Oil pressure dropping at higher RPM - need help

[uhcoog1]

Data is from data logs (aside from oil temp- dash gauge).

Sensor 1 is oil pressure post filter.

2nd gear pull on street.

3rd gear pull on street. Last of day. Oil maybe slightly warmer?

 

[uhcoog1]

A_Harman- factory bearing specs above (looks like we posted at almost the same time).

last motor was a stock 6.1 that was pulled and sold. New motor is ~100 rwhp more. Unfortunately I was not logging oil pressures at the time.

 

[uhcoog1]

Previously acquired data- on both sides of a -10 check valve:

Max psi:
67 psi pre check valve
50 psi post check valve
RPM: 195*, 170*1, 170*2,
3000: 61/45 (63/48) nd/nd
4000: 56/42 (56/44) 63/48
5000: 61/44 (59/45) 59/46
5500: 55/41 (58/45) 57/44
6000: 57/43 (46/38) 51/41
6500: 56/43 (48/39) 55/42
Cold oil, 4500 rpm: 71/53

I ditched the check valve. I'll let the filter drain back be the accusump's check valve.

Based on what I'm seeing, it looks like I'm getting better pressure higher with hotter oil (acting like lighter weight oil). Course I don't know what 30wt at 170*f is comparable to...

 

[uhcoog1]

previous accusump plumbing. Have since bypassed cooler and check valve (and capped accusump line for clean data):

 

[A_Harman]

Oh, that's in-car data. Nice data package.
Oil pressure was lower in the 3rd-gear pull, but was more stable over the ~11 seconds of acceleration. You can see the oil pressure dropped when you opened the throttle, but it recovered and stayed stable to the max engine speed.

Here is an example of logger data I get out of my Corvette:
http://www.bobistheoilguy.com/forums/ubb...roa#Post3311220

 

[uhcoog1]

That's some solid data you have! I like it! What data acquisition system are you using? Mine is all through megasquirt MS3x. At some point I'll need to add more sensors - I only have 3 generic ports currently wired, but it can handle like 16. So for the time being, I'll be swapping between oil pressures 1&2 (pre and post filter- for accusump data), fuel pressure, and two linear potentiometers (one front left, one rear left) to see how much lift I'm experiencing.

What is interesting is you're never over 40-45 psi on track. Makes me feel better about my current pressures. I know it's not apples to apples, but it's nice to know someone is living on the road course at less than 10 psi per 1,000 rpm.

I have a gigantic oil cooler. I will leave it bypassed for my jan24-25 track day at TWS. Weather is supposed to be in the 40's and 50's. Last year at the big bend open road race I crested 220-230*F, which is the hottest I've had the oil temps.

 

[A_Harman]

That is data I get out of the AEM fuel injection system. I can log up to 16 channels at varying rates, depending on how much running time I want to store. The AEM box comes with 512k of storage. I have a 2-axis accelerometer in the car that is input to two unused pressure channels, so I can see what my acceleration, braking, and turning G's are. I would like to be able to log oil temperature, but the engine doesn't have any extra ports in the main oil gallery after the filter. I still have the OE oil temp sensor active so I can monitor it on my dash while on track.

Lap average oil pressure on that engine is about 36 psi, but I would be more comfortable if it was 45-50. I'm not a great believer in high oil pressures, such as 75-80 psi because I think it just pulls oil from the pan and strands it in the cylinder heads.

 

[Merkava_4]

Originally Posted By: uhcoog1
What filters have the highest flow and lowest pressure differential these days?


That would be NAPA Platinum/WIX XP.

 

[zray]

Originally Posted By: A_Harman
"…….. I'm not a great believer in high oil pressures, such as 75-80 psi because I think it just pulls oil from the pan and strands it in the cylinder heads.


high oil pressure has nothing to do with "stranded oil", neither does high volume. The only way oil gets "stranded" is if the drain back holes are plugged up. It just doesn't happen in a clean engine. The drain back holes can handle considerably more volume than the oil pump sends to the heads. Lets give the engineers just a little credit for building a reserve capacity into the system.

I wish I had a nickel for every oil myth I read on the internet.

Z.

 

[SteveSRT8]

^^^Since pressure and volume can be very different depending on design I doubt that the statement was a "myth".

Since A_Harman is/was deeply involved in development of actual engines perhaps you'd be so kind as to reveal YOUR qualifications...

 

[Lapham3]

Like lot's of things in life, 'one size fits all' doesn't really apply here. There are plenty of examples of engine development that initially 'missed the mark' in certain areas. I'll give an example. This some years ago at the shop of a Buick 400-430-455 engine specialty builder. A retired Buick engineer in Buick powertrain was giving a talk of Buick testing of the new 'light weight' 400-430 engines to replace the 'nailhead' V8. Quite a bit of 'real world' testing occured during drives from Flint, MI to the Desert Proving Grounds. Analog instrumentation monitoring was included. The engineer told of regularly breaking the 3" main crankshafts.(He mentioned full power runs up UTE Pass west of Colorado Springs)The 'fix' was to make the journals 3 1/4". He stated that they found that the new light weight block had some 'flex' under servere conditions that caused the problem. I'll always remember saying to him that the idea of stabilizing the flex with the rotating assembly seemed nuts. He kinda smiled and nodded. They still had some problems and later oiling 'fixes' and bearing clearance attention helped them survive better.I still prefer the nailhead. Sorry if long/off track a bit.

 

[zray]

Originally Posted By: SteveSRT8
^^^Since pressure and volume can be very different depending on design I doubt that the statement was a "myth".

Since A_Harman is/was deeply involved in development of actual engines perhaps you'd be so kind as to reveal YOUR qualifications...


I prefer to believe the engineers at Melling over the myth of HV or HP,pumps running the pan dry because all the oil is lounging inthe cylinder heads. Anyone at Melling will tell you that's just not going to happen.

PS. I helped my uncle build NASCAR engines when I was 12. That was 51 years ago. I've been building engines of every type since then. I think by now I know something about High rpm endurance V-8 engines, what they need to survive, and what to avoid..


Z

 

[turtlevette]

Originally Posted By: SteveSRT8
^^^Since pressure and volume can be very different depending on design I doubt that the statement was a "myth".

Since A_Harman is/was deeply involved in development of actual engines perhaps you'd be so kind as to reveal YOUR qualifications...


It's pretty much a myth. Take a look at almost any head. There are lots of big openings for drain back. It'd have to be a really poor design to pool a couple of quarts of oil.

We can respect someone's quals but still disagree based on engineering principles.

 

[punisher]

Nothing wrong with the bearing clearances. On the loose side, yes, but nothing that will cause a problem. (Old school "loose is fast" philosophy).

Anytime I see oil pressure drops/fluctuation at upper RPMs, I think of cavitation first and foremost. Sometimes people get the pickup /pan clearance wrong, sometimes you leave out a pan baffle/windage tray, sometimes you have drain back issues.

Add an extra quart of oil to the pan and see if upper RPM pressure changes.

The 10psi/1000RPM rule is kind of old, but something to remember- feeding an engine actual oil at 50 PSI is better than feeding it a foamy oil mess at 80 PSI.

 

[OVERKILL]

Originally Posted By: punisher
Nothing wrong with the bearing clearances. On the loose side, yes, but nothing that will cause a problem. (Old school "loose is fast" philosophy).

Anytime I see oil pressure drops/fluctuation at upper RPMs, I think of cavitation first and foremost. Sometimes people get the pickup /pan clearance wrong, sometimes you leave out a pan baffle/windage tray, sometimes you have drain back issues.

Add an extra quart of oil to the pan and see if upper RPM pressure changes.

The 10psi/1000RPM rule is kind of old, but something to remember- feeding an engine actual oil at 50 PSI is better than feeding it a foamy oil mess at 80 PSI.


Yup, this is what killed a motor we picked up that came with a car for my buddy (pics posted a long time back). Aftermarket pick-up/pan/pump/oil combo was cavitating. Ultimately the same supporting parts on a stock shortblock with a stock pump, pan and pick-up worked fine and reliably, pulling hard to the limiter, which was set at 7K in the Crane HI-6. This setup had no issues retaining oil pressure at around the relief on the pump (65psi) past about 4K IIRC.

 

[The_Eric]

Originally Posted By: punisher
Nothing wrong with the bearing clearances. On the loose side, yes, but nothing that will cause a problem. (Old school "loose is fast" philosophy).

Anytime I see oil pressure drops/fluctuation at upper RPMs, I think of cavitation first and foremost. Sometimes people get the pickup /pan clearance wrong, sometimes you leave out a pan baffle/windage tray, sometimes you have drain back issues.

Add an extra quart of oil to the pan and see if upper RPM pressure changes.

The 10psi/1000RPM rule is kind of old, but something to remember- feeding an engine actual oil at 50 PSI is better than feeding it a foamy oil mess at 80 PSI.


Along the same lines as adding oil, also remove a quart (if adding doesn't help or makes it worse). There was another member here who had a hot rodded Chevy that was doing the same or similar thing. After lots of hair pulling, help from forum members and emails to the oil pump company- he ended up draining a quart out, which fixed his problem.

 

[bruno]

Why don't you use the correct spec oil ?
30W is not 5W-40 .

 

[splinter]

Effects of windage and/or aeration?

http://dspace.mit.edu/bitstream/handle/1721.1/32358/61493939.pdf

 

[uhcoog1]

30 weight was recommended by the builder for break in.

A few fast 3G Hemi's on the drag strip have benefitted from adding oil drainback lines from the rear of the valve covers to the pan.

I tried a quart high and a quart low. Did not see a difference.

I'm putting 10w-40 conventional in this weekend. I'll finish break in on this, then try a 0w-40 European blend after that.

Are royal purple filters any good? I'll start looking for the recommended Fram and wix. Any opinions on their oil?

The factory Hemi pump has a ridge in the inlet. Should have removed the lip, that might have helped. Oh well.

 

[dailydriver]

Originally Posted By: uhcoog1
The motor is used for HPDE / road race / street driving. I shifted the last motor at 6,000-6,200 rpm, and this motor I'll pfobably shift at 6500 and maybe leave it in gear at 6500 or so when slowing for a high speed corner. The motor will see 7,000 on occasion.


This is in a Challenger, correct (or is it a swap into an older Mopar muscle/pony car?)?

Just curious, as I believe that the Chargers (with the exception of the new Hellcat version) cannot be had with a TR6060 manual gearbox, correct?
In any case it is COOL (and I am glad to see) that you are road racing/open tracking a Hemi car, as there are not a whole lot doing so as far as I've seen (besides our own Steve SRT8 on here).

Originally Posted By: uhcoog1
Dry sump is cost prohibitive for ANY motor.


Fixed it for ya!