Stock FPR

[oe_tuner]

Hello.

I was wonering if any of you have tried to apply a boost reference to your stock FPR?

Right now I am only applying vacuum to it, but I was considering trying to get a rising rate out of it by applying a boost signal to it.
My concern is that I could damage the FPR, or that it would hold too much pressure.

The reason for this is that I have had to jack up all the settings on my PCPro to get my car to not run lean under boost. I have replaced everything on my fuel system (new OE FPR, new Walbro 190HP, new fuel filter, swapped 5th injector with a buddy's) and it would still run way lean under boost. The car runs like a top other wise, so I do not think that the other 4 injectors are messed up. My car only has 57K on it.
Have any of you had to make dramatic changes to the PCPro setting on your 94-97's? I will try to gather my final settings this week and post them.

Thanks!

[Tom @ Fast Forward]

Seems like a few bad E-Cool PC-Pros lately and possibly a bad 5th injector connector or two. Have you confirmed thet E-Cool is working? Set it to max and take an AF reading. Then set it to min and take a reading and let me know how it goes. Are you lean across the board or just at the lower RPMs?

[magnamx-5]

Just how lean are you? 12-1?

[BlownMX5]

oe tuner,

I have a '94 that is similar to your '95 - OE fpr, 190 lph pump, etc. My car runs lean under boost too, but only above about 6200 RPMs. At 5000 to 5500, it's actually very rich, then goes lean. I have it set rich just trying to get it to stay rich enough at redline. Tom and I have deduced that it may be my stock fuel rail at fault. But, so that I'm ready for future enhancements :), I got an E-Cool instead, thinking that the 5th injector can take up the slack of my four stock injectors and relieving the constriction of the stock fuel rail. Unfortunately I haven't been able to get it to work at all yet. First I rechecked all of my connections and made sure I had continuity. Then, I did the test that Tom suggested (max rich then max lean) and I didn't get any difference in my a/f. I then tried blowing into the vacuum line at the E-Cool PC-Pro while the engine was idling. This should fool the PC-Pro into thinking it was under boost causing it to fire the injector and the engine should stall. It didn't. So I soldered a couple of wires on to a 12v bulb and hooked it to the injector connector, to see if it lights up under boost. Now a word of caution here - I used a two-filament bulb (regular tail light-type bulb) where one filament is about 26 watts and the other is about 8 watts. You can't really tell which is which when you look at the base of the bulb - there are just two terminals there. Of course I picked the 26 watt circuit and I may have damaged my E-Cool PC-Pro because of it. Anyway, I never was able to get the bulb to light up and in fact as soon as I go into boost, now all of the lights on the E-Cool PC-Pro go OUT, and stay out until I turn the key off and back on. This is why we think I may have killed it by connecting it to the high-wattage filament on that bulb. Tom is being most gracious and is sending me another PC-Pro so we'll see how that goes later this week.

Anyway, you might try some of these other tests and if you do the light bulb test make sure you use a bulb with low wattage.

Pat.

[bogey]

I have the Split Second controller for the 5th injector, which has 4 injector leads. I connected an LED to on of the extra lead sets. When I hit boost, the LED glows brighter and brighter based on the RPM.

[oe_tuner]

OK, so here are my settings:
Main injectors:
Green - 5
Yellow - 6/7
Red - 3
Yellow/Blue & Red/Blue - 6/7

E-Cool - 6

With this set up I can keep me at safe air fuel ratios, but does go a but rich right around 5,500 RPM. It seems like it could probably use a little more fuel on the green setting still.
Tom, I will e-mail you my zeitronic's downloads.

Does anyone have an answer to my original question about putting boost to the stock FPR?

Thanks!

[Gord96BRG]

The stock FPR and fuel system expects boost to the FPR. The purpose of the fuel pressure regulator is to ensure that the pressure differential between the fuel rail and the intake manifold is constant, so that the injectors are flowing the same amount of fuel for the same pulse width whether under light vacuum, strong vacuum, or boost. If you increase the pressure in the manifold, you MUST increase the pressure in the fuel rail.

Say you're cruising at light throttle, intake manifold is at -10" mercury ( = ~-7psi?). Fuel rail pressure is ~40psi, therefore pressure across the injectors is 40 - (-7) = 47psi from the rail to the manifold, through the injector.

Now you're at medium throttle, boost gauge at 0 (vacuum gauge at 0 also ;) ). The FPR uses the vacuum signal to adjust your fuel pressure to 47 psi, net pressure across the injector is 47 - 0 = 47psi (same as at light throttle).

Next, step on it, and you're showing 10 psi boost. The FPR needs to raise the fuel rail pressure to 57psi to keep the injector pressure differential constant - 57 psi in the rail, minus 10psi boost in the manifold, equals 47 psi differential. If the FPR did not see the boost signal, it would not raise the fuel pressure beyond 47 psi, and you'd only have a 37psi pressure differential for the injectors to operate - the net result would be less pressure for your injectors, so LESS fuel injected per pulse when under boost!

(Take it to the extreme - if you were running 47 psi boost and the FPR didn't see the boost signal, you'd end up with manifold pressure equal to the 0 boost fuel pressure of 47 psi, you'd get NO fuel injected at all, even though the fuel injectors could be open 100% of the time!)

[oe_tuner]

Interesting.

So, are you running boost to the stock FPR? <-- original unanswered question.

I know some kits supply a boost reference regulator, but I thought that was to supplement fuel like what the PCPro is doing in Tom's kit.
Tom's instructions for the kit say to run the hose to the VDB which only sees vacuum.

[Tom @ Fast Forward]

Gord,

I didn't think it should see boost. So far, we have not had a top end fuel issue with the PC-Pros that I am aware of. It would be easy to tee off of the 1/4" nose to the bypass valve. We did try it last week at the syno with Dave's 94 and didn't notice any real difference? We had a fuel pressure gauge on the line and didn't really see it change much more than what the manual says. It was ~38PSI at vacuum and ~43 with atmospheric or ~45 with boost.

[chuckerants]

I have the Split Second controller for the 5th injector, which has 4 injector leads. I connected an LED to on of the extra lead sets. When I hit boost, the LED glows brighter and brighter based on the RPM.

Hey that's a cool idea! I've been getting really into LEDs lately. So far, I've replaced the in-cabin light bulbs with white LEDs, I've also placed a blue LED for when the WI is activated and another RED blicking LED for when I'm getting low on water.

Maybe I'll use the spare green LED I have for the 5th injector. :)

[Gord96BRG]

Interesting.

So, are you running boost to the stock FPR? <-- original unanswered question.

Well, yes... BUT...

I'm using the FM Link standalone ECU on my 96, with vacuum/boost to the FPR (tee'd off the line to the MAP sensor and boost gauge). FM's instructions are to use that signal for the FPR, and their reasons are as I wrote.

I recall Tom's instructions have just vacuum going to the FPR, and if that's how the PC-Pro is calibrated, then that's how it should be run. For a Link, perhaps for other standalones, the FPR should see boost as well as vacuum.

[BlownMX5]

Well, I haven't changed the vacuum source for my FPR, so I'm sure it's seeing boost. I've measured fuel pressure and it's about 35 psi at idle and 51 at WOT, 5000+ RPMs. I make about 7 psi of boost. Could this be a problem for me? I go lean above 6300 RPMs.

Pat.

[oe_tuner]

Gord,

So far, we have not had a top end fuel issue with the PC-Pros that I am aware of. We had a fuel pressure gauge on the line and didn't really see it change much more than what the manual says. It was ~38PSI at vacuum and ~43 with atmospheric or ~45 with boost.

Well, we know I have been struggling with huge lean conditions since I got my car running.
As you can see I have really had to jack up the settings on my PCPro to get it to run safely. Like I said earlier, I have replaced everything in the fuel system. I have tested the e-cool PCPro and injector several times. I am pretty confident that it is working. When I put about 8psi to the boost tube on the e-cool PCPro, the engine stumbles, and if I hold pressure for a few seconds, the car sounds like it will stall. I did the same thing with the main injector controller and the engine almost immediately stalls.

So, if I am not supposed to put boost to the stock FPR, then I am not sure why I have had to modify your base setings so much.

I have an electric fuel pressure gauge in my car, and I see about the same pressure as you stated above (except I have not applied boost to the FPR yet).

Also, I still think the car is not as quick as it should be. Don't get me wrong, it is faster than it was, but just not the tire ripping, neck wrenching power others talk about. Today I was behind a newer Accord V6 6MT, and I was barely able to keep up with it getting on the highway. That is not much to brag about. Has anyone with a base kit on a 94-97 taken a trip down the 1/4 mile? What kind of ET's should I expect? There is a track close to my work. I am thinking of going to one of the Friday test and tune sessions.

Are there any ideas or opinions about my situation? Am I just expecting too much for the $4,000+ I spent installing this kit?
I definitely need to schedule some time on a dyno. I just want the car to be in the best running condition I can get before I go, so I do not spend all my time trying to tune a car that is not functioning correctly.

Thanks for everyone's input.

[Tom @ Fast Forward]

Not sure about your coils but, if they are weak, misfires will show up lean on your A/F even though you have ample fuel. It will also lose WHP.

Time for a compression and leak down test. Send me your dyno file when you have it so I can see what the lines look like.

[oe_tuner]

Any way I can test my coils? I have already spent a lot of time and money fixing a fuel system that was not broken.
I really do not want to spend money on new coils if I do not need to.
I will check the compression when I have time.
The car only has 57,000 miles on it and I know the previous owners took good care of it.

[oe_tuner]

I have finally gotten around to testing seveal items on my car to rule out the possibility of poor performing parts.
I tested the coils per the Enthusiast Handbook and they tested perfect.
I tested the plug wires and they all have low resistance and look good.
I checked the compression in each cylinder. They all read between 160-170 psi. I am very pleased with those compression results.
I also check the plugs. They are all gapped perfectly at 0.30
The insulators do look awefully clean though.
http://new.photos.yahoo.com/oe_tuner/photo/294928804422322831/1
http://new.photos.yahoo.com/oe_tuner/photo/294928804422322844/0
At this point I believe that everything is functioning correctly on the car.

So, I took the car out for another run with the datalogger. The air fuel ratios still seem off to me.
I am running the settings in the beginning of this post. The concern that I have is that I cannot keep a consistent air fuel ratio, and I do not have the adjustment resolution to fix it. The car has a rich dip at 5600, and starts to lean out towards 6500.
http://new.photos.yahoo.com/oe_tuner/album/576460762388283646/photo/294928804422344510/19
I also ran the car from a stop to 6500 all in 2nd gear and got an interesting AF curve. It seems like it runs lean at full throttle and partial boost/lower RPMS. It looks like the PC Pro does not really kick in until 6.5psi.
http://new.photos.yahoo.com/oe_tuner/album/576460762388283646/photo/294928804422329249/18

Tom, have you had a chance to reconfrm the base setting considering the fuel pressure differences between the 94-97 and the 99-up models? Do I need to run an adjustable FPR to get my AF ratios in order?
How does the PC Pro add fuel relative to boost? Any idea why I have the strange AF curve in the 2nd gear pull graph?

Is anyone else having the same concerns with thier base FFS 94-97 system with the e-cool and PCPro?

Next step will be the dyno.

[mx3jmcb]

Seems like i'm also getting the infamous 6200rpm "lean out" problem on my 94.

At first i thought i was rich but after logging some highway pulls from 3-4th gear i found out i was reaching AF's up to 14.5 at 7000rpm.

Basically the engine will stay rich, safe and stable until i reach around 6-6200rpm where it quickly leans out.

I spoke to Tom about clamping the return lines to verify if the problem was the fpr so ill be checking that out but i have a feeling we have the same sort of problem.

I also have a tip in problem where the engine will studder slightly when i keep stable throttle and the engine goes from vacuum to boost. Kinda annoying....anyways, hopefully we can work out these glitches without it costing too much.

I have the 110mm pulley and from past experience....i have a feeling my car right now would run mid 14 second passes at the 1/4, nothing crazy but obviously much quicker than stock.

[Tom @ Fast Forward]

What bothers me with those graphs is the up turn at thehigher RPM/Boost. When we saw that here, it was indicative of a weak FPR. As Jean said, I recommended that he cklamp the return line and make a run. It is a lot easier and safer at the dyno but a quick run up in evem second gear would tell you whether it was OK or not. If I recall, on Dave's 97 it looked similar (12.7 or so) and, when we clamped the return line we could make it way richer than 12:1 all the way. Normally that up turn at the high load means you are running out of fuel. Either a fuel pump or FPR. The FPR needs to be able to close tight to make the pressure increase. If it has been only closing part way for 13 years the spring might even have memory.

If you clamp the return line and have richer A/F that could be the reason.

[mx3jmcb]

Here's a log of a 3rd gear pull to about 7100rpm.

http://img221.imageshack.us/img221/6126/untitled1bm9.jpg

You can see the AF start to climb at around 5500rpm climbing over 12.5 at around 6000rpm.....by the time im at 7000rpm, the AF's are around 14.5.

Kinda scary...what brings my attention is the slope of the curve as it suddenly stops decreasing and starts rising.

[oe_tuner]

Tom,

It bothers me too.
As I mentioned in my earlier posts, I have replaced everything in my fuel system except the steel lines. I have tried 3 different FPRs, all giving the same results. I have an Walbor 190L HP Pump too.
Clamping the return line will not prove anything to me other than that maybe us M1 guys need an adjustable FPR to meet the fuel demands of the supercharger. As we discussed on the phone, there is a big difference in the base fuel pressures between the M1 and M2's. Also, as you mention elseware, the M1 injectors have less capacity. Did you ever get a chance to double check the PC Pro settings for the M1 considering the fuel pressure difference between the M1 & M2's to be sure the M1 settings were appropriate? I know we had discussed this last time we talked, but I have not heard anything since.
I am going to the dyno next Thursday to see how the car is running and hopefully dial in the tuning a bit more. My concern is that with my current tune, I am rich at 5500 but up turning toward lean by 6500 an dI do not have enough tuning resolution to fix this. I would prefer to spend my time and money at the dyno knowing that I have all the approporiate hardware. Do you think that the M1's need an adjustable FPR to increase the overall fuel capacity of the system? Should we be using a boost refernece on the FPR to add a little more fuel pressure at the top end? If so, I was hoping to get an FPR installed before I spend time at the dyno.

Any feedback would be appreciated. Thanks.

[Tom @ Fast Forward]

If you want to send me the cards and harness, I will open up the adjustment so you can put in more fuel. The thing I don't understand is that the E-Cool is the equivalent of two of the stock injectors and it should be able to flow a LOT of fuel if the main injectors don't.

The FPR should be able to stop the return fuel if needed, to keep the pressure up. That is the only reason I thought it should be tried. Just curious if it made a difference.

[mx3jmcb]

After testing the clamping of the fuel return line trick, seems like the ecu properly manages the extra pressure in the fuel rail and idles normally.

I only did 2nd gear pulls but i can already see a difference....the response of the engine is considerably better and it runs very rich in the below 5500rpm (around 10), when i let go of the gas at around 7000rpm, the AF's were right around 12.

Without the clamping of the fuel line, i get AF of close to 14 at around the same revs.

Initial thoughts suggest that 94-97's need an ajustable FPR and higher rail pressures...

[Tom @ Fast Forward]

Theoretically, the stock FPR should be able to clamp the return line if working properly and it sees the pressure drop off.

[Tom @ Fast Forward]

There's always one of these?

http://cgi.ebay.com/ebaymotors/Red-Universal-Fuel-Pressure-Regulator-240SX-350Z-G35-TT_W0QQitemZ230145778267QQihZ013QQcategoryZ33674QQ rdZ1QQcmdZViewItem

Take the stock one off and replace it with something like this. Adjustable from 20PSI to 140PSI and $25.