[Mk2] [Turbo] Loud exhaust pop. HOW??

[pez]

Hi all,

I once heard a Skyline that i was racing produce a very loud pop from his exhaust.

Now my question is that how can i make mine pop really loudly every now and then?

I currently have HKS induction kit and Apexi GT on my tubby. To be honest i do hear pops regularly from mine but never had a loud one.


Thanks

[CosmosblueMR2]

the "pops" you hear are unburnt fuel igniting in the exhaust...

free-er flowing the exhaust the more you will get.. along with how rich your map is (stock maps are quite rich)


Inj duty cycles go 100% on lift off of the gas (momentarily)- so just plant your foot back on and "BANG" - you will probably notice this when changing gear mostly... (because of the lift off and then planting again)

[pez]

I will try this but i am sure he had bigger fuel injectors and richer map.

So i guess those have to be my next mod.

It is unbelievable the amount of unfamiliar racers that pop sound scares. I have seen it loads of times and every time it makes me laugh.

As soon as they hear the pop they think "xxxx, my car is falling apart or i blew my engine", so they brake for their lives.

[CosmosblueMR2]

I will try this but i am sure he had bigger fuel injectors and richer map.

So i guess those have to be my next mod.

if you want bigger injectors and a richer map ( ) then you will need a new ECU to manage it all. but I'm sure you know this already.

Otherwise if you just want a pig rich map - get a uni-chip and a crap Mapper - stock injectors still have life in them no need to change.

[pez]

I was aware of the ECU but thank you for mentioning it.

So are you saying i should forget about those mods?

[CosmosblueMR2]

So are you saying i should forget about those mods?

no, if you are wanting more performance... (but obviously you don;t want a pig rich map for that !)

but it's horses for courses...
if you are only doing all this for the pops of the exhaust - you don't need the expense of :

Standalone ECU
bigger Injectors
Mapping
+ Labour...


just go for a unichip + rubbish Map instead

(Im assuming in all this, that your current exhaust set-up is decatted by the way )

[pez]

Yeah, i have the original cat on the car but it has been gutted.

[amnesia]

Skylines have a hotwire air flow meter which measures the air immediately after the filter. If you run a vent to atmosphere blow off valve then the air will be vented but the fuel for that volume of air will still get into the cylinders as the ECU has already read the amount of air passing through the AFM.

This fuel has no oxygen to combust with and so is expelled through the exhaust valves and out through the exhaust. If the exhaust is hot enough then this fuel then ignites and you get flames, and / or a loud pop or bang.
The car is not technically over-fuelling... if anything it is UNDER-AIRING as the fuel would have been the correct amount if the BOV hadn't have vented the air when the throttle was closed.

I believe MR2 tubbys run a MAP sensor which is the pressure in the manifold (rather than airflow past a hot wire). When you lift off the throttle the BOV vents the air so the pressure drops - consequently the fuelling is adjusted to suit and you don't get uncombusted fuel passing through the exhaust.


Ergo, as mentioned in Cosmo's post above ^^^, the only real way of getting popping and banging (and flames, if that's your bag) is to alter the ECU to overfuel. This could, however, cause bore wash, and premature engine failure, along with costing you more in fuel.

I would be happier in the knowledge that your car is more technically advanced than a Skyline and doesn't therefore need to fart and backfire when you change gear

It does sound good though, and is handy for stopping rep-mobiles from tailgating on the motorway !

Sorry for the essay...

Daniel.

[Sponge Bob]

Can't you adjust the mixture from the AFM - there's a small lever which can be moved... whack it to uber rich... you'll foul up your plugs and get lots of poppy pop pop pops... everyeon's happy

[CosmosblueMR2]

Can't you adjust the mixture from the AFM - there's a small lever which can be moved... whack it to uber rich... you'll foul up your plugs and get lots of poppy pop pop pops... everyeon's happy

he has a rev 3


so no

[dawolf]

All turbo's will pop a bit on the overrun due to their very nature of running rich and the exhaust getting very hot. A simple de-cat will make it pop loudly.

[black2]

yeah mine pop's and bangs not very often, you have to get the revs right and it seems to work better in 3rd gear than any other. going through a tunnel on my way home from work i got a very loud bang although the woman behind me did sh@t herself and brake very hard did make me chuckle

[2Crooky]

Just get the exhaust stupidly hot by driving it hard......on a track of course and then play around with throttle resoponse to get some nice pops....

Or fit anti lag which is probs what the Skyline had

[pez]

Awesome replies. Thank you all.

[Sponge Bob]

Can't you adjust the mixture from the AFM - there's a small lever which can be moved... whack it to uber rich... you'll foul up your plugs and get lots of poppy pop pop pops... everyeon's happy

he has a rev 3


so no

hehe

[rossdymond3352]

Theres a lever on the AFM? what purpose does it serve? Never noticved one although ive never really looked!

Ross

[klx_boy]

I think hes talking about the screw under the rubber bung on the AFM? you can turn it to weaken or richen the air mixture i believe.

[CosmosblueMR2]

I can't beleive people are advocating touching this, has the board gone mad ?

[2Crooky]

I can't beleive people are advocating touching this, has the board gone mad ?

Watcha mean bud??

[CosmosblueMR2]

adjusting the AFM