Modified oil pump really needed?
12 March 2007, 06:59 PM
#1
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Modified oil pump really needed?
I asked this before but didnt get a proper answer. Planning to run 380bhp. I know people say its more safer etc. But how about comments from guys actually running high power. Did you change your oil pump? If not hows it coping?
13 March 2007, 01:21 AM
#3
If you are running methanol, remember that your AFRs need to be adjusted for your methanol mix with petrol. Failure to do so means you run a weak mixture and cancause serious damage.
Stoich for petrol is 14.7 : 1. Stoich for methanol is around 6.4 : 1.
Decide a percentage methanol, work out the stoich figure and then stick to it but it means you are locked in to using methanol always if you want the best out of your engine, unless of course your ECU supports two maps, one for methanol and max performance and one for V-Power or whatever.
Stoich for petrol is 14.7 : 1. Stoich for methanol is around 6.4 : 1.
Decide a percentage methanol, work out the stoich figure and then stick to it but it means you are locked in to using methanol always if you want the best out of your engine, unless of course your ECU supports two maps, one for methanol and max performance and one for V-Power or whatever.
13 March 2007, 08:06 AM
#5
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This is a good question. I'm not sure what they do when modding them but i cant see any problems with a factory pump. Oil pressures never been a problem with mine at any rpm above 2k. When i put my engine together i just tapped each side of the screws into the pump housing so they cant come undone.
13 March 2007, 08:50 AM
#6
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The mod to the pumps is only a small one to the relief plunger.
Some engine failures have been attributed to the plunger sticking, and/or the retaining bolts on the back of the housing coming undone.
For this reason if you are doing a rebuild or have the cam belt off then it's worth doing for peace of mind IMHO. Or at least check the bolts and loctite them in.
It will make no difference to the pressure (unless of course your old pump is worn), but pressure is not regarded as a reason for failure (unless of course you are loosing pressure from the cover bolts being loose).
Some engine failures have been attributed to the plunger sticking, and/or the retaining bolts on the back of the housing coming undone.
For this reason if you are doing a rebuild or have the cam belt off then it's worth doing for peace of mind IMHO. Or at least check the bolts and loctite them in.
It will make no difference to the pressure (unless of course your old pump is worn), but pressure is not regarded as a reason for failure (unless of course you are loosing pressure from the cover bolts being loose).
11 April 2008, 08:37 PM
#7
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So what exactly is the mod? Something that a bit of sandpaper could cure, assuming the rest of the standard oil pump is OK? Are all the modified oil pumps punted around the same mod? Or do some produce higher oil pressure with a different spring or something?
I'm all for an extra margin of safety but at the same time, why do modded oil pumps seem so expensive when a cheaper option would be to reuse my existing one and do the 'mod' myself. If I've got as far as pulling the engine and dismantling it, how hard can it be to fix the oil pump?
I'm all for an extra margin of safety but at the same time, why do modded oil pumps seem so expensive when a cheaper option would be to reuse my existing one and do the 'mod' myself. If I've got as far as pulling the engine and dismantling it, how hard can it be to fix the oil pump?
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13 April 2008, 08:49 AM
#10
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Well I would be very interested in that...I'm all for paying experts to do a job - if I can't do it myself. But I'm on a strict budget with this engine rebuild so if I can do just as good a refurb/mod job myself, why not? And let's be honest, the jury still seems to be out as to whether oil pumps cause big end failures, or big end failures cause oil pump failures. Unless there's a big name Subaru specialist out there who's ready to guarantee and stake their reputation on oil pumps being the cause of big end failures....
13 April 2008, 08:59 PM
#14
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Yes I can understand the relief valve being basically shimmed (a stainless steel washer?) to change the pre-load so you hit a higher pressure before the relief valve will open, but what is the actual 'modification' that's done to the valve itself? Or is it just to the tube it runs in?
It's interesting that a few reputable Subaru specialists sell basically the same modified product, often using the EXACT same wording claiming that they have found various problems with the OE design and modified it. The only ones which seem to be different are Cosworth who talk about actually cleaning up the oil passages inside as well as actually changing the pump gears from 10mm to 12mm to give 20% more flow.
It's interesting that a few reputable Subaru specialists sell basically the same modified product, often using the EXACT same wording claiming that they have found various problems with the OE design and modified it. The only ones which seem to be different are Cosworth who talk about actually cleaning up the oil passages inside as well as actually changing the pump gears from 10mm to 12mm to give 20% more flow.
14 April 2008, 07:13 PM
#15
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Or let's put this another way - if I'm tackling an engine rebuild, is rebuilding and 'modding' an oil pump myself gonna save me £150. Or can oil pump's be permanently knackered by a big end failure and un-saveable?
14 April 2008, 07:32 PM
#16
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You need to check the condition & clearance of the rotors & relief valve. If all is ok then it's ok 
Put the money towards a new modine (and flush the block & heads with the gallery plugs removed!)
Jase.
Put the money towards a new modine (and flush the block & heads with the gallery plugs removed!)
Jase.
14 April 2008, 08:14 PM
#17
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That's my thoughts exactly. It's not that I'm cheap (well I am a little) but that money could be spent elsewhere where it's more important, and by all counts the modine CAN'T be reused?
14 April 2008, 08:17 PM
#18
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15 April 2008, 06:07 PM
#20
If you look at the std relief valve it has small "clearing" ring machined around it's circumference, The theory is that debris can get stuck in this ring and cause it to stick open, which in turn will obviously cause low oil pressure.
The mod is a relief valve which does not have the ring machined into it.
A few years ago there were various theories as to why these engines were suffering from big end failures, one of them was the oil pump relief valve. As when the pumps on blown engines were being stripped it was noted that the relief valve had stuck open & debris had caused this. Unfortunately it's a bit like the "chicken & egg" theory. Which came first? Did some debris get into the pump and cause the engine failure? or did the engine fail first, which in turn then caused swarf to pumped around the system and into the pump itself consequently jamming up the relief valve.
It's up to you to decide which.
Phil
The mod is a relief valve which does not have the ring machined into it.
A few years ago there were various theories as to why these engines were suffering from big end failures, one of them was the oil pump relief valve. As when the pumps on blown engines were being stripped it was noted that the relief valve had stuck open & debris had caused this. Unfortunately it's a bit like the "chicken & egg" theory. Which came first? Did some debris get into the pump and cause the engine failure? or did the engine fail first, which in turn then caused swarf to pumped around the system and into the pump itself consequently jamming up the relief valve.
It's up to you to decide which.
Phil
16 April 2008, 05:45 PM
#21
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Well I'm just about to pull my oil pump out tonight so I'll have a look. I know when it failed I heard the rattling way before I started losing oil pressure and oil temp started rising.
Are these 'plain' relief valves without the ring available to buy off the shelf? Or do I need to get one machined for me?
Are these 'plain' relief valves without the ring available to buy off the shelf? Or do I need to get one machined for me?
16 April 2008, 06:08 PM
#22
No it's not an off the shelf item I’m afraid. Roger Clark have them made and then fit them themselves.
My personal opinion is that there is not a problem with the std item.
Prodrive do not do this mod when building the top spec Grp N engines & they do not suffer from the supposed fault.
On a footnote about playing with oil pressures, the std pump produces more than an adequate amount of this & imho there is no need to increase this. Infact, the early Prodrive Grp N engines had this reduced to gain a bit more power from the engine & this may well still be the case.
Phil
My personal opinion is that there is not a problem with the std item.
Prodrive do not do this mod when building the top spec Grp N engines & they do not suffer from the supposed fault.
On a footnote about playing with oil pressures, the std pump produces more than an adequate amount of this & imho there is no need to increase this. Infact, the early Prodrive Grp N engines had this reduced to gain a bit more power from the engine & this may well still be the case.
Phil
16 April 2008, 06:14 PM
#23
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So presumably all the other modified ones out there - e.g. Graham Goode Racing - are doing the same thing (the replaced valve), or are they just sticking a washer in to preload the spring to relieve pressure slightly higher than usual?
16 April 2008, 08:29 PM
#27
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So Harvey - do you have any of these plungers? If so, I've bought bits and bobs off you before and I'll happily do so again, just PM me.
I'll take my oil pump out tonight if I can and check it against spec, if everything looks OK, then I'll just mod it myself.
I'll take my oil pump out tonight if I can and check it against spec, if everything looks OK, then I'll just mod it myself.
17 April 2008, 12:38 AM
#29
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No problem Harvey, at least I can see what I'm dealing with. I've just taken mine apart and when the spring came out, the plunger didn't come with it. The thing was wet with oil so it should have just plopped out but it had to be fished out instead with the end of the spring. It felt gritty as it came out and there was a coating of very fine swarf on it. Presumably this is what stuck it open and caused my loss in pressure, after the big end failure.
18 April 2008, 12:42 AM
#30
Yes but like Phil from Barretts Motorsport said, what came first? The engine failed and debris is now spread through the engine including the oil plunger chamber thus jamming the plunger open. OR The plunger jammed open with a resulting loss of pressure causing metal to metal contact and bearing failure???
A bit like the chicken and the egg. Which came first?
A bit like the chicken and the egg. Which came first?