Mondo1 and Spike you guys are getting good. Joel, I think that you need to talk with Chet. I like it when the replies show some thought. Thank you. Now please tell me about X-pipes and their role on the Lightning (is there one).

 

Good one WC, I'll play a round.

The word scavenging has only been mentioned by Silver01. An exhaust "header" is designed to scavenge the cylinders at a specific RPM with negative wave pulses timed to meet the cylinder when both valves are open. The flow momentum created when these negative waves collapse in the cylinder can have significant results on a normally aspirated engine with EQUAL length exhaust tubes (and only 14.7 psia to fill on the intake side). On a ‘boosted’ engine, the momentum effect attributed to the ‘header’ is less with 22+ psia available for filling. ‘Long-tube’ headers will have a greater scavenging effect with at lower RPM and ‘short-tube’ will have more effect at high RPM.

Now for some advertising dribble from Dr Gas ( http://www.drgas.com )

The Dr. Gas Crossover

Remember that radio and TV commercial about the piston engine going "Boing-Boing," when it out to go HUMM? Well, all V8 engines with 90 degree cranks, have an out of sync imbalance in their firing order between the right and left cylinder banks. Yes, they do go "Boing-Boing." The firing order imbalance is a necessary sacrifice for dynamic balance of the rotating and reciprocating crank, rods and pistons. Each time the firing order is completed (two full revolutional), two cylinders within each bank will fire and exhaust within 90 degrees of each other. These two cylinders will be exhausting into the header collector or exhaust manifold almost simultaneously. This overlapping condition creates a lot of back pressure and a pop sound. Meanwhile, the opposite exhaust manifold has no activity (or pressure) in it at all. This is where the characteristic, low harsh popping V8 sound comes from.

The most common way of reducing this out of sync imbalance is with rebalancing crossovers such as H pipes and over-and-under X style crossovers. These provide both noise reductions and efficiency (power) improvements. H pipes are effective only at low and mid range. The over-and-under X crossover works a little better but still does not completely rebalance the exhaust at high RPM.

Dr. Gas, Inc. has developed a new generation of crossovers that uses a tangentially siamsed junction, in place of the H or over-and-under X. It evenly splits, smoothes, and synchronizes exhaust pressures at all engine speeds. The high and low pressure pulses in the two pipes are evenly imposed on each other, leveling out the pulse time history pressure differences between right and left cylinder banks. Re-synchronizing the exhaust pulses reduces back pressure, cancels sound, and provides additional scavaging. Tests have sound 6 dBa (75%) reduction in sound levels, and increases of 10 to 30 hp, and up to 40 ft-lbs. of torque! Economy, and throttle response are improved. Exhaust flow after the crossover is completely smoothed out. The job the headers started is finished.

One of the most appealing benefits of this system is the modified exhaust note. The deep growling and popping sound is replaced by a higher pitched smooth sound. The exhaust note is similar to a 180 degree header system without the nightmare of tubing.

Dr. Gas crossover kits replace the first 3 to 4 feet of the exhaust system with pre-bent mandrels pieces. Simply measure, cut and weld into place. The system is universal fit for most header applications. After the crossover, any type of dual exhaust, converters, or mufflers may be used with little or no effect on power. Vehicles that have problems meeting sound limits at local area tracks can also benefit with an increase in power tool. And so, the piston engine can go HUMM!

 

I've got a fabricated x pipe in place of the muffler. It was made by a fellow L owner who thought it was too loud for him while towing his race car. He sold it to me for the $75.00 he was in it for. Do a search here titled "x pipe" and read more posts. It bolts right in place of the muffler, which has not been back on since the install. It does drone a little at 70 mph, but I have had nothing but compliments. I did run a friend with a 68 camaro SS 383 stroker who said it was obnoxious as I passed him on his left. These pipes singing next to an open window must make a statement. I know they don't hurt performance either since I have serious traction problems with an airaid (front panel removed) and a R9 superchip. I now will smoke them through most of second and once hit third spinning on stock F1's. I am anxious to see how my new x mas gift hooks up at the track (MT ET streets 26 x 11.5 x 16).

 

Thank you Joel. I knew that you could explain it. The sound of a true X-pipe on the Lightning is one to behold and the power is there too. Thanks again.

 

Correct. Scavenging also aids a normally aspirated engine to draw fuel into the chamber, and also out of the chamber over the exhaust valve to cool the tips. Since some L owners have documented a loss in torque at lower RPM's, my GUESS is that too much fuel follows the exhaust into the exhaust manifold. When the RPM's go up, the velocity of the exhaust gas doesn't keep pace relative to the RPM, thus the torque is back up to "pre header" levels.

Regards,

George
(who would love a loping idle, rasping exhaust note and 6500 RPM Lighting - yet still happy with it as is!)

 

Yes i have a magnaflow just for a little more growel! i don't believe it helped with TORQUE! JL

------------------
93 cobra 10.90@127.00
99 lightning (black)
E.T. 12.07
best mph 112
60 ft. 1.65
(All Throttle No Bottle!)
JL ram air
JL Powercooler
2# pulley
Level 10 shift kit
Test Converter!
DiabloSport Dist.!
(KEEP IT BETWEEN THE LINES!)
_ _ _ _ _ _ _ _ _ _ _ _ _
JohnnyLightning Performance
E-mail: jlightningracing@cs.com
WEB:JohnnylightningPerf.com
svtperformance.com

 

The guy from Lightning Performance (Mike ??) wrote a post over on SVTPerf. web site. He says he measured the back pressure at the inlet of the stock muffler and it was 3psi, he also measured the back pressure between the stock exhaust manifold and the pre-cat and it was 11+ psi. Sounds like good info to me.
One thing I've noticed is that there are a lot of trucks running 12's now with stock exhaust, but they all seem to be stuck around 104 to 106 mph. ( thats were my truck is at) But if a truck has even a muffler on it the mph seems to go way up.
If you look at Sixpipes times that he posted,his truck is cookin (over 110 mph) and correct me if I'm wrong, but I think he is the only one in his group that had headers and a muffler.
Dale

------------------
Black 00'
12.98 @ 105.85
full weight, stock F1's
stock exhaust

 

That is just the extra thrust from the exhaust velocity helping them out

 

Newbie.....this thread has been left alone for a year and 3 months but thanks for the input

And besides wouldn't the "extra thrust" push them sideways down the track.......remember we do have side exhaust

--Joe