JoshG

I have a carb rx7 turbo and everytime I turn it off it backfires loudly I would love to know what Is causing this and if it is doing any harm?

GSLSEforme

Need some more specific info than what you have posted here.
Generally,backfiring or more correctly”afterburn” happens when there is combustible fuel in exhaust system that finds a source of air/oxygen and ignites.

JoshG

After I turn the car off about a second later a loud backfire comes from the exhaust could these be because I'm carbed and I would want to fix it because it sounds just like a gun shot when I'm just trying to turn the car off.

t_g_farrell

iTrader: (1)

Its a turbo so its probably running rich at idle and dumping unburned fuel at shutdown is my guess.

GSLSEforme

Again,how about some more info...
What kind of carb,what kind of turbo?
Is ignition system stock?
Pics?

JoshG

holley 650 double pumper 2 msd 6al 2 mad blaster ss and 0n3 70mm turbo running 15psi

JoshG

aeromotive a1000 fuel pump with fuel sump also aeromotive fpr motor is a turbo 2 swap in a fb with turbo 2 trans and has large streetport and is pinned

JoshG

also I had a thread on how much power I was making with the one 70mm turbo on 15psi and I got mixed answers from 250 to 350 I wanted to know what you guys think off those estimates for power?

Qingdao

iTrader: (3)

Are you letting the turbo slow down before you shut it off? Let the car idle for a few seconds before you shut it off; it allows the turbo some time to slow down before the oil feed stops pumping. Probably has nothing to do with the backfiring, but its a good idea.

More than likely its just a leaky exhaust causing some fresh O2 in when the car is shut off. If the engine isn't running the exhaust leak will let air in as apposed to being pushed out. That causes the un-burnt fuel to ignite (hot/fuel/O2 makes for combustion).


No, not a problem. Kinda fun too. But do watch out for bumper fires.

JoshG

could these be the issue their is no weld on some of my exhaust tip?

JoshG

yes I let the turbo slow down for like a good 30 seconds would time do you suggest to let it slow and cool down?

GSLSEforme

Bundle up some rags and place/hold in position over exhaust outlet with engine running and have a helper listen for hiss at location of escaping exhaust gas in exhaust system. That location will be source of air entering exhaust system.

Qingdao

iTrader: (3)

Should be good and plenty time depending on how fast the turbo was spooling when you started the idle period.

I have a good half a mile of neighborhood before I get to my house from the main road. So my engine isn't turning that hard through the neighborhood. That and a good 5 or ten seconds at my house is more than enough to slow it down. IDK i'm no expert, but just use your best judgement 30 seconds seems fine.


A leak at the tip isn't gonna make a boom. A leak further up stream, like right after the turbo will. BUT seeing your tail pipe is that sooty; hows your afrs? rich?

JoshG

It previously ran super rich too which led to it fouling spark plugs but we leaned out the carb some which helped a lot and it hits like 10.9 to 11.0 on wot and at idle is 12.6 also could i have low compression because when I cold start or even hot start my car it takes at least two to three tries to get it on and then it chokes out if I hit the throttle too fast then eventually when it gets a little warm it's fine or would that be the result of me not having a choke for my holley carb??

j9fd3s

iTrader: (3)

yes, you said it yourself....

when an engine is cold it needs to run richer than it does when its warm, so with a carburetor there is a choke to do this. if you remove the choke from the carb it will run badly because the mixture is wrong when the engine is cold. if you're willing to be gentle until its warmed up its not a problem.

JoshG

thanks man glad to hear I was getting the feeling I was sold a car that was running low compression but hearing from you that's not the issue.