RPMs and Mufflers
Thread Starter
Team Owner
Joined: Sep 2002
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From: OBAMA IS HITLER
RPMs and Mufflers
I have a question that has had me intrigued since I replaced my stock mufflers with more free-flowing targa mufflers. Among several good things, the RPM range has increased between shifts. However, I noticed that cruising
in 5th gear went from about 2400 RPMs (stock mufflers) to about 2700-2800 RPMs (targa mufflers). Can someone explain this for a dummy like me? Is there a way to offset this effect so that crusing RPMs can be reduced back to original levels? I would think that the higher RPM cruising is a negative, not a positive. Thanks! :seeya
in 5th gear went from about 2400 RPMs (stock mufflers) to about 2700-2800 RPMs (targa mufflers). Can someone explain this for a dummy like me? Is there a way to offset this effect so that crusing RPMs can be reduced back to original levels? I would think that the higher RPM cruising is a negative, not a positive. Thanks! :seeya
Team Owner
Joined: Sep 2001
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
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Re: RPMs and Mufflers (bradvette)
You were doing 2400rpm at what speed? And at the same speed youre doing 2700rpm?
:confused:
The new mufflers should make it rev quicker, but not rev higher like that.
:confused:
The new mufflers should make it rev quicker, but not rev higher like that.
Thread Starter
Team Owner
Joined: Sep 2002
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From: OBAMA IS HITLER
Re: RPMs and Mufflers (vader86)
70 mph in both cases. I thought it was a little strange that with the KBD's that it cruises at about 2800 instead of about 2400 RPMs with the stock mufflers. Any ideas? Everything is otherwise stock, nothing else changed and everything seems in fine working order.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
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From: Australia
Re: RPMs and Mufflers (devilfish)
Someone has changed your diff gears or your clutch is slipping Bad!
Seriously , Mph v Rpm is set by the gearbox / diff gear ratio/ tyre size.
This ratio ( a certain speed for a certain rpm) can only change if one of the above physical changes is made.
Seriously , Mph v Rpm is set by the gearbox / diff gear ratio/ tyre size.
This ratio ( a certain speed for a certain rpm) can only change if one of the above physical changes is made.
Thread Starter
Team Owner
Joined: Sep 2002
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From: OBAMA IS HITLER
Re: RPMs and Mufflers (rodj)
Explanation makes perfect sense, thanks you for that. The clutch is not slipping its solid as a rock. I guess that gear fairies came by and changed out my 3.33's to 3.07 :eek: :D Whelp, I'll chalk it up to the Outer Limits phenomen :lol: ist only a small difference anyway :seeya
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From: tucson AZ
St. Jude Donor '04 & '05
Re: RPMs and Mufflers (bradvette)
Must install the FlowMaster mufflers....they are the best...I've said this over and over.....pick up on it....and get better performance...You bet!!!!!!!!!
tony
:flag
tony
:flag
Burning Brakes
Joined: Feb 2002
Posts: 871
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From: Union KY
Re: RPMs and Mufflers (bradvette)
Brad:
If you're not jerking our collective chains, the problem is that your tach is incorrectly reporting the engine's RPM's.
As stated here by others, the mufflers CANNOT effect the speed at which the engine turns at X MPH. That is only controllable by the overall ratio of the drive train.
I'd go have a scanner connected to the diagnostic port to see if agrees with your tach. I'm betting it doesn't. You may have a bad tachometer control head. BTW, I think it controls (or contributes to the Computer's oversight) of a passel of engine controls, so it really needs (as in avoiding $$$ engine damage) to function correctly.
Cire96
If you're not jerking our collective chains, the problem is that your tach is incorrectly reporting the engine's RPM's.
As stated here by others, the mufflers CANNOT effect the speed at which the engine turns at X MPH. That is only controllable by the overall ratio of the drive train.
I'd go have a scanner connected to the diagnostic port to see if agrees with your tach. I'm betting it doesn't. You may have a bad tachometer control head. BTW, I think it controls (or contributes to the Computer's oversight) of a passel of engine controls, so it really needs (as in avoiding $$$ engine damage) to function correctly.
Cire96
Team Owner
Joined: Sep 2001
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Re: RPMs and Mufflers (bradvette)
I'm thinking your tach filter has taken a crap on you, its a common problem with late L98s.
Thread Starter
Team Owner
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From: OBAMA IS HITLER
Re: RPMs and Mufflers (vader86)
Thanks guys, I'll bet it is a faulty tach reading. Its only coincidental that this phenomenon occurred shortly after I put the new mufflers on. I can live with that though. I appreciate your efforts in helping me out with this one! :cheers: