Hi all sifu2

recently, my car(AT) are having 2 issues:-

1. gear shift earlier than before, they shift at between RPM 1.7-2.5, and im stepping the pedal as usual, not too hard/ light.

And 2. no pick up unless i step hard.


im not sure if it was related to my full exhaust changed recently, due to crackin' here n ther.
this is wat recomended:
4-2-1 (nt sure the size, but told its only have 1 size for my model)
2 bullet (long n sort)
1.6 piping
mugen twin loop (imitation)

car driven:-
Honda City SX8 (yr1998)
1.5 AT.
_____________________________________________________________________

thank you very much

This post has been edited by Bob-Marley: Dec 30 2014, 11:05 PM

Piping size same as before?

yes it is. bt i din measure the ori 1, nt sure wat diff it is.
but i GUESS just a slightly wider. huhu

current-
1.5 in, 2.0 out for 421, 1.6 piping.

try to post here.. there's a lot people can help u there..

Noted! great 1, will go thru them and see...thanks yo

I had an SX8 2001 model as well.

I changed exhaust as well because it had rusted. I did not choose Mugen Twin loop because that time only have 2 choices for the inlet which is 2.0inch and 2.5inch.I choosed something with smaller inlet S flow muffler. Piping size I also up it to 1.6inch from original 1.5inch.

I believe its your muffler inlet too big, that is why the car like no power.

I remember last time the exhaust shop did solder a silencer inside the bullet to increase back pressure / scavenging effect.

This post has been edited by k!nex: Dec 31 2014, 11:56 AM

Hello

oh really? i took the 2 inch, cos its a smallest. but i thot the muffler will not affect the performace but only sound...danq

Gear box change fliud on time? every 20~30k?

Usually changing new exhaust system u will having different powerband.
Most car after change whole system, specially header, the car refuse to go when hard press, or refuse to go when light press... Thats why sometimes ppl not recommended to change header / decat if u did not plan to retune your car with piggyback.

i guess its chge around on time, now using penzoil, (honda atf too exp)

piggyback = smtg like emanage?

it was chged bcos cracked evywher ...n the short bullet come after, cos ihav no pwer at pickup+gear shift earliy, pomen told to add-in a short 1....no gain a very little, n rpm goes quite high like dw to shift.

isit true that gear shift based on back pressure? (wana make sure if it is wat causing gear shift early)
damn.............

Yes, something like emanage...

Actually I have some recommended set up for 1.5 auto, for model with cat con... there are few choices.*without change header

1st : change everything after cat con... to 1 long bullet + system block type muffler + 1.6 mandrel bent or 1.75 crush bent.

2nd : Decat ( if the oem cat is stuck ), replace cat with a twist type bullet, or replace with a straight through short type bullet, other same with the 1st choise.

Technically the back pressure change your car powerband, which might made higher or lower low end torque, which will slightly effected gear change.
Exhaust gases back pressure din`t effect your gear change.. your exhaust gases will never go to your gear box marh...

thanks!! for the suggestion bt my header sudah crack, same goes other.

1st- wat is system block type muffler? (gas go around in the box bru keluar?) n muffler wit bent bent?

2nd- r u sayin replace the 1 of the '2' in 4'2'1 to a short bullet? o.o

u'r right, gas dont go into gb. i rmb i saw somewher sayin ie. less backpressure on AT will make shift chge earlier, nt sure abt is true or wat....hehehe

Gear shift is supposed to based on engine load and throttle demand. When you changed the exhaust, it affects the back pressure, which affects engine load. The ecu detects higher load (due to back pressure) so it may thought that you're climbing up hill, or towing something, so it don't change gear as it thought you need more torque/power at the higher rpm range

in opposite, can i say if ecu detect less back pressure then it'll shift to next gear?
**less back pressure = no load OR/AND gas pass thru fast due to (1) nt much restriction on muffler box (2) muffler in/outlet size too big for ur car

sry noobie

Honda ATF too expensive ??? It is like RM22/L in 2013 . Your car only needs 2.5L . Use only Honda ATF-Z1 . Don't simply listen to the mechanics and use other stuffs. The gearbox is much more sensitive than the engine. You're really asking for trouble if you try being cheapskate on this stuff.

For honda city sx8 larh...
I recommended to replace header with a design which same with your stock, sx8 originally comes with long type 4-2-1 if I`m not wrong.
So u just get a long type 4-2-1.

So here is the setting, Header 4-2-1 > 1.6 piping > 40cm bullet > 1.6 piping > system block muffler.

System block type muffler are those tri flow/dual flow/twin loop/chamber type.
Tri flow muffler in local they called it S-flow.

The exhaust backpressure effect your engine power... and technically the power effected your gear change.

I usually never ask my customer to change header and cat con, unless it is crack or rust, talk about cat con, i think city sx8 dun have 1.

haha den nt sure wat make me think its expensive lol
probably bcos of gear shift prob. nt fixed tho...wil hav atfz1 soon he2

THAT is wat my setting at 1st place yo..until las week addin 2nd bullet, help a LITTLE at low end, little + top speed 'lesser'......

yep only 1 size for sx8, wat pomen said la....n sx8 do have cat,, probably nt functionable after 15 yrs, nw, 16

ard on twinloop 2inch. mayb wat k!nex said is right, too big for a 1.5 AT, cudn 'keep' pressure....or else itself doesnt restrict much......BUT, why some other r doin fine wit it, hahaha.....

SX8 original catcon comes together with the extractor as 1 piece. Once you change extractor, the catcon is gone too.

Did u double confirm with yout current header size, and your muffler should not bigger than 30cm..., 2.0 is okie for u,
and how long was your header lenght?

if im nt mistaken, the header size - 1.58, 1.6, 2.0 accordingly. il update here once i get info (header length+muffler) from the mech

This post has been edited by Bob-Marley: Jan 4 2015, 09:18 PM