Questions concerning Fuel Cut

[OneJArpus]

I have a 1.5JZ Swap with a T61 MP Turbo (.68 AR) 550 inj, AFPR, Walbro FP, no dampener. I have a SAFC, Innovate LC-1 Wideband, full IC, 3'' exhaust, 264 hks cams, and stock ECU.

I've heard that the 1 bar map sensor for the 1JZ sets the fuel cut at 14.7 PSi. I want to run 16-18 PSI. How would i get around this? Is it safe to install a HKS FCD STD type? I have one but not sure if i should install it.

Are there any major down sides? Major upsides?

Your input is appreciated.

Also how would i install the FCD with SAFC thanks

 

[Dylan JZ]

I run a neoAFC on my setup but I still installed a greddy BCC to avoid hitting the cut.. but a lot of folks feel that disabling boost cut is bad in general. I'll assume you already know that though..

http://www.mkiv.com/techarticles/bcc/why_bcc/Why_the_GReddy_BCC.htm

Despite the fact that some info is not directly applicable, I read the above thread and a few others before making my decision.

 

[OneJArpus]

hmmm interesting, i'm wondering could i possibly wire in a GM Map sensor with the stock ecu.

Sucks as i pd for a new hks fcd the same price as the GBCC.

 

[zSP3CTERz]

i read on her that running 550cc injectors will keep you from hitting cut.. is that true?

 

[OneJArpus]

I don't think injector size will prevent fuel cut. But the amount of boost pressure the Map sensor gets. It is a 1 bar map sensor so it is limited to 14.7 PSI it can see. Anything about that I think is what triggers the fuel cut defense in the ECU

 

[Gritz]

What bar is the 2jz map sensor?

 

[Dylan JZ]

people have said the 2j unit was capable of more pressure, but I recall them being the same as far as the sensor inside.

 

[zSP3CTERz]

so is running a fuel cut defencer on your car bad or good. if bad what are the chances of it being bad..

 

[OneJArpus]

IIRC 2jz map is 2 bar.


Im still gathering info on if its good or bad to run a FCD

 

[Evilempire1.3JZ-GTE]

It have been proven that the 2JZ & 1JZ haves roughly the same MAP they are both 2bar technicaly speaking because 1 positive 1 negative so its actually a 3bar sensor you need that reads up to 30psi and covers negative pressure.
The MAP sensors are roughly the same the big diference though is the 2JZ ecu can read higher voltages into the ecu fuel map before fuel cut so thats why people are missled into thinking the 2JZ MAP sensor is an upgrade.

You need a AFC neo wired into a 3Bar GM map then a tune done.
Your pushing the limits though of oem ecu 400-450hp is ok.
500+hp you better upgrade the regulator and fuel pump.
You also should be looking for a top feed rail if you plan to drive it alot at that boost.

AFCNeo + 3Bar sensor so at 5 volts on a 3 bar sensor is 30psi so 18psi your looking roughly at just under doubling the voltage from the 3 bar by tunning the AFC to get the fuel map spread out for more tunning points and least resolution loss.

The only time fuel injectors come into play is your boost is more power & demand more fuel then they can deliver. So you want the injector size to match and be a little higher then your WHP target because if you get a 1000cc+ injector and 3bar map sensor then only run 500hp to the wheels your wasting 500cc of fuel precision control thats wasting almost 50% resolution control which you will really notice at low end & a AFC will be overly tasked keeping AFRs right at low end to idle engine speeds.
I think your O'right for now with 550's your wideband will let you know if you need 750s & lower boost.
If you goto 750s for sure you want a top feed.

 

[cbutler]

good info, does anyone have a part number for the 3 bar GM map sensor?
Also, how critical do you guys think it is to get the map sensor if you are planning on going just over fuel cut limit, say 16psi? With AFC and wideband of course.

 

[Evilempire1.3JZ-GTE]

You have no choice when going over 14.5-14.7 psi you need a 3bar.
Otherwise you cant deliver acurate fuel to the air ratio. its not measurable if the sensor wont read it.

GM 3BAR here
http://shop.ebay.com/?_from=R40&_trksid=p3907.m570.l1313&_nkw=gm+3bar&_sacat=See-All-Categories about 40$
works pretty much the same
1 wire +5vdc
1 wire pressure sensor signal
1 wire is ground

Specs here from ~ -14.7psi - +29.4 psi abouit 45psi range

MAP Sensor Range (bar) 3 bar
MAP Sensor Range (psi) 44 psi
MAP Sensor Style GM, Bosch, MOTEC
Notes For use on applications running 1-30 pounds of boost. Stock style.
Quantity Sold individually.
Wiring Harness Kit Included Yes.

 

[OneJArpus]

Thanks evil, seeing as i just crashed my cavalier imma pull the GM Map sensor off of it and wire it in LOL. Thats if it isn't fucked.

I can use the GM Map and my current setup no problems? And would i need the FCD still because of the stock ECU reading teh voltage off of the map above 14.7?

 

[Evilempire1.3JZ-GTE]

I dont know if that sensor is a 3bar gm haves 2bar sensors to.
You can test it plug the sensor into a pressure regulated manifold.
Take resistance readings as you vary the pressure. what ever pressure it stops working at is the capacity or you can try looking the part number to look up the specs.

To tune a 3 bar its simple it will just output a lower voltage per psi then a normal 1jz map will read so that means at the peak capacity a 3 bar will output a 2bar sensors peak capactiy use the AFC to trim that voltage to achieve the ideal AFRs then you can boost above 2bar assuming your injectors could keep up with the boost afr and tune your setting as max.

 

[OneJArpus]

I dont know if that sensor is a 3bar gm haves 2bar sensors to.
You can test it plug the sensor into a pressure regulated manifold.
Take resistance readings as you vary the pressure. what ever pressure it stops working at is the capacity or you can try looking the part number to look up the specs.

To tune a 3 bar its simple it will just output a lower voltage per psi then a normal 1jz map will read so that means at the peak capacity a 3 bar will output a 2bar sensors peak capactiy use the AFC to trim that voltage to achieve the ideal AFRs then you can boost above 2bar assuming your injectors could keep up with the boost afr and tune your setting as max.

I don't plan on running anything over 2bar so even if it were a 2bar sensor would it still work.

Also, will i need to install a FCD?

 

[Evilempire1.3JZ-GTE]

No FCD, just AFC will do with 3 bar sensor

 

[OneJArpus]

Great, then i'll just get a 3bar map sensor, do you know the part # or which chevy it comes off of that is 3bar?

Also, how would i setup the SAFC to control the map and how would i know what # it is for the safc. I was reading the directions for the safc and the jza has a PR1 some have PR3 etc etc

 

[Evilempire1.3JZ-GTE]

http://shop.ebay.com/?_from=R40&_trksid=p3907.m570.l1313&_nkw=gm+3bar&_sacat=See-All-Categories just buy a new one cheap bay with pigtail.

 

[OneJArpus]

Yea just bidded on one.

I have a bad sputtering issue. Any time the car see's any positive boost it starts to sputter. Time to go back into my wiring and make sure it is ok with the SAFC.

ugh. Plus i have a leaky injector dammit!