a well designed c4 exhaust

[grumpyvette]

theres plenty of math, but clearance issues, and packaging limitations, are the factor that limits what CAN, be done in most cases
remember an internal combustion engine works by use of producing rapidly expanding gases over a piston to produce pressure that forces the piston to spin the crank, those gas pressures exceed 600 psi and over 1000F temps, a well designed exhaust system will have a low enough restriction to exhaust flow that the max positive pressure will remain below 2 psi at peak rpms, and ideally less

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

http://victorylibrary.com/mopar/cam-tech-c.htm

http://www.corvettefever.com/techarticl ... index.html

viewtopic.php?f=56&t=91

MOST OEM CORVETTE EXHAUST SYSTEMS, AND SOME AFTERMARKET, ARE HIGHLY RESTRICTIVE
http://www.corvettecentralexhaust.com/c4/stock/systems/

http://www.parts123.com/parts123/yb.dll ... 000050Q~~~

http://www.parts123.com/parts123/yb.dll ... 1~cadefibQ

Id also point out that cam timing matched to the exhaust scavenging has a huge effect on potential intake flow rates




first ID advise STAINLESS as the material used in an exhaust and 2.5 minimum,pipe size 0r better yet 3" pipe size aft of the header collectors feeding into the (X) pipe, IDEALLY for size, on the pipes on a performance exhaust.especially with nitrous and ideally with
the (X) pipe located as close to the two header collectors as under the car clearances allow.(IDEALLY) if your forced to use an (H) pipe and ONLY if forced, by clearance issues, it ,should be as close to the header collectors as the available space/clearance allows, also, thats generally near the front u-joint due to the trans pan required clearances, the OPTIONAL second (H) to lower resonance, should be installed connecting the two exhaust pipes just in front of the muffler entrances

http://www.melroseheaders.com/products/smooth_flow_exhaust_systems/c-4.php





Id buy this or duplicate this EXHAUST,and add an (H) where it connects to the mufflers, similar to this
the second (H) goes a long way to destroy resonance

http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUM%2D642030&N=700+115&autoview=sku

viewtopic.php?f=56&t=10419

the idea is to minimize flow restriction and maximize cylinder scavaging in the rpm range youll operate in the majority of the time[list=][/list]

[grumpyvette]

What is the stock stall speed for a '85 Corvette 700R4?
and what can I do to boost the responsiveness, or way it responds when I jump on it without throwing huge amounts of cash into the project? Thanks,

most early TPI stock converters on stock TPI engines stall at about 1900-2000rpm,the stock TPI intake,manifold design , while very effective at producing low speed torque, is very restrictive to air flow above about 4500rpm as it was designed for a 305 displacement engine originally, and the cylinder heads, cam and exhaust are all very restrictive to air flow over 4000rpm, and the stock cars came with pathetic 2.57:1-3.07:1 rear gears too increase or add decent mileage and reduce emission test results at the expense of performance.
keep in mind that what goes in , needs to exit at a low restriction or it reduces the potential power and that your engines generally far more efficient in the mid rpm ranges at producing power, so keeping it there as much as possible helps your car run more effectively, in that theres more efficient use of available power.


swapping to a 3.54:1-3.73:1 rear gear and a 2800-3000rpm stall converter even with the stock engine gives a very noticeable improvement in performance but requires an additional trans fluid cooler,and benefits a great deal from a cam upgrade

on the early flat tappet cam TPI versions the crane 114132 has proven to be a trouble free and welcome upgrade worth 30-35 hp and its especially effective with 1.6:1 roller rockers and new valve springs and long tube headers


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[bytor]

I replaced my from Y pipe a while back due to a rattling pre cat. I went with the Magnaflow 93987. Nice mandrel bent piece. Here's some comparison pics with the stock unit. The crimp bends on the stock unit are a performance killer. I do notice a little improvement on the low end, feels more torquey. Also noticed a very slight increase in drone around 1400 RPM, It's not horrible and something I can live with.

When I got the car it had muffler eliminators on it. Like these, http://www.ecklerscorvette.com/corvette-quad-power-mufflers-stainless-steel-quad-zr1-style-tips-1984-1991.html It has a nice rumble at idle.

Grumpy, have you used muffler eliminators on you C4's? If so, whats your thoughts of them?

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[grumpyvette]

Exhaust noise is the perceived vibration or resonance caused by the high pressure pulse of exhaust gases exiting the engine in strong intermittent pulses that match the engine rpm, you reduce the perceived noise by absorbing or dissipating the strength of the individual pulses and by damping or blending the low and high pressure peaks in the pulse strength, this has been well proven, to be helped by adding an (X) pipe to the exhaust as it effectively doubles the cross sectional area,of each header collector if the exhaust pipes are the same diameter past the (X) thus instantly reducing the gas velocity and blends the pulsed thus effectively changing the two exhaust pulse per cylinder bank per rotation into four less intense pulses past the (X) pipe , this also tends to equalize the exhaust flow rates, reduce flow restriction and thus change and in most cases MELLOW or LOWER the strength of each individual pulse by interrupting the original frequency range caused by the engines exhaust pulse strength in the process.

Ive found that mounting DUAL in series (X) pipes has both a slight beneficial increase in exhaust scavenging, and a noise reducing tendency, the use of dual in series (X) pipes, very defiantly changes the rpm range and tone of any exhaust note!


several of my friends have chosen to install those muffler eliminators and obviously each of us has a individual tolerance for noise level and the type of exhaust note or rumble we prefer
I know many of the younger guys seem to like that raspy exhaust sound and I was amazed at how quiet the car actually is with no mufflers at all,just those muffler eliminators, if you run the dual (X) pipes but I think many of us older guys will still find mufflers preferable.
http://www.ecklerscorvette.com/corvette-quad-power-mufflers-stainless-steel-quad-zr1-style-tips-1984-1991.html It has a nice rumble at idle.
the C4 corvette with an engine that is designed to exceed 450hp will require a low restriction exhaust, it would generally help to have long tube headers and a 3" dual exhaust with (X) pipes behind those header collectors and dual 3" inlet mufflers would in most cases help power output over the OEM exhaust design

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