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Oil pump gears - ever seen a failure?
- Thread starter SC3291
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Have seen at least 1 failure, and it was associated with an "oil starvation" situation (on high-g banked ovals) that ended up in catastrophic failure.
A bit of a chicken and egg on this -- did oil starvation cause the pump to fail (i.e., a pump running dry) or did the pump fail first and contribute to the oil starvation?
More likely the former, as the lateral Gs at an angle would push all the oil into the outer-side cylinders. But not being there, this is just speculation.
The folks "in the Woodwork" can give you more explanations on this -- not sure if they're on this Forum.
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In either case, am told the CT gears are recommended for forced-induction and prolonged track use. What the car really needs IMO is a higher-flow pump, and a pressurized oil system (dry sump?).
A bit of a chicken and egg on this -- did oil starvation cause the pump to fail (i.e., a pump running dry) or did the pump fail first and contribute to the oil starvation?
More likely the former, as the lateral Gs at an angle would push all the oil into the outer-side cylinders. But not being there, this is just speculation.
The folks "in the Woodwork" can give you more explanations on this -- not sure if they're on this Forum.
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In either case, am told the CT gears are recommended for forced-induction and prolonged track use. What the car really needs IMO is a higher-flow pump, and a pressurized oil system (dry sump?).
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- 3 February 2000
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Funny you should ask... I was just working on this new page for the FAQ:
http://www.nsxprime.com/FAQ/Performance/oil_pump_upgrades.htm
http://www.nsxprime.com/FAQ/Performance/oil_pump_upgrades.htm
Although I have not personally seen this happen, I WILL get the gear and the pump and install them with larger oil pan with buffle. The engine is too expensive to take any risks. But I will do this after I blow my current engine(huh?) I'm just looking for excuses to rebuild my motor with high performance parts 
. My goal is 380hp without force induction, stay tuned!
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George Wang
Keep it Real!
http://www.geocities.com/maomaonsx/price.html
. My goal is 380hp without force induction, stay tuned!------------------
George Wang
Keep it Real!
http://www.geocities.com/maomaonsx/price.html
Woodwork gave a good presentation at NSXPO 99 on the oil pump and the oil pump gear. It is my understanding that the problem of oil starvation as mentioned by Manuel above is not rectified by a stronger-than-stock oil pump gear such as Comptech's product. Oil starvation can be addressed on the NSX with a baffled larger oil pan, than forces oil to remain within reach of the oil pump's inlet.
The billet oil pump gear from Comptech is reportedly stronger than stock. Woodwork's presentation highlighted an instance where due to a mis-shift, the oil pump gear shattered from an application of too much torque.
I run the CT oil pump gear in my car, and have not experienced any problems.
-- Chris
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www.ScienceofSpeed.com - Click for more info
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The billet oil pump gear from Comptech is reportedly stronger than stock. Woodwork's presentation highlighted an instance where due to a mis-shift, the oil pump gear shattered from an application of too much torque.
I run the CT oil pump gear in my car, and have not experienced any problems.
-- Chris
------------------
www.ScienceofSpeed.com - Click for more info
www.NSXClassifieds.com - The internet's only exclusive NSX Classified site!
The last one that I replaced literally EXPLODED because my customer shifted into second at 120 mph and pegged the tach. He only went there for a fraction of a second, but the deed was done. The pump ring gear came out in ten perfectly sized pieces.
We DID install the CT Hi Capacity Billet pump. It fit perfectly and the quality was top notch.
Mark
We DID install the CT Hi Capacity Billet pump. It fit perfectly and the quality was top notch.
Mark
As with so many things from CT, the price seems excessive for what it is, limited production or not. Not that the protection isn't worth it, I'm just looking at how deeply they gouge you for it.
I had a 94 engine seize due to oil starvation (high rpm at extended high g left hand turn) I will not drive the NSX hard without the CT oil pump gear, I also recommend the hi-cap oil pan dali sells also I dont have it on my 97...yet.
Maybe woodwork can shed some light on this, but a Honda source told me the 3.2's were re-engineered to prevent this as Honda noticed this happening to a number of NSX's..I am not sure I am buying into this but its what I heard.
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Chris Anders
http://www.chrisanders.net
ce_anders on yahoo messanger
Authorized Zaino Dealer
Maybe woodwork can shed some light on this, but a Honda source told me the 3.2's were re-engineered to prevent this as Honda noticed this happening to a number of NSX's..I am not sure I am buying into this but its what I heard.
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Chris Anders
http://www.chrisanders.net
ce_anders on yahoo messanger
Authorized Zaino Dealer
Price getting a set custom made at a machine shop (if they can even do it right) and the cost is not so out of line.
Well yes, of course, but that's true of anything and everything and isn't the point. Or rather, it's exactly their point. I don't begrudge anyone a profit, but once their initial R&D is paid off I think they would come out ahead shooting for more volume. There are enough young people buying older cars and doing mods that the market has probably never been better, and still growing.
I wonder if Mark at Dali ever priced having the gears fabricated. It always comes down to volume.
Mostly I'm just annoyed with myself for not thinking to do this while I was replacing the timing belt and water pump.
[This message has been edited by sjs (edited 14 July 2001).]
Yes, it's an old thread, but I'm not one for creating yet another thread on the same topic.
Does anyone else have anything like updates to add to this?
Does anyone else have anything like updates to add to this?
Yep, the NA2's are stronger.
IMO, if you're not driving your car balls to the wall, you don't need these reliability upgrades. If you are, get as many as you can afford... The NSX wasn't engineered to be driven balls to the walls, every time..
Reading through this it just sounds like the gears are weak for over-revved engines. OK, I can think of other engine parts that can cause significant damage too in that scenario.
Does anyone know of gears that fractured and failed for a non-over-revved engine
Also, has anyone ever had one of the aftermarket oil pump gears cause problems
Thanks,
Dave
Does anyone know of gears that fractured and failed for a non-over-revved engine
Also, has anyone ever had one of the aftermarket oil pump gears cause problems
Thanks,
Dave
Reading through this it just sounds like the gears are weak for over-revved engines. OK, I can think of other engine parts that can cause significant damage too in that scenario.
Does anyone know of gears that fractured and failed for a non-over-revved engine
Also, has anyone ever had one of the aftermarket oil pump gears cause problems
Thanks,
Dave
According to the FAQs.....at extended high-RPM use (some techs as Honda has said mid-8000 RPM range) the stock oil pump gears spin so fast that they actually expand, which brings them out of tolerance and causes them to get stuck and shatter.
I track my car a fair bit, so I had this done this year in conjuncition with a new T-belt. It is an inexpensive mod compared to the price of a new motor.
Has anyone done something along the lines of re-working ("porting") the OEM oil pump?
there is a machine shop near me that did one that had a dali gear result was lower pressure, but roughly a 33% gain in volume(flow), then it was limited by oil journals, It was pretty neat to see, he has a machine called the "pig" that acts as the oil pump to determine flow in the block, heads, and oil squirters. It basically a fancy large capacity oil pump with a bunch of gauges.
Yes, Dali offers a wider gear (and therefore housing), that increases oil volumetric flow rate by ~17% with no drop in pressure:
http://www.daliracing.com/v666-5/catalog/index_browse_part.cfm?focus=2544
Oil pump gears fail due to cavitation. That happens when the pump is spinning so fast and trying to supply oil flow without enough oil being supplied at the inlet of the pump. The pump is creating a vacuum at the inlet since it is trying to suck more oil than is available. The net positive suction head available is not high enough, and the oil begins cavitating. This cavitation is what leads to oil pump failure. Google oil pump cavitation.
While the original explanation that the cheap metal just shatters given in the FAQ may also be valid, it is my $0.02 that cavitation is the main reason for the pump failure at extended RPM.
Now, to avoid cavitation, you need to ensure the Net Positive Suction Head (NPSH) Available (NPSHA) at the pump inlet is greater than the NPSH Required (NPSHR) for your particular pump at maximum engine RPM. NPSHR increases as pump speed increases. Now, our oil system has an internal bypass circuit in it. As engine speed increases, the increased pressure builds up to a point where it's force overpowers a spring and dumps the pumped oil back to the pump inlet. This is very important because as pump speed increases, your NPSHR is increasing while your NPSHA is constant due to the oil level in the pan (that's sloshing around and also slowly decreasing as the heads are filling up with oil from sustained VTEC). This is a recipe for disaster unless the pump suction can be supplied with some of this bypassed oil.
I know one of the popular Honda mods B16/B20's, etc) is to add a shim to the oil bypass spring to increase the maximum oil pump discharge pressure before it bypasses back to the inlet. I don't think that is a good idea since you are decreasing the bypass flow until higher engine speed is reached. That means more pump cavitation. Unless you've modified the engine oil passageways and added piston squirters or have significantly enlarged bearing clearances, the Honda engineers sized the flow capacity and pressure correctly for our engines.
I'm rebuilding my engine right now. I purchased the Dali billet oil pump gear to replace my old OEM one. I'm not porting anything or increasing the maximum discharge pressure since I don't think that's the right thing to do. I'm just going to check all clearances of the pump, gear, and spring to make sure they are in spec.
A dry sump will solve this, but what cost? Unless you REALLY know what you're doing, you can ruin an engine trying to figure out your dry sump setup too.
My $0.02.
Dave
http://www.daliracing.com/v666-5/catalog/index_browse_part.cfm?focus=2544
Oil pump gears fail due to cavitation. That happens when the pump is spinning so fast and trying to supply oil flow without enough oil being supplied at the inlet of the pump. The pump is creating a vacuum at the inlet since it is trying to suck more oil than is available. The net positive suction head available is not high enough, and the oil begins cavitating. This cavitation is what leads to oil pump failure. Google oil pump cavitation.
While the original explanation that the cheap metal just shatters given in the FAQ may also be valid, it is my $0.02 that cavitation is the main reason for the pump failure at extended RPM.
Now, to avoid cavitation, you need to ensure the Net Positive Suction Head (NPSH) Available (NPSHA) at the pump inlet is greater than the NPSH Required (NPSHR) for your particular pump at maximum engine RPM. NPSHR increases as pump speed increases. Now, our oil system has an internal bypass circuit in it. As engine speed increases, the increased pressure builds up to a point where it's force overpowers a spring and dumps the pumped oil back to the pump inlet. This is very important because as pump speed increases, your NPSHR is increasing while your NPSHA is constant due to the oil level in the pan (that's sloshing around and also slowly decreasing as the heads are filling up with oil from sustained VTEC). This is a recipe for disaster unless the pump suction can be supplied with some of this bypassed oil.
I know one of the popular Honda mods B16/B20's, etc) is to add a shim to the oil bypass spring to increase the maximum oil pump discharge pressure before it bypasses back to the inlet. I don't think that is a good idea since you are decreasing the bypass flow until higher engine speed is reached. That means more pump cavitation. Unless you've modified the engine oil passageways and added piston squirters or have significantly enlarged bearing clearances, the Honda engineers sized the flow capacity and pressure correctly for our engines.
I'm rebuilding my engine right now. I purchased the Dali billet oil pump gear to replace my old OEM one. I'm not porting anything or increasing the maximum discharge pressure since I don't think that's the right thing to do. I'm just going to check all clearances of the pump, gear, and spring to make sure they are in spec.
A dry sump will solve this, but what cost? Unless you REALLY know what you're doing, you can ruin an engine trying to figure out your dry sump setup too.
My $0.02.
Dave
So the NA2 Oil pumps have different Gears? Bigger? Any other changes to the Oil system on a NA2?
That's the first I've heard of different oil pumps/gears being used.
I think everything is identical, even the same engine bearings.
I couldn't find the actual oil pump gear part numbers, but the oil pump assemblies have the exact same part number between C30 and C32: 15100-PR7-J21. If the housings are identical, the physical size of the pump gears must be too.
Dave
I think everything is identical, even the same engine bearings.
I couldn't find the actual oil pump gear part numbers, but the oil pump assemblies have the exact same part number between C30 and C32: 15100-PR7-J21. If the housings are identical, the physical size of the pump gears must be too.
Dave
That's true, but I wouldn't use their modified relief spring to increase the oil pressure for the reason given above.
Unless you've significantly modified the engine and have a better oil pump suction design, increasing oil pump flow or pressure or both is probably not a good idea.
Some people on here have observed their oil pressure gauges indicate near zero pressure at high RPM when in sustained VTEC on the track. If the sender and gauges are working correctly, then this in indicative of oil pump cavitation since the pump flow output and pressure will drop and be erratic.
That's why I think an Accusump is a great and cheap solution. Even though I probably won't be tracking my car in the near future, I am putting a 3qt Accusump system on my rebuilt engine. What can I say, brief bursts to 8500 RPMs is fun....
Dave
Not to nitpick, and I don't know if it was mains or rods, but the 3.2 bearing journals are larger by i think 2 mm.
No insult intended, but our lay discussion is somewhat academic. We need to know what all oil system mods Shad and other race engine builders have used. And copy them. These parts are WAY to expensive for trial and error mods. Pretty disappointing that Honda did not address this on later models. ANY oil system failures should have been treated VERY seriously. While we are not getting responses from those with the problem, not many old timers are on this list i don't believe. From my memory of the old big list and not hanging out at the track, I do recall several bone stock cars popping on the track. Ironically chevrolet does smallblock upgrades just about every year. While their cars may not make it around the block, they would have fixed this pronto.
I completely agree. It's just that I have neither the personal funds nor the willingness to rebuild failed engines. Short of the profesisonals telling us what mods they did and for how long it worked for them, we each have to make our own decisions on what we feel comfortable with.
I was just bringing up something that is commonly regarded in the industry as the main cause for oil pump failure (cavitation), but has never been mentioned before on this site (we just blame it on inferior gears).
Dave
