Does the s13 sr20det have fuel cut?
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vwluv10338
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Movingviolation240
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'93 Lexus SC300 w/ SP66 turbo kit
Stock ECU has a fuel cut at 4.5volts on the MAF, depending on your mods you will hit this at different boost levels (since it's airflow baised not pressure). Typically with a stock turbo that will happen around 14psi. So yes you are hitting the stock fuel cut which is designed to keep the crappy injectors from going static and your motor from blowing up. The stock MAF runs off the chart and cant' measure anymore air so it stops your fuel to keep you from making anymore boost and hurting things. A Z32 MAF will get rid of the problem, so will an ECU re-tune.
Paul
Paul
T25 should produce up to 20psi and settle to 16-17 if you run it without a wastegate signal for 1/4 mile runs which some people do. This is out of the compressor's efficiency zone, but will still drop 1/4 mile times - at the expense of turbo life.
If you can't boost over 14 psi, you probably have an intercooler coupling leaking at high pressure that works perfrctly fine at lower psi. Or your BOV is leaking.
Airflow based fuel cut? I've never heard of that, and there is no way is that happening at 14 psi. The stock MAF flows up to about 290 crank hp, the stock fuel system can definitly handle 290 chp with just a Walbro fuel pump. Walbro hi-press fuel pump can handle 350 whp no problem.
_______________________Jeff HHeavy Throttle Performance
If you can't boost over 14 psi, you probably have an intercooler coupling leaking at high pressure that works perfrctly fine at lower psi. Or your BOV is leaking.
Airflow based fuel cut? I've never heard of that, and there is no way is that happening at 14 psi. The stock MAF flows up to about 290 crank hp, the stock fuel system can definitly handle 290 chp with just a Walbro fuel pump. Walbro hi-press fuel pump can handle 350 whp no problem.
_______________________Jeff HHeavy Throttle Performance
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BuudWeizErr
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hum.. well i tested all the piping and it held 30psi for a good while on the pressure checker. Do you think that maybe my wastegate spring is just shot? Ill pull the hose on the wastegate and plug it and them make a run on the street just to see what happens. Also i tried to set my boost at 14psi with my profect A and it will hit 14 psi in first, but in second it drops to below 10 and stays at about 9psi. however when i shift it will hit the set psi for a split second. It has done this with 3 bost controlers, so its not that.
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Movingviolation240
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'93 Lexus SC300 w/ SP66 turbo kit
I said it would make 240hp, that's WHP, so that's about 290 at the crank. When the MAF hits it's max voltage on airflow it is going to 'cut' because it simply dosn't have the resolution to go any higher. If you stick on a massive turbo you can hit 'cut' at a lower boost level because your pulling more CFM through, so the MAF sees the 'cut' at a lower RPM.
What he is describing at 14psi is EXACTLY what my CA did at that boost level and exactly what my freind's SR did there. I never had that issue because I had a Z32 MAF on my SR (higher flow than stock, so when it hits it's max of arround 5volts it's flowing 550hp of air..... Which means I won't hit that because my GT25R can't flow within 100hp of that). Maybe some of the different number ECU's are a little different (I'll have to see what my buddy's car was) but I know it has one.
What he is describing at 14psi is EXACTLY what my CA did at that boost level and exactly what my freind's SR did there. I never had that issue because I had a Z32 MAF on my SR (higher flow than stock, so when it hits it's max of arround 5volts it's flowing 550hp of air..... Which means I won't hit that because my GT25R can't flow within 100hp of that). Maybe some of the different number ECU's are a little different (I'll have to see what my buddy's car was) but I know it has one.
popping and sputtering usually isn't turbo related. As for boost cut, the cecu can cut boost but only if you have the boost controll solenoid hooked up. Most of us don't. Everything Movingviolation has told me on the boards has been very acurate. It definately sounds like an ignition or fuel problem to me. BOth of whitch would happen if the ECU was freaking out becaseu of an overboost condition.
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Movingviolation240
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'93 Lexus SC300 w/ SP66 turbo kit
I'll try to find where I read this, it was off an australian website... I know they have to deal with that over there because if you look at their list of mods half the time it includes a reprogramed ECU for boost cut, or an HKS FCD or somthing similar.
But first I have to put in 8hrs at work..... oh joy
Paul
But first I have to put in 8hrs at work..... oh joy
Paul
Heres what im gonna try, ill turn my profec to 17psi and hit the streets for a few bursts and see if it still cuts out the fuel after 14psi. as of now i have only seen the car do it in first gear as its the only gear that will give me over 12psi. or ill just pull the wastegate hose for a few and try that.
OK heres the deal, I pulled the wastegate hose and went for a run. In first gear the turbo builds 14psi very fast, so fast that i dont think fuel can keep up cause the engine sputters. Then i tryed 2ed gear, holly carp the car boosted 22psi and droped to 12psi within seconds. then i tried 3ed gear in this gear the car seems to hold what ever boost i want to run, after 19psi the car runs out of fuel (pump gas) and misses. So now im going to set my profec A at 12psi on low boost and 18psi on over boost and see if it holds it.
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Movingviolation240
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'93 Lexus SC300 w/ SP66 turbo kit
ECU cuts fuel when the MAF is maxed - how does this make sense? Why would Nissan deliberately introduce a feature that would cut fuel, resulting in extremely lean condition that can lead to detonation just at the time (high boost / cfm intake) it could do the most damage? Why wouldn't the MAF just keep sending 5v?
I've had an SR MAF on a Big28 turbo upgrade w/ 550 injectors and JWT ECU (tuned for Z32 but I used the S-AFC to read the stock SR MAF) and the engine just kept going until it simply wouldn't build more boost or power. There was no fuel cut, and psi was 16-17. Just a wall that the engine would not go past. As measured by SAFC - Throttle 100%, Airflow 100%
________________________Jeff HHeavy Throttle Performance
I've had an SR MAF on a Big28 turbo upgrade w/ 550 injectors and JWT ECU (tuned for Z32 but I used the S-AFC to read the stock SR MAF) and the engine just kept going until it simply wouldn't build more boost or power. There was no fuel cut, and psi was 16-17. Just a wall that the engine would not go past. As measured by SAFC - Throttle 100%, Airflow 100%
________________________Jeff HHeavy Throttle Performance
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Movingviolation240
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'93 Lexus SC300 w/ SP66 turbo kit
That's because of the lower voltage of the Z32 MAF. The fuel cut works just like the rev limiter, if you stop all the gas at once there isn't enough fuel in the combustion chamber to cause any problems. Why did Toyota do it to the Supra, or why did Mitsu do it to the 4G63..... to keep ppl from going way high on boost and blowing stuff up. If the motor dosn't run up that high then you can't hurt it.
I know for a fact that the CA18DET has that exact same function (I hit it many times before upgrading the ECU and MAF), and I'm sure that the SR has it as well. Maybe it has somthing to do with the different number on your ECU (i.e. the red '62')
http://www.se-r-list.org/new-archives/W ... 09991.html
(If you object to me using Horse Power (hp) as a measurement of airflow,simply substitute in CFM or whatever you're happier with...)
Air Flow Meters (AFM), a.k.a Mass Airflow Meters (MAF):
The basic function of any ECU is simple. Calculate the correct amount offuel and ignition advance required by the engine at any time. To make thesecalculations it needs to sense how much "load' the engine is under.
The primary load sensor on the Nissan ECCS ECUs is the Air Flow Meter. It isthe ECUs biggest asset and also it's achilles heel (from a performanceviewpoint).
The AFM measures the true mass of air entering the engine. Since mass of airentering the engine is known, determining the mass of fuel required for anappropriate Air Fuel Ratio is a straight forward calculation. This alsomeans the majority of modifications will not require a retune, unlike MAPbased systems.
Unfortunately the standard AFM can be a considerable restriction in theintake. A 50mm diameter is not a large area for a turbo to draw through.AFMs also have a set operating range from 0-5V, representing a flow of airfrom 0 to their max rating. 5V on a CA18DET AFM is equivalent to enough airto make around 200hp. 5V on a 300ZX TT AFM is enough for over 500hp.Fortunately, retuning for a larger, less restrictive AFM is possible.
Once the CA18 ECU senses the AFM is at its limit (ie at or close to 5V), itwill cut fuel to protect the engine. The dreaded boost cut. Or moreaccurately, Air Flow Cut.
Once the Airflow meter is at 5v, any increase in flow will still result in areading of 5v, as the sensor is at its limit. The ECU can no longercalculate the correct amount of fuel, so it shuts down the engine to preventa lean out. Once the AFM reads below 5v, the ECU will inject fuel onceagain.
NorrisDesigns
The 200SX like many Japanese cars has a turbo boost cut-out. This works when the engine management system senses that boost levels are above the expected figure and takes action to shut the injection down. We offer an FCD (Fuel Cut Defender) which when fitted to the ECU prevents this cut out, which allows boost levels over 18Psi.
Greddy and HK$ also sell a fuel cut defence for the SR in the UK and Australia.
That's the basic information which I baised my response around. I know they have to deal with that in Australia and the UK, dunno about Japan since. I don't go on any of those message boards since I only speak english.
I know for a fact that the CA18DET has that exact same function (I hit it many times before upgrading the ECU and MAF), and I'm sure that the SR has it as well. Maybe it has somthing to do with the different number on your ECU (i.e. the red '62')
http://www.se-r-list.org/new-archives/W ... 09991.html
(If you object to me using Horse Power (hp) as a measurement of airflow,simply substitute in CFM or whatever you're happier with...)
Air Flow Meters (AFM), a.k.a Mass Airflow Meters (MAF):
The basic function of any ECU is simple. Calculate the correct amount offuel and ignition advance required by the engine at any time. To make thesecalculations it needs to sense how much "load' the engine is under.
The primary load sensor on the Nissan ECCS ECUs is the Air Flow Meter. It isthe ECUs biggest asset and also it's achilles heel (from a performanceviewpoint).
The AFM measures the true mass of air entering the engine. Since mass of airentering the engine is known, determining the mass of fuel required for anappropriate Air Fuel Ratio is a straight forward calculation. This alsomeans the majority of modifications will not require a retune, unlike MAPbased systems.
Unfortunately the standard AFM can be a considerable restriction in theintake. A 50mm diameter is not a large area for a turbo to draw through.AFMs also have a set operating range from 0-5V, representing a flow of airfrom 0 to their max rating. 5V on a CA18DET AFM is equivalent to enough airto make around 200hp. 5V on a 300ZX TT AFM is enough for over 500hp.Fortunately, retuning for a larger, less restrictive AFM is possible.
Once the CA18 ECU senses the AFM is at its limit (ie at or close to 5V), itwill cut fuel to protect the engine. The dreaded boost cut. Or moreaccurately, Air Flow Cut.
Once the Airflow meter is at 5v, any increase in flow will still result in areading of 5v, as the sensor is at its limit. The ECU can no longercalculate the correct amount of fuel, so it shuts down the engine to preventa lean out. Once the AFM reads below 5v, the ECU will inject fuel onceagain.
NorrisDesigns
The 200SX like many Japanese cars has a turbo boost cut-out. This works when the engine management system senses that boost levels are above the expected figure and takes action to shut the injection down. We offer an FCD (Fuel Cut Defender) which when fitted to the ECU prevents this cut out, which allows boost levels over 18Psi.
Greddy and HK$ also sell a fuel cut defence for the SR in the UK and Australia.
That's the basic information which I baised my response around. I know they have to deal with that in Australia and the UK, dunno about Japan since. I don't go on any of those message boards since I only speak english.
Interesting, looks like you are right on the MAF at limit issue, it is clear the CA does exactly what you described.
What is still unclear is whether the SR does the same thing. The Norris Designs blurb states:
"The 200SX like many Japanese cars has a turbo boost cut-out. This works when the engine management system senses that boost levels are above the expected figure and takes action to shut the injection down."
Engine management system SENSES BOOST LEVELS - since I and most others have the OEM boost sensor removed how could the 'turbo boost cut' feature be working on a car with this disabled? That is exactly WHY we don't hook those devices up. I still have never experienced any ECU boost or fuel cut on an SR under 20psi.
I also agree it is strange that turboex can't boost as high in first gear as the other gears - weird.......
_______________________Jeff HHeavy Throttle Performance
What is still unclear is whether the SR does the same thing. The Norris Designs blurb states:
"The 200SX like many Japanese cars has a turbo boost cut-out. This works when the engine management system senses that boost levels are above the expected figure and takes action to shut the injection down."
Engine management system SENSES BOOST LEVELS - since I and most others have the OEM boost sensor removed how could the 'turbo boost cut' feature be working on a car with this disabled? That is exactly WHY we don't hook those devices up. I still have never experienced any ECU boost or fuel cut on an SR under 20psi.
I also agree it is strange that turboex can't boost as high in first gear as the other gears - weird.......
_______________________Jeff HHeavy Throttle Performance
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Movingviolation240
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'93 Lexus SC300 w/ SP66 turbo kit
Well, it's not really a boost cut per say but an airflow cut. The FCD basically clamps the MAF signal at like 4.9 volts so the ECU dosn't cut fuel because it never hits that magic 5v number. The problem is that the car dosn't get any more gas above that point either. Thats why they say not to run it over 19 psi.
How much voltage your MAF puts out is directly related to how much airflow your motor is using. If you have a SMIC or a crappy intake, or it's a hot day you can run more boost and still have a lower airflow. On the flip side I could hit fuel cut at about 8psi on my old CA because I had a big turbo, ported head, and cams.
The Z32 MAF (since it flows more air at 5volts) dosn't suffor from the boost cut untill your making 500+hp. So if you upgrade your MAF you get around the problem.
PS that blurb from ND is talking about an S14 w/sr20det not the CA18DET.
How much voltage your MAF puts out is directly related to how much airflow your motor is using. If you have a SMIC or a crappy intake, or it's a hot day you can run more boost and still have a lower airflow. On the flip side I could hit fuel cut at about 8psi on my old CA because I had a big turbo, ported head, and cams.
The Z32 MAF (since it flows more air at 5volts) dosn't suffor from the boost cut untill your making 500+hp. So if you upgrade your MAF you get around the problem.
PS that blurb from ND is talking about an S14 w/sr20det not the CA18DET.
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Movingviolation240
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'93 Lexus SC300 w/ SP66 turbo kit
Z32 and some sort of programer to fix it. Or better yet Z32 MAF and 555 injectors is pretty much 'stock' again. The MAF reads a lower voltage but the large inejctors allmost compleatly make up for it. It's not a good 'long term' fix and it's not safe to run high boost on, but it works for a while.
Or you could get a FCD, OR a reprogramed ECU
Or you could get a FCD, OR a reprogramed ECU