High fuel consumption and cracked exhaust manifold?

"dan martin" <nospamdwmartin@idirect.com> wrote in
news:FK6dnQy8k86uA47fRVn-pA@look.ca:

> I beleive it's due to less back pressure. I have seen my fuel consution
> skyrocket from a open straight pipe.
>
> Dan
>
> <KnifeKnut@gmail.com> wrote in message
> news:1108522596.679172.14270@f14g2000cwb.googlegro ups.com...
>>
>> vtecracing wrote:
>> > Yes, a cracked exhaust manifold will result in excessive gas
>> > consumption.
>>
>> Why?
>>
>
>

On a o2 sensor equipped car, it will make a difference. Exhaust "pressure"
is not constant, a good part of the time when not at high throttle
settings, a negative pressure exists in the manifold . Air enters through
the crack, and the oxygen in the added air is read by the o2 sensor, and it
compensates by adding more fuel to try to correct the "excess" oxygen. I
have not had direct experience with it but a friend had a Fiero, his
stainless headers cracked constantly, and he said he could tell by
monitoring his performance and gas mileage.
Scott

I beleive it's due to less back pressure. I have seen my fuel consution
skyrocket from a open straight pipe.

Dan

<KnifeKnut@gmail.com> wrote in message
news:1108522596.679172.14270@f14g2000cwb.googlegro ups.com...
>
> vtecracing wrote:
> > Yes, a cracked exhaust manifold will result in excessive gas
> > consumption.
>
> Why?
>

vtecracing wrote:
> Yes, a cracked exhaust manifold will result in excessive gas
> consumption.

Why?

Yes, a cracked exhaust manifold will result in excessive gas
consumption. The easiest way to test if theres a crack is listening to
the sound of the engine. First, start off by making sure that you
engine is at full operating engine temperatures. Then pop open your
hood and manually apply the throttle from the throttle body. If you
hear any abnormal tone in your exhaust then you can be sure that there
is a leak. I hope this helps you.

http://www.trackspeedracing.com
"Honda and Acura Drag Racing Parts Specialist"

Hi,

I just went through my papers and found a recall from Honda that mentionned
my Exhaust manifold could be cracked and would be garanteed under their
extended warranty. How would I know if the manifold is cracked? Is there a
loud noise? Does the consumption go up? I've noticed that my consumption has
actually gone up but yesterday I had my timebelt changed and they didn't
find anything? is it possible to overlook this?

thanks,

Jason