I know on my FPR (Aeromotive A1000) if the vacuum screw is screwed in too tight, the screw will actually interfer with the internal components that control fuel pressure. It can also result in a unsteady fuel pressure. so anyone reading this, perhaps look at your vacuum port that screws into the FPR, if its screwed in too much it will mess with the regulation of fuel pressure.

 

Don't have access to an oscilloscope

I believe I did changed the sample rate after purchasing the sensor, mainly because I thought the sensor was bad. With the help of Cludwig at the time (thanks dude!) we logged the raw output from the sensor and there was evident voltage oscillation.

I will log FPR, sensor raw data, and other parameters, hopefully this weekend.

 

With the issues you're having with sensor data oscillating, I wonder if you have an issue with the 5v regulation or with signal ground noise. I'd be interested to see what 5v ref does while you're driving the car. Does your signal ground, the black/white wire, connect directly to battery negative?

 

Do you still have the sensor mounted to the fuel rail where the fuel temp sensor used to be? I previously had the same set up and head strange readings. I ran a -4 line from this location and relocated the sensor to the fire wall and now the readings are perfect.

 

This would also show with a scope.

If there were an overall problem with reference or ground I'd expect to see that on other sensors (TPS,MAP, etc) but a wiring fault on just that sensor wouldn't. While it would be good idea to test for a circuit fault, I wouldn't expect it to manifest itself this way.

 

All sensor wires are connected to the haltech. As part of the troubleshooting process, I have a created a new sensor harness, since that did not do anything concerning the oscillation, I went ahead and created a new harness with the ground to the sensor going straight to the battery negative post.

Oscillation did not improve with the new harness, or the harness that had the ground wire going to the battery ground post.

I did, I moved the sensor mount to after the fuel filter, and from there a 1 ft of -4 aeroquip rubber hose, and then the sensor. This did not improve the pressure oscillation.

There's another sensor on the same harness that its also having the same issue (oil pressure). Both sensors are sharing the same 5v wire, and ground wire on the ECU. Both sensors have been tested with a ground wire going straight to the battery negative post, and 3 different harness were made for the sensors. Same oscillation issue, by the same amount, regardless of ground location, or harness.

What throws me off, is that with the engine OFF, if I apply 12V to the fuel pump, the fuel pressure is steady where it should be; but as soon as I start the engine, the oscillation occurs.

 

sounds like noise from alternator possibly.tried shielded wire to sensors?

 

I haven't tried shielded wire for the sensor harness. I never thought of alternator noise, since both sensors are on the opposite side of the alternartor, plus as vicoor mentioned, there are no other apparent issues with the other sensors (specifically the TPS, which is also a 3 wire sensor, and its the one closest to the alternator)

On any case, I guess I could test this theory fairly easy. Start the engine without the alternator for 30 seconds or less. I should be able to tell if there is any oscillation right away.

 

irrespective of all the noise/problems/etc/etc/etc. Isn't the bottom line that enough fuel is getting to your engine. And when you look at what controls your injectors is your base fuel map. If the base fuel map is smooth and your AFR's are good, and you have a weird pressure drop or some weird data, more than likely the sensor or some other factor is messed up.

Because the proof is the smooth map and AFR's are where you want. If the map does something funky, then you have issues somewhere.

When I first tuned 15U's car on this forum we couldn't get into boost. He had multiple vacuum leaks, and the base fuel map showed exactly that. It also had a ton of problems at upper rpms, the fuel would just slowly die off.

Then I tuned another persons car. He had connected the primaries and secondaries backwards. I had it leaned way out and told him either he swapped the injectors around, or wired them backwards. car did still run and was dripping fuel out of the exhaust manifold.

I had a problem with my FPR, the side vacuum port was tightened by someone else messing with me car (he was just looking at it and tightened it down, or what he thought) which contacted the internal spring that connects to the diaphragm. My FPR couldn't control the pressure, I noticed it through my AFR's leaning out during acceleration. It took me a while to figure it out and a bunch of research that the vacuum port on the side was too tight, especially since I didn't tighten it.

Most everything can be seen through AFR's that are fuel related or engine related (vacuum leaks, clogged fuel filters, clogged air filter, worn components.

If AFR's and base map are good, its impossible to have a pressure drop like one is saying, therefor the sensor, wires going to or from, noise, etc is the problem.

 

I've attached an image that might help to understand how the data rate would give you readings like that.

The fuel pulses remaining constant with the pressure and pulsing with the opening/closing injectors, and the frequency of the pulses increasing with the RPM, this graphic hopefully can show how collecting data a even intervals can result in erratic looking readings even though the average pressure remains constant.

 

Your logic makes sense!

AFRs somewhat oscillate at idle, but they are solid at WOT, and the fuel map seems to be very linear on both axis

I now see what you mean about the sample rate, I thought you were talking about the data logging sample rate, not the sensor reading data rate. As far as I know, the haltech PS100 has a fixed sample rate for sensor readings.

I could try finding a cheap oscilloscope, but knowing how to use it its another subject in its own.

 

No, I was talking about the sample rate of the log. My point is that the log readings are affected like this and it may not be a problem that you are looking at. In fact, as was already mentioned, you AFR readings are trying to tell you that it's ok.

I'm like you in that I am always trying to analyze/over-analyze everything, which can sometimes save having big problems, but more often just leads to new learning experiences.

Looking scope will likely just show that in fact the fuel pressure is pulsing like would be expected. But would allow you to see the overall pressure increase with boost pressure, verifying that all is well.

 

I see! This makes me sad, because my whole point of logging pressure was so that I could use the ECU engine protection setting. With the oscillations, is very difficult to set engine protection parameters, without them interfering during "normal" engine conditions.

Thanks for your help, same goes to everybody else, and CLudwig (which has gone above and beyond)

 

What you see in the datalog isn't necessarily what the ECM "sees".

The datalog polls and captures data at a specific rate so a constantly changing reading like this can appear wonky. But the ECM is capturing this data way faster and is not as susceptible to this error. Some inputs may also have smoothing functions. Maybe someone with specific knowledge of these inner functions on a haltech can weigh in.

No matter what, the lowest values it could record is the bottom of the oscillations, so if you set the safety parameter by that value, I'd think that would work fine.

I didn't ask before, but are you capturing the log directly to a laptop, or logging to the ECM and retrieving it?

 

Update: After putting the fd on the back burner for a year, I ended up with it back at my house last week. Since a couple shops hadn't figured out the issue I felt stuck... So I reached out to Chris Ludwig and he got back to me right away about a couple things I should try.

He asked me to try a fuel pressure test and try running the fuel pump wire direct to the battery. So I tried the second part first and I ran a log the fuel pressure was holding WTH I was told this was tried already.... This was a great feeling finally something and just at the right time I planning to take it to another shop to get it checked out again and just go back to 91 until we figured out the issue.

The reason Chris said to run direct is because the wire from the ecm to relay was already at it's capacity from his experience and he replaces it when he builds harnesses.

So I took it to the Dyno on Tuesday night on E85 @ 18lbs it made 398/348 ftlbs tuned by Nelson Haltech P1K, stock ported motor, GT35r 1.06 divided. The only issue now is the fuel pressure climbs to 58 psi dropping to 6 lbs early and drops another 3lbs at 6500rpm stronger pump? currently Bosch 044. So Nelson tapered the boost to compensate in the higher rpm's. I have engine protection setup on my car for pretty much everything so the fuel pressure issue has never been problem except a road block for more power.

Now down to the tune, The fd has never ran so good... I was blown away it's like driving a newer car it's super smooth in transitions 1000/2000cc, idles great, revs super smooth and the drive-ability is freaken amazing... It hits so much harder now with Nelsons new map, I never thought it would run as smooth as my evo but it does. My Evo puts down 400whp on e85 but the fd makes it feel so slow now lol

Thanks again for all you Help guys... -Jonathan

 

Good to hear you are making progress! With a single 044 on e85 you could be maxed out all ready. I have maxed my single 044 out on pump gas and hit 548whp so with a crude calculation subtracting 30% would be 385hp.

 

Question would a surge tank with another inline Bosch 044 help with providing additional fuel pressure/volume? I know it works great for low fuel and sloshing but I'm currently running out of fuel and don't see how another inline 044 would help this out vs running two lines and two pumps in parallel.

 

I'm actually working on my new fuel set up right now. Going with:

(1) Bosch 044 in tank as a lifter pump

to

Aftermarket Industries SP800 Dual pump Surge tank featuring (2) Walbro 460's.

Depending on what youre looking for power wise..... YOu may need another pump.

 

A surge tank goes on the low/no pressure side of the fuel system.

Putting pumps inline with each other works for marginal situations because fuel pump flow is related to pressure. As pressure goes up it gets harder to pump so flow drops. Having two pumps inline is like having double the pump power so you get less pressure drop.

I tend to prefer doing pumps in parallel with a pressure switch so the second pump comes online at a couple pounds of boost. It takes a bit more effort to do, but you double your flow capacity at pressure. Having plenty of extra capacity is good because pumps degrade over time.

 

@Manny very nice. I'm looking at their 1.7L dual 044's but I don't want to run 2 pumps let alone 3. My power goals I'm perfectly fine with it's just the fuel drop...

 

Thank you for explanation. It's pretty much a gamble trying the inline route then. I roughly need another 10 pounds of holding pressure.