popping exhaust while accelerating

[letemlaf]

i have a r33 gtst and while im accelerating with my foot to the floor, when i hit about 4 or 5 thousand rpm i get a massive pop comming through the exhaust. its not that loud but while it does the single pop the car stopped accelerating for that brief second and then screams the rest of the way to red line.

im worried if this is a bad thing or if it can do any damage at all.

any ideas?

[drifto]

Sounds like fuel cut from the boost limiter in the stock CPU.

If your not running more then 9 or 10 psi or do have a boost cut defender then it would be the fuel supply not keeping up with demand as you come on boost hard.

Another cause is old or faulty plugs, or wrong plug gap. Take em out and inspect the colour and condition of the core and electrode.

The reason why i would think it is not plugs initially, is the fact that it happens only at 5-6 grand and then cleans up to the red line.

When my plugs were bad it broke down all the way to the red line when ever under high boost load.

[ENTYSU]

yeh true mostley what drifto said , just make sure your not leaning out at that point , or when it is just about too happen just see if there is a plum of black smoke after the pop. it could be a glitch in the fuel map coming onto boost.

[letemlaf]

its not pinging when it does that is it?

as far as i can see theres no puff of smoke

do u mean like when u see some of the high powered skylines hitting the drags and they change gear and all the smoke (fuel) comes out?

[ENTYSU]

yes i mean that ...kind off like when its hitting fuel cut , u will see a blast of black smoke during that pop....

you will know if its pinging mate , just listen for a ratteling sound coming from the valve train ... like a clangy sound , that means its realy lean and its pre detoating due too great heat in the combustion chamber, if its doing this STOP! straight away or youll have melted pistons in no time ......

well if u can see no puff of smoke i think u might be leaning out mate ... how much boost are you running and do u have a fuel cut defender or anything else modified too your computer system

[letemlaf]

hrm as far as i can tell i got no fuel cut defender (maybe thats coz i dont know what it looks like). im running 7psi boost.

can leaning out damage the car?

[ENTYSU]

Wont damage the car man just the DAM engine ... ,realy bad like no more engine after a single vital knock

[ENTYSU]

7 pounds ... dam i recomend going too a mechanic and getting your fuel pump diagnosed .... fuel pressure wise and fule flow rate ... trust me most imports stuff there fuel pump b4 long due too the boost

[FATGTS-R]

"Wont damage the car man just the DAM engine ... just imagine your seeing your girlfreind ***ing another bloke infront of you , thats how bad the engine is hurting when your leaning it out ....."

Um yeah......... You could put it that way I suppose. LOL

[Guilty]

ummm ive actually knoticed my poppin..but its only when i like rev it to say 5-6000rpm in first gear and wen i knock it down to 2nd, it makes the pop noise..

is my problem the same as letemlaf ?

[BHDave]

Guilty, you just have the rich pop when you are changing gear, most skylines have it but some more than others.

Mine used to get it quite loud until i took some fuel out

[ENTYSU]

ummm ive actually knoticed my poppin..but its only when i like rev it to say 5-6000rpm in first gear and wen i knock it down to 2nd, it makes the pop noise..

is my problem the same as letemlaf ?

its mainly the rich fuel curve in the fuel map after boosting hard you back of str8 away and there will be excess fuel in the exhaust and combustion chamber and when u come back on hard you are just burning alot more fuel at that moment thats why u get a wicked pop and maby even a shoot of flame if u have a hi flow cat or better yet non at all ..

[Kinks]

it sounds like your coil packs are getting tired, mine does the same thing. check plugs first - i'd put new plugs in people recommend gapping them to 0.8. if you've done that and it's still missing i'd say coil packs.

[ENTYSU]

it sounds like your coil packs are getting tired, mine does the same thing.  check plugs first - i'd put new plugs in people recommend gapping them to 0.8.  if you've done that and it's still missing i'd say coil packs.

yes it would be this man but if it was popping and farting all the way up the load range not just at 5-6k ........ but yes check the GAP .8 of a mill is the way too go .....but i realy do recomend a fuel pressure check and fuel flow check ...

[letemlaf]

can any mechanic do a fuel pressure check and fuel flow check?

roughly what costs are envolved if u know?

[ENTYSU]

yeh any mechanic with the device , just say i think my fuel pump may be on its way out and need a check up for flow and pressure , would be better on a dyno , not much if its just a check without a dyno about 30 bucks but if u wanna check up on the dyno well im not sure there i say around 100 .... ? all depends on the leniency off the mechanic

[Guilty]

ohhhhhhhhz ok

so there is nothing wrong with my poppin right?

like my problem is totally different to letemlaf ?

thanks for the help guys

[ENTYSU]

ohhhhhhhhz ok

so there is nothing wrong with my poppin right?

like my problem is totally different to letemlaf ?

thanks for the help guys

INDEED.......Happy popping

[letemlaf]

im gonna take the spark plugs out and check them tomorrow morning,

at the back of the black cover theres some kind of sensor or something.

is that hard to take off and replace or is there anything else that might be a ittle bit tricky that i need to watch out for?

then ill get the fuel flow tested

[ENTYSU]

sensor, well for memory there are the coil packs on top of the plugs then there should be a ignition module coming from the coils from thought there is no sensor at the back of the head .... explain more on this sensor