Jump to content
SAU Community

Recommended Posts

An atmo bov will increase the backfires as its venting air to the atmo instead of back into the air intake making the afm compensate with more fuel, which means car runs richer and backfires. It used to happen on 90% of my gear changes so I got rid of the atmo bov and went back to the std one, though when I downchange at 3000rpm or more it backfires too. Need to get an SAFC to lean it out a bit.

Ive always had it, figured the aftermarket ECU caused the majority of them. Then i got an atmo BOV and its increased slightly, probably hear 6 or 7 in an hours worth of driving. Doesnt really do any harm. ALOT of turbo nissans do it with aftermarket exhausts.

But if its doing it on 90 percent of your gear changes then thats just ridiculous.

And its not strictly a backfire in my opinion.... backfires cause people to hit the pavement (see Uncle Buck).... Skylines seem to just make nice snap crackle pop noises.

Red17

yep, i believe that this 'backfiring' as described is actually 'over-run'. I think it has something to do with the fluid (exhaust) flow through a pipe and the effect of massive changes in flow velocity as you change gears (i.e very fast gas flow to much slower)... sort of a reverberation within the pipe. This happens more with aftermarket exhausts due to the increased diameter resulting in a greater flow speed differential. Of course if your mixtures are rich then this will also cause exhaust noise as the unburnt fuel is ignited outside the combustion chamber.

This is only a guess, but i think it is reasonable given the aerodynamics i studied through my (unused) mechanical engineering degree... feel free to correct me if i'm wrong.

OK...youve given me some ideas...thanks.

Some great theories, and it's intriguing that others suffer the same problem.

It is actually a popping noise, rather than a backfire, still, it is a bit distressing. Is it damaging though ??

I do have an aftermarket exhaust...a Kakimoto NS309....but the problem has only recently started....possibly after I was stuffing around with the BOV tension.

I might try tightening up the BOV (an atmo) and see if that has any effect.

cheers Ozzy

same here ED!

The Skylines are known to run very rich. Up the boost and the ECU over compensates even more. Mine is starting to sound like a rally car on the up changes ( running 0.9 bar ).

Could be wrong but I definately though it was unburnt fuel from running too rich.

BUT it sounds COOL...RIGHT???

Maybe not 90% of your driving time tho, that'd be a little annoying! I can get mine to back fire any time usually, just nail it and the back off real quick, if no back fire, lightly tap the Loud Pedal and you should hear the fruits of your labour.

I think my plugs need replacing now, but that's OK...

Yeah its just a pop, not a huge backfire... yeah its cool, there is one corner on the way home if I get the green light I can wind it down from 80km/hr to around 40km/hr and drop it into 2nd and I got a nice pop out the back... I suppose if I had a dump+front pipe and no cat I'd get flamage :P

I bet if you put the standard BOV back on you wouldn't hear a sound...

Yes the ECU expects an extra burst of air from the plumb back which is expelled from the intake system, so it compensates for this by adding fuel. This also solves the mystery of why some after market BOV make your car stall (over fuel).

A mate of mine solved this by installing an AVO atmospheric/plumb back BOV (all in one).

But if you don't mind the sound, forget about it, it's doing any harm.

Have Fun.

Yesiree, it is mine.....thanks....I think it looks good too. It came from Japan like that....I believe it is a standard factory R33 GTR bar.....Its good in several ways....you can remove the bottom lip when its been scratched to hell and repaint it off the car....(the beast has Tein's all round and is set on the stops)....it also allows you an absolute shirtload of room for a FMIC....which will come when the MRS lets me spend some more (of my) money.

cheers Ozzy

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • I also don't mean to rain on your parade. But with a 5-10k budget for road only? I'd want to check confirmation that everything IS working correctly and I'm with @GTSBoy for a plan of action here. I'd be checking subframes, bushes, exhaust hangers, interior bits and generally QOL things and CONFIRMING they are working right before thinking about motor. You can get 250KW+ on stock RB26 hardware by simply removing the built in restrictors and tuning the stock ECU. If you want purity that's as far to take it, which I would be worried to do and won't think the budget would allow for when earnestly checking for 30+ year old car stuff.
    • I specifically said buy new performance car because of the use case here (i.e, no track use and fun livable everything/do it all easily if not especially amazing as a drivers car). Tracking an 80K Skyline and an 80K M2 makes the BMW the obviously more risky purchase WHEN something goes wrong you suddenly can't easily fix it with hand tools and readily available parts that you may have a community of people you know available, or years of your own knowledge on the platform to apply. There's reasons you see Hondas and Vettes and RB's and Miatas and such at tracks, you can easily hand-tool repair 99.9% of it in a shed, usually with the tools and the skillset of the owner to apply to it. An i30N is not going to beat a R chassis unless it's got massive problems either. The old cars can, and still do work great. The problem is - and always has been - social media would have you believe it's simple and easy to achieve the results you see online.  People want their car to be like "one of those cool JDM cars" which is the default image people have when they think of  "cool JDM cars" You are paying 25 years of catchup R&D to achieve. Or the knowledge somebody else has to do it for you, which is big dollar restomod stuff.  The bar has been moved and every R chassis that people see/like/enjoy has 25 years of R&D thrown at it, or is owned by someone who did all that work and has that knowledge over the past 25 years. All the survivors have been progressively resto-modded the entire time. OR you slowly bring it back to how it was stock. Which is also prohibitively expensive, done for the love of it. This is what the JDM community is now. This is fine, but "Where do I start?" is either: 1) Don't 2) Take your own slow journey but you cannot compare your progress with others who have had 25 years of R&D and experience building their own cars unless you pay for it.
    • Yep, with the crazy inflation of the value of our cars these past couple of years this became a problem for me too... My solution is to transition to bikes. Everything feels so cheap compared to tracking the skyline lol
    • So, I've been a little busy on this car. I replaced the bonnet struts which is always satisfying but very confusing that nobody else on the planet seems to do this. Its just my routine first thing I do on any car I buy. The boot struts for both the tailgate and the separately opening glass window was a bastard. And, I found a fair bit of rust in the strut cavity. I filled it with rust converter and cleaned up as much of the dirt as I could. There was so much dirt. One piece of the trim was barely hanging on and so I've left it off. I'll try to get a replacement. You can see how disgusting and dirty it all was in this thread; I had to remove the little clips that hold the struts on the ball. The ones I took off had no clips and it was impossible to get them on with them in place. Fingers crossed they stay put. So, I turned my attention to the headlights, they were in a bad way and likely would stop rego. I took the headlights out and found the adjusters were all just loose. So, I fixed those and unclipped the lenses to clean them up. Couldn't believe how easy it was to take all this apart compared to the E90.   I also cleaned up the stockies which was awesome, these are super cool with lug nut covers. They're in good nic but the tyres are shot. I was going to use these for rego but in the end got a fresh pair of rubber for the 17's on the front of the car instead. The front bar of this car is from a late(r) model one. I don't think it's quite LCI but who knows. I'll need to find out. Anyway, the bar was missing the fog lights and the wiring and plugs were for the original ones so I got new plugs and some cheap fogs. I wasn't sure if missing original equipment would hamper my blue slip attempts. Had a couple of these little fellas helping out. But not Ben who got stuck behind the pool heater .... How embarressment.  I ordered new speed sensors for all corners because I knew one was out. I just got cheapies and will replace them with Bosch items when I can find Bosch items. Again, this was just for rego. Alas, it seems the blue speed sensors are not the same as the grey ones. Back they went and replacements ordered. In the end, with my new scan tool, it was just rear left that was shot. Replaced it and cleared the codes. All good now. Lastly, my aux (thermo) fan is being a bit odd. Its powering up at strange times and NOT powering up when I think it should (100C). While this can be caused by a few things, the most likely (for me) is the ambient temp sensor. Given mine reads -40.0C regardless of the temp, I figured it would be good to replace it. In the end, the sensor wiring was abysmal with (terrible) attempts made by somebody to fix it.   I fixed this all up but the sensor is only attached using pins into the wires. The plug is not there. Despite trying and trying to connect it securely it wouldn't work so a replacement sensor and plug is on the way. Oh, I also ordered a replacement piece of trim for the part missing here at the bottom. Ordered from Latvia for $70 delivered. I took a bit of a leap of faith because I didn't have the exact part number and, as usual, there were eleventy billion pieces of trim that looked to fit. Nailed it. Well, its not totally perfect but I think its more a 28 y/o car problem than a trim problem. And, as of today ..... I have bought the workshop manuals 2nd hand off a guy in tassie. 1000+ pages of E39 goodness, hopefully it helps me with the fan. I also have a new temp switch on the way incase its the problem. Stoked.
    • I don't even know that you want an M2 Competition as a track car. My rule for a track car is only risk as much as you're willing to completely total out. Clean stock C5 Z06 Corvettes out here are cheap. Buying someone else's already ruined track car is even cheaper. Maybe I'm just not that good a driver but even a Fiesta ST on the Nordschleife felt like as much car as I could realistically handle.
×
×
  • Create New...