BMC does nothing for performance

[payna]

....so are one of you 'rolling roaders' gonna try a before and after run with a bmc?? would be good to see style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

[Loopy Lupo]

if someone coughs up the 25 or as prev suggested we have a whip round i'll happily take my standard airbox and see what happens.

[dazraz_uk]

The only way to do it is to get one of those things that fakes the lambda signal so that it's what the ECU expects - but they seem to be a bit variable as to how well they work.

Any ideas where id get one of these as seen as ive bought ross's de-cat?

[The subtle modder]

Tigz we know your there you dont have to keep quoteing your own posts style="vertical-align:middle" emoid=";)" border="0" alt="wink.gif" />

This is an interesting subject as i was gonna get a decat pipe made up while having my full stainless done but after reading this im not gonna bother now

one question while all you technical people are on here though im fitting a stainless full system soon and want a loudish sporty sound so hjave been told i will 'need' to loose back pressure which will decrease my torque but where will i loose it from? bottom end, midrange, or top end? and will getting rid of the middle sillencer have the same effect as removing the cat?

thanks people

wayne

[Frankie]

I had a de-cat. I have struggled to notice any performance gain but i wouldnt say that i have lost any power. Quite shocked to hear that a gti can lose 8 bhp, if it was a similar figure for the sport i would have thought the power loss would ber noticeable. Maybe a sports cat is the way forward, who knows ey.

[Loopy Lupo]

for less hassle come mot time a sports cat has to be the way to go i guess....if you can afford it!

just to add, shame tim is selling his gti and not getting full janspeed system - would have been very interesting on the rollers!

[johnyardley]

Nikki,

Torque vs power question.

Example, motorcycle engine in a car - no torque lots of power - still go fast but because of lack of torque it would take ages to accelerate the weight.

What da ya think?

John

Fabia tdipd100

stage 3 allard 321 lb ft, 182 bhp

[Nicki]

I think you can't spell my name! style="vertical-align:middle" emoid=":lol:" border="0" alt="laugh.gif" /> style="vertical-align:middle" emoid=":D" border="0" alt="biggrin.gif" />

I get the torque/power concept, its *how* a schrick works that I don't get.

(PS Tigz, don't feel the need to repost the same quotes again mate, I just don't get it)

(Edit to say Schrick manifold)

Edited November 16, 2005 by nickilupo

[Tigz™]

Ok.

If you think of it this way.

You have a big drain pipe exhaust, you lose touque yes?

But at high revs you will get more power?

It has a valve in the manifold which is restricting the air flow at low revs, but opens up at higher revs so you get the benifit of extra power.

Does that make sense?

[Nicki]

Kinda I guess... so its all to do with pressure then? style="vertical-align:middle" emoid=":huh:" border="0" alt="huh.gif" />

[The Stig]

i would argue that if you decat a standard system removing the precat,and keeping the rest standard then i could imagine a power decrease.a standard exhaust is one of the main restrictors in a car.

*my advice would be to keep ur decat (ie down pipe) run a 200 cell sports cat and a stainless performance system.for ur lamda i would speak to jim curley at star performance who has engineered a small device that doesnt remove ur lamda it adjusts it.

hope that helps

Edited November 30, 2005 by The Stig

[Tigz™]

that doesnt remove ur lamda it adjusts it.

Ajusts the lamba?

Hows that work?

Its a sensor...

[The Stig]

not sure but he puts a spacer on ur lamda when u decat the precat and remove's this problem of engine management coming on and detunning ur car.

[stevewp]

Sounds fishy to me

[Snoopy]

The theory (I believe) is that by putting a spacer between the lambda and the exhaust, the second lambda sensor gets less exposure to the passing gases, therefore reporting a lower value back to the ECU - as it would do if there was a catalytic convertor reducing gas flow.

Whether it works or not is a different matter...

[stevewp]

As the pressure inside the cat isn't changed though, and the volume of gases is also unaltered, will it really get less exposure? I can see that it might, but I can't say I'm very convinced.

Still, I've no experience with exhausts in that sense, so what do I know?

[Jez]

ive no idea if this is helpful to ya'll

but on my polo

a decat made no difference to the at the wheel power on a pretty much standard 1.4

both times it was 91 at the wheels

this only has one cat though, and the power had shifted a little

[Arun]

im new to the site and just read this whole post.

in 2 words - im confused.

i was planning on gettin a 4-2-1 manifold and a custom cat-back exhaust, then doing the de-cat myself, now im thinking of going back to my moped

[Bikerz]

lol moped, no dont do that , get a cat back system and manifold, forget the cat, i think sports cat seems the way to go if ur that desperate for squeasing every possible bhp

[tdwindustries]

exactly

[Frankie]

ive heard of this lambda adjustment thing. I know that you can get a replacement lambda sensor for a yaris that fools the ecu into thinking the cat is still there, result being no engine light etc.

Personaly i would have thought that no cat is the way and a nice tight back box to retain some pressure.... surely something that was made to protect enviroment cant be good for performance aswel, thatd be a miracle surely. style="vertical-align:middle" emoid=":wacko:" border="0" alt="wacko.gif" /> My sport read 104.5 on rolling road with a decat and precat still in so it cant be all bad.

who knows ey.

[Arun]

are there any problems with your sport after de-cat? ie. dash light, fueling probs etc.

if u say theres no problems ill try do it next week at work

[Bikerz]

Personaly i would have thought that no cat is the way and a nice tight back box to retain some pressure.... surely something that was made to protect enviroment cant be good for performance aswel, thatd be a miracle surely. style="vertical-align:middle" emoid=":wacko:" border="0" alt="wacko.gif" /> My sport read 104.5 on rolling road with a decat and precat still in so it cant be all bad.

who knows ey.

what have u done to urs to get 104.5 bhp? just decat it? if thats the case then u have answered the question. DECATING does HELP PERFORMANCE, and alot be the sounds of it, nearly 5bhp for removing the cat, tho im guessing a torque loss?

exactly

*faints*

yet again someone agrees with me style="vertical-align:middle" emoid=":D" border="0" alt="biggrin.gif" />

[VWR Lupo]

what have u done to urs to get 104.5 bhp? just decat it? if thats the case then u have answered the question. DECATING does HELP PERFORMANCE, and alot be the sounds of it, nearly 5bhp for removing the cat, tho im guessing a torque loss?

*faints*

yet again someone agrees with me style="vertical-align:middle" emoid=":D" border="0" alt="biggrin.gif" />

I havnt done any thing to my engine apart from a K&N and i got 105.8bhp.

Think it also depends on how run in the engine is, my lup as done 70.000 miles now and have been reved pritty hard with regular service and good oil (Castrol RS) which i change every 5.000 miles style="vertical-align:middle" emoid=";)" border="0" alt="wink.gif" />

Edited December 24, 2005 by VWR Lupo

[Arun]

i dont think engines are ever EXACTLY dot on the manufacturers claims, but as long my bhp stays in triple figures, and iv still got enough tourque, i dont care. this car is gunna be more for show and sound. ill do performance on my next car