1 thing ive found about the stock exhaust is that ford did thier homework! without a doubt there are countless lightnings out there running 12's with NOTHING done to the exhaust. i believe these engines and the way thier designed are really geared up for TORQUE not HP. and as we all know TORQUE is usally made down low not high in the rpm range. i believe when we "free up" the exhaust on these engines we are taking away from the TORQUE. which these HEAVY trucks need to get em going. we are trading much needed TORQUE for lets say some minamal hp gains which are at the top of the rpm spectrum exactly where these trucks don't need it. these trucks are HEAVY and need TONS of TORQUE! therefor i believe whatever we can do to get more TORQUE from these awsome machines the faster we will go! i'm not just praising my truck here just using it for an example my truck goes 12.0's and i still have the stock exhaust! that should speak volumes for the engineering of the stock exhaust. JL

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93 cobra 10.90@127.00
99 lightning (black)
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best mph 112
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_ _ _ _ _ _ _ _ _ _ _ _ _
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svtperformance.com

 

Well said in referring to Torque. Horsepower is always viewed as the most important source
while Torque is second nature and overlooked alot. My motorcycle buddies with there 700 pound bikes strive for those HP #'S AND I push for the Torque to carry the load, and put that strong pull in the seat of my pants.The Torque is well needed to launch the weight of the L.

 

But what about torque JL? You think that maybe a factor?

------------------
Red '00 Lightning,
Power Surge Performance enhanced,
Sound effects provided by Flowmaster,
375 RWHP,
445 RWTQ,
12.974@104.818
Track Videos

 

4D THNDR -

If all you care about is big boost numbers, stick a couple potatoes in the tailpipes and watch how much boost you get!!

Big boost isn't everything!

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La dee friggin' da!




[This message has been edited by ladeefrigginda (edited 03-26-2001).]

 

As a general rule a blown motor (super or turbo) will respond favorable to a free flowing exhaust. The L exhaust is obviously excellent from the factory since changing it doesn't help performance. More compression equals more power no matter how you achieve it-more boost or by static ratio. A lower static ratio with higher boost will generally be doggier when off the boost than a higher compression/lower boost combo but the higher compression might not run on pump gas. Speaking of-the formula to compare the effective compression ratio of blown to N/A is: (boost psi/14.7)+1 times motor compression. Example 10 divided by 14.7 plus 1 equals 1.68 times 8.4 equals 14.11 This is basically to say take your blower off, jack the motor compression to 14 and the performance should be the same. The difference is it would be way snappier around town but you'd hafta run race gas all the time.

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2000 Silver L #4906
Best 1/8th mi stock:9.13
Best with R9 and new motor: 8.50 at 82.5
1995 Stang : (wifes'car) 12.30 1/4 mi
1972 Skylark: 7.16 1/8, 6.70 on the bottle

 

Exhaust systems can be tricky. Larger diameter pipes don't necessarily mean better performance. Taking out bends in the system usually buys you something. Remember that after combustion, the exhaust port opens and a pulse begins flowing down the exhaust pipe. Then, usually before the piston reaches the bottom of the cylinder, the intake valve also opens up. The purpose of this is to allow more of the exhaust gases to exit the cylinder. Think this is called cylinder scavenging. Anyhow, that pulse of hot gases that was sent down the exhaust pipe actually helps to pull more intake mixture into the cylinder. With a supercharger, scavenging can be more thorough. The diameter of the exhaust pipe is critcal to maximizing this process. To small and you'll see power at the low end but nothing at mid or high rpm. Too large and you'll lose performance at the low and mid ranges. Also, the length of the pipe comes into play which affects performance. Ideally, the exhaust pipes would be variable length and diameter controlled by engine rpm. Well, we can always dream!

 

I knew this would get interesting! I also know someone that is making well over 360 RWHP on their stock motored Lightning without the use of a chip. Just some good old intake and exhaust tuning. NO Ported Heads.

[This message has been edited by WCFan (edited 03-26-2001).]

 

i go with J.L. on the torque business.Its torgue that propells vehicles with H.P. as an important,but not THE important by product...especially on a heavier vehicle like a truck.This explains how a 4900 pound Super duty powerstroke can do a 17 sec. 1/4 mile with only 220 h.p. but with 500 ft/lbs. of torque.And why v-10 will lose to a deisel in a sprint, even though the V-10 has more H.P. One of the quikest muscle cars from the factory was a Buick GS 455.It had about 80 horses less than a 454 Chevelle SS yet the Buick posted slightly quicker 1/4 mile times(same weights and gearing) than the Chevelle.The difference was the torque and the infamous power under the curve.yes H.P. is a key element, but only whwen combined with a good torque figure designed in conjunction with the weight of the vehicle for usable and streetable performance.this is one reason I do not think that Ford will opt for a 4 valve head.Its a peaky motor and though may produce higher "peak" numbers, would definatley hurt the L's infamous Torgue numbers.A three valve engine,you ask? Well that might be a completley different story altogether!

 

If you would have read my second post you would have noticed that was covered.

Automan, thanks for the formula. It had been stated by another that we were around a 14:1 compression with the boost.



------------------
Red '00 Lightning,
Power Surge Performance enhanced,
Sound effects provided by Flowmaster,
375 RWHP,
445 RWTQ,
12.974@104.818
Track Videos

 

What is power under the curve? What do you mean when you use that term? Is there an example such as a graph that can explain it. Thanks fo all the info so far.

 

What about an X-pipe? What would that do?

 

WCFAN- Simply put "power under the curve" refers to the overall power or the power that is not necessarily the "peak" H.P. Example: Truck "A" puts out 350 H.P. and Truck "B" has 340 H.P.. Both at 5000 rpm.One would think that truck "A" is faster.,what is not shown is that truck "B" has the following h.p. data: 3000 rpm-320 h.p., 3500 rpm.-330 h.p., 4000 rpm.-345 h.p., where Truck"A" has 3-4 h.p. less at these rpm's.Therefore the usable power at these lower rpm's is in favor for the "B" truck.Hence the term power under the curve ,meaning the plotted h.p. or torque curve on a dyno chart.This is the all important curve for a desirable street machine.Hope that explains it.(its a lot easier to see on a dyno chart comparo)

 

Will the real William Claude Dukenfield please stand up.

 

JL,

I thought you were running a Magnaflow?

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Later,
Chuck
Black 00
Chuck's Lightning Page

 

Mondo1 hit the nail on the head regarding the curve. As long as the gearing is correct, the greater the area is under the curve, the greater performance the truck will have.

Here's my thought regarding minimal performance gains from exhaust modifications:

Cam lobe design and the exhaust/intake overlap. My guess is that the exhaust is tuned very well to the stock grind. Maybe with a different cam grind, the exhaust might become a factor.

------------------
Regards,
George
george@spikeengineering.com
http://www.spikeengineering.com
---------
Red 2000 Lightning, #4033
White 1996 Whippet (1/2 mile course, 6 turns: 40 Seconds)
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