A quick question for the Supertrapp users

4846 Views 26 Replies 13 Participants Last post by jbranson, Apr 28, 2007

ROSKO

Discussion Starter · Apr 12, 2007

I know most of you run the solid style end-cap
(like so)

has anyone used the reverse cone style?
(like so)

BORN TO LURK, FORCED TO WORK.
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Anti reversion cones would serve a very similar function as megaphones. Impractical for most V8's to run megs.

Parks...you mean a "poppit" valve? Already been done...kind of hard to control valve timing if exhaust pressure has to open the valve. One might think that inertia would lift the reed and create a vacume behind it...not so...some positive pressure will always be required to lift the reed...you wouldn't want that positive pressure between the reed and the exhaust valve. Better to let that inertia expend itself in an open pipe pulling a negative pressure behind it.

JohnnyB

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ROSKO

Discussion Starter · #22 · Apr 25, 2007

BFD, Aaron, Johnny and everyone thanks for the info. Traded the reverse for a solid end cap and testing with 7 disks to start. She's running. so far so good.

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ROSKO

Discussion Starter · #23 · Apr 27, 2007

on the 2-1 w/ 4" trapp 7 plates chokes the engine. We pulled the backing plate 1/2" back and she rev'd right up to 9.5 no problem. May have to run the full dozen plates.

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ttilghman

· #24 · Apr 27, 2007

rosko-

as discussed before, i'm running 12 disks each side with the 1-1 and still a hair rich. (did you see me bog it down to the back of the starting grid in Aron's video) so it's time to eff with the carburation again. for some reason, i'm just hesitant to take the step down from 105s to 100s....maybe floats first? i just know i can't settle for starts like i had at summit.

have a hoot monday...oh, and i have your engine from joe, aaron will get it right over to you....thanks for the K0 cam and followers. so the deal is you can have the engine once you turn some laps a summit.

-tt

Edited by - ttilghman on Apr 27 2007 1:51:37 PM

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jbranson

· #25 · Apr 27, 2007

I know I'm not going to get you guys to believe me....but...7-8 four inches disks should be fine for a 350 2-1. If you have seven on it and it won't rev past 9,500 it's not because the exhaust is being restricted, it's more likely because you are too rich. You don't tune the exhuast to match the jetting...you jet to match the exhaust.

Basically you can't do either worth a crap without a dyno. Typical process would be...put on 7 or 8 disks...run it on the dyno...jet for max power. Then add a few disks and see what it does for power...if it makes more....keep screwing the exhaust. Then when it maxes out...re-jet again for max power (or curve).

Exhaust is a fixed entity...the engine will make the most power with a certain exhaust, and a certain amount of disks...always...once that is determined then you jet to for max power. You don't correct jetting problems by adjusting the exhaust system. Like I've said before, my system has 210cc breathing through a 2-1 seven 3" disks at 12,000 rpm...and makes about 120hp/liter. Exhaust will almost never limit how far the engine revs....that's on the intake side.

Also....make sure your trapp disks have the little edges pointed towards the BACK...NOT the FRONT. And...you only want them tight enough to not rattle...if you crank down the bolts you will close up the space between the disks and it won't breath for shit.
JohnnyB

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ROSKO

Discussion Starter · #26 · Apr 28, 2007

Whoa! I believe you, that's why I keep asking my stupid questions. It's hard to wrap my head around going down as far as 105 or 100. It really comes down to running it, I won't know sht till I can really run it full bore.

TT,
Worst delivery service ever, even worse than Aaron's.

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jbranson

· #27 · Apr 28, 2007

Nobody ever believes me....about exhaust...or ufo's.

Yes, wide open throttle at close to redline rpm is the only way you'll really determine how it's going to run under race conditions. Four strokers need to always keep in mind the most common reason for killing power is running too rich. You'll know it if it's too lean..it will just fall right on it's face...too rich and it will just feel doggy and sluggish. Reading plugs is iffy...takes a real experienced hand to do a proper throttle/ignition chop. And with pump gas if the plugs look a little rich...they are probably very rich.

A dyno run will be the best money and time you ever spent.

JohnnyB

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