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Old 29th June 2004, 14:09   #1
GTO
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So I spoke to Automech for a full custom exhaust in my Vtec. A complete set with headers, mufflers, expansion chambers etc. comes up to 8750 - Excellent value in my opinion keeping in mind that Automech is very renowned for its professionalism and experience in this line of work.

Buttttttttt the hurdle came after I spoke to Ichibaan and Linkway. Basically, the minute you install a free flowing exhaust system your engine warranty is defunct. Not surprising since it is a heavy modification to an already complex engine.

And the timing could not have been any more perfect. He is in possession of a 2000 year Blue Vtec which has a full custom exhaust set installed by a "professional". The car has encountered compression problems since quote "The free flow exhaust systems make the exhaust gases exit directly. The Oxygen sensors are refitted in an area that is not originally meant for them. The cat is thrown out". The blue Vtec's engine is totally finished. Cost of repair? In the region of 2.5 lacs!!!

I am out of this free flow thing for my Vtec. No ways am I going to install something that is going to kill my warranty and potentially damage the engine.

GTO
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Old 29th June 2004, 14:15   #2
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What do the automech guys promise? Boost in top end or mid range?
A subtle and safe mod would be to get a replacement K&N or UNI air filter and change the 3rd and 4th section of the exhaust to a free-flowing one. Subtle but nice.


The expansion chambers u must save fo the bike though...LOL
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Old 29th June 2004, 15:45   #3
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Quote:
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Quote[/b] ]What do the automech guys promise? Boost in top end or mid range?
Hey Tom, though they promise an increase throughout the powerband, it is more concentrated on the top.

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Old 29th June 2004, 16:08   #4
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GTO, I think it's less of a risk for older machines. Where you don't have MPFI and cat.
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Old 29th June 2004, 16:09   #5
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free flow's are good for any engine. maybe the blue vtec had a poorly balanced exhaust system! i have a full free flow system in my lancer and haven't had any problems.
read any technical website that this is what they will say too!
most of the indian dealers are quite ignorant about mods and belive me - would be most happy to say that ur warranty is void just because of the mods you made!
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Old 29th June 2004, 16:11   #6
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the automech system for the non-vtec city was quite good - a friend of mine got it for his 1.5 city. this prompted me and another friend to order the automech systems for our lancers.
i havent experienced the vtec with an automech system, but i reckon they shud be quite good!
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Old 30th June 2004, 01:45   #7
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Quote:
Originally Posted by [b
Quote[/b] ]"The free flow exhaust systems make the exhaust gases exit directly. The Oxygen sensors are refitted in an area that is not originally meant for them.
Well now here's where the problems start. Essentially exhausts are designed not only as a means of having exhaust gasses exit out but also to create backpressure. What free-flows do is prevent the exhaust gasses from going back into a loop that creates this backpressure. And its not really good.

It could lead to the engine running a real lean mixture (lean means where the air to fuel ratio is lower) and could lead to overheating of the engine and subsequent damage to the engine.

The Oxygen sensor in modern day cars in the exhaust is essentially a sensor that measures the amount of oxygen coming out of the exhaust chamber. If its less, it sends it back for further (purification?) thus completing what is essentially the "lamda loop".

Having had a small experience with Automech and having used their exhaust system for a year, all i can say is this. Have a free flow only if you really really need that performance bump for a car that is used only for performance runs. O/wise you are playing around with the mechanicals a bit too much. A blown engine is not something i am surprised with. But its a stark reality.

Honestly, K&N and a high lift cam as well as a slightly modded chip shud give u tons of fun. And very much within the dynamics of the engine.

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Old 30th June 2004, 02:09   #8
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Quote:
Originally Posted by [b
Quote[/b] (Revvmaster @ June 30 2004,00:15)]the amount of oxygen coming out of the exhaust chamber. If its less, it sends it back for further (purification?) thus completing what is essentially the "lamda loop".
The function of the oxygen sensor is to see how much unburtnt oxygen there is in the exhaust gases, and use that info to better judge the air/fuel mix for a complete burn, and make the neccessary changes to the amount of fuel being added henceforth.

I believe the "purification" your talking about is the EGR (exhaust gas recirculation) which is only used for emmisions purposes.

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Old 30th June 2004, 02:11   #9
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Yup EGR it is.

And yea, thanx for reminding me bout the oxygen sensor pal...kept wondering all the time while writing the reply that i was missing something...

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Old 30th June 2004, 11:38   #10
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Quote:
Originally Posted by [b
Quote[/b] (Rehaan @ June 30 2004,00:39)]The function of the oxygen sensor is to see how much unburtnt oxygen there is in the exhaust gases, and use that info to better judge the air/fuel mix for a complete burn, and make the neccessary changes to the amount of fuel being added henceforth.
if so then how does the engine run a lean mixture?
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Old 30th June 2004, 14:26   #11
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Quote:
Originally Posted by [b
Quote[/b] (Tom @ June 30 2004,10:08)]
Quote:
Originally Posted by [b
Quote[/b] (Rehaan @ June 30 2004,00:39)]The function of the oxygen sensor is to see how much unburtnt oxygen there is in the exhaust gases, and use that info to better judge the air/fuel mix for a complete burn, and make the neccessary changes to the amount of fuel being added henceforth.
if so then how does the engine run a lean mixture?
Hey Tom,

It wasnt me who said lean mix, but let me just take a guess at the reasons -

Maybe, the Oxygen sensor being relocated in the exhaust system is now getting slightly different values due to the further chemical reactions that may occur even after the gasses exit the combustion chamber.
Also, maybe the rate of airflow or the different temperature of the sensor or gasses causes different readings.

Thats what i could think of...
cya
R
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Old 30th June 2004, 14:41   #12
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as per my understanding the cars electronics will automatically re-adjust the necessary air/fuel mix...in carb cars jetting has to be done manually and is a big pain to get it spot on.

and I dont think it's right to say free flows eliminate back pressure completely....in 4-strokes a minimum or optimum level of back pressure is required.

the correct way to build a free flow would be to use some software or simulator...does automech use this?

Going back to basics:
Improving the breathing of the engine will make it more efficient.

At the intake:
Cold air intake set-up
Performance air-filters...etc.
air scoop

Exhaust:
Free Flowing Exhaust
Keep the exhaust hot

More power = more heat
More power = quicker wear n tear

these mods are in my opinion the safest and simplest and power can be increased atleast by 3-5% easily

Your next step would be shaving heads, high lift cams, big bore...etc



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Old 30th June 2004, 15:01   #13
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Quote:
Originally Posted by [b
Quote[/b] (Tom @ June 30 2004,13:11)]as per my understanding the cars electronics will automatically re-adjust the necessary air/fuel mix...in carb cars jetting has to be done manually and is a big pain to get it spot on.
Very true,

but thats exactly the point. The oxygen sensor just senses oxygen and those values are sent to the ECU.
Now say if it was at the original position it would sense a value of X, but if it was moved 3 inches down the pipe it might sense a value very different from X, and hence the ECU would be making incorrect adjustments.

I agree with you on everything else you have said, you just have to keep in mind that the automobile engine is a very sensitive peice of machinery, and every little thing is interconnected and has to be functioning perfectly for a complete perfect functioning.
Little errors, especially in modern engines could pile up into huge problems someday, therefore its essential that any engine modifications are done with care and knowledge.
When it comes to automech i cant comment, simply because i havent seen their work and how they work.

cya
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Old 30th June 2004, 15:26   #14
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Quote:
Originally Posted by [b
Quote[/b] (Rehaan @ June 30 2004,13:31)]
Quote:
Originally Posted by [b
Quote[/b] (Tom @ June 30 2004,13:11)]as per my understanding the cars electronics will automatically re-adjust the necessary air/fuel mix...in carb cars jetting has to be done manually and is a big pain to get it spot on.
Very true,

but thats exactly the point. The oxygen sensor just senses oxygen and those values are sent to the ECU.
Now say if it was at the original position it would sense a value of X, but if it was moved 3 inches down the pipe it might sense a value very different from X, and hence the ECU would be making incorrect adjustments.

I agree with you on everything else you have said, you just have to keep in mind that the automobile engine is a very sensitive peice of machinery, and every little thing is interconnected and has to be functioning perfectly for a complete perfect functioning.
Little errors, especially in modern engines could pile up into huge problems someday, therefore its essential that any engine modifications are done with care and knowledge.
When it comes to automech i cant comment, simply because i havent seen their work and how they work.

cya
R
Totally right Rehaan,

Today's electronics are very sensitive and care has to be taken when making even the simlest of modifications. Thank god we haven't reached the level that the new Beemers are at just yet though!

Just a point about the O2 sensor though. Even if there is a problem with it like placed in the wrong location or not working, the only real effects would be the car running either lean or rich and hoigher emission levels. What may have happened with the honda engine that GTO was talking about was that it was running too lean. If the driver frequently drove the car hard, shifing at the redline, which he probably did if he fitted a full system, then the lean running would have been responsible for this problem.

However, a failed O2 sensor on a regular car can have the same effect, so pay attention to your car's behavious.

For more info on O2 sensors check out this link

Rtech
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Old 30th June 2004, 16:09   #15
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ok...so why move the sensors in the first place???
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