Closed loop Lean cruise and idle and cruise timing

General Tuning Questions And Discussions
vp304
Posts: 451
Joined: Wed May 19, 2010 2:21 pm

Re: Closed loop Lean cruise and idle and cruise timing

Post by vp304 »

its factory cat il double check if 2 1/4 or 2.5 inch size
I get what you mean tho.
'quipt4it
Posts: 675
Joined: Sun Oct 28, 2012 12:57 pm

Re: Closed loop Lean cruise and idle and cruise timing

Post by 'quipt4it »

Stock is 2.25" 400CPI.
Definitely worth looking at.
Unless there are some pinched bends in the exhaust tubing, this will be holding it back, ie the biggest restriction.
vp304
Posts: 451
Joined: Wed May 19, 2010 2:21 pm

Re: Closed loop Lean cruise and idle and cruise timing

Post by vp304 »

Yeah i was hoping to decat it in the next 1-2 weeks. Will let you know how i go.
Rest of system is Mandrell bend. I will have a look through the muffler also when i cut the cat of see what it looks like inside also.
'quipt4it
Posts: 675
Joined: Sun Oct 28, 2012 12:57 pm

Re: Closed loop Lean cruise and idle and cruise timing

Post by 'quipt4it »

vp304 wrote:...Going to decat it soon as im on stock pulley and reading 11psi at 5500 rpm i think exhaust is holding it back a little.
I know 11 psi sounds crazy high for stock pulley
But the exhaust holding it back would mean higher boost...
That exhaust would have to be really restrictive to be almost doubling the boost pressure.
I would guess that the cat is either blocked or partially melted. Or the muffler has collapsed.
vp304
Posts: 451
Joined: Wed May 19, 2010 2:21 pm

Re: Closed loop Lean cruise and idle and cruise timing

Post by vp304 »

Thats what im hoping has happened so when i decat it will have a look at the muffler then
May unleash a whole lot of power hehehe
'quipt4it
Posts: 675
Joined: Sun Oct 28, 2012 12:57 pm

Re: Closed loop Lean cruise and idle and cruise timing

Post by 'quipt4it »

Have you noticed any difference in running?
vp304
Posts: 451
Joined: Wed May 19, 2010 2:21 pm

Re: Closed loop Lean cruise and idle and cruise timing

Post by vp304 »

Its always felt from day dot, like it falls over after 4000rpm. Like strong up to 4000rpm then just feels like runs outa puff.
Could be exhaust or could be timing being so low. Or maybe or bit of both.
'quipt4it
Posts: 675
Joined: Sun Oct 28, 2012 12:57 pm

Re: Closed loop Lean cruise and idle and cruise timing

Post by 'quipt4it »

Those L67's are supposed to be good to 5200 RPM, where they produce their max. power. Max. tq. on those 'early' ones is @ 3200 RPM.
Someone is being short-changed... :sad2:
vp304
Posts: 451
Joined: Wed May 19, 2010 2:21 pm

Re: Closed loop Lean cruise and idle and cruise timing

Post by vp304 »

Yeah but i was driving a ls v8 before this complete different kettle of fish hehe
I will look into the exhaust tho i think is some funny business going on there
'quipt4it
Posts: 675
Joined: Sun Oct 28, 2012 12:57 pm

Re: Closed loop Lean cruise and idle and cruise timing

Post by 'quipt4it »

You can do an exhaust back-pressure test. That will verify excessive resistance to exhaust flow. Would save cutting/ re-welding, getting thrown in jail etc.
It would involve tapping in a port fitting before the item you most suspect to be restrictive.
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