My 7 has been down for quite some time awaiting the arrival of a GT35R single kit. Right before I parked it, I installed a wideband O2 sensor and gauge. While driving I noticed that the car was running extremely lean...often in the 15:1 range, it was so lean that I thought the gauge was wrong (Innovate XD-1). So I parked the car much earlier than I had planned..

I didn't think much of it because I was not ever driving the car hard, and it wouldn't be long until the single came in and I would be overhauling every major system on the car.

So now I have the car totally apart. I pulled the turbos off last night and to my suprise the inside of the turbos looks like it is powdercoated white! The inside of the turbines is white, the inside of the exhaust manifolds is white, the inside of the downpipe is white...

The car starts right up...hot or cold...doesn't smoke AT ALL, minor condensation on cold morning starts...but goes away before the engine is even at operating temp. The car ran fine while I was driving it, of course I was never beating on it...but it cruised nice, accelerated when asked, didn't hesitate...

The car was for sure running lean, my question would be: Is all the white residue a symptom of some other problem? Would I have other symptoms if a coolant seal was bad? (My car was using a tiny amount of coolant, but I found a decent sized leak where the water pump mounts to the wp housing, I figured that was where it was going.)

Can you run lean with no damage to the engine if you are never in boost? Somewhere i heard that it isn't a lean condition that kills a rotary it is overboosting....



Anyway...I am kinda worried because I just spent probably $6000 getting the car ready for the single, I really dont have the money left to go into the engine. Any one have any words of comfort...?


mods on the car when it was running....

Street port (or similar, prior owner never told me the exact porting)
down pipe
HF cat in a 3" mp
RB dual tip catback
power fc
PFS IC
PFS intake

Innovate WB O2 gauge

 

The tan (or white, which is more severe) deposits in exhaust and on plugs indicate a clean burn that is far too lean for a turbo rotary. I see it a lot on clean running FC NA rotaries. IF a turbo car has a tan/white exhaust, there is a definite problem. Your gauge is right. Even a stock FD with no mods does not run anywhere near that lean. I suggest you examine your tune, injectors, etc. to find the issue.

 

The injectors will go to RC tomorrow.

The tune will obviously be changed with the single turbo going in. I just want to know if I need to pull the engine before I even start installing anything back into the car.

The fact that the car still ran ok was my only positive sign that I might not need to pull the engine. At this point I was just looking for advice.

Can I run a compression test with a piston engine tester? Would that tell me anything?

I think losing an Apex seal would definately give me more symptoms though...

 

[QUOTE=RotaryResurrection]The tan (or white, which is more severe) deposits in exhaust and on plugs indicate a clean burn that is far too lean for a turbo rotary. I see it a lot on clean running FC NA rotaries. IF a turbo car has a tan/white exhaust, there is a definite problem. Your gauge is right. Even a stock FD with no mods does not run anywhere near that lean. I suggest you examine your tune, injectors, etc. to find the issue.[/QUOTE/




My exhaust tip is white when I run any gas containing lead(race gas). All unleaded fuel it stays black. Have you ever heard of this? I do not run any higher boost w/ the race gas. It is just cheaper to mix Av. gas w/ 93 (50/50) because that is what I was tuned on. 100 octane unleaded pump gas is about double that of 100LL Av. gas and probably not as high quality. G

 

Oh yeah, race gas will run white, but it is a different shade, sort of like chalk. That's normal.

 

IF you're asking if the constant lean condition ruined the engine, it's doubtful, you would have known if you had broken a seal. A compression check with a piston gauge will tell you the overall health of the engine, i.e. 90psi, 110psi, etc. Running lean in itself won't hurt the engine, running lean under high boost (8psi or more) CAN, but not necessarily WILL. Every situation is different...some engines let go with 11.0:1 afr, some hold together at 13.5:1. IF it runs normally and shows decent compression right now, then you got lucky and all that time running lean didnt hurt you.

 

I had those deposits, I think they were from the injectors needing cleaned and running lean. I haven't pulled the exhaust apart to check since they were fixed.

Dave

 

My manifolds all the way to the MP end of the downpipe look like they were coated in baby powder (or similar).

on the plus side, that makes them look really clean!

Another good thing to note is the previous owner had the turbos ceramic coated. Makes them look nice and I am sure keeps heat down a tad. They are in perfect shape and will be in the for sale section here shortly.

 

As you approach the MP though it gets back to normal and the midpipe actually is black on the inside. Kinda strange that the gas changes color like that.

 

Under what load was the engine running @ 15:1 afr? Cruise or partial throttle around town?
If you still have coolant in the engine, and the coolant system is still together. Pressurize the coolant system to check the coolant seals condition. Usually if a coolant seal is bad the overflow will boil over. Are you running premix or stock omp? Can you take a picture of your spark plugs? If you need some " comfort " you can use the compression tester at the shop for free, just PM me...

 

That's what I figured.. I was on the dyno about 500 miles ago and everything looked good AFR's, no fuel pressure issues etc. Can't wait to install my wideband w/ gauge. Thanks for the info. G

 

I will PM you 1Revin7 be nice to meet another 7 owner in the valley...

here is a pic:

 

Appears to be just a lean burn, high egt soot. Which makes perfect sense since you said you were noticing lean afrs. Looks like the car needed more tuning/possibly bigger fuel system.

Is the car apart right now?

 

yep...totally apart.

Well the engine is still in the car, but the turbos, fuel system, all the solenoids and rats nest are out of the car. The cooling system is also apart, I am replacing the gaskets on the water pump and water pump housing. The UIM is getting powdercoated, I removed the double throttles and AWS on the UIM.

I think I want to modify my primary rail to accept the 850s and bore my stock 850s to 1300. I have everything ready to send to RC I just need to know what I am gonna do...

I dont know for sure what fuel pump is in the car but I think it is a Walboro from Rotary Performance...

Engine is a street port, with a T4 GT35R single turbo from A-spec (which should be on the way)...

I want to get it all together soon...but every part I order takes 3 weeks longer than it should to get to me, so my dates keep getting pushed back. Why can't someone quote you a date that things will be ready too far away...then beat it. Everyone always has to quote a date and then end up late....

 

Well just a suggestion but if you can't wait; I do single turbo kits at the shop

www.turblown.net

 

I already paid them...the order is sitting there waiting for the DP and manifold to come back from ceramic coating...it has been waiting for 2 weeks now. I just want to get the car running.

Can you machine my stock primary fuel rail the .125"? PM me...