How much would changing my exhaust effect my tune?
 

So I am going to be running a BP 12A with a holley 650. I wanted to know if i am risking anything by tuning with my dumps open then using Smaller diameter exhaust for noise control on the street.

I am fine with just not having the all the power, but I wanted to make sure the added backpressure with the dumps closed wasnt going to cause any major issues or damage.

Do you have access to a wideband? What size pipe is the street exhaust set up? It probably won't make a big difference with the added back pressure, just cut down on power and make driveability even worse.

It'll probably affect the tune a bit, but not enough to worry about. Like trochoid says, depending on how restrictive your exhaust is, it might adversely affect drivability because of the increased intake charge dilution.

The plan was to have 2 dumps right after the header, then a collector down to 2" or 2.24" back to the muffler. If there is room I might add some short glass packs.

It will have a wideband. but I have a feeling with this setup I will need 2(one for each pipe before the dump)

if you tune it uncorked, it'll probably just be really rich corked up, but its impossible to say how much.

going from an open dump to 2" pipe is such a huge step though, it may not even run. you may have to have a "street" and a "race" jet setup

I want to avoid swapping jets if I can. Would you think stepping up to 3" help?

If this was an injected motor I would be willing to run a dual tune, but other than that I am lazy.....

My current setup is 3.5" header going to stock 81-82 connecting pipe and a stock rusted out rear muffler. Also 81-82. Flows good, just loud. Just bought a RB 81-82 muffler, so we'll see how loud it is after.

2.5 single is big enough. 3" will be too loud and I dont care what muffler you stick in there, it will still be loud. you cant own a bridge and expect to be quiet. this is a common mistake.

+1
Yupp.

I wasnt expecting it to be silent or anything, just quieter so most cops wont bug me.

EDIT: Its kind of a long story but I did not intend to have a BP. It just kinda fell in my lap so I am making due with what I have :)

define quieter....bridge and quietness cant be used on the same sentence IMHO. muffle it with 2" single but performance will suffer.

I am looking for something about as loud as ricer exhaust on a civic.

Good luck doing that with a header,
That's where we're getting.

Noted. :)

It was worth a shot. :)

if you want a nice and quiet stock port motor I'll GLADLY trade you lol

I'm not trying to discourage you, or be an Ass.
Just stating my experience. I have a Monster Ported 12A in my Daily Driver. Originally it sported a RB Header/Presilencer and Stock 85' exhaust on back.(Tone sucked) And honestly, it was loud but just right for my taste. I do like a noticable but not annoying exhaust.
After, I tried porting a exhaust manifold to match my exhaust ports(they're huge, words can't describe) and then ran a open downpipe to the stock rear exhaust. Then it was quiet, to me. I then changed again to a Apexi N1 muffler. Loud, loud, loud. Even though I didn't change any tubing diameters.
After that I went to a flowmaster muffler, which was really quiet.(50 series) the thing was just too big. Flowed plenty though.
So, I then tried running the stock 81-82 connecting pipe and muffler with the ported manifold. A little louder, but, tone sucks. Like all stock exhaust does.
Nowww I have a custom fabbed 3.5" header with a scavenger style muffler welded in it and the stcok 81-82 rear exhaust. It's Hella loud. But, again, not too much for my taste but it does attract to much attention. Simply cause my 81-82 muffler is rusted out, has some holes in it.
So I bought a RB 'street port' muffler last night, we'll see how she sounds when I get her on. The tone is already amazing with my big header. Even with my POS muffler.
I'll have my custom header, 81-82 CP, and Street port muffler. IMO, it's a good combo for a big port engine daily driven that you want to make good power with and still be, somewhat quiet let's say. Or, tolerable would be a better word. It's all about a persons opinion. And another thing, at first everythings going to seem loud when you bolt it on but after driving it a while, it doesn't seem so bad.

ive got a P port, and it was honda ricer loud when exhaust 2.0 went on it. the KEY for a big port engine is actually the intake, lots of noise comes out of that too.

i put a stock 12A air cleaner on, it only flows enough for like 6000rpms, but the neighbor doesn't complain that his head is going to explode.

exhaust 2.0 is similar to the RB street port system, except i used a pair of straight thru glasspacks (31" long!) and it goes from 2x2" pipe, to a 1x3" pipe to a borla, which is a bad choice.

the glasspacks lasted 9 laps, the borla survived just fine, but it doesn't sound all that great and its expensive and its not quiet. people in my 'hood have never experienced a car like peepers, and with all the stickers it's invisible too, so they act like its some kind of gardening accident

3.0 might just be 2x2" pipe to 1x3" to an RB muffler. airbox 2 is in the mockup stage, basically its going from the stock intake's 3" inlet to 6" to a duct that goes to the front of the car

No worries, I wasn't taking it as you being an ass or anything. I really do respect the knowledge on this forum and am here to learn. Being a Mod on another fourm for a different car make I tend to be able to read people and what their intentions are.

I thank you all for the advise and will definitely be a learning process in building the exhaust for this car.