coldfire

iTrader: (1)

Hi,

just wondering, what was the RB collected header primarily designed for (in terms of porting and powerband)? they say "streetable" which makes it sound that it is better designed for street use, but really an exhaust system is never really going to hinder street usage, in terms of performance, it will just merely optimize a certain part of the powerband depending on design...

also, what are the lengths of the primaries? looks like 30 inches or so...

it seems that the RB collected is neither a short nor long primary system...is this a decent compromise or does it kill the true potential of exhaust tuning?
i definetly agree in collecting exhaust...i don't see the advantage of running an uncollected true dual system. it seems that real tuning can be done using a collected system, just all the depends where you collect it i guess...

88IntegraLS

Contrary to some opinions I've read here, the RB streetable header is an excellent low cost short-primary header IMO. The runner length is 34" which is perfect for 8 trips through the runners at 900 degrees C given a 7000 rpm tune point and scavenging in resonance with subsequent exhaust port openings.

I made my own long primary system and the length came out to be exactly double the RB streetable header, subtract a couple inches to make up for the cooling effect of the gas through the pipe. My design is based on the principle of pipe resonance as taught in engineering physics class, and it matched up perfectly with how the RB is designed, basically if you can't fit a long primary system, you make the header half as long to get the same acoustic scavenging but at a higher resonance (arguably with a lower amplitude than the primary resonance ie. from a true long primary setup).

This is all acoustic tuning by the way, the collector is not ideal and would be better with a megaphone style cone aft the collecor (see yawpower.com for a couple pics of Paul Yaw's fabbed collectors on his own race engines).

Adding the RB streetable header to my medium streetported FC base model, which had a ported intake manifold and cold air intake, resulted in a .8sec. improvement in quarter mile time, from 15.6 to 14.8, even with the stock main cat and cat back exhaust behind it. I've read that this header won't work well on a stock port car though.

coldfire

iTrader: (1)

hmm, interesting. i would like to someday study exhaust resonance design more in detail...

i was always thinking that the RB collected header was not a short design, but your explanation makes sense...basically taking a calculated long primary design and cutting it in half...

i've been to the yawpower site a few times, but i'll give it a read again.

how do you think the RB collected header works with a half-bridge engine? i mean in terms of it being optimized or not.

Smilodon

Heck, why not just get some slip-fit bits and experiment?

coldfire

iTrader: (1)

care on elaborating?

really i was just wondering about the RB collected header specifically, since i really don't know much (IMHO anyway) about exhaust tuning.

if there really is a simple way to do it, on the specific engine in question, then i'm all for it

88IntegraLS

I don't have experience with bridgeport engines but the exhaust timing and resonance theory are all the same. If anything, bridgeport engines are more sensitive to exhaust tuning and backpressure than street port engines.

That said, the RB streetable header still functions as a short primary system tuned for 7000 rpm, and would work fine IMO if you don't have the room (and/or money) for a full long primary setup. The RB road race header was probably made for real racers who want the full 65-70 inch runner lengths, while the streetable header was what they saw as the next best compromise for street use when you have many more sound reducing devices behind the collector.

In my case, I just made this gnarly y pipe with three disc CC inserts, moroso spiral flow resonators leading to dynomax HD superturbo mufflers that were so big they barely fit in the FC muffler wells. The system is a true long primary with megaphone collector system, but is very quiet. My supercharger whine and intake hiss are louder than the exhaust at idle.

zerogrips13

can anyone give me some specs on the RB road race header .. i know they use 2" piping with so and so thickness, but how long is this thing?>?