TRD fmu or Free fmu?
02-14-2003, 01:41 PM
#21
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Originally posted by ravencr
I'm going to have the 370cc's like we have discussed, so what's the best combo, money aside?
Chris
I'm going to have the 370cc's like we have discussed, so what's the best combo, money aside?
Chris
Split Second FTC
305cc injectors
Walbro 190 LPH fuel pump
Free FMU
02-14-2003, 01:54 PM
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I know what he's been getting at, and I'm wondering how to get the additional 15 psi of fuel pressure that he talks about the Free FMU missing out on. I'm wondering if the combination you mention plus the Cartech, Paxton, or Vortech FMU's would cure this 15 psi loss at max boost. Seems like a lot of lost fuel to me. But, I could easily be wrong.
Chris
Chris
02-14-2003, 02:07 PM
#23
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The TRD FMU that was included in the original kits would give you 65 PSI at full boost until the stock pump petered out then it will fall back to 50 PSI. This was with the stock injectors. A BAP or pump upgrade would maintain the 65 PSI at max boost and all RPMs.
The Free-FMU will give you around 50 PSI with the stock pump and injectors as max boost.
The Free-FMU with 305cc injectors will give you 50 PSI at full boost until the pump starts to peter out and then pressure will drop. On my 96 that would be around 38 PSI, on my 97 with 14,000 miles on it would be around 43 PSI.
The Free-FMU with the 305cc injetors and the Walbro 190 LPH pump would give around 50 PSI at max boost and would remain stable at all RPMs. This would also be the same for the BAP.
Of course your results may vary...
Tell the truth, you are just dying to put one of those Band-Aid things on your truck arn't you?? Come on, be honest.:rolleyes:
Gadget
www.GadgetOnline.com
The Free-FMU will give you around 50 PSI with the stock pump and injectors as max boost.
The Free-FMU with 305cc injectors will give you 50 PSI at full boost until the pump starts to peter out and then pressure will drop. On my 96 that would be around 38 PSI, on my 97 with 14,000 miles on it would be around 43 PSI.
The Free-FMU with the 305cc injetors and the Walbro 190 LPH pump would give around 50 PSI at max boost and would remain stable at all RPMs. This would also be the same for the BAP.
Of course your results may vary...
Tell the truth, you are just dying to put one of those Band-Aid things on your truck arn't you?? Come on, be honest.:rolleyes:
Gadget
www.GadgetOnline.com
02-14-2003, 02:44 PM
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So, I guess I can't get a straight forward answer whether it will actually boost it up to 65 psi by adding the additional FMU to the free FMU with all the other fuel mods, right?
Chris
Chris
02-14-2003, 04:54 PM
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02-14-2003, 04:59 PM
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Gadget,
Am I missing something here or what? I'm doing the 370cc injectors, already installed the larger fuel pump, th TRD supercharger, SMT-6, and the free fmu at least, but should I go ahead and add the aftermarket FMU too???????????????
Am I stupid or something? How's this a band-aid fix if I'm doing everything you recommend and I'm trying to see if the additional FMU will help even more. How's that Band-aid?
Chris
Am I missing something here or what? I'm doing the 370cc injectors, already installed the larger fuel pump, th TRD supercharger, SMT-6, and the free fmu at least, but should I go ahead and add the aftermarket FMU too???????????????
Am I stupid or something? How's this a band-aid fix if I'm doing everything you recommend and I'm trying to see if the additional FMU will help even more. How's that Band-aid?
Chris
02-14-2003, 05:50 PM
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You certainly are not stupid. Don't think that for a minute.
I have just been unsuccessful in my communications to clear up the mystery. That is my failing.
When the engineers design the vehicle they have a list of specs that it must meet. To meet those specs they figure that the vehicle will need an engine of a certain power level to meet the specs they have been provided. In dreaming up the engine they design a fuel and engine control system to meet its design specs. They don't over build anything to any great degree because that cost money. The engineers when they designed this engine, fuel system and control system never dreamed that a whole bunch of really whacky people like us would be bolting superchargers on them so the fuel and engine control system was never designed to support it.
No comes the aftermarket crowd. They design a supercharger that bolts up really nice, but there are other things to consider like the fuel and engine control system. How do you get an injector to flow more fuel then it was ever intended to so you can supply more fuel to support the aftermarket supercharger?? There are all kinds of ways to do it. Some cheap, some expensive. Most of these aftermarket companies go the cheap route and Band Aid the issue by installing a pressure rising Fuel Management Unit. By increasing the fuel pressure more fuel will flow from the injectors that are really do small to start with.
These are usually cheap mechanical devices and really don't work all that well. You can get to much gas flowing when you don't need it and not enough when you do. Or not enough all the time or even to much all the time. They are never just right, because it is just a stupid mechanical device with springs in it.
A better answer is to install the proper size fuel injectors and an electronic control unit so you can precisley tune the fuel curve to meet your new needs of the aftermarket supercharger. Doing this electronically is much more precise and provides repeatable consistant results time and time again. Once you complete the initial tune it can be drive and forget while still passing tail pipe emmission tests.
Yes you do want to connect the fuel pressure regulator to the boost port with the proper size injectors so that the fuel pressure will always be in a consistant relationship to manifold pressure so you remove that dynamic from your tuning scheme. It just makes things much easier and that is why most all fuel pressure regulators in the world on fuel injected engines are connected to the manifold. Why Toyota did it differently on a few models of the 3.4 is a real mystery and it is not even reflected in the shop manuals.
Now, since you are going to be installing larger injectors you do not need to jack the fuel pressure way up to get more fuel to flow. You will have more then enough injector and fuel flow capacity to use a standard fuel pressure and flow enough fuel to meet your needs. It is so much easier to change a couple of numbers on a data table then it is to swap springs out of a mechanical FMU and just hope to get somewhere in the neighborhood of being close.
So, with the proper size injectors you do not need nor should you even consider using a pressure increasing aftermarket FMU. If you do you are going to really hink things up and make this much more complicated then they need to be.
Just say no!
Gadget
www.GadgetOnline.com
I have just been unsuccessful in my communications to clear up the mystery. That is my failing.
When the engineers design the vehicle they have a list of specs that it must meet. To meet those specs they figure that the vehicle will need an engine of a certain power level to meet the specs they have been provided. In dreaming up the engine they design a fuel and engine control system to meet its design specs. They don't over build anything to any great degree because that cost money. The engineers when they designed this engine, fuel system and control system never dreamed that a whole bunch of really whacky people like us would be bolting superchargers on them so the fuel and engine control system was never designed to support it.
No comes the aftermarket crowd. They design a supercharger that bolts up really nice, but there are other things to consider like the fuel and engine control system. How do you get an injector to flow more fuel then it was ever intended to so you can supply more fuel to support the aftermarket supercharger?? There are all kinds of ways to do it. Some cheap, some expensive. Most of these aftermarket companies go the cheap route and Band Aid the issue by installing a pressure rising Fuel Management Unit. By increasing the fuel pressure more fuel will flow from the injectors that are really do small to start with.
These are usually cheap mechanical devices and really don't work all that well. You can get to much gas flowing when you don't need it and not enough when you do. Or not enough all the time or even to much all the time. They are never just right, because it is just a stupid mechanical device with springs in it.
A better answer is to install the proper size fuel injectors and an electronic control unit so you can precisley tune the fuel curve to meet your new needs of the aftermarket supercharger. Doing this electronically is much more precise and provides repeatable consistant results time and time again. Once you complete the initial tune it can be drive and forget while still passing tail pipe emmission tests.
Yes you do want to connect the fuel pressure regulator to the boost port with the proper size injectors so that the fuel pressure will always be in a consistant relationship to manifold pressure so you remove that dynamic from your tuning scheme. It just makes things much easier and that is why most all fuel pressure regulators in the world on fuel injected engines are connected to the manifold. Why Toyota did it differently on a few models of the 3.4 is a real mystery and it is not even reflected in the shop manuals.
Now, since you are going to be installing larger injectors you do not need to jack the fuel pressure way up to get more fuel to flow. You will have more then enough injector and fuel flow capacity to use a standard fuel pressure and flow enough fuel to meet your needs. It is so much easier to change a couple of numbers on a data table then it is to swap springs out of a mechanical FMU and just hope to get somewhere in the neighborhood of being close.
So, with the proper size injectors you do not need nor should you even consider using a pressure increasing aftermarket FMU. If you do you are going to really hink things up and make this much more complicated then they need to be.
Just say no!
Gadget
www.GadgetOnline.com
02-14-2003, 09:01 PM
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Now that was a great detailed response, and as always I always love to hear your responses. You've been great as always.
Sort of a quick questions sort of on this same subject. I've been told it's really hard to program the ECU during Closed Loop. Trying to richen things up only causes the O2 sensor to react and send the signal to the ECU to lean it back out. Is this true? CAn we only really tune the Open Loop part, which from what I'm gathering is over 80% throttle?
Chris
Sort of a quick questions sort of on this same subject. I've been told it's really hard to program the ECU during Closed Loop. Trying to richen things up only causes the O2 sensor to react and send the signal to the ECU to lean it back out. Is this true? CAn we only really tune the Open Loop part, which from what I'm gathering is over 80% throttle?
Chris
12-13-2009, 10:42 AM
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Ok I'm way behind the curve here. Every time I read Gadget's site again, I learn more. So the free FMU is great under boost. You lose pressure under vacuum but the motor isn't under power anyway so it sounds like a good trade off. The TRD and third party FMUs seem to be worthless.
Would the upgraded pump be of any use with stock injectors?
Would 305cc injectors and the pump be of any use with the stock electronics or would it trip codes and generally be a mess?
Is the URD 7th inj kit the best choice? I have AFR meters and not O2 sensors.
The reason I ask, is my truck runs pretty well but I don't want it burn up the cats or anything else. It doesn't see redline to much. I mostly use the extra power for towing so 4000 rpm seems to be my usual "redline".
Does the stock fuel system keep up at 4000 rpm?
I paid under $700 for my SC. The injector kits are $1000... Still all cheaper than getting a newer tow vehicle with the 4.0 or V8 and start mods all over.
TIA
Would the upgraded pump be of any use with stock injectors?
Would 305cc injectors and the pump be of any use with the stock electronics or would it trip codes and generally be a mess?
Is the URD 7th inj kit the best choice? I have AFR meters and not O2 sensors.
The reason I ask, is my truck runs pretty well but I don't want it burn up the cats or anything else. It doesn't see redline to much. I mostly use the extra power for towing so 4000 rpm seems to be my usual "redline".
Does the stock fuel system keep up at 4000 rpm?
I paid under $700 for my SC. The injector kits are $1000... Still all cheaper than getting a newer tow vehicle with the 4.0 or V8 and start mods all over.
TIA
Last edited by LarsDennert; 12-13-2009 at 10:47 AM.
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