Home / Toyota Supra Forums

Go Back   Toyota Supra Forums! Join the Supra forum! > Performance, Modification, and Maintenance Forums - for generation specific discussions > MKIII Supra

Reply
 
Thread Tools Display Modes
Old 11-22-2010, 06:47 AM   #1
btwilson86
Super Moderator
 
btwilson86's Avatar
 
Join Date: May 2007
Location: Billings, Montana
Posts: 1,034
btwilson86 is on a distinguished road
Default

Well, I wouldn't really be able to say for sure; never drove anything with a high-flow cat on it. Exhaust systems are tricky, too much free flow and you don't build the pressure differences between outside air and the gases within the pipes that is required to help suck the exhaust out of the system, too little flow and exhaust backs up in the pipes and chokes the engine. Both scenarios will hinder performance.

I feel it should be noted that it's not about how much hp you can gain, but how the car drives. That extra 2 hp at XXXX rpm for a split second could translate to less hp throughout the powerband. In this scenario, you have more peak hp but performance will suffer due to the lower overall hp.

Oh, I also forgot to mention that the Supra I was referring to above had an unknown brand 2 1/2" cat-back system on it, both before and after the cat change.
__________________
1989 7MGTE R154 Targa Top White Package w/Blue Interior
Driftmotion 57trim CT26, Upgraded Intercooler, 2.25" Hard Pipes, 3" Turbo Back Exhaust with Test Pipe, HKS VPC w/GM 3 bar MAP sensor, APEXi S-AFC, Walbro 255lph fuel pump, ProSport EVO Series Boost / Fuel Pressure / AFR gauges, Lotek a Pillar Gauge Pod, HKS Type 0 Turbo Timer, Eibach Lowering Springs, Tokico Illumina II TEMS struts, custom powder coated Motegi Racing TrakLite wheels
btwilson86 is offline   Reply With Quote
Old 11-22-2010, 06:59 AM   #2
Supra Saiyan
3" Exhaust
 
Supra Saiyan's Avatar
 
Join Date: Feb 2010
Location: Oregon
Posts: 225
Supra Saiyan is on a distinguished road
Default

Quote:
Originally Posted by btwilson86 View Post
Well, I wouldn't really be able to say for sure; never drove anything with a high-flow cat on it. Exhaust systems are tricky, too much free flow and you don't build the pressure differences between outside air and the gases within the pipes that is required to help suck the exhaust out of the system, too little flow and exhaust backs up in the pipes and chokes the engine. Both scenarios will hinder performance.

I feel it should be noted that it's not about how much hp you can gain, but how the car drives. That extra 2 hp at XXXX rpm for a split second could translate to less hp throughout the powerband. In this scenario, you have more peak hp but performance will suffer due to the lower overall hp.

Oh, I also forgot to mention that the Supra I was referring to above had an unknown brand 2 1/2" cat-back system on it, both before and after the cat change.
Hmm, I see..
Supra Saiyan is offline   Reply With Quote
Old 11-22-2010, 07:02 AM   #3
Supra Saiyan
3" Exhaust
 
Supra Saiyan's Avatar
 
Join Date: Feb 2010
Location: Oregon
Posts: 225
Supra Saiyan is on a distinguished road
Default

Thanks for all your input.. I have decided the only way to find out if I will in fact lose or gain will come down to trying the high flow cat and the test pipe on a dyno. This way I can see where I gain or lose along the power band...
Supra Saiyan is offline   Reply With Quote
Old 11-22-2010, 07:29 AM   #4
btwilson86
Super Moderator
 
btwilson86's Avatar
 
Join Date: May 2007
Location: Billings, Montana
Posts: 1,034
btwilson86 is on a distinguished road
Default

That's a good idea, be sure to post your results once you're able to do this
__________________
1989 7MGTE R154 Targa Top White Package w/Blue Interior
Driftmotion 57trim CT26, Upgraded Intercooler, 2.25" Hard Pipes, 3" Turbo Back Exhaust with Test Pipe, HKS VPC w/GM 3 bar MAP sensor, APEXi S-AFC, Walbro 255lph fuel pump, ProSport EVO Series Boost / Fuel Pressure / AFR gauges, Lotek a Pillar Gauge Pod, HKS Type 0 Turbo Timer, Eibach Lowering Springs, Tokico Illumina II TEMS struts, custom powder coated Motegi Racing TrakLite wheels
btwilson86 is offline   Reply With Quote
Old 11-22-2010, 01:52 PM   #5
fantasma87
3" Exhaust
 
fantasma87's Avatar
 
Join Date: Oct 2010
Location: kansas
Posts: 166
fantasma87 is on a distinguished road
Default

nice topic, i`m interested now because my fantasma doesn`t have the cat and its a straight 3" pipe from the downpipe to the muffler. i will run 550cc injectors and some mods on it "7mgte". post the results to see the diferences. thanks
__________________
Nice 87 Supra, Pearl white, targa top, 5 spd, 7mgte

ARMY STRONG !!

La fiebre Boricua Puerto Rico!!!
fantasma87 is offline   Reply With Quote
Old 11-26-2010, 03:27 PM   #6
Supra_Freak_7m
Intake
 
Supra_Freak_7m's Avatar
 
Join Date: Apr 2010
Location: Montana
Posts: 40
Supra_Freak_7m is on a distinguished road
Default

Do keep in mind that the changing of the cat will only heavily influences N/A's on powerband issue. With a Turbo, all of the back pressure required by the car is supplied by the turbo, no further back pressure is needed.

So, If you got a turbo, sure, you can take the cat off and see a considerable gain.

With an N/A, I wouldnt, the car runs alot smoother with it on and it smells better.

One more thing to keep in mind, the oxygen sensor on this car is not heated, I have been to told by mechanics that beack pressure created by the cat helps to heat up the oxygen sensor, and that little guy controls up to about 8% of your fuel economy...
__________________
1987 Toyota Supra 7MGTE AUTO
1987 Toyota Supra 7MGE MANUAL
1990 Toyota Supra 7MGTE AUTO-> MANUAL
Supra_Freak_7m is offline   Reply With Quote
Old 11-26-2010, 05:10 PM   #7
Supra Saiyan
3" Exhaust
 
Supra Saiyan's Avatar
 
Join Date: Feb 2010
Location: Oregon
Posts: 225
Supra Saiyan is on a distinguished road
Question

Quote:
Originally Posted by Supra_Freak_7m View Post
Do keep in mind that the changing of the cat will only heavily influences N/A's on powerband issue. With a Turbo, all of the back pressure required by the car is supplied by the turbo, no further back pressure is needed.

So, If you got a turbo, sure, you can take the cat off and see a considerable gain.

With an N/A, I wouldnt, the car runs alot smoother with it on and it smells better.

One more thing to keep in mind, the oxygen sensor on this car is not heated, I have been to told by mechanics that beack pressure created by the cat helps to heat up the oxygen sensor, and that little guy controls up to about 8% of your fuel economy...
F' it all.. I'm either hollowing the cat or doing the test pipe.. Anyone know what kind of noise a hollow cat will make? something nasty added to my 3'' system? or will it not sound bad?
Supra Saiyan is offline   Reply With Quote
Old 11-22-2010, 02:53 PM   #8
Ranma
12psi boost
 
Ranma's Avatar
 
Join Date: Jun 2010
Location: Claremore, OK
Posts: 326
Blog Entries: 10
Ranma is an unknown quantity at this point
Talking

I took my Supra without cat for a run down the mother road on Saturday. Had the top off and the engine sounds get annoying real quick. I do not think he has any more power than my Supra with the CAT. If anything there seems to be less power. Well put enough money into her, suppose it is time to replace the exhaust system or at least from the block to the cat.
__________________
1986 Mk III MA70 7MGE Targa Top 5 Speed Stock Exhaust
Ranma is offline   Reply With Quote
Old 11-22-2010, 06:46 PM   #9
fantasma87
3" Exhaust
 
fantasma87's Avatar
 
Join Date: Oct 2010
Location: kansas
Posts: 166
fantasma87 is on a distinguished road
Default

so you feel more power with the cat?
__________________
Nice 87 Supra, Pearl white, targa top, 5 spd, 7mgte

ARMY STRONG !!

La fiebre Boricua Puerto Rico!!!
fantasma87 is offline   Reply With Quote
Old 11-22-2010, 07:47 PM   #10
Ranma
12psi boost
 
Ranma's Avatar
 
Join Date: Jun 2010
Location: Claremore, OK
Posts: 326
Blog Entries: 10
Ranma is an unknown quantity at this point
Talking

Quote:
Originally Posted by fantasma87 View Post
so you feel more power with the cat?
I would have to do a series of objective tests. I do hope to get transferred to Hawaii or return home to Japan. The Cat is needed for both, do wonder if I can get in trouble for running without the cat.
__________________
1986 Mk III MA70 7MGE Targa Top 5 Speed Stock Exhaust
Ranma is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Average HP Gains (?30HP?) Supra Saiyan MKIII Supra 18 08-12-2010 03:00 AM
ABS delete jdmsoup MKIII Supra 8 06-22-2010 03:19 AM
Heater Delete joshtexican MKIII Supra 9 06-20-2010 05:15 PM
ABS delete matt1993supraTT MKIV FAQ 13 06-06-2010 05:23 PM
3" exhaust/2.5" wit not cats Hp Gains? supraman121 MKIII Supra 0 08-20-2007 06:09 AM


All times are GMT. The time now is 09:06 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.

1986



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87