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Tuning Around Stock Gtr Afms/injector Limits


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Firstly, I know there has been discussion about this in the past and ive read a number of threads but seeking input and opinions from those that have done it or seen it first hand coz im sitting on the fence here...

Heres the basics of my situation -

Cars a 32 GTR, before I bought it, made 270rwkw on 1 bar with -7s, PFC, Forged motor, Tomei Fuel pump, stock Injectors/AFMs and an SX Pressure Reg.

Ive since added some small Tomei cams and am now ready for a tune and somewhere around 18psi.

I bought some Siemens 740cc Injectors ages ago (can sell easy enough) but am wondering whether is it really worth doing Injectors and Z32 AFMs with these turbos?

Is is realistic and more importantly safe enough to squeeze the stock injectors and AFMs to the limits of the -7s? My tuner mentioned he can 'tune around' the stock AFMs to an extent...

I figure with the cams and 18psi it MIGHT make 300rwkw ish?

What would you do?...Im at a point where im trying not to spend on it so if I can retain stock AFMs and Injectors with the SX reg and make close enough to 300rwkw i'd prefer to!

Thoughts?

Cheers.

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I made 340rwkw with stock injectors/AFMs

Obviously there was a fair bit more rail pressure, and tuned well past the AFM's limits...

The car came like that, so for safetys sake i put in 700's

300 wont be a problem though. One thing would be get the injectors flow tested/cleaned before doing it.

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i think it comes down to how reliable you want your car. if your tuner can tune around the AFM's thats fine - lots do. but on stock injectors you'd be running close to, if not on 100% duty cycle. you would be leaving a very small margin of error so things are more likely to go wrong.

personally, 85-90% duty cycle is the most i'd go at peak boost/power. you'd be well over that, most of your usable power will be in the 90-100% duty cycle range.

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IMO you could make a little more than 270 with that combo as is. First thing to check is the exhaust.

AFMs you can tune past with an element of risk, injectors are risky near 100% and fatal over 100%.

Also clean injectors flow far more than dirty ones. There was a recent thread showing injector that were flowing evenly, but flowed 20% more after they were cleaned. So, as well as rail pressure and AFR, injector cleanliness will determine how far you can get on the stockers. If they're leaking already its a no-brainer - replace them.

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Cool, so you kept stocko AFMs @340rwkw Nismoid?

And MrStab, what Injectors/AFMs are you using to make 305rwkw? Stockers?

The existing Injectors arent leaking and im pretty sure theres a receipt in the pile that came with the car for having them cleaned/flowed but would do again to be safe...

But based on above, I think i'll whack the 740s I have in there and work with the stock AFMs...seems theyre 'less' of a safety issue than the injectors, as long as tuner is capable enough of working around them.

Cheers.

Edited by NSNPWR
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Cool, so you kept stocko AFMs @340rwkw Nismoid?

And MrStab, what Injectors/AFMs are you using to make 305rwkw? Stockers?

The existing Injectors arent leaking and im pretty sure theres a receipt in the pile that came with the car for having them cleaned/flowed but would do again to be safe...

But based on above, I think i'll whack the 740s I have in there and work with the stock AFMs...seems theyre 'less' of a safety issue than the injectors, as long as tuner is capable enough of working around them.

Cheers.

Yes they were stock.

I did put Nismos/injectors in after i purchased it.

Car ran fine like that for 2 years however under previous owner.

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And MrStab, what Injectors/AFMs are you using to make 305rwkw? Stockers?

Injectors are seimens 550's, but they were originally bought to replace leaking stockers before i got the -7s. AFMs are stock, so I assume they're out of resolution at full torque. In this case the tune should be extra rich in the map areas where AFMs are maxed so the engine wont lean out on a cold day (cold air = more air mass, which means it also needs more fuel, but the ECU has no way of knowing that). When the AFMs are maxed the ECU is just estimating fuel delivery based on RPM. I'm probably going to get nismo AFMs before i push it to 320-330.

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The tuner should be allowing for and checking this on the dyno then, yeah?

You think the -7s will go 320-330? You mentioned exhaust, im running ceramic coated HKS split dumps into an unknown brand front pipe, into a big metal cat into a 3" pipe with one muffler right up the back...again, for the outlay, is a 3.5 worth the $$$? A few years ago ive had not been worried and just spent the $$$ but Mortgages etc change priorities!...

Edited by NSNPWR
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The tuner should be allowing for and checking this on the dyno then, yeah?

Yeah, but it cant hurt to specifically ask him to do it.

You think the -7s will go 320-330? You mentioned exhaust, im running ceramic coated HKS split dumps into an unknown brand front pipe, into a big metal cat into a 3" pipe with one muffler right up the back...again, for the outlay, is a 3.5 worth the $$$? A few years ago ive had not been worried and just spent the $$$ but Mortgages etc change priorities!...

I think 330 is possible given the current power and boost level, but I wont know until I try. I probably need a stronger clutch, and if i'm taking the gearbox out I should do something about the noisy input shaft bearing.... so i'm putting it off for a while.

Re exhaust, get the tuner to drop it at the front pipe to see if its an issue or not.

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Cheers. Not exactly sure of clutch in mine, some cushion button thing with a billet flywheel according to receipt...hopefully holds up.

Should a full weight 32 GTR trap around 120mph with 300rwkw and a good launch? Or more? I'd like to think it would do that easy...

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Buy a pair of rb20 afm's- they're direct plug in into the stock loom and will give you enough resolution for 380-400rwkw as well as being cheap. They're the same size as Z32's just half the price and no need to change the plugs.

You have injectors already... so why take the chance? Or sell them/swap them for smaller 550's.

I find it a little silly to take the chance at wrecking an engine for the sake of lazyness?

Cheers

Justin

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Lol @ cheapskate...Running PFC, thanks for the tip mate, 20/25 AFMs arent exactly in abundance from browsing the forums?...

Like I said, im trying not to spend on it, nothing to do with being a cheapskate, have burnt plenty of cash on this and previous cars.

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Lol @ cheapskate...Running PFC, thanks for the tip mate, 20/25 AFMs arent exactly in abundance from browsing the forums?...

Like I said, im trying not to spend on it, nothing to do with being a cheapskate, have burnt plenty of cash on this and previous cars.

Should be plenty around form people upgrading to Z32, Link/Vipec etc.

Plenty in NZ - have a look thruigh these ( I could probably get you a couple or three cheap and post them to you if you can't buy direct):

http://www.trademe.c...rch_suggested=0

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Lol @ cheapskate...Running PFC, thanks for the tip mate, 20/25 AFMs arent exactly in abundance from browsing the forums?...

Like I said, im trying not to spend on it, nothing to do with being a cheapskate, have burnt plenty of cash on this and previous cars.

300 for a pair from any import parts wreckers???

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Lol @ cheapskate...Running PFC, thanks for the tip mate, 20/25 AFMs arent exactly in abundance from browsing the forums?...

Like I said, im trying not to spend on it, nothing to do with being a cheapskate, have burnt plenty of cash on this and previous cars.

Just remember they are still 2nd hand.

You could burn $300 on a 2nd hand set and then have them die on you a week later :/

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