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Discussion Starter #21
I would recommend not using an accusump. They are a band aid if you do not have another reasonable option. The Unit2fab might be the best of all available wet sump pans but might not be needed. Maybe I missed it above, what class/tires/tracks are you running with the car?
You're right it is a Band-Aid. I'm thinking the unit2fab also may not be needed because of the tires, but the typical roads and tracks (Road America, Blackhawk Farms) it will be used on have lots of elevation change, off-camber, and bumps, so I think it is particularly high risk based on that data with the NSX - which was likely on a flatter surface, but with stickier tires, so I don't know. I think generally a baffled pan is enough for street tires, since oiling failures are so uncommon - even the BTCC car used a simple baffled pan. I'll almost definitely use exclusively Bridgestone RE-71r in 255/40/17 in the front. I'll continue researching it but if there is considerable risk of very infrequent momentary oil starvation, then I think an accusump would be the cheapest solution, with the only disadvantages being greater complexity and +~4lb of positionable weight. Why would you recommend not using one?
 

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In order to run an accusump, you will likely need to add a sandwich plate to your oil filter in order to get the needed volume of oil out of and back into the accusump. I did not see any mention of an oil cooler, you will probably want one and the accusump plumbing will either interfere or complicate the plumbing. You will need a valve on the accusump. Manual valves are the most reliable but require the accusump to be within arms reach of you in the driver's seat, so likely you need an electric valve. For some reason the electric valves have a high failure rate.

If the accusump is being utilized, that means the engine's oil pickup is dry, the accusump will start supplying oil at the pressure just before the pickup went dry. From that point on, the pressure will drop as the oil flows and the air that is compressed in the accusump expands. When oil makes contact with the pickup again the pump will need to scavenge the air in the pickup to re-prime the pump. From first hand experience, I have seen this take an alarming amount of time. Once the pump is re-primed and pumping oil again, the pressure to the engine will be low because the pump is both supplying the engine and refilling the accusump. Depending on how bad the oil starvation is, this can happen multiple times during a lap.

The oil level in the engine's sump should be full when oil pressure is at it's peak. That means any time the oil pressure is lower, the accusump will have pushed out some of it's oil and the sump will be over filled. This could lead to oil windage, robbing hp and frothing the oil.

In order to reduce the dependence on the accusump, a baffled pad should still be used.

I have many years experience with an accusump in a Lotus Europa that I autocrossed and did track days with. I will never go down the accusump road again.

I am currently endurance road racing a K swapped EG civic using a Moroso road race oil pan. I have limited experience with this as we have only completed one race weekend so far, but the oil pressure was consistent throughout the weekend. We run the car on 225 wide Hankook RS4 tires.

If I were you, try to find out what pan the K powered Honda Challenge races are using. I think they are mostly using drop in baffles and the Moroso pan.
 

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I'll be using a ported RSX Type-S pump. The porting is just on the outlet side, not the suction side. The porting is detailed above...
Thanks for the reply and information.

...I used two rolling platforms with bearings for the crank and pin bores to rest on. That bearing was height adjustable.
That's cool DIY stuff, which I like 🆙. Did you add or cut off for balancing, or was it already balanced within your given tolerance?

...I leveled each connecting rod with one rolling platform on a scale and other free to roll. The balance was within .1g between the ends of all the connecting rods, so when selecting the components for balancing each cylinder I was aware of that, and able to maintain that balance. The oscillating mass is within 0.01g and the rotating mass is within 0.1g.
I understand, what you do is balancing the rotating and oscillating masses over the all 4 cylinders. My question was more the balance of the crank assembly, once it get spon to a certain engine speed you have forces, once analysed on a harmonic approach, of 2nd order. These forces are bounded to Newton's 2nd law (F = m x a). So the engine builder is interested to reduce the mass, as the acceleration is given by the crank assembly kinematic and engine speed. There are many ways to reduce those, but what else is done is what we call in Germany "Massenausgleich", which is like a rotating mass, which has a counter weight will not cause a rotating force. Within this particular mass balancing (= Massenausgleich) you also can reduce the effect of the oscillating forces by placing a counter weight on the crank. Now the factor I was asking explains the mix of oscillating and rotating mass which is balanced by an counter weight.

Just to give you and example. The rod and piston assembly per cylinder has 850 g in total. According to a rod balancing measurement 350 g are related to oscillation and 500 g are related to rotating mass (you may know the approach to get this measured?). Now the question is, how much mass you want to put into the counterweight to balance those dynamic forces optimal? Typically the two counter weights of each big eye of the crank have a 30 % to 60 % balancing, which means 100 % of the rotating mass plus 30 to 60 % of the oscillating mass are included into these two counter weights.
The higher it is, the lower the oscillating forces in vertical direction, but the higher the forces in horizontal direction. For an 99 mm stroke application this is a vital number, as the impact on engine safety is much higher then the imbalance on a few 1/10th g of mass on each cylinder. I am not saying it is not important to balance the weights over each cylinder like you do it, but you whip out the main reason of balancing of an 4 cylinder engine when you don't focus that balancing factor right for your application.

Ah, not to forget, the 60 % balanced counter weights of the above mentioned examples are 500 g + 0.6 x 350 g = 710 g per cylinder (added to the balance weight difference of big eye and counterweight only). With that design the vertical forces are lowered. Just the question which stays open, what balance factor does your application need. For me a 99 mm stroke engine has an bigger demand on the vertical ones.
 

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Discussion Starter #25
In order to run an accusump, you will likely need to add a sandwich plate to your oil filter in order to get the needed volume of oil out of and back into the accusump. I did not see any mention of an oil cooler, you will probably want one and the accusump plumbing will either interfere or complicate the plumbing. You will need a valve on the accusump. Manual valves are the most reliable but require the accusump to be within arms reach of you in the driver's seat, so likely you need an electric valve.

When oil makes contact with the pickup again the pump will need to scavenge the air in the pickup to re-prime the pump.

Any time the oil pressure is lower, the accusump will have pushed out some of it's oil and the sump will be over filled. This could lead to oil windage, robbing hp and frothing the oil.

I am currently endurance road racing a K swapped EG civic using a Moroso road race oil pan. I have limited experience with this as we have only completed one race weekend so far, but the oil pressure was consistent throughout the weekend. We run the car on 225 wide Hankook RS4 tires.

If I were you, try to find out what pan the K powered Honda Challenge races are using. I think they are mostly using drop in baffles and the Moroso pan.
That's pretty convincing. You're right, it's not very good at it's job and has several trade-off inherent to it's function, therefore is best used as a fail-safe rather than to depend on. Since I'll be using the car mostly on roads, it may make the accusump needed infrequently enough to warrant it, but the big unknown we've identified which will determine that is the cornering g and effectiveness of pan baffles, which I think we don't have enough information now to accurately judge. Therefore a different pan may be better.

The potential for windage is probably greater than I was visualizing or hoping for. I think that alone might be enough to push the balance in favor of a better pan.

I've installed a DC5 factory oil cooler onto the engine. If I needed to add an oil cooler, you're right, it makes the accusump less appealing for many reasons. Because the DC5 oil cooler is water-cooled, I've wondered how effective it would be to run a better radiator setup versus an additional air-cooled oil cooler.

Unfortunately EP3 and DC5 can not accept Moroso oil pans because they interfere with the subframe.
 

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Discussion Starter #26
Thanks for the reply and information.

That's cool DIY stuff, which I like 🆙. Did you add or cut off for balancing, or was it already balanced within your given tolerance?

Just to give you and example. The rod and piston assembly per cylinder has 850 g in total. According to a rod balancing measurement 350 g are related to oscillation and 500 g are related to rotating mass (you may know the approach to get this measured?). Now the question is, how much mass you want to put into the counterweight to balance those dynamic forces optimal? Typically the two counter weights of each big eye of the crank have a 30 % to 60 % balancing, which means 100 % of the rotating mass plus 30 to 60 % of the oscillating mass are included into these two counter weights.
The higher it is, the lower the oscillating forces in vertical direction, but the higher the forces in horizontal direction. For an 99 mm stroke application this is a vital number, as the impact on engine safety is much higher then the imbalance on a few 1/10th g of mass on each cylinder. I am not saying it is not important to balance the weights over each cylinder like you do it, but you whip out the main reason of balancing of an 4 cylinder engine when you don't focus that balancing factor right for your application.
They were already balanced within the tolerance, and I was able to improve that by matching each rod to a particular bearing, pin, and ring locks.

I haven't given rotating, 2nd order harmonics that much consideration. I'll research it. It sounds like that by changing the amount of counterweight on the crankshaft we can either reduce the amplitude of the momentary spike in crankshaft forces, which cause 2nd order harmonics, by adding inertia to the crank, or we can reduce the rocking-couple imbalance inherent to inline 4s by reducing the weight of the crankshaft counterweights. Therefore we must basically select the minimum amount of counterweight needed to protect against strong 2nd order harmonics.

It reminds me that the TSX crankshaft is lighter than other k24 cranks, yet is uses heavier piston/rod assemblies. It concerns me that in this engine the crankshaft is much heaver compared to the piston/rod assemblies. I'll see what I can come up with using a search, and a may call some specialists and see what they say. If you have a way to calculate the correct crankshaft counter weight, even very roughly, please chime in.
 

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Discussion Starter #27
Sorry I can't, that was over 20 years ago...paper pictures only 😂.
The roads here make it easy to use the road surface to move the car with more force, so setup changes to assist in tire loading aren't particularly advantageous. I think generally such setups are used to improve time across a section(s) of the course where the car's fundamental design makes it difficult to load certain tires. I think setup changes like those are what tend to give a car a distinctly oversteer or understeer behavior - the idea is that any usage of the tires that is lost from an understeer or oversteer-prone setup will be more than made up for on other section(s) where a tire(s) may not be used much at all. On a hillclimb course in an FF, it can be particularly difficult to load the front tires, which can be even more problematic because the front tire grip often determines how well the rear tires can be used. Such cars would require setups that made it easier to load the front tires or to slide the rear. I think that's why FF setups that make the rear easier to load and slide, and are therefore oversteery, tend to be more successful.

The roads here are generally high speed with long, sweeping corners with very few or no very-low-speed corners or hairpins, and lots of elevation change. Because of that, stability, and the improving how the rear slides at higher speed outweighs the understeer that setup may cause on very low-speed corners or hairpins, because they are so infrequent. Jordan Cox's EG6 is a fun example of an extremely competitive FF without any significant understeer or oversteer tendancies.
 

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I've installed a DC5 factory oil cooler onto the engine. If I needed to add an oil cooler, you're right, it makes the accusump less appealing for many reasons. Because the DC5 oil cooler is water-cooled, I've wondered how effective it would be to run a better radiator setup versus an additional air-cooled oil cooler.
The factory water-to-oil oil cooler is a great choice if you are not going to be producing huge hp over a long duration. you should not need any more than that. We put one on our k24 swap and oil temps peak at 220 deg F and hold there for hours on end. We run a stock S2000 radiator and it provides more than enough cooling.
 

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If a Moroso pan will not fit, I would probably go with a Clockwise Motion drop-in baffle and TracTuff oil pump baffle.
 

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Discussion Starter #30
LotusElise, I've decided to ignore synchronizing the crankshaft counterweights to the weights of the piston/rod assemblies for now. I'll continue researching, so it;s possible I'll change my mind. I'm reassured thinking of how many engine build have neglected this, and survive today. Furthermore, the weight of each rod/piston assembly is much closer to the weight of the factory parts than other aftermarket parts which are more commonly used. However, I don't know whether the danger increases as the weight difference between factory and aftermarket parts increases, or how exactly 2nd order harmanic frequencies correspond to piston/rod and crankshaft imbalance.

I'm now at the stage of assembly where I should install an oil pan. I've ruled out the accusump AND Unit2Fab oil pan. The Unit2Fab oil pan is an absolutely terrible fit on the dc5/ep3. I've attached photos that Unit2Fab sent me showing how much material must be removed from the subframe and how one customer modified their subframe for clearance. Unit2Fab also told me that their aluminum pan which we've been talking about, was developed to cope with sustained 2g+, and 3g spike loads that were causing the recorded momentary oil pressure loss, which I imagine is greater than what this car will see. They also said that their steel pan, which has a relatively simple and conventional baffle, is suitable for "mild" time attack, and has been tested and verified to have no detectable oil pressure loss. This is valuable new information as so far the company has published oil pressure datalogs of only their much more expensive and exotic aluminum pan.


Here is what Unit2Fab said:

"we also offer a... stock capacity steel pan. we've used
everything we've learned on the elite [aluminum pan] and incorporated it to fit within
the stock pan. ... This pan ... is still used on
many fast touring cars builds and mild-time attack cars and have never
seen a dip in oil pressure to date.

The elite was simply made to be the best there is in terms of a wet sump
and that's simply what it is (sustains solid oil pressure even when
subjected to spikes of over 3 gs and sustained 2 g+ loads). In order to
sustain solid oil pressure on some of these wild unlimited-time attack
cars.

I know you mentioned a accusump, but from our experience and experience of the
people around us. No one has ever had success with them. By the time the
accusump kicks In it's already too late and the engine has been damaged."


The man was very friendly. I'll talk to him about their baffle development and theory, since he said he'd love to help find a solution. It looks like I'll use a custom baffle on one of the stock oil pan, and will see how cheap and easy I can make the design to help people replicate it. Once I finish the oil pan, progress should really accelerate; I'll have the car on the road in May if at all possible.



notched 1.jpg pci elite 2.jpg pci elite.jpg
 

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However, I don't know whether the danger increases as the weight difference between factory and aftermarket parts increases, or how exactly 2nd order harmanic frequencies correspond to piston/rod and crankshaft imbalance
It is a question of engine speed, duration and load. It won't damage your engine in a moment like accidentally. It increases wear and friction slightly with increasing speed given that there are significant imbalances. A 12,000 rpm engine is factorized more affected by those as an 8500 rpm engine. Difficult to get beside quality quantitative figures to that without knowing the imbalances, ... .

Here is what Unit2Fab said:...
I know you mentioned a accusump, but from our experience and experience of the people around us. No one has ever had success with them. By the time the accusump kicks In it's already too late and the engine has been damaged."
Thanks for the reply of your their answer, which is very helpfully experience of them. If their wet sump system can handle 2+ g accelerations in all directions (except the one down to earth 😉) I think most chassis carrying race cars would be fine with it. Formula cars definitely not, but low aerodynamic race classes with higher barycenter to wheel distance to weight ratio are doing hard (even on slicks) going above 2.5 g. I checked out their (Unit2Fab Elite Steel pan) product, the oil pressure measurement of before and after looks convincing.
 

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Discussion Starter #32
It is a question of engine speed, duration and load. It won't damage your engine in a moment like accidentally. It increases wear and friction slightly with increasing speed given that there are significant imbalances. A 12,000 rpm engine is factorized more affected by those as an 8500 rpm engine. Difficult to get beside quality quantitative figures to that without knowing the imbalances, ... .
I'm guessing that having certain combinations of crankshaft counter weights and piston/rod assembly weights would cause either more frequent and/or more powerful harmonic vibrations. i.e. a smaller imbalance might make harmonic vibrations occur more frequently, and a heavier imbalance might cause harmonic vibrations to be more powerful, but decrease the frequency of harmonic vibrations... I imagine there would be small harmonics, where energizing the harmonic would occur every second, third, fourth, etc. revolution, and big harmonics that would be energized every revolution.

If the combustion force, rpm range, and weight ratio between the crankshaft and piston/rod assemblies were the same, I'd guess that a lighter rotating assembly would cause small harmonic vibrations to occur more frequently, and a heavier rotating assembly would cause vibrate harmonically less frequently but more powerfully, due to greater inertial resistance to combustion forces, but greater mass. I'd guess harmonics at which the vibration was energized every revolution would likely occur at a similar number of frequencies between the light and heavy rotating assembly engines, so the power of the harmonic vibrations should always be considered. Small harmonics would be insignificant compared to harmonics energized by every revolution; problems would occur when the force of the harmonic was great enough to penetrate the oil film of the bearings. A high-revving engine might have more to gain from precise crankshaft counterbalancing if it were more likely to encounter strong imbalances more than once throughout the rpm range. Larger clearances and thicker oil i.e.~0.002, 10w-40 might be a crude but effective way of protecting an engine from those strong vibrations. A more rigid crankshaft would be another crude way, making me think it might be significant that the k24a2 crankshaft is more rigid than the other k24 crankshafts.



Will you link to the data you saw on the steel pan on their website please? I couldn't find it.
 

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Nice project! And a good read.
As far as the oil starvation problems go. I think in your situation your already fine with a clockwise drop-in baffle (Skunk2 replicated it also) It holds up to 1.3~1.4G spikes just fine and with the tyres you named your not going above that number without any significant amount of downforce. Also let's you keep the aluminium sump wich further helps with oil cooling and rigidity 🤷‍♀️
 
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