You observed a sustained drop over time? What's the lowest pressure you read at the sender? I would expect the flow rate required to sustain vtec after the initial engagement would be small. The pump must be able to maintain flow through all bearings and orifices while keeping adequate/safe pressures.
Technical Discussion about Oil Pressure
- Thread starter Larry Bastanza
- Start date
The longer the car is in VTEC to lower the pressure is. Inital VTEC engagement will drop pressure from 90 PSI to 80 PSI, the pressure will slowly drop(about 35 sec.) to 30 PSI read at the gauge, down stream from the spool valve. This was on a motor with 4000 miles, all bearings within spec, Comptech oil pump and gears. This was at Spokane Raceway where you can run wide open from the last turn, front straight and through turn 1 with out lifting, about 155 MPH at the brake zone for turn 2.
As soon as RPM dropped, spool valve closed and the gauge would pop back up to about 70 PSI.
As soon as RPM dropped, spool valve closed and the gauge would pop back up to about 70 PSI.
I'm new to this thread after recently experiencing the (indicated)oil pressure on the stock gauge in my 95 drop to 0 above 7500 rpm , i drove the car around alot trying to make sense of it and rationalized a few already mentioned points,1 - yes the vtec would kick off if the pressure really dropped- 2 the motor wouldn't live very long at 8k with no oil but is there anyone who has actually had this problem with oil press. dropping above 7k and can verify that it is the sender? obviously my next move is to verify press. with a real mechanical gauge! but for how hard i run my car i'm thinking that if i really had a problem with oil supply my motor would be done by now! (I even held the thing in 2nd gear at 7500 rpm for quite a while, studying the guage's action - yes i'm brave ,and also looking for an excuse to build a real turbo motor!) any real input on this phenomenon is greatly appreciated
Wil
Wil
We have an NA 2 car that is exhibiting the oil pressure drop off above 7300 RPM, just drops down to 0 if you keep the car above that RPM. I dropped a manual oil pressure gauge (with T fitting at the location where the stock pick up is) off at the garage where the car is in for a timing belt change. Eddie is going to hook it up and see if there is a pressure drop or something odd with the sender...
Stay tuned...
Stay tuned...
Eddie mentioned that to me this past BMW day. I assured him it was normal but I believe he thought Paul's car was some type of exception when he had it out on session.
My own experience is that I pegged mine to zero every lap last year into T1 without fail. It starts concern-ably dropping off fast half way down the front straight at the top of 4th and by the time I glanced back down - having just shifted into 5th back on WOT - it read dead zero, and remained so until the braking zone. Knowing it was a documented issue and other aftermarket gauges read fine, I just got used to it and didn't let it bug me out- also chalking it up to the long sustained VTEC coupled with the sender taking the abuse over time.
What's to say- stock gauges and senders are usually never all that confidence inspiring on the track. IMHO you can get by with them but for most applications they obviously aren't the ideal. It is really nice to have an audible alarm for critical things like oil/water anyway because you can't rely on driver. Either way, I look forward to seeing the test results. His car being bone stock should work very well for this purpose.
Personally, I see it as a great opportunity to spend more money... and you can always just take the high road as I'm confident it is nothing 5-10K in PI or EFI data instrumentation won't fix. :wink:
However, since we are talking about Paul's NA2... I think the solution is that he needs to park it and let us strip that awesome Mercedes of his I saw the other day and it's problem solved. I think it's time for a Euro time-attack. :biggrin: :biggrin:
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this is all very weird...
about this next to 0 pressure above 7300rpms...
when i do my near 300km/h runs...the rpms are next to 8000 for about 5 minutes long... i look often to the pressure needle...the lowest i've seen it was little lower than half, 1 tick down at the most....
about this next to 0 pressure above 7300rpms...
when i do my near 300km/h runs...the rpms are next to 8000 for about 5 minutes long... i look often to the pressure needle...the lowest i've seen it was little lower than half, 1 tick down at the most....
Al, you had me at "showing over 45 lbs during full VTEC."
But, you lost me at "a little over the 6 mark" on the freeway.
My car (high mileage, high track use, stock) idles at the 1 mark (or so) but at cruise is only at the 4 or 5 mark. It only goes over 5 when the oil is cold. Even when I rev it it doesn't get up to 6 unless really cold and high revs.
When VTEC kicks in, my gauge shows maybe 4.5 and then starts to drop. It drops to 4 or less. It had (has) me concerned.
I just wonder if our cars are exhibiting the same thing - or if mine is reading lower than yours throughout the use cases.
For those that have replaced their oil pressure sender, what were the results and how much was the sender?
I replaced mine and had much better readings.
http://daliracing.com/v666-5/catalog/index_browse_part.cfm?focus=1814
http://daliracing.com/v666-5/catalog/index_browse_part.cfm?focus=1814
Swapped out the sender and the oil pressure never drops to 0. It will still drop below 4 bars on the dash gauge at the end of a long VTEC run.
When I talk about the readings I'm getting from my OEM sending unit, it may not be the same for yours. From what I've seen from other NSX's out there, the normal freeway driving oil pressure from the stock sending unit can vary by one or two marks. I don't put much faith in the true accuracy of the OEM unit since it had to be designed with a good dampening quality to compensate for the high vibrations present on the head. It's close but they really only wanted to show you that you did have oil pressure in most driving speeds. I know that before I changed oil to Mobil 1, at idle I showed no oil pressure. Now it registers at the first mark. But this is why I opted to install the second oil pressure gauge because I feel it's a very important reading for all engines and especially those used in a track event.
I wouldn't worry about what specific reading you are getting versus someone else. It is due to the variance in the manufacuturing at the factory more than anything else. I would start to worry if the oil pressure dropped quickly during VTEC and you suddenly also felt the engine kick out of VTEC as well. That could be a sign that you have lost major oil pressure and you might want to shut down ASAP. Also the second gauge gives me more confidence if one of them suddenly reads "0" and the other is reading other than that. So far my setup has been working fine for over 3 years and all track events. I'm definitely glad I added the second oil pressure and an oil temperature gauage.
Now it's time for an oil cooler.
Al
I wouldn't worry about what specific reading you are getting versus someone else. It is due to the variance in the manufacuturing at the factory more than anything else. I would start to worry if the oil pressure dropped quickly during VTEC and you suddenly also felt the engine kick out of VTEC as well. That could be a sign that you have lost major oil pressure and you might want to shut down ASAP. Also the second gauge gives me more confidence if one of them suddenly reads "0" and the other is reading other than that. So far my setup has been working fine for over 3 years and all track events. I'm definitely glad I added the second oil pressure and an oil temperature gauage.
Now it's time for an oil cooler.
Al
Has anyone ever felt their NSX drop out of VTEC because the oil pressure was too low?
Maybe VTEC stays engaged even if the oil pressure drops because of friction in the engagement mechanism. If that were the case, the oil pressure could drop dangerously low but we wouldn't feel it. Since all the mechanical VTEC parts are covered in oil, that shouldn't happen, but who knows?
I've never felt my car drop out of VTEC, but when my stock (and surely inaccurate) oil pressure needle drops below two or three bars, I back off the gas just in case. It it were safe to keep it floored, I'd love to!
Maybe VTEC stays engaged even if the oil pressure drops because of friction in the engagement mechanism. If that were the case, the oil pressure could drop dangerously low but we wouldn't feel it. Since all the mechanical VTEC parts are covered in oil, that shouldn't happen, but who knows?
I've never felt my car drop out of VTEC, but when my stock (and surely inaccurate) oil pressure needle drops below two or three bars, I back off the gas just in case. It it were safe to keep it floored, I'd love to!
yes, i've seen many vtec cars come out of vtec with insufficient oil press. It will happen because the vtec press switch disengages. the situation you describe cannot happen because without oil press the pins will be forced back immediateley,as soon as the cam rotates enough that it is on the base circle of the lobe
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- 16 November 2018
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I know I'm coming very late to this thread, but I have some info that may help others if they run into this problem. When I bought my 1997 NSX (in 2011), it did not exhibit this problem. Normal pressure was around 70. At some point, it started losing oil pressure above 7K. By the time I hit 8K, it would be down around 20. I did not keep it there to see if it went lower (as some have apparently done). My mechanic at the time said it was either a dented oil pan, which put the pan too close to where the oil gets sucked up to allow enough in, or the sending unit. We found that the oil pan was dented (apparently someone had tried to jack up the car using it as the jack point). So, we changed the oil pan. That didn't fix the problem. Unfortunately, the sending units are no longer available, even from Japan. Different mechanic at this point (long story) who found this thread as he was trying to research the problem. He's the one that found the sending unit no longer available. While it was there, they were supposed to change the oil (told them to use Mobil One). When they changed the oil, either the mechanic didn't see the note or ignored it and used Red Line. The problem is now gone, or at least mostly so. It still drops, but only to about 50-60. I do remember at some point switching from Red Line to Mobil One. I'm guessing that's when the problem started, but I didn't correlate at the time because I don't usually wind it out that high on the street and it was probably many weeks between oil change and next track event. Anyway, figured I'd post what I'd learned in case someone comes along with the same issue and this info helps.
