Loud Bang From Zorst

[Tbetts]

Hey Guys,

Ok so I'm reasonably new to the jap car seen and need some advice and please forgive the ignorance.

So when my car is under heavy acceleration I get a loud Pop/bang from my exhaust when up shifting in the higher rev ranges 5k+.

The only mods i have done engine wise is a 3inch turbo back stainless steel system with a massive jun-bl cannon on the back courtesy of Exhaust Technology and a Apexi power intake pod.

The Exhaust specs are , 3inch bell mouth dump and front pipe into a 100cell cat (unsure what brand) then to a single mid mount lukey oval muffler and then straight to the Jun-bl Cannon ( dunno actual sizing but it was the biggest one there)

O and by the way the Car is a R34 Gt-t sedan with a trip tonic auto trans. ( i know a trans conversion is on the cards but not right now).

So yeah is this normal it doesn't happen all the time just when its under load and only if i don't take my foot off for the gear change.

Please Help and thank you

Tom.

[xALmoN]

no cat?

[GTSBoy]

He said a "100 cell cat".

Anyway, an upshift backfire is not uncommon on auto Skylines, especially with a big exhaust. Not normally a really loud bang though. Usually just a sexy little pop thud. My R32 used to upshift dead on the rev limiter (while it was still auto) and the sound was the only good thing abotu the auto.

[Tbetts]

He said a "100 cell cat".

Anyway, an upshift backfire is not uncommon on auto Skylines, especially with a big exhaust. Not normally a really loud bang though. Usually just a sexy little pop thud. My R32 used to upshift dead on the rev limiter (while it was still auto) and the sound was the only good thing abotu the auto.

Yeah I was hoping it was just that I googled it before and it's came up with alsorts of stuff about transmission mounts on the way out.

Thanks man

[xALmoN]

lol, i had bangs on my old R, but that's because i had a decat.

[Sunkist]

there could be a leak in the exhaust system somewhere.. that causes bangs.

[bubba]

It's probably due to the ECU cutting IGN briefly on the shift.. means you get a bit of unburnt fuel into the hot exhaust which goes bang..

[Tbetts]

there could be a leak in the exhaust system somewhere.. that causes bangs.

Gahh i would hope not i got it less then a month ago lol

And yeah its been there since i have had the new zorst put on But its got louder which i put it down to Carbon build up Still makes me abit nervous.

And with the Ecu that definitely sounds possible it would explain the bang probably needs a re tune soon any way I reckon i will do that After i get my FMIC put on in a week or 2.

[Sunkist]

did you re tighten them after it was warm? steel expands bud so things loosen themselves.

also ECU could sound right as when high in the revs you will get an injection pulse when you release the accelerator. i think its to cool down pistons or something but i know it does it

[666DAN]

My tiptronic ones used to do the same on high rpm upshift, the n/a with the kakimoto exhaust it used to bark, later with the turbo more of a bang

[chiksluvit]

ECU on auto skylines retard timing on upshift to protect the gearbox

manual doesnt

retarded timing on 0 load high rpm creates the bang

so its just the ecu, nothing to stress about

anyone who has a power fc in their manual, try changing the timing advance in first row to 0, it'll do the same too, refer to paulr33's PFC FAQ

[Tbetts]

Ok so i checked it out and yes it is the ecu!

Sooo with tax time conveniently placed just around when i need a tune i think i might invest in a EBC, Nistune and have a FMIC already then i just need it all fitted.

Fingers Crossed for 180-200kw at the wheels

Thanks for the help

[bubba]

ECU on auto skylines retard timing on upshift to protect the gearbox

manual doesnt

retarded timing on 0 load high rpm creates the bang

so its just the ecu, nothing to stress about

^^ this.

also ECU could sound right as when high in the revs you will get an injection pulse when you release the accelerator. i think its to cool down pistons or something but i know it does it

^^ not this.