atpena

Ok guys so a buddy of mine found me a #62 ecu for my Sr but its tuned for gt3071r turbo 550cc injectors and z32 maf. I was planing on doing a z32 maf and 550's already but I'm running a s14 t28 what I want to know is would There be a problem with me running a smaller turbo if its tuned for that gt3071? Please help thanks

atpena

anyone.....?

Kingtal0n

Here are the potential problems:

#1 you say its "tuned" but what that usually means is that somebody adjusted the fuel chracteristic for said maf/injectors and usually left the timing alone or screwed it up.
That means, even if the Air/Fuel ratio is dialed up correctly, even if its perfect, the ignition timing is still probably way off. And that can lead to serious problems long term.

#2 I assume you dont care about #1 and just want your car to run and drive. In which case, You could probably get it to work just fine. You will most likely need to adjust the fuel pressure, and you maybe even want a SAFC for fine tuning the idle characteristic (since Fuel Pressure would normally optimally be used to dial in the final A/F ratio of the engine at Wide Open Throttle which might leave your idle with something to be desired)

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inopsey

tell that to someone running a generic rom tune. all jwt/enthalpy ask for is the injector size and what maf is being used. why would that be?

blkvrtswp

You should be fine - but as with all ROM Tuned ECU's I recommend using a dyno or wideband O2 to verify that the AFR is proper before you push the turbo much.

fliprayzin240sx

Should be fine, it might run rich under WOT but the MAF should still read how much air is coming in so the ECU can make corrections for it.

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EsChassisLove

The t28 will not flow nearly as much a the 3071. You will be flooding the engine with fuel at WOT.

soft driving I think should be ok.

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Kingtal0n

Ah, but you seem to forget the car has a MAF sensor, which reads MASS OF AIR not BOOST pressure. So at 10psi on a T-28 and 10psi on a 3071, yeah lets say the 3071 moves more air.
That also means the maf will read to a higher load in the map, which results with more fuel.

Likewise, if the t-28 will want to move less air, it will read lower on the load scale in the ECU because the MAF will calculate the mass of air entering the engine.
Tuning with a MAF is like that. you can adjust such that any turbocharger can work. Until you exceed the maf sensor or the injectors.

Im not saying it wont be ultra rich at WOT either; it will probably be way off, most rom tunes start out far from ideal.
The real problem is the ignition timing. It seems like nobody knows what to set it at. The exception seems to be JWT, I have seen proper results from their ECU online, never seen one in person though, on a dyno.

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5.3/4l80e/turbo 240sx playthrough:
https://tinyurl.com/turbo240

Croustibat

This is a MAF system, not an alphaN. alphaN does not work on charged engine anyway... why cant you just shut up when you dont have a clue about what you are talking about ? His spooling zone wont be perfectly matched, and he just wont use the last 2 or 3 columns of his maps, leading him to run maybe a little bit too much timing and leaner than what it should run at WOT, and thats it... not much to worry about, and he certainly wont be flooding his engine...


TL;DR:
You are full of BS and dont know jackshite, so stfu, noob.

EsChassisLove

Are you always such a baby back bitch? Just curious lol


Edit-So running to much timing and also running leaner....cuz that's totally ok lol.

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Croustibat

With idiots that dont know jack, but pretend otherwise to increase their postcount, on something that can lead to quite expensive repairs ? Hell yes. Anytime. This is no video game dude, someone real is paying for parts here, and it clearly is not you.

You dont know an answer ? THEN DONT TRY TO GUESS. MORON.


I suggest you read what i wrote again, without removing words from my sentences. You might learn something if you try enough. "lol" .

Kingtal0n

Ive used alphaN on a V8 supercharged engine, crusti; just throwing that out there. They use the TPS it doesnt care what sort of atmosphere is presented to the combustion chambers. It was a commander 950 fwiw.

I wrote an auto tuning software for it too (using map sensor only though)



ah good old days. I wrote that software when I was 18 years old.
Also, take it easy man. this is the internet not serious business. Theres alot of misinformation on forums; its up to the users to decide whos full of what.

I won a free cookie at subway today. Its the small things in life.

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5.3/4l80e/turbo 240sx playthrough:
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godsmack

I'm not very knowledgeable when it comes to tunning. But would it make a difference since the bigger turbo will move a greater volume of air at the same pressure as the T28? This is my understanding right now but if I'm wrong let me know.

Kingtal0n

Forget about turbos. Think of engines. Engines move air. They move VOLUME of air. Air has a volume because temperature is more than nothing. If you change the temperature of air lower and lower the air molecules (alot of nitrogen gas in our atmosphere that is inert and some oxygen and you can google the rest of it) will squeeze closer and closer together.

And in the combustion chamber, those molecules, well, some of them (mostly the oxygen, or O2) react in the presence of vaporized hydrocarbons (if you are using gasoline, its carbon chains ranging from 6-9 carbons long. plus or minus) to combust in a manner that you hope will gently press against all surfaces and find the one that moves easiest (such as the surface of the piston).

The trick with engines when it comes to horsepower is reacting as much of this fuel and air together as you can, in a controlled manner that does not explode the engine apart in the process. So you want as many of those molecules as you can squeeze in the cylinder, in the proper ratios, with the proper ignition timing, reacting just fast enough to push the piston when the right time comes as far down as it goes. The process repeats of course.

Engines do this whether there is a turbocharger or not; The idea behind turbochargers is that they can squeeze the air molecules together closer, just like lowering the temperature can. but they can do it while the temperature is actually going up. Thats why we get boost pressure; its pressure above atmospheric- that is, the pressure generated by the air molecules as they bounce off their container, be it intercooler plumbing, or the cylinder walls or the intake manifold. Thats what gives pressure, air molecules bouncing off their container. It has NOTHING to do with the AMOUNT or MASS of air molecules in that container; That is why we can discount turbochargers when considering this scenario.

A maf sensor is able to measure the actual mass of air entering the engine. meaning it knows exactly (well, within reason) how many air molecules per unit time is entering the engine. From that conclusion it can accurately reason how much fuel should be injected to reach the desired Air/Fuel ratio as determined by the fuel map.

So turbocharger or not, supercharger or not, boost pressure or not; none of that matters. the maf sensor will accurately decide how many air molecules per unit time is entering the engine, and walaa you get an Air/Fuel Ratio. Keep in mind this changes on the fly because the computer has no actual idea how many fuel molecules are entering the engine. For instance, the injectors could get clogged up. the computer can only attempt to inject what it thinks is right. its OUR job to determine if the computer is doing its job correctly; we can do this many ways, but my favorite is by looking at a wideband (installed a good 3 feet away from the turbocharger turbine) and an EGT gauge (installed as close to the combustion chamber as I can get it)

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Kingtal0n

Another way to answer this question ( since you did not mention MAF sensor or fueling )

#2 explanation:

A larger turbocharger moves more air. Everybody says that. but lets examine where this "extra air" is coming from with regards to the actual compressor.

Imagine a T-28 and a 3071 turbocharger. The T-28 is "smaller". Lets turn the flow rate of both to 100CFM. Guess what? Both turbochargers will move approx the same amount of airflow. Keep turning up the flow rate of both turbochargers. 200cfm. 300cfm. 400cfm. Keep going. As you keep turning up the flow rate, eventually, the compressor will give up. In other words, they have a maximum flow rate that they can not (should not) exceed for many reasons. One reason is the amount of heat being added to the air as it being compressed can actually reduce the overall number of air molecules per unit time entering the engine. which would decrease horsepower, despite an increase in boost pressure.

So the trick is having the properly sized compressor to match your engines maximum desired flow rate at its peak desired horsepower. In other words, install a 400 horsepower turbocharger if you want 400 horsepower. The engine must be able to actually flow 400 horsepower worth of air at the desired boost pressure within a tolerable range of temperature for the fuel being used; 93 octane gasoline has been known to give serious trouble when the boost pressure is 25 or 28psi in an SR20DET engine for instance. Really, we need to calculate backwards from the engines capability to find it's maximum flow rate first. Then figure what an increase in atmospheric pressure would do to that flow rate. Factoring in adiabatic efficiency, which in physical chemistry terms means that there is no heat exchanged between the system and the surroundings, quote "the change of the state of the system was dependent only on the amount of work done on the system, not on the particular type of work or how it was done" (page 54, the first law: energy is conserved)- we will lose some air molecules per unit time to the laws of thermodynamics as the compressor does it's job. How WELL that it does its job is the key, as compressing air and generating heat can be a pointless process if the amount of heat generated spreads the air molecules out farther than the increase in pressure moves them together. You WANT them to move closer together, but there is GOING to be an increase in temperature regardless, which will attempt to move them apart. When a compressor is efficient, near the center of it's compressor map, it tends to move the air molecules closer together and the heat generated, while moving them apart some, moves them apart less than the increase in pressure moved them closer together. As the compressor moves off the right of it's compressor map (this is where the size of the compressor matters), the amount of heat generated moves them farther and farther apart regardless of how much pressure you try to make.

A larger compressor has more flow rate to give before it runs off the right of it's map. it can flow more air molecules per unit time without adding a substantial amount of temperature increase to them in the process. So when the T-28 starts to run out of breath, the horsepower stops there for it because even if the boost pressure is the same on both turbochargers, the larger turbo can flow the same amount of air without adding so much heat to it, thereby keeping the air molecules closer together.
Thats where the maf sensor comes in and realizes that there are more air molecules per unit time entering the engine, and the ECU should inject more fuel.

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5.3/4l80e/turbo 240sx playthrough:
https://tinyurl.com/turbo240

godsmack

Lots of good info there. I know about most of it since my dad taught me about that stuff while tuning carbs. I was just unsure of how the maf really measured the air. Wasn't sure if it was the pressure or the volume of air.

So according to what I just read there, the maf will read the volume and not the pressure. Which in turn transfering from turbo to turbo as long as the maf is up to the task of the amount of air flowing through, and the tune is good, then it should not really matter what turbo you have bolted up, as long as you are running what the tune is tuned for.

Did I get that right?

Kingtal0n

The maf reads mass. "mass air sensor". why dont you google up on how maf sensors work?
there is a hot wire involved and a resistance and voltage involved. It seems complex but it measure mass of air. not volume or pressure.
I like to think of it as reading air molecules per unit time, as I have mentioned frequently.

MAP sensors read pressure.

And nothing that I am aware of reads volume of air.

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fliprayzin240sx

Basically, yes...remember where the MAF is located at? Its before the turbo. So how ever much air the turbo can suck in, is all the MAF wil measure. ECU uses that to calculate how much fuel is needed.

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atpena

Thanks for the help guys I'm gonna go ahead and try out the setup, just gonna daily baby it for now till I can get it tuned for my own setup thanks again a lot of great info



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Croustibat

bold > no. MAF = Mass Air Flow sensor. It measures the mass, which is constant. Neither volume nor pressure can represent the air quantity in an engine; a volume of hot air will always carry less air than a volume of cold air, at the same pressure. A volume at 1bar absolute also contains half of the air quantity there would be in a 2bar absolute volume of identical size and temperature.

when air is compressed, it is supposed to have more air molecules in the same volume; but heat tends to do the opposite, and compressing "adds heat".

thus there are 2 ways to measure the air entering our engines:

the MAF, which measures mass airflow , or the map system. MAP measure absolute pressure, and it also needs a temperature sensor to get the real air quantity entering (aka the mass).

But you understood the concept somewhat. The thing is, turbos will spool differently, at different mass air, so you need to adapt the maps to turbo specially in these zones when changing turbos.

That and more mass of air requires more fuel and less timing, but ECUs use an interpolation system which when programmed correctly can fit safely bigger/ smaller turbos. It wont have the best performance of course, but it should be ok.

So Make Like

this thread started out as a typical help thread, but ended up being a good read. thanks.