[T2] What's With the Popping Noise in the Exhaust?

[Al Brase]

Sorry, I disagree. ALL older systems do it. It likely has a slight leak in
the exhaust. On the rebound of the escape of exhaust gas, air will enter.
This air will allow the rich mixture to combust. Very modern systems will
almost completely stop any fuel delivery under coasting conditions. Some
have AIR or EGR that may be allowing air to enter. (But EGR is supposed to
go the other way- exhaust to intake.)
Al

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On Sat, Jul 1, 2017 at 10:54 PM, c.dreike <c.dreike at verizon.net> wrote:

> I believe it may due in part to the fuel/air mixture enriching slightly
> under those conditions to reduce emissions (thanks EPA). The richer mixture
> is not burning fully in the cylinders and igniting in the exhaust manifold.
> Older engines/carb/dizzies don't do that.
>
> Chris
>
> On 7/1/2017 8:23 PM, Roger Lemberg wrote:
>
>> I’ve been living with this problem since my parents owned a ’69 bus and I
>> know I’m not the only one.
>>
>> Sometimes, when the car is “overrunning” the engine (long steep
>> down-hills, engine braking) there’s a popping noise (backfire?) coming from
>> the exhaust.
>>
>> Is there something that can be done?
>>
>> Peace,
>>
>> Phrogbus and its Phroggie
>> (’70 Sportsmobile conversion)
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