RB25DET backfiring at high rpm full throttle

[Eric0]

4 hours ago, KiwiRS4T said:

So your car is not sitting on a dyno? The tuner is just playing with the maps? Do not gap your new plugs at .02 go to 32 thou (.8mm or .032 in)

The fuel controller is the ecu so if you reckon the pump and fpr are fine that just leaves the injectors so as Murray says what kind are they and could they need cleaning and testing?

Do you have any idea what the duty cycle is on the injectors? I still think your tuner does not know what he is doing.

The  car was on the dyno but is now home. It drove home fine but it hiccuped on high rpm so I thought spark plugs. Once they were changed, it did the same and backfired. I’m still waiting for him to verify my tune. 

[Eric0]

4 hours ago, KiwiRS4T said:

So your car is not sitting on a dyno? The tuner is just playing with the maps? Do not gap your new plugs at .02 go to 32 thou (.8mm or .032 in)

The fuel controller is the ecu so if you reckon the pump and fpr are fine that just leaves the injectors so as Murray says what kind are they and could they need cleaning and testing?

Do you have any idea what the duty cycle is on the injectors? I still think your tuner does not know what he is doing.

The fuel pump is a 550 walbro and it is brand new as well. I’m not sure what an FPR is, could you inform me? Everything on the car is brand new, even the ECU. 

[KiwiRS4T]

6 hours ago, Eric0 said:

The fuel pump is a 550 walbro and it is brand new as well. I’m not sure what an FPR is, could you inform me? Everything on the car is brand new, even the ECU. 

FPR is the fuel pressure regulator and not a likely suspect. The injectors may be old school or modern ones (Deatsworks don't make them they just rebuild them) but if new should be ok.  After the new coils are installed,  and please confirm you are not going to gap the plugs down to nothing (0.02in) - you just need a tune. What does "verify your tune" mean? Will he have access to an AFR meter, knock detector etc? If you are right about your current afr levels then yes you are running lean enough to damage your engine.

[Murray_Calavera]

7 hours ago, Eric0 said:

The fuel pump is a 550 walbro and it is brand new as well. I’m not sure what an FPR is, could you inform me? Everything on the car is brand new, even the ECU. 

FPR is a fuel pressure regulator. 

I just quickly re-read your posts again, you mentioned that your AFR is around 14-15 on 'load'. Originally I interpreted that as light cruise, is that what you meant or is it 14-15 AFR on full boost? 

Re your injectors, yes you have terrible injectors by today's standards, if your not running E85, that explains your idle mixtures. 

Have you fitted the new coil packs yet? 

If it is the case that your mixtures are extremely lean, (14-15 AFR on 'load'), you are approaching the realm of lean misfires. While I wouldn't expect a lean misfire at 15 AFR, a mixture of 16 AFR wouldn't surprise me that it was backfiring/misfiring. 

I think the primary concern at this stage is the state of tune, til that's answered it's hard to know where the real problem is. 

You asked should you be driving this car? Well if it's running that lean I wouldn't drive it.

Also, what are the odds you'd be able to upload your ECU's map? Would only take me about 20 seconds to tell you if the tune is so bad that it's a tune issue rather then a coil issue. 

Edited September 17, 2019 by Murray_Calavera

[Eric0]

2 hours ago, KiwiRS4T said:

FPR is the fuel pressure regulator and not a likely suspect. The injectors may be old school or modern ones (Deatsworks don't make them they just rebuild them) but if new should be ok.  After the new coils are installed,  and please confirm you are not going to gap the plugs down to nothing (0.02in) - you just need a tune. What does "verify your tune" mean? Will he have access to an AFR meter, knock detector etc? If you are right about your current afr levels then yes you are running lean enough to damage your engine.

Yes, my fuel injectors are new new. I suggested I gap my plugs at .032 and my tuner said he prefers .02 with his tune. My ecu is stand-alone so he will have access to the AFR I believe. It can be wirelessly tuned so by “verifying” I mean he can access my ecu’s memory and check if everything is looking good. The car had been on the dyno and he said it was good but now that this is happening he’ll wirelessly remote the ecu after I install new coils and plugs to .02 (he insist on it).  

[Eric0]

2 hours ago, Murray_Calavera said:

FPR is a fuel pressure regulator. 

I just quickly re-read your posts again, you mentioned that your AFR is around 14-15 on 'load'. Originally I interpreted that as light cruise, is that what you meant or is it 14-15 AFR on full boost? 

Re your injectors, yes you have terrible injectors by today's standards, if your not running E85, that explains your idle mixtures. 

Have you fitted the new coil packs yet? 

If it is the case that your mixtures are extremely lean, (14-15 AFR on 'load'), you are approaching the realm of lean misfires. While I wouldn't expect a lean misfire at 15 AFR, a mixture of 16 AFR wouldn't surprise me that it was backfiring/misfiring. 

I think the primary concern at this stage is the state of tune, til that's answered it's hard to know where the real problem is. 

You asked should you be driving this car? Well if it's running that lean I wouldn't drive it.

Also, what are the odds you'd be able to upload your ECU's map? Would only take me about 20 seconds to tell you if the tune is so bad that it's a tune issue rather then a coil issue. 

The attached image is the base tune i drove on to break the engine in. The car drive perfectly without issues. But I didn’t capture the final tune to show you. 

[Eric0]

Just now, Eric0 said:

The attached image is the base tune i drove on to break the engine in. The car drive perfectly without issues. But I didn’t capture the final tune to show you. 

Also, this image wasn’t the end of the tune. The base tune stopped at 300hp flat. 

[Murray_Calavera]

7 minutes ago, Eric0 said:

Yes, my fuel injectors are new new. I suggested I gap my plugs at .032 and my tuner said he prefers .02 with his tune. My ecu is stand-alone so he will have access to the AFR I believe. It can be wirelessly tuned so by “verifying” I mean he can access my ecu’s memory and check if everything is looking good. The car had been on the dyno and he said it was good but now that this is happening he’ll wirelessly remote the ecu after I install new coils and plugs to .02 (he insist on it).  

You can still buy the old dinosaur DW injectors brand new new. 

When I say they are old, I mean old design. As in, they are side feed injectors that are essentially milled stock injectors. Modern injectors are a much better design. 

On the plus side, your mixtures don't look bad on those runs. 

If your car is making 300hp, I can't believe your spark plug gap even came up in discussion. I would bet there are many people running around on factory spec plugs without any issues at all at that power level. 

Please post back with results after you have replaced your coils. 

[KiwiRS4T]

24 minutes ago, Eric0 said:

 after I install new coils and plugs to .02 (he insist on it).  

Your afrs as per the above chart don't look too bad. But regarding plug gap your tuner is flat out wrong. Factory is 1.1mm or .043 inches and people with beefed up ignition systems can run that gap ok. With Splitfires and a decent amount of boost  gapping down to 0.8mm or .032 inches works ok.  But .5mm is getting ridiculous. There are literally thousands of RBs running in Australia and New Zealand and tuners have over two decades of data to work with and I don't think you would find one among them who would think you should gap down to .5mm

Also remotely accessing your ecu and playing with the maps without any monitoring equipment is not proper tuning.

[Ben C34]

just to clear things up a bit, hopefullly, a tight gap wont cause problems but it shouldnt be required for the amount of power you are making.

.5 mm spark plug gap isnt worthy of the concern on its own. It seems like its the worse thing ever reading through this thread. plenty of guys run that sort of gap when required.

[GTSBoy]

6 hours ago, Ben C34 said:

just to clear things up a bit, hopefullly, a tight gap wont cause problems but it shouldnt be required for the amount of power you are making.

.5 mm spark plug gap isnt worthy of the concern on its own. It seems like its the worse thing ever reading through this thread. plenty of guys run that sort of gap when required.

Yeah well.....sorta.  But we're at opposite ends of the same problem here. If the gap is too close you don't get as much energy out of the spark. And there's also a need for the gap to be large enough to actually expose enough mixture to the spark. That's why big gaps are great, when you have the power to drive them, because you get a big spark that sees lots of mixture.

The other end of the problem is where the gap is too large for the ignition system energy available to jump through the dense mixture of a high boost engine. And you get no spark at all. Either way, you get a misfire.

I would agree that 0.5mm is not waaaaaay too small. But it is getting so small that it is clearly not the right thing to do.

[Eric0]

Hey guys! I hope you’re all doing well. Just a quick update. I ordered coilpacks and learned that the s1 has internally built in ignitors and s2 doesn’t. I didn’t know that after I purchased the coilpacks so the attached image are the ones I ordered. Are they looking like the right ones? They are on back-order and won’t be shipped till 5-7 more days, unfortunately. But perhaps fortunately if they’re the wrong ones for my engine. 

My CAS was just painted, I read online that’s a good indication that it’s a series 1, plus I only have the coilpacks harness without the rear box usually found in series 2.

Thank you! 

[GTSBoy]

3 hours ago, Eric0 said:

I ordered coilpacks and learned that the s1 has internally built in ignitors and s2 doesn’t.

No. That's the opposite. Early ones (RB20s, S1 RB25s) have a separate ignitor pack. Later ones are integrated.

[KiwiRS4T]

Without knowing for sure which engine you have a good way to check if you have the right Splitfires is to ensure that the bolt patterns are the same as your stock coils. Look at the link below. You will be needing either DIS 001 or DIS 005 and you can tell by looking at the bolt pattern - one has three bolts, one four.  Whichever has the same bolt pattern as yours is the correct replacement.

https://driftsideracing.co.nz/split-fire-ignition-coil/nissan-skyline-ignition-coils-dis-001.html

[DQB]

-change plug gap to 0.9-1.0 mm because too small can not ignite all of the fuel - smaller stands up to more boost physically only

(think of a birthday candle and a harder blow is more psi)

-call your tuner and tell him to tune your car properly and stop running so f**king lean

-do you run ~400hp at 15 AFR? I don't believe that you know the "final tune" without taking pics yet you have pics of your "base tune" If so repeat above point with added profanities, if not then we need pics of the actual tune you're using not irrelevant bullshit

-rb20det = coilpacks w/ ignitor pack (NOT built in)
-rb25det s1 = coilpacks w/ ignitor pack (NOT built in)

-rb25det s2 = coilpacks w/o ignitor pack (built in)
-Buy some proper injectors not the retarded 90s shit
-Or ignore all above and stop being a pussy scared by a pop noise, belt the piss out of it and buy another when it leans out and f**ks you over because of your idiotic tuner

[Ben C34]

Settle down!

[Dose Pipe Sutututu]

Lol..  the AFRs look fine in the graph, in the 11 range.