489bhp on standard AFMs? - GT-R Register - Official Nissan Skyline and GTR Owners Club forum

Jim27 · 31st October 2005, 10:37 PM

General concensus is that the standard GT-R AFMs are max'd out at circa 420-450bhp.

I bought Matt Jeff's R33 RB26DETT that had been treated to the Middlehurst 500 upgrade. I got the job lot and basically whatever came out of Matt's engine bay came as part of the package.

The AFMs that Middlehurst use are the standard ones - 65mm internal diameter and the same code on the brown sticker as my OE R32 ones. Yet my own standard R32 AFMs were retained and when RK fitted the engine and got it mapped he managed to get 489bhp & 450lb/ft of torque whilst still using the standard AFMs. That was at 1.3 bar, albeit having to use octane booster.

I've just got my new fuel pump (Bosch 044) and have some nice clean filters on the way before sending the car for a remap. Just wondering whether or not I'll need to spunk another few hundred squids on uprated AFMs, and if so, which ones?

Jim
(so much for a cheap Xmas....)

NikWilson · 31st October 2005, 11:52 PM

Looks like you will need some Nismo AFM's. Same diameter as standard so no need to repalce your fittings. Some new ones for sale on Flea bay from Middlehurst.

Nik

NissanBoy · 1st November 2005, 10:57 PM

Z32 maf's is what you need, you will need to change the info in the ecu to have them work, I guess you are running a pfc or the like so it should be straight forward.

Jim27 · 2nd November 2005, 08:24 AM

Yes- PFC.

I had a chat to Andy Middlehurst yesterday, as it was Middlehurst that originally did the 500bhp upgrade.

He told me that the standard AFMs are retaining for 500bhp as they can handle the level of air flow required. Going much further upwards from 500 (e.g. 550+) necessitates Nismo AFMs but the OE ones should be perfectly fine for supporting 500bhp...

Pikey · 2nd November 2005, 09:27 AM

Dont buy the Z32 ones unless you then want to spend another £400 on the Apexi induction kit to mate to them, as they're bigger diameter.

Jim27 · 2nd November 2005, 10:44 AM

Good point Pikey

Hedgehog Dodger · 6th November 2005, 08:57 AM

I am a total newbie when in comes to RB26, but I have modified the 3S-GTE for about 4 years now.

Am I right in thinking that the upgrade consisted of Middlehurst using some kind of aftermarket ECU - Apexi Power FC or HKS F-Con Pro?

Therefore wouldnt these ECU's use a MAP sensor and get rid of the need for AFM's?

matt j · 6th November 2005, 11:39 AM

Quote:

Originally Posted by Hedgehog Dodger

Am I right in thinking that the upgrade consisted of Middlehurst using some kind of aftermarket ECU - Apexi Power FC or HKS F-Con Pro?

Standard ecu with upgraded chip - not an aftermarket unit.

Matt.

Hedgehog Dodger · 6th November 2005, 02:38 PM

Quote:

Originally Posted by matt j

Standard ecu with upgraded chip - not an aftermarket unit.

Matt.

kingsley · 9th November 2005, 12:18 AM

Not ignoring what's already been said in this thread, it's worth mentioning that it is possible to get a bit more power from an engine than the AFMs will read though your mapping might not be very accurate at the top end.

For example, if your AFMs max out at, say, 6500rpm and beyond that don't register any more air flow, under the simplest circumstances you'd expect the mixture to start getting leaner from that point. If you were running excessively rich at 6500rpm then at (say) 7000rpm the mixture might have leaned out to a better value and consequently allow you to make a bit more power than the AFM's metering max.

Some aftermarket ECUs may (total guess) allow you to program in a richer mixture at high rpm where the AFMs are maxxed out. This might serve to compensate (approximately) and keep the mixture more or less right. It's not going to be very accurate but it's better than nothing. Obviously, it's better to have AFMs that meter the flow properly.

31st October 2005, 10:37 PM	#1 (permalink)
Jim27 GTR Register Member Join Date: Jul 2004 Location: Bolton Posts: 4,478	489bhp on standard AFMs? General concensus is that the standard GT-R AFMs are max'd out at circa 420-450bhp. I bought Matt Jeff's R33 RB26DETT that had been treated to the Middlehurst 500 upgrade. I got the job lot and basically whatever came out of Matt's engine bay came as part of the package. The AFMs that Middlehurst use are the standard ones - 65mm internal diameter and the same code on the brown sticker as my OE R32 ones. Yet my own standard R32 AFMs were retained and when RK fitted the engine and got it mapped he managed to get 489bhp & 450lb/ft of torque whilst still using the standard AFMs. That was at 1.3 bar, albeit having to use octane booster. I've just got my new fuel pump (Bosch 044) and have some nice clean filters on the way before sending the car for a remap. Just wondering whether or not I'll need to spunk another few hundred squids on uprated AFMs, and if so, which ones? Jim (so much for a cheap Xmas....)

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31st October 2005, 11:52 PM	#2 (permalink)
NikWilson GTR Register Member Join Date: Oct 2002 Location: East Dereham, Norfolk. UK Posts: 933	Looks like you will need some Nismo AFM's. Same diameter as standard so no need to repalce your fittings. Some new ones for sale on Flea bay from Middlehurst. Nik

1st November 2005, 10:57 PM	#3 (permalink)
NissanBoy GTR Register Member Join Date: Jul 2005 Location: NW London Posts: 179	Z32 maf's is what you need, you will need to change the info in the ecu to have them work, I guess you are running a pfc or the like so it should be straight forward.

2nd November 2005, 08:24 AM	#4 (permalink)
Jim27 GTR Register Member Join Date: Jul 2004 Location: Bolton Posts: 4,478	Yes- PFC. I had a chat to Andy Middlehurst yesterday, as it was Middlehurst that originally did the 500bhp upgrade. He told me that the standard AFMs are retaining for 500bhp as they can handle the level of air flow required. Going much further upwards from 500 (e.g. 550+) necessitates Nismo AFMs but the OE ones should be perfectly fine for supporting 500bhp...

2nd November 2005, 09:27 AM	#5 (permalink)
Pikey GTR Register Member Join Date: Feb 2004 Location: Cheltenham Posts: 4,151	Dont buy the Z32 ones unless you then want to spend another £400 on the Apexi induction kit to mate to them, as they're bigger diameter.

2nd November 2005, 10:44 AM	#6 (permalink)
Jim27 GTR Register Member Join Date: Jul 2004 Location: Bolton Posts: 4,478	Good point Pikey

6th November 2005, 08:57 AM	#7 (permalink)
Hedgehog Dodger GTR Register Member Join Date: Jul 2004 Location: Warrington Posts: 951	I am a total newbie when in comes to RB26, but I have modified the 3S-GTE for about 4 years now. Am I right in thinking that the upgrade consisted of Middlehurst using some kind of aftermarket ECU - Apexi Power FC or HKS F-Con Pro? Therefore wouldnt these ECU's use a MAP sensor and get rid of the need for AFM's?

9th November 2005, 12:18 AM	#10 (permalink)
kingsley GTR Register Member Join Date: Aug 2002 Location: West Surrey Posts: 1,801	Not ignoring what's already been said in this thread, it's worth mentioning that it is possible to get a bit more power from an engine than the AFMs will read though your mapping might not be very accurate at the top end. For example, if your AFMs max out at, say, 6500rpm and beyond that don't register any more air flow, under the simplest circumstances you'd expect the mixture to start getting leaner from that point. If you were running excessively rich at 6500rpm then at (say) 7000rpm the mixture might have leaned out to a better value and consequently allow you to make a bit more power than the AFM's metering max. Some aftermarket ECUs may (total guess) allow you to program in a richer mixture at high rpm where the AFMs are maxxed out. This might serve to compensate (approximately) and keep the mixture more or less right. It's not going to be very accurate but it's better than nothing. Obviously, it's better to have AFMs that meter the flow properly.