Baseline Dyno runs and some fuel/charging problems

[datsunmotorsports]

I finally got the car on and made two runs at it with little to no tune. The engine is RB25DET from a 94 R33. I built my own 3" mandrel bent exhaust system with a Gredy straight through tip muffler. The only other non-stock/OE part is the intercooler. I have a million miles of pipe with multiple, excessive bends to fit a NPR Isuzu box truck intercooler.

So after 5 cars cut in line and pulled up on the Dyno I finally got in at the last minute and made my two runs. Both runs ran far to lean and started to pop at about 6400 rpm.I actually walked away from this with a smile on my face because I realized that I made more power than I had expected to. Also I know there is much more power waiting to be unlocked in a tune session.



So that's exciting to me.

Now on to find out why Im so lean still.

Two problems have come to my attention about my RB Z.

-First problem is the Alternator.At least I believe. I have tested the alternator with a micro VAT. I have 42AMPs max output. I have some AC ripple that has concerned me, but I am un-sure the total allowable amount. If I remember correctly I have about 3 volts AC ripple in the system. That doesnt seem to be my issue however. Any time that a load is placed on electrical system it drastically affects the rest of the system. Turn signals for instance can be heard affecting the fuel pump pitch. That cant be correct. I have removed the 74 voltage regulator and connected the signal wire from the RB alternator to the battery with an inline resistor that keeps my max voltage below 13.8V. Without the resistor the voltage will spike 15.6V at times and Ive seen it get really close to 16V. I thought I may have had a ground issue but I bought a new battery ground cable and made several other ground straps for the engine. Why is my electrical system being loaded so heavily? Isnt the alternator suppose to regulate spikes and draws on the system?

-Second Problem Fuel.As you can see by my other recent post with my Dyno results I have a fuel starvation issue. I have been through 90% of my fuel system. So Im at a loss for an explanation. So let me explain what Ive done.I was using the original R33 pump for my car at first. I placed the pump in the tank with the pickup sock in the center of the tank. 1/4 tank left and any heavy accel/turning and the pickup would go dry. I still have this problem. However I dyno'd the car with a FULL tank. About 3-4 weeks ago I replaced the R33 pump with a used, but known good, Infiniti Q45 pump. These pumps have a tendency to go out and become loud (often referred to as "Angry Bees")and chances are if you pull one at a wrecking yard you will get a bad one. I pulled mine from a driving parts car I had a few years back. My logic was that the VH45DE is rated at 279ft/Lbs and about the same HP, the RB has a very similar rating so the pump should be a very qualified replacement part. Im using a brand new fuel filter for the R33.Ive checked the FPR and the fuel rail for problems. My fuel lines have been checked as well and they are both flowing fine. I have a APEXi SAFC II installed and it isnt having much of an effect on the AFR at high load.My guess is that the Q45 pump has gone bad while it sat on my self at home and that it may be time to upgrade the pump and tank. Id like to verify the problem before I go and spend money on new parts that may not fix my problem.

Anyone have input for testing the situation with-out an O-scope.EDIT: Also I noted that the R33 Sending unit/fuel pump carrier as a very small orifice for the return line. approx 1/8" or so. Its really small. Ive been researching info about the fuel pump modulator and pin 104. Currently I am running a 5/16" return line.

Thanks for input

[DrifterProdigy85]

Hanna at Best1Tuning told me the RB runs around a 12.5 AFR at 43psi fuel pressure. He recommended to bump the fuel pressure up to get the AFR down to a more suitable area. How much fuel pressure are you running?

[Shocker]

eliminate issues and just get a 255, not the best pump but it works, never starve it.

Next thing I bet your coil packs or ignitior is on its way out. Wrap them up with some electrical tape and see if that helps, there are a few threads on this if you look.

[datsunmotorsports]

It apears the stock pump was PWM through pin 104 and the system was almost a returnless one with that small return orifice on the tank sending unit cap.

As for my Fuel Pressure, for some reason I thought I had done that test along with a flow test. I remember doing the flow test and the results, but I cannot recall the pressure test. I will have to check it again.

As for the Coils I have a S2 without the ignitor pack. The ignitors are built into each coil. I have actually already gone through and replaced them after testing them. 5 of the 6 failed testing. I bought used ones through Ricky at RAW BROKERAGE. One of the used ones he sent me also failed testing, but they were all used and I got them for a very good price so eh. I actually made one of those posts you refer to. BTW electrical tape pretty much wont help you. I ended up coating them in epoxy and liquid electrical tape.

[Shocker]

If you dont swap the pumps make sure/rewire it so its seeing at least 13.5-14.0 volts.

Pressure should be 43 psi vac off base. Should see 53-54 max PSI if your running 10-11 psi boost with that base. If the pressure is dropped off I'd suspect either bad reg, bad pump or clogged fuel filter. If reg is new, I'd lean towards pump, or filter. You should be running z32 or equivlent filter.

5/16" return is fine, dont worry about that.

[Coolwhip]

Hey Ray, are those coils you speak of the ones from February? I'm gonna check and see if I have any other oem S2 coils in stock to help you out.

[maryjane]

walbro is cheap insurance

[datsunmotorsports]

Well I am running a stock setup. I was running the R33 fuel pump for a while then I switched to the Q45 as it has the same rating as the stock R33 Rb25det pump.

I put a restriction in the return line to make it 4mm(Still larger than stock R33). Then I threw it on the 5 gas analyzer and started to tune. I have a APEXi SAFC II to tune with along with Nissan Data Scan on a lap top. So I tuned the low end in at no load(I know but whatever). I pulled off the silencer on the back at this point. Then back on the Dyno today to make 13 more runs. I'll try to give you a walk through on my tune and runs.

The first 2 or 3 runs were total crud. Something like 140hp. We didnt bother printing them out. We used them to start tuning the AFR in. The next few runs are here:



Closer with the AFR. Not really there yet though. I did make the most power I would all day at 252hp. But the miss is still there. So I called it quites for lunch and went down to the napa store and bought cheap copper core plugs that were rated 1 step colder than stock. Its pretty warm today and my car was heat soaking during lunch so we got back on the dyno and decided against cooling it down just to stay consistant with the ONE change at a time rule. During these runs we made some fine tuning after each pull. You can see the slight changes.Here is what I put down with the next 5 runs.



Very consistent if you ask me and good numbers for a mostly stock setup. There is still some power hidden in there. More tuning will have to be done.

I need to go out and buy a fuel pressure testing kit. I still havent checked the pressure. I need to do that. Im running stock boost during all these runs. The Fuel pump is seeing 14-14.8V at all times. I need an O-scope and low amp probe to verify its true condition though. I am running a brand new fuel filter from Nissan for the R33.

252hp max with a hickup... Engine is rated for 260hp at the flywheel... I must be doing something right. I couldnt tell you what, but I am. LOL
Modified by datsunmotorsports at 2:47 PM 7/1/2009

[Shocker]

Why are you even fussing with an SAFC to tune it? Sounds like your wasting time to me, and over complicating a pretty much stock rb25.

I laid down 277rwhp and 252ftlbs with 11 psi stock turbo, a POD filter, 3 inch turbo back, 255 pump, -6 NGK coppers and FMIC. Could have made a few more if I had advanced the timing a bit on the CAS, and added another lb or two. There have been ppl to make 300 with the same mods that I had on stock ECU. ToadX is one of them on here.

Remove the SAFC and sell it IMO.

EDIT forgot to mention those numbers were on a Dynojet as well.

[datsunmotorsports]

The truth is Im compensating for not having enough control over the fuel system at this point. That is why all of this is a base-line tune. I have other stuff on the way. I have a upper plenum with a front mount TB for less intercooler piping in the works and I am doing my best to reconstruct the stock fuel system and find the best way to modify it to fit my needs. I wont believe just strapping a Walbro or whatever in there will simply fix the fuel system. It wasnt designed to work that way. You might as well pull off the OE FPR at that point and get a really expensive one. Im not there yet. I may get there in the near future, but I want to prove it on the dyno if I can. Then I will have proof to post that X mod works and its the best way to go as per my results.

[Shocker]

You should have a 5/16" feed, you already said you have a 5/16" return. If that is the case that is EXACTLY what my s13 has. A walbro 255 intank, along with a nismo FPR was all it takes, trust me. For the price of both is cheaper than an SAFC.

[datsunmotorsports]

My car has a 5/16" return and feed line. The Skyline has a similar size line. I think it may be a 9mm feed and a 9mm return or within a MM. The piece of information you are missing my friend is that you have never seen inside the stock Skyline tank and fuel pump housing unit. I have the fuel pump housing unit. Inside the R33 unit I have the feed line remains 8-9mm all the way through the pump into the huge soak pickup. HOWEVER the return line is a different story. It is split. There is a pressure relief valve with a 4mm dump into the tank. I have no idea what that relief valve is set at. Then there is also a reed valve of sorts on the return line as well. This connects to the evap recirc system. Im unsure of the exact operation of this valve bu I have a feeling it helps draw in condensed or even saturated air into the tank with the return feed. The actual return line orifice sits under all this. The size of said orifice is about 2mm. Its tiny. The FSM refers to this collection of valves and orifices as a "Jet Pump".

So when people say to "just put the 255 pump on it" I have a hard time believing that that is any less fo a band aid than the SAFC. The system wasnt designed to be run with a 5/16" return to the tank. That much flow may be a problem. IN fact you can see that from my first dyno run. On a gas analyzer my car runs great. The moment you demand maximum fuel my AFR goes to hell. The car will drive totally normal around town and you can watch the AFR on my gauge stay an average of 13:1-13.5:1 while it swings. The only time it dips lean is at idle. It will sit at 21:1 at idle, but that is pretty normal from all the Nissans Ive tested. Its a good way to keep from burning fuel when you dont need to at idle.

That is about the end of what I know.

So, SHOCKER, where did you get those Fuel Pressure numbers? I have been digging through my FSM and cannot find numbers for the fuel pressure. If I could get some OEM numbers I could verify the situation and get everything under control or move on to looking for another problem.

I was actually searching around and found this read as well,http://www.240sxforums.com/for....htmlA little more in depth than just get X brand/model pump to fix your problem.a little R&D provided to us.

[datsunmotorsports]

...A walbro 255 intank, along with a nismo FPR was all it takes, trust me. For the price of both is cheaper than an SAFC.

BTW SAFC II = $100 slightly used with all original components/manual in box+$5 Velcro to stick it to my dash Whereas Walbro 255 is ebay-$89/summit$125Nismo FPR is $99-$125

So unless your thinking of the APEXi NEO or something else completely that statement is untrue.

[maryjane]

afcs blow!

[DrifterProdigy85]

Reason you dont want the AFC is because it modifies the MAF voltage to get the AFR it wants. Sounds well and good but when you modify the MAF voltage, you also change what timing cell the ECU is in under whatever load. AFC is definitly not something that should be used on our engines.

[datsunmotorsports]

Reason you dont want the AFC is because it modifies the MAF voltage to get the AFR it wants. Sounds well and good but when you modify the MAF voltage, you also change what timing cell the ECU is in under whatever load. AFC is definitly not something that should be used on our engines.

Here comes my question of Ignorance.

IF the AFC is modifying the Voltage to change Pulse width so it is corrected for the loading on the engine then isnt the timing map going to be corrected the same? So then the AFR would be more correct and the timing would indeed also be correct, right? Im under the impression that the two maps are directly correlated and that if the AFR is correct for the engine at any given load then the timing is also correct. What am I missing?

[DrifterProdigy85]

Our maps are setup by the MAF Voltage and RPM. When you apply load or throttle, it raises the MAF Voltage. The Timing is set for this perticular voltage and rpm. I dont know what the stock timing maps look like but lets say for example your going WOT @ 5500rpm and the Timing is setup for 20* and its doing a 12.0 AFR. You take the AFC and richen it 2% and it lowers the AFR down to 11.6. This has raised the MAF voltage to get the ECU to put in more fuel but what it also did was take it out of the 20* timing cell and put it into the new cell thats made for the higher voltage. Chances are if its gonna be using the timing from the higher voltage than you just retarded your timing from what it should have been in the first place. If your timing maps are setup accurately and all you need to do is fuel, you should just change fuel pressure and leave the timing out of it.

[Shocker]

Is the first run with the SAFC or w/o?

And the idea behind my statement on cheaper was new products not used. I'm trying to help you from my past experience with a stock/bolt on RB, no need to be a d!ck.

There is nothing wrong with a 5/16" fuel return, that should have nothing to do with your A/F unless its actually restricting fuel from making it to the tank quickly enough. This is not the case for you. I just looked through the FSM, and I see what your talking about with the pump. I still don't see the problem with a walbro being placed in there, its a very common pump for ppl to use. Even with a skyline tank.

[datsunmotorsports]

The first run was with the AFC installed already, but it was set to +-0% across the Hi and Lo Throttle positions.

I was looking around for a used Nismo FPR and came up with one, and it was being sold for $100. I couldnt find anything else. I didnt look for the pump used. I also called all the Local Nissan Dealers and could not find one in stock. Is everyone using the one with the a o-ring/screw on one side and a long barbed end on one side that looks like it wont fit my 25 fuel rail? Or is there one that fits without cutting the long tube off?

As for the Return line my line of thought wasnt that it was being to restrictive, its that it wasnt enough restrictive. The OE fuel pump is pulse width modulated. It appears that in stock form the Fuel system could be almost returnless with a PWM pump. Fuel Pressure can be controlled through a fixed orifice and modulating the pump off and on. Thats why the size of the orifice has my attention. If you put the Walbro on the OE system with an adjustable FPR it would still work properly because you would have set the pressure with a gauge and FPR. Pumps create Flow. Restrictions create pressure. My problem with the Walbro is that until I hunt down and find the real problem the Walbro is just a band aid. The more I read about the Walbro installs it does look like a good way to delete the entire OE fuel system. Im almost ready. I got my fuel pressure gauge in hand today so Ill have a look and see whats going on.

I see what your saying about the timing blocks. Retarding the timing though is safer than advanced timing, or even regular timing with AFRs like I had. Hopefully the pressure gauge will give me some insight as to what is going on in my fuel system and I can fix it. Otherwise I can think of no other thing to do than throw parts at it.

Sorry Im a very curious person and I cant always deal with the simple answer. Thanks for putting up with me.

[DrifterProdigy85]

Its gonna retard or advance depending on how the MAF Voltage is being changed. Retarding the timing isnt always safe. You can still get knock from not running enough timing. I know your trying to justify why you have it on there but electronically it shouldnt need to be there. Also you have an RB25 and your looking for a USED regulator. Stop being cheap and spend the 20 extra bucks on a new one. I think mines for a RB26 but it all fits. May need to run a new rubber fuel line but it works.

[Shocker]

I suspect you have a fuel issue for sure. Here is my graph with the mods I described for reference. Look at my a/f its pretty good.

[DrifterProdigy85]

How much fuel pressure are you running Shocker?

[datsunmotorsports]

...I know your trying to justify why you have it on there but electronically it shouldnt need to be there. Also you have an RB25 and your looking for a USED regulator. Stop being cheap and spend the 20 extra bucks on a new one.

AFC, point taken and I completely agree.

Not at all I just pointed out the used regulator for reference. I actually called all 3 of the dealerships in the area and checked with Nismoparts.com for availability of a new Nismo adjustable FPR. $100-$125 new isnt bad.

Shocker,

"277rwhp and 252ftlbs with 11 psi stock turbo, a POD filter, 3 inch turbo back, 255 pump, -6 NGK coppers and FMIC. Could have made a few more if I had advanced the timing a bit on the CAS, and added another lb or two. There have been ppl to make 300 with the same mods that I had on stock ECU."

I too am interested in your fuel pressure.

Tested the fuel pressureidle 40.5 psiremove vacuum =49psiTested at WOT loaded in second gear holds about 48psi

So not bad. Unfortunately

I read a couple posts about locating the MAF to close to the turbo inlet and messing with the MAF. My MAF is about 8" away from the turbo. Any chance its messing with my MAF? I cant think of anything else.

Modified by datsunmotorsports at 5:13 PM 7/4/2009
Modified by datsunmotorsports at 6:40 PM 7/4/2009

[DrifterProdigy85]

Damn, that lean with that much fuel pressure shouldnt be lean at all. Im wondering if the dyno wideband isnt reading accurately. What ive seen with the MAF from being too close to the turbo, is it will pick up some turbulance making it stumble and stall at idle. I havnt seen a change in AFR or anything like that. If your car idles and drives fine then i dont think thats a problem.

Also did you test your fuel pressure when the engine is warm or cold? What ive found with my SR and RB is that the fuel pressure will be high when cold and after a short drive after being warmed up the reading drops. Something doesnt look right from what you posted about your fuel pressures. If your at 49psi w/o vacuum, you should be at 60psi fuel at 11psi boost.

[datsunmotorsports]

Damn, that lean with that much fuel pressure shouldnt be lean at all. Im wondering if the dyno wideband isnt reading accurately...

Also did you test your fuel pressure when the engine is warm or cold? What ive found with my SR and RB is that the fuel pressure will be high when cold and after a short drive after being warmed up the reading drops. Something doesnt look right from what you posted about your fuel pressures. If your at 49psi w/o vacuum, you should be at 60psi fuel at 11psi boost.

Im positive the wideband is accurate. I ran 8 other vehicles on it and they were all where they were suppose to be and running great.

I did the test after it had warmed up for 10 min in 100 deg weather, but that doesnt always mean its at full operating temp.

My Boost is stock, which I believe is 7lbs. Shocker said he was running 11psi.

[DrifterProdigy85]

oh ok. Drive the car and get an exact fuel pressure reading w/o vacuum and then see what vacuum reads under 7lbs boost. That should eliminate if your FPR is the problem.

[Shocker]

43 psi vac off was my FP. Obviously w/o a reg you wont be able to adjust this. Before I had the reg on there I was mega rich, my car would pop and shoot flames constantly along with a nice cloud of black smoke. Car was definitely faster when I had the reg on there for it helped lean me out a bit.

A properly working reg should adjust for boost 1 psi, for every lb of boost built. Its a linear proportion.