Hot Rod Cams Idle Vacuum

[StockishS197]

Trying to track down decel popping and occasional hunting idle, starting with potential vacuum leaks on my 2007 Mustang GT with Hot Rod cams.

What sort of idle vacuum should I be seeing at a hot idle with hot rods at 840 RPM? Currently showing between 13-14 inhg at hot idle.

Does that sound about right or a little on the low side?

 

[whitmanink]

ive always had a hunting idle since my jlt cai was installed ,, decel pop as well,, lito said all looks good.. i changed my brake booster cuz that was bad ,,but yea still problems

 

[bambam 06]

Any time you have high lift cams, your vacuum is going to be low. I have Comps Mother thumpr and my vacuum is 10 to 12 ingh.

 

[whitmanink]

Any time you have high lift cams, your vacuum is going to be low. I have Comps Mother thumpr and my vacuum is 10 to 12 ingh.

it was my understanding that the gt500 brake booster was better for the cams, so i got one,,
still hunting at idle but only when warmed up ,,
a year ago i changed intake gaskets and even the brake booster hose and check valve .. still the same,
it does seem tho like with the gt500 brake booster the brakes are better..
but i still get the annoying hunting and decel pop , from time to time..

ive sometimes wonderd if the tune itself isnt right ,, but idk ,, lito has my car running awsome otherwise.

still its anoying tho ,, but io guess i just learned to deal with it..

i even reset the pcm many times ,and did an "idle relearn",, still only when hot will it hunt ..?

 

[86GT351]

it was my understanding that the gt500 brake booster was better for the cams, so i got one,,
still hunting at idle but only when warmed up ,,
a year ago i changed intake gaskets and even the brake booster hose and check valve .. still the same,
it does seem tho like with the gt500 brake booster the brakes are better..
but i still get the annoying hunting and decel pop , from time to time..

ive sometimes wonderd if the tune itself isnt right ,, but idk ,, lito has my car running awsome otherwise.

still its anoying tho ,, but io guess i just learned to deal with it..

i even reset the pcm many times ,and did an "idle relearn",, still only when hot will it hunt ..?

Even with the best tuners in the world nothing will ever be 100% perfect all the time.

 

[StockishS197]

Even with the best tuners in the world nothing will ever be 100% perfect all the time.

From what I have seen, these cars just tend to have occasional RPM drop when coming to a stop. Something to do with the DBW

To answer my own original question, Lito confirmed 13-14 inhg is fine (and even on the higher side for a cammed car).

 

[whitmanink]

Even with the best tuners in the world nothing will ever be 100% perfect all the time.

im new to the tuning world,,,
this car is my first project car aiming at 600 wheel ,,

im very very happy with lito ,, he did me good, like i said my car rips,, just the idle hunt here and there and the backfire every now and then is the "side effects"

and like i said , its been this way since my jlt, CAI, long before the mutha thumpers i have in,,
so to me as lomg as the engine is happy and dont go boom and bang,, im a happy camper

 

[86GT351]

im new to the tuning world,,,
this car is my first project car aiming at 600 wheel ,,

im very very happy with lito ,, he did me good, like i said my car rips,, just the idle hunt here and there and the backfire every now and then is the "side effects"

and like i said , its been this way since my jlt, CAI, long before the mutha thumpers i have in,,
so to me as lomg as the engine is happy and dont go boom and bang,, im a happy camper

I understand. This is not a slight on Lito. There are way too many variables with a car running for a tuner to be able to compensate for all the time.

 

[Dino Dino Bambino]

i'm very very happy with lito ,, he did me good, like i said my car rips,, just the idle hunt here and there and the backfire every now and then is the "side effects"

Even the best tuners can't completely mitigate the effects of a longer valve overlap, and one of them is spitting and popping from the exhaust as a result of unburnt fuel from the fresh intake charge getting into the header tubes. The rougher idle and lower intake manifold vacuum are others.