Another Stock Mojave on 37s (Manual)

[JT1]

so yes and no, pressure starts increasing at 2800, its a setting in the software to activate the solenoid). However it takes a few rpms to get up to full pressure. There is also a slow pressure decay once under 2800 (once it turns off). My initial intent was to say stay away from 2800 with margin, so keeping it at 3k or 2500k keeps the pressure constant regardles of the actual pressure. (i.e. minimize on/off of the solenoid)

You mentioned the 3.6 scattering apart with SC's, do you have any technical details?

I've only heard of a few instances and some of them being from running a larger pulley. I'v taken data logs and saw max boost around 8psi. I know others have swapped out the rods as those were noted as the weak point for higher boost applications.

On mine the pressure starts ramping at 84mph (2950rpm) and is at 70 at 85mph. There is not much ramp up. At 2900 rpm I'm still at low pressure (34-38psi depending on temp).

It drops back to the lower pressure at 83.


No idea on the S/C, if I get desperate, I'll drop an LS in the thing.

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[piroman683]

On mine the pressure starts ramping at 84mph (2950rpm) and is at 70 at 85mph. There is not much ramp up. At 2900 rpm I'm still at low pressure (34-38psi depending on temp).

It drops back to the lower pressure at 83.


No idea on the S/C, if I get desperate, I'll drop an LS in the thing.

man, I'd love an LS!

I do wonder if the activation is more of a feedback and contral function. That is, there is an initial target based on engine load, pedal position, etc. then within a range of criteria it activates. For example, at WOT in 1st it knows the driver wants to rip, so itturns on 100 rpm sooner, or during a slower acceleration it might think the driver is just shifting normally at 3k so since there is low engine load/throttle position it desides not to fully activate it since it shifted sooner. This is my general conecern with overly complicated feedback and control systems in these particular case. But now you have me wondering, so I'll try to remember to do some data logging next time I'm driving it around. (currently in my shop waiting on some upgrades for an upcoming race in Mexico)

 

[Splenda]

Maybe one of you can explain to me why the 3.6l Pentastar oil pressure fluctuates between 30 psi and 70 psi. I know when the engine is cold, it runs around 70 psi until the engine warms up a little, but sometimes when I'm just driving along, the oil pressure spikes from 30 to 70 for no apparent reason. I read this and was wondering if this is the reason:

"The 3.6 Pentastar has a two stage oil pump. When you first start it up, it is in high stage, so that all of the oil circulates. High stage is approx. 99 PSI. Then it drops back to the low stage of 30's to 40. When your RPM reaches 3500, stage two kicks back in, to activate the piston cooling nozzles. This is normal for the 3.6 engine. When the oil pressure sensor fails, it fails and stays in high pressure mode."

 

[JT1]

man, I'd love an LS!

I do wonder if the activation is more of a feedback and contral function. That is, there is an initial target based on engine load, pedal position, etc. then within a range of criteria it activates. For example, at WOT in 1st it knows the driver wants to rip, so itturns on 100 rpm sooner, or during a slower acceleration it might think the driver is just shifting normally at 3k so since there is low engine load/throttle position it desides not to fully activate it since it shifted sooner. This is my general conecern with overly complicated feedback and control systems in these particular case. But now you have me wondering, so I'll try to remember to do some data logging next time I'm driving it around. (currently in my shop waiting on some upgrades for an upcoming race in Mexico)

The automatics seem to be different, and when I'm playing in the low gears, I don't have time to watch it, lol.

In 5th or 6th with the cruise on, I can tap it 1mph at a time and watch.. I try to stay out of that second stage just driving it.. so 84mph is my self governed top cruising speed.

 

[JT1]

Maybe one of you can explain to me why the 3.6l Pentastar oil pressure fluctuates between 30 psi and 70 psi. I know when the engine is cold, it runs around 70 psi until the engine warms up a little, but sometimes when I'm just driving along, the oil pressure spikes from 30 to 70 for no apparent reason. I read this and was wondering if this is the reason:

"The 3.6 Pentastar has a two stage oil pump. When you first start it up, it is in high stage, so that all of the oil circulates. High stage is approx. 99 PSI. Then it drops back to the low stage of 30's to 40. When your RPM reaches 3500, stage two kicks back in, to activate the piston cooling nozzles. This is normal for the 3.6 engine. When the oil pressure sensor fails, it fails and stays in high pressure mode."

RPM and/or load. Switchover is somewhere around 3K rpm.

 

[Splenda]

RPM and/or load. Switchover is somewhere around 3K rpm.

So, you're also saying it's best to stay below that 3000-3500 rpm threshold so that it stays in the lower pressure?

 

[JT1]

So, you're also saying it's best to stay below that 3000-3500 rpm threshold so that it stays in the lower pressure?

What @piroman683 were talking about are the transient times when maybe the actuators have switched to the high lobe cams, but the pressure wasn't fully built up.. the high lift cams are a sort of flat tappet design, where the low lifts are rollers.

Specifically, I don't want to be pushing 70psi at interstate cruise with essentially minor load on the engine.

 

[Splenda]

The oil pressure and TPMS are the things I monitor most with the information screen in the cluster. I use my radar detector as a speedometer. I had noticed that the oil pressure does weird things. I will be sure to stay away from that transient zone where it kicks into the higher pressure. Thanks for the info.

 

[piroman683]

What @piroman683 were talking about are the transient times when maybe the actuators have switched to the high lobe cams, but the pressure wasn't fully built up.. the high lift cams are a sort of flat tappet design, where the low lifts are rollers.

Specifically, I don't want to be pushing 70psi at interstate cruise with essentially minor load on the engine.

exactly, and i have not been able to find any iterature on what is the minimum pressure for the high lift mechinism to activate/deactive is.

 

[JT1]

exactly, and i have not been able to find any iterature on what is the minimum pressure for the high lift mechinism to activate/deactive is.

I'd really like to see those data logs if it tells us which cam (VVL) and what the pressure is with the data synced. If those cam lobes aren't active until 3200 rpm no matter what, I don't think we have an issue. If they are active at 2800, I can see why these things occasionally eat themselves. Should be simple enough to tune out, but still a fly ball to short center.

 

[piroman683]

I'd really like to see those data logs if it tells us which cam (VVL) and what the pressure is with the data synced. If those cam lobes aren't active until 3200 rpm no matter what, I don't think we have an issue. If they are active at 2800, I can see why these things occasionally eat themselves. Should be simple enough to tune out, but still a fly ball to short center.

oh hell yeah, i can definitely map and track that!

 

[JT1]

oh hell yeah, i can definitely map and track that!

I still think these engines would benefit from additional zinc in the oil, but most of the failures I've seen are on the roller first, then the "flat" which points to a materials or spec flaw.

 

[piroman683]

Found the data log from the dyno run I did, but it wont let me upload it so here's a snapshot.

I also had a loose grounding wire which was causing intermitent power surges that I was trying to diagnose (grounding wires of the cam sensors at the back of the engine) this is a snip of that log as well. What was happeneing is at 50% pedal the computer was inturperting it as only 25% throttle, but that eneded up being rooted in the cams not moving resulting in the throttle body not opening faster. but if I slammed on the pedal then all hell broke loose. Hard to show with only images

 

[Ding gus]

Found the data log from the dyno run I did, but it wont let me upload it so here's a snapshot.

I also had a loose grounding wire which was causing intermitent power surges that I was trying to diagnose (grounding wires of the cam sensors at the back of the engine) this is a snip of that log as well. What was happeneing is at 50% pedal the computer was inturperting it as only 25% throttle, but that eneded up being rooted in the cams not moving resulting in the throttle body not opening faster. but if I slammed on the pedal then all hell broke loose. Hard to show with only images

 

[Ding gus]

Well minor update. Stock mojave no longer on 37s.

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