As for AFR gauge I am using a WEGO II by Daytona sensors. It has an LCD display and data logging. Their software is a bit rudimentry but it works. The design is ok, nothing pretty. Probably going to make a housing in the future so it looks a bit better. Their new WEGO looks even worse, but still, functional and a good price for one with data logging.

[gradon]

If you have the $, get Innovate's LM-2 wideband o2/obd2 scanner/datalogger. That'll let you know where your fuel trims are and also what the afrs are in WOT. With that data you can use a psc1, apexi, or like to zero the fuel trims and get WOT down to 12.5:1.

[SilverXJ]

That'll let you know where your fuel trims are

How does it do that? Connect to the OBD II port?

Really, I'm not sure of recommending the Apexi unless you can pick one up cheap. While it is really a "rice" device it does work. It gives you an extra gauges for TPS, MAP, RPM, etc. You can adjust it on the fly, and it has two programs, but the whole thing about it being geared toward imports. It does work though. Its just personal preference. And its just more crap to put on the dash. Like the AFR gauge, GPS, CB, switches and radar detector isn't enough to clutter up the interior.

[dwg86]

I am using the cobra EV6 24# injectors. Everything seems OK with the stock computer. My plugs are a very light tan color(stock champion plugs), and I have 3500 miles on my stroker now. But I will know more when I install an AFR gauge. Has anyone used an AEM uego AFR gauge part #30-4100? Would this be a good gauge to run?

[SilverXJ]

It look pretty decent, but I can't find if it has internal data logging or not. "Serial data stream included for output of AFR (RS 232)" from AEM's site makes me think it doesn't.

[dwg86]

It look pretty decent, but I can't find if it has internal data logging or not. "Serial data stream included for output of AFR (RS 232)" from AEM's site makes me think it doesn't.

Forgive me Silver, but when it comes to computers,I am really dumb. Do I need "internal data logging"? Does internal data logging mean that I can read whats going right there at the gauge without needing a computer to see?

[SilverXJ]

No, the AEM gauge looks like you need to hook it up to an external data logger, i.e. a second device that records the data, which you would still need to down load that data from on a computer. I would verify that with them though.

When I say internal data logging, I mean the device itself records the data (usually has an RPM and TPS input as well), and has a serial or USB port to hook the PC up to in order to down load that data.

Personally I wouldn't buy a unit with out data logging. I prefer to watch the road under a full throttle accell instead of the wide band. Also, the AFR can change so quickly that its hard to watch the screen for that and record where the RPM and throttle is. This way I can come out of my apartment, go about 1/8 mile down to the road to a nice hill, put the pedal down, then coast down the other side of the hill for cool down flip a U, full throttle up the hill, coast down the other side and pull into my parking where I pull the data off the wideband and see where the AFR ratio is. Adjust the Apexi accordingly and do another run in the future to see what you changed.

[dwg86]

Power? Not sure, but it will help your engine. Using stock injectors, you are most likely running lean on WOT (Open loop). Or if using larger injectors you could be running rich. I run an Apexi and a mod'd PCM. The PCM was sent off to be reprogrammed and I told them to remove fuel from the program in open loop. They removed some but wasn't enough. If I didn't already have the Apexi I would have sent it back for a reprogram. However, I still like it for all the other things the re program did.

As for the Apexi, its basically a MAP adjuster with multiple points, and it does work well to bring the AFR to where I want it. It only makes changes in open loop, and I don't know of anything that would make the PCM change from 14.7:1 afr in closed loop.

As for AFR gauge I am using a WEGO II by Daytona sensors. It has an LCD display and data logging. Their software is a bit rudimentry but it works. The design is ok, nothing pretty. Probably going to make a housing in the future so it looks a bit better. Their new WEGO looks even worse, but still, functional and a good price for one with data logging.

OK, so with running a piggyback computer you can only change the afr in open loop? From what little information I can find, to change settings in closed loop you need to reprogram the ECM. http://www.kennebell.net/techinfo/dodge ... 40tech.pdf (see SPEED DENSITY SYSTEM). If anyone has a web site, or book I can read to learn more, please let me know.

[Plechtan]

This is simple, if you have more air, you need more fuel. I have seen pictures of the Hesco supercharger installations, It looks like they have a special fuel pressure regulator that is controlled by the boost, more boost , higher fuel pressure, more fuel into the motor. This approach does not involve reprogramming the PCM.

[gradon]

For example, on my 96 obd2 setup, I was running a split second psc1-002 and the lm2 wideband/datalogger. When looking at the fuel trims in closed loop, the pcm was adding 10-15% more fuel to maintain the 14.7:1afr. I would tweak the psc1 until it was 0% fuel trims long and short, so the pcm didn't have to compensate much at all. Open loop started about 3000-3100 with medium throttle input. I blended a few cells(psc software) once open loop started to get the 14.7:1 down to 12.5:1(best power on NA). Now on my setup, I wanted the 2500-3000 to be richer than 14.7:1(like 13.5:1) because this is where the peak torque is building/cylinder compression is high, but I can't override the pcm(unless I pull the cts and keep it in open loop mode). This is where you need someone to program the obd2 pcm or have a piggy-back that can intercept the signal, tweak it, and tell the pcm what it wants to see.

[SilverXJ]

I don't know of any company that will do the reprogram on the closed loop on Jeep PCMs.

[DaveJeep]

You can tune WJs with SCT Pro Racer Package. I have it for my WJ. Not sure about the OBD2 ZJ & XJs though. Get the PCM code off the PCM and email SCT support and they will tell you if they can offer a tuning solution.