[HWYSTR455]

The pressure transducers fail easy when its mounted to the engine, vibration kills them fast.

I use a N2O or brake line, brained stainless, and mount the transducers on the firewall. On the A-body, I mounted 2 with a pair of coated clamps, in the divot where the trans tunnel meets the firewall, one for fuel psi, one for oil psi off the back of the block. They are hidden for the most part.

Not sure it the transducers are GM, but I was thinking more like IAT, CTS, MAP, and TPS stuff.


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[HWYSTR455]

Looking at that vid, the fuel psi, it looked like you may have the vacuum reference hooked up to a vacuum source. With choppy cams, it doesn't like using the reference is what I've found, but could also be idle compensation.

How is it at say 1000 rpm?

Could be interference, but if it were that bad, I would think other stuff would be affected too. Like ignition.


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[ID67goat]

Originally Posted by Formulajones

I'm dealing with that right now. Bought the expensive stainless Holley sensors to monitor oil pressure and fuel pressure.

Oil pressure sensor is screwed to the block right next to the MSD distributor, and the fuel pressure is screwed to the fuel rail on the side of the Sniper unit.

I was worried about RFI but the oil pressure sensor is doing just fine. Fuel pressure sensor on the other hand is jumping all over the place from 40-70 psi and does it so fast I had to log it and slow it down to actually read the numbers. Holley tech told me that has to be RFI, but how so if the oil is okay. Those fuel readings can't be correct, can't see how the unit can make fuel corrections with a huge swing in pressure like that but the car runs okay. (set pressure with mechanical gauge) Will be doing more diagnostic like isolating the sensor from the engine completely free of vibration and RFI etc.... but my gut tells me it's a faulty sensor. Because nothing has bothered that oil sensor, vibration, RFI or otherwise.

I think the electric fuel pressure sensors are sensitive to vibration. When I had one on a Cummins mounted to the engine it died in no time at all. The next one I remote mounted and it seemed to be ok after that. please let us know what you find on yours....

[Formulajones]

Originally Posted by HWYSTR455

The pressure transducers fail easy when its mounted to the engine, vibration kills them fast.

I use a N2O or brake line, brained stainless, and mount the transducers on the firewall. On the A-body, I mounted 2 with a pair of coated clamps, in the divot where the trans tunnel meets the firewall, one for fuel psi, one for oil psi off the back of the block. They are hidden for the most part.

Not sure it the transducers are GM, but I was thinking more like IAT, CTS, MAP, and TPS stuff.


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Ah yes the CTS is a GM piece supplied with the Sniper. I have transducers on the brain because that's what I'm dealing with right now.

I was told vibration could be a culprit, but oddly the oil sensor, screwed right to the block, is doing fine.

Worse case scenario I'll have to use the -4 braided line to move the fuel sensor off the rail. As long as I can find a suitable place to hide it. I really don't like this stuff being out and visible. I'll try the vibration theory with a temporary piece of that braided hose to isolate the sensor as soon as I get back to it.

[HWYSTR455]

I'm starting to think the transducer reading is right, the AFR is jumping around too.

Oil psi jumping from 74-81, that's kind of in range too with a low idle speed and choppy cam.

On the oil psi, what's it like at 1000 rpm? Steady?

What's your idle speed? (please don't say 650!)


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[Formulajones]

Originally Posted by HWYSTR455

I'm starting to think the transducer reading is right, the AFR is jumping around too.

Oil psi jumping from 74-81, that's kind of in range too with a low idle speed and choppy cam.

On the oil psi, what's it like at 1000 rpm? Steady?

What's your idle speed? (please don't say 650!)


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It's idling about 1100 rpm in that video.

Yeah oil pressure seems normal so not worried about that one. It's cold in this video, hot idle it's around 40 psi.
I've never had a rock steady AFR, with a carb or EFI, as those 02 gauges always seem to be searching at least .3 to .4 with a little bit of a swing so that doesn't alarm me. But that fuel pressure, if in slow motion, can be seen swinging from 40 psi and up to 70 psi. It's like all over the place crazy. Mechanical gauge reads fine.

I tend to think if those fuel pressure readings were real, this thing wouldn't even run. Since it bases the fuel correction off of fuel pressure I tend to think the computer is seeing what I'm seeing with the mechanical gauge, because I don't think it could possibly correct the fuel tables successfully with fuel pressure swings that severe.

[HWYSTR455]

Here's some snippets, the AFR is following the psi. The lower the psi the higher the AFR number, and visa-versa.

Towards the end of the vid, as it's starting to warm up a little, the AFR is stabilizing. That I think may be due to your afterstart enrich and the slope.


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[HWYSTR455]

Do you have the vacuum port on the regulator hooked up?


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[Formulajones]

Originally Posted by HWYSTR455

Do you have the vacuum port on the regulator hooked up?


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Nope

[JLMounce]

Yeah if the pressure regulator is hooked up to vacuum and you've got a pretty lumpy cam, that can be a result. I'd unhook the vacuum line, let the system idle for a bit and see if anything changes.

On the FiTech's, they were originally supplied without having a vacuum line attached to the pressure regulator for systems that used a 4 bar regulator. My system is setup like that and I've never had an issue with idle fueling. Though I also don't have a massive cam either. 232/238 112 roller. I've never had an issue with idle fueling, even given the constant 58psi pressure.

Newer systems ship with a vacuum line attached to the 4 bar regulator and routed to one of the rear vacuum ports.

I don't think you would overlook this, but just out of curiosity, if you do have a vacuum line attached to the regulator, it's not plumbed to a single intake runner is it? It would need to be plumbed in the plenum so it doesn't see bouncing vacuum readings.

[JLMounce]

Originally Posted by Formulajones

Nope

looks like you answered that before I posted. If vacuum is not hooked up to the regulator, you can certainly give that a try.

If that doesn't help, you might consider changing the regulator. You can either do the correct 3 or 4 bar regulator for the system, which should reference to something like an Audi A4 with the 2.0T engine, or if you'd prefer a stand-alone unit you can also use a regulator block off plate, then mount a stand-alone regulator of your choice.

That said though I do think that it's your sender that is a likely cause here. If your fuel pressure was fluctuating that much as it is in your video, you'd see a pretty wild fluctuation in your AFR's as well. From the video, your AFR is about as stable as I would expect it to be given the cam in your engine.

[First Bird]

Is this a compatible CTS? ACDelco pn 213-948 shows 3/8" NPT but I can do a bushing in 1/2" hole in coolant crossover

[Scott65]

Jones, does your system have any lag adjustment for the different sensors? If so maybe try that. To test the transducer, sounds like you could swap the two and see if the results are the same or reversed.

[Formulajones]

Originally Posted by First Bird

Is this a compatible CTS? ACDelco pn 213-948 shows 3/8" NPT but I can do a bushing in 1/2" hole in coolant crossover

It looks like it would be.

Hope all this talk isn't scaring you off. They really are pretty good systems.

[Formulajones]

Originally Posted by Scott65

Jones, does your system have any lag adjustment for the different sensors? If so maybe try that. To test the transducer, sounds like you could swap the two and see if the results are the same or reversed.

I was asking someone at Holley about that the other day thinking I could dummy down the sensor a bit. Never got a response. Goes back to the previous comment of tech support lol. I haven't seen anything in the gauge tables that would allow me to do so. Of course that doesn't mean it isn't there.
I do plan to swap the sensor just for giggles since I have a pair of new ones sitting here. I just haven't gotten back to it yet.

[Scott65]

Hopefully you can get a tech that knows the answer. It seems almost useless to have it where the sensitivity can't be adjusted at all... I'll bet there's some way.

[Formulajones]

Originally Posted by JLMounce

looks like you answered that before I posted. If vacuum is not hooked up to the regulator, you can certainly give that a try.

If that doesn't help, you might consider changing the regulator. You can either do the correct 3 or 4 bar regulator for the system, which should reference to something like an Audi A4 with the 2.0T engine, or if you'd prefer a stand-alone unit you can also use a regulator block off plate, then mount a stand-alone regulator of your choice.

That said though I do think that it's your sender that is a likely cause here. If your fuel pressure was fluctuating that much as it is in your video, you'd see a pretty wild fluctuation in your AFR's as well. From the video, your AFR is about as stable as I would expect it to be given the cam in your engine.

We are thinking the same thing. I was debating about hooking up the vacuum to the regulator just to see what happens. I know it'll drop pressure at idle and part throttle. Holley told me it wasn't mandatory to do so but the system will work that way, I just haven't tried it.
I'm using a Aeromotive 13301 regulator with the EFI spring installed.

The wide swing in pressure and AFR were my thoughts too. I'm not so certain it would even run correctly if the pressure was really doing that. Or maybe the computer is just that good. I don't know.
Yep with the cam, reversion, overlap etc.... AFR's are never really rock solid. If the computer is in fact seeing the fuel pressure move around, I can see how that would move the AFR around trying to compensate though, but man that sure is a big swing.

[Formulajones]

Originally Posted by Scott65

Hopefully you can get a tech that knows the answer. It seems almost useless to have it where the sensitivity can't be adjusted at all... I'll bet there's some way.

Agree, there has to be a way to do it. I can't imagine there wouldn't be.

I can adjust the gauges to read any increment I want, with warning lights at any range I want. Somewhere in there it should have a sensitivity range.

It does have a calibration screen from 0- 5 volts and 0 to 100 psi. But that just changes the accuracy I believe.

[First Bird]

Originally Posted by Formulajones

It looks like it would be.

Hope all this talk isn't scaring you off. They really are pretty good systems.

Hah! No. Not scaring me off. After carburetors and external fuel pumps, I'm looking forward to geeking out on sensor placement and datalogging.

Well I am scared off by the talk of FiTech being Holley now. I wanted to support the little guy but if they now ARE the big guy and will not be supported later on, gives me pause . . .

Are there any other sensors you would replace BEFORE installing the system?
regards,

[JLMounce]

Originally Posted by First Bird

Hah! No. Not scaring me off. After carburetors and external fuel pumps, I'm looking forward to geeking out on sensor placement and datalogging.

Well I am scared off by the talk of FiTech being Holley now. I wanted to support the little guy but if they now ARE the big guy and will not be supported later on, gives me pause . . .

Are there any other sensors you would replace BEFORE installing the system?
regards,

HWY's post on that got a little buried. Doesn't look to be the case.

Formula, I know the FiTech doesn't even read fuel pressure and I get the feeling that neither does the sniper. What the FiTech does is read injector flow and cross references it to the o2's lamda reading.

The calculation would work something like base VE table fueling > VE modifers (coolant, IAT, TPS, MAP) > fuel flow > lambda. then the trim kicks in based on lamda and loops back to long term learn, which is a modification of the base VE table.