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Discussion Starter #1
I finally got my fuel psi sensor installed but I just realized that it may be wrong. I got a fuel rail adaptor with gauge and that didn’t work, kept leaking. Now I have the aem fuel filter bolt with adaptor going to a sending unit. I have an afpr which is why I wanted the fuel psi sensor but with it being at the fuel filter I’m guessing it won’t tell me anything about adjusted pressure after the afpr, correct?

2nd, What are the symptoms of leaking intake manifold gaskets on these cars? I’ve only dealt with it on ls1 and lq4 engines. I know cold weather can effect things. My afrs are going super rich on the highway. 10.0, then I let off and give it gas again and they will go to 13-14 for awhile then 10 again. I can adjust my arc2 and get it good but those settings won’t work on the street in traffic. I’m about to go slam these intake gaskets in, upper and lower and see if things improve. When boost leak testing at 22-24psi I can’t tell if I am hearing leaks through the intake gaskets or the crank case. It’s deep though.
 

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Discussion Starter #2
So I found the chart I was looking for



550 injectors state 466-624 with afpr
660 state 559-748 with afpr.

I think with my setup I’ve got too much injector. I can’t dial fuel pressure down enough for my fuel trim at idle to be right. Plus my low is always at 81. The current trim that is always changing is around 50. Maybe I’m confused on how to read that information though, I thought you’d want it around 100 for low mid and high. The value that’s always changing should probably be within 80-120? Or am I wrong?

I dont Know what else could be causing my low fuel trim to always be at 81. People say vac leaks and boost leaks but I don’t have any that are large enough, and trust me I’ve been searching. I think the injector is just too much and the arc 2 can control it but not fine tune it enough?

After doing upper and lower intake gaskets and blindly dialing down the afpr It seems to be happier but I honestly think for straight pump gas and under 20psi that 550s seem to be the way to go. Especially after reading that post about timing and fuel pressure being between 39-45 psi base.

So maybe 660s need the 50/50 mix of e 85 to be more controllable and more in line with that chart? Honestly I like just throwing 93 in it and going about my day though.
 

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What does your mid fuel trim show? I’m curious what it says since you have an overly rich idle(81 trim). It could very well be that you are adding too much fuel with the low and accel knobs this causing light load/throttle conditions to go super rich instead of a gradual richening to WOT. Stock maps should be around 13-13.5 AFR at 0 psi and 14.7 cruising or idling. You may want to see what your airflow Hz reading is while cruising and it’s going rich. It could be shifted dramatically from where it should be because of the base ARC-2 settings.

I’ve found on 1st gens that the low fuel trim maxes at 81 on a datalogger even though it has a 80-120 range with 100 being optimal. This corresponds to a +/-12.5% fuel correction the ecu will make and right now the ecu is seeing your 02s as full rich thus trying to take out 12.5% of fuel to try and hit stoich 14.7:1 AFRs. Boost and vacuum leaks will have some effect on running richer but not a significant amount. That is in the piggyback settings.

Plenty of people have run 660s just fine on pump gas and you should be ok. They are a little bigger than you need for sure but I imagine you will only see 1-2 degrees of ignition timing advance. To know for sure you would need to log rpm, timing, and boost if you don’t have a way to log ECU load correctly. If anything the larger injectors will just mean you’ll hit knock sooner on pump gas than on something smaller like 550s. You should still be able to make 16-17 psi on pump even with the larger injectors.
 

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Discussion Starter #4
Mid shows 98. If I mess with the low and accel knobs it won’t idle or rev off idle near as smooth as it is now. My thoughts are the 660s are just to much fuel for idle to be around 100. I dialed back the afpr but unfortunately I have no reference.

the part I don’t get now that you say that is that at idle my af gauge is around 15-16-17, I’m sure that’s ok, but it’s still pulling fuel you say. Then when driving it goes to 12-14, when getting on it the last time today I saw 10.9 Af but got 3 counts of knock.

I don’t know where my injector flow results went but I remember they were not all 650, some plus some minus. I got them cleaned and tested but I guess not flow matched.

as always, thanks for the input! I appreciate seeing your name reply because I know you know your stuff. I have a spare maf I could try. I also was thinking maybe it’s my massive air filter? There were 2 filters depending on the arc2, a long one and a short one, I have the long one but mine was Supposed to be a short one.
 

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I finally got my fuel psi sensor installed but I just realized that it may be wrong. I got a fuel rail adaptor with gauge and that didn’t work, kept leaking. Now I have the aem fuel filter bolt with adaptor going to a sending unit. I have an afpr which is why I wanted the fuel psi sensor but with it being at the fuel filter I’m guessing it won’t tell me anything about adjusted pressure after the afpr, correct?
Our fpr is a back pressure regulator. It controls the pressure at it's inlet (upstream) by adjusting the flow of gas thru it. This is different from say a pressure regulator on an air compressor tank which controls the pressure at it's outlet (downstream). Afpr's that have a gauge or sensor connection on them for our application have that port connected to the regulator's inlet. So the pressure after the fuel filter (where your sensor is) is virtually the same as the pressure in the fuel rails and at the fuel injectors and in the line to the afpr (if remote mounted). So your sensor should be reading the correct pressure. The pressure at the outlet of the fpr or afpr is close to zero as the gas is routed back to the gas tank. You do have a small vacuum line from the afpr to either the fuel pressure solenoid or the intake plenum, correct?
 

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Discussion Starter #6
I have the AEM afpr and adaptor. I have the vac line hooked up. It goes to one of the 3 nipples on top of the throttle body, i have a t in that Vac line that I use for my lcdbc boost/vac reference too. I only see about -9.5 to -10.2 vacuum though on the lcdbc. Speaking of that I need to ask @rossb if he got his to read lower since we both seem to have that issue.

I’m confused on how injectors, that are past the afpr, operate on near 0 psi? But if you’re saying you can check fuel psi at the fuel filter and the afpr can effect that, That’s good And I can hook it up, I thought I just wasted money.
 

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The AFPR should be coming off the rear fuel rail on a stock setup. What he is saying is that the AFPR controls the pressure in front of it(up stream) by bleeding off pressure to the downstream. This makes it so everything up stream of the AFPR is the same, so it shouldn't matter where your gauge is as long as it is upstream of the AFPR.

Think of it like a dam on a river. If the water level(pressure) up stream gets too high, you open up a bypass and the level drops. If it is too low, you close it and let it build back up.

As for my vacuum at idle, I'm still around -9.3 to -9.0 with no load(AC/lights/etc.), nothing I do seems to affect it.
 

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Mid shows 98. If I mess with the low and accel knobs it won’t idle or rev off idle near as smooth as it is now. My thoughts are the 660s are just to much fuel for idle to be around 100. I dialed back the afpr but unfortunately I have no reference.

the part I don’t get now that you say that is that at idle my af gauge is around 15-16-17, I’m sure that’s ok, but it’s still pulling fuel you say. Then when driving it goes to 12-14, when getting on it the last time today I saw 10.9 Af but got 3 counts of knock.

I don’t know where my injector flow results went but I remember they were not all 650, some plus some minus. I got them cleaned and tested but I guess not flow matched.

as always, thanks for the input! I appreciate seeing your name reply because I know you know your stuff. I have a spare maf I could try. I also was thinking maybe it’s my massive air filter? There were 2 filters depending on the arc2, a long one and a short one, I have the long one but mine was Supposed to be a short one.
Mid is fine then and you don’t need to adjust the low at all. You should be able to take out one click on Accel to dial some fuel out of idle without issues normally, but you’re already idling pretty lean. It makes me wonder if you have your AFPR dialed down too low. Lower than 39 psi with the vacuum line disconnected it doesn’t give good enough atomization. The stock 43.5 psi vacuum line disconnected pressure setting has always worked for me.

I don’t think your injectors are too big to control. If that were the case you would have to pick from 11-12s idle and 16-17 no inbetween because one click wouldn’t be finite enough to adjust to stoich. That’s what I found for 1000s on E-85 and the stock ecu. I just ran it lean until I got a flashed ecu and then I was able to hit 14.7 without a problem but the weird thing is the ARC-2 doesn’t do a good job at imitating a stock scaling no matter what you set it at unlike the GM MAFT combo set to 360 base settings and zero idle, mid, and wot knob settings. I needed to rewrite almost all of the timing map to correct the ecu load shift with the ARC-2 on bigger injectors. Anyways, you won’t have FPR overrun since you have an adjustable one but I’m curious if your base fuel pressure is set too low and causing some issues. Usually if it’s too high and won’t adjust down, then you have too restrictive of a return orfice. That was an issue with the AEM AFPRs for awhile.

It still seems like something else is going on causing you issues not being able to get your fueling dialed in correctly. Have you replaced your 02 sensors at all recently? If not and you have access to a datalog, do they cycle from 0-1V back and forth after the car warms up and it is closed loop feedback? When they get lazy before they trip a CEL they will kind of want to hang some at one end or the other or even read mostly lean at greater deterioration. Also, you can observe them hanging lean or giving some odd signal voltages under acceleration before catching up to a higher voltage they should be reading.

Also, you should have a dedicated source for your FPR because you don’t want anything else to cause an inaccurate or lazy reading since it has to increase your fuel pressure 1:1 with boost. I have wondered whether or not the top three ports on the TB flow enough to be a good spot for the FPR, but have never tested it with a MAP sensor there vs directly on the intake manifold. It might be worth relocating to see what happens. I have mine behind the TB on the intake manifold and relocated the BOV to the back of the intake manifold.

The location of the FPR on a stock setup connected to the rear rail is the last part of the whole fuel system before the return. The only place the fuel can go from there is out the exit bleed portion of the FPR through the return line to the tank. Everything before the FPR meaning the rails, loop, and feed lines are at the same fuel pressure. You have 6 injectors using volume off that main feed before it gets to the FPR but I’m sure the FPR can react fast enough to keep up with the demand on the injector supply/use and sustain the head pressure of the fuel. If you ever split an injector o-ring you’ll find out the fuel pump can supply quite a bit of volume lol. Maybe that will help visualize where the FPR comes into play for regulating pressure and how there isn’t anything else(sans injectors spraying fuel) in the system to change it. If your fuel pump was maxed out you would see a dip in fuel pressure because the pump can’t fill up the fuel rails with as much volume as was leaving through the injectors.
 

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Discussion Starter #9 (Edited)
It’s possible the oxygen sensors are getting slow. I can get them to cycle properly though. I still run my arm1 and it’s easier to see it dithering. I have that, the wideband, and then the lcdbc telling me knock and boost. I get dizzy trying to watch it all lol.

So I had the aem afpr set to factory settings which they claim is 40psi out of the box. Then I dialed it back today Due to finding that chart. I figured I wanted to be at 39psi or the lowest I could go since I’m not Even pushing 560hp.

You are saying to up it to 43.5 to richen the idle so I can dial the low and accel back right?

I can redo the vac lines too. I think I have enough to go off the back port on the intake manifold. I think either blackstealth or stealth 316 said to tie the boost gauge ref source into the fpr line lol

EDIT: It was a vac reduction walk through On 3swiki that said to tie the boost gauge to the fpr source.Not blackstealth or stealth 316
 

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You’d have to watch the voltages on a log to get a good idea if they were being lazy going into boost other than the obvious not cycling when in closed loop the rest of the time.

FPR should be set with the vacuum line disconnected so it will read higher. Once you connect it the vacuum will lower the reading. Disconnect it, see what it reads, and adjust it back to 43.5 if it’s lower or higher, then reconnect the vacuum line.

I’m not honestly sure the throttle body ports on the top are large enough to handle much of a demand from one important device let alone two.
 

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Discussion Starter #11
Ah ha I wrapped my mind around the afpr thing and the fuel psi. Like putting your thumb over a garden hose changes pressure IN the hose. Duh.

so I’ve got some work to do, where are you getting your boost/vac reference from?
 

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Anything after the throttle body will give you vacuum and boost readings which is what you want for your FPR and LCDBC MAP sensor. I have my FPR connected to the port right behind the TB on the intake manifold where the BOV connects to in the stock configuration. All the rest of the connections except the boost reference side of the boost solenoid are all connected to the back of the intake manifold.
 

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Discussion Starter #13
Cool, I will work on re-routing some stuff and getting the sending unit wired in. I guess I worded that wrong, is your BOV source on the back side of the intake manifold too then? isnt there just 1 nipple back there?
 

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Cool, I will work on re-routing some stuff and getting the sending unit wired in. I guess I worded that wrong, is your BOV source on the back side of the intake manifold too then? isnt there just 1 nipple back there?
There’s only one but I have multiple ones added with some NPT to barb brass fittings from the hardware store.It’s thick enough to drill and tap and still get a good seal.
 

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Discussion Starter #15
I borrowed a timing light from a guy at work to check that. It was at 5. Reading stealth 316 I bumped it up to 7 to try. Also using the lcdbc to check idle since it has a test for that I noticed it was pretty dang low. Warm Idle should be 750ish right? So when using the test I shouldn’t hear the engine struggle to run right? Base idle should be 700rpm and it sounded like it was dropping to 500rpm. I adjusted the biss out to help with that. Now I hear a slight difference when hitting the 10.5 timing idle test in the lcdbc.

So now my lcdbc shows 19-20 degrees at idle instead of 30. I’m a bit confused as to what it should show at idle but I think 15-20 depending on altitude? And when I hit the 10.5 timing test button idle doesn’t drop near as much.

I put the afpr back up 2 turns as well

With that done I set my end psi to 15 on the lcdbc from 11. Ended up with 18.1 psi max and 1 knock count.

idle is showing anywhere from 14.5 to 16. Cruising she goes way rich again now that the afpr is set higher. But like you said maybe I need to go higher and then dial back.

My pig tails to connect the fuel psi sending unit up will be here tomorrow so I’ll mess with that soon. Now all I can do is see how she cold starts with the changes I made.
 

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This is a great discussion but i have to ask, if you have access to E85 and basically all the mods to run it already installed, why aren't you going for it?
 

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Discussion Starter #17
I wanted to get it running right on pump first before doing the mix. I figure that transition will be easier. But part of me wants to just run pump and 550s are bette for that. I guess trying e85 is easier than putting in 550s.

My other concern is reading afrs. Do you still target 14.7 and 10.5 as references or do those change when going to e85?

I guess basically I don’t just want to do it without knowing what to expect once I put the mix in the tank lol. I guess I still have knock values to keep me safe? Lol. Maybe I’ll try it next tank.
 

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Understood. I agree that 550 would be better for pump, especially if you have knock issues, but that doesn't mean you can't make the 660s work on pump.

Yes you can still reference the same AFRs. Stoich for ethanol is different than stoich for gasoline in terms of relative amount of air and fuel, but most people "think" in terms of gasoline AFRs so very few people (if any) actually change their wideband configuration settings to read lambda or ethanol AFRs. So basically, you still tune based on the same AFRs, keeping in mind that most people opt to not run quite as rich WOT with ethanol (maybe low 11s instead of 10.5). You still get the NBo2 cycling around 14.7 in closed loop.

I too was extremely paranoid about putting this 'mysterious' fuel into my car, lol. As ive written about on some other threads i did 50/50 mix (5 gallons of each) for a while, then after i hotwired my fuel pump recently, I'm now almost full E85. I'm tuning myself with SAFC, and its not bad at all. You will notice immediately when you put in the E85 that you need to increase your corrections (i.e., less negative), but if you are going to go from full pump to say a 50/50 mix, the change wont be THAT dramatic and the car will still run on your pump settings just a bit leaner. As you alluded too i just watch knock on my torque screen and AFRs with my wideband when i do pulls. I used to datalog 3x 3rd gear pulls, put in excel, plot AFRs vs. RPM and make SAFC corrections based on that (when i first started mixing), then after that as i increased ethanol % i literally just did a 3rd gear pull watching AFRs, pulled over and 'eyeballed' how much fuel to add/subtract based on what i saw, then did another pull lol. Of course just be careful on the first pull after adding ethanol to make sure AFRs are in check, and perhaps go down to wastegate boost. Tune first, then up boost later. The other good thing about ethanol (besides higher octane, more cooling, etc), is that it typically likes a little more timing, so the 'extra' timing you get from a piggyback is actually a good thing.
 
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Discussion Starter #20
Lol. Damn alright then!

I mean it only makes sense that e85 will help with my low fuel trim problem too I think.

I’m not sure if anyone has ran 50/50 with an arc 2. Generally you keep the mid knob at -7. Wonder if that’ll change with a 50/50 mix?
 
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