OIL MOD - The Reader's Digest version
by Dave Dodge

Phil Ross wrote:
>I am trying to understand this. Using oil pressure to the top end (supplied by the stock transmission line) as a baseline, how >can oil pressure to the bottom end increase when your oil mod is tapping its supply, given that both pressure and volume to >the top end have also been increased? How does this affect *volume* to the bottom end? I do understand that the old >transmmission-to-topend line has been plugged and that should increase both pressure and volume available to the main >gallery, but it seems to me that the total volume supplied by the oil pump wouldn't change. Is pressure more important than >volume to the bottom end?

Dave :
I'm glad you asked, so here is the Reader's Digest version. The oil pump has two stages; 1) the higher pressure side that feeds the main galley, and 2) the low pressure side that feeds the trans and stock top-end oil take-off.


Once the pump builds pressure at idle the oil is guided thru a series of orifices to meter flow to the two passages. The low pressure side of the pump is so low on pressure that Honda uses a .080" restrictor inside the angle drive to build pressure, and a second .100" restrictor in the end of the bolt to maintain that pressure before it enters the stock metal line. After the restriction the oil dumps into much bigger lines in an attempt to create volume which does not work very well because its source is an .080" hole, hence the oil feed problem.


By blocking the stock passage to the heads when using an oil mod, the oil that is normally diverted to the heads is instead fed to the main galley resulting in increased volume and pressure. This now becomes the source for the required oil used by the oil mod. The only control that limits the main galley flow is a pressure relief valve that opens at about 80 psi to prevent over-pressurizing the system. At idle up to around 6000 RPM you get the full benefit of any oil that finds its way into the main galley.


Now for an explanation of how lower-end pressure can be increased when the oil mod is installed. First and foremost through years of testing we (DRP) know how much oil and what pressure is required to keep cams properly lubed. We control this by line size that is specifically designed to achieve this. The problem with most do-it-yourself mods is that the line size is too big. This results in a drop in lower-end oil pressure. The DRP mods provide 3 times the volume of oil at twice the pressure vs. stock, using filtered oil and has the added benefit of a 2 to 5 psi increase in bottom-end oil pressure. Anything more than this is not needed and results in a 2 to 5 psi decrease in bottom-end oil pressure. In this case bigger is not better.


To put all this in prospective, this all started when Anne was asking questions about the best way to do an oil mod on a V45 Interceptor. This particular engine is very finicky about oil supply to both top-end and bottom-end. I warned against using the home-made and Art R's mod plans because the line sizes are way too big. The V45 Interceptor also requires the low-profile style adapter to clear the exhaust pipes. In other words, what was intended and selected by Anne was not going to fit or provide the proper pressure characteristics for that bike.


Additionally, for the last week I have been corresponding with a guy who just rebuilt a V45 Interceptor and did a large hard-line mod. He was asking why he was only getting 20 psi pressure at 5000 RPM and it should be 50+. He installed a new pump, new seals etc. and was stumped. I asked him about his mod and he told me that he used 5/16" hard line to the heads. Well we already know that this is too big, so he has purchased one of mine, and results to follow.


Dave Dodge DRP
drp123@mindspring.com <mailto:drp123@mindspring.com>
AMA, SCRA, ProStar, NHRA
Interceptor Drag Bike (Parting Out)
Killer Vee III ('96 Magna Dragbike)


Ozzie
Re: Oil Mod
Fri Nov 17 22:21:27 2000


When using the screw on mod, you change to using the MM9 filter versus the stock MJ0. The MM9 has the same filter capacity as the MJO and same relief pressure, it's just packaged in a smaller body.