What's the skinny on NA-T with totally stock fuel/control?
12-14-11, 11:47 AM
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What's the skinny on NA-T with totally stock fuel/control?
Hey everyone,
Long time lurker but I've finally registered now that I've picked up a 92 sc300 5speed to play with. I've been around in the tuning scene for a little while. I've got a couple 3000GT VR4s and a Stealth TT. I've had 2 S2000s as well. I'm no stranger to boosting and doing things differently and weirdly. My favorite VR4 currently runs on totally stock computer and fuel and I have done the opposite of what most people do (in any car really) and have raised the compression from 8:1 to 10:1 lol. The engine is super responsive and I don't have to mess with tuning it, I love it. So the thought of going NA-T and retaining the "high" compression ratio really doesn't phase me.
Later on down the road once I really want to start making some power I'll probably do something like swap in a 2jzgte ecu along with the appropriate stock injectors and sensors and convert to MAP. I've read up on that mod and I'd like that kind of driveability and reliability that a factory system offers.
My real question is before I go that route what's up with just boosting at 6-7psi on the existing system without even a piggyback like an SAFC? I realize the ECU is not setup for boost timing wise, but I know I can dial back overall timing a bit with the distributor. Is an SAFC or something similar really necessary? I mean the car as it is has an airflow meter and isn't MAP based, which means that any additional airflow, be it intake/header/exhaust or mild turbo setup, shouldn't need any additional tuning as long as you remain within the limits of the injectors. Am I wrong here? I guess I can understand tuning a little at WOT to obtain a more ideal AFR for boost vs an AFR meant for NA. Is that really the biggest issue?
Long time lurker but I've finally registered now that I've picked up a 92 sc300 5speed to play with. I've been around in the tuning scene for a little while. I've got a couple 3000GT VR4s and a Stealth TT. I've had 2 S2000s as well. I'm no stranger to boosting and doing things differently and weirdly. My favorite VR4 currently runs on totally stock computer and fuel and I have done the opposite of what most people do (in any car really) and have raised the compression from 8:1 to 10:1 lol. The engine is super responsive and I don't have to mess with tuning it, I love it. So the thought of going NA-T and retaining the "high" compression ratio really doesn't phase me.
Later on down the road once I really want to start making some power I'll probably do something like swap in a 2jzgte ecu along with the appropriate stock injectors and sensors and convert to MAP. I've read up on that mod and I'd like that kind of driveability and reliability that a factory system offers.
My real question is before I go that route what's up with just boosting at 6-7psi on the existing system without even a piggyback like an SAFC? I realize the ECU is not setup for boost timing wise, but I know I can dial back overall timing a bit with the distributor. Is an SAFC or something similar really necessary? I mean the car as it is has an airflow meter and isn't MAP based, which means that any additional airflow, be it intake/header/exhaust or mild turbo setup, shouldn't need any additional tuning as long as you remain within the limits of the injectors. Am I wrong here? I guess I can understand tuning a little at WOT to obtain a more ideal AFR for boost vs an AFR meant for NA. Is that really the biggest issue?
12-14-11, 03:44 PM
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I'm going to have to agree with deathsled on his response...the question was whether or not it could be done not whether or not it was right to do.
I say put a wideband on it. I'm not going to just throw parts at my setup until I know for sure what needs to be upgraded.
I say put a wideband on it. I'm not going to just throw parts at my setup until I know for sure what needs to be upgraded.
12-14-11, 04:57 PM
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And how is not buying or modifying anything and utilizing the stock equipment already in place a MacGyver'd workaround?
I'm well aware of how much all the different piggyback systems cost. As I said I'm no stranger to the tuning world. I've been building and tuning cars for over a decade (hey I'm youngish)
I'm well aware of how much all the different piggyback systems cost. As I said I'm no stranger to the tuning world. I've been building and tuning cars for over a decade (hey I'm youngish)
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12-14-11, 05:02 PM
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12-14-11, 05:12 PM
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No, I've read that thread and the threads referenced within it already.
A guy running injectors 2x the stock size of course needs some sort of fuel control and is not the kind of example I'm looking for or the setup I'm asking about.
I'm not thanking you for that
A guy running injectors 2x the stock size of course needs some sort of fuel control and is not the kind of example I'm looking for or the setup I'm asking about.
I'm not thanking you for that
12-14-11, 06:24 PM
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I don't see a point to upgrading the injectors and fuel pump unless you actually need to - which could only be found out via a wide band and data logs.
I see the point why some people do it ahead of time, you never want to run out of fuel but it adds another added cost to the factor that may not be needed (for people like me, who really don't want to make 800 WHP on a daily).
I see the point why some people do it ahead of time, you never want to run out of fuel but it adds another added cost to the factor that may not be needed (for people like me, who really don't want to make 800 WHP on a daily).
12-14-11, 07:42 PM
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Put a wideband on it... You will probably see why. A NA engine MAF and ECU and stock components are not setup for the introduction of boost. What you're are asking the components to do is compensate for the correct afr. You might probably get away with the stock fuel pump (maybe also doing the 12v mod) but you will need just a bit more fuel. The stock ECU is not set up for it. You will probably have lean points in there as well when you hit boost despite it being the low end of boost or the ecu may try and compensate for it incorrectly. So if you don't want to upgrade your fuel system then get a wideband and monitor it... You should be around 11 for afr WOT or so.. anything higher you're leaning out. Afterwards then get a afc or something to push more out of the stock injectors.. Injectors are pretty cheap though so you could pony up for them and they wouldn't hurt your wallet....
Last edited by antonio356; 12-14-11 at 07:49 PM.
12-14-11, 07:54 PM
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See, I'm trying to understand why there would be lean spots or why one would need a piggyback to "push more out of the injectors".
The ECU knows how large the stock injectors are and how to utilize them. There is an airflow meter in the intake path that tells the engine EXACTLY how much air is being ingested. Regardless of whether or not the intake charge is being compressed or not seems like it would be irrelevant. Pretend for a moment I just bored and stroked the motor to 4.0L or something. The MAF is going to be reading all that extra air coming into the engine and the ECU should be adding fuel to compensate.
Are the stock maps in the ECU not robust enough to push the injectors to 80-90% duty cycle if the airflow demands so across different RPM ranges?
The ECU knows how large the stock injectors are and how to utilize them. There is an airflow meter in the intake path that tells the engine EXACTLY how much air is being ingested. Regardless of whether or not the intake charge is being compressed or not seems like it would be irrelevant. Pretend for a moment I just bored and stroked the motor to 4.0L or something. The MAF is going to be reading all that extra air coming into the engine and the ECU should be adding fuel to compensate.
Are the stock maps in the ECU not robust enough to push the injectors to 80-90% duty cycle if the airflow demands so across different RPM ranges?
12-14-11, 09:11 PM
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It really depends on if you're using a blow through method (to measure the added air) or a pull through (at least on a normal MAF car). The O2 sensors, etc should be enough to compensate without seeing boost.
The 12V vs 5V shouldn't make a difference being that the fuel pump should switch to 12V automatically based on TPS position.
It's sort of like a dry shot of nitrous, people are scared because of the horror stories - same holds true for boosted NA-T cars. I agree it's a better quality of a build with more insurance but it's not needed if you're not pushing the car.
The 12V vs 5V shouldn't make a difference being that the fuel pump should switch to 12V automatically based on TPS position.
It's sort of like a dry shot of nitrous, people are scared because of the horror stories - same holds true for boosted NA-T cars. I agree it's a better quality of a build with more insurance but it's not needed if you're not pushing the car.
12-14-11, 10:49 PM
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However, I am aware that switching from draw through to blow through often does require a small change in tune.
12-15-11, 02:58 AM
#15
simply put , would be a fast ticking timebomb..
ge ecu as you stated has zero ref for positive pressure.. retarding base timing to offset upper rpm timing will get you a poor idling and cruising car with super hot egt when you dont want it .. stock injectors is no go,, fic , safc the whole alphabet soup thing is old school thinking , for ge to perform and drive like stock standalone is the only way .. been there done that
ge ecu as you stated has zero ref for positive pressure.. retarding base timing to offset upper rpm timing will get you a poor idling and cruising car with super hot egt when you dont want it .. stock injectors is no go,, fic , safc the whole alphabet soup thing is old school thinking , for ge to perform and drive like stock standalone is the only way .. been there done that