Fueling Questions

[No Crust Racing]

Hi guys,

Car is a CA18 S13 and was running T25G 14psi, using SAFC II and stock fuel system - Made 164rwkw (sheets around if needed) at about 12-12.5 AFR.

Have recently fitted T28BB and intend on running around the same boost which will obviously be a lot more air flow. I had a quick play last night and couldn't get the AFRs anywhere near safe, at best it was 13.5 and that was only for a short period, it was averaging much higher with SAFC using maxed correction (I'm aware adding fuel retards timing costing response and power so bare with me). This is obviously far too lean.

As I have seen plenty of others take stock injectors up to and over 180rwkw, my assumption is that the pump can't keep up and that upgrading to something like a Walbro 255lph would give me a bump in fuel pressure/volume meaning more fuel in for a given Injector Pulse Width. (The item missing from my setup and other CA's using this turbo making more power is the pump for those still using stock injectors).

I realise I can upgrade to GT-R injectors also and reduce the duty cycle and this is part of the plan but at the moment I'm more interested in the fuel pump. Will adding the pump alone richen up the mix or will the stock fuel reg cancel out the increased fuel pressure? Do I also need an adjustable reg if adding a pump?

FYI I have a wideband in the car so I can see what's happening. I need to get some more fuel in "mechanically" if you get me so I don't need to use as much correction on the SAFC, the correction means more retarded timing which is costing me some response. I know I can go nistune/dr drift etc but atm I am staying with the SAFC.

Cheers

Edited January 5, 2012 by ActionDan

[GTSBoy]

A bigger fuel pump will definitely richen the mix, because what is probably happening now is the rail pressure is dropping below the desired pressure (which would be about 43+boost psi). If you can hold the pressure up, then more fuel will flow to the engine on the same injector pulse width.

Whether it's enough to solve your problem is a different story. An adjustable reg will allow you to add a few psi to the rail presure and gain some more headroom if you're desperate for it.

[No Crust Racing]

Well It's certainly a start and based on some other CA dyno results, is the missing part from my setup to those making 180-185rwkw on stock injectors (which would be getting replaced anyway as they are getting up into the 90% duty cycle range at that power).

Just keen to know if a reg is "needed" or if the pump is enough to deliver more fuel. Seems the pump should at least have "some" affect.

Edited January 5, 2012 by ActionDan

[rob82]

Never seen a STD ca18 with a good fuel system/afm be lean! Pump will fix your problem.

[chris_82]

Rather than starting a new post, Just a question relating to this, if i upgraded my turbo on my R33 to a kando or hyperflow etc, and wanted to run about 12-15 psi. Still running a stock ecu, fuel pump and injectors. would a SAFC be enough to compensate the new turbo or would i need an after market ecu. Is it only the AFR that needs to be adjusted.

[No Crust Racing]

As with any car using an SAFC, you will have to accept that it will be a compromise. It will not drive as well or produce as much power as a fully tuned car. The SAFC is just intercepting the AFM signal and making the ECU put in more fuel which means timing is retarded. In a daily driver that will result in poor fuel economy, not that it was ever good in an import, less power, slightly more lag, and slightly duller response in general (due to retarded timing) - and potentially higher EGTs if the timing is retarded so much that the burn is still going when the exhaust valves open.

I am happy to walk this path as the car gets driven 4-6 times a year and in anger everytime. You might want to consider going a Nistune/PFC/Some other fully tunable solution instead if you want the utmost power from the package, the best on road manners, and reliability.

If you can live with the above, and in the end we are only talking a 5-10% difference then an SAFC can be an OK work around but I wouldn't be fiddling with one unless you have access to a Dyno or a wideband (like I do).

[chris_82]

Yeah ok i get ya thanks. Have u decided what ur doing with urs yet, pump or reg or both.

[No Crust Racing]

I'm big on the whole proving a theory thing so I will go pump first, then test results, then decide what to do if anything further is needed (injectors most likely).

Forgot to add, R33 ECUs also have a lovely thing called rich and retard - when the AFM/ECU sees too much airflow it will dump fuel in and massivly retard timing, feels like the car massivly backs off by itself.

When that starts happening you're at the point of needing a proper tune.

CAs aren't smart enough for that

Edited January 6, 2012 by ActionDan

[femno]

CAs aren't smart enough for that

Are you sure about that?

[No Crust Racing]

Nope, just guessing based on having seen a bit on the timing tables which only seem to account for knock. Where as the R33 ECU dumps fuel and pulls timing to the point of a huge stutter in power delivery, CAs just seem to pull timing and dull response to a lesser degree. CAs run into power ceilings due to AFMs maxing out but don't go rich/retard in the same way that 33s seem to, maybe it's just how aggressively the ECU performs those actions that differs?

But I'm not tuner so feel free to share what you know with the rest of the class Matty

[GTSBoy]

The difference between the older ECUs (like CA, R32) and the newer ones (RB25s) with rich and retard behaviour is mainly in the amount. The stock maps on the later ones have a very rich and very retarded upper right corner of the map. So they are inherently rich and retarded - more so than the earlier ECUs' maps. But the early ones are still quite rich and not very advanced up there. The knock maps are the same, just more so.

So if you have an earlier ECU that is knocking, then it will switch to the knock map. If the knock continues, it will aggressively chop more timing out of it - which is a feature that is not mapped, it just happens. The R&R behaviour of the later ECUs is really an attempt to stop the engine from getting to the point of knocking in the first place.

Edited January 9, 2012 by GTSBoy

[No Crust Racing]

Good to know

Also, have a Walbro on the way.

[Rolls]

fork out for a nistune or aftermarket ECU once you fix the fueling problem, will give you a much nicer result.

[DVS JEZ]

Havent read all the posts but upgrade the pump and add a new power feed/ relay so the pump gets alternator voltage.

And a nistune as Rolls suggested

[DVS JEZ]

So if you have an earlier ECU that is knocking, then it will switch to the knock map. If the knock continues, it will aggressively chop more timing out of it - which is a feature that is not mapped

Have u tested this dude? Im curious how much it retards on top of the knock map

[Rolls]

So if you have an earlier ECU that is knocking, then it will switch to the knock map. If the knock continues, it will aggressively chop more timing out of it - which is a feature that is not mapped, it just happens.

Interesting, I wasn't aware that they did this.

[No Crust Racing]

Update to this.

Car is much angrier with the fuel pump in. I wound in some more boost ~16psi, wound in some more timing (as it was retarded) and took fuel OUT of the transition point as it was too rich, seems to hold 12.5 all the way through and wants to light up second coming onto boost just from rolling along and nailing throttle. Spool time seems the same, 15-16psi approx 4000rpm but it came on much harder tonight (might just be the cold air).

Was also thinking...what do people think I might make on this car with a Dr Drift Remap?

It made 164rwkw on a dyno dynamics at approx 13-14psi on a T25G using just the SAFC II and some retarded base timing.

The differences would be:

- Base Timing at 10 degrees and proper timing throughout due to remap

- Walbro fuel pump - installed

- T28BB at 15psi

I was under the impression that the T28 at 15psi would actually be flowing a lot more air than the 25G at roughly the same psi but I'm looking around dyno threads and seeing some people making 160rwkw with the above modes, some making 190rwkw.

I'd be annoyed if a bigger turbo with a touch more boost, better timing, and better fuel pump only got me 5-10rwkw. I was kind of hoping it would make 180-190rwkw (if I went ahead and got it remapped) or is that too ambitious on 15psi? I could push the turbo harder but not before adding injectors.

[GTSBoy]

Have u tested this dude? Im curious how much it retards on top of the knock map

Nah. It's not the sort of thing you want to test, pushing an engine into knock hard enough to trigger it. It's supposed to be real emergency business - like when it gets a tank full of wife spec petrol on a real hot day.

I can't even remember where/when I learnt about it. I think it was many years ago when I was considering going down the RomEdit path to tuning my ECU (but balked at the expense of buying all the kit needed). I read fairly widely (of what little was available in English!) on the topic. FWIW, I think it's not really different to the R&R behaviour of the R33 etc ECUs, just without so much fuel added.

[freyb]

got a r32 gts rb20det - pod filter, fmic blitz return flow, stock injectors and stock engine/turbo/ecu, boosting on .7 bar

changed my stock fuel pump last monday when it suddenly died while driving.

got a walbro 255 now

question - should i upgrade to a aftermarket fuel reg or injectors or safc?

[GTSBoy]

Um.....nearly everything on your engine is stock. So you won't need injectors, you won't need a reg, and I can't for the life of me think why anyone would want and SAFC. There are a bazzillion threads on here describing the way and sensible order to mod your RB20. Time to start reading.