I got a new PLX wideband for my 1991 FC and noticed it was burning rich. The original MPG for the RX7 is listed at 24mpg. I was getting 14mpg around town and 20mpg on the highway.

I thought having an aftermarket computer installed and a dynotune would help get my MPG up. So I drove it from Utah to Lucky7Racing in Duarte, CA. They called me up saying it was ready and I told them I'd be out on September 15th to pick it up. Then I got a call saying it wouldn't start and they were working with Adaptronic on firmware fixes. Then they said they did compression test and it was really bad and the engine would need a rebuild.

I flew from SLC to LAX and then took two hour train to Duarte to get my car. On my way home my EGT was hitting 1700F going uphill at 5000 RPM. It was impossible to drive over 80 MPH without EGT over 1300 F.

After I stopped for the night I checked my oil in Cedar City (about 400 miles driving with too much oil) and found 2.75 quarts of excess oil in my engine. Car ran a lot better after taking out the extra oil, but it still is stalling when I stop at a light and it chokes out around 6000 RPM. The EGT is lower though.

Lucky 7 Racing is saying too much oil would create lots of smoke out the tailpipe. However, that wasn't the case. The only thing that changed is the rear rotor lost compression and it drives like crap compared to when I drove it to their shop.

Question is, what will putting 8 quarts of oil do to a 1991 13B?

 

eh wont do ****...

it will just burn the extra until its under 6

 

Yeah, our sump has no moving parts (like a crankshaft) in it, so windage isn't an issue. I can't think of a repercussion from overfilling unless it's from case pressure or oil drainback.

Your current problems all seem tuning related to me and isn't that what Lucky 7 was supposed to deal with?
I've seen them mentioned here before and have no personal/business history with Lucky 7...yet cannot help but feel suspicious about going from "She's done, come and get it!" to "Needs a rebuild!".
Especially after a new ECU and tuning session.

If the work was done and good enough to arrange pick up, presumably there is a dyno sheet confirming it was all intact and functional at some point before mysteriously failing.
It's not clear from your post if Lucky 7 actually did any rebuild work or where all the extra oil came from...both interesting questions.

 

clokker, I agree it's very suspicious. They didn't do any rebuild work and they charged me for an oil change. I checked the oil was full before I dropped the car off. The extra oil showed up between me dropping off the car and driving home.

The engine was rebuilt three years ago. Compression tested it before I bought it and all chambers on both rotors were 89-92 psi. Now after having Lucky 7 Racing work on it the front rotor chambers are 69-72 and the rear rotor is 0.

I didn't get any dyno charts, but they sent me this video. Looks like it's running great! However, now at 6000 RPM it chokes out and I fear doing anything other than taking my foot of the accelerator.
https://www.dropbox.com/s/gn1lpm3gc9dnn5m/Video%20Aug%2010%2C%208%2014%
2053%20PM.mov?dl=0

Found this other thread from 10 years ago. https://www.rx7club.com/3rd-generati...ch-oil-498782/

 

high oil pressure from to much oil can damage a TURBO... or any of the control systems.. but not the rotary engine itself.. your question is what it will do the the 13b. the engine.

 

OK, I read the 10 year old thread and have a question...
Our oil pan is just a box with oil in it. Oil drains back and oil gets pulled out.
So where is all this pressure that's "pushing oil where it shouldn't be" coming from?
The output of the oil pump hasn't changed, seems to me the only change is the reservoir of oil has increased but I don't see how that takes out an engine.

The rotary is in no way comparable to a piston engine in this respect.
Our sump has no moving parts to create pressure differentials (such as pistons rising and falling in the crankcase) and windage from the crank does not exist, so, other than a potentially leaky sump>keg interface, what's the harm?

 

lol this too i pondered.. how can a rear or front seal push out. well if you think about it, the front is part of the pan sump.. but i would think it more likely a old weak seal that needed replacement that got some help from higher then normal sump pressure... however the PCV system is meant to keep out positive pressure for that reason, so you need a pcv system failure, and you need to over fill the system. i think after putting GALLONS of oil in you COULD clog up the PCV.. though on these cars its not a normal pcv system... so maybe not.

 

Again, what pressure?

 

Blow by gases? Also, the main oil drain for the rotating assembly is the center plate. What if the drain is filled with oil?

 

Does anyone saying it won't damage the engine have a NA engine and willing to put in 8 quarts of oil to prove it?

 

 

I've not asserted that overfilling won't hurt an engine, I've questioned the proposed mechanism by which it could.

I think maybe TonyD might be on to something with the obstructed drain idea.

My particular NA does a fine job of keeping me busy without poking sticks at her to see what happens, so no, I cannot volunteer for the experiment.

More interesting than parsing the effects of the extra oil is the question of how it got there to begin with. I'm still unclear as to how you went from ready-for-pickup to needs rebuild and why it left the shop in an unfinished state.

 

i work full time as a technician. i see alot of bmw and vw systems that have a pcv valve build into an oil trap, when that goes bad they can smoke and blow out rear main seals, until you get a new pcv.
providing i can leave the oil cap off the car, or open vent the crank i would throw 10 quarts in my n/a car to prove a point, but the n/a car is waiting on it's ecu and tuning so it will be a few months.

 

I called up Extreme Auto in Layton, UT this morning. An RX7 enthusiast cornered me in the parking lot at Lowe's a week before I drove out to California and talked my ear off about RX7's and insisted Layle at Extreme Auto is the best RX7 mechanic.

I don't know about that claim, but Layle just told me that me compression is fine. He suggested Lucky 7 Racing might have falsified the rear compression to get it out of their shop, or to get me to spend another $4000 to install a new engine. Layle says my throttle sensor is bad and without a MAF sensor he's not sure how it could properly inject fuel. Not saying he's correct, but I need to find a new throttle sensor to find out. Lucky 7 Racing is telling me the Adaptronic doesn't use the MAF sensor and instead uses a MAP sensor.

Does anyone have a used throttle sensor they can sell me?

 

I don't know, I'm no expert but lets think about this. I really don't think you could get to the center plate e-shaft clearance holes with 2.5 qts of extra oil but (some would fill the front cover, drain voids in the end plates), what if it was filled to there, or over e-shaft center line? I think oil foaming would be ridiculous, this is already an issue when racing these motors.

 

my take aways are
Layle says without a MAF sensor he's not sure how it could properly inject fuel.
Layle at Extreme Auto is NOT the best RX7 mechanic.

also it is possible to have no compression on the rear rotor because of flooding, and after getting it running compression returning.

 

Yeah he may not be the best RX7 mechanic, but maybe the best in Utah. He's the only rotary mechanic I could find in Utah.

How would a stock computer know how to properly meter fuel with no MAF sensor and a faulty TPS?

Interesting idea on the flooding. Certainly there was a lot of unburnt fuel coming out of the exhaust.

 

your car is now running a adaptronic correct? they don't use a maf for fueling they use map. as for tps being faulty would create faults with acell enrichment. was it actually to much oil or fuel laden oil? as if it did have low comp and lots of blow buy it would fill sump up after a long drive. combined with a rich tune would increase the rate in which sump would fill

 

By using "speed density" instead of mass airflow to calculate the fuel injection.

Electronic Fuel Injection Mass Flow vs. Speed Density - Hot Rod Network

It's funny really. Us RX7 owners try and run away from MAF and go SD when classic muscle car people with EFI are begging for MAF. The factory resistor based AFM sucks and I wish there was a good plug and play, hot wire, MAF to replace it, but there is not. With an aftermarket computer, yes, speed density is the easiest and cheapest method, but MAF is WAY more accurate...but expensive.

Edit: To add, the N Alpha method specified in that article is how a carb works...waste of money to use a computer to do that.

 

from my experience with a drastically over filled engine.

on a T2, I was getting smoking out the exhaust from the turbocharger, engine was probably around 3-4 quarts over. ran it like this only for 30-40 minutes total. then discovered this, drained to normal level. car had zero issues after this.

with the oil level so high oil drain backed up in turbo, and id imagine the front counter weight and oil pump chain were probably whipping up the oil

 

There are a lot of posts in this thread which seem to insinuate that oil level has something to do with oil pressure. It does not. Well, unless the level is too low for the pump to pickup.

Oil pressure is set by the pressure regulator on the rear iron. Over filling the sump will not increase oil pressure.

 

Precisely the point I less succinctly tried to make.

 

Suck what?

 

Yes it has an Adaptronic that uses MAP. However, I'm wondering why it ran fine with the stock computer and MAF and after Adaptronic and MAP it runs like crap, but maybe the TPS went out while they had it at Lucky 7 Racing.

It was almost 3 quarts too much oil in the engine. Not sure what you're saying, but I didn't see any separation layers if that's what you're asking. It ran a little better after draining the extra oil. Super high EGT around 1700F, my guess is from fuel being burned in the cats.

Got a used TPS on the way. Curious to see if that solves the problem.

 

I was just going off the info you had stated.
you said that you were told it had low comp. when side seals clearance is to high(low comp) and there is blow buy in conjuction with a rich tune you can see the sump fill up slowly. the fuel mixes with the oil and dilutes it. you won't see a separation layer but will be able to smell it. hence looks like you are gaining oil. that was a possibility that sprang to mind with the Information I got from you. I have seen it a few times now on low compression engines that have been driven like that for a period of time. in your case you stated you had driven 400miles after told was low on comp.