Disconnecting the BPS on sw20 turbo

[Al]

Ok guys in the states say this is the way to have no fuel cut without a FCD on your mr2 turbo. As all the BPS (boost pressure sensor) does is tell the facto boost gauge what to read and to tell the ecu that it has hit 12.5psi for the fuel cut if it gets that high..ive been told differently here that it also has something to do with ignition maps and the like?

Can anyone clear this up?

[Al]

OK ive pulled the sensor wire clip off and had the car idling. The stock boost gauge just points up and I have no error codes. Ill take the car for a drive and see what happens

[Malcolm]

it's actually called a TPS (a little confusing, since there's a Throttle Position Sensor too). I think with the unplugging thing you have to unplug it after you start the car, because if you unplug it before starting the car it goes into limp mode. The other thing I believe you can do is to block off the line going into the bottom of it, that makes the ecu think it is still functioning, rather than detecting the open circuit on the start up diagnostic check thing it does.

[Malcolm]

I just remembered that one of those two things (unplugging it or blocking the line off) makes it still hit fuel cut as normal (apparently it can calculate boost based on AFM, RPM and TPS signals), but I don't remember which. There was actually a bit of discussion about this on here a couple of months ago

[Al]

Yep i wound out to 15psi and it went stop pretty quick

[Al]

OK found out i have to remove the hose....not the plug.

Al

[matt dunn]

OK found out i have to remove the hose....not the plug.

Al

You can mod it to just up the limit rather than remove it.

[Al]

How so? Id like my cut to be at 17psi.

[Malcolm]

I imagine you could make a bleed or something similar in the line going to the map sensor, just as you would on the line going to the wastegate for boost control. You can also run a variable resistor between the PIM and E2 I believe.

BTW isn't 17psi a bit high? I don't go over 13psi on 98 octane gas,(knocks at 14psi) and only go to 16psi on race gas, admittedly that's on the upgraded turbo but I still think 17psi is mighty high for stock gen 2 fuel maps, not to mention just blowing a lot of hot air on a stock ct26

[Al]

I have a ct20b

[matt dunn]

How so? Id like my cut to be at 17psi.

By putting diodes inline with the signal wire.
Make sure they are the right way around.
Each diode gives about 0.8 volts drop to the ECU so keep adding them inline untill the boost level required is reached. Although you are limited to the max reading the senssor can handle.
Good for small increases 3-5 psi but I dont know if it will make it to 17 psi.

Matt

[Al]

i'll just pull the hose then. Ive adjusted my Greddy Profec B and it holds rock solid all the way to redline, even with my aussie exhaust 3" dp

[flygt4]

wuldnt it just be easer to install an fcd and then just put the limit real low and test it raising it each time til u get the desired level. u only need to cut one wire and tap 2 others on.u may spend a bit more but i reckon its a bit more reliable

[Al]

Im from the south island and i have scottish blood, i wont spend money unless i have to

[Malcolm]

17psi on a CT20b is still very high for stock fuel maps. When I was in chch running on crap 96 octane gas I didn't feel safe going over 12psi on the t04e/ct26. It's not the lack of fuel that's the problem either, it's about the ignition timing. The ecu's maps don't just vary the fuel for boost pressure, but also the timing, they retard the timing as boost rises to prevent detonation, however the stock gen 2 maps only retard timing based on boost to approx 12.5psi, so from there on, even if you have enough fuel, the timing is going to be way out from where it should be, and that is what is most likely to cause detonation, especially on low octane gas, and with the already aggressive stock timing maps.

I'm just trying to help, btw, so don't take this the wrong way.

[Al]

Nah thats all good mate, on the US mr2 board they claim the stock ignition is mapped to 18psi...but the ecu just dumps fuel in after 12.5psi

btw im not gonna run 17psi...i just wanted my cut to be there, i run 10psi on the street and on avgas at ruapuna it will be 16psi

Al

[Malcolm]

well, I beg to differ in regards to the stock ignition maps
I'm not sure on the original source of these, but I got them from alltrac.net
Ignition maps note they stop at .8bar


Fuel maps

[fivebob]

well, I beg to differ in regards to the stock ignition maps
I'm not sure on the original source of these, but I got them from alltrac.net
Ignition maps note they stop at .8bar

Actually they don't, the load points on that map (which BTW is I believe for the Gen III as the Gen II is AFM controlled not MAP) are not necessarily correct, in fact nobody really knows what they are as Toyota won't reveal that info. What you see on that map is someones guess as to what the load point is. Also note that the RPM axis stops at 6800, so it may be that the graph is incomplete as well

The original source for these maps is http://kaele.com/~kashima/car/3sgte/index.html a company that sells the equipment necessary to reverse engineer the Toyota ECU

[Malcolm]

well then, I stand corrected.

[mister two]

hi guys sorry to interupt but i noticed that someone here said briefly how to raise the boost pressure...
i am running 9 pound at the mo and i wanna put it up to 12 psi.
how do i do that? i know it can be done easily but im new to turbs and i dont know how?
any help appreciated
ps car is a sw20

(i was having a play just before and in my hose that runs off the side of the turb, to what i believe is the waste gate(?) there is a t intersection with one part blocked off. when i removed the block and had the hole going to the atmosphere it ran 10-10.5 psi and when i restricted the flow(dont ask how it was mongrel) it dropped down to 8 psi. so i know that i am onto something but i just dont know what?)