fonseca

I'll host the article myself for a while, that site maxes out super fast.

gspots-01htse-

good thing that article was so informative or else i dont think that i would have made it through the whole read. GREAT FIND!! helps me. thanks

sndprssr

Since this is a sticky and I'm bored I figured I'd add my $0.02 so this might get a little long and boring for those that don't really care. Most of this will probably be pointless unless someone actually feels like doing a lot of reading or math...

1. More back pressure smooths out power pulses and prevents over-scavenging but is ineffective at high RPMs while less back pressure improves top end where over-scavenging in not a problem. As back pressure decreases, blow-down becomes more effective.

2. For those that didn't pick up on it scavenging is using the exhaust gases to pull in the new A/F mixture and of course over-scavenging is pulling in so much of the mixture part of it goes out with the exhaust. Reversion is the reverse flow of gasses into the cylinder which takes place at low RPMs with a cams having a high overlap or when scavenging is not synchronized with valve opening or with insufficient back pressure.

3. Optimum scavenging is determined by the Mean Flow Velocity which is the speed at which exhaust gasses exit. The common opinion is that the ideal velocity is 280 - 300 ft/sec in the middle of the selected RPM range and the exhaust ports should flow at least 85% of the intake port and thus is determined by pipe diameter. (formulas to find this crap will be at the bottom of the post)

4. Sonic Wave Scavenging deals with the pulse traveling back and forth in the exhaust track with shorter length pipes/headers while Thermal Wave Scavenging deals with the same but in pipes over 51".

Mean Flow Velocity – (APS/60) x (Bore²/Exhaust I.D.²)
MFV measured in ft./sec., Ideal is 280 – 300

Average Piston Speed (APS) – (Stroke x RPM)/6
APS measured in ft/min.

Sonic Wave Scavenging for RPM – (950 x EX)/Length; EX = Exhaust Open # + 180°
SWS for 50” or less header for top end power

Sonic Wave Scavenging for Length – (950 x EX)/RPM


Thermal Wave Scavenging for RPM – (1380 x EX)/Length; EX = Exhaust Open # + 180°
TWS for 51” or longer header for low end power

Thermal Wave Scavenging for Length – (1380 x EX)/RPM

radu_rd2

I hope this is the most appropriate thread to post this question: what do you think is the quietest performance muffler that would fit a tibby? I have researched this quite a bit, but I did not find any decisive answer (on the forums or the web).

I've narrowed it down to two choices:

Dynomax Super Turbo 17733 (as in the KFX exhaust).
Borla Pro XS 40364 (or other variations on it).

There are some test results online, and the Borla performs very well and seems very quiet - despite that it's apparently straight-through.. It's also pricier though. What do you think? Anybody has any comparison how much louder any of these two mufflers is compared to stock?

The Dynomax Super Turbo 17748 is probably quieter than both, but I'm pretty sure it's too big to fit on a tibby (20 inches just the muffler).

enigo

Just read a lil article that's good information on exhausts as well...

http://www.nsxprime.com/FAQ/Miscella...austtheory.htm

Polaris

^^^^Dude, you just reposted the first post...I started reading and was like hey, this is the same article haha

Tony Vendetta

I jst read this and it is very interesting and very educational, as far as I know for our cars specifically the magic # for our exhaust diameter is 2.25". What do you guys think, jst imagine this scenario, you have 4-2-1 headers 2.25" hi flow cat back exhaust and at the end of it you got a 3.5" muffler tip, to be more specific this muffler tip.

http://cgi.ebay.com/ebaymotors/3-5-Stainle...%3A1|240%3A1318

what do you guys think of the design of this muffler? is it good please give details on your opinions.

radu_rd2

^ It will be LOUD

Tony Vendetta

yes am sure it will be loud but believe me it wont be anywhere near as loud as catless....I had my auto tibby running like that, actually it still is lols, but what do you guys think is better a duel tip muffler or a single tip muffler of the same dimensions. like this one

http://cgi.ebay.com/ebaymotors/4-25-N1-SLA...%3A1|240%3A1318