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Discussion Starter · #1 ·
Much has been written about changing exhausts, decat pipes, downpipes and turbo elbow (didn't know there was such a thing but now i do i want one - anybody else suffer from this?). I assumed that by putting a bigger system on you would reduce exhaust back pressure and this was a good thing. I have a Blitz Nur system, Magnex de-cat pipe and Magnex downpipe (but no elbow!) and the system sounds fantastic. I also have the HKS Racing Suction Kit so i'm in theory getting more air in. Overall the system does give an increase in mid - top end pull, but, as has been written elsewhere it does seem to have lost a bit of bottom end torque. Why is this - is it the de-cat, or the downpipe? Will a new elbow improve things?

Also, from a cold start for the first couple of times up the rev scale the engine stutters a little, give it a good boot and all is OK (I had this on my 5 also with a de-cat). When idling the engine hunts around. Is this because the cat is taken out - is there a sensor in the cat? Is there any harm with this out?



Discussion Starter · #2 ·
Hi Kevin!

I think that you have a very good exhaust fitted,and probably the turbo elbow will improve it further.

When I bought my evo v rs there was a supersprint stainless steel cat back system and the power curve was very good(supersprint had graphics shwing 299bhp and better torque than standard with the cat back).Then I fit the downpipe and decat pipe and even if the power at top end was improved the low end was worst then before(supersprint graphics was showing 306bhp at higher rev than before and slightly lower torque at higher rpm!)

If the exhaust system makes a 25/30bhp difference on the evo vi is probably because the standard system is restrictive,and so it makes a lot of back pressure.
When you have a free flow system it's normal that you feel less response at the low end.

When you fit the cat back system the power and torque range is improved everywhere,so it's
obviously better than standard without side effects.Once you fit the downpipe and decat your
evo will be faster but you will loose some low end.

About iour idle problems I don't think that the decat pipe have something to do with it.
I had these kind of problems when i had a vent to air blow off valve fitted.Do you have one?

If you have a bov try to go back to standard.The best you can do is buying a recirculating
dump valve,power engineering or reid.

Discussion Starter · #3 ·
The factory exhaust and inlet installation is designed to provide a good compromise between ultimate power(torque) and drivability within the confines of emissions and noise.
When these systems are replaced with different items , engine characteristics will be changed , thus the powerband , max torque , max bhp , turbo boost threshhold will all be changed specifically and in relation to each other.
To obtain the max benefit from intake and exhaust mods , the ECU shud be remapped to increase boost (now that the exhaust can use it) with fueling and ignition to match.
This will then improve torque band and boost threshold , thus providing a magnitude of improvement over standard.
Obviously most aftermarket systems are intended to provide improvement without remapping , so more torque and bhp will (or shud) result , it's just that u can have more with remapping.
Lean running can occur with replacement intake and exhaust because effectively the engine is processing more air with the same amount of fuel , as the ECU can only compensate so much with the factory map.

However with standard boost settings this shud not be a problem.

Basically it's difficult to get something for nothing , compromise is always in the picture.

Discussion Starter · #4 ·
So Evoboy are you telling me I might get better fuel efficiency / mileage if I upgraded my exhaust? I'm running stock boost with a decat pipe, though as I mentioned earlier I plan to upgrade the entire exhaust system including the downpipe.

I replaced my filter to a K and amp;N unit. It improved fuel efficiency and power noticeably. Would an exhaust help me in the search for fuel efficiency too? I know Mouton would call me dumb for buying my Evo and worrying about fuel consumption! border|EQU| 0 align|EQU| absmiddle >

Many thanks! [img] border|EQU| 0 align|EQU| absmiddle >

Discussion Starter · #5 ·
Afraid not , the specific fuel consumption will remain the same due to the engine map , actually because the engine will develop more power the actual fuel consumtion will increase when using the performance , it wud stay the same or may reduce very slightly at cruising speed off boost border|EQU| 0 align|EQU| absmiddle >
The only way to improve fuel consumption is to use a fuel controller or remap the ECU.

Discussion Starter · #6 ·
Wow your'e right about poorer fuel consumption cruising off-boost! I plan to get a fuel controller and fiddel with the first 3K rev range, in the interest of quicker pick-up and fuel economy (my engine seems to have a tendency to bog at lower RPM's, due to I think a very rich mixture). When I got the car, it was using low-comp aftermarket pistons, which led me to believe that the ECU has been remapped for greater fuel flow. What do you think?

Many thanks!

Discussion Starter · #8 ·

How I wish I could afford one! border|EQU| 0 align|EQU| absmiddle > Way beyond my budget! [img] border|EQU| 0 align|EQU| absmiddle >


Funny, I was talking to a guy who was into racing cars, and he was so adamant to get me into either remaping my ECU or getting a Motec if I install an intake / exhaust combination. I do plan on keeping the stock boost settings (I'm quite nervous about upping the boost nowadays) and plan to keep my E4, so I'll just follow what you said about not needing to remap the ECU (in the interest of not running lean / safeguarding the engine) and keeping the stock boost setting (0.9 bar).

The last straw was when he told me how much it would cost me if his friend would remap my ECU: 140,000 Pesos or a little over 2,000 UK Pounds! I do believe I can get a Motec for that price!

Discussion Starter · #9 ·
nothing wrong with improving your fuelling,they do run rich part throttle
and if you get better economy in the bargain,all well and good
similarly,a boost controller will allow you to up the boost just a little ,if you wish to play really say,1.1 bar,which will give you more kick
but when you turn it off,you run low boost and safe fuel that way too
nothing wrong with saving petrol,trying to tune on a budget is where problems begin

evoboy,im dying to know,will this 400|PLS| bhp monster you are building run on normal or super unleaded ?

Discussion Starter · #11 ·
Hi Evilution,

I noticed that you have a Magnex system all the way to the de-cat pipe, did you start off
with the full Magnex system? If so does the Blitz Nur system sound better than the magnex
and which one is louder?

Discussion Starter · #12 ·

I didn't have the Magnex full system and haven't heard one so can't give you an opinion, I only have the Magnex downpipe. The Blitz is very loud, certainly louder than the HKS Super Dragger I had on my 5. Sounds good though - better than the HKS did, IMO. Would get a bit much on a long journey - but then you can put the tailpipe insert in that makes it a lot quieter.

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