Anthony 1,003 Posted June 2, 2006 After it sitting there crying out for attention for the best part of two years, I've finally pulled my finger out and put my new rebuilt 1.9 Mi16 lump togther. Yes, wonders will never cease... Anyway, the quick question is whether it is worth using the Group A oil pump spring that I've got sat here in the engine, or will it gain precisely nothing? The engine is fairly standardish spec, still retaining the hydraulic lifters and will be running a new pattern XU9 oil pump from QEP. Logically I can't see that it's going to help things a great deal, and certainly oil surge will likely be just as bad as if there's no oil for the pump to pickup then it's not going to matter one iota what pressure spring you're running. On the other hand though, I can't help but think that Peugeot Sport wouldn't have made a higher pressure spring if it had no benefit, and more to the point, there must be a reason why the XU10 engines all run higher pressure as standard than the XU9 engines. Anyone got a definative answer of the benefits and drawbacks of running higher oil pressure? (I'm sure this has been discussed countless times before but I couldn't find a definative answer when searching, so apologies for the fact this is almost certainly a repost ) Share this post Link to post Share on other sites
Miles 331 1 Cars Posted June 3, 2006 I always use the spring to help up the pressure slightly on the XU9's, But I would always run a XU10J4RS pump (Runs a different speed) now as it gives better pressure has a chain guard on iut to help stop to churn up the oil in the sump and the main thing it runs a keyed drive wheel unlike the crapping friction fit ones, You just need the RS cambelt drive pulley again lighter but you need adjustable pulley's as the drive wheel is 1/2 tooth out on the timing Share this post Link to post Share on other sites
Rippthrough 98 Posted June 3, 2006 http://forum.405mi16.com/index.php?showtopic=152 No experience myself, but theres one reason there that makes sense. Share this post Link to post Share on other sites
Baz 421 Posted June 3, 2006 Also something i had wondered but couldn't find much after a search! Surely its helpful if not 'essential'?? Share this post Link to post Share on other sites
petert 588 Posted June 3, 2006 (edited) I'd just change to an XU10J4 drive sprocket (26T) and chain. More volume, same pressure. I've got no evidence to support whether the extra oil pressure will increase the onset of lifter pump up, but theory suggests it would if your valve spring seat pressures weren't up to scratch. I know the XU10 engines run at 8 Bar, but 6.5 Bar is still a lot of oil pressure. Conversely, you have to consider how much pressure drop there is between the pump/main gallery and a lifter. There would be a significant pressure drop over the non-return valves, how much I have no idea. Perhaps PSA was allowing for this, ensuring there was still a reasonable pressure at the lifter gallery? Edited June 3, 2006 by petert Share this post Link to post Share on other sites
Anthony 1,003 Posted June 5, 2006 Thanks for the responses I'd just change to an XU10J4 drive sprocket (26T) and chain. More volume, same pressure. Maybe I'm overlooking something, but wouldn't using a drive sprocket with more teeth just mean that you're turning the oil pump over faster at a given engine speed? If so, wouldn't that just mean that you get upto maximum oil pressure earlier in the rev range and then you're still on the pressure bypass valve, and thus merely increasing pumping lossses by spinning the oil pump faster than required? I've got no evidence to support whether the extra oil pressure will increase the onset of lifter pump up, but theory suggests it would if your valve spring seat pressures weren't up to scratch Is this mainly an issue if you're running higher than standard revs and/or with lairy high lift cams on standard springs? The engine has new OE valve springs on it and shouldn't be running cams too lairy or running at excessively high rpms (although the bottom end was built with that potential in mind being fully balanced and with ARP bolts, with the limitations of the standard rods/pistons anyway) Share this post Link to post Share on other sites
Rob_the_Sparky 9 Posted June 5, 2006 How about looking at it from a different point of view: What is the downside of running more oil pressure? I suspect it is being more leak prone but there must be others as well... Rob Share this post Link to post Share on other sites
Miles 331 1 Cars Posted June 5, 2006 I'll have to check the teeth on the Oil Pump it self as these can vary too, But getting a restrictor in the head to head keep the oil in the sump is a good idea, Another thing found on the GTi6 engine Share this post Link to post Share on other sites
jacobs53 0 Posted June 5, 2006 How about looking at it from a different point of view: What is the downside of running more oil pressure? I suspect it is being more leak prone but there must be others as well... Rob From what i have read too much oil pressure can lead to serious problems!!! From my understanding lets that the main bearings, the oil is forced into the journal and provides a wedging action (sorry can't remember the name for this, hydro... something) and centralizes the jounal inside the bearings. If the oil pressure is too excessive the oil can actually push the journal down onto the bottom bearing and cause increased bearing wear, and likely failure. You will also probabily find that the oil galleries in the xu9 and xu10 differ in length and diameter, and this is for a reason! the sizes determine the velocity of the oil at a certian pressure, if the oil galleries are increased then the oil velocity reduces and it takes longer for oil to reach a certain point. Also from the research into the gti-6 head it probabily uses a slightly lower oil pressure and smaller size of oil gallery, to prevent the oil starvation. don't know how relevent this is to your question, anthony, but I'd seriously research into what are the effects of increasing the oil pressure too much. When i was rebuilding my turbo engine, I tried to use a oil pump from a 1.9 diesel (one with the vernier pulleys as standard) but when opening up the pump the rotors when smaller, and the oil capacity was smaller inside the pump. After questioning one of my lecturers he said the best oil pump to use is the smaller one with a uprated pressure spring (for performance reasons anyway, less rotating mass etc...) but he swore blind about keeping the oil pressure as the manufacture intended unless i changed the oil galleries or made a modification to the oil system. lee Share this post Link to post Share on other sites
petert 588 Posted June 6, 2006 (edited) More pressure also costs more hp. Like everything, You don't get something for nothing. I'd recken it takes 23% more hp to drive the same pump at 8 Bar rather than 6.5 Bar. Edited June 6, 2006 by petert Share this post Link to post Share on other sites
