R34 Rich Fuel Mixture - Apexi Afc

[robjay]

Hi all, need a bit of guidance. Had my newly acquired r34 gtt auto dyno'd and made 145kw at the wheels - is this a bit low for a NEO engine?

Health check revealed nothing bad accept for the fuel mixture was rich, the dyno mechanic explained that the mixture should be around 10 to 11 throughout the run but by car pretty much shot to 14 as soon as boos came on not sure what this means apart from that its thirsty. Also psi peaked early at 9psi but dropped off to 7 for atleast 1/2 the curve due to rich mixture. Not as smooth a power curve as I hoped for form a stock setup.

He then suggested to get an apexi afc.. I think its now called a superafc.

Question is what is the best product out there as far as tuning air/fuel maps for a skyline r34.. and if I do decide to get serious would I be better of getting an entire engine management unit such as power FC.

I have a fair idea of the concepts and theories behind afc & tuning but not familiar with what products are best matched for skylines & in particular the neo rb25

I'm serious about a full ecu, price is not really an issue but I've heard bad stories about lack of experience out there to tune neo's and high knock counts as a result of going custom.

Plus I've seen youtube videos of a 10,000 rpm skyline is this really possible - I would like to one day pursue an engine build that has ability to hit 8 to 9 k rpm, for simplicities sake what would it take to make a rock solid 8000 rpm rb25, is this foolish? .. would it be better to go high torque low rpm

What thoughts are there around having a large high lag turbo plus a supercharger to make up for the lag down low , has anyone tried this?

[32hills]

im also interested in the apexi safc as i cant afford a full computer at this stage will be watching this thread

[mad082]

the air fuel ratio should be about 10 to 11 for a stock car, and if it has been tuned it should be about 12. 14 isn't richer than 10 or 11, it is leaner. the lower the number the more fuel there is as it is the AIR/FUEL ratio, so when saying 10 or 11 or 14 that is 10 parts air to 1 part fuel. that is unless he is somehow reading the AFRs differently.

for the AFR to be going so lean when boost comes on then you may have a fuel pump issue or a fuel pressure regulator issue. my suggestion would be to forget the SAFC and get yourself a nistune (pretty sure they do them for the r34) and get that tuned. that will cost you less than a PFC, give you the same results and be much better than the SAFC. should cost you under $1000 for the nistune and to get it tuned (similar cost to a SAFC but will give much better gains than a SAFC).

as for the power you made and the behaviour of the boost, that really comes down to what mods you have. if you are still running stock exhaust, or only have a cat back exhaust and still have the stock cat and turbo to cat section of the exhaust then i would say that the power you made is about right, all things considered.

[robjay]

the air fuel ratio should be about 10 to 11 for a stock car, and if it has been tuned it should be about 12. 14 isn't richer than 10 or 11, it is leaner. the lower the number the more fuel there is as it is the AIR/FUEL ratio, so when saying 10 or 11 or 14 that is 10 parts air to 1 part fuel. that is unless he is somehow reading the AFRs differently.

for the AFR to be going so lean when boost comes on then you may have a fuel pump issue or a fuel pressure regulator issue. my suggestion would be to forget the SAFC and get yourself a nistune (pretty sure they do them for the r34) and get that tuned. that will cost you less than a PFC, give you the same results and be much better than the SAFC. should cost you under $1000 for the nistune and to get it tuned (similar cost to a SAFC but will give much better gains than a SAFC).

as for the power you made and the behaviour of the boost, that really comes down to what mods you have. if you are still running stock exhaust, or only have a cat back exhaust and still have the stock cat and turbo to cat section of the exhaust then i would say that the power you made is about right, all things considered.

is 14 too lean in this situation?

the actual data:

psi speed a/f lambda petrol

1.5 70 14.4 .99

1.5 80 14.4 .99

4.3 90 13.6 .93

6.2 100 11.9 .82

8.2 110 11.4 .78

8.3 120 10.9 .75

8.2 130 10.3 .70

8.0 140 10.2 .70

7.8 150 10.0 .69

7.6 160 10.0 .69

[mad082]

no that looks pretty right. the reason being that at light throttle the AFR's will actually be between 14 and 15, controlled by the o2 sensor and the ecu. once you put your foot down the ecu ignores the o2 sensor and reverts to it's mapping and there is where it runs richer.

in the case of your car, it is running rather rich up top and it would greatly benefit from some form of aftermarket ecu, be it a nistune or a SAFC or any other ecu or piggyback. the ideal afr you want is about 12:1 where as you are running as rich as 10:1 (which is common for stock ecu cars).

as for the power it made, what mods do you have? that will be a determining factor as to how good/bad your power is, but considering the boost pressure you were running it doesn't sound too far off what it should be.

[robjay]

no that looks pretty right. the reason being that at light throttle the AFR's will actually be between 14 and 15, controlled by the o2 sensor and the ecu. once you put your foot down the ecu ignores the o2 sensor and reverts to it's mapping and there is where it runs richer.

in the case of your car, it is running rather rich up top and it would greatly benefit from some form of aftermarket ecu, be it a nistune or a SAFC or any other ecu or piggyback. the ideal afr you want is about 12:1 where as you are running as rich as 10:1 (which is common for stock ecu cars).

as for the power it made, what mods do you have? that will be a determining factor as to how good/bad your power is, but considering the boost pressure you were running it doesn't sound too far off what it should be.

No mods at all.

[mad082]

in that case then the power you made is pretty much right. you have to remember that the 206kw they are rated at is at the flywheel and not at the wheels, so the power at the wheels will always be less.

throw on a full exhaust, wind the boost up to about 10psi and you should see that figure rise up to around 170 to 185kw. throw on a frount mount intercooler and raise the boost up to around 12psi and you should see about 190 to 200kw. add a tune on top of that and you should see a bit more again.