chuyler1

iTrader: (1)

I'm trying to wrap up the finishing touches on my build and I'm stuck with these issues...

1) Off throttle coasting between 1,800-3,000 RPM is violently rough causing the whole car to shake
2) I see puffs of smoke between shifts at redline if I lift off the throttle too much
3) Today instead of shifting, I just lifted off the throttle at 7,500 RPM and it left a trail of smoke behind me...grayish.
4) I'm burning about 1 qt of oil every 500-600 miles
5) The AFRs on the front rotor seem to be low at idle and high off throttle compared to the rear. Example, at idle, the ECU keeps the rear rotor at 13.7 but I'll often see 12.7 and as low as 11.7 on the front gauge. Cruising they are both pretty close around 14. Off throttle the rear will be at 14.7 and I'll see high 15 and the occasional 22 from the front.

A little bit more about the setup...

It's a big street port 12a but it idles fine at 1,000 RPM at 13.3-13.7 AFR. It was recently rebuilt with used, but in good shape, plates and housings that came out of a vehicle with 60k miles on it. The OMP is hooked up and squirts oil before the throttle plates. I have tried disconnecting the OMP hoses and dumping them into a catch can and pre-mixing for a few tanks to see how much oil is actually getting delivered. I found maybe 1/4 quart of oil dispensed into the catch can after 600 miles. That leaves 3/4 quart getting lost elsewhere. No puddles forming under the motor when I park it and everything looks generally clean under the hood.

The AFR swings could be explained by a vacuum leak but I have not been able to find one. I have run the car with just the MAP sensor hooked up, no brake booster, no EVAP, etc, to eliminate variables and it still shudders. I sprayed carb cleaner all around the intake manifold and didn't hear any changes in idle.

With the smoke from shifting, I have read that it could be PCV or purge valve related, but I tested the purge valve and it will open with any positive pressure from the crank case side but it doesn't let a ton of air through. How did the Nikki handle positive crank pressure? I see on the rats nest the upper port on the oil fill neck branches out with one end going to the purge valve and the other going to the carburetor. Is there a PCV in there or is it just let free air release into the carb? What I'm getting as is, do I need a PCV in addition to the purge valve?

Some other searches lead me to people claiming this behavior could be oil control rings. On a fresh rebuild though? I don't get any smoke at startup which is the other symptom of oil control rings.

I'm tempted to tap some new vacuum ports on the manifold so I can move my vacuum lines elsewhere and reinstall the idle adjustment needles. However, I don't think the issue is with a balance between the throttle bodies...they are linked by the vacuum lines just like many 4 cylinder engines that come with ITBs. I don't want to tap new holes only to find out it didn't make a difference at all.

Oh, and as far as timing goes, I'm running direct fire and off throttle advance is around 25 degrees in the RPMs where the shudder is worst. Spark split is 10 degrees. I've tried lowering the timing and it doesn't help. I even tried reverse ramping the timing as suggested by Andy from Adaptronic for heavily cammed/ported engines but that didn't do anything either. The shudder is quite undesirable and makes the car almost unbearable to drive in traffic if you try to one-pedal drive using engine braking. I can usually manage it but if someone is in the car with me I'm afraid they will get nauseous.

There is one solution that sort of works...throttle off overrun. If I turn this on with maybe 100ms delay it eliminates the bucking by shutting off the injectors at 0% throttle position. It only works while coasting. Once I touch the brake pedal the overrun disengages. I don't know how the ECU knows i'm braking, perhaps its the change in MAP reading, but overrun in general just makes for jerky driving in other ways. I will eventually enable it, but I'd like to solve the problems it masks before I do.

GSLSEforme

1)Can you duplicate this by pushing in clutch and coasting to separate driveline from engine to rule that out,have you tried this? I think this is a fueling/timing issue. Eliminate the driveline thing so as not to chase your ***.
2) Possible the streetport timing is aggravating operation of valve,is there evidence of oil on intake side of valve/hose? You may need to delete,for testing and run a pcv valve in its place.
I'm not sure what you have for metering oil setup,if not using oe id lines something larger id,doesn't take much,capillary action is effed and oil is sucked out of lines into engine.Where are you tapped into,throttle bodies,intake manifold?
3) Oil consumption/burning,what your're using oil wise is way too much...oil control rings well could be the culprit. Were the irons lapped? I'm not looking at your engine guy,but i would question the run to NC and back with a low miles after rebuild engine,i'm very conservative with something like this and wouldn't consider a run like that on a low miles not fully sorted engine. Like a piston engine,more so with a rotary,breakin period is critical.
All the dickering around with the fuel/ignition system,trying to get it right-on a new engine is something that would concern me to the point of not doing it. When i have done this,both for my own cars and for customers,i have a test mule car with a known good fuel/ignition system that i put the engine into for several hundred miles to 1k miles to break it in running it "normally". Once broken in and sorted,oil changed-goes in customers car and fuel/ignition mods they have or i'm doing is done on a known sound engine. Any problems arise proceeding from this point,i know it's not the engine mechanically causing it. I realize everyone doesn't have a mule vehicle to do this.It's not practical.

This is a much easier/logical scenario i will employ on an engine i'm building for a truck i'm restoring. The engine will be converted to FI,this is a carbed truck. I'm near done building the engine and i will swap in the engine and get running and break in the engine for couple thousand miles and then install the FI system i have chosen and dial it in. I do not expect problems,but if i have to deal with some abnormalities with system such as overfueling, i'll be concerned til getting things 100% but not as worried as if this was a 1st fire of engine.
4) Do you have a distributor with igniters,wiring and oe coils you can swap in,disconnect coil feeds...ignition system you had in car before this to eliminate ecu timing abnormalities for testing?

5) 1st thing i would do regarding AFRs differential between rotors is swap injectors and see if fueling quirk(s) follow injectors. If it does,i would have injectors flow tested-after i had consulted manufacturer/supplier or they may send you a replacement pair if still in warranty period. If the problem stays with same rotor,ecu/mechanical issue,vacuum leak needs to be investigated. Does your ecu provide real time individual injector duty cycle,can you datalog this and compare to associated AFR readings,or do you have that info already? Intermittent ecu issue or problem with it,possible to run your problems past the seller or techline they may have?
A lab scope is another option for same injector info.
6) Time to contact your engine builder,if you haven't already?

Don't take my responses personally,they're not meant in that context. Responding to each of your points,with some knowledge of prior posts,though not all,possibly misremembering some of them.
I'm old school and been doing this a long time. Some of the things i suggested,especially break in procedures may seem convoluted. I have and am still enrolled in the school of hard knocks,i reserve the right to do dumbshi* occasionally,i do things the way i do from learning the hard way,defective parts,unscrupulous customers,etc.
Last,i have no hands on working knowledge of the Jenvy parts you're using.

chuyler1

iTrader: (1)

problem goes away if I push the clutch in or switch to neutral. Problem goes away if I enable overrun (injectors shut off) so it’s clearly fuel/air/ignition driven and not mechanical.

no oil on the hoses between intake and purge valve but clearly oil on hose between purge and oil fill cap as it has stained the blue silicone. The port timing could definitely be part of it, I didn’t know if this was common behavior for big ports or bridge ports and people just deal with it.

not using original lines, but they are very small internal diameter. They run to the throttle body on the air filter side of the throttle plates and drip down into the air flow. Inside of the air filter gets a bit oily with this setup because it’s side draft.

The irons were not lapped. i put 1,000 miles on the motor before DGRR, 300 after getting it started with a safe 12-13 AFR tune and I kept it under 5,000 the whole time but did a few hard pulls, changed the oil after my first drive, the builder put 300 on it including dyno time, and I drove it for a few weeks back and forth to work before making the trip to DGRR. I changed the oil again before DGRR but it was already consuming oil at that point and I was putting in 1/2 quart every fill up.

The problem was there with both intakes. I think I set a very aggressive overrun setting to make it manageable. That works as a bandaid, but as I mentioned, overrun won’t engage when i’m on the brakes so it’s no good for the track days.

i have the stuff, it would take quite a bit to swap things over, not the kind of effort I want to get into to just to verify engine timing. I set 0 degree timing on the engine and the ECU is running the ignition map the builder set. I’ve tried raising and lowering timing in the off throttle cells but nothing really helps. I even tried just setting static 10 degree advance to see if a stable advance would eliminate it, but it doesn’t. With timing fixed, I see the rpm and map jump around in the logs still like the engine is fighting itself. I tried lean fuel settings and rich fuel settings too. Lean causes misfires on the front rotor, rich does nothing to help.

Didnt think about swapping the injectors. I’ll try that tomorrow, should only take 5 minutes. The ECU can log injector duty, and i have tried trimming it to even out the AFRs but it took about 5% to start making a difference and then the motor started running rough. I suppose it could be an issue with the O2 sensors or the Innovate controller. I did do some swapping around of sensors and inputs on the wideband but never got any conclusive data. I also recalibrated them a few times thinking one wasn’t calibrated the same. The difference in AFR is lower on my priority list, but i mentioned it just in case it related to the shuddering problem. Even the original motor showed a difference between front and rear but I don’t have any video or logs to see if it was this much.

its really hard to get him to work on the car, his full time job is working on spec Miatas, but he’s in charge of all rotary projects at the shop. They tend to take a back burner during race season. It’s not cost, i’d happily pay someone to just fix this, if I don’t figure it out soon I’m just going to drop it off with him and tell him I’m not picking it up until it’s sorted...but I want to try everything I can do myself first.

Thanks for your input. I don’t think any of this is related to the throttle body as it’s a relatively simple device. It could however be related to using a MAP based tune with ITBs instead of TPS. I’d have to start over from ground zero with the tune if I made that switch. I’m hesitant because it behaves so well the rest of the time.

I think tomorrow I will swap the injectors and maybe just disconnect the hose between the purge and oil fill and run a make shift catch can to see if I still get plumes Of smoke between high rpm shifts.

chuyler1

iTrader: (1)

Swapped the injectors no difference.

Disconnected the purge valve and just vented to a water bottle, no difference.