new best time, baby steps now.

[HICKL]

I did the Import face off at Houston Raceway park this sunday and knocked a few my tenths off my best time. I squeezed out a 11.516 at 118.41 mph(prior best was 11.72ish). I hadn't turned a wrench on the car since my 11.72, but it was about 35 degrees colder yesterday, I guess the car liked it. I think that's about all she's got, may be time for NOS...

[grumpyvette]

first congrats on the new best time!

what carbs/intake are you currently running?

whats the rpm your going thru the lights at?

are you getting a good 60 ft time?

is that 118 mph trap speed consistant?

whats the car weight with YOU in it?

[HICKL]

first congrats on the new best time!

what carbs/intake are you currently running?

whats the rpm your going thru the lights at?

are you getting a good 60 ft time?

is that 118 mph trap speed consistant?

whats the car weight with YOU in it?

 

Perfomer RPM, holley double pumper.

I am grabbing 4th right at the end, not sure of rpm

60's are in the 1.62 to 1.68 range.

did 2 118mph's in a row, in the summer 117 was my best.

can't remember exact weight, seems like just under 2900 lbs.

[mr_denner]

congrats on the new best time

good luck

[grumpyvette]

as I mentioned before, a good set of LONG tube custom built headers, added to the combo too replace the shorties your now running and a better low restriction exhaust behind it will build on the combos results.

your probably down a couple tenths due to the lack of an ideal exhaust scavaging combo

[grumpyvette]

A GREAT DEAL of the results will depend on the exhaust header design,MOST commercial headers are designed with low cost and ease of installation in mind rather than max scavaging and max HP. but the exhaust restriction level behind the headers can kill most of the potential results from even the better designs, if your not willing to change the whole system to optomize the results then a stock or modified stock or shorty headers will be a decent choice, if the FULL LENGHT HEADERS are MATCHED to a full length, 3" exhaust with an (X) that will significantly lower the restriction to flow rates. the stock corvette exhaust manifolds tend to be far better than most stock exhaust manifolds but they still fall far behind what a decent set of full length headers and a low restriction exhaust will do for your cars power.

design the system correctly and you can significantly increase the exhaust scavaging of the cylinders and increase power,do it wrong and youll hurt power.

 

http://www.sjdiscounttools.com/waebpt01.html

 

readings above about 1.5 psi usually indicate a restriction thats costing you power.

 

the main IDEA is to REDUCE restriction and EQUALIZE the flow, AND INCREASE the CYLINDER SCAVAGING to help power by increasing the cylinder filling efficiency. side benefit is usually a more mellow exhaust tone

lets say your car has two 2.5" exhaust pipes, blending the flow thru use of an (X) doubles the area and cuts the restriction almost in 1/2, plus if designed correctly it helps scavaging, a single 2.5" pipe cross section is approximately 4.9 SQ" a single 3" has approximately 7 sq inches of cross sectional area, so adding an (X) effectively reduces the restriction almost in half but stepping up the size and adding an (X) beyond the header collectors does far more at reducing the restiction

 

THE (X) BY FAR is more effective, the (H) may equalize the pressure to a great extent but the (X) blends and exqualizes the flow,

 

http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm

 

http://victorylibrary.com/mopar/lcb-c.htm

 

http://victorylibrary.com/mopar/header-tech.htm

 

http://www.engr.colostate.edu/~allan/fluids/page7/PipeLength/pipe.html

 

you can easily meassure this, get a pressure gauge and drill a 1/8" hole in the exhast behind the headers and bring the engine up to full throttle with the gauge attached, (I usually suggest running thru the gears on a semi hard accelleration test run with a partner in the pass seat watching the gauge readings, with a temp test line to the gauge running into the cab thru a window.

 

whats the differance?

lets say for the example the exhaust pulse is a quart to water moving at several hundred feet per second, but unlike water it can be compressed,since the exhaust pipe inside dia. is set the length of the pulse or slug of exhaust exiting the engine every 90 degrees of rotation (v8) has inertia/energy/mass, if it passes a right angle low pressure exit point, at first it flows into both routes but as the mass passes the opening a slight negetive pressure forms and it reverses and the flow changes, put a vacuume gauge on the (h) and it vibrates, wildly.

install an (X) and the flow from both sources is FORCED to BLEND, line up, equalize and BOTH sections of the up stream flow benefit from the

as each inertia/energy/mass, and slight negative pressure that forms, but its far more equalized. gases unlike liquids will expand to fill any void.

put another way if one side was pumping out dark green water and one side was pumping clear, an (H) would have dark green exiting one side and light green exiting the other, an (X) would have both sides an equal, slightly lighter green flow .now at low rpms , or with a smaller than ideal pipe dia. thats no big deal, but at high rpms, BOTH the SCAVAGING of the cylinders your trying too scavage enhances the effect and the reduction of the restriction to flow tends to be better with the (X) put a vacuume gauge on the (X) and it vibrates. but not to nearly the same extent, and the changes in pressure reading remain more consistant

 

BUT,DON,T be thinking that either is a mandatory huge improvement, it may or may not help the power, the degree of restriction, displacement, compression ratio, cam timing and the efficiency of the headers has a good deal to do with your results, and sticking restrictive mufflers on past the (X) or (H) can effectively kill most of the potential benefits