A bit about me (not for my ego, but for your open mindedness and ponderance of the info I will give from time to time). I am an ASE Certified Master Auto Tech for 20 years. (No, I don't know everything, and I DO enjoy learning something every day). I manage a very successful smog repair and performance shop here in the Mojave Desert of California. (Heavy pollution control laws here!!)

For a decade I was (retired now) a repair analyst and technical training instructor on the American Space Shuttle program. When I am interested in something, I analyze the hell out of it before I do anything or spend $$$ on it.

Now, with the internet so handy, I do even MORE research to get the MOST performance from my cars. I get alot of info from other enthusiasts, and race performance magazines, too.

I have built, tuned, and raced cars, carts, and motorcycles.
I am living on a performance budget, too, like most MKIII owners.

SO.......First Supra performance mod.....Exhaust Systems....

I read on this forum recently (like 2005)that a 3" (75mm) exhaust is the way to go. My experience indicates that is only true for the turbo motor....
Wide open breathing....
Quicker spoolup of the turbo....
Higher RPMs.

But...for a naturally aspirated motor, (and NOT a track only car running high rpms all the time), you want 'some' back pressure to give you more torque at the lower RPM's. (You know, 0 to 60 MPH, daily driving).

And remember, these cars are very heavy (mine is 3600 lbs).

Much research led me to run a 2.5" (62mm) pipe from the Cat Converter all the way out.

I went with a Magnaflow straight thru muffler (packing inside). It was "too" loud for me. It is at the end of the pipe, and it created an awful drony, deep tone at cruising of 2k RPMs. I could not even listen to the stereo.

So...I ADDED a 24" long straight thru glass packed muffler, same 2.5" inside dia., and 4" diameter outside, in the middle of the system (middle of car).

Now it has a GREAT sound, with an UNRESTRICTED flow, and just enough back pressure to keep my torque high at lower RPMs.

Before this exhaust mod, the car would max out at 125mph.

After this mod, I can easily go 145mph any time I want.

actually 2.5 with a glass pack is still considered overkill(too free flowing). 2.25 with a single chamber no cat is equivalent to what you used. to gain the best compremise of torque; its a header without cat straight back 2.25in pipe with a 2 chamber or equivalent muffler. if you want a clean crisp sound, try a flowmaster delta series. if you want a deep sound, go with a MAC muffler. :D

Here in Calif. we must have a cat converter to be street legal. That is why I went with the 2.5" pipe, the cat causes some restriction. Even without a cat, I'd still run 2.5".

well... yeah thats true 3" down pipe for the turbo. thats true. n me thats what i were having on my mk2 right now. i got a 5mgte singo turbo n just about to upgrade my turbo into t4 turbo. now i were using 3" down pipe without converter. straight pipe 3" from the turbo elbem all the way to the 3" exhaust to. but i were using this one thing it call something like a flare or something like that tho. and i were using a silencer on my exhaust to. n it sounds like a stock muffler now. its not loud at all. well let me know how you setup on your mk3 alright.

awesome info there mrnickleye... when you've got some luvly research like this post it in the faq's ;)

i may have neglected to mention that 3" was not suitable for na LOL.. oops.. i guess i automatically assume everyone's is turbo.. my bad haha

moved to faq's :D

i hit FULL boost @ 2700 ish rpm (i get boost before that mark but not full until around there)

2.75 elbow
http://www.alamomotorsports.com/AMS/ams_suprao2.html
3" downpipe
http://www.alamomotorsports.com/AMS/amsex.htm

"F" the cat !
i use a striaght through 2.5 ish custom (there's your back pressure) hehehe

3" exhaust
http://www.alamomotorsports.com/prodndxman.html#Blitz
mostly using a silencer on the end of it


it sounds nice and tuned as i pull away or so i've been told .
just my 2 cents on the subject

Your thoughts aren't worth more then two cents? :D

lol thats funny
Hey Diamond you ever go to the NESupra group on yahoo ?

there reason i ask ...
Request to join NEsupras denied
Hello,

Your request to join the NEsupras group was not approved.
The moderator of each Yahoo! group chooses whether to restrict
membership in the group. Moderators who choose to restrict
membership also choose whom to admit.

Please note that this decision is final and that Yahoo! Groups
does not control group membership.

DENIED

Mine was also denied , thats why i'm started my own group and club for new jersey supra owners. I still decide wether people get to join or not, i'm just not such a dick about it.

Mine has a stock pipe on. I was thinking about putting a 3.5" on, is this too big?

if its a non turbo, yes.

Hey Monki, or anyone that can answer this, is there such a thing as an exhaust being too big for a turbo?

i think the bigger the exhaust for a turbo to breath is fine but dont go all out like a freaking deisel truck, i deleted one cat ran 2 1/2 back to the diff then went 3 inch and it has a nice throaty sound unlike thoses damn crx's and stuff that sound like pissed of bee's...lol....plus who can hear my turbo at idle from the exhaust....its kool....lol

if its a non turbo, yes. [/b][/quote]
Yea she's a twin turbo, check my signature, so is a 3.5" alright?

Well from i can gather by what he said up there a 3.5 would be fine.

Yea she's a twin turbo, check my signature, so is a 3.5" alright? [/b][/quote]
i'd consider a 4". if you start hitting really high hp(750+), you'll need it. there was once guy running a single 4in split into 2 3.5in. and it fit, tucked under a sc300.

"it has a nice throaty sound unlike thoses damn crx's and stuff that sound like pissed of bee's"




AMEN

-------------------------------------------------------------------------------------------

Domestics FEAR ME

"it has a nice throaty sound unlike thoses damn crx's and stuff that sound like pissed of bee's"

even more important "those damn crx's"


AMEN

-------------------------------------------------------------------------------------------

Domestics FEAR ME

so since everybody is saying that a 3" is too big for a N/A, would it even matter if i put a high flow 3" cat in my 2 1-2" exhaust? is it worth it?

and what about the research info done on the cold air? tell me......

Well...I manage a smog test & repair shop here in CA. The high flow cat, like Magnflows (the brand of cats we use) will get you thru smog at least once. The specs are higher on our MKIIIs than newer cars. The high flow cats are just that, and many times the openess does not allow the cat to get hot enough to do its job.

I installed the 2 1/2" cat and piping all the way back. It seems to work fine. I am only 225 hp, though. My smog #s are very good.

Be sure to get a new O2 every few years. Cheap insurance for better fuel mixture ratio.

As for cold air intake, I've read lots on the net, magazines, and forums. With the AFM like our n/a has, you'll end up putting a K&N (or similar) either directly onto the AFM (mine), or on the 3" pipe you'll use to run out front somewhere (behind the headlight?).

I ducted air with galvanized sheet metal up from the front grill to the opening for original airbox, behind headlight.

Then I made a plastic box to seal off the heat from under the hood from getting into the K&N.

You DO NOT want hot air going into the air cleaner, it cause HP loss !!!

cool thanks for the info

I have a question, does anyone have a before/after dyno sheet pic of a stock N/A before and after mods? I was thinking about buying a header and getting the whole exhasut done, but i dont want the car to be loud so I duno if its worth the HP gains/noise

could someone point me in the direction of an exhaust that is quiet but doesnt restrict power too much. i would really like one that doesnt have any sound (as close to that as you can get). oh...i have an 86.5 N/A.

Put a 24 inch glass pack inline, And get a factory muffler from any car at an autoparts place. There like 25$ each.

what elese could i use to make a heat shield other than a plastic box?

You could use sheet metal, but it does not insulate as well as plastic.
By box, I meant I boxed it in. I actually used a household trash can. I cut 2 pieces out of it, one for the top, and one for the side that is toward the radiator.

The bottom is already there, as is the fender side.
The back is best left open, as the AFM blocks enough off, and you need it open in the back to allow the outside air to flow better over the filter.

great info nick. i to live in CA and deal with smoging. I'd like to clean up the intake like you have, but what about changing the original equip. when it comes time to smog? What does the state require?

Ca. smog testing
 

You must have the original equipment in place and working properly. Aftermarket stuff must be C.A.R.B. legal.

-Cat convertor
-EGR system
-Timing set to spec
-No check light on (except when they test for a good bulb)
-Evaporation canister & system
-Vacuum lines in place and routed properly
-No BIG holes in the exhaust or muffler
-No fuel leaks
-No BIG liquid leaks (oils, coolant, etc)
-No obvious signs of tampering (like disconnected stuff)
-Good gas cap (new ones cost $6)


Also, make sure its running good, and won't overheat during the test. Make sure the brakes work.

Of these mods, what is legal in CA? I really don't want to pay $50. or so for a stock rubber intake hose to replace the damaged on I have, if I can install a better flowing intake pipe from my air-box.

Well....the smog tech will want to 'see' the AFM under the hood. He's not gonna care if you use K7N type filter, or PCV or metal or whatever piping from AFM to the throttlebody. Just so its connected tight, with no air leaks.

Some people have used those 3" metal piping kits from internet or Pepboys, or custom, etc. But I don't because it sits right over the exhaust manifold and the metal will get very hot, which heats the intake air.

As for the $50 hose off the throttlebody, I later saw some 3" rubber, and PCV elbow pieces at Home Depot & Lowe's that would have worked. $10-15.

What is AFM? Great idea about the pvc and rubber hose. I'll take it one step further and wrap the pipe with insulation to help control intake temp and protect the piping. What do you think?

The AFM (Air Flow Meter). The metal and plastic electronic component that the air filter is mounted to. Near the power steering reseviour.

Insulation wrapping is good if you remove the original equipment and use other piping materials. There is some you can buy from internet performance stores just for this purpose. Looks good too.

were you at
 

wasnt quasimodo already white..... haha just noticed your name, and yes mr nickeleye thanks for all your input on this forum, it helps, but i do have a question about exhausts, what is the horsepower difference between cat backs and with headers etc.. im a noob, and would love to know as much about these things as i can, not only horsepower difference but maybe why someone would add headers and full exhaust over cat back, also an average price difference, if anyone knows please share, thanks.

Well, it is estimated that going cat back , and larger pipe (2 1/2" in our N/A's), will get you about 5-10 hp.

In alot of cars, it is estimated that putting headers on will get you about a 10% gain. But that because those cars had restricted exhaust manifolds.

The N/A motors have a nice, free flowing, and light-weight manifold from the factory. Toyota spent a lot of time and $$$ developing that manifold to give you the best "bottom-end" torque, with out a big loss on the top-end.

I still have my factory one on. I drive it every day, city mostly.

As you read in the first post, "Before this exhaust mod, the car would max out at 125mph.

After this mod, I can easily go 145mph any time I want."""""

Some of the other folks here may be able to tell you about their experiences with headers, and what gains they have gottn,

thank you very much for your input, helps me understand a lil better, but is cat back basically everything is stock except the cat converter and everything behind it, cause that's what it sounds like haha, and are headers and downpipes the other exhaust upgrades you can get, or are there additional? thanks for any input guys. im being thorough cause im getting ready to do it in a few weeks

Cat back does not mean replacing the cat. It means...from the cat ...back.

No 'down pipe' on a N/A car, only turbos.

Headers for our cars go way back, to a pipe, then the cat.

There are performance cats, but not needed unless you are building a 300hp + car.

thanks nickeleye, i now know what i need to get, now the only other question i have is sound.... i do not want a large sound so that every one looks at me like im a loser, or a ricer sound, i'll probably youtube some exhaust sounds soon, but any suggestions would be nice as well guys. Maybe even something like yours mentioned earlier nickleye.