Over fuelling N/As - Apexi SAFC

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.

Wide band AFR fitted? How do you KNOW if it's overfuelling or not? If you are concerned 1st step would be to measure the fuelling under lots of different conditions.

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.

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.

Excellent point, plus I see some vac tanks that leak or have faulty one way valves, or the hard to see / get at hoses to them are collapsed, perished or split.

Vac tank? On an N/A? Yep, a lot of owners don't even know they are there. Similar in looks and placement to the tanks on a TT.

My ACIS valve works perfectly, but still rich over 4k.

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.

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

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?

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.

I gave it a try this afternoon and with the ACIS running closed, the AFR's behave much the same.

Maybe it's because the 68mm t.b. can't deliver enough air?

So what would be needed for better airflow, Bigger entry or is it imposibly exspensive

That may not be the cause but a larger t.b. would certainly help the bhp without loss of ACIS valve torque gains.

Should I have not been side-tracked with the supercharger conversion, I was planning to make an adaptor and use a 72mm t.b. from a 1UZ-FE.

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 )

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.

Got my 2 new O2 sensors today from the states. Came to around £78 including delivery and import tax for the pair.

http://www.rockauto.com/catalog/

part number 234-1055

got this information from another thread on here.

I think Jagman's hit the nail on the head with this one.

I cant see it being the 02 sensor's that cause this same problem after fitting a manifold more like the design of actual manifold itself.

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?

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

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.

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.

What Walbro pump fits the N/A?

What Walbro pump fits the N/A?

Same as the jap tt GSS342

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.

Without AFR gauges the fystery will continue.

Without AFR gauges the fystery will continue.

I'm just going off what is posted on here and the US + aus forums.

I will try and get mine checked when the new engine and mani are in.