JWT Twin Turbo
#136
02-02-2006, 09:57 PM
Apparently the JWT kit uses stock injectors and relies on a rising rate FMU for fueling, along with a standard piggy-back MAF and crank angle signal spoofer for "fine tuning" of fuel and timing. 
While the hardware looks good, I'm not a fan of FMU-based tuning. Been there done that with previous setups. Running such elevated fuel pressures is never a good thing. But I can understand where they're coming from. By retaining stock injectors and base fuel pressure off-boost they should be able to pass emissions testing without too much trouble...
It sounds like there are some JWT kits out there running well for long periods, so that's good. But it's 2006 dammit and for $7k you should have a much better management solution.
While the hardware looks good, I'm not a fan of FMU-based tuning. Been there done that with previous setups. Running such elevated fuel pressures is never a good thing. But I can understand where they're coming from. By retaining stock injectors and base fuel pressure off-boost they should be able to pass emissions testing without too much trouble...
It sounds like there are some JWT kits out there running well for long periods, so that's good. But it's 2006 dammit and for $7k you should have a much better management solution.
#137
02-03-2006, 08:23 PM
I heard a rumor that the JWT kit relocates the sensor element of the MAF in to a larger diameter housing. Can anybody verify or comment on this? It's not clear from the pictures. I doubt this is the case because it would take extensive massaging of the load maps to be able to run stock injectors with a larger MAF. It's usually coupled directly with correspondingly larger injectors.
#138
02-04-2006, 04:13 AM
Here is some good reading for you Marty......................
http://www.my350z.com/forum/showthread.php?t=167710
http://www.my350z.com/forum/showthread.php?t=167513
http://www.my350z.com/forum/showthread.php?t=164431
http://www.my350z.com/forum/showthread.php?t=159840
http://www.my350z.com/forum/showthread.php?t=167710
http://www.my350z.com/forum/showthread.php?t=167513
http://www.my350z.com/forum/showthread.php?t=164431
http://www.my350z.com/forum/showthread.php?t=159840
#139
02-04-2006, 04:59 AM
What am I looking for exactly? I saw some dyno charts. Wonderful. How about some air/fuel charts along side each dyno chart, along with the fuel pressures and injector duty cycles?
And has there been any real research to back up that the OEM MAF maxes out at lower airflow rates when it is in a pressurized pipe than when it is at a pipe under low pressure? This goes against anything I've seen. MAFs keep a constant temperature difference between the sensor element and the air, and measure the amount of heat flow required to keep this constant temperature difference. Basically it is a measurement of the number of molecules coming in contact with the sensor element, it shouldn't care much about the ambient pressure. When I measured MAF voltages on my last car with the sensor both pre and post turbo, I saw the same voltage versus airflow curves. But if the Nissan MAF differs in this respect I'm all ears to hearing about it.
What concerns me is the fuel-pressure based tuning. At 400 whp, you're looking at roughly an 80% increase in power (1.80 times stock), which is about an 80% increase in airflow. To even keep AFRs similar to stock at stock duty cycles, you'll need an increase in fuel pressure of (1.80)^2 = 3.24 times stock. Assuming the stock system runs ~3 bar, that's a peak pressure of ~9.72 bar = 141 psi. Injectors aren't designed to operate at those pressures. Most will, and I've done it before, but it's not ideal.
And assuming you're using something equivalent to the Walbro 255 LPH HP pumps, they won't even hit those fuel pressures at any appreciable fuel flowrate. So chances are the injector duty cycles are astronomical and the fuel pump pressure is being set directly by the fuel flowrate in to the motor. I don't generally like operating my motors at this bleeding edge of safety in the fueling department. At this point if airflow increases, AFR increases, and there isn't anything you can do about it.
But if I'm completely off and you're able to achieve very low AFRs at less than maximum duty cycles at reasonable fuel pressures, then by all means please correct me and share your data. I love all of the JWT hardware (the Garrett turbos, piping, intercoolers, downpipes, etc) but am a bit concerned about the management, that's all.
And has there been any real research to back up that the OEM MAF maxes out at lower airflow rates when it is in a pressurized pipe than when it is at a pipe under low pressure? This goes against anything I've seen. MAFs keep a constant temperature difference between the sensor element and the air, and measure the amount of heat flow required to keep this constant temperature difference. Basically it is a measurement of the number of molecules coming in contact with the sensor element, it shouldn't care much about the ambient pressure. When I measured MAF voltages on my last car with the sensor both pre and post turbo, I saw the same voltage versus airflow curves. But if the Nissan MAF differs in this respect I'm all ears to hearing about it.
What concerns me is the fuel-pressure based tuning. At 400 whp, you're looking at roughly an 80% increase in power (1.80 times stock), which is about an 80% increase in airflow. To even keep AFRs similar to stock at stock duty cycles, you'll need an increase in fuel pressure of (1.80)^2 = 3.24 times stock. Assuming the stock system runs ~3 bar, that's a peak pressure of ~9.72 bar = 141 psi. Injectors aren't designed to operate at those pressures. Most will, and I've done it before, but it's not ideal.
And assuming you're using something equivalent to the Walbro 255 LPH HP pumps, they won't even hit those fuel pressures at any appreciable fuel flowrate. So chances are the injector duty cycles are astronomical and the fuel pump pressure is being set directly by the fuel flowrate in to the motor. I don't generally like operating my motors at this bleeding edge of safety in the fueling department. At this point if airflow increases, AFR increases, and there isn't anything you can do about it.
But if I'm completely off and you're able to achieve very low AFRs at less than maximum duty cycles at reasonable fuel pressures, then by all means please correct me and share your data. I love all of the JWT hardware (the Garrett turbos, piping, intercoolers, downpipes, etc) but am a bit concerned about the management, that's all.
Last edited by MechEE; 02-04-2006 at 07:47 PM.
#140
02-06-2006, 01:11 AM
#141
02-06-2006, 02:33 AM
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Originally Posted by MechEE
What am I looking for exactly? I saw some dyno charts. Wonderful. How about some air/fuel charts along side each dyno chart, along with the fuel pressures and injector duty cycles?
And has there been any real research to back up that the OEM MAF maxes out at lower airflow rates when it is in a pressurized pipe than when it is at a pipe under low pressure? This goes against anything I've seen. MAFs keep a constant temperature difference between the sensor element and the air, and measure the amount of heat flow required to keep this constant temperature difference. Basically it is a measurement of the number of molecules coming in contact with the sensor element, it shouldn't care much about the ambient pressure. When I measured MAF voltages on my last car with the sensor both pre and post turbo, I saw the same voltage versus airflow curves. But if the Nissan MAF differs in this respect I'm all ears to hearing about it.
What concerns me is the fuel-pressure based tuning. At 400 whp, you're looking at roughly an 80% increase in power (1.80 times stock), which is about an 80% increase in airflow. To even keep AFRs similar to stock at stock duty cycles, you'll need an increase in fuel pressure of (1.80)^2 = 3.24 times stock. Assuming the stock system runs ~3 bar, that's a peak pressure of ~9.72 bar = 141 psi. Injectors aren't designed to operate at those pressures. Most will, and I've done it before, but it's not ideal.
And assuming you're using something equivalent to the Walbro 255 LPH HP pumps, they won't even hit those fuel pressures at any appreciable fuel flowrate. So chances are the injector duty cycles are astronomical and the fuel pump pressure is being set directly by the fuel flowrate in to the motor. I don't generally like operating my motors at this bleeding edge of safety in the fueling department. At this point if airflow increases, AFR increases, and there isn't anything you can do about it.
But if I'm completely off and you're able to achieve very low AFRs at less than maximum duty cycles at reasonable fuel pressures, then by all means please correct me and share your data. I love all of the JWT hardware (the Garrett turbos, piping, intercoolers, downpipes, etc) but am a bit concerned about the management, that's all.
And has there been any real research to back up that the OEM MAF maxes out at lower airflow rates when it is in a pressurized pipe than when it is at a pipe under low pressure? This goes against anything I've seen. MAFs keep a constant temperature difference between the sensor element and the air, and measure the amount of heat flow required to keep this constant temperature difference. Basically it is a measurement of the number of molecules coming in contact with the sensor element, it shouldn't care much about the ambient pressure. When I measured MAF voltages on my last car with the sensor both pre and post turbo, I saw the same voltage versus airflow curves. But if the Nissan MAF differs in this respect I'm all ears to hearing about it.
What concerns me is the fuel-pressure based tuning. At 400 whp, you're looking at roughly an 80% increase in power (1.80 times stock), which is about an 80% increase in airflow. To even keep AFRs similar to stock at stock duty cycles, you'll need an increase in fuel pressure of (1.80)^2 = 3.24 times stock. Assuming the stock system runs ~3 bar, that's a peak pressure of ~9.72 bar = 141 psi. Injectors aren't designed to operate at those pressures. Most will, and I've done it before, but it's not ideal.
And assuming you're using something equivalent to the Walbro 255 LPH HP pumps, they won't even hit those fuel pressures at any appreciable fuel flowrate. So chances are the injector duty cycles are astronomical and the fuel pump pressure is being set directly by the fuel flowrate in to the motor. I don't generally like operating my motors at this bleeding edge of safety in the fueling department. At this point if airflow increases, AFR increases, and there isn't anything you can do about it.
But if I'm completely off and you're able to achieve very low AFRs at less than maximum duty cycles at reasonable fuel pressures, then by all means please correct me and share your data. I love all of the JWT hardware (the Garrett turbos, piping, intercoolers, downpipes, etc) but am a bit concerned about the management, that's all.
yeah, what he said...and like to hear their response
but seriously, good points.......that's why i'm looking into the turbonetics single that'll come with walborro 255s and pre-tuned to about 380-400 right out of the box on stock internals.........plug and play iirc...
#145
02-08-2006, 04:28 AM
Originally Posted by caelric
Seriously, I would just like an update on the CARB status, and when/if JWT expects approval.
Dave
Dave
#146
02-09-2006, 07:03 PM
#147
02-09-2006, 10:29 PM
Originally Posted by MechEE
Anybody tune JWT kits for our cars that actually knows something about the AFR curves / injector duty cycles / fuel pressures? Or are the cars tuned blind?
Blind?? what?...
Are you trying to say that Jim Wolf and Clark at JWT and Mark at VRT do not know about AFR curves, injectors, and fuel pressure, or how to tune this kit???
VRT installed and tuned my jwt kit (20,000+ miles ago) and there is absolutely NO problems with it.
Last edited by Native1; 02-09-2006 at 10:32 PM.
#148
02-10-2006, 12:15 AM
Originally Posted by Native1
Blind?? what?...
Are you trying to say that Jim Wolf and Clark at JWT and Mark at VRT do not know about AFR curves, injectors, and fuel pressure, or how to tune this kit???
VRT installed and tuned my jwt kit (20,000+ miles ago) and there is absolutely NO problems with it.
Are you trying to say that Jim Wolf and Clark at JWT and Mark at VRT do not know about AFR curves, injectors, and fuel pressure, or how to tune this kit???
VRT installed and tuned my jwt kit (20,000+ miles ago) and there is absolutely NO problems with it.
1) VRT does not monitor all of these values (I hope at least AFR) and so can not comment on them, or
2) VR6 does monitor these values but whoever posts in the forum is not technically aware of them or their significance and therefore doesn't want to risk posting anything about it, or
2) VRT does monitor them but doesn't want to share because they are not ideal, so for them it's better to just keep it secret
#150
02-11-2006, 02:57 AM
Originally Posted by MechEE
I'm just calling out for people that know something about the tuning of the kit. I'm sure JWT is very aware of that data for the car. Is VRT? Not necessarily, they just have to play with the SplitSecond piggyback. But if they are, I would have assumed that they would have chimed in to share since they've posted in the thread already. Since the kit is supposedly so well designed, they should easily be able to defend any design choices. So I am left to assume that either:
1) VRT does not monitor all of these values (I hope at least AFR) and so can not comment on them, or
2) VR6 does monitor these values but whoever posts in the forum is not technically aware of them or their significance and therefore doesn't want to risk posting anything about it, or
2) VRT does monitor them but doesn't want to share because they are not ideal, so for them it's better to just keep it secret
1) VRT does not monitor all of these values (I hope at least AFR) and so can not comment on them, or
2) VR6 does monitor these values but whoever posts in the forum is not technically aware of them or their significance and therefore doesn't want to risk posting anything about it, or
2) VRT does monitor them but doesn't want to share because they are not ideal, so for them it's better to just keep it secret
Why are you so skeptical... (hate much)
Believe me pal, VRT does know how to tune this kit very well. Do you think that JWT would intrust VRT with the installing and tuning of some of THE first of this highly anticapated tt kit if they did not know what they are doing?? I have seen them (Mark the tuner) do it time and time again on my car and on severall other customers cars, they do take in to account all tuning aspects (AFR, fuel pressure, injector duty cycles, timing, etc.). I do not know all there is to know about these TT set ups and tuning them, However I do know that VRT is not able to post too much here in the way of specs on these public message boards, they are asked not too "yet" by JWT themselves.
Last edited by Native1; 02-11-2006 at 03:06 AM.