Maxed AFM, and other questions

[hayes_666]

Hi There,

My r32 gts-t rb20 engined skyline reaches 96% airflow (reading from my Apexi s-afc) through the afm on a cool day at only 9 psi boost.

I have:

Gtr exhaust Mandifolds.

Twin Garret T2 turbos (internal wastegates)

Gtr front mount intercooler

Hks air filter

twin 2 1/4inch down pipes - 3 inch pipe

3 inch decat

4inch gtr exhaust system (stainless belived veilside)

uprated/modfied standard blow off valve.

Apexi s-afc (blue screen)

The car uses standard injectors, air flow meter and ecu

I have no air leaks and no more than 9 psi boost, but still read 96% air flow have seen 100% in exceptional sercomstances (spelling ).

I have a air/fuel ratio meter from auto gauges and that shows no excessive fueling, i also have a flammer kit on the car which takes a little hamering to get to flame, so belive that the mixtures are fine.

So whats next?????.

Will try for gtr fuel pump and injetors, But what afm, i have thought about twin gtr afm's as the apexi unit can do that.

Would this work?????,

If i have maxed my afm then my injectors must be near max and as she isnt over fueling.

What sort of bhp am i running????

If my engine is safe to around 1.2bar standard

What sort of bhp do you think i should see???.

Sorry for all the questions but i love to play with my linner buti love to cheack up on things before i do them.

Thanks

Nathan

[Busky2k]

I suggest you dont turn up the boost anymore than what you ahve it set at. Once you go past 100% the AFM cant measure any more air so this can result in a severe lean out, or a fuel cut. I suggest you go to a dyno ASAP.

ALso think about getting a Z32 AFM and a PowerFC.

[hayes_666]

Hehe i have seen 100% and it isnt nice the engine just cuts out, :Bang: , would the gtr fuel pump, injectors and afm's help a bit.???.

Thanks

Nathan

[FATGTS-R]

Is a standard RB20 ecu even going to work with two afms?

[Bl4cK32]

Hehe i have seen 100% and it isnt nice the engine just cuts out, :Bang: , would the gtr fuel pump, injectors and afm's help a bit.???.

Thanks

Nathan

Please explain why most people laugh at 100% duty cyle or their afm maxxes out?

Id be more worried about blowing the motor than tight arsing when it comes to mods. Surely you must have thought at some point fuel and airflow must be maxxed out, so why leave it till the last minute when the motor is border line to decide whether or not to upgrade?

Having just gone through 12 months of a full rebuild, spending big $$, its not fun with no car.

Get a z32, larger injectors (rx7 ser 5 drop ins) and a power fc.

Dont say you cant afford to stretch it if youve obviously planned to go this far, if not further....

[hayes_666]

I Laugh as it was such a surprise to run out of air flow on only 9psi boost when the engine was running 11psi before, the only reason i went to twin turbos was the price,it was cheaper for me to do this than upgrade to a large single with steel internals over here,

all i wanted to do was run just over 1bar boost which i was assured the standard setup could do, but now knowing that the twin turbos max the whole system out with only 9psi was kind of a shock, and it left me with a whole load of diffrent routes to o down now.

I will try to get gtr injectors, gtr fuel pump, and gtr afm's as i would belive that this may be a good match as it works on the gtr ok, the trouble i have is that nobody in the uk has ever done what i havedone on the rb20 engine, over here the gtr is king and thats it why nobody realy bothers tuning the gts-t, i kind of hoped that somebody on here has done what i have done andcan tell me the best way to over come thease problems,

Sadly it looks like i am on my own and haveto try to make the best decisions and to not waste to much money on wrong ones.

Fatgts-r, The rb20ecu wont run twin afm's as is but the Apexi s-afc has a clever little trick that allows it to read two Afm's and combine the outputs to give a single output that the rb20 ecu can read the two into one pipe set up i have to draw air through the one afm is a large unit so to run two will give me more space and a better inlet flow as well.

Thanks

Nathan

[Sydneykid]

Hi There, My r32 gts-t rb20 engined skyline reaches 96% airflow (reading from my Apexi s-afc)  through the afm on a cool day at only 9 psi boost. I have:

Gtr exhaust Mandifolds.

Twin Garret T2 turbos (internal wastegates)

Gtr front mount intercooler

Hks air filter

twin 2 1/4inch down pipes - 3 inch pipe

3 inch decat

4inch gtr exhaust system (stainless belived veilside)

uprated/modfied standard blow off valve.

Apexi s-afc (blue screen)

The car uses standard injectors, air flow meter and ecu

1. I have no air leaks and no more than 9 psi boost, but still read 96% air flow have seen 100% in exceptional sercomstances (spelling ).

I have a air/fuel ratio meter from auto gauges and that shows no excessive fueling, i also have a flammer kit on the car which takes a little hamering to get to flame, so belive that the mixtures are fine. So whats next?????.

2. Will try for gtr fuel pump and injetors, But what afm, i have thought about twin gtr afm's as the apexi unit can do that. Would this work?????,

3. If i have maxed my afm then my injectors must be near max and as she isnt over fueling.  What sort of bhp am i running????

4. If my engine is safe to around 1.2bar standard  

5. What sort of bhp do you think i should see???.

Sorry for all the questions but i love to play with my linner buti love to cheack up on things before i do them.

Thanks            Nathan

Hi Nathan lots of questions, my suggestions follow;

1. Number 1 thing to remember is boost is irrelevant, airflow makes horsepower. Boost is a measure of resistance to airflow. I can have a turbo (or twins) that make 40 lbs per minute of airflow at 1 bar. I can also have another turbo (or twins) that make 30 lbs per minute at 1 bar. Number 2 thing to remember, the AFM measures the airflow into the turbo/s, not the boost out of it/them.

I am not familiar with the "air/fuel ratio meter from auto gauges" but what I can say is if it uses the standard lambda sensor, then it is pretty much useless. It is what I call "slow and narrow". It only measures A/F ratios over a very narrow band and its response to changes in A/F ratio is very slow. So slow in fact that you can have heaps of lean spots while accelerating that go past too quick and the meter never shows them. If you are going to tune your car properly you need a "fast and wide" lambda sensor. That's what dyno shops use.

2. You can use twin AFM's or a single, since you have twin turbos it is probably easier (and more efficient) to plumb two AFM's. I would use two RB20 AFM's (80 mm) just in case one day you get over the limit of twin GTR (65 mm) AFM's. Plus you only have to buy one (cheap) RB20 AFM.

3. Not necessarily, but pretty likely. Standard RB20 injectors usually run out of flow at around 350 bhp depending on how solid the fuel pressure is.

4. As is said above boost is irrelevant, it's power (combustion pressure), rpm and poor tuning that kills engines.

5. There is no reason why you shouldn’t get the same power using GTR sized turbos as a GTR does. At 2 litres versus 2.6 litres it will be a bit more peaky and laggy though. Around 450 bhp is my rule of thumb limit for a standard internals RB20. You would of course have to do a few more things before the rest of the upgrades matches the turbos. Power FC or equivalent ECU upgrade would be on the list, as would cams, injectors and fuel pump.

My suggestions for the next steps.

#1 GTR fuel pump

#2 Adj fuel pressure regulator, Nismo have one that fits on the standard RB20 fuel rail (replaces the standard FPR), Nengun sell them for ~$A150 (=not many Euros). You can sneak around 10% more fuel flow by increasing the rail pressure. I don’t recommend going any further than that.

#3 96% on the AFM's is not an issue, upgrade when you get to 100%. I'd check the voltage wiht a multimeter first though, max is 5.1 volts. I have seen SAFC's record 4 volts as 90%, obviously not correct.

#4 GTR injectors, you will need a resistor pack as well, to match the impedance for the GTST ECU.

Hope that helps

[hayes_666]

Thanks Sidneykid,

That makes alot of sense, ,

Themain reason i was going to use gtr afm's is that i would have thought (could be wrong) that nissan would have matched the system up as well as the rb20 setup if you get what i mean so that there would be less of a miss match requireing more tuning, if i went upto 550cc injectors then two rb20 afm's would be better at a guess, touble is i have seen twin gtr afm's for the same price as one rb20 one, due to more people upgrading gtr's than gts's,

But anyway what you have said will help greatly thankyou.

Thanks

Nathan

[pnblight]

ha just a suggestion would it be posible to run a gtr ecu on this car as he has the same crank angle sensor ,and will have soon two afms and gtr injectors .he could most like pick up r32 pretty cheap and they are reprogrammable yeah

[lazza]

Nathan, what is a flammer kit???

It sounds like something I need to have.

Lawrence

[hayes_666]

I did ask the question on the uk skyline sites about the use of a gtr ecu, as in why can i not use it?, obviously the big problem is the inlet manifolds throtle set up , but i guess that the gtr still only has one TPS on it?.

A flammer kit is a very crude method of creating flames from your car, it is simply pulse circuit using a 555 timer chip, it then powers a basic HT coil, which inturn creates a near continous spark on the spark plug you have to fit in the exhaust.

It will then ignite any unburnt fuel in the exhaust creating some mental flames on overrun, and between gear changes.

Some of the guys here are using butane kits that flame when ever you want (very similar to 2f2f).

Nathan

[aybee]

sounds like you need to buy my Power FC...

and maybe even my AFM

[hayes_666]

Would all depend on price of the apexi power fc?.

Nathan

[TurkeySlapper]

man i'm going to flamed for this. I know that SAFC's are no way near good enough get a power fc blah blah blah but cos thats not an option atm $$ wise would it be possible to use a Z32 AFM on a stock RB25 with an SAFC2? Cos mine reads up to 100% all the time and the engine has a very annoying cutout/detonation at high revs occasionally. I only ask this cos the SAFC manual says that you can specify an "in" and "out" type of AFM reading, as in it can convert a Z32 afm reading into a RB25 reading, or thats what i gathered. Bit of a dodgy bandaid solution ive been pondering.

[hayes_666]

No you will still have to set it up as it will read less air flow when there is more i guess, so you will run very week, (again i guess) so you would have to uprate the fueling as well.

Nathan

[Sydneykid]

man i'm going to flamed for this. I know that SAFC's are no way near good enough get a power fc blah blah blah but cos thats not an option atm $$ wise would it be possible to use a Z32 AFM on a stock RB25 with an SAFC2? Cos mine reads up to 100% all the time and the engine has a very annoying cutout/detonation at high revs occasionally. I only ask this cos the SAFC manual says that you can specify an "in" and "out" type of AFM reading, as in it can convert a Z32 afm reading into a RB25 reading, or thats what i gathered. Bit of a dodgy bandaid solution ive been pondering.

The SAFC 11's can handle different voltage ramps from AFM's, it is a little tricky to set up and tune. But it does work OK, within the limits of SAFC tuning of course. I have seen a car running a Q45 AFM with an SAFC quite well, but that was a bitch at low airflows apparently. A Z32 AFM should be a lot easier.

Bottom line, if you are TRULY maxing out the R33 GTST AFM, as in 5.1 volts for long periods through the RPM range, then your upgrade is way past where I would no longer recommend an SAFC. You have no control of ignition timing, in fact by using the SAFC to control fuel you are just making the igntion timing problem worse. What is cheaper $900 for a Power FC or $4,000 for an engine out and rebuild?

It's your call

[hayes_666]

Dont hks do a piggyback ignition controller?.

Nathan