Flow

Hi folks, for sub 300hp tracked cars what intervals should we be replacing our oil pumps? Are there any trend monitoring indicators for first sign of degraded performance? What do people do for component time in service tracking?

sixshooter

iTrader: (12)

As far as I know, most of us just use a boundary engineering Billet oil pump and sometimes a better aftermarket harmonic balancer like an ATI or fluidampr. Unless there is foreign object damage I don't know of anyone who has replaced the boundary oil pump simply because of run hours.

Mudflap

I have a related follow up question. Does anyone have an pump that allows oil to drain (slowly) back down from the head? I ask because when my car has set for a few days I get a horrible sound on the top end that goes away within seconds. I presume that I've got oil draining down out of the top end.

Flow

Thank you six, can you explain the connection between oil pumps and engine harmonics or does the boundary engineering pump also eliminate harmonic balancer clearance constraints? I am looking to better understand the failure/degradation mode or design limitations of the OEM oil pumps especially if harmonics are involved.

I have seen some say that the OEMs oil pumps are fine at 300hp but is it fair to say that the oil pumps on these engines are a week point or is it more about trying to dampen harmonics?

codrus

Disclaimer: I'm a software nerd, not an ME.

AIUI, there are a lot of rotational vibrations in a 4-cylinder's crankshaft, which the harmonic damper is supposed to cancel out. A stock damper, in new condition, does a pretty good job of this at stock power levels. As the power level goes up and as the damper wears, it does this less well. When you get past some combination of power and lack of damping, the first thing that fails is the sintered gear in the OEM oil pump. As an extreme example, there are multiple instances of a stock oil pump failing when paired with a turbo and a damper delete (solid underdrive pulley), sometimes in as little as 20 miles.

Empirically, 300 rwhp with a stock oil pump and a good condition stock damper seems to be OK. Most people who are dumping thousands of dollars into built engines decide to spend the few hundred dollars on either a boundary pump or an upgraded damper (or both!) for insurance.

--Ian

sixshooter

iTrader: (12)

Stock oil pumps fracture sometimes. It is expensive and usually happens at an inopportune time. Harmonics are thought to be a contributing factor. Piston engines do not spin at a steady speed. Every revolution they are speeding up and slowing down and the speeding and slowing becomes more pronounced with increased cylinder pressures. The damper and the flywheel are designed to even out these pulses but they do not solve the problem. Lightweight balancers and flywheels exacerbate the problem.

Feel free to do whatever you like with your engine. As for me, I like to remove unnecessary exposure to financial trauma.

Savington

iTrader: (31)

There is no interval for pre-emptive oil pump replacement. Nobody changes the oil pump on a functional engine as a preventative maintenance item (that I know of).

The proper interval for oil pump replacement/rebuilding is "when the shortblock is rebuilt". If you have the shortblock apart for other work, the oil pump should be replaced (OEM) or rebuilt (Boundary) at that time. Boundary pumps can be refreshed at reasonable cost, contact them directly for more info.

Re-using a used oil pump on a fresh shortblock is like re-using a condom. It's not done in polite company, and if you do it, it's best not to talk about it.

North of 250whp an aftermarket damper is advisable. This will help keep the OEM sintered steel gears together. North of 300whp, you should consider an oil pump upgrade in addition to a damper upgrade.

Ted75zcar

iTrader: (2)

My money is on the VVT actuator. I am coming to the unfortunate conclusion that an accusump is the only solution. Would love the hear differently!

ST heavy doubles, +1mm OS, BE 2 shim, thermostatic oil cooler w/filter relocate and 10AN

Savington

iTrader: (31)

@Mudflap your VVT actuator is rattling. There's a mechanical pin inside it which locks the actuator until oil pressure fills the cavities. Once the actuator sees pressure, the pin is forced out of place and the actuator can moved as needed. Your pin is not holding the gear in place when the engine is off, which causes the gear to flap around for a couple of seconds right after the engine starts, which causes that horrific noise you hear. The fix is to replace the actuator. You can try a used one, I went through two before I got tired of pulling the TB and just bought a new one, which finally fixed the issue.

Ted75zcar

iTrader: (2)

Sad face.

Sav, did you ever try to diagnose what was causing the pin to not hold?

Savington

iTrader: (31)

There was wear on the face next to that pin, but it wasn't blatantly obvious exactly what was causing it. It's impossible to know whether the pin is not engaging, or whether the spring isn't holding it in place long enough, or what's exactly going on. That's a project for someone who has more patience and time than I had at the time. I am a systems guy, I isolated the issue to a replaceable part, I replaced the part, the issue went away, I moved on

Ted75zcar

iTrader: (2)

Well crud, yet another off season task and expense.

Thanks!

Flow

Is the group wisdom that you generally don't need to touch the oil pumps until rebuild time? Has anyone had a need to replace or rebuild pumps before overhaul? When swapping in second hand long block and doing cambelt, water pump, gaskets etc refresh leave the oil pump alone do we think? Does anyone here run component time in service tracking or engine data logging and trend monitoring as part of a maintenance program?

Mudflap

Thanks Sav!! I've been worrying/wondering about that for over a year! I'll get right on it and report back.

Flow

Ha! Thanks Ian, From what I understand torsional vibration is no joke. So essentially as the power pulses increase, pretty much double for most of us, or weight and resonances change (rods, pistons etc) we need to re-tune the dampers or move to a wide band solution. No place for damper deletes on these motors by the looks.

It also looks like no one does any trend monitoring on their engines to catch issues before they become a DNF?

Flow

Cheers Sav, what is your pick for aftermarket dampers, tuned or wide band and why?

sixshooter

iTrader: (12)

We would if we actually had failures here, but we don't. We experience opportunities here, but not failures.

Flow

Ha! Otaaay... I have noticed we assert all kinds of things here, some solid and smart, and some totally off the reservation. Trend monitoring work for the rest of the planet not sure what is so special about MX5s. It looks like the MS pumps out all kind of useful data that would be ideal for condition and performance monitoring. I am not a web dev but a site we could upload our sessions to that had leader boards on performance numbers and algos to trigger condition warnings would add all sorts of goodness to the community. Anyone with web dev skills want to brain storm it?