Jump to content

decat+manifold=less power-WTF?


Recommended Posts

k chaps,installed decat and stainless manifold along with new gaskets, i now have slightly less power and a quieter ehaust note (brand new std turbo too)

i still have the standard exhaust system, anyone know whats happening here???? :p

Link to post
Share on other sites
Have you got a boost gauge, with the free-er flowing mani and decat you may have a bit of a boost drop, or just a leak.

What sort of boost control do you have?

i only have the standard boost gauge to go by but it appears to boost all the way.

currently have the solenoid bypassed but i can re-install the hi/lo if needed.

the actuator came fitted to the OEM turbo complete so should be fine?

its kinda hesitant at the bottom end now and i get a small amount of whitish smoke when idleing for a while-the very reason i changed the turbo!!(albeit it used to be lots of smoke..) :(

my best guess is that the stainless manifold gets much hotter than the standard cast one-heating up the EFI pipe,indeed i made an alloy heat shield which helped a small amount.

i was going to route a new intake pipe in front of the rad but was told i'd get boost creep??

how does this manifest itself and ultimately is it a bad thing as there seem to be different ideas on this one ;)

Link to post
Share on other sites
i only have the standard boost gauge to go by but it appears to boost all the way.

currently have the solenoid bypassed but i can re-install the hi/lo if needed.

the actuator came fitted to the OEM turbo complete so should be fine?

its kinda hesitant at the bottom end now and i get a small amount of whitish smoke when idleing for a while-the very reason i changed the turbo!!(albeit it used to be lots of smoke..) :(

my best guess is that the stainless manifold gets much hotter than the standard cast one-heating up the EFI pipe,indeed i made an alloy heat shield which helped a small amount.

i was going to route a new intake pipe in front of the rad but was told i'd get boost creep??

how does this manifest itself and ultimately is it a bad thing as there seem to be different ideas on this one ;)

Well the smoke could just be any residue that was one the new mani and decat burning off, most do this when just fitted, however if it doesn't stop fairly soon then I'd start looking for a problem elsewhere.

I'd advise getting a boost gauge first before doing anything else, so you know what the boost is running at, then also at the least an hks actuator to give you more control over the boost.

The reason it may not feel as quick anymore is probably because you've had a slight boost drop and are maybe getting a little more lag with the free-er flowing exhaust, the hks actuator should help this, it'll definately make it feel quicker anyway.

Link to post
Share on other sites

totally agree ^^^ you shouldn't try and up the power of the car without knowing what you are boosting at, definitely get a boost gauge even if its a cheapish one of ebay it will do the trick, then get a hks actuator fitted this way you can adjust your boost using the actuator and see what is boosting at using the boost gauge, if this doesn't even out the loss of power there is a problem somewhere else

Link to post
Share on other sites
I wouldn't recommend just a cheap gauage off ebay, bill who I just sold my old autometer gauge to noticed a 0.2bar difference between the readings on the gauges, his old one was a cheapo off ebay. ;)

well i didnt mean mega cheep i said 'cheepish' i have an autogauge boost gauge it's not the best gauge in the world but i find it to be very accurate and there not to exspensive.

Link to post
Share on other sites

just putting a decat and exhaust system on my misses stock gt made quite alot of difference, sits at 9psi on full chat and then drops a tad at high revs (stock actuator) next mod is the mani,

although cant see how its ganna make it slower, i can understand there being slightly more lag with the uprated mani as ive noticed that before on my old gtir and evo 3,usually because the runners have a longer run and have a larger internal dia than the stock mani. you will prob notice it pulls better at high revs though

Link to post
Share on other sites
totally agree ^^^ you shouldn't try and up the power of the car without knowing what you are boosting at, definitely get a boost gauge even if its a cheapish one of ebay it will do the trick, then get a hks actuator fitted this way you can adjust your boost using the actuator and see what is boosting at using the boost gauge, if this doesn't even out the loss of power there is a problem somewhere else

i see what your saying chaps, i have a toytuning actuator on order (for some time)which they said was in stock but after giving my details i havent heard anything ,i even tried pm'ing toby but i havent heard back still,are they on holiday or should i start 2 worry?- ive had no problems in the past dealing with TT.

still got a small amount of whitish smoke at idle sometimes ,ive checked the coolant and pcv valve whats left? hope its not rings or sumpthin major :-(

Link to post
Share on other sites

check everywhere for air leaks mate. i had one on my decat the other day. my car was running like an absolute bag of shit. now ive fixed that its back to normal.

Link to post
Share on other sites
check everywhere for air leaks mate. i had one on my decat the other day. my car was running like an absolute bag of shit. now ive fixed that its back to normal.

i know what u mean,i had the egt probe fall out yesterday-you really know when its blowing and yea really ran like a bag-o-shit then but luckily it was still attached to the cable and had flicked up under the undertray-how lucky was that!! ;) ..about the only luck ive had tho :(

anyways ive triple checked 4 leaks since and no sign what now :p

Link to post
Share on other sites
maybe that damaged it mate? its a possibility

unfortanately the probe fell out after mate....:-(

i keep changing the oil to as it starts to smell burned quite quickly,could that mean anything?

Link to post
Share on other sites
  • 2 weeks later...

Sounds like there isint enough compression of the exit gases. either a leak or a possibily of you system being too "free flowing" exaust systems work best under slight compression which aids transport of gases out of your exaust system. just had a look on the net and came across this. is your engine powerful enough to be puming out a decent amout of exit gases? a remap mite also help for various problems you have stated. hope this helps

jon

Link to post
Share on other sites
Sounds like there isint enough compression of the exit gases. either a leak or a possibily of you system being too "free flowing" exaust systems work best under slight compression which aids transport of gases out of your exaust system. just had a look on the net and came across this. is your engine powerful enough to be puming out a decent amout of exit gases? a remap mite also help for various problems you have stated. hope this helps

jon

this is very unlikely as he has stock exhaust system in place.

Link to post
Share on other sites

interestin ideas folks,

so far as i can tell theres hardly any smoke now and having driven it for a while with the mods it feels like it has less torque certainly-judders a bit when u pull away and it never used to.

it pulls for longer in gear tho probably letting u shift like 1000-1500rpm later without the power dropping off and according to the boost gauge seems to hit max boost faster but getting wheelspin in second gear is nigh on impossible were as it used to be a piece of cake so a fair difference i'd say.

i live in the south and i cant find any performance related garages anywhere local- anyone know of any in winchester,romsey,eastleigh,hampshire in general would be a big help!! :rolleyes:

Link to post
Share on other sites
  • 1 month later...

get a decent boost gauge mate.. and i dont think you have an egt probe mate.. the top one is your lambda/ 02 sensor which determins your air fuel ratio.. if this is damaged your fueling could be all over the place.. smoke/ vapour indicating its running rich...

on another note the bottom sensor is a cat temp sensor so having a decat i very much doubt that this is inserted..

so just to confirm.. you have decat, stainless mani but still standard exhaust?

Link to post
Share on other sites
  • 3 weeks later...
get a decent boost gauge mate.. and i dont think you have an egt probe mate.. the top one is your lambda/ 02 sensor which determins your air fuel ratio.. if this is damaged your fueling could be all over the place.. smoke/ vapour indicating its running rich...

on another note the bottom sensor is a cat temp sensor so having a decat i very much doubt that this is inserted..

so just to confirm.. you have decat, stainless mani but still standard exhaust?

just back from my hols yay!

yes i have all of the above (i think your right-must be cat temp,its defo bolted into the bottom of the decat tho)

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...