Nissan Skyline GTS4 RB20 INTAKE “TURBOCLUB RB AFM” Rebuild


1992 Nissan Skyline Hr32 GTS-4 AFM (Air Fuel Meter) Upgrade modification to suit high volume 550cc Mazda RX7 Injectors.


Modified Nissan Skyline HR32 GTs-4 RB20DET INTAKE AFM Rebuild!

Nissan Skyline GTS4
Complete RB20 INTAKE “TURBOCLUB RB AFM” High Flow Modification
MID 2004

Index Page

Click on the images below  to see a larger view

The main reason for this turbo AFM modification was that I wanted to fit larger RX7 550cc Injectors to the Nissan RB20DET Engine in my quest for 250AWKw, and not be restricted by the airflow limitations of the standard sized AFM. (Air Fuel Meter)

RB20DET – Single Turbo 2Ltr

4 Speed Automatic

RWD Bias until more grip needed then Front
Wheels engage.

_Nissan_RB20DET_AFM_01.jpg (63833 bytes)

Proven to WORK!!
Car completely drivable with 550cc Mazda
RX7 Injectors in place of the standard Nissan injectors.

MID2004 – In doubling the size of the metered
orifice area  that was the Original Nissan AFM I guestimated
that the increased size for a given RPM would
slow the airflow measured by the AFM so the
larger injectors would open less to keep the
Airfuel ratio roughly correct. Hopefully this
would be enough to be able to drive it to a Dyno
to get it properly tuned to suit all  the modifications so
it is 100% smog legal.

afm_1.jpg (53058 bytes)

afm_2.jpg (50453 bytes)

afm_10.jpg (51744 bytes)

afm_3.jpg (11502 bytes)
afm_4.jpg (15096 bytes)

This is how the AFM looked after cutting
up the plastic tubing surrounding the post
and electronics box and connector still
intact and ready to measure a lot lower
airspeed in the new larger orifice .

afm_11.jpg (51570 bytes)

afm_7.jpg (53081 bytes)

afm_5.jpg (51221 bytes)

Here you can see the original Intake Air Box
has been cut to remove the original AFM body
mounting and the hole extended to suit the
larger custom AFM assy. The new duct was
made from welded aluminum sheet formed to
suit the size required to double the
original with a rounded lip to smooth the
                             afm_12.jpg (53060 bytes)  afm_6.jpg (49954 bytes)

The AFM post assy then was refitted to
the new larger diameter tube in the same
position as original.

afm_15.jpg (58570 bytes)

afm_9.jpg (52501 bytes)
afm_8.jpg (53893 bytes)

Here you can see that I have had to reduce the pipe size back down to near the original but this is after the air flow has been measured by the meter so it does not matter.



JAN2005 “TURBOCLUB RB AFM” mod finished and
proven to work

– completed “TURBOCLUB AFM” insitu below..

_Nissan_RB20DET_AFM_05.jpg (50682 bytes)



_Nissan_RB20DET_AFM_01.jpg (63833 bytes)

_Nissan_RB20DET_AFM_02.jpg (55923 bytes)

_Nissan_RB20DET_AFM_03.jpg (62836 bytes)

_Nissan_RB20DET_AFM_04.jpg (37488 bytes)

Because I fooled the ECU with the 550 cc
injectors and the double size AFM I suspect
the ecu is giving incorrect timing.

Obviously I expected to have to re-tune the
ECU anyway to suit the fuel and air mods but
may have not realised the timing
implications.Well as mentioned I took the Nissan HR32
GTS4 to Dr Drift – Sam Cornell this morning
to see if we could sort out the bad noise
problems and generaly check over the entire
ECU etc.
As he is the only person that seems to
specialise in remapping the Nissan ECU in
Melbourne I was happy to only have to drive
20 klms instead of 1200 klms to Adelaide to
see Martin Donnon again just to tune the
Sam seems to know what he is on about and
said he would do a baseline run just to see
what was going on regarding my concerns on
the modified AFM I had created to allow the
Mazda RX7 550cc Injectors to work OK on the
Nissan Skyline RB20 turbo and at least be drivable to be able to
get it to a workshop to be tuned.


I have to say that in talking to Sam, (Dr
Drift) initially before taking the car over
to his workshop, he expressed some concerns
with the Mod AFM causing a problem with the
AF ratio and the fact it may be extremely
difficult to map the mod AFM to get good
stable AF ratio and it may be running lean.
Sam suggested that some of the 15yr old AFM
units are causing some problems and maybe
worthwhile to get a new Z model AFM that he
could easily map.

Well after running the RB20DET up on the
dyno he logged the AFR ( Air-Fuel-Ratio) at a steady 12.2

across the rev range! AFM Modification
PROVEN TO WORK with 550cc Injectors near
spot on. The timing needed a 2-3deg retard
but that was all on 13PSI the std gate non
bled pressure.

Admittedly the idle was a bit
ordinary, mainly ok but occasionaly
hesitating and near stalling but at least
fully drivable.

OK what was the RW-KW?? – DAMN only 106!

The problem is that the virtually brand new
$800 Soderstrom torque Converter is totaly
slipping all the way to 5000rpm and Sam
could not go any further until I get this
issue fixed!

I remember that Martin Donnon did say when
he tuned it at MorPowa up to about 180KW
that he suspected that the trans was
slipping then but I did not want to belive
it because I had recently spent $3000 on
getting it completely rebuilt and how could
it possibly be the problem?!?

On the return journey home to Victoria I
blew off one of the intercooler hoses
passing a truck and was able to fasten it
again without too much drama and I said to
myself “THATS why Martin could not get the
power up, it must have been loose and
leaking” – Stupid they did not check!

Glenn, (Turbine) suggested we drive over to
Street & Strip Automatics in Seaford where
he got the Jatco for the RB20DE+T Drag Car
built to talk to Alex about what to do to
sort it out.

Looks like I will have to book the GTS4 in
for a week or so for him to remove the
Soderstrom TCI 2700 Stall Torque Converter
to get sent away for rebuilding. As well I
intend to get the whole box disassembled to
be rechecked that all the expensive kevlar
clutches and bands are still OK after ONLY
less than 5000K’s of driving around reving
the car at no more than 3000RPM because of
the noise problem that no one seems to be
able to accurately identify.

I am starting to wonder if maybe the strange
noise is the bloody transmission as well!!

Well in hindsight I should have guessed that the noise was going to be bad!

It was the bigends knocking from lack of oil pressure from the oil pump that the screws were later found to be coming out of the internal backing plate of the oil pump. After the engine had completly almost ceased to run we pulled it down to find the reason why and could not believe that the oil pump could come apart so easily with all the screws loose and obviously leaking all pressure internaly into the sump.


'82 Mitsubishi Starion Turbo - 91 Mazda Familia Turbo AWD - 91 Nissan Skyline R32 AWD Turbo - 69 AMC Javelin 401 & GMC Supercharger - 72 AMC Javelin

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