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PostPosted: May 20, 2019, 5:01 am 
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The fuel pumps are brushed DC motors (shocking, scary, and anxiety inducing, but normal...), so dropping the voltage supplied to them with a resistor will reduce their RPM/torque output, and produce a lower max pressure. The vanes simply move less fuel per unit of time

Mitsubishi used a relay that dropped in a resistor to limit the voltage, and reduce max pressure, till the engine passed a given load range. Kept the FPR from being overworked, and allowed for more linear response.

As far as I know, any/all fuel pumps can be fed a lower voltage without much issue.

Out of curiosity, what's the amp draw for your pump when priming the fuel system with the engine off?

EDIT: Reason I ask, is there may be a way to add PWM control of your pump using OEM Jag/Porsche parts for under $40 (ebay/junkyard), since you have a megasquirt already. Just need to make sure the module I direct you towards can handle the pump stall-load when engine is not running.

Could also use the same units for fan control.


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PostPosted: May 22, 2019, 8:05 am 
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I run a fuel pressure sensor into the MS for continuous monitoring. IMO if you have a decent return-style fuel system with a normal FPR you don't need to get into PWM control of the fuel pump.

The 90psi fuel pressure was probably making autotune just about useless. With pressure that high, even the tiniest spurt from the injector could be too much for idle/low loads.

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PostPosted: May 24, 2019, 1:29 pm 
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300D50:
Thanks for the info! Will have to be a consideration if my return line fix doesn't work. I haven't yet had a chance to check the load while priming, but I'm hoping to get a little work done tonight.

Laminar:
That's my thoughts as well, will probably add a fuel pressure sensor when I add boost, because I will need a new regulator then too.

My AN bulkhead fittings and a tee fitting arrived in the mail yesterday, everything looks like its going to work, just have to decide where to tap in the new return. The pump hat is a little cramped with other plugs and hardware, but there is a hat on the other side of the tank which I think is just for the transfer pump that might work. This weekend is a two day driving school out at High Plains Raceway that I am helping to instruct, so unless I can get time in the garage tonight or tomorrow night, not much work is going to get done. May have a few hours on Memorial Day but I think we have plans. Installing the new fittings and lines shouldn't be too big of a job, and I need it done before next weekend.

More soon.

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PostPosted: May 24, 2019, 1:59 pm 
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I haven't been keeping up on this thread, but if the issue is about insufficient fuel flow, powerful engines can require powerful fuel pumps, which can take a lot of current. If flow is in question, put a voltmeter as close to the pump terminals as possible* and go for a drive, with the meter where you can watch it. It could prove surprising.

Regarding fuel pressure, watching it at idle won't tell you much. You have to see what it is under hard acceleration (maybe putting a Gopro on it to record it if you can't see it yourself). Granted, if you're running rich, it's "probably" not a problem, but needs to be confirmed.

*If the problem is a ground wire inside the fuel tank that's too small, the above won't work. If in doubt, go with at least #12 wire.

**What horsepower are you reaching for?

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PostPosted: May 24, 2019, 8:13 pm 
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KB58:
No worries on not keeping up; the current problem is far too much flow/pressure. Factory spec (even at idle) is between 48 and 53 psi, and I am seeing over 90 at the rail. The eventual goal is somewhere in the low 400s on E85, mid 300s on pump gas. My wiring is all good, the issue is the insane pressure. Some research says that there is a pinch point as the hose connects to the tank in the factory return line that gets clogged, and the fix is either to clear it out with some sharp welding wire, and/or run a second return line. I intend to do both for future proofing, if I can find a place to install another fitting in my fuel tank.

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PostPosted: May 25, 2019, 10:53 am 
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KB58 wrote:
if the issue is about insufficient fuel flow, powerful engines can require powerful fuel pumps, which can take a lot of current. If flow is in question, put a voltmeter as close to the pump terminals as possible* and go for a drive, with the meter where you can watch it. It could prove surprising.


This was a problem with the Buick Grand National guys once they upgraded their fuel systems. There were any number of solutions trying to avoid stringing new wire, including a vendor who sold a "voltage booster" which somehow avoided smoking the wiring harness...


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PostPosted: May 31, 2019, 5:52 pm 
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Countdown to dyno day! Brought the car in for a checkup and smoke test at the tuner, and aside from one torn PCV hose, the car passed with flying colors! I'm just about finished with the fuel system, figured out where I'm going to tap in the new return line. Car is getting on the dyno Sunday, so I'll update after that since I'm pretty pressed for time. Wish me luck! :cheers:

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PostPosted: June 14, 2019, 12:21 pm 
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Made it to the dyno:

https://youtu.be/unU9RJR6VcY

This was the best pull we got out of the car, but I will get back to that. Been a very busy couple of weeks since them. To pick up where we left off, I was trying to tackle a fuel pressure problem related to old lines, and the new Walbro 450 pump. Research said that I needed to add a second return line to get around a known pinch point in the tank return line. The weekend before the dyno day, I got to talking with the owner of SCR Performance, who told me straight up that the factory regulator would not handle the flow from that pump, and would need to be replaced. The tricky part is the factory regulator is not in line, it is bolted to the fuel rail, and has an O-ring fitting to connect it. Fortunately, it meant I had an excuse to get into the machine shop and actually make something functional for my car! So I took off the FPR, brought it into the shop at work, and between breaks, lunch, and a long afternoon, I made a simple FPR-delete piece:

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It works very well, fit nicely, and no leaks at all! I also went to the dyno shop a few days early, and they sold me an Aeromotive adjustable FPR. Only had to drill one different hole in the mounting bracket, and then it fit really nicely onto some already existing studs on the firewall:

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After the dyno checkup on that Friday, I started working on the return line. I was very pressed for time since there was an autocross the next day. Thanks to some very helpful people on the E30 Facebook groups, I found that the best place to run the return line is into the filler neck, and drop some submersible hose down into the tank to stop aeration. So I marked a point, pulled the filler neck, and drilled a hole. I could not get any acceptable bulkhead fittings or anything that would fit my application, so I set up a highly specialized custom jig *cough* a bench vise and a zip-tie *cough* and used JB weld to assemble the fittings:

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As you can see here, I really didn't use very much JB Weld... So I left it to sit overnight, and it held! The submersible hose fit right where I wanted, so I went ahead and reinstalled the filler neck. A quick aside here, submersible hose is REALLY expensive! Like $33 a foot! And I had to order it in. Anyways, I reinstalled the filler neck, test fit it with my return line, and it worked great! But I wanted more JB Weld on it, so I went to pull the return line off and it snapped off in my hand :BH: . After considerable fiddling, and only a small amount of panic, I managed to reattach the brass fitting with a TON of JB Weld. I should mention at this point that it is now 10:00 at night, the night before the dyno. So I went to bed, hoping that the JB Weld would set overnight and be strong enough. So two hours before needing to be at the dyno my car looked like this:

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Luckily, the JB Weld set, I attached the hose, and I applied another thick layer of JB just to make it even stronger over time. And it held! We set fuel pressure at 50psi on the dyno and it is working perfectly.

Now to the elephant in the room, the crazy high-RPM breakup on the dyno. I should mention that we spent the entire morning and part of the afternoon tinkering with wiring before even getting on the dyno. They were beyond helpful in diagnosing and fixing my cam sensor problems (improper wiring), and getting the idle going as best as possible. We were immediately seeing some issues that wouldn't be fixable that day. The first was that as soon as we got the cam sensor working, my coolant temp signal got super wonky. Jumping all over the place randomly, which really messed with the tune. The next issue was that when the RPMs dropped too low, like 500 RPM, cylinder 6 would stop firing. We weren't (and still aren't) really sure why. Another problem is a very rough, and surging idle. The last problem of course is the breakup under load. Nonetheless, we pressed on, and even with the litany of problems, the car still made 100 rwhp, which was already higher than my lowest estimate. They guess once everything is fixed it will be making 130-140 rwhp on their Mainline Dyno, which they claim generally reads low. That means it would be making noticeably more than the stock 168 bhp, which I would be very happy with.

Rob, the guy who was tuning my car on the dyno, works in electronics, and agreed to help me diagnose the car under the table. The issue with the coolant sensor, and some of the idle problem was simply fixing the shielding on the crank and cam signals. So already the car is running much better. We got together again the other night with an oscilloscope, to try and adjust the VR trim pots, and determined that the incoming signal from the crank position sensor was actually inconsistent. So we are 95% sure that the problem is in the sensor itself, or its wiring. I think sensor, because they are a known weak point on these engines, and this one is almost 200k miles old. So I have a new one coming, but it won't be here until almost July.

Big shout out to the Boost Creep, who tuned the car, and DIYAutoTune, who I've been continuously exchanging emails with through this whole process. I have a little break until the new sensor arrives, so I'm going to take a little break from the car, except maybe mounting the front fender flares.

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PostPosted: June 18, 2019, 8:52 pm 
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Picked up a crank position sensor today from a racing buddy, came off a car that was known to be running and healthy. Tomorrow I'm getting a new protective cover for the wiring for the sensor. This is important because the wire runs directly across the upper timing cover, very close to the V-belts, and some coolant hoses. My car doesn't currently have that cover, the wire was just zip-tied in place, and those zipties eventually broke. Broken zipties have resulted in damage to the wire shielding, which could have something to do with my signal problems. Will report back once the new sensor is in and set, later this week.

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"Stuckness shouldn't be avoided. It's the psychic predecessor of all real understanding." --Robert Pirsig

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PostPosted: June 26, 2019, 10:36 pm 
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It's solved now. Put in a new Crank position Sensor, and spent a fair amount of time over the weekend tightening up the gap, and adjusting the trim pots. Gradually I managed to get the signal to clean up a little bit. Could get the car to rev up to almost 6000 RPM, but then it would still breakup. Gave up for a couple days, and had a good brainstorm. I had some concerns about the CPS I had. I'm on my third now: the first one was all beat up, with damaged shielding, so I tossed it. The second one was given to me by a racing buddy, off a car that had been rolled. Unfortunately, the wire was so damaged that there was no signal at all. The third one is a Hella replacement, but it turns out it doesn't have a metal body like the OEM one, and apparently they aren't built to the same standard as the metal ones. So I know that the VR sensor that came on the car originally is not the most reliable, even the OEM ones.

So I figured I should just change the sensor entirely; DIYAutoTune sells a hall effect sensor that is supposed to work pretty well, so I ordered one. While talking to some other E30 people about the hall sensor, and how best to fit it to the car, I was also going over datalogs with my tuner. He was going through a list of possible things that might need to be changed, and on a whim we decided to swap the ignition input from "falling edge", to "rising edge". And just like that, the signal cleared up perfectly! Made a test pull on a back road, and it revved all the way to 7000RPM with no problems! Another E30 guy confirmed our suspicions about that setting, so I sent an email to DIY to let them know the information they have on their website is incorrect.

So, next step is to get a timing light on it, to make sure the base timing is still correct. I'm sure the setting change has shifted it just a bit. Following that, I need to mount the front fender flares, and go over the car to make sure everything is still tight. I have another dyno appointment on July 10, and then July 13 is the next autocross! Things are looking up!

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