Increasing backpressure? - Toyota Yaris Forums

PHXDEMON · 08-21-2009, 11:47 PM

I recently installed the nitto midpipe on my car along with the stock header and a tanabe madallion axleback. It feels like I dropped a lot of torque from 2-4k RPM and I usually don't rev higher than 4k

Is there an easy mod I can do to temporarily inscrease some backpressure to regain some of that torque until I am boosted? Also for those of you who have the midpipe are you getting 100% success on getting rid of a CEL with that anti fouler deal the garm sells on his website?

AdeJong 03 · 08-22-2009, 03:59 AM

what is the diameter on your exhaust?

i believe the general rule of thumb is 2'' up to 120 hp, 2.25" up to 180hp, 2.5'' up to 250hp, 3'' up to 300-350ish, and 4.5'' for anything beyond

please dont quote me on this. its just general hearsay from my years around other forums.

Reddog99 · 08-22-2009, 11:01 AM

If you don't usually rev above 4k, then exhaust modifications are the wrong thing to do. Over the years, I have installed various exhaust modifications on vehicles I've owned and without exception, every one that reduced back pressure (on a stock engine) also reduced mid-range torque, sometimes by a substantial amount.

Most of these systems increased power in the upper RPM range, but for most street driving, that's pretty useless. If you have a big motor with lots of torque, it probably won't matter. But on a little engine like the Yaris has, a mid-range torque hit can be very noticeable.

cali yaris · 08-22-2009, 11:08 AM

yes on the anti-fouler question.

Parmas · 08-22-2009, 11:23 AM

When I completed the 2.5" exhuast from the downpipe to the rear I really felt the difference in torque especially on the 3rd gear compared to the downpipe only. From this experience I understood well how much back pressure makes a big difference...

Tamago · 08-22-2009, 04:36 PM

it has less to do with back pressure, and more to do with velocity and/or laminar flow of the exhaust gasses. the higher the exhaust gas velocity, the more "smoothly" it flows through the exhaust pipe.

if you want more "back pressure" put in a smaller exhaust pipe.

Galavoxx · 08-23-2009, 05:01 PM

Also, did you reset the ECU? I just installed the DC header and had a similar issue. After an ECU reset I got most, if not all, of the mid-range power back.

PHXDEMON · 08-24-2009, 07:38 PM

Quote:

Originally Posted by Galavoxx

Also, did you reset the ECU? I just installed the DC header and had a similar issue. After an ECU reset I got most, if not all, of the mid-range power back.

Yes I did reset the ECU. Drove 20 miles and CEL came right back on.

PHXDEMON · 08-24-2009, 07:45 PM

Quote:

Originally Posted by Tamago

it has less to do with back pressure, and more to do with velocity and/or laminar flow of the exhaust gasses. the higher the exhaust gas velocity, the more "smoothly" it flows through the exhaust pipe.

if you want more "back pressure" put in a smaller exhaust pipe.

I just don't want to hack up the nitto midpipe. I think I am just going to return it to stock

ChinoCharles · 08-24-2009, 07:48 PM

Take it from me... on the subject of power, never make decisions based on "feel."

Why don't you go dyno that thing and make sure you're not just feeling what you expected to happen rather than what actually is?

PHXDEMON · 08-24-2009, 07:56 PM

Quote:

Originally Posted by ChinoCharles

Take it from me... on the subject of power, never make decisions based on "feel."

Why don't you go dyno that thing and make sure you're not just feeling what you expected to happen rather than what actually is?

The power feels smoother throughout the whole RPM range it just lost a lot of "pep" at low RPMS

It probably is making more power overall just less power where I typically use it on the street.

06silveryaris · 08-24-2009, 08:28 PM

Not using a straight thru muffler will help the back pressure, like a dynomax turbo muffler or similar style.

ChinoCharles · 08-24-2009, 08:44 PM

I guess it is hard to justify spending money on a dyno visit to find out if you're gaining/losing 3 foot pounds at the wheels. Either way good luck with the decision.

08-21-2009, 11:47 PM	#1
PHXDEMON View User's Garage Drives: 2007 Red Liftback Join Date: Oct 2008 Location: Phoenix, AZ Posts: 885	Increasing backpressure? I recently installed the nitto midpipe on my car along with the stock header and a tanabe madallion axleback. It feels like I dropped a lot of torque from 2-4k RPM and I usually don't rev higher than 4k Is there an easy mod I can do to temporarily inscrease some backpressure to regain some of that torque until I am boosted? Also for those of you who have the midpipe are you getting 100% success on getting rid of a CEL with that anti fouler deal the garm sells on his website?

08-22-2009, 11:08 AM	#4
cali yaris ULTIMATE View User's Garage Drives: 07 Yaris Turbo Join Date: May 2007 Location: Canoga Park, CA Posts: 14,859	yes on the anti-fouler question. __________________ Micro Image forums, online store and shop are now closed. It was a great eight year run, but it was time to focus on other things. I'm still selling parts on eBay under micro*image seller ID and customers can still make requests for anything specific.

08-22-2009, 11:23 AM	#5
Parmas Drives: Vitz RS Turbo Join Date: Nov 2008 Location: ML Posts: 576	When I completed the 2.5" exhuast from the downpipe to the rear I really felt the difference in torque especially on the 3rd gear compared to the downpipe only. From this experience I understood well how much back pressure makes a big difference... Last edited by Parmas; 08-22-2009 at 12:55 PM.

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08-22-2009, 03:59 AM	#2
AdeJong 03 "Stealth Runner" View User's Garage Drives: 2009 Yaris-S Sedan Join Date: Jan 2009 Location: LA, CA Posts: 510	what is the diameter on your exhaust? i believe the general rule of thumb is 2'' up to 120 hp, 2.25" up to 180hp, 2.5'' up to 250hp, 3'' up to 300-350ish, and 4.5'' for anything beyond please dont quote me on this. its just general hearsay from my years around other forums.

08-22-2009, 11:01 AM	#3
Reddog99 Drives: '08 Yaris Join Date: Oct 2008 Location: SoCal (Jamul) Posts: 97	If you don't usually rev above 4k, then exhaust modifications are the wrong thing to do. Over the years, I have installed various exhaust modifications on vehicles I've owned and without exception, every one that reduced back pressure (on a stock engine) also reduced mid-range torque, sometimes by a substantial amount. Most of these systems increased power in the upper RPM range, but for most street driving, that's pretty useless. If you have a big motor with lots of torque, it probably won't matter. But on a little engine like the Yaris has, a mid-range torque hit can be very noticeable.

08-23-2009, 05:01 PM	#7
Galavoxx View User's Garage Drives: Yaris Hatch Join Date: Oct 2006 Location: San Francisco Posts: 397	Also, did you reset the ECU? I just installed the DC header and had a similar issue. After an ECU reset I got most, if not all, of the mid-range power back.

08-24-2009, 07:48 PM	#10
ChinoCharles Banned Drives: LB Join Date: Jul 2006 Location: OH Posts: 7,787	Take it from me... on the subject of power, never make decisions based on "feel." Why don't you go dyno that thing and make sure you're not just feeling what you expected to happen rather than what actually is?

08-24-2009, 08:28 PM	#12
06silveryaris Drives: 2006 yaris Join Date: Oct 2008 Location: Puerto Rico Posts: 536	Not using a straight thru muffler will help the back pressure, like a dynomax turbo muffler or similar style.

08-24-2009, 08:44 PM	#13
ChinoCharles Banned Drives: LB Join Date: Jul 2006 Location: OH Posts: 7,787	I guess it is hard to justify spending money on a dyno visit to find out if you're gaining/losing 3 foot pounds at the wheels. Either way good luck with the decision.