Redtop

[240sxredtopdrift]

i bought an sr20det redtop to put in my S13 and I’ve been having a lot of problems getting it to run good. I had a lot of problems with leaking intercooler piping finally i got it sealed but its still bucking and missing. When it starts to miss I just let up a bit on the throttle it stops. I checked the plugs and there white so I’m afraid to blow my motor. i have a front mount intercooler, Greddy Blow off valve, walbro 255 fuel pump, 3" Exhaust everything else on the motor is stock. I noticed that there is no speed limiter! I was wondering if my computer was modified so i checked inside no daughterboard. does anyone know what could be wrong? My computer code is 55, no problem. Idles great(after MAF reground). I have a air/fuel ratio gauge at idle it goes lean and when I’m at 25% throttle it goes to rich but when i floor it bucks and misses flashes LEAN. I have reground my MAF and Oxygen sensor because ohms were high. I checked for leaks between my MAF and turbo. Maybe my MAF is defective what voltage am i supposed to get at 3000RPM? i know diagnosing motor on the net is hard. How can i test other components like fuel pressure and TPS? thanks.




1990 240SX
SR20DET Redtop @ 7psi (4 now)
Megan racing FMIC
3" IC Piping
3" Exhaust (JDM)
Walbro 255LPH Fuel pump
Greddy Blow off Valve Type RS
Clutchmasters stage 1 clutch
Silvia LSD
RSR D1 Spec Polyurethane bushings
Megan Racing Track series fully adjustable Coilovers
Greddy Tower Brace Front
EM tower brace Rear

[slider2828]

It might be because no limiter, secondly an ecu can be modified without a daughter board as well. But if modified it shouldn't go lean like that as well. Fuel pressure can be only really tested with a guage. A tps can be tested based of FSM ohm/voltage meter. Sounds like you have one of those autometers crap rich lean meters which doesn't tell you anything. Check your timing as well.

[statik]

It might be because no limiter, secondly an ecu can be modified without a daughter board as well

just curious, how would you modify an sr ecu without a daughterboard for the new rom...

[slider2828]

You could get a flash then retune. Basically, an IC chip, you can pull it out and then hook it up to an eprom programmer and then just put it back in. That is about it. They do it like that in Hondas.

[240sxredtopdrift]

my MAF signal voltage goes to 7V hahaha thats why its cutting. i'm gonna try to rewire it agian. my MAF that i'm using now is from my ka24e it worked fine in my ka. is the power voltage supposed to be +5 or +12? mine is +12.

and i think i have no speed limiter because its an ecu from an automatic.

[bardabe]

be sure that when you wire uop your MAF you don't cross your signal and power wires for the MAF. the signal wire is the white with black stripe, (5V) power wire is full white (12V) and ground wire is black. if you mix your wires you can potentially damage the ECU or even Fry it.

-Juantons

[cotbu]

:bite:be sure that when you wire uop your MAF you don't cross your signal and power wires for the MAF. the signal wire is the white with black stripe, (5V) power wire is full white (12V) and ground wire is black. if you mix your wires you can potentially damage the ECU or even Fry it.

-Juantons
What kind of car do you have?
Signal is white, power is black and white or maybe your right? IDKA
:hammer:

[240sxredtopdrift]

ok i checked my wiring. Redtop with ka24e MAF.

A +12
B ground
c Signal

this is right....? i think so.

volts read

key on .8v
idle 1.5v
3000 no load 2.??V
full throttle on street it can go up to 7V if i push it?!?!?!?


i rechecked for piping leaks(pressure test to 15psi) and there is none!

[slider2828]

The KA MAFS, need to be rewired and NO the MAFS will not go above 7Volts. Nothing on your car pretty much should god 7 VOLTs. Anything that high you run the risk of burning out your ECU. Because the MAFS is directly connected to the ECU, you cross those wires, your ecu is gone. I have don't it, sparked the MAFS wire, ECU was gone. Idle should not be 1.5, unless you have a Z32 MAFS, highest flow you can get is 5V. I tune my maps by tapping the Hot Airflow Input. I ran my SR20DET at 14PSI (with proper upgrades) and NEVER got above 5V on the stocks MAFS, so something is wrong. Get a new mafs.

[cotbu]

ok i checked my wiring. Redtop with ka24e MAF.

A +12
B ground
c Signal

this is right....? i think so.

volts read

key on .8v
idle 1.5v
3000 no load 2.??V
full throttle on street it can go up to 7V if i push it?!?!?!?


i rechecked for piping leaks(pressure test to 15psi) and there is none!
Your Wiring is correct!
The KA MAFS, need to be rewired and NO the MAFS will not go above 7Volts. Nothing on your car pretty much should god 7 VOLTs. Anything that high you run the risk of burning out your ECU. Because the MAFS is directly connected to the ECU, you cross those wires, your ecu is gone. I have don't it, sparked the MAFS wire, ECU was gone. Idle should not be 1.5, unless you have a Z32 MAFS, highest flow you can get is 5V. I tune my maps by tapping the Hot Airflow Input. I ran my SR20DET at 14PSI (with proper upgrades) and NEVER got above 5V on the stocks MAFS, so something is wrong. Get a new mafs.
Correct, I topped the stock mafs @ 13psi. It did try to read more, but whatever it was saying the S-AFC didn't like.

[fliprayzin240sx]

Double check your timing, change your o2. Well until you eliminate the maf atleast.

[statik]

You could get a flash then retune. Basically, an IC chip, you can pull it out and then hook it up to an eprom programmer and then just put it back in. That is about it. They do it like that in Hondas.

you cannot reflash the stock ecu chip, thats why they add the daughterboard, and bypass the stock rom.

[bardabe]

:bite:
What kind of car do you have?
Signal is white, power is black and white or maybe your right? IDKA
:hammer:
well right now I am looking at my unspliced Harness and my SR MAF

Pin B (black white) 5V
Pin C (black) Ground
Pina D (white) 12V

someone prove me wrong so I can go buy an ECU lol

[240sxredtopdrift]

well right now I am looking at my unspliced Harness and my SR MAF

Pin B (black white) 5V
Pin C (black) Ground
Pina D (white) 12V

someone prove me wrong so I can go buy an ECU lol



is that on a blacktop?? because on my motor the white is signal (+5) to ecu.

[240sxredtopdrift]

i'm going to see my motor guy on thursday. he said he will let me exchange my MAF. i'll let u guys know how it goes......hopefully my computers ok. thanks all 4 your help.

[bardabe]

is that on a blacktop?? because on my motor the white is signal (+5) to ecu.
180sx Blacktop

[240sxredtopdrift]

i could not wait for thursday so i went to see my motor guy. He likes me cause i send him people to buy engines! he let me change my computer and my MAF but unfortunatly the car was the same. so i tried like 4 different MAFS and it did not fix it. i had 1.5V at idle and could go over 6-7v when underload. i dont understand! i checked for leaks like 4 times now F***.

[smithers584]

your maf is a 5 volt sensor, read the fsm, it will tell you at idle you are supposed to be around .9 volts and at 3000 rpm you will read like 1.5-2.0 or something like that. have you actually tested the maf voltage or are you just reading off the safc II? are you sure you have the right in and out on your safc II? i think the only maf that will read that high is a q45 maf. if you would download the fsm, it will tell you everything you ever want to know about your sensors, all of them. start there, for example, you say your 02 read high ohms, fsm says to check for 3-1000 ohms for a good o2.