I have a stock 2002 automatic that i suddenly have the urge to modify after last weeks Cruisin OCMD muscle car show. while there i discovered there was a such thing as electronic exhaust cutouts. My goal with the car is to increase performance and give the car some serious grumble. i do like a relatively quiet ride though, so i thought these electronic cutouts is just what i need. However... i was wondering if anyone knows how the performance will be affected by tuning the car with the cutouts opened and then cruising with the cutouts closed when im just commuting every now and then. Would running the cutouts closed on a tune thats based on the open cutouts affect my engine in any way? Presumably knocking/misfires?
all insights is appreciated. Long term goal is nice headers to the cutouts and an aftermarket intake and/or supercharger.

 

Jay

Seems every one wants a killer sounding exhaust system. I did too. I was one of those people that found it VERY DIFFICULT to spend $1000-$1500 on a set of cat back mufflers. Most CAT back systems will give you an additional 10-12 Hp on a relative stock LS-1.

SO,,, I had the idea, Why not go STRAIGHT PIPES! Not wanting to hack up my 98 Coupe exhaust system, I made 3/4" metal spacers and obtained some longer exhaust muffler flange bolts. I put the spacers between the mid-pipe flange and the muffler flange. The gap between the flanges allowed the system to see and open exhaust.

HOLY CRAP! It sure was LOUD but, along with LOUD came a very guttural sounding exhaust note and a WHOLE BUNCH of in cabin drone!!! I CAN HANDLE loud BUT THAT drone can actually make the car very unpleasant to drive. I kept it that way for approx. 6 months. The drone was just too much.

A well designed muffler system cancels out the drone and lets more DB out.


- As for performance. Yes, you will gain some performance. with an open exhaust system. Nothing to write home about. Remember... Change MUFFLERS for a different SOUND. NOT MAJOR HP increases. I know plenty of people who are at the 500 RWHP mark and run ZO6 Ti Mufflers. They are basically straight through chambered mufflers with a little stainless steel wool on the outlet pipe.

ZO6 Ti Cut Away Muffler:



- Will it hurt anything?? Your PCM is very adaptive. It will use the LONG TERM and Short Term fuel trims to make the CLOSED LOOP 14.7:1 AFR

JUST SAY,, Your engine went a little lean when you UN CAP the exhaust system. Your LONG TERM FUEL TRIMS would increase the percentage of fuel to increase the AFR to correct for the lean issue.

Most all OEM C5s are a little rich in the AFR department when you go into Open Loop Mode and enter Power Enrichment (PE) mode, i.e. "HAMMER THE THROTTLE" I think it some where around 75% throttle..

That being said,, a rich PE AFR doesn't make as much power as a PE AFR thats properly tuned. With your already rich OEM PE AFR,, the PCM will take that percentage of LONG TERM FUEL TRIM (added Fuel) and ADD it to the already rich AFR PE.

Long story short,, You would need a tune to get everything spot on so you could run in the noise mode and not have a way rich PE AFR.

 

I've been running electric cutouts on my 99 FRC for about 12 years. It doesn't seem to make a huge difference either way, except for the loudness level of course. Never had any problem with the tuning and did not make any changes at all when I installed them.

Dope

 

My question is if i get my vette tuned with the cutouts open and gain said number of horsepower. Now all of a sudden i close the cutouts with the car still tuned to the open cutouts. Will the pcm adjust to the sudden restriction of flow (as little as it might be)? Will the car still run well with the cutouts closed but not tuned to that setting or would i need one of those flash tuners or whatever to switch it back to closed mode?

Edit: i want the electronically controlled cutouts that i could open from the cabin while driving to show off or be that guy with a mean sounding car. Along with that i could adjust the amount of open/close the butterfly valve is to almost tune the exhaust sound

 

These are my QTP cutouts with a switch mounted in the center console where the accessory power outlet used to be. I have XS-Power long tube headers with cats then into Z06 Ti stock exhaust. With the cutouts closed it has a nice idle, sounds good at WOT and no drone. With the cutouts open it just sounds plain nasty. I have noticed no ill effects regarding the tune open or closed.

 

Anything done to the engine or intake?
cause that is almost exactly what what i want lol

 

Yes. It is a 2000 6 speed coupe: LS6 ported intake and throttle body, RHS Pro Action 205cc ported heads with 2.02 intake valves/1.60 exhaust valves, TSP 224R cam on a 114LSA, and as mentioned long tube headers and Ti exhaust.

 

Wow that thing probably sounds like godzilla or some ****. How do you think it would sound with a nice longtube header and a good intake? Or stock with cutouts even

 

OK I assume you are talking about your vette. Even stock with cutouts will give you a very strong sound. Adding the headers, intake etc. will only back up that sound with performance. Having said that just keep in mind that it is a balancing act. In other words plan what you want then get advice about what works together to produce the optimum gains. Just dropping that monster cam in without supporting and complimenting other mods will hurt more than help. Do a little searching on the forum and you will come up with a ton of good advice.

 

Yeah this is my first post on here and i figured exhaust/intake is the best first stepp of modding. Thanks for the advice in laymens terms

 

Just do all you Mods that you want and then tune the car in the 90% condition that you will be NORMALY driving it.

Then the 10% will be easily compensated by the PCM. NO ISSUES..

You CAN NOT hae a TUNE to cover 100% if you do something that effects/changes air flow through the engine.

You want that change to be on the ABNORMAL driving side of the clock.

BC

 

Cutouts as muffler bypass

 

Innovative idea. Mine as pictured are tucked up on each side of the tranny and the motors and wiring wrapped in heat shield. Do you have any concerns the way yours are positioned closer to the ground as pictured? I would imagine though that placed so rearward they pass less noise into the cabin.

 

They're above the subframe so I'm good but I'm going to make a piece
of angle as a barrier shield to cover and protect the motors and wires since one got snapped when I ran over a dead critter in the middle of the road at night on the highway

The cutouts can also be turned almost 180 deg with the motors in the underbody but fabbing them this way was easier.

Mine is about 10 db louder open and it flows almost straight out vs your 90 degree exit.
I can run with it open without fumes under the car since it goes out the tail pipes.
It sounds real sweet

 

The cutouts as muffler bypass looks awesome but also looks like a pain in the dick to weld as compared to the traditional way

 

The Pep Boys cutouts are 3" and come bare
so I had to make something.
That's when I thought of a bypass.
I bought some 3" pipe, gaskets and flanges from a muffler shop.
Making this wasn't much of a challenge for me.
I used to be a bodyman so this is nothing I can't do.
Did this mostly with a 1/8" cutoff wheel on an electric grinder
and a dremel like air tool.
I like making stuff like this
There's lots of overlap 3" over 2.75" so that makes it easy
to weld it up.
It also comes apart should I need to replace a cutout.

 

Yeah after thinking about it it doesnt seem too bad Except for the close quarters parts by the muffler. What kind of weld did you do?

 

I didn't weld them on the car.
Drew the lines where the cutouts went after
fitting them to the car then took the mufflers out,
cut the holes in the pipes and welded them in.
Used a MIG welder with Argon gas.

 

No i know you didnt weld them while they were on the car but the section in between the muffler and cutouts seems a little tight but its hard to tell by pictures.

 

Plenty of room to do this.
This pic shows how close it is to the muffler.
You could make it further away and turn the
cutout 150 degrees.