Zs Z wrote:An FMU basically is a crutch to aide the ecu so that the fuel pressure changes making your injectors squirt more fuel in based on boost pressure (or thats the understanding that I have had) It is not necessary but it certainly is not a bad thing to run and I would imagine it makes tuning less of a headache too.
your confusing an fmu with a 1:1 boost reference fuel pressure regulator. this i recommend and it replaces the stock fuel pressure regulator. an fmu raises the fuel pressure a ridiculous amount and its mounted after the stock fuel pressure regulator. it makes tuning less of a headache for an amature tuner and it is not a tune. it cannot adjust fuel entering the cylinder based on rpm, load, and boost level. if your tuning the stock ecm then there is no need for an fmu. exponentially increasing fuel pressure based on boost pressure is the 90"s way of doing things. back then, there was no other option. this is 2011 people.
Whalesac wrote:JOE L wrote:an fmu is not a tune so dont waste your money buying one. get it tuned or if your running low boost add an extra injector controller. these will be able to controll fuel entering the engine unlike an fmu which just exponentially dumps fuel into the engine.
No it doesn't. It increases rail pressure proportionally to manifold pressure, and as such, increases injector flow "relaively" linearly as well. This only becomes an issue when you fatigue the injectors prematurely by running very high rail pressures (i.e. high boost).
If your only choice for tuning is Alpha-N, an FMU would be a good addition. Without some form of boost reference, you can never tune an Alpha-N turbocharged engine well for all engine loads (this truth is even more evident on larger/laggier turbos). I don't know where people get this idea that the definition of "tune" is strictly changing some values in a computer.
lol. that is the definition of a tune. an fmu exponentally increases fuel rail pressure which is not a tune. it is not precise and it cant adjust fuel entering the engine dependant of rpm, load, and tps. the engine requires more or less fuel at different rpms and boost levels. only a tune can do this. therefore an fmu is not a tune. the next best thing to an actual ecm tune is an extra injector controller. these can control extra injectors based on rpm, tps and boost level. this type of system replaced the fmu because it can actually controll the amount of fuel entering the engine under boost.
an engine under boost requires different amounts of fuel at different rpms. the engine is most efficient at the rpm where max torque takes place and at this rpm is where the engine VE( volumetric efficiency) is at its max. this is the very point where the engine requires the most fuel. as you pass this rpm VE goes down because the engine is spinning to fast to fill the cylinder so less fuel is required even under boost.
example: a boosted 4 cylinder engine reaches max torque at 4000 rpm and the VE is at 110%. (this is the point where the injectors will feed the cylinders the most fuel) now the engine has increase its rpm past 4000 to 5000 rpm. VE is now 102% because the increased speed of the engine cannot fill the cylinder fast enough so the injectors are feeding the engine less fuel. now the engine is at 6000 rpm and the VE is 95%. the engine is spinning even faster so there is even less time for air to enter the engine. the injectors would feed the engine even less fuel.
THERE IS NO FMU IN THE WORLD THAT CAN COMPENSATE FOR THE ABOVE COMMENT SO FOR THE LAST F&^KING TIME AND FMU IS NOT A TUNE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
How about you post some pictures of your car with said turbo kit and hood exiting exhaust.
"Oil Leak ? What oil Leak ? Oh, Thats Just The Sweat From All The HorsePower!!"
JOE L wrote:Whalesac wrote:JOE L wrote:an fmu is not a tune so dont waste your money buying one. get it tuned or if your running low boost add an extra injector controller. these will be able to controll fuel entering the engine unlike an fmu which just exponentially dumps fuel into the engine.
No it doesn't. It increases rail pressure proportionally to manifold pressure, and as such, increases injector flow "relaively" linearly as well. This only becomes an issue when you fatigue the injectors prematurely by running very high rail pressures (i.e. high boost).
If your only choice for tuning is Alpha-N, an FMU would be a good addition. Without some form of boost reference, you can never tune an Alpha-N turbocharged engine well for all engine loads (this truth is even more evident on larger/laggier turbos). I don't know where people get this idea that the definition of "tune" is strictly changing some values in a computer.
lol. that is the definition of a tune. an fmu exponentally increases fuel rail pressure which is not a tune. it is not precise and it cant adjust fuel entering the engine dependant of rpm, load, and tps. the engine requires more or less fuel at different rpms and boost levels. only a tune can do this. therefore an fmu is not a tune. the next best thing to an actual ecm tune is an extra injector controller. these can control extra injectors based on rpm, tps and boost level. this type of system replaced the fmu because it can actually controll the amount of fuel entering the engine under boost.
Wow, you are completely clueless. You keep saying that an FMU increases fuel exponentially (I'm not sure you even know what that word means), so how about you explain to the class how an FMU actually works.
Tuning has existed for longer than EFI or computers have even been in existence.
JOE L wrote:an engine under boost requires different amounts of fuel at different rpms. the engine is most efficient at the rpm where max torque takes place and at this rpm is where the engine VE( volumetric efficiency) is at its max. this is the very point where the engine requires the most fuel. as you pass this rpm VE goes down because the engine is spinning to fast to fill the cylinder so less fuel is required even under boost.
example: a boosted 4 cylinder engine reaches max torque at 4000 rpm and the VE is at 110%. (this is the point where the injectors will feed the cylinders the most fuel) now the engine has increase its rpm past 4000 to 5000 rpm. VE is now 102% because the increased speed of the engine cannot fill the cylinder fast enough so the injectors are feeding the engine less fuel. now the engine is at 6000 rpm and the VE is 95%. the engine is spinning even faster so there is even less time for air to enter the engine. the injectors would feed the engine even less fuel.
THERE IS NO FMU IN THE WORLD THAT CAN COMPENSATE FOR THE ABOVE COMMENT SO FOR THE LAST F&^KING TIME AND FMU IS NOT A TUNE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Again you don't know what you're talking about. For one, there isn't a single cavalier on this board that is exceeding 100% VE at any RPM. What you see in the tuning program (you're probably refering to HPTuners) is an approximation to VE and it's useful to approximate high from a tuning standpoint, because it gives you more resolution. Furthermore, at approximately max VE, you don't see "max fuel". What you do see is max injector pulsewidth, because of the phenomenon you just described (i.e. cylinder filling). This is not even remotely the same as max fuel. Max fuel delivery occurs at approximately peak power, and it's because of this that you size your injectors to fall within the max power you are going to max
Onwards....An engine itself doesn't care what your throttle position is. All it cares about is mass flow, for which map based fueling is a much better approximation than Alpha-N for turbocharged vehicles. Tell me genius, using only an Alpha-N tune, how you control the fuel when there is very little inertia on the exhaust wheel while cruising at 3000+ RPMs, and you all of a sudden mash the peddle to 100% TPS....then again, you proabably don't understand the idea of wheel inertia either, so that probably fell on deaf ears.
I have no signiture
JOE L wrote:BuiltNBoosted wrote:JOE L wrote:an fmu is not a tune so dont waste your money buying one. get it tuned or if your running low boost add an extra injector controller. these will be able to controll fuel entering the engine unlike an fmu which just exponentially dumps fuel into the engine.
mine is working just fine... and making over 300whp...
with an fmu alone.... doubt it!!!
I don't think you have seen Vince's car..
just coveert to speed density with the gm supercharger tune and use that as a base tune. Then get a tuner to adjust it accordinally
GMR has got nothing on this
Not sure he can do that with his platform
Meh, not too terrible, should probably put an exhaust on it.
Any picture of a boosted LD9 is motivation to build my motor and finally boost mine.
"Oil Leak ? What oil Leak ? Oh, Thats Just The Sweat From All The HorsePower!!"
i started my down pipe to day i should be welding and wraping 2marrow
ok i have been setting up a turbo kit for my car piece by piece and im just wondering if it is possible to get the kit on the car with no tune if i run very low boost and dont beat on the car (2-3psi) and also i only plan on running 5 psi or so max. these my be stupid questions but this will be my first time turboing a car so i guess im wondering why you cant just get a wideband, 255lph fuel pump, injectors, and a fpr and make you own adjustments until its no longer running lean or will this not work? i know its not as precise as a tune but if the A/F ratio is in spec shouldnt it be fine for low boost? also can u make adjustments with an safc? not trying to sound like an idiot but im learning as i go and cant afford to buy an expensive tune that i wont know how to use lol
No amount of untuned boost is safe, its HPtunners or go old school and run an FMU or do both. You can do Fuel pump, bigger injectors, and HPtuners and be safe. safc wont work on our cars because fuel is not map based like the safc is designed for. you want to tune for around 11.5-1 for boost.
Umm, wow, nice...turbo kit....
~2014 New Z under the knife, same heart different body~
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2012 numbers - 4SPD AUTOMATIC!!
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