Hi boost misfire

[jeffp]

Well got the car to the dyno again and it is still misfiring at high boost levels. I got one good pull @ 20psi and that was it. The car had a slight misfire @ 4500 rpm's and it would go and about 5500 to 7000 it would misfire again.

I did all of the standard stuff with the plug gap and all of that with no improvements.

I tried two different type of chanpion plugs (that was all the shop had) and that did not make improvements.

I was running a 6 range plug and they glazed and began to misfire. I then went to about a 9 heat range, they did not glaze, but it did appear that they were to cold. I have tried an 8 range irridium plug, and an NGK race V-power plug in the 7 and 8 ranges.

The 8 range seems to be about the best but the misfire is still there.

I have a new ECU and the spark duration is 3 milli seconds, and we tried 4 milli seconds with no improvement either.

any idaes?

[frank280zx]

Well got the car to the dyno again and it is still misfiring at high boost levels. I got one good pull @ 20psi and that was it. The car had a slight misfire @ 4500 rpm's and it would go and about 5500 to 7000 it would misfire again.

I did all of the standard stuff with the plug gap and all of that with no improvements.

I tried two different type of chanpion plugs (that was all the shop had) and that did not make improvements.

I was running a 6 range plug and they glazed and began to misfire. I then went to about a 9 heat range, they did not glaze, but it did appear that they were to cold. I have tried an 8 range irridium plug, and an NGK race V-power plug in the 7 and 8 ranges.

The 8 range seems to be about the best but the misfire is still there.

I have a new ECU and the spark duration is 3 milli seconds, and we tried 4 milli seconds with no improvement either.

any idaes?

 

well give the car me call it quits jeff

See you in a few weeks!

 

anyhow when does your methanol injection kick in .. would that have to do anything with the misfires? just an idea!

[ktm]

Jeff, you are doing exactly what I did. Spark gap, colder plugs (7s and 8s myself as well), increasing coil dwell, etc. I still get the occassional misfire, but that could be attributed to my fueling. I don't know. Now that I have meth injection, I will lean out my map a little more and see if that helps.

 

Maybe timing? But that would show up in AFRs.

[SATAN]

When you say you did the standard stuff with the plugs, what exactly did you do. I have seen plugs that need to be gapped down to .020" or EVEN LESS sometimes. How far down did you take your gap?

[jeffp]

When you say you did the standard stuff with the plugs, what exactly did you do. I have seen plugs that need to be gapped down to .020" or EVEN LESS sometimes. How far down did you take your gap?

 

I took the spark gap to .025- .028 for this set of runs. The designer of the new system was doing the tuning during the dyno runs. So telling him that the plug gap had to be set down did not wash with him all to well.

So I called it a day and paid my money for the dyno and a set of chanpion plugs I don't want.

When Lance said he needed to test the wires and plugs in his pressure tester I decided that was the best thing to do for now, and order some plugs. I found a good site that sells the B7es-B9es standard 2.25 a plug NGK parts. I think this may be beneficial.

I have also tried the V-power race plug from NGK with little success.

So for now, I am going to go with the tests Lance wants to perform. Its cheaper that way LOL. No I really want to find out what the heck is still happening.

[jgkurz]

I took the spark gap to .025- .028 for this set of runs. The designer of the new system was doing the tuning during the dyno runs. So telling him that the plug gap had to be set down did not wash with him all to well.

So I called it a day and paid my money for the dyno and a set of chanpion plugs I don't want.

When Lance said he needed to test the wires and plugs in his pressure tester I decided that was the best thing to do for now, and order some plugs. I found a good site that sells the B7es-B9es standard 2.25 a plug NGK parts. I think this may be beneficial.

I have also tried the V-power race plug from NGK with little success.

So for now, I am going to go with the tests Lance wants to perform. Its cheaper that way LOL. No I really want to find out what the heck is still happening.

 

Jeff, A good friend of mine who owned a local tuner shop told me that he liked using the standard thick electrode (non-platinum) plugs on turbo cars. His shop dyno'd and tuned a great deal of turbo cars so I took his advice seriously. I have had great success with the following plugs depending on the situation. NGK BPR7ES plugs at .030 gap on pump gas at 15-20psi and NGK BR8ES plugs at .030 gap when I'm going all out on the dyno or track. You may need to go to a Yamaha dealer to get the BR8ES plugs. My EFI doesn't allow me to change dwell but I don't have any audible misfires or hesitations under boost that I'm aware of. Good luck.

[ktm]

Jeff, A good friend of mine who owned a local tuner shop told me that he liked using the standard thick electrode (non-platinum) plugs on turbo cars. His shop dyno'd and tuned a great deal of turbo cars so I took his advice seriously. I have had great success with the following plugs depending on the situation. NGK BPR7ES plugs at .030 gap on pump gas at 15-20psi and NGK BR8ES plugs at .030 gap when I'm going all out on the dyno or track. You may need to go to a Yamaha dealer to get the BR8ES plugs. My EFI doesn't allow me to change dwell but I don't have any audible misfires or hesitations under boost that I'm aware of. Good luck.

 

I used the BPR7ES myself at 15 psi and switched back to 6s because I was still misfiring. I thought maybe the plug was too cold. I'll switch back to 7s for pre-ignition protection.

 

Jeff, I found a great website as well for NGK plugs, its probably the same place (www.ngk.com - its not www.ngksparkplugs.com).

[Boosted_JDM]

If you want to save your engine don't use champion plugs. Stick with NGK

 

NGK R5671A-8 for about up to 20psi

NGK R5671A-9 for about 20psi +

 

Heard of these being discontinued, but I haven't have a problem sourcing them

 

BTW 6 is was too hot of a plug for turbo, if your running low boost still don't go below 7's

[jeffp]

First off, the champion plugs are gone. I did not want to use them in the first place, but that was all that the shop had. I did find a good site to sell plugs http://www.ridegear.com The had every plug I was looking for.

I was thinking along the lines of a B8es plug, but the resistor type will work good also. The plugs are cheaper then the newer plugs. I have been told the Nissan engine does do better with the wide electrode. I also have tried the NGK V-power plug and it appears to work well at more cost.

Either way, the 8 range plug appears to be the best bet.

I was also looking at the injector flow rate requirements and from what I have been able to calculate on the RC engineering site, I have just about run out of injector.

so with my fuel pressure set to 58.8psi and using their formula of .65 for the brake specific fuel consumption, 650hp desired, the injector flow rate is indicated to be 740 cc/min with the injector @ 80% duty cycle. Anyone want to verify that figure, I might be missing something.

I ran into this problem on the mustang dyno @ 489hp or so with 17psi at the wheel. The dynojet said 508 or so @ 17psi of boost.

Not to far off the measuremets.

The thing that really sticks out to me is that when the engine comes up on boost about 3200 rpm's I get a misfire at about 4500 and it goes away. Then at about 5500 or so I misfire to 7K

Now I could be wrong all together on this, but from the injector flow formula, I am out of injector to pull the power up over 600-625hp

I will speak to lance on Monday and get a better idea of what is going on. He did not indicate that there was a problem with injector sizing, and I did not think to ask him what the duty cycle was. The thing is that the wideband did not indicate a lean or rich condition, but we know that when the O2 sensor gets into a pressure state in the exhaust they start acting a little funny. It just could be that the sensor was not reacting fast enough to measure the AFR's at that level. I am running the Honda NTK sensor.

 

Now wouldnt that be a pisser, the injectors are out of juice at 625hp or so.

 

I ordered some plugs from NGK and they will be here Monday, I will also order some of the Br8ES and BR7ES plugs. I think the 8 plug will be best. The 9 heat range is to cold even for my car, and my motocycle when I rode bikes. That plug would foul fast, and looking at the plug out of my car, that plug appears to not be getting hot enough to burn off the carbon on the insulator.

So what do you think? bigger injector? maybe this was all that I was seeing last year? Really would be a pisser.

[jeffp]

So I was talking to a friend of mine about what the car was doing and the thought occured to me and him that if it is a fuel problem, no problem, I can start injecting methanol to compensate for the lack of fuel I believe is happening.

So if it does turn out to be a fuel problem the methanol will corrcect the problem. I can do this test without changing out the injectors.

 

I will have to think on this a while longer, but if that is the case, then the car will have two power levels, fast and reeeeeelllly fast.

Anyway that is what I am thinking.

[Scottie-GNZ]

Jeff,

 

both Z-Gad and I run BPR7s gapped at .022 in the 2JZs at 27+psi (30+ for Z-Gad). I absolutely endorse meth inj but do not use it as a stopgap for a problem. I would want to see you identify the problem then add the meth inj. Couple of things to consider: factor your injs based on FWHP not RWHP; Find a way to put a voltmeter on the pump(s) to make sure you have enough and stable voltage under load.

[jeffp]

I am running the fuel pump with the stock fuel pump relay. I may be losing some power there, I will have to test the relay.

I don't want to mask a problem with the methanol, but I really th8ink the engine is running out of fuel not spark. The give away is when the power curve starts coming up quickly in the 4K range I get a little misfire but it is short. That tells me it is not an air flow problem.

I have completed the fuel delivery charactorization a while back, so here is that data.

Using the Nissan twin turbo pump, the pump will go into bypass at about 90psi. I also tested the drop in pressure from the pump outlet to the fuel rail and there is about a 4psi loss through the stock fuel line (feed side) so that would make my maximum fuel pressure at the regulator be 86psi with boost.

58.8-86=27.2 so that would indicate I can run 27psi of boost. So depending on what my brake specific fuel consumption is, I have never put a flow meter on the fuel, I need at least 3300 cc's of euel a minute. I think that number is higher, but I have not worked that formula. So to test the system, supply battery vooltage to the pump @ 13.8 volts. run the system with the return line in a bucket to measure the cc's that return to the tank, this is the fuel the injectors have to use to fuel the engine.

I tested the system to 83-85psi with boost added to the static pressure of 58.8psi.

I am not all that sure the single pump is going to supply all of the fuel required for 600-650hp so when I put more boost to the engine then 600hp I don't have enough fuel for the engine, hense a "misfire" So I need to work a few formulas and do some fuel edlivery testing to make sure there is enough fuel.

But according to the rc injector formula, to run the car to 600 hp with a bsfc of .65 @ 58.8psi static I will need an injector that is 740cc's/min or 70.36 Lbs/Hr fuel injectors.

The calculation for flow is if I am correct 740cc's/min X 6 = 4440 a minute. I don't think my system is able to accomplish that task, close but no cigar.

I am also going to test the system again to make sure I have the flow I need and I also need a little head room as well.

So I have a few choices:

1) get 96Lbs/hr fuel injectors and run 43.5 static fuel pressure and that will get me to almost 700hp

2) use the methanol on the topend to get the fuel required.

3) leave it alone and run to 19psi and be done with it, and be happy knowing I still have at least 5 psi of boost left in the turbo.

The lower fuel pressure will save me an additional fuel pump to get the correct flow at the fuel pressure under boost.

so that is what I was thinking. What do you think?

[Scottie-GNZ]

While the logic in your formulas make sense, the flaw is what happens to that pump at 86psi. IMHO, you already have one bandaid, i.e., running 58+psi FP. With that, I would point my finger at the single pump trying to provide the required fuel @ 86psi with only 13.8V. I am willing to bet if you wired up a voltmeter on that pump at 86psi, you are lucky if the pump is getting 12.5V, especially with the stock fuel pump relay. My guess is the pump is probably supplying no more 175lph under those conditions.

 

Do not believe that because you have 72# injs and the formulas say it should work, that it will. Ask me how I know. I struggled for a while with a similar problem and Z-Gad can attest to it as he was scratching his head also. I would instantly go lean at high RPMs with my 72#ers. Never thought it was the injs because I was not making enough HP to max them out with the alky and the DC was in the high 80s and I run dual in-tank Walbros. Bought Z-Gad's 96#ers and the problem went away.

 

You still have not said if the 650hp you refer to is RWHP or FWHP. No way you are going to get a single pump to support that w/o a volt booster. At your boost and power levels, here is what I advise, based on my experience. Go to 96# injs. Install a 2nd pump. If your return line is smaller than -6, install a 15# pressure switch in the compressor housing to turn on the 2nd pump. Too small a return might cause an issue at idle with both pumps on. Ditch the stock FP relay and install a seperate relay for each pump with 10g + & - wiring. Use the 30 off the stock relay as the trigger for both new relays and run the ground for the 2nd pump relay through the pressure switch. Set the FP back to 43 and the boost to 20psi and start from there.

 

Yes, this is exacltly how I have mine set up. Now at an estimated 840 at the crank, my inj DC is in the mid-60s with 43# static + 27psi. Of course, that is result of approx 20% of what is being ingested being meth and the engine loves it especially when going thru the traps at full boost with an IAT in the mid-hi 80s. OK, OK, I love meth but you get the point.

 

I might be off base with your problem but it just sounds too familiar to what I struggled with.

[Six_Shooter]

Scottie-GNZ:

 

Do you have any sort of a check valve after the secondary pump? I have thought about doing something similar, but was a little worried that pressure would bleed off through the pump that is off.

[Tony D]

Japanese have used multiple pumps for years. Each pump should have it's own discrete in-body check valve, and unless you are spending real $$$ adding an external check valve may cause more problems than it solves, especially as it relates to fuel flow.

 

MSD Boost-A-Pump...hmmmm

 

I think someone mentioned dual pumps, 1100CC/min injectors, and some stainless steel repiping of the fuel system on the phone some hours ago...muahahaha! "Every time I call you it costs me $2000!" No problem, just go to the money tree and pick some more! LOL

 

Jeff has the power he wants (Anybody else recall 'all I want is 600 flywheel horsepower and I'll be happy'?), he's just getting greedy now!

 

Bwahaha!

[jeffp]

As Tony said that is where my brain was going. 96Lbs/min injectors. That will set my static fuel pressure to 43.5psi at idle then the boost of 25psi. The Nissan pump should be up to thattask, but I am going to check it. I think if memory serves me correctly, the nissan pump is delivering excellent fuel flow quantities. I have a big cc flask at work that will do the trick for the test.

The fuel pump relay, I agree, it just may be time to get a better part. Scottie, I ran down that road a number of years ago with the dual pump setup. The thing that stopped me from doing it was the fuel delivery at pressure levels higher then 75-80psi of line pressure. All of the pumps I looked at had a top of about the 75-80 psi and the flow rate would go off a cliff and die.

I will look into the 96lbs/min injectors. I m not sure what idle will be like though. That would solve my problem.

Greedy, I don't think so Tony, I have the air available, and from my sensors, when the car is heat soaked the mat is telling me the air is 67 degreesC not to bad for an intercooler that is sized on the small size for this build. I want to run the boost to the limit. so with an additional 5psi of boost, the engine will be very close to 700hp at the crank. The 537 figure was at the wheel, so that puts me right at 617hp with the 15% drive train loss figure. Not to bad, for a street car. If you got it, use it. Hooking up the tires is an all together different story, but we will see what the wrinklewalls do for traction.

Anyway, I have pugs on order, and I will speak to Lance today about the larger injectors, and try to complete the flow testing. 4500cc's should do the trick, and if not, then I will consider the second pump, what a pain. I thought the fuel delivery was good enough, and last time it took some engineering to get that system correct.

Anyway lets see what happens.

[Tony D]

Greed is a sin, gawd will punish you for your pursuit of opulence.

 

If you crack a Moosehead and it's skunky...it's a sign!

 

LOL

[frank280zx]

 

Three Fuel pumps, filter and swirl pot, these are in the spare wheel well… what do you have there now jeff

[Scottie-GNZ]

Even though you are talking FWHP, I would still be leery of running a single pump @ 70+psi w/o a volt-booster. As you said, most pumps fall off above 75psi and the answer is to throw more voltage at them or a 2nd pump. If you definitely have meth-inj in your plans, then I would stay with the 72s, add a volt-booster to the pump and see how far that takes you. Whichever route you take, do not bank on that single pump providing more than 200lph w/o a volt-booster.

[jeffp]

I agree Scottie, pushing a single pump that hard will not be the best option. The voltage booster is an option, and MSD sells one of those boxes.

Realistically if I get a flow rate of 4400 cc's a minute then I should have the flow I am looking for.

So here is the plan, I spoke to a number of people and the common fix was a second pump, we will see about that. In the mean time I am going to see what I get with the single pump at 69psi and thatwill tell me which way I really need to go. that is 3 BAR 43.5 plus 25psi of boost. That is where the rubber meets the road.

I have all my test bottles ready to do the test today, so I will post the results tonight.