sillbeer

Just wondering what everyone thinks about using these as oil coolers? I bought one new for my s13 while I was in Japan about 3 years ago and never got around to using it. About a year ago I bought a T78 kit for my gs300 and it came with a greddy oil cooler. I thought it would be allright to use both on my 20b. I figured I could mount them off to the side instead of blocking the airflow up front. Would that be better than say running 2 stock fc coolers? Also anyone know what the greddy thermal system is?

-Destin

RETed

Overpriced Earls units repainted GReddy blue.

-Ted

sillbeer

Thanks. I told my roommate to buy the Earls units.

-Destin

onefastrx7turbo

iTrader: (5)

Yea, im going either earls or mocal. But, in the end, these should suffice for a 600hp or so 20b in az right? I mean, FD uses twin oil coolers, and its cooling 2 turbos....

neil

power hungry

Is the pic on the far right the thermal system your talking about? If so it kind of looks like a oil thermostat. In that case opens flow to the coolers when it hits a certain degree.

Turbo 3

iTrader: (3)

I run two FC oil coolers in series and it takes me about 10 minutes of driving to get my oil temp gauge to even move and about 15 to get in the 180 range, 20 minutes + for 200+ if it's above 80 deg F out. When it's 50-60's Deg F, it stays around 180.

This is under light to moderate load and street driving. Haven't raced it the car yet.

Hope that helps someone. I didn't want to spend money on aftermarket coolers when I already had two FC's from my car in the first place and they are quite efficient...almost too efficient since it takes so long for her to warm up

BLUE TII

iTrader: (9)

Don't the FC oil coolers have a thermal bypass built in for faster oil warm up?

Did you remove those Turbo 3?

Turbo 3

iTrader: (3)

I believe so.
No I did not modify them.

'Spose I should have clarified that the motor has ~300 miles on it and is still running a base tune just for break in and I do not exceed 4-5K and 5psi at the very most because I put a 5psi spring in my wastegate for break in to ensure I don't overpressure anything. I haven't been able to drive the car much in the last two months since I got it back and trips are usually around 30-90 minutes per event followed by checking torque on bolts, inspection for leaks and in general, etc, etc.

BLUE TII

iTrader: (9)

Turbo 3,

Do you have an oil thermo bypass in the front of the eccentric shaft (stock on '86 later) that is keeping oil out of the rotors for faster warm up?

I could see that making it take a while to warm the oil up. It is usually removed/disabled in a performance application to eliminate the chance of failure.

Turbo 3

iTrader: (3)

Blue; I couldn't tell you for certain but I did not tell my engine builder to remove that. We did modify the inside of the front cover to ensure oil wasn't dumping into the cover by the oil pump/galley since the stock computer OMP was removed and capped off. Other than that, not to my knowledge was that done. Do you have a picture of it on a 20B so I can see what you're talking about?

I'm confused by what you're saying as well. So if the thermo pellet is removed wouldn't that allow for oil to flow at full rate all the time and thus take longer to warm up overall? If you did have the pellet, leaving it in would cause the oil in the motor (just like a coolant thermostat) oil to warm up first inside the motor and then it opens, allowing it to fully circulate into the external coolers.

onefastrx7turbo

iTrader: (5)

3 rotors dont have the eccentric bypass pellet

BLUE TII

iTrader: (9)

Ah thanks, makes sense since they weren't imported to US so cold start emmisions were probably not a factor in design.

Turbo 3

iTrader: (3)

They did have the cold start thermowax pellet on the throttle body as I did do the TB mod on mine so if they did that I would guess that they most likely have the oil thermopellet as well. Keep in mind that with dual FC coolers my capacity is around 7-8 quarts of oil as well depending upon how full I want it to be on the stick. Oil has a great deal of energy absorption so doubling the quantity makes a big difference.

onefastrx7turbo

iTrader: (5)

nah, thats what I mean, they dont have an oil bypass pellet. Its a different setup than the 13b's. On 13B's, there's an oil passage all the way through the shaft, and ending at the oil pellet. On 20b shafts, the threads for the pulley boss dead ends; it's solid at the end. My guess is, 20b's eliminated the oil bypass partly for emissions, but also because 3 rotors have no problem heating oil up, therefore an oil bypass isnt needed

neil

Turbo 3

iTrader: (3)

Does somebody have a picture of the two shafts? Curious to see the difference...

setzep

Hey turbo 3, have you ever checked the pressure drop with two FC coolers in series? I'd have to imagine it's pretty high.

Now that's it's ~35deg F in the morning here in MN I can actually see the thermostat working in my oil cooler. The temp will rise to ~170 then take a nose dive to ~150 once the thermostat blocks off the bypass. Takes ~10 min before it will start to move the needle on my 140-240 gauge ( 5 min idling and 5 min driving).

For the $ you can't beat Rx-7 air/oil oil coolers.

Turbo 3

iTrader: (3)

No I haven't and it would be a major PIA to weld in fittings to check something that my pressure gauge already tells me at the oil filter just after the return line. You sound like an engineer asking a question like that

I have seen a definite pressure difference with and without an oil restrictor in the turbo oil inlet. The numbers I've mentioned before were with the restrictor in, without it the pressure goes down to 20 psi on a 60 deg F day that I had it out. Based upon that, I highly doubt that there is much pressure drop from having two coolers in line much more than one cooler already is, maybe a few psi but my thought is that who cares? With the doubled capacity there is a substantial greater load the oil system can take for heat exchange so if it drops even 5-10 psi but the overall volume is double the system is still much better off.

I suppose you could run the coolers in parallel but it is not nearly as efficient for a variety of reasons (pressure drop greater across one than the other, multiple oil lines and complexity of install, etc, to name the big ones).

setzep

Let me clarify a little. Say you were to "T" in a gauge right at the front cover where the oil comes out and then another gauge where the oil goes back into the engine (at the filter). This is where I'd imagine you'd see a big difference in pressure.

Are you saying 20psi at warm idle? If you'd like to raise that you can block off the OMP passage in the front iron assuming you don't run a omp.

Actually running the coolers in parallel will give you less pressure drop throughout the system. Try blowing through two coffee straws hooked end to end. Then put two straws in your mouth side by side and blow, much easier right? You're right about the plumbing though, it would take a bit more. I'm not sure this is a huge deal anyways unless you are going over the relief valve in the front cover due to so much pressure drop.

I'd just like to see how much more pressure drop there is when running the coolers in series compared to parallel. I suppose I could take one to work and put it on the flow bench but I'm lazy

Turbo 3

iTrader: (3)

Yes, 20 psi at warm idle.

I did block off the OMP as well.

Not necessarily. In an ideal world parallel would be better to reduce pressure drop but it's still not as efficient, you are making an assumption of resistance being identical between the two. By running the oil from the bottom to top it maximizes the residency time and obtains the greatest amount of exchange. The oil does not have the ability to choose two routes, only one.

My reasoning for series vs. parallel is that let's say cooler A has more resistance to flow than the other because of X reason. This in turn causes pressure to increase because it has to push harder to get through. Where does the oil want to go? Path of least resistance... so then it goes through cooler B instead. One cooler is not going to be as efficient in exchanging as much heat as the other.

Instead of pressure drop, I'm much more curious about heat exchange and would love to see temp's at the pre/post of each cooler to quantify how much is removed at A, and how much diminishing returns you get from B. Say 50% removal at A and another 10% at B (just guessing but that's why it would be interesting).

I'm too lazy as well and cheap...I don't have nor do I want to spend $ on thermocouples to satisfy a curiosity on something that works really well already

setzep

Before I blocked off my front iron I saw a tad under 30psi at idle (880rpm) now I have 40. Is mine high or is your's low? I suppose different engine/turbo combos will have different pressures.

I'm not making the assumption that they would have equal pressure drop, I know one probably would be a little different than the other but in the end does it matter? Oil is still going to move through both unless one is blocked off for some contamination reason or another (if thats the case you have other problems ). When some oil moves through one cooler a little slower that's just more heat exchange time right? But when the oil moves through one a little slower that means is also moving throgh the other a little faster with less heat exchange time so it equals out right?. Either way, series or parallel the oil spends the same time in the coolers. The way I figure is why not take some pressure drop away if you can. In parellel you'll have 1/2 the pressure drop of a stock Rx-7 with only one cooler but in series you have 2x's the pressure drop of a stock Rx-7 with only one cooler. I'm assuming a 20b has a larger pump than a 13b so the pressure drop would be even more.

I'm sure your system works well (probably too well on some days at taking heat out) but I'm just throwing ideas out there. To satisfy my curiosity I might T in a gauge before the cooler on my car to get some data, I already have a under hood gauge right after the cooler before my remote mount filter.

Turbo 3

iTrader: (3)

I have other problems as well that need to be addressed so don't use my oil pressures as being the best information out there. My motor consumes oil at the rate of about 1 quart per 30 miles and I've ruled out everything outside the motor (no oil injectors, blocked off the turbo oil feed, no OMP, no oil leaks anywhere on the motor or at the oil lines) so it must be coming from inside and on a fresh build that did this right from the initial startup... not good. It seems nothing can go right on my project...

Working at a place that uses a vast number of large industrial heat exchangers as reference they are all run in series with flow going from hot side through the bottom and working its way upward through each subsequent cooler. The cold side starts at the top and works its way down which is to minimize thermal shock and give the longest possible dwell time for heat exchange. Although ours is liquid/air vs. liquid/liquid the principle to me is the same and why I'm still going to side on the series way of doing things for now

setzep

Ouch! 1 quart per 30 miles. I'm sorry to hear this.. Did you build the engine or do you get to fall back on a engine builder?

There is no doubt that series is the way to go if pressure drop is not a concern. Having less plumbing can really help in tight areas like our little Rx-7 that already have all kinds of other things in the way when they are turbocharged (let alone a 3rd rotor in there). The only reason I brought up parallel is because of the pressure drop issues that could or could not be of concern when running high velocity oil with a relatively low pressure system.

BTW what oil pressure do you see when @ 3000rpm?

Turbo 3

iTrader: (3)

It's not necessarily the engine...don't assume I'm tracking down what I think is the turbo but it takes time do this and road time which I do not have anymore this year as you are well aware of our climate. There were two engines built identically and at the same time so why mine consumes oil and the other doesn't... don't know, but the turbo's are completely different so that's where we are starting.

Two big items that seem to stand out when looking at turbonetics web site on turbo problems is; A - blocked or plugged air filter, B - blocked oil drain line, C - blocked (or in my case) not having crankcase ventilation (oil filler neck has a hose off of it but it is not connected to the air inlet of the turbo so there is no vacuum being drawn on the oil pan).

So; next trial is to simply remove air filter and start car, see what happens. Next is to install crankcase ventilation bung and hoses with drop-out can. Last is to disconnect oil drain line and check for flow. From there we could go to removing the front cover and other engine-internal related stuff. Would much rather prefer not to do that and will start with a boroscope before it gets to that point throughout motor to see WTF is going on.

Oil pressure at anything past idle to 5K is 45 under load, and about 40 at cruise. Idle seems to want to hang back down around 20 again after I had a new turbo rebuilt (another vendor that F'd me yet again...and only after 200 miles did a new turbo fail, imagine that). The assumption now is that the turbo is fine, there are reasons why the turbo is consuming oil so that's the direction I'm headed until I exhaust those potential issues.

GooRoo

iTrader: (4)

Maybe you've already heard of this, but when you do this, you should do the Crispy secondary oil vent line like Damian and I did since you're planning on tracking the car.

If you haven't heard of it, this is what to do:

I'm pretty sure the 20b has a secondary oil return from the stock twins similar to the 13B. You take the block-off plate for that (since you have a single and aren't using it anymore) and thread in a 90 degree elbow/barbed hose fitting. Then run a oil safe hose (use some heat resistant wrap/tubing near the exhaust) to the catch can. I used a Jaz catch for a while which has 2 barbed inlets that worked nice for the two lines. I was getting excessive fluid with my old oil that was filling the can in a single session, so I ran the outlet of the Jaz to a secondary 1 quart catch tank that I mounted to the side of the engine bay. Problem solved.

I have since changed the oil to 5w40 and I no longer have to much fluid in a single session. I'm pretty sure I was getting to much because of the old (diluted) oil, and the high sustained g's of Road America. I'll see what happens next time I run there.

Turbo 3

iTrader: (3)

You'll have to show me what you're talking about. I ordered a Greddy oil catch can early this week, hopefully have it by middle of next week but the car is in storage now for all intent but I can still start it and go in the driveway. I run 5-30 for now under break-in. I was just planning on running the existing vent off the oil filler neck to the catch can which is (guessing here), about a 3/8" ID line, hopefully that's big enough?