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Over fuelling N/As - Apexi SAFC


Neil-NA

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I remember a discussion on here not too long ago stating that N/As over fuel quite badly especially when they have an aftermarket manifold which will lead to a small loss in power (i know but every little helps when you dont have a lot to start with)

 

Would an Apexi SAFC NEO help or solve this? i know they are very basic and most will say use a proper piggyback or full standalone but i am thinking as a budget solution here.

 

Reason i am asking is i keep reading the US and aus forums and they seem to use them all the time when not chasing mega power but i never see it get mentioned on here.

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Improved manifolds/exhaust do lead to N/A's over fuelling, mine is a perfect 14.7 cruise to 13 WOT, except when over 4k drops to 10.5.

 

Changing the manifold dropped it a bit and changing the exhaust a bit more, but the biggest change was caused by insulating the manifold.

 

I have tried moving the AIT sensor to a very warm place to try and lean it out, but it makes no difference, soon it will be getting the AEM, so for now I trundle around below 4k.

 

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js800_AFR_dyno_003.jpg

Edited by David P (see edit history)
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Neil, be sure that your variable length intake runner system is functioning as it should. Have a look for split vacuum pipes or in my case, completely disconnected!

 

I had my NA dyno'd with the actuator disconnected unbeknownst to me and the engine ran rich at anything over 4k rpm as the air flow was less than it should have been at that engine speed.

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Hi to all, This is an interesting read. I have recently fitted a full decat and a new manifold she sounds awsome but it seems that fuel is not lasting as long I will get some simple figures up in a min. The safc how can that help / work? It's not a massive problem but does it cause massive loss of power the reason I ask when she is slightly cold she shifts but when she warms up it feels very laggy pick up any help would be great.

 

 

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Because not many folks tinker with N/A's, this over-fuelling response to increased exhaust flow remains a fystery.

 

A piggy back would sort it, yet to discover what is causing it could lead to an easier fix.

 

The over-fuelling appears to coincide with the opening of the Acis valve and/or ECU open loop.

 

I will doctor the ACIS on mine to stay closed and see what happens?

Edited by David P (see edit history)
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Thanks for the answers guys :)

 

I havnt checked my fueling I was just referring to a thread posted not so long back stating that n/as with aftermarket manifolds are likely to overfuel. I wanted to know could a SAFC be used to lean it out a tad as there doesn't seem to any any other solutions.

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Because not many folks tinker with N/A's, this over-fuelling response to increased exhaust flow remains a fystery.

 

A piggy back would sort it, yet to discover what is causing it could lead to an easier fix.

 

The over-fuelling appears to coincide with the opening of the Acis valve and/or ECU open loop.

 

I will doctor the ACIS on mine to stay closed and see what happens?

 

 

It could simply be the exhaust manifold is not scavenging , it hits an rpm and loses scavenge , thus its not pulling air through the engine from intake and yet the fuel stays the same demand -open loop - thus you run rich

Tricky things exhaust manifolds on na cars , small changes can have a large effect , decats, exhaust matching ,lengths and diameters -( wrapping will change the temperature and thus the speed of gas flow, again altering the scavenge and sweet spot of the manifold )

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At £50 worth of premium fuel I'm getting a little under 194km and that's mixed with easy and hard driving if that helps at all. Thats the best I can give

 

When were the oxygen sensors last renewed? Worn O2 sensors is the usual reason for poor mpg's.

 

The sensors should be changed every 30-50K miles, if the sensors are worn out the ECU will default to a rich mixture which has a significant effect on fuel consumption - and a small but noticeable effect on performance. The 2JZ-GE has 2 sensors, they are not cheap but they should pay for themselves in fuel savings quite quickly.

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This over fuelling seems to be reported in connection with many if not most flavours of N/A tubular manifold, cat removals and cat backs.

 

I can't see them all being 'wrong', yet can't understand how increasing air flow could increase AFR's?

 

Nic, do you have any test results from your old manifold and exhaust systems?

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gjp,

 

Are you monitoring your AFR? if so please post up any change after fitting the new sensors.

 

This is curious.

 

http://www.mkivsupra.net/vbb/showthread.php?253680-Run-with-no-lambda

 

The manifolds not on yet but I will have taken off the 2nd cat and replaced with a straight pipe, added Nics's tubular manifold, walbro fuel pump and Mines ecu.

Not got an afr gauge I'm afraid.

Edited by gjp
forgot the pump (see edit history)
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Bump.

 

So back to the Q in hand, will an SAFC lean it out a bit.

 

I understand its probably not ideal and the manifold will probably be what is causing it to run rich in the 1st place but unless spending 1000's on a custom manifold most of us will be stuck with nics,XERD,MVP,AB88 manifolds.

 

I havn't actually checked if it does run rich though i have just gone of research which 95% of the time suggests its going to be rich.

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