Missing @ 35 PSI

[TerryLiv]

I posted this on another board and someone suggested I try a different ignitor. Anyone North of Denver have one I could borrow? I would pick it up.

This is for a 1G, E-85, big injectiors and enough fuel.

I am hearing, seeing on my logger and feeling random missing above 5500 RPM. Starts happening at about 30 PSI and is worse at 35 PSI of boost. I am running stock ignitor & coils, a Dynatek ARC-2 CDI box, new NGK wires & 7 and 8 NGK plugs (but not at the same time). It would miss slightly at 27 psi and 0.028" gap and more miss at 32 PSI, finally at 0.020" gap at 35 PSI it was even worse.

This occurs from lean to rich, so I feel confident it is not fuel related.

The wires are isolated in 1-4, 2-3 pairs away from any metal in stock plus aftermarket plastic/rubber looms. I have been working on correcting this for about 3 weeks, and now after adding the new wires I am thinking I don't know Marco's secret plug wire isolation technique.

Any further suggestions appreciated. If your suggestion is COP, offer suggestions as to where to buy from.

Thanks,

Terry

[D Walker]

Whats your IAT's? Edit- thought you were someone else, but what are your IAT's?
.020 is likely too small a gap for complete combustion, especially with E85 and the volume of fuel you are injecting@35psi.

I have stock ignitors and coilpacks, as well as the COP ignition system I build.

EDIT again- what year 1G and which ECU are you using?

[yokotabrat]

I'm in Northglenn and have an extra ignitor you could try.

[mpdeneen]

I'm in Northglenn and have an extra ignitor you could try.

I'm in fort collins and I can pull the one off my 1G, as long as I get a ride...

:D

[TerryLiv]

Don,

Thanks for your reply. I have tried plug gaps from .017 to .035 with and without the ARC-2 CDI unit. I will try .028 again tomorrow.

I don't have a temperature sensor after the turbo, but these are second gear pulls that last about 3 seconds, so in the winter it probably is cool enough.

My car is a 91 AWD with a stock ECU and keydiver chip.

Where did you get the 3 pin connector from that you used on your COP system. Do you have any problems with missing at 35 PSI in your car with COP?

Terry



Whats your IAT's? Edit- thought you were someone else, but what are your IAT's?
.020 is likely too small a gap for complete combustion, especially with E85 and the volume of fuel you are injecting@35psi.

I have stock ignitors and coilpacks, as well as the COP ignition system I build.

EDIT again- what year 1G and which ECU are you using?

[TerryLiv]

I'm in fort collins and I can pull the one off my 1G, as long as I get a ride...

:D

Don,

Thanks for the offer. When would be a good time for me to meet you for the ride and to borrow the igniter? I should only need it for 1 day.

Terry

[TerryLiv]

I'm in Northglenn and have an extra ignitor you could try.

Bert,

Thanks for the offer. I am taking the other offer since he is so close. I have been hoping I could get to meet you in person soon. Our paths have crossed (via posts) for the past 8-9 years. I believe you lived on the West Coast when I lived in Portland. How are you liking your Speed Density installation?

Terry

[D Walker]

I usually buy the connectors new from my Tyco/AMP distributor, otherwise you can probably just use a coil or AC connector. Havent seen any issues with the COP at over 35psi.

Do you know what your fuel pressure is at 35psi manifold pressure? There is an off chance that if you are not running enough fuel pressure or are having injector issues with bad atomization when at higher boost levels.

Don,

Thanks for your reply. I have tried plug gaps from .017 to .035 with and without the ARC-2 CDI unit. I will try .028 again tomorrow.

I don't have a temperature sensor after the turbo, but these are second gear pulls that last about 3 seconds, so in the winter it probably is cool enough.

My car is a 91 AWD with a stock ECU and keydiver chip.

Where did you get the 3 pin connector from that you used on your COP system. Do you have any problems with missing at 35 PSI in your car with COP?

Terry

[dsm_gsx97]

How are you liking your Speed Density installation?

Terry

I was hoping you two would end up talking about this :D

...and just a heads up Terry that Don is in Aurora and that was mpdeneen that was in the Ft. Collins area.

[mpdeneen]

Don,

Thanks for the offer. When would be a good time for me to meet you for the ride and to borrow the igniter? I should only need it for 1 day.

Terry

Hey Terry,

Anytime after 5 or so would work. I'm going to pull it of my running engine, which is down for other reasons. PM me or give me a ring at nine seven zero 481-3317...

-Mike

[TerryLiv]

I usually buy the connectors new from my Tyco/AMP distributor, otherwise you can probably just use a coil or AC connector. Havent seen any issues with the COP at over 35psi.

Do you know what your fuel pressure is at 35psi manifold pressure? There is an off chance that if you are not running enough fuel pressure or are having injector issues with bad atomization when at higher boost levels.

Don,

I had not considered that as a potential problem. I have been (and still am) running 30 PSI base fuel pressure, but now that I have added another 255 in parallel in the tank will be upping that to 45 psi since I now have enough fuel flow. I haven't been able to up it yet as my chip burner is at Moates for repair. Maybe soon.

I will try today to see if I have enough adjustment in my SAFC to correct for higher base without changing my chip.

Thanks,

Terry

[TerryLiv]

I was hoping you two would end up talking about this :D

...and just a heads up Terry that Don is in Aurora and that was mpdeneen that was in the Ft. Collins area.

Chris,

Thanks for noticing my error in Naming. I am glad that Don noticed and, Mike, please accept my apologies.

Terry

[v413nc3]

Terry, my ARC2 and COP doesn't misfire all the way to 50PSI on E85. I run a 29 gap. I would keep an eye on your fuel setup like Don suggested. Perhaps you're not getting the pressure you think you're getting.

[TerryLiv]

I usually buy the connectors new from my Tyco/AMP distributor, otherwise you can probably just use a coil or AC connector. Havent seen any issues with the COP at over 35psi.

Do you know what your fuel pressure is at 35psi manifold pressure? There is an off chance that if you are not running enough fuel pressure or are having injector issues with bad atomization when at higher boost levels.

Don,

Another question. Did you have any missing problems @ 35 PSI before the COP or did the COP come before operating at 35 PSI +?

Thanks,

Terry

[D Walker]

I have had no missing issues with the ARC2 with OEM coils or with the COP.

FWIW please remember than when you use two pumps inline you do NOT double the fuel flow rate, at best you get 1.5 times the rate of a single pump. This is why it is better to run pumps in parallel rather than in series. Please check your fuel pressure at 35psi using an accurate fuel pressure gauge, and remember that you will need to check this pressure not with an air hose at the FPR and the engine not running, but at RPM and actual 35psi boost pressure.

[v413nc3]

As a matter of fact two pumps in Parallel can handle higher pressure feeding than a single larger can.

[yokotabrat]

Bert,

Thanks for the offer. I am taking the other offer since he is so close. I have been hoping I could get to meet you in person soon. Our paths have crossed (via posts) for the past 8-9 years. I believe you lived on the West Coast when I lived in Portland. How are you liking your Speed Density installation?

Terry

No problem. Mike D is a good guy.

No west coast for me. I've been in Colorado since 95 and before that I was in Japan. We have talked a few times over the years via email since you've been in Colorado, though.

Speed density is going great! I love it. I'd be more than happy to show you or anyone what all is involved with it. With the software being free, the cost to convert is pretty low. Since it sounds like you have a burner, it would be pretty easy for you to do.

[TerryLiv]

I have had no missing issues with the ARC2 with OEM coils or with the COP.

FWIW please remember than when you use two pumps inline you do NOT double the fuel flow rate, at best you get 1.5 times the rate of a single pump. This is why it is better to run pumps in parallel rather than in series. Please check your fuel pressure at 35psi using an accurate fuel pressure gauge, and remember that you will need to check this pressure not with an air hose at the FPR and the engine not running, but at RPM and actual 35psi boost pressure.

Don,

Thanks for the advice. I do have my pumps in Parallel, and understand the fueling relationships very well. I have measured fuel flow at idle at 30, 65 and 100 psi base pressure with one pump and at 30 psi and 52 psi with two pumps. They flow as would be expected. My fuel calculator tells me that at 35 PSI boost & 30 base = 65 total, I need about 310 LPH of fuel. At 65 PSI total fuel pressure my single 255 pump puts out about 270 PSI, and two put out about 400 LPH. The reduction is affected by my stock fuel lines.

Since I don't have any boost leaks and my AFPR works fine, I don't see a reason not to believe I am seeing 65 PSI of fuel pressure at 30 base + 35 boost. I have measured the fuel flow at the rates above and they are reasonably accurate.

I don't see a significant O2 narrow band voltage (no wide band yet) reduction at boost compared to off, so have no reason to measure actual fuel pressure inside the cab while at 35 psi of boost.

Thanks for you help with this matter. I think I am closer to the solution.

Terry

[D Walker]

The reason you need to watch your fuel pressure is because of the pressure ratio between manifold pressure and rail pressure. We all know what you need is a 1 to 1 increase, supplied by the FPR, and for every one pound of boost pressure, the fuel pressure will be raised by one pound.
For example-
I use a base pressure of about 43-45 psi at atmospheric pressure plus 58 psi of boost =
101.5 psi of rail pressure will be needed at 58 psi of boost to maintain a pressure ratio of 1:1 across the injector.
This must be done to keep the same amount of fuel flow from the injector at all times. The positive manifold pressure has a negative effect on fuel flow at the injector tip. This is why you must keep a 1:1 pressure ratio, especially at higher levels.
We get a bit screwed up up here because our atmospheric pressure is usually a bit below the 0 line, around -2.something. Since most gauges measure in differntial pressure rather than absolute pressure, our readings are a bit off if this isnt accounted for.

BTW- some fuel pumps (and Im not sure the Walbros fall into this category since they have been used with good results in similar applicationa, but Im sure it could be figured out) internally bypass at over 100psi, and some pumps when used in multiple pump setups with plumbing issues will actuall bypass or stall at lower flow/pressure rates.
Sorry if I seem to be rambling, its been a long day.

[TerryLiv]

BTW- some fuel pumps (and Im not sure the Walbros fall into this category since they have been used with good results in similar applicationa, but Im sure it could be figured out) internally bypass at over 100psi, and some pumps when used in multiple pump setups with plumbing issues will actuall bypass or stall at lower flow/pressure rates.
Sorry if I seem to be rambling, its been a long day.

Don,

The intank Walbro's have a pressure relief valve that begins bypassing fuel at some level. (Not true with the inline 392 model) Some say 75 psi, others higher. I overrode this feature on my walbro 255 and have seen as high as 115 PSI of fuel pressure before the engine died of overfeeding. I haven't seen any difference in action between my two parallel mounted pumps at low pressure (30 PSI). I have tried this with 1 pump running and with 2 pumps running. With 2, at off boost conditions however, my stock return line gets overrun.

Terry
91 AWD

[99mitsuspyder]

Here is a shot in the dark.. Check your injectors. The notorious black goo was causing this in my car for along time. Its worth a shot.

[TerryLiv]

Here is a shot in the dark.. Check your injectors. The notorious black goo was causing this in my car for along time. Its worth a shot.

Thanks but I don't think it is worth pulling them They are New FIC BlueMax 1650's and have about 200 total miles on them now.

Terry