Boost/AFR dyno graph - lean then rich

[Bodhi]

Gang -

This was originally posted on miata.net in the SC section, but the thread seems to be going downhill (sigh). Sorry for the cross-post, but I'd like a little input.

The car was dyno'd last week and we recorded the data shown on attached graph. It is concerning that the fuel enrichment doesn't start until ~4300 rpm and it runs lean up to that point. After 4300 rpm, it goes rich, eventually ending up in the low 10/high 9 range.

I talked to Tom about it and he said the PC-Pro will add fuel when it sees boost above the current atmospheric pressure. In this instance, that doesn't appear to be the case. It appears as though the PC-Pro is waiting to hit a configured value. The dyno is at 6000 ft above sea level, so that value would be 19psi (12.5 psi atmospheric pressure + 6.5 psi boost).

My experience driving the car on the street matches what is seen on the graph. It will ping at ~4000 rpm, but run smoothly in the upper RPMs.

Pertinent details:

* FFS coldside kit with 105mm pulley
* PC-Pro used for both main injectors & e-cool
* JR timing card
* AC removed
* wideband to be installed this weekend

It has also been verified that the mechanical (boost) connection to both the PC-Pros is good. I had a passenger report what she was seeing on the displays while I was watching the boost gauge. The lights displayed on each one of the controllers matched what I was seeing on the gauge.

[lds2002black]

If you go here http://www.fastforwardsuperchargers.com/forum/showthread.php?t=1077&page=14 to post #38 you can look at what my 2002 does. I think that also has my PC-Pro card settings on it also.

[lds2002black]

Here's one with the card settings http://www.fastforwardsuperchargers.com/forum/attachment.php?attachmentid=297&d=1205163808

[chuckerants]

When I'm at the dyno, the operator asked that I get it in 4th gear at 2500 RPMs and then go WOT until fuel cutoff (unless we heard pinging in which case we lifted). Is this how you did your dyno run?

[Bodhi]

Here's one with the card settings http://www.fastforwardsuperchargers.com/forum/attachment.php?attachmentid=297&d=1205163808

Cool. Thanks for the link.



Is this how you did your dyno run?


I'm not sure. The shop would let no one but the dyno operator run the vehicle.

[Tom @ Fast Forward]

We might have had a minor communication error. By lean, I mean 13:1. It can be at13:1 or richer up to ~4000 RPM. After that, it should be around 12:1. For the 94-97, even 11:1 is OK. It would be great to know what your fuel pressure was doing during that time. Also, can you post the settings on both cards?

As shipped, they should be

Main Card:

Green 0
Yellow 0
Red 0
Green/Blue 0
Yellow/Blue 4
Red/Blue 4

E-Cool:

Green 0
Yellow 0
Red 0
Green/Blue 4
Yellow/Blue 0

[Bodhi]

Tom -

I'm running with the settings you posted above. Also, if there were a breakdown in communication, it was probably on my end.


lds2002black - I read through your thread. The AFR "curve" that you have looks pretty darn good. I'm running a lower Y/B setting, yet ending up a good deal richer on the top end. Must be the altitude...

[Tom @ Fast Forward]

The PC-Pro is based on the stock ECU. It compensates for altitude and so does the PC-Pro. That correction should already be made.

Your fuel pressure regulator has a vacuum line to the fuel pressure solenoid and it has a line to the VDB. It would be of interest to see what happens if you skip the FPS and tie the FPR direct to the VDB. I wonder if the solenoid is delaying the increase in pressure from getting to the FPR?

In the meantime, you can add fuel to the green and to the red on the main card. Set them bothe to 3 or 4 and see if that doesn't bring on more fuel sooner.

[Bodhi]

It would be of interest to see what happens if you skip the FPS and tie the FPR direct to the VDB. I wonder if the solenoid is delaying the increase in pressure from getting to the FPR?


I already did that. My research found that the FPS exists to keep vapor lock from happening during hot re-starts. The popular consensus is that it's not really needed.


In the meantime, you can add fuel to the green and to the red on the main card. Set them bothe to 3 or 4 and see if that doesn't bring on more fuel sooner.

Did you mean to say 'add fuel to the green and yellow'? I'm already getting too much fuel in the red RPM zone.

[Tom @ Fast Forward]

Yes. My bad. Green and yellow. Do the green first. You may not need to add to the yellow.


Did you mean to say 'add fuel to the green and yellow'?

[FormerDatsun510Man]

I decided to post here instead since you will get actual help here :)

The PC Pro has a MAP sensor and this is calibrated to atmospheric any time you start the engine. It certainly uses this as part of the functions that add fuel.

In looking at your a/f it appears to me that two things are occurring. First, below 4300rpm at WOT it is staying in closed loop (i.e. ECU tries to maintain stoich 14.7:1 a/f ratio). Second, once the ECU is in open loop > 4300rpm, the a/f ratio gets progressively richer instead of staying relatively flat. For the closed loop problem, I recall in my tuner days that the '94-'97 Miata exhibited the behavior of staying in closed loop even at WOT while below ~ 3500-4000rpm unless you used an O2 clamp. The '99+ didn't show this behavior, for them they would go open loop with EITHER WOT or O2 clamp. The PC Pro that I have sets the TPS to read basically WOT as soon as anything >0 psi is seen by it. Perhaps the '94-'97 would do better with it reprogrammed for the O2 clamp function? I am just thinking out loud here, Tom knows better than me on this and I would go with his judgement. As far as the problem with the a/f ratio getting progressively rich, I am with Tom, I think something is up with the fuel pressure. If the fuel pressure is increasing further when in boost (as a function of boost) this could explain it.

I admit I am sort of pulling at straws here as I have no experience with the PC Pro and the '94-'97 models.

Bill

[Tom @ Fast Forward]

94-97 works about the same as the 99+ as far as the TPS goes.

Which reminds me, where is the TPS set for the switch? Some have found 0.020" works way better than the 0.050" as noted in the instructions. Does it idle OK?

[Tom @ Fast Forward]

After you add some fuel to the green and yellow (if needed), you can probably pull the Yellow/Blue back down a bit and kill the high end richness. A half light or maybe a whole light to the Y/B should do the trick. Might want to wait until you get the WideBand?

[Bodhi]

It idles at 850 rpm, smooth as a baby's...well, you know. ;) We set the TPS at 0.020.

[Bodhi]

...you can probably pull the Yellow/Blue back down a bit and kill the high end richness. A half light or maybe a whole light to the Y/B should do the trick. Might want to wait until you get the WideBand?

I'll wait until the WB is installed to pull any fuel.

[Bodhi]

Ok...I installed the WB & did a bunch of test runs. The e-cool PCPro was set to 4 G/B for all the runs.

main controller settings and results:

Y/B: 3
R/B: 3
green: 8
yellow: 8
red: 0

With the above, my AFR is ~12:1 from 3000-4000. After about 4200, it drops quickly, eventually hitting 10:1 at redline. This is what I'm currently running.

I tried setting the yellow light to 0. I would hold a 12:1 AFR until 3000 RPM. From 3000-4000 RPM, the AFR would rise slowly to the mid 13's. From 4000 to redline, it would fall slowly, eventually settling into the mid 10's.

I also tried running with the following:

Y/B: 2
R/B: 2
green: 8
yellow: 5
red: 0

Again, I would hold ~12.5:1 to 3000. From 3000-4000, AFRs would climb steadily to the high 13's/low 14's. From 4000 - redline, AFR's drop steadily, eventually hitting ~11.5:1 by redline. This would be a great baseline setting if it weren't for the lean spot from 3000-4000 rpm.

It seems like something is amiss. The car is running safely, but it feels like I'm using the G/Y/R fuel trim values to overcome something wonky with the primary fuel enrichment setting. There has to be a reason I'm going lean from 3000-4000 rpm.

Also, I'm consistently hitting 6psi at 4000 rpm. Max boost tops out at 8.5. Before saying those numbers are too low, remember that most of this testing is done at 8000 ft, so those values are to be expected.

Opinions?

[Tom @ Fast Forward]

Drop the E-Cool to G/B = 3 and see what happens. I think the main card should still be Y/B = 3 and R/B = 3. Just drop the E-Cool a bit. What you do with Green and yellow is somewhat immaterial. The 01-05 do similar. Typically ~13:1 below 3500RPM. That is no problem whatsoever. They do that stock as well. That is why the Green and Yellow are there, to trim that out if needed. Continually going richer is indicative of too much E-Cool.

This is what it looked like on the PO's car. Similar to yours. What I suggested to him was to add Green and Yellow as well. Without knowing what the fuel pressure is doing through all of this, it is hard to say difinitively.

http://www.fastforwardsuperchargers.com/Dynos/MN-Miata-Kentucky.jpg

[Bodhi]

Thanks for the input. I'll make the appropriate changes and report the results. I forgot to mention that I pulled 3 degrees of timing in the yellow zone as added protection. That may get added back in after the fueling is stabilized.

A new coil pack is on its way and I may order a replacement FPR. I know you have your doubts about the one that is on my car.

[Bodhi]

Tom -

I tried to add this to the above post, but it looks like the edit window expired. I broke down and ordered one of the ebay FPR units with the gauge. As you know, I have reservations about using those things, but experimental verification is a good thing, right?

If it helps my problem, I will issue a public mea culpa and buy you a Coke.
:grouphug:

[Tom @ Fast Forward]

It just sounds like fuel pressure is low and then steps high? The formula in the PC-Pro is a slope. No step changes.

[Bodhi]

Tom -

The barb that screws into the fuel rail to replace the FPR fitting is a 3/8 NPT x 3/8, correct?

[Tom @ Fast Forward]

The 90* barb for the end of the fuel rail is a 1/4" NPT x 5/16" barb. All fuel line in the Miata is 5/16".

1/4" NPT is about 3/8" diameter so it is confusing. The reason is because NPT is a measure of the internal hole (ID).

[Bodhi]

The 90* barb for the end of the fuel rail is a 1/4" NPT x 5/16" barb.

Cool. Thanks for the info.

[Bodhi]

I broke down and ordered one of the ebay FPR units with the gauge...

So, my FPR unit arrived and I installed it today only to find it didn't work. Regardless of how where I set the adjustment screw, there's no reading on the gauge. Zip...zero...nada. The needle doesn't even move. What a piece of crap. This further cements my opinion of flea-bay car parts.

I ordered a stock replacement FPR and will install it upon arrival. I am not a happy camper.

[Tom @ Fast Forward]

You loosened the lock nut on the top and adjusted the allen screw and nothing happened?

[Bodhi]

I loosened the lock nut and turned the adjustment screw. It made a difference in the fuel pressure. At first, the car was barely running and my AFR gauge was reading ~17:1. A couple turns on the adjustment screw smoothed out the idle and got me back to 14.7:1. Hence, the adjustment screw is doing it's job, but the gauge isn't reading any pressure.

The only thing I can think of is that the fuel lines going to the FPR barbs are swapped. There weren't any instructions and the barbs aren't marked IN/OUT, so I guessed. I'll swap the lines and see if it makes a difference.

[Bodhi]

The lines going to/from the FPR were wrong. I swapped them and got pressure on the gauge. I stand by my assesment that the unit is a piece of crap, but it works. I may shop around for a higher quality unit.

A test drive was in order. Cutting to the chase - Tom was right and I was wrong. :dupe: My lean tip-in is gone and the car no longer runs too lean from 3000-4000 RPM. I need to adjust the settings on the PC-Pro to accommodate the change, but that's not a big deal. Overall, it's much smoother both in and out of boost.

I owe Tom a Coke.

[Bodhi]

Well, the saga continues. ;) Upon firing up the car earlier this evening, I noticed the fuel pump was louder than usual. A casual inspection under the hood showed fuel pressure at ~75 psi. Try as I may, the fuel pressure wouldn't come down, regardless of which way I turned the adjustment screw on the FPR. So, I'm on the hunt for a FPR that doesn't suck. I may just run the factory replacement part until I can find a decent unit.

[Bodhi]

After doing a little research, it looks like the FPR that I bought is not the same one used by some of the other guys. Here's the link:

http://cgi.ebay.com/ebaymotors/_Racing-Parts__BLUE-FUEL-PRESSURE-REGULATOR-SUPRA-RX7-MIATA-MX5-86-98_W0QQitemZ270256514247QQadnZRacingQ20PartsQQadiZ 7583QQcmdZViewItem?hash=item270256514247&_trksid=p3756.m14.l1318

Don't buy this one. It is cheaply made, very difficult to adjust using a flathead screwdriver inserted into the top of the adjustment screw and broke about 30 minutes after being on the car. It cost $18 + $16 shipping, so at least I'm not out a bunch of money. The one Tom recommended is adjustable via an allen fitting at the top of the adjuster screw, but is no longer listed anywhere on e-bay. I found a nice unit with a gauge, but it's $100.

[Bodhi]

<cheesy announcer> ...but wait, there's more... </cheesy announcer>

Fast forward a couple days after the 75psi incident...

I go out to the garage and peak under the hood, noticing the pressure on the fuel gauge reads 0 psi. No biggie, the car's been sitting for a while. It cranks, fires, stumbles and dies. Okay...let's see what's going on. Closer examination of the FPR shows a crappy seal between the adjustment screw and body of the FPR. Also, there is a strong gas smell coming from the area of the FPR, which is mounted where my charcoal canister used to be. I had Kath crank it a couple times and noticed that the FP gauge reads ~37 psi when the motor is cranking. That pressure is held a couple seconds after cranking stops, but falls to 0. The fall to 0 psi is in a digital fashion, not gradual and is accompanied by a whooshing sound.

The above leads me to believe the FPR has completely gone to the big parts bin in the sky. I'm going to remove the gauge from the FPR and tap it in somewhere as it's been nice to know my fuel pressure.

My 190lph Walbro pump is in transit, too. :)

[Bodhi]

I replaced the crappy ebay FPR with a new stock unit and the car still won't turn over. It's getting both spark and fuel to the rail, so I'm not too sure what the problem is.

I was poking around under my dash looking for loose connections and I noticed something odd. There is a 6 port plug under the steering column on the left side. It has five wires. On my car, someone spliced in a section of wire between the harness and plug on two of the wires - red/black and black/white. Whoever did it used alligator clips and the splice on the red/black wire is degrading. The splice is held together by maybe 20% of the wire material and the plastic shrouding around the clip looks burnt, indicating a short. I put up a post on miata.net asking about that plug and my starting problem. Someone posted a couple suggestions for the starting problem, but I haven't heard anything about the plug. Any ideas?

[Tom @ Fast Forward]

Blk/WHT is always 12V power to something.

Red/BLK is usually used for the headlight control?

If you have fuel and spark, about the only thing left that could cause a no start, is spark timing or a lack of signal from the cam or crank sensors or lack of signal from the MAF.

[Bodhi]

It lives! Apparently, the problem was the broken wire. I disconnected it completely and the car remained dead when the key was inserted and turned to the on position.

I pulled out the crappy splice and soldered in the appropriate gauge wire. Even after the repair, it was still hesitant to fire up. When it finally did, it ran pig rich (10.x:1) at idle for a while. I took it on a nice, long 45 minute drive and the problem seemed to clear up. It's back to idling at stoich.

It runs well with the new FPR. I'm still getting a little lean tip in, but the lean spot from 3000-4000 is gone.

Something ugly did happen with the ebay FPR. I must have broken the seal between the vacuum and fuel chambers when I was monkeying around with the adjustment screw. When that happened, the car ingested a small amount of fuel into the vacuum line going to the FPR and the into VDB itself. There wasn't much in the line (< 1cc) and only a couple drops in the VDB. I blew that out by removing the vacuum lines except for one and blowing on it, pressurizing the VDB. There was a film of gas in the throttle body and the blower itself may have ingested a small amount. I'll keep my fingers crossed that no damage was done.

It was bad timing that the splice on that wire decided to go when I was monkeying around with the FPR. At least I learned a bunch of cool diagnostic procedures during this process.

As a final note, I don't blame the failure on anything having to do with the SC kit. Like I mentioned earlier, that splice was poorly done and it was a matter of time before it went.

[Tom @ Fast Forward]

A little fuel in the VDB will cause no harm. Fuel has a low vapor point and a little time idling at 18-20" Hg should vaporize and remove it all.

Yep. It's the little problems that cause the most harm. Like that black/white wire I had rub through the insulation and randomly touch the block. It just happened to be the 12V feed to one of the two ignition coils. Funny how well it runs after I fixed that. ;)