So every time I've listened to a bridgeport idle they always change back and forth from brap brap brap brap to brrrrrrrrrrrrrrrrrrrrrrrrrr.

I've just fired mine up and it does the same thing, here is a video of it:

http://www.indyhp.com/vids/zinx-halfbridge_starting.wmv

The idle changes at 1:01 and 1:16.

Anyone have any insight into this? I'm guessing its something to do with the overlap.

 

in your ecu map, at different temperatures, your car will adjust the amount of fuel and the idle level depending on water temps.... This could have something to do with it...

 

my guess is you're hearing a confused stock ECU trying to deal with the overlap.

 

Its not just my car, every bridge i've heard does this. I don't think its something in the tuning. The idle is rock solid, as well as the all temps. Its not moving to any other bars on the coolant adjustment map.

 

ive always wondered this also

 

My guess always was that it had something to do with the plugs fouling slightly. On my carbed car, the car would start to run like that, and after I revd it up to "clean it out" it would idle with strong sharp braps again.

 

You'd think if that were happening you could see the idle drop or fluctuate, but it doesn't. If you couldn't hear the car do this, you'd never know it way happening.

 

my stock port you could hear it change rythyms. never stayed the same. maybe its a rotary thing

 

yes, it was the same for my car when i had stock ports and with the street port.... i just figured it was the position on the map changing and the temps adjustments... either way, if your looking to fix the problem, put an ls1 in there... lol... or just deal with our crazy rotaries...

 

Its not a problem, so i'm not looking to fix it, just wondering why.

 

When it's brapping "solid" the rotors are in phase. When it's just sorta rrrrrr then the rotors are brapping out of phase of each other, so it seems smooth.

Because of the plenum volume on my P-port, it almost always was "smooth" at rest. When coasting, it would brap (buck).

 

I have always wondered the same, although even stock rotaries do it too.....

 

so you mean they are both rotating the same and in sync?

ya stock ones be like pprrrrrrrrrrrrrrrrrrrrrrrrrrrrr pr ppr pr pppppppprrrrrrrrrrrrrrrrrrrr
or something like that

 

like would this be out of sync?

 

just curious what is your idle set at...and hey thats my avatar picture..lol

 

lol ya sorry

 

im confused on what in and out of sync "physically" is.

 

Your exhaust sounds awesome. Can you elaborate more on the exhaust. This has to be the best sounding 4 inch exhaust without a silencer in the tailpipe. Is it really that quiet at idle?

Anthony

 

You get the "brap" with high overlap ports (like bridge) because the engine misfires rhythmically due to exhaust contamination of the intake charge. Sometimes that rhythm changes as no two combustion events are the same so the engine may change it's tune for a few seconds.

 

Zinx my halfbridge does this all the time. If it starts doing it I rev it a little and it goes back to brap braping away. I saw your car at Tuxedo but I dont think I met you........

 

Same here....

 

My bridged 12a does the same thing goes back and forth from smooth streetport idle to brap brap idle of the bridge. I'm running a 48IDA on my bridge. I dont care it seems fine to me, but with the p-port going in i cant wait to hear its idle

 

Its basically a 4" downpipe off the T88 back to a 4" in and out magnaflow resonator and then a 4" oval straight through mangaflow muffler. I don't know exactly which part numbers of anything, but it really is that quiet compared to other 1/2 bridged cars i've heard.

 

That makes sense although the A/Fs don't change at all, they are rock solid.

 

Same here. I was the guy in the black Ireland jacket, shaved head. Congrats on the 562!