Backpressure with muffler delete?

[shojoe1997]

I have a 98 sho. I wanted to know if you do a muffler delete does it make a difference with backpressure and performance? Also is it too loud, will it drone while driving to an unbearable point. Its stock. All 3 cats, silencer cone all in place

Thanks Joe

 

[stephen newberg]

Yes, removing the mufflers will have an effect. It tends to move the power curve a bit toward the higher end, and some have reported it also decreases overall output a small amount.

Will it be loud? Yes, very. Most people seem to find it way too much for normal driving, but a few seem to like it that way. If you want to bring out the sound of the V8 but do not want to have full time no mufflers, there is some sort of a muffler bypass that can be shifted on and off, IIRC, though I do not know who makes it or if it is still available. Or you can go to some 3rd party mufflers. I am running Flowmaster 40s these days in combination with Magnaflow cats and find the result very pleasing without messing about with the performance of the engine to the negative side.

pax, smn

 

[RonPorter]

When I had my V8 and was ready to change mufflers, I had the shop delete the mufflers and run through the tips. That lasted for a week!! WAY too loud, it droned, and it felt slower.

Put in turbo mufflers the next week, and the car felt stronger again.

Also, a few folks had deleted the 3rd cat. Then they reinstalled it, and found some midrange torque that they didn't notice losing when they removed the 3rd cat.

It's a small engine in a heavy car, running through an automatic, and it's tuned for higher rpm power, hence not a lot of useable torque through the midrange. You don't want to lose any of it!

 

[shojoe1997]

Thanks. I think I'm going to do magnaflow or flowmaster with a 3rd cat delete

 

[shojoe1997]

How do the flowmaster 40s sound. I've heard flowmasters sound tinny from a guy who had a v8 mustang, I don't know if its the same for the v8 sho. Are you happy with the 40s. My local auto zone has Flowmastern40s and I was thinking about picking them up

 

[stephen newberg]

You can probably find some videos with sound files about here somewhere. No, the Flowmasters are not 'tinny' at all. Very much a low and deep burble. On mine, anyway. The stainless 40s I put on have been great, and they were not hugely expensive. I think you will like the results.

pax, smn

 

[RonPorter]

Thanks. I think I'm going to do magnaflow or flowmaster with a 3rd cat delete

Mufflers are a personal choice, but DO NOT delete the 3rd cat! You WILL lose torque.

 

[stephen newberg]

I have to agree with Ron on this. Deleting the cats, including the 3rd cat, is an error if your goal is to have the car run as quickly as possible. Plus the obvious part about potential air pollution and maybe problems with vehicle inspections. But it will have less torque regardless, and that is from two of us with fairly fast Gen IIIs, as these things go.

pax, smn

 

[RICHARD ROWLEY]

I live in Alberta, Canada. I have no cats, deleted all 3. my 1/4 mile time went from 16.1 to 15.4 so ya you loose under 3300 rpm but the car pulls way quicker up to 6500 rpm.

 

[stephen newberg]

It would not be the cats that did that, Richard. Normal for this vehicle is a mid 15 time. The really interesting question is why you were getting the over 16 time in the first place. And it is simply wrong that the car is faster with the cats off, as has been determined a fair number of times with dyno work. Some of that is likely still posted, if you look about here or over on V8SHO.com

pax, smn

 

[RICHARD ROWLEY]

there is another v8 guy that had a exhaust cut out. he only got faster. i have done the dyno a few times. stock set up was 180 whp. done after changed plugs.coils. welded cams. all synthetic fluids. after dyno car was at 197 whp. i bought the car last may with 104,000 km on motor. original motor blew up, cam failure. I have a Ford esp. replacement long block. bill was $15000 in 2004, i pulled the records via vin. I drag race a Castrol in Edmonton. 2200 ft elevation. so 1/4 times are not that great comparing to sea level cars. the exhaust is very restrictive. 3.4 L engine should have 2.5 inch min. all that way thru. V8 SHO does not. I have a catless 89 SHO and dyno results showed 180 wTQ from 2000 rpm to 5000 rpm. on a dyno jet. cats are a restriction.

 

[SHOspazz92]

180 WTQ is what stock V6 SHO's make.

 

[stephen newberg]

Exactly. And as noted before, there is a lot of existing and correctly done dyno testing that shows not only no gain from an open exhaust on the Gen III, but in fact small losses in addition to alteration in the curve that will hurt quarter mile times from the low end.

Lets stop this now, as it is getting repetitive and misleading for people that are new to all of it.

pax, smn

 

[sho'noff]

you may need to upgrade your fuel system and add a free flowing air filter if you are going to make your exhaust more free flowing. but then how will you ever keep it under 90?

 

[intimdatr]

you may need to upgrade your fuel system and add a free flowing air filter if you are going to make your exhaust more free flowing. but then how will you ever keep it under 90?

Lol. So not true.

 

[sho'noff]

you got no idea

Lol. So not true.

It is pointless to open the exhaust and leave the rest alone.

 

[stephen newberg]

Actually, it is pretty pointless to open the exhaust unless you are trying to change the sound rather than gain power, which I think we have now gone over enough to hopefully not be leading anyone down the garden path. You can, however, change around the output curve a bit, with only small power losses, and you can certainly change the sound a lot, pretty much to anything you personally like.

pax, smn

 

[intimdatr]

It is pointless to open the exhaust and leave the rest alone.

Unless you plan on running cams or FI messing the with those thing you listed will gain you a net of nothing.

 

[sho'noff]

I am not sure on fuel injection but with a carburetor a aftermarket air filter and stock exhaust will richen your fuel mixture and foul your plugs
with a carb stock air filter and open exhaust will lean your fuel mixture and foul your plugs
either way you should not cut corners an air filter, exhaust and proper jetting(or ecu upgrade in your case) will add horsepower, throttle response and torque.
the super high output is fine from the factory as far as I am concerned.
you may be damaging your engine and looking at a valve adjustment sooner than factory recommended.

 

[intimdatr]

With fuel injection the ECU is more than capable or enriching and leaning the system with all bolt ons up to even some mild cams.