Help - Disable Fuel Cut - EBC - 3SGTE 4gen - MR2 Owners Club Message Board
 
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post #1 of 17 (permalink) Old August 21st, 2019, 10:51 Thread Starter
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Help - Disable Fuel Cut - EBC - 3SGTE 4gen

Hi,

I've installed an Electronic Boost Controller on my Stock 3sgte 4gen to reach more boost because, in stock it reaches around 0.45bar. (It's the A/T version, and I have Manual transmission, so the car doesn't give me more pressure).

Then, when I'm running at around 3.000rpm, I push the gas pedal to the metal and boost gives up!! "Whooooaaaahhh!!".
But, when the car reaches 4.500rpm, the car loses power and make a noise like a rev limiter "BRRRRRMMH..".

I think the car is limiting the igniter or the fuel injection because I'm trying to reach more boost than expected, so I like to remove the fuel cut and try again.

I have searched, and many people says that you can disconnect a vacuum hose which controls that pressure and automatically you have removed the fuel cut.. well... I've try some vacuum hoses but no result.
If I remove the MAP vacuum, or I remove the MAP vacuum hose and then I plug a bolt, the car stops inmediatly. Engine seems to need that vacuum connected.

The MAP vacuum hose is attached to a small cylinder with two hoses. Right, to the MAP. Left, to.. (i don't know. I think it goes to Fuel Pressure Regulator).

Any ideas?

Thank you in advance.

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post #2 of 17 (permalink) Old August 21st, 2019, 13:04 Thread Starter
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I have recorded a video. (This forum doesn't allow me to upload video until the post be greater) I'll describe:

If you can see, I can pass the 5.000 rpm slowly and 6.000 rpm in half gas pedal. But, when I press the full gas pedal, at 100%, the rpm goes down and car sound is like rev limiter.

It is the same if I'm on 3000 rpm and full gas, the rpm go up until 4.500-5.00rpm, with same sound.

I'm going to check my MAP sensor.
Also: My engine is japan imported so, I think is a good idea to buy a new OEM knock sensor. What do you think?

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post #3 of 17 (permalink) Old August 21st, 2019, 14:33
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Not sure on why this is happening but I can tell you why the MAP vacuum hose makes the car shut off.

These are MAP sensor engines (GEN4 3SGTE) so they use the MAP sensor to run fuel maps. You remove the vacuum hose and 1, it loses a proper signal and 2, you create a rather large vacuum leak which makes the car freak out.

What you refer to is the GEN2 3SGTE which is AFM and only uses the MAP sensor for fuel cut and the factory boost gauge. This works if you disconnect the vacuum hose and plug it up. Disregard this information for your engine.
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post #4 of 17 (permalink) Old August 21st, 2019, 15:30 Thread Starter
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Quote:
Originally Posted by GDII View Post
Not sure on why this is happening but I can tell you why the MAP vacuum hose makes the car shut off.



These are MAP sensor engines (GEN4 3SGTE) so they use the MAP sensor to run fuel maps. You remove the vacuum hose and 1, it loses a proper signal and 2, you create a rather large vacuum leak which makes the car freak out.



What you refer to is the GEN2 3SGTE which is AFM and only uses the MAP sensor for fuel cut and the factory boost gauge. This works if you disconnect the vacuum hose and plug it up. Disregard this information for your engine.
Thanks for your explanation.

So, if I understood correctly, I canNOT use a Fuel Cut Defender (for example the HKS FCD) to remove the Fuel Cut on GEN4 because I will affect the MAP sensor measurement, right?

Does anybody knows is Fuel Cut can be removed from GEN4 3SGTE?

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post #5 of 17 (permalink) Old August 21st, 2019, 15:30 Thread Starter
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This is my issue explained above. Only when I go to full gas.https://cloud.tapatalk.com/s/5d5da9e9..._195802053.mp4

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post #6 of 17 (permalink) Old August 21st, 2019, 19:01
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I believe what your after is a MAP clamp (Zener diode). This will limit the maximum voltage the ECU see's for your MAP sensor, which you set to just under boost cut (Essentially the end of the ECU MAP)

Personally I wouldn't go that way - your going into dangerous territory.
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post #7 of 17 (permalink) Old August 22nd, 2019, 00:43 Thread Starter
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Thanks Pete, I understand.
Yes, I know is dangerous. I only wanted to make a try and solve my problem.
As you can see in the video, mi boost only goes to 0.3 bar. I set it too low for the test and same problem, always.

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post #8 of 17 (permalink) Old August 22nd, 2019, 20:47
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Fuel cut in the sense of over boosting is only applied at 18psi? on these engines. The stock waste gate spring is around 7psi so your 4psi is not even getting to waste gate pressure so your boost controller, OEM or aftermarket is not the problem here.

And yes I agree with PETE about not using an FCD. They are only made for AFM cars like the GEN3 3SGTE and 2JZGTE. You don't want to be messing with the main fuel map to fix this problem.
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post #9 of 17 (permalink) Old August 26th, 2019, 07:20 Thread Starter
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Originally Posted by GDII View Post
Fuel cut in the sense of over boosting is only applied at 18psi? on these engines. The stock waste gate spring is around 7psi so your 4psi is not even getting to waste gate pressure so your boost controller, OEM or aftermarket is not the problem here.



And yes I agree with PETE about not using an FCD. They are only made for AFM cars like the GEN3 3SGTE and 2JZGTE. You don't want to be messing with the main fuel map to fix this problem.
Thanks for your comment.
I was thinking that maybe I have a faulty MAP sensor.
I'm going to clean the sensor and try if I notice any changes. If yes, I will replace with another new OEM MAP sensor.

If I connect my OBD2, I can read the MAP value, but is strange... A bit confusing. When idling (800rpm more or less) it reads 0.27bar. (When standard would be around -0.6 bar or similar). But maybe I'm reading with a bad OBD2 scanner. So, I will check the Volts value at IG ON and idling.

I will post my answers here.

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post #10 of 17 (permalink) Old August 26th, 2019, 15:00
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Originally Posted by ST-Ryu View Post
Thanks for your comment.
I was thinking that maybe I have a faulty MAP sensor.
I'm going to clean the sensor and try if I notice any changes. If yes, I will replace with another new OEM MAP sensor.

If I connect my OBD2, I can read the MAP value, but is strange... A bit confusing. When idling (800rpm more or less) it reads 0.27bar. (When standard would be around -0.6 bar or similar). But maybe I'm reading with a bad OBD2 scanner. So, I will check the Volts value at IG ON and idling.

I will post my answers here.

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You should not be seeing boost at idle. that's not quite right. I'm not sure if trying to clean the sensor will work. The tend to have a filter on the vacuum hose. Maybe the sensor itself is damaged electronically.

What OBD2 scanner are you using?
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post #11 of 17 (permalink) Old August 26th, 2019, 15:28 Thread Starter
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Originally Posted by GDII View Post
You should not be seeing boost at idle. that's not quite right. I'm not sure if trying to clean the sensor will work. The tend to have a filter on the vacuum hose. Maybe the sensor itself is damaged electronically.



What OBD2 scanner are you using?
Hi,

Today, after cleaning the sensor and the filter of vacuum hose, I get at idle:
-0.62 bar (negative) at boost gauge
+0.35 bar (positive) at OBD2 (O-0B-0).
But, one idea came to my head. If I think in atmospheric pressure...
+0.35 - 0.97 = -0.62 bar

The reader is an ELM327 Wi-Fi and OBD2 Facile for Android.

Regards.

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post #12 of 17 (permalink) Old August 27th, 2019, 09:21
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Quote:
Originally Posted by ST-Ryu View Post
Hi,

Today, after cleaning the sensor and the filter of vacuum hose, I get at idle:
-0.62 bar (negative) at boost gauge
+0.35 bar (positive) at OBD2 (O-0B-0).
But, one idea came to my head. If I think in atmospheric pressure...
+0.35 - 0.97 = -0.62 bar

The reader is an ELM327 Wi-Fi and OBD2 Facile for Android.

Regards.

Enviado desde mi G3112 mediante Tapatalk
Right on, MAP, Manifold Absolute Pressure. Pressure is from 0 (pure vacuum) not 0 (atmospheric pressure)
a MAP sensor should never show a negative number, and a pressure of 1 (or thereabouts depending on elevation) should be engine off, atmospheric pressure
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post #13 of 17 (permalink) Old August 27th, 2019, 09:22 Thread Starter
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Originally Posted by wildhippie666 View Post
Right on, MAP, Manifold Absolute Pressure. Pressure is from 0 (pure vacuum) not 0 (atmospheric pressure)

a MAP sensor should never show a negative number, and a pressure of 1 (or thereabouts depending on elevation) should be engine off, atmospheric pressure
Understood. Thank you

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post #14 of 17 (permalink) Old August 28th, 2019, 08:03
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I have a gen4 running a stock A/T ECU and have recently struggled with boost issues similar, maybe even the same.....
couple of things I have recently learned that may be useful to you.

The stock ecu will just DUMP fuel at full throttle, though it seems you are lacking fuel for power, chances are you have too much.

If the ECU throws a code (other than transmission ones) boost will be limited to about 8psi no matter how hard you try to make it go higher. ( I had to replace both the Air Intake Temp sensor and engine bay temp sensor to get full boost)

HKS makes a fuel cut defender, though I have seen no documentation on its use for a 4th gen, there should be a way. Its only 4 wires and a selector switch.....
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post #15 of 17 (permalink) Old August 28th, 2019, 08:11
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Originally Posted by DeftAnesthetik View Post
I have a gen4 running a stock A/T ECU and have recently struggled with boost issues similar, maybe even the same.....
couple of things I have recently learned that may be useful to you.

The stock ecu will just DUMP fuel at full throttle, though it seems you are lacking fuel for power, chances are you have too much.

If the ECU throws a code (other than transmission ones) boost will be limited to about 8psi no matter how hard you try to make it go higher. ( I had to replace both the Air Intake Temp sensor and engine bay temp sensor to get full boost)

HKS makes a fuel cut defender, though I have seen no documentation on its use for a 4th gen, there should be a way. Its only 4 wires and a selector switch.....
The only reason to use a Fuel Cut Defender would be if you were running higher than 18PSI, there's no reason it should be cutting fuel at such a low pressure for OP.
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post #16 of 17 (permalink) Old August 28th, 2019, 08:19 Thread Starter
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Originally Posted by DeftAnesthetik View Post
I have a gen4 running a stock A/T ECU and have recently struggled with boost issues similar, maybe even the same.....

couple of things I have recently learned that may be useful to you.



The stock ecu will just DUMP fuel at full throttle, though it seems you are lacking fuel for power, chances are you have too much.



If the ECU throws a code (other than transmission ones) boost will be limited to about 8psi no matter how hard you try to make it go higher. ( I had to replace both the Air Intake Temp sensor and engine bay temp sensor to get full boost)



HKS makes a fuel cut defender, though I have seen no documentation on its use for a 4th gen, there should be a way. Its only 4 wires and a selector switch.....
Yeah I don't have CEL errors (apart from 2 o 3 from transmission). But I upgraded my fuel pump to walbro 255. So I'm not sure if fuel is the problem.

Thanks for the information .

I will replace that sensors!

Before you replaced that sensors, did you had engine error codes?

Regards,

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post #17 of 17 (permalink) Old August 28th, 2019, 09:05
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Yes I had codes for the AIT and from time to time I would see the engine bay fan light come on so I replaced that too. They are both the same part. if you dont want oem denso's you can get them for pretty cheap, I cannot find OEM for less than about $50 each I got delco's for just over $20 each p/n:213-4438

I don't know what pump has been put in mine but I know it has been upgraded as well, also running a greddy style upgraded intercooler. if you still have stock intercooler that could also be your bottleneck.
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