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#1 |
![]() Join Date: Feb 2024
Location: Fairfax, VA and Springfield, IL
Posts: 42
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My new-to-me 1990 has the old style Billy Boat exhaust and the drone is absolutely unbearable for me at all cruising speeds in 6th gear (1700-2400 RPM). It currently has OEM manifolds but I plan to install Maximizer/OBX headers with either 200 or 400 cell cats.
I've learned of several ideas/concepts that have worked for other vehicles with different exhaust systems, more space etc: 1) Welding in a j-pipe or Helmholtz resonator before the mufflers; loads of videos on YouTube if you're not familiar (it's works but I'm not sure there is enough space under the vehicle for this) 2) Adding mass/weight to the exterior of the mufflers (maybe the engineers of the forum can better explain this) 3) Wrapping the mufflers in header/exhaust wrap (would this last long terms?) This is somewhat of a budget build/restoration for me and I'm trying to do the majority of work myself with the help of WAZOO and other members. Does anyone know of any other realistic and sustainable solutions or care to comment with their knowledge on the ones I've listed above? EDIT: Cost is a factor as the previous owner misrepresented its condition and the maintenance/repairs/restoration is starting to nickel and dime me. The previous owner powder coated the exhaust tips black to match the wheels which he also had powder coated black. If I get any different exhaust, new or used, I would also have to powder coat the tips to match the wheels. Last edited by ZBrink; 04-07-2024 at 09:15 PM. |
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#2 |
![]() Join Date: Jul 2020
Location: Nashville TN
Posts: 317
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Do not wrap exhaust. It will only lead to corrosion.
Do you have an x-pipe in the center just aft of the transmission? |
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#3 |
![]() Join Date: Feb 2024
Location: Fairfax, VA and Springfield, IL
Posts: 42
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I just double checked and I do have the x-pipe.
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1990 ZR-1 #299, Bright Red/Red 1998 Z51 Fastback Coupe, A4, Torch Red/Oak |
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#4 |
Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,697
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What Karl is describing is what was done w the C6Z. In order to reduce weight, Corvette went w an Xpipe rather than a resonator, and to duplicate the effect of the resonator, they adopted a muffler valve, the NPP. The system he described is what I now have on my ZR using a manual electrical switch to acivate the valves.
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[SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX |
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#5 |
![]() Join Date: Apr 2007
Location: Lake Bluff, IL
Posts: 2,067
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A good solution would be to get a Corsa exhaust, and if budget constrained, you might be able to find a used one. Marc Haibeck might have one, as might others on this forum. The resonance frequencies created by the LT5 and many other engines occurs primarily at two rpm points, about 1800 and about 3400, and they manifest themselves most noticeably under light throttle application. The Corsa system (like the stock system) utilizes Helmholtz resonators to tame them both. There is one in the center resonator that deals with one of the rpm points and there are Helmholtz resonators in each of the rear mufflers to tame the other. (I forget which handles which frequency). In the early days the Corsa was the only one to really quiet resonance other than the stock system. Today I believe there are other systems that do a fairly good job of it but not sure which. Others on the forum will undoubtedly chime in. Good luck with it. But I think getting a different exhaust system than the one you have is probably the most straightforward approach. --Bob
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2016 Long Beach Red Z06 #10281 "POPS Z" 1995 Polo Green #409 "WARP TEN"--Haibeck 350/510 package, 4.10s, Hurst, Stock Exhaust with QTP Cutouts --Sold but still running strong 1993 Quasar Blue #161 "HIL KING" --Sold but still running strong, now with more than 120,000 miles 1967 Marlboro Maroon/Saddle Corvette Coupe 300 hp/4-spd --Sold a long time ago ZR-1 Net Registry Founding Member #95 NCM Lifetime Member Favorite Quote--Attributed to Mickey Thompson: "Too Much Horsepower is Almost Enough" |
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#6 |
Join Date: May 2013
Location: Chicago
Posts: 978
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Either upgrade to their new system or try this. I deleted my resonator and installed an x pipe but have not done the NPP mod.
https://www.zr1.net/forum/showthread.php?t=22512
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1993 ZR-1 #211 Yellow On Beige Beast #2 1992 ZR-1 #427 Black On Black *Sold* 1985 L98 Blue On Blue *Sold* |
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#7 | |
![]() Join Date: Feb 2024
Location: Fairfax, VA and Springfield, IL
Posts: 42
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1990 ZR-1 #299, Bright Red/Red 1998 Z51 Fastback Coupe, A4, Torch Red/Oak Last edited by ZBrink; 04-07-2024 at 06:32 PM. |
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#8 | |
Join Date: May 2013
Location: Chicago
Posts: 978
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The new B&B is not in my goals now. If I upgrade my exhaust it will be a 3" titanium system to save weight.
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1993 ZR-1 #211 Yellow On Beige Beast #2 1992 ZR-1 #427 Black On Black *Sold* 1985 L98 Blue On Blue *Sold* |
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#9 | ||
![]() Join Date: Jun 2022
Location: Virginia
Posts: 84
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I'll err on the side of Warp Ten here and say you may be better off planning to get a new catback system that is designed more towards eliminating drone.
OBX/Maximizer has a catback system that is very reasonably priced on Walmart to match the headers you bought. From what I have read here on the forums and seen on youtube it has little or no drone. Quote:
By adding mass to the large surface areas you change the amount of energy required to hit that resonant frequency. That can reduce or eliminate it through the vibration ranges it will see use at. In sound deadening (for car stereo example) this is done by adhering sheets of butyl to the sheet metal panels to change the overall mass. You probably couldn't use the same stuff for the muffler because of the more extreme heat. Applying exhaust wrap to the muffler would achieve a similar effect, it is adding mass. Another option would be welding extra material to the muffler to reduce the size of the resonant zones and/or add mass. Quote:
The danger of exhaust wrap comes from it getting wet, and then holding that moisture against your system for a long period of time. Aside from the obvious things, like rain or puddles, moisture can also come from not allowing the headers/exhaust to get hot enough to force evaporation. There is moisture in the air, and some heat can cause that to condense inside the wraps. So very short errand runs can actually be bad if there isn't a longer drive to break those up. The risk here can easily be overblown. If it gets wet, at first opportunity take the car for a longer drive to build enough heat throughout your exhaust system and force any moisture to evaporate. Starting the car and letting it idle won't be enough to do this, the engine needs proper load to build the correct amount of heat, and enough time for all the moisture to be forced out. So consider your usage. Is it a daily driver? That might be a little higher risk if you expect to be driving it in the rain. Weekend cruiser? No problem, that is low risk. Last edited by Raykahn; 04-05-2024 at 05:17 PM. |
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#10 |
![]() Join Date: Jul 2020
Location: Nashville TN
Posts: 317
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I wish it was that simple Raykahn but I ignored the warnings on header wrap on an LT1 powered 383ci 94C4 and they rotted through in a year just as others had predicted. Car rarely saw any rain and all drives were long enough to reach full operating temperature. Lived in Detroit metro at the time, nothing was less than half hour. Car was never exposed to winter or salt either. Of course SE Michigan is humid.
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