I just got done installing SLP 1 5/8 headers, y-pipe, 3"catco cat and 3" Flowmaster muffler.I lost an incredible amount of torque down low in the off idle to 3,000 rpm range but the car pulls a lot harder starting at 3,000 rpm and pulls well to 5,000 rpm.I know its a trade off, but is there anything I can do to improve the low end torque? I had a 2 1/2" flowmaster muffler on the car originally and it sounded great but the 3" flowmaster muffler I put in is loud as hell to me and I was wondering
if I could get some torque back with a
more restrictive quieter muffler? does that make any sense/ Sure appreciate the help...bob



------------------
91 camaro RS convert,t-5 ultimate TBI mods,TBI spacer,SLP 1 5/8 headers,
3"cat back, 3.42 torsen posi,alston SFC's,Global West LCA relocation brackets

 

Can anyone anwser this question? I noticed it too when I put my 1-5/8" Edelbrock TES headers #6872 on my car, made a custom 3" exaust w/o cat and Flomaster 80 Series Muffler. I noticed a little bit of decrease in my torque as well but a lot better at higher rpm's. Should I find a high-flow cat and put one on? Would this help my torque or would it hurt me at higher RPM's?

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Eric Natzke
91 Firebird 305 TBI (ZZ4 summer of "01")
ASCD Ram Air Hood-3" custom exaust-Flowmaster 80 Series-No Cat-Edelbrock TES Headers (coated)-March Pulleys-TBI Spacer-K&N Open ELement-TransGo Shift Kit-B&M Supercooler 28,000 GVW-Hypertech Thermomaster-160 Stat-3:42 GM Gears-Auburn Posi Unit-Edlebrock Strut Tower Brace-MSD Superconducters-Accel Cap & Rotor-MSD Blaster Coil-Rapidfire Plugs-265/50/R15 Tires-Emmison's all Gone
http://members.aol.com/j007golden/91firebird.html

 

guys there would really be nothing u can do to the exahaust to get torque back unless u want to purposely restrict it more. Ur now gonna have to do different mods to get that lost torque back. these cars need some back pressure if there is gonna be really poor acceleration until like 3grand if its all gone. I know this wasnt the answer u r looking for........sorry guys....

BTW eric.......when u bought ur flowmaster u bought it designed for ur car right?? how did it fit up to the stock set up?? What did u have to weld and would u have a part # for it? Thanx man, i just wanted to get the 80 series to give me a nice rumble.

 

Exhaust manifolds work as well as they do for off-idle torque because they use the "expansion" principle. The hot gas comes charging out of the port and sees a wide open common chamber to spread out in. That acutally works better at low speeds than headers. As the RPMs increase though, the lack of direction causes a lot of turbulence and the stock manifold becomes a hinderance.

With headers, the exhaust slug has to push the long column of gas in the header tube out of the way as it comes out. At higher RPMs, the header pipe can take advantage of the inertia of the moving column of gas to scavenge the rest out and "pull" the intake charge into the cylinder. There is an RPM range at which the pipe "resonates" and that is where headers shine.

With the ECM, you'll very likely have to get an aftermarket ECM chip that's designed to accomodate all that non-stock stuff.

 

Onefine89, what other mods do you suggest tht might help with torque?
This is ongoing for me,I am trying to make mods that I can later use on a 350TBI.
Thanks....bob

 

if you want your torque back, get the Hooker Cat-back. i have a big increase in low-end torque. before i had a 2 1/4" glasspack the dumped before the rear axle. now i went to the 3" Hooker Cat-back and i have increased my low end torque. hope this helps.

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RED82TA5.7L

1982 Pontiac Trans Am
Cross-Fire Injected 5.7l V8
Eldebrock Headers, 3" Hooker Cat-Back, 2 nice tips with duel outlet on each side.
Mods: 1.6 Proform Roller Rockers, electric fan.

Future mods: X-Ram( Aftermarket Cross-Fire Injection Manifold that proves to have as much power as TPI www.x-ram.com )
Cross-Fire Injection after market chip that says that it will proform like 90's injections.. http://www.turbocity.com/CorvetteCro...ECMUpgrade.htm

 

rsilver, well u did alot of the cheap/free mods other than ignition. A good ignition will deffinetly improve low end and throttle responce. In this case u almost should have went 3.73 for ur car. The only reason being is that it will make u rev quicker where the headers will really come into play. But for now i would look into an ignition, haveing ur TBI modified or just go with a smaller outlet muffler. That could possibly bring back pressure w out having to mess with the headers or n e thing.

 

lol one big thing i forgot was cam. O good high lift cam will definetly inprove torque. ALOT!

 

I have the same problem when I leave the plate open(borla )

 

For what its worth....isn't the Hypertech Stage II chip designed for cars with modded exhausts? Has anyone out there used this setup with any differences in torque?

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92 Camaro RS LO3, 5-spd, T-tops
Mechanics:
Open Air Element w/K&N Filter, Flowmaster 3" Cat-back Exhaust, Z28 Grille w/aftmkt fog lamps
Electronics:
Alpine 8030 Alarm System, Valentine One Radar Detector (How did I ever drive without one?), Pioneer DEH 7450 Head Unit w/6-pack CD changer, Pioneer DEQ 7600 Sound Processor, 2 Kenwood KAC-90 Amps powering 2 12" Pro Red subs and 4 Infiniti speakers.
NEXT UP: SLP 1 3/4" Headers/Y-pipe, Centerforce Dual Friction Clutch kit

 

Sounds like a higher stall torque converter should be next. My engine was designed to run with a supercharger, but sometimes, I run it without. Can you imagine the torque loss on my 305 with

large tube runners,
TPIS Big Mouth base,
ported/polished Corvette heads,
Crane 2032 with 1.6 rockers (482/496 lift, 214, 220 dur @ 50),
SLP 1-3/4" headers, and
dual cats. Most if not all these parts should be for a 350, not a 305.

My Vigilante raises my rpm's at low vehicle speed more than enough to compensate for any loss of torque.

------------------
Willie

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
12.57 @ 111 mph.
12.04 @ 114 mph (50-hp nitrous).
http://members.optushome.com/au/downunder1/rides/willie/willie.html

1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.

 

Hey Mike, I put the Flowmaster 80 Series on my car when I put the 3" custom exaust on. Sorry. I don't think u could put a 80 Series on a stock exaust since the inlet is 3".

So u think if I added some sort of catylitic hi-flow converter on then I would gain some torque back? Cause right now I don't have any cat, just a 3" pipe from the headers to the muffler.

------------------
Eric Natzke
91 Firebird 305 TBI (ZZ4 summer of "01")
ASCD Ram Air Hood-3" custom exaust-Flowmaster 80 Series-No Cat-Edelbrock TES Headers (coated)-March Pulleys-TBI Spacer-K&N Open ELement-TransGo Shift Kit-B&M Supercooler 28,000 GVW-Hypertech Thermomaster-160 Stat-3:42 GM Gears-Auburn Posi Unit-Edlebrock Strut Tower Brace-MSD Superconducters-Accel Cap & Rotor-MSD Blaster Coil-Rapidfire Plugs-265/50/R15 Tires-Emmison's all Gone
http://members.aol.com/j007golden/91firebird.html

 

You need to restrict your flow a little or get a cam with less overlap.

------------------
1985 Camaro IROC-Z LB9

1989 Pontiac Firebird
Formula W6S LO3 TBI 305
-180 degree stat
-Hooker Cat-Back

 

i noticed a big difference in low end power with the converter in place as compared to open y-pipe. but the open exhaust deffinately pulls better in the high rpms.
a happy medium that i have found is a straight pipe instead of a cat.
if you want to be real sneaky, weld a pipe through a hollowed cat.

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88 CAMARO RS
87 IROC-Z DRIVETRAIN
305 TPI, 700R4, 3.73s
ported plenum, performance resource chip,edelbrock TES Headers and cat-back, K&Ns, AFPR, rest is stock.
15.0 @ 92.5 (bald tires)

 

Back pressure DOES NOT create low end torque. Relatively small exhaust pipes result in high gas velocity. Back pressure is a product of, or side affect of small pipes, and has nothing to do with creating low end torque. The high velocity gases have momentum, which helps to evacuate the cylinders of the engine at low engine speeds. At lower engine speeds, your larger exhaust system, with lower gas speeds, is no longer evacuating the cylinders, and pulling fresh charge through the intake system, compared to the factory exhaust system. The OEM TBI was not calibrated to operate with a free flowing exhaust system. I recommend you install an aftermarket computer chip, compatible with the modifications you have made.

I have run Hypertech, and would not recommend it because in my application, I have the ignition timing retarded 5 degrees from the factory setting and the engine still pings under load with 92 octane unleaded. I have heard a lot of praise from the users of the Fastchip (www.fastchip.com) Their standard chip for your car is $159. If you feel you need something other than their standard chip, they can burn a custom chip for your combination for more money.

 

Yeah, I have a hypertech right now and my car pings too with 92 octane. I want to get a fastchip and sell the hypertech. With my mods, u think it would be better to have a custom one made or just the fast chip for my car?

------------------
Eric Natzke
91 Firebird 305 TBI (ZZ4 summer of "01")
ASCD Ram Air Hood-3" custom exaust-Flowmaster 80 Series-No Cat-Edelbrock TES Headers (coated)-March Pulleys-TBI Spacer-K&N Open ELement-TransGo Shift Kit-B&M Supercooler 28,000 GVW-Hypertech Thermomaster-160 Stat-3:42 GM Gears-Auburn Posi Unit-Edlebrock Strut Tower Brace-MSD Superconducters-Accel Cap & Rotor-MSD Blaster Coil-Rapidfire Plugs-265/50/R15 Tires-Emmison's all Gone
http://members.aol.com/j007golden/91firebird.html

 

Eric:

I don't have much experience with computer chips, but I would think the generic chip would suit your limited mods application just fine. I imagine when you get into aftermarket cams, heads, intake, etc, a custom chip may be required.

I e-mailed fastchip a few months ago and inquired how they determine the chip programming for a given application. They have a chassis dyno with a wide-band oxygen sensor that they use to maximize HP and torque output while adjusting the fuel and timing curves. Obriously, finding someone with this type of equipment, who is compitent and reputable, would be the way to go. It would probably also cost 4 or 5 times that of a generic chip.

 

There is a Howell custom chip company here in Michigan. I will probably give them a call.

------------------
Eric Natzke
91 Firebird 305 TBI (ZZ4 summer of "01")
ASCD Ram Air Hood-3" custom exaust-Flowmaster 80 Series-No Cat-Edelbrock TES Headers (coated)-March Pulleys-TBI Spacer-K&N Open ELement-TransGo Shift Kit-B&M Supercooler 28,000 GVW-Hypertech Thermomaster-160 Stat-3:42 GM Gears-Auburn Posi Unit-Edlebrock Strut Tower Brace-MSD Superconducters-Accel Cap & Rotor-MSD Blaster Coil-Rapidfire Plugs-265/50/R15 Tires-Emmison's all Gone
http://members.aol.com/j007golden/91firebird.html

 

Thanks to all for your comments. I bumped timing up in 2 degree increments and then did quarter mile runs with a stop watch. Not real accurate but increasing from 4degrees to 10 degrees only made 1 MPH and .1 second. I could tell no difference SOP. BUT, I finally got off my *** and made the adjustable fuel pressure mod to the TBI shown on this site. I don't have a guage so i don't know what the fuel pressure was at or how much i increased it, but at most it was a full turn of the screw.
Anyway, that made a BIG SOP difference on the low end. The engine even sounds better to me . I will get out under same conditions
and see if it makes any difference with the stop watch or if it my imagination.Gonna hook up my friends scan tool this weekend and see where i am at on the o2 voltage and dial it in.
You all gave me some very good advice and I really appreciate it.....bob

------------------
91 camaro RS L03 convert,
t-5, ultimate TBI mods,TBI spacer,SLP 1 5/8 headers,
3"cat back, 3.42 torsen posi,alston SFC's,Global West LCA relocation brackets

 

Duh...rsilver hit the nail right on the head. It didn't even occur to me until I read about increasing fuel pressure, that I remembered something: exhaust mods will make your car run lean. The engine can move more air out of the cylinders, and therefore can put more air into the cylinders. More air means you need more fuel or you'll run lean. A little bit lean hurts power; a lot lean causes detonation and melted pistons. In fact, it's standard procedure on carbed engines to make the engine run richer when you put headers on. So, I bet if you bump the fuel pressure up some, you'll get all your nice low-end back.

------------------
Jon
------------------
1988 Trans-Am GTA w/ L98, Futura GSX tires, and a rusted-out no-name cat-back
------------------
Mods: TB coolant bypass...more on the way!

 

A lot of the "big boys" strategically place kinks throughout their exhaust(headers mostly) to pick up lost torque. I know most of us (prolly all of us) can't go out and by 10-20 sets of headers to do these tests>>>>>>but it's something to think about. Also>>>>>>as said>>>>>adjust that fuel pressure man.......it's a good start to where you want to go.

------------------
Alex (AKA chevyboy) '91 RS 327 stroker, trans-go shift kit>> manual valve body, cat-delete, MSD (ignition, coil, 2-step, timing retard/ advance),Flowmaster, complete Edelbrock suspension including shocks, struts and lowering springs. CRAGAR drag wheels. Lowered 2.25" in front and 1.5" in rear....Best E/T 12.84 @109 mph...(got spray?)plus more!!

 

Well, just a little update on this. The flowmaster behind the 3" exhaust is a little loud for a daily driver, at least for me, so I looked into a number of other mufflers with 3" inlets and dual 2.5 outlets. Most of the manufactures I talked to were honest and
said they didn't think theirs were any quieter than flowmaster. So, I spent $30 and got a 3" straight through resonator to maybe quiet things down a bit. I noticed very little difference in sound, but MAN did I get some big time torque back. This thing seems to be getting dialed in cause now I have great off idle torque to 3,000 and it pulls hard to about 4800-5000. Very drivable.
There sure is a lot to exhaust tuning, thats for sure!!I wish someone would come up with a 3" tube you could install with a variety of baffels so you could really tune the exhaust. ( I know borala has them for their system)......bob

------------------
91 camaro RS L03 convert,
t-5, ultimate TBI mods,TBI spacer,SLP 1 5/8 headers,
3"cat back, 3.42 torsen posi,alston SFC's,Global West LCA relocation brackets

 

Hey Bob, where did u get that for ur exaust? The resinator? What the heck is it and how do u install it? I have a custom 3" exaust system, edelbrock TES headers and a Flowmaster 80 Series (3" inlet, 2.5" outlet)

------------------
Eric Natzke
91 Firebird 305 TBI (ZZ5 summer of "01")
ASCD Ram Air Hood-3" custom exaust-Flowmaster 80 Series-No Cat-Edelbrock TES Headers (coated)-March Pulleys-TBI Spacer-K&N Open ELement-TransGo Shift Kit-B&M Supercooler 28,000 GVW-Hypertech Thermomaster-160 Stat-3:42 GM Gears-Auburn Posi Unit-Edlebrock Strut Tower Brace-MSD Superconducters-MSD Cap & Rotor-MSD Blaster Coil-Rapidfire Plugs-265/50/R15 Tires-Emmison's all Gone
http://members.aol.com/j007golden/91firebird.html
For info on certain parts or mods go to the site below
http://members.aol.com/j007golden/modeval.html

 

91bird, it looks like a small muffler but its a straight through tube with slashes or a type of a baffle inside which puts in a very mild restriction. It about 12 14 inches long
and you install it in a straight section of pipe behind the cat before you get to the muffler. If you don;t like it you can cut it out and just weld a 3' pipe back in its place.I believe most performance muffler shops have them and they also make a similar thing called a resonator tip but the ones I saw were really ugly. The tech at flowmaster suggested I try this and said most muffler shops have resonators. I have heard that some guys just put in a cheap glass pack muffler to accomplish the same thing.
Let me know how you make out if you do it ..........bob

------------------
91 camaro RS L03 convert,
t-5, ultimate TBI mods,TBI spacer,SLP 1 5/8 headers,
3"cat back, 3.42 torsen posi,alston SFC's,Global West LCA relocation brackets

 

what is "back pressure" a new seat thingy??
the only thing that i know of with engines(or any air pump) is something called "port velocity"

maybe i'm wrong.
i have a full exhaust on my camaro. and can tell a huge diffrence from stock. check your plugs, and make sure the car is in tune. also maybe try some of the free/cheap mods

HTH,
RS

------------------
(A.K.A FireBird88)
AOL SN: Zander0710
1992 Camaro RS 25th anniversary edition Adopted Feb,14 2000

Mods:
14x3 Open element w/ K&N filter, MSD 6a, MSD GM blaster Coil ,MSD 8.5 SC wires, AFPR,Fuel Pressure gauge(60Psi max), 3-Row Al rad. , 180* t-stat, Hooker 1 5/8 headers, 3" Catco cat, 3" Hooker Aero Chamber cat-back, "Ultimate TBI" mods

[This message has been edited by UnderDogRS (edited December 05, 2000).]

 

well, the only thing i can say is to do a full overhaul on your motor just check/replace minor things-spark plugs, injectors,and so on . your car might not be running to its full potential

 

All my plugs are fine and brand new, along with the wires and cap & rotor. I don't think I have a problem getting air in the intake from all the stuff I have done. I think I just need to add a resinator like RSsilver did. To much exaust for my 305 I think. Needs a little bit of restriction.

------------------
Eric Natzke
91 Firebird 305 TBI (ZZ5 summer of "01")
ASCD Ram Air Hood-3" custom exaust-Flowmaster 80 Series-No Cat-Edelbrock TES Headers (coated)-March Pulleys-TBI Spacer-K&N Open ELement-TransGo Shift Kit-B&M Supercooler 28,000 GVW-Hypertech Thermomaster-160 Stat-3:42 GM Gears-Auburn Posi Unit-Edlebrock Strut Tower Brace-MSD Superconducters-MSD Cap & Rotor-MSD Blaster Coil-Rapidfire Plugs-265/50/R15 Tires-Emmison's all Gone
http://members.aol.com/j007golden/91firebird.html
For info on certain parts or mods go to the site below
http://members.aol.com/j007golden/modeval.html

 

My stuff is fine too. But the combination of increasing fuel pressure ( 900mv at WOT on the o2 sensor measured with scan tool)and the resonator made a big difference.The fuel pressure adjustment helped but for my POS LO3 it was the resonator that made the biggest difference. Anyway, I am done till I either add heads and a cam to my LO3 or bite the bullit and go for a 350. Still trying to decide. Thanks again for all the help......bob


------------------
91 camaro RS L03 convert,
t-5, ultimate TBI mods,TBI spacer,SLP 1 5/8 headers,
3"cat back, 3.42 torsen posi,alston SFC's,Global West LCA relocation brackets

 

Yeah, I have my AFPR at home, need to put it in and set it. Heard it does great things for moddified LO3's.

I don't know about u, but I am biting the LO3 build and going 350.

------------------
Eric Natzke
91 Firebird 305 TBI (ZZ5 summer of "01")
ASCD Ram Air Hood-3" custom exaust-Flowmaster 80 Series-No Cat-Edelbrock TES Headers (coated)-March Pulleys-TBI Spacer-K&N Open ELement-TransGo Shift Kit-B&M Supercooler 28,000 GVW-Hypertech Thermomaster-160 Stat-3:42 GM Gears-Auburn Posi Unit-Edlebrock Strut Tower Brace-MSD Superconducters-MSD Cap & Rotor-MSD Blaster Coil-Rapidfire Plugs-265/50/R15 Tires-Emmison's all Gone
http://members.aol.com/j007golden/91firebird.html
For info on certain parts or mods go to the site below
http://members.aol.com/j007golden/modeval.html

 

So are you guys saying with headers, 3" Dynomax cat, and a 3" Flowmaster cat-back, I will lose low end power? How about using that setup with a stock cat though? Thanks.