Please help me tune my 3.2 Turbo Conversion

[lr172]

Following much of the greate advice/experience of the folks on this board, I have completed my 3.2 Turbo conversion and got it back on the road today. However, I am struggling to get the Fuel delivery working well.

I am setup with a Protomotive stage 1 chip and a BEGI FPR. I have a wide band and a boost gauge in the car and a fuel pressure gauge in the engine. My wastegate is set for .4 bar and the 38mm Tial wastegate doesn't seem to have a problem shedding the exhaust, as I have no creep (I was worried this wouldn't work).

My AFR readings are all over the place. I spent most of the day sputtering (too rich) on boost. I finally have a setting that seems to work ok, but is inconsistent. By Sputtering, I mean that it was the feeling of hitting a rev limiter, where very suddently that performance would fall off and make a type of sputtering in the cadence of the engine.

I have the BEGI set at about 65 PSI at atmosphere (no vacuum signal). I can't seem to get below 13 as I go through 0 on the boost gauge. I am afraid to turn it up much higher. I tried 70 PSI and that didn't seem to do much.

The key problem is that the AFR behavior will be different for each different RPM, gear, and part throttle/full throttle. For example, at the current setting, I will start going sputtering rich at about 5000 RPM or so (eventhough I had been on full boost since 4000). However, I won't get any sputtering as I accelerate through third or fourth gear.

In some situations, the AFR will hold low twelves at full boost through the RPM. In other situations, the AFR will keep getting richer as the RPMs increase. Still other cases where the AFR goes to the low 13's as the RPMs climb.

I am pulling my hair out trying to understand this. Some times it is very difficult to tell if the lean AFR's are really lean. I chased this all morning thinking I was lean and in fact was too rich. I finally remembered that at the point that you become too rich to fully combust, the AFR reads lean from all the unburnt oxygen in the exhaust due to incomplete combustion. The problem is that the AFR gauge picks this up before it starts sputtering and it appears that I am lean. I feel this may still be part of my problem.

Any guidance that you guys can provide, I would really appreciate. Does my onset setting seem too high or too low? The manual suggested 40-55 is the common range at atmospere.

Thanks,

Larry

[jbrinkley]

what brand of wide band and where are you measuring from?
have you thought that an air leak or bad connection in a hose somewhere could mess up the afr numbers?
and the fuel pressure..... idle about 35 or so?
can you see what the peak pressure is at full boost?


I would guess air leak somewhere, probably wouldn't have to be that big of a leak to mess up the driveability like that.
things that come to mind
all the air connections and signal lines that could really mess things up, including the begi signal.
afm issues possibly.
you could check the chip against the stock chip also. it will work for testing to rule it out.
get the car to run well first, idle mix and no leaks, don't push it too hard for testing. then work on the RRFPR and afr numbers
tons of little things could be going wrong.
got pictures of everything?

[mb911]

wow larry that was fast. I Would agree with jerry as well

[lr172]

Originally Posted by jbrinkley

what brand of wide band and where are you measuring from?
have you thought that an air leak or bad connection in a hose somewhere could mess up the afr numbers?
and the fuel pressure..... idle about 35 or so?
can you see what the peak pressure is at full boost?


I would guess air leak somewhere, probably wouldn't have to be that big of a leak to mess up the driveability like that.
things that come to mind
all the air connections and signal lines that could really mess things up, including the begi signal.
afm issues possibly.
you could check the chip against the stock chip also. it will work for testing to rule it out.
get the car to run well first, idle mix and no leaks, don't push it too hard for testing. then work on the RRFPR and afr numbers
tons of little things could be going wrong.
got pictures of everything?

I am using an AEM Wide band unit. The unit has seen a few hundred miles on my corvette and seems to work, but couldn never determine if fluctuations like this are the unit. It seems reliable. It is connected in the exhaust pipe between the turbo and the muffler. This is a 2.5" pipe about 6" long.

When you talk about an air leak messing up numbers, are you referring to the exhaust or intake (I assume exhaust)? I have re-done most of the vacuum tubing with new (including existing and begi FPRs. All the connetions are tie wrapped to assure that they stay on. THe engine shows a rock solid 15" at idle. I have never confirmed that my brake hose circuit does not leak, however, this posed no noticeable problem before. It is possible that I have very slight leaks in the exhaust flanges. I saw water drip out of a gasket on startup, but cannot feel any exhaust coming out. It is possible that my AFM flange gasket may not be perfect, but I figured this could do much other than keep me from reaching my boost.

My fuel pressure gauge is installed on the Begi input, so I cannot see pressure at idle. However, my problems are all under load. I did pinch off the final return line to confirm top pressure and I got about 100 PSI. I cannot get on boost in nuetral, so I cannot see peak pressure. This would take time, as I would have to order a pressure gauge for the cockpit.

Interestingly, I first ran the car with the Steve Wong chip just to make sure everything worked well before changing to the new chip. Right out of the box, it ran great with no problems. Then I put in the protomotive and had all of these problems. Then I went to the stock chip and it was better. Then back to the protomotive with all that I learned and was able to dial it to a more acceptable level.

Clearly there is something in the fuel maps that make the protomotive more picky. However, until I get a better understanding of what is going on, I am not going to say it is bad, just different. At only .4 BAR, do you think I would have any problems running on the stock chip? I figure with the conservative timing maps geared toward 87 octane, I should be safe if I am running 93. This would allow me to better eliminate the chip from the equation.

Jerry, can you tell me where your onset pressure is set at? The fuel PSI at idle with the signal disconnected from the BEGI (i.e. 0")?

Thanks so much for your help with this. I will go do some work on this today and report back. I'll snap some pic's as well.

Larry

[lr172]

Originally Posted by mb911

wow larry that was fast. I Would agree with jerry as well

Thanks Ben. Believe it or not that is with fabricatiing most of my parts (exhaust, flanges, holders, etc.) I wound up using a Magnaflow 2.5" same side in/out. It is slightly louder than the M&K that was on there before, but not much. It fit well and is all SS.

Larry

[jbrinkley]

ok.
I was referring to intake leak/ signal leak

your boost signal comes from the booster line? which is fine, just not the way I did it. I wanted a signal straight from the source.

pinching off the return line will show you the max pressure the fuel pump will reach, or expose weak points in the hoses, or pop the hoses.
*if you didn't pop a hose at 100 psi you're probably good*

if I went back and read the begi manual I'd know which line to remove to read the idle pressure. But I think removing the signal line your gauge will show the idle pressure?
without looking, the top screw increases idle pressure and the small brass screw on the side is the rate of gain. start with flat or unloaded settings on the begi and work your way up.
check to see that removing the signal line from the stock FPR raises the idle fuel pressure by a few psi. Do you have another gauge you can put on the rail in the test port?

All this is with no o2 sensor pugged in right?

It really is in the fueling probably because Todd uses the OEM regulator adjusted to his specs.
That chip isn't much different that the stock chip. Or put it this way, the stock chip is closer to the oem chip than to Steve's chip.

I think my idle pressure was around 35-37 and the pass though pressure, or zero(gauge) manifold pressure was only a few psi higher than that. with max pressure at 60 something. I'd have to go read past posts again. I'll go read some stuff today when I can.

It makes a huge difference being able to watch the fuel pressure rise on a gauge right next to a boost gauge.

Maybe thinking an air leak is the wrong direction to go on. more likely a fuel thing.

I know at cold start idle my afr s were in the 13's and ramped up to 14's at hot idle.

I think it makes sense to start at the bottom so to speak, with an idle of 880 at stock fuel pressure and good afm mix setting to acheive 14.5 +or-. get that straight with your chip and work your way up. Increasing the top screw on the begi slightly, and than the rising rate screw on the side. That thing is very sensitive.

[lr172]

Thanks for the input/guidance here.

I have my begi signal branched off the line feeding the stock FPR, which comes straight from the throttle body. I was just saying that I hadn't verified the integrity of the booster line.

Based upon your feedback, I think that I am way too rich. I have my onset (large hex screw at top) set to give me 60 PSI at 0" of vacuum (measured by pulling the signal line from the begi and observing fuel pressure (my pressure gauge is tapped at the input of the BEGI). Given that your max is 60 something at boost and I am starting at 60 PSI at 0" (onset of boost), I must be way too rich. I will put the stock chip back in and get it dialed in with that. I have a call into Todd to see why his chip is behaving so differently. The tech that I spoke with seemed to think they may have moved to a dual rate FPR in place of the rising rate. If that is the chip he sent me, that would explain a lot. Hopefully I won't knock too much at 5PSI with the stock chip.

I have my idle and no boost operation dialed in nicely. I have adjusted the idle mixture and speed (bridging B-C on test port) and the AFRs do what they should before getting on boost, including about 14.5 at idle.

I have done all of this with the 02 sensor connected (except the idle mixture setting). SHould I be running without the sensor?

I will put the old chip in and set the BEGI to an onset of 45 PSI and start tuning from there. If I can get that dialed in, I'll switch back to the Proto chip and see what happens.

I am pretty sure this is fuel delivery problem, as I run pretty well before boost. It certainly seems to be the right place to start anyways.

I'll report back with my progress.

Thanks again for your support here. Very much appreciated.

Larry

[jbrinkley]

I would run without it, that's just me though.

let us know what happens

[lr172]

Was able to get out at lunch for a little testing. Put in the stock chip and set the the atmosphere pressure at 45 PSI. Much better now. Pretty stable now and started to go rich around 5000 RPM. I will need to tweak the needle a bit more, but ran out of time.

Do I need the AFR at 12 as I come through 0" into boost or can it decrease down to 12 as I come up to the 5 PSI? Also, should I be doing all my testing at full throttle? I notice different results part throttle and full throttle.

Thanks,

Larry

[lr172]

Originally Posted by jbrinkley

I would run without it, that's just me though.

let us know what happens

Permanently or just for testing / tuning?

[911st]

Caution using the stock chip with boost. I suspect pulling back timming is the most significant differance. I am gussing you are using it without boost to get your FPR working.

Good luck with your build, can not wate to hear what you think about the power differance and hope to see some pictures.

[lr172]

I am using it with only .4 bar of boost. I use it only momentarily to test/dial in the FPR. I do not get on it or stay on boost for more than a few seconds. So far I have heard not a single knock or ping. I attribute this to the fact that I am still running quite rich. Also, I am running 93 octane and the original chip is set up for 86 or less (Porsche had to account for bad gas and such).

As soon as I stablizie the FPR settings, I'll go back to the Proto chip and see if I am still having problems.

I'll try to snap some pictures tonight.

Larry

[jbrinkley]

I wouldn't do any full throttle full boost with the stock chip.

at this point your car doesn't need the o2 sensor, I would ditch it altogether.

middle of the range is where the most pull back is in the proto chip. up top it goes almost back to a stock chip setting.
keep afr s in the mid low elevens.
you want it stay around there when you start doing your full throttle/boost runs.
once you pass through zero is when you want the afrs to come down and the fuel pressure to start rising....... it should, and will start rising right before you pass through that zero mark.

remember that until you start forcing air it's a regular car. with regular afrs

I'm not an expert, this is just my experience.
be careful

[911st]

I think the stock chip is pretty consertive anyway. Also you know you can pull timming back a bit with the fuel quality switch.

I am interested in how your AFR's look on the stock chip.

[lr172]

Ok. I have the BEGI set at 40 PSI at atmospheric, which should be just a bit above the specified range according to Bentley (33-39 PSI). I confirmed that the proto and OEM chips run similar and am not experiencing any real problems with the Proto. However, the AFR's under boost do seem a bit higher than with the OEM. I wonder if this could be due to the reduced timing.

Things are stable now, however, my AFRs are in the 13's until about 5000 RPM, where they quickly drop to about 10 (end of range for the AEM). If I adjust the needle to stay just above 10 at high RPMs, I am in the high 13's through the lower RPMs and I begin to be a bit rough there (thinking I may be too lean, though I can't hear knocking).

I keep thinking that my gauge may be slow to react, but is seems to bounce around quite a lot when not on boost, making me think it is not faulty.

Any ideas?

Larrry

[gsmith660]

I have seen wide band O2 sensor fluctuate wildly from noise on the supply voltage you might try a 4700 microfarad 35 volt capacitor on the supply voltage line to smooth out any noise coming in.

[lr172]

Got on the highway and was able to do more testing to isolate the behavior. I can dial it in so that I get around 12 AFR on the boost. After about 5 seconds (oberseved it at different RPMs, I think) it instantly drops to 10 (limit on AFR gauge). I mean one second it is 12.2 and the next fraction of a second it is 10. On the highway, I was able to stare at the gauge long enough to see it happen. The whole five seconds, I am pinned at 5 PSI and it doesn't change from there when it drops off the cliff. I was able to repeat this consistently, at many different settings on the needle. Also, it stays at 10 and doesn't come back unless I let off the gas (well, at least for the few seconds that I tried holding it there).

I am pretty convinced the regulator is bad. Can you guys think of any reason why this would be happening other than the regulator? Clearly the signals are good as my boost gauge is rock steady and it comes from a port directly next to the one for the fuel pressure regs (all three are on the same feed.

Thanks again for your support on this.

Larry

[gsmith660]

Originally Posted by gsmith660

I have seen wide band O2 sensor fluctuate wildly from noise on the supply voltage you might try a 4700 microfarad 35 volt capacitor on the supply voltage line to smooth out any noise coming in.

Ill say again if you haven't looked at this 911 electrical systems are notoriously noisey.

[Fast951]

If you are using the stock chip, you can pull some timing out via the FQS, position 4,5,6 and 7 all pull a bit less than 3deg timing. FQS is fuel quality switch, position #0 is the leftmost setting (counterclockwise).

Make sure your TPS is not malfunctioning when it's hot. If the DME is not getting the WOT signal it will not select the correct internal maps. To check the TPS you can use your voltmeter and connect it to the correct pin at the back of the DME plug (you need to remove the cover).

You can also check your AFM signal (0-5V range). DME #7 is AFM signal. Make sure the signal is fairly linear (no jumps in the voltage). Also make sure you are not maxing out the AFM where it is generating a maximum voltage before you hit your max RPM.

If you are running rich under boost, it can be a indication of a boost leak. The metered air is not making it to the head. However the DME already got the message from the AFM and is supplying the needed fuel, but the air never made it. A pressure test of the intake system will flush out any leak.

Using the factory chip is not a good test as it has a preset Max load value. When using forced induction, many variables must be handled correctly on the chip.

Not to sound bad, but a rising rate FPR is not a ideal solution Using larger injectors and modifying the DME chip to work with them is a much cleaner approach.

Good luck. Feel free to email if you need any help.

[911st]

Thinking out loud:

With a NA 3.2 the AFM dose stall just after about 5000rpm. However you might want to think of it in terms of HP as you are operating way outside the air flow expectation of the stock chip.

Thus, after about 180-190hp your AFM is pegged. If your build is going to pull about 325ft lbs that could be as early as 3500rpm.

This means that by 3500-4000rpm the chip is only using the RPM to determine injector duty cycle. That and the fuel pressure as determined by your FPR should then determine the amount of fuel you get.

I would suspect the stock chip may not be able to understand an AFM max air flow reading at 4k rpm. This might be an area where the two chips differ other than the ignition side.

You might try running no load (no boost, pulling a vac in the intake manifold) up through the RPM range to see if the chip is working in normal aspirated mode.

Again, I suspect you do most of your tunning past 4k on boost with the FPR/BEIG.

Note that many have experienced boost loss at the elbow between the AFM and the connection to the throttle plate area. I also believe the AFM can leak.

If you are loosing boost any place after the AFM, this would send your AFR's rich.

I think you can spray some brake cleaner near the injectors, near the AFM, and the elbo with the car at idle to see of you have a leak.

I would go back to the Proto chip as it should understand the air flow pattern of a boosted motor. You then just have to get the other attributes (boost & FPR calabration) to meet its expectation.

I am not and expert on this, just a couple of guesses.