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Popping On Decel

Country Cruzin
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Country Cruzin Collaborator

Country Cruzin

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Just got my car back from the work shop, has now got 270 degree cams an cam gears, an the insides of the cat were removed as it was chocked up, an some other unrelated mods.

Car now pops under decelleration with an occasional loud pop (backfire?) when i back off from full throttle, (full revs) to grab nxt gear or just slow down with an occasional flame coming out the back exhaust.. wondering wot people's thought are, is this normal or would it be hurting the engine? :ermm:

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The Mafia Grand Master

The Mafia

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Having not cat will allow the popping and flames travel all the way to the end of the exhaust. The cat usually stops this and the sound.

The other thing is, if you have an ATMO BOV, aw well as AFMs. This creates a rich condition on decell, and you will get this same issue, but more likely stalls and fouled plugs. The car will eventually start running like crap.

Country Cruzin Collaborator

Country Cruzin

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Yer i have an atmo bov, always have, were on the car when i bought it 4 years ago, chnaged where it is so its closer to the intake an put a diff bov on but both were atmo bov's. dont use the z32's anymore since i got a vipec bout 2 years ago.

Did u mean the car will start running like shit if the plugs carbon up or for a diff reason? =s

The Mafia Grand Master

The Mafia

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Yer i have an atmo bov, always have, were on the car when i bought it 4 years ago, chnaged where it is so its closer to the intake an put a diff bov on but both were atmo bov's. dont use the z32's anymore since i got a vipec bout 2 years ago.

Did u mean the car will start running like shit if the plugs carbon up or for a diff reason? =s

If you have a Vipec and you're running a map sensor, then the ATMO BOVs shouldn't be a problem. I've never liked them because the cars were never designed to operate that way, but thats just me, I've always noticed cars run better with the plumb back ones on. But where there are heavy mods, it doesn't usually matter any more.

Also, after clearing your cat, you might need a tune.

When I mentioned the plugs fouling, that will only happen with ATMO BOV's and AFMs.

But as I said earlier, with no cats, you will always get popping and flames, because the cats always block this. Its also how a cop can tell if you have not cat - because you are blowing flames. A smart one will simply hear it via the popping.

Anyway, the short version - No cats = popping and flames.

Country Cruzin Collaborator

Country Cruzin

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Car has been tuned since, thinkin of gettin a new cat again.. got 3inch in let out let on current cat with a 3inch high flow cat, does anyone know if you can put a 4 inch cat into a 3inch exhaust? or does the diff size (3inch -4inch-3inch) mess up the air flow too much?

Country Cruzin Collaborator

Country Cruzin

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:ermm: Ritio, will ring them tomorrow, an guess ill have take it back to brisbane when i get a spare weekend.. an get them to strap it back on the dyno. hopefully for free.. already spent 1k on tuning for the cam, an cam gears.. cat was removed before tuning. i dont mind paying out my hard earned dollars to overcharging performance shops but when i do, i expect the jobs to be done perfect.. an get annoyed when things aren't because it means wasting a weekend to go down to brissie drop the car off, an if it cant be fixed immediatley finding a lift home an a lift back down to pick it up when its ready, or paying an employee to pick me up an drop me off, or sometimes its easyier if im busy to tilt tray it.. which is all a pain in the ass.+1 reason for buyin a stock xr6-t
KiwiRS4T Grand Master

KiwiRS4T

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Car has been tuned since, thinkin of gettin a new cat again.. got 3inch in let out let on current cat with a 3inch high flow cat, does anyone know if you can put a 4 inch cat into a 3inch exhaust? or does the diff size (3inch -4inch-3inch) mess up the air flow too much?

I have a 5in Venom 100 cell metal cat on a 3in exhaust - my theory is the bigger the cat the less the resistance.
gtsttrk Mentor

gtsttrk

Posted
Posted

I have a 5in Venom 100 cell metal cat on a 3in exhaust - my theory is the bigger the cat the less the resistance.

Running exactly the same as you mate, never had any issues and in my opinion you can't go to big on a turbo!

  • 4 weeks later...
Country Cruzin Collaborator

Country Cruzin

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took the car back, over run fuel cut was turned off, he turned it on.. but does it need setting up? seemed to have fixed the car for a while unless it was coincidence, just a slight popping on decel nothing major, but by that night it was back to back firing/shooting flames with a load bang, big enough so i could see the flames in my right hand mirror (exhaust is on the left) probably once in every 12 gear changes under full accelleration (when i back off to change gears) Could it be possible the computer turned it back off?? drove it last nite with a car load of ppl seemed to back fire every gear change under acceleration to some degree some very large, some not so big, all Very noticable..

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