jvallo7

why can a n338 n/a vert ecu be used in a turbo car [so ive been told] what makes the vert ecu diff from other n/a ecus??

misterstyx69

iTrader: (142)

you need to look at the archives ..
the thread was staring you in the face about ten threads down.
INFO:N326 - 86-87 NA
N332 - 87 Turbo
N327 - 88 NA
N333 - 88 Turbo
N338 - 88 Vert
N350 - 89 NA California
N351 - 89 NA
N352 - 89 Vert California
N353 - 89 Vert
N370 - 89 Turbo

MrGoodnight

iTrader: (1)

I think he is wanting to know why the vert doubles as NA/turbo ecu while others are one or the other.

Not which ecu is turbo/NA.

2slow4stock

iTrader: (18)

Because in Japan the vert didn't come n/a... There is a thread specifically about this ecu. I have ran the vert ecu on a turbo set up no problem in the past before as well.

jharris2188

iTrader: (1)

This forum can be difficult to search and find what you are looking for. I use something like this in Google:

site:rx7club.com 2nd Generation Specific (1986-1992) what i want to find here

site:rx7club.com 2nd Generation Specific (1986-1992) vert ecu on a turbo setup

Makes life easier; if I can't find it within 30-60 minutes then I look at starting a thread.

EDIT: You will find a lot of other relative information so if you start reading other posts I wouldn't count that in your 30-60 minute window

misterstyx69

iTrader: (142)

After taking out my James bond decoder ring it looks that way.

KompressorLOgic

iTrader: (6)

I remember a few threads on this way back in the day...
but never seemed to get any solid answers as to why it works....
its got me interested in it again as well!

how does the ecu tell which motor is hooked up how does it know which boost sensor is pluged in?

could there be some 1 wire difference that toggles something in the ecu?
man when I owned an 88 vert perhaps I should of looked more closly at some of it.

Akagis_white_comet

iTrader: (4)

Actually, I don't believe we've actually gotten to the bottom of why the 88 Vert ECU is capable of running a TII properly.

My understanding of the system is as follows:
N30x: Pre-FC 13B EFI engines (GSL-SE, HB Cosmo, etc)
N31x: J-spec S4 Turbo (Coupe AND Vert)
N32x: Euro/North America S4 NA (N322/N323 for Euro, because of distributor)
N33x: North American S4 Turbo (Including 1988 Vert)
N34x: Euro S4 Turbo
N35x: North American S5 NA
N36x: Not Used, intended for Euro S5 NA
N37x: North American/J-spec S5 Turbo
N38x: Euro S5 Turbo
N39x: *J-spec S5-Kai Twin Turbo (JC Cosmo only)*
*The reason why I say it is S5-Kai (Japanese for "Modified") is that the N370 and N3A1 ECUs are VERY similar in their pinouts. The N390 would logically be even closer to the N37x due to being developed before the N3Ax.

N3Ax: North American/J-spec FD S6 Twin Turbo, 8-bit ECU (1993 North America FDs, J-spec up to 11/95)
N3B1/3: **North American S5 NA Vert (1992 only)**
N3B7: Euro FD S6 Twin Turbo (1/92 to 7/93)
N3Cx: Revised North America FD S6 Twin Turbo, 8-bit ECU (1994 North American FDs)
N3Dx: Revised Euro/North America FD S6 Twin Turbo, 8-bit ECU (8/93 to EOP for Europe, 1995 for North America)
N3Ex: Revised California FD S6 8-bit ECU (1995 only)
N3Fx: FD S7 Twin Turbo, 16-bit ECU (12/95 to 11/98)
N3Gx: FD S8 Twin Turbo, 16-bit ECU (12/98 to EOP)

**I've never actually seen the N3B1/B3 ECU before, but it is in the Parts Catalog for 1992. My hypothesis is that Mazda ran out of N35x ECUs and had to modify some N3A1's for use in the final run of S5 verts, hence the N3B1/B3 prefixes.

Would be nice to see what's under the cover of each ECU...

j9fd3s

iTrader: (3)

the parts catalog shows that the JDM s4 vert ECU is an N341....

RotaryEvolution

iTrader: (30)

i'm wondering if in actuality all n/a ECUs are in reality capable of running a turbo. i have never actually tried it though.

the question is what happens when it sees positive pressure on the pressure sensor and what it does to correct timing, and plugging in a turbo pressure sensor the same questions applied. the airflow meter can be worked around to supply enough fuel for both turbo and n/a applications because the AFM can't tell the ECU if there is positive pressure or not going into the engine.

so the pressure sensor output is the only real difference in the coding of the ECU and what it does to correct for that reading or if it simply just cuts fuel when it reaches a certain amount of positive pressure. i have seen n/a ECUs interpret 2psi of positive pressure on naturally aspirated engines before and there was no fuel cut(s5 n/a coupe N350).

i was thinking of just trying it and finding out, since i'm in the process of doing a S5 turbo vert. would save me some headache moving things around.

if it works it would surely make life simple for the n/a>turbo conversions, especially once i get this 6 port turbo conversion LIM ironed out. but for some reason i can't foresee them making maps for boost beyond a few PSI of resonant pressure so i'm skeptical that it does work or if it is mapped it is probably very rough.

j9fd3s

iTrader: (3)

well we've seen the NA and T2 timing map for the turbo, and the turbo is actually more aggressive.

the AFM, doesn't care if you hook it to a turbo or not, but the NA and T2 AFM's are only going to read to a certain airflow, we have the charts for the Cosmo AFM's and we know what the S4 T2 will read up to, in terms of airflow.

it does seem that aside from timing the ECU maps are pretty similar, and most of what they did was use a larger scaled AFM and injectors

bumpstart

they may only read to a certain output but the scale 0-5V is also spread over that value
the turbo AFM spreads 0-5V over a much wider spread of airflows
.. so adding the NA afm will make the turbo ecu see full signal ( and will look up the tables to add full fuel ) at much lower airflows

... a car that runs sick rich before it runs out of ability to compensate and gradually leans up up top

RotaryEvolution

iTrader: (30)

but the question is at what power level does the non turbo AFM start to read inaccurately, like will a stock turbo at below 10 psi still compensate.

we do know that the non turbo AFM maxes out a bit before the turbo AFM will. ballpark i would say the turbo AFM can read up to 350-400whp(of course the injectors will not support it but the airflow of the meter does still read that high), the on turbo 225-250whp?

FelixIsGod29X

iTrader: (50)

Sooooo is it that only the S4 vert ecu is capable of being using in a stock TII swap or can a USDM S5 vert ecu be used in a TII swap as well? Pretty sure its no but still worth asking.

j9fd3s

iTrader: (3)

the JDM vert ecu is an N341, so its different from the JDM coupe and different from the US vert. the fact that the US ecu works is a testament to how reliable the rotary is...

bumpstart

uummmm .. you all do know that jap verts are in fact turbo.. but not in the US or aus delivered versions??

j9fd3s

iTrader: (3)

https://www.rx7club.com/2nd-generati...mo-afm-961741/

bumpstart

and PS.. the n340 ecu,, is the euro one .. their first with a CAS and ( we hope ) the 5 V signal system .. lacks the set couple in the wiring harness

would wonder if the N341 is wired up same ??

am wondering if all this hear say is just confusing the jap vert ECU with the us and oz ones
( which is for a turbo and thus will work and if a variant of n340..is missing lots of stuff like AWS etc which should make the swap simpler and more likely to work as lacks lots of interlocks .. )

j9fd3s

iTrader: (3)

MAZDA

look em up! the euro S4 is N322.

the 88 JDM coupe is N340, the 88 vert is N341

bumpstart

nopes.. sorry ..i have seen them in the flesh and had to trouble shoot a few
.. how do you think i know about the set couple

... n322 is euro NA,, with a dizzy,, with butterflies for aux switching,,,

and - N340 is turbo euro .. now with a CAS ( yay for them ) .. ,, with a non adjustable BACv
.............. they turn up here now and then in oz ( suspect english origin ) and prove to be a pain in *** as are such an odd man out.......
they are definitely a NON AWS ecu for LHD.. and that doesn't just mean japan..england in europe looks like the obvious other contender as LHD no AWS
suggest a ring around of the UK owners to see whats on the ecu.........

PS.. linky above .. is in greek .. so what is it i can check ???

j9fd3s

iTrader: (3)

you're right the N322 is the euro NA, N344 is the euro T2

N340 is the 88 JDM

Customisbetter

So if you hypothetically bolded a turbo to an 88 vert, Would you put the AFM in front of the turbo or behind in the pressure zone?

gregs22

iTrader: (12)

I have a N340 from a front clip that came from japan.

bumpstart

its always in front.. the point is each ECU has a look up table.. for 0-5V from the AFM
if you whack the wrong ecu on the wrong AFM then the ecu will be getting a mass flow signal.. and looking up its table to add fuel to that and that is all out of whack

its not just as simple it will hit X flow and have no more correction... the NA afm will make the turbo car run rich everywhere


whilst the NA sees say ( theoretically,, for examples sake .. 400 CFM ).. it outputs perhaps nearly max signal .. lets say 4.5 V
added to a turbo ecu.. which is expecting 4.5V to be closer to 700 CFM .. and adds 700 CFM air's correct amount of petrol .. to 400 cfm .. result = rich as hell

there is no way around this ( but one ) .. an ECU that is instead tweaked to maybe ignore the AFM flow result.. but instead use the AFM air temp.. the inlet pipe air temp.. and the map sensor signal to do a different type of mass flow calulation

so.. for our supposedly NA vert ECU to work on a turbo..... then it must be modded thus ( and have the correct map sensor it was set up for ) .. OR have the correct AFM fitted up with the ecu

the only plausible scenario there is that the NA vert ecu is somehow a map not maf version.. and if it works with the NA map sensor
.. then the offset for the map sensor signal ( signal middle point ) is skewed to run something like -10 psi ( 20 inch Hg ) to 10 psi within the range of the sender

RotaryEvolution

iTrader: (30)

i assume most conversions are using some method of adjusting fuel from the AFM signal, already knowing the AFM won't act correctly flowing more air from the turbo(will run rich and max out the airflow meter much sooner). slap an SAFC on, lower fuel trims or reclock the spring inside the AFM to add more tension(but that may create problems with starting).


as far as i'm concerned you could tweak the AFM to have a much higher ceiling but the pump switch could pose problems. the pump switch can easily be bypassed though but it will always prime with the key on.