pianoprodigy

I've been noticing quite a bit of black smoke coming from my tailpipe after I "get on it" up to higher RPMs and then let off, letting the engine wind down slowly. If I "get back on it" the smoke stops. This only occurs at high RPMs.

I went from Full to Low on the Oil dipstick in only one week. It seems like the "checkerboard" equals about a quart. I'm pretty sure these are related. Is there an oil return line or something that might be malfunctioning? The engine only has 3k miles and I'm running 10 psi on a Single Turbo.

I hope nothing is seriously wrong. I'm taking the car in this week to get the 5th gear synchro fixed, get the Profec-B installed as well as an aluminum flywheel. I'm excited to see what 20 psi will do, but I'm a little nervous because of this smoke issue.

Thanks in advance for the advice...

-Alan

rx713bt

iTrader: (4)

It's either the turbo or most likely the oil control O-rings on the rotor assembly. I hope they were replaced with new one.

-Jeff

pianoprodigy

Neither of those sound good! Am I right?

JBurer

Hi Alan,
Nice to see a fellow Tampa rotorhead on the list.

Once upon a time I had a Microtech EMS on my single turbo FD. I had the black smoke issue upon deceleration. It turned out that there was too much fuel on the higher vacuum areas. Pulled some fuel in those areas and the problem went away.

Are you doing your own tuning?

The oil issue is quite serious, however, and it sounds like it is separate (unless the smoke is blue, in which case the maps aren't overly rich - you're just burning oil).

If either of the two things Jeff suggested are true, they would be instances of gross negligence on the engine builder's part.

One could lose some oil if the intake ports were opened up past the oil control ring, causing oil to enter the combustion chamber. However, that would not cause the massive oil loss you are describing.

Who built the engine?

Email me at Jrbjag@yahoo.com.
My Best,
John

pianoprodigy

Scott at Mazsport built the engine. The weird thing is that it seems like it isn't doing it every time. The smoke is definitely black not blue. I get an occasional puff of blue smoke, but this problem is definitely black. Scott spent like 4 months building the engine. There are only like 3,000 miles on the engine, and I have not been running it hard often. I'll talk to Scott tomorrow and get his opinion. I hope it's nothing major that will require me not having my car for weeks again. It took him 5 weeks to install and tune the Microtech.

-Alan

JBurer

Sent a PM with my response....

pianoprodigy

Any other experience with this? I didn't get to talk to my mechanic today...

CCarlisi

It sounds like your problem is caused by the motor rather than the turbos.

I almost bought a motor that was ported into the outer oil seal track so I know a little bit about what the symptoms of this problem are. Dave at Kd said that a motor that has been ported into the oil seal track will let out occasional pops and puffs of smoke at idle. The port is basically metering oil into the intake stroke with every revolution. Therefore, it is most noticeable at low throttle openings (idle, cruising regardless of rpm) because the oil to air ratio is highest at these points.

Here is a list of quotes from various builders on this subject:

Racing Beat (Chris Engine tech): "Uh Oh" (after I told him the housing I was planning on using had this characteristic) He went on to say it will shorten the life of the oil seals and can break the side(or maybe it was corner) seals.

Mazdatrix: (Jeff) It can catch and break the side seals. It should not be done under any circumstances. "It is not a grey area, if the housings have been ported in this far THROW THEM AWAY."

Mazdacomp (Tim): "Bad idea....It will increase wear on the oil seals and can catch and break the side seals."

Rice Racing (thread listed below): “For the very marginal gain in port opening area (less than 5%) That porting is VERY bad practice! It will result in excessive outer oil control ring wear due to excessive exposure to raw air fuel mixture. It will not provide any gain in flow due to port timing improvement as for a large majority of the time the extra area ported is covered by the rotor side...”

Judge Ito (thread listed below): The very first lesson a Rotary Engine builder learns about porting is: never port into the center of the side housings(no gain in power or anything else and exposure to the oil seal ring is no good. https://www.rx7club.com/forum/showth...al&pagenumber=3
https://www.rx7club.com/forum/showth...hreadid=201468

I wouldn’t settle for your builder’s analysis without first getting a couple of other opinions.

Snook

iTrader: (12)

CCarlisi very informative reply

pianoprodigy check this out so you can see what he means...

striker

on the topic of black smoke, is it bad to have it under hard acceleration?

Kento

Enough where you can definitely see it, yep. Black smoke=soot=too much fuel.

JBurer

Yes, what Kento said.
However, it vary's in degrees. If it's just a little overly rich, you have the extra fuel diluting the oil metered into the combustion chamber, increasing wear.

If it's extremely overly rich, you have carbon building up on the rotors. Carbon retains heat and, if hot enough, can glow and cause pre-ignition.

Alan, what is the verdict from good ole Scott?
Cordially,
John

neevosh

Is there any gas dilution in your oil? I had this problem before my engine gave out. Exessive smoke in the high RPM range and oil consumption. It sounds like maybe your builder ported into the oil control ring path.

pianoprodigy

The car goes in first thing Monday morning. It felt very strong last night. The car is running a manual oil metering pump (i think that is the proper description) so he said that will cause the excess oil problem.

JBurer

If it's a manual OMP then it is controlled by a small 'arm' coming from the engine (for rpm reference) and a throttle linkage.

The second gens did not have this issue, nor did mine when I had a 2nd gen manual pump on the car.
Even eliminating the OMP altogether and running straight premix only calls for about 16 ounces per fillup. That would be *1/2* of a quart per week, if one week equals 1 tank of gas.

Anyone else out there with a manual pump losing 2 quarts of oil a week?
Best,
John

rx713bt

iTrader: (4)

Only if the manual pump is malfunctioning. MY 87'-88' turboII never smoked during deaccel.

-Jeff