So today I get my fifth car in with a missfire, needless to say I work on Toyota's and Lexus's for a living, these are the 2GR-FE 3.5L v6 Direct Injection Engines.

So here lies what happened, a Lexus GS350 comes in about 4 months ago with a ignition missfire, and we could not figure out why, infact it only happens when the valvetrain is completly warmed up. I call up Lexus Technical support because I hooked up T.I.S (Toyota information System = hink of it has HP Tuners but for made by and for Toyota)

All the values are within specification, this car has 80k miles on it.

So we take off the intake plenum, then manifold and we peak in at the valves, the back of the valves are competly dry infact brand new looking, so we put it back together, and Lemon lawed the car and gave them a new one.

2nd and 3rd time RX350 and IS350 come in all around 80k miles same exact thing, we cleaned the valves, made the sure fuel pump and pressure was perfect (these cars inject fuel at about 1.5k PSI) and everything is fine, spark plugs are atad bit fouled, but that comes with D.I. you cannot get rid of that because the fuel is practically sprayed on the ignition plug.

So we lemon lawed those cars and gave them new ones, well today a RX 350 comes in with 60k Miles, now i really really want to know what is going on with these cars, hell I checked EVERYTHING I even went to the extent of pulling off the heads. Well I found out the problem.

The problem is that the intake valves were sticking causing a missfire, so I ask myself.. "Why the hell are the vlaves sticking?"

Well after re-assembling the engine I was driving the car around to heat up the valvetrain to see if I could get it to missfire again, well it missfired thenit hit me!

(This part gets abit advanced so the average person might get lost)

Now with Direct injection no fuel is sprayed in the intake, so no fuel touches the seating area of the intake valves so there is no lubrication, where as with E.F.I the fuel sprays into he intake manifold then passes onto the intake valves lubricating the valve seat area.

So then that brought up another contimplation in my skull, why does the D.I. engines tend to blow out more smoke when the pedel is slammed to the floor, well its because of valve overlap and scavaging.

-TAKEN FROM WIKIPEDIA-
Scavenging is the process of pushing exhausted gas-charge out of the cylinder and drawing in a fresh draught of air ready for the next cycle in automotive usage. This process is essential in having a smooth-running internal combustion engine. Modifying the exhaust system, (i.e. modifying the exhaust gas velocity by changing exhaust tube diameters) can detract from the "ideal" scavenging effects, and reduce fuel efficiency and power.

What is not listed here is how during this phase (Stroke 1 )the fuel is sucked into the cyclinder from the intake manifold on a EFI engine, where as a DI engine its injected directly into the cyclinder and the fuel then gets sucked out before the exhaust valve fully closes, then burning up cold fuel in the catalytic converter (I have replaced many cats on DI engines around 50-60k)


So during lunch today I ran into technitians from Audi and my friend from Pontiac, We all sit down and chat and I bring up this topic, Well Audi has had DI engines for awhile and David (the Audi tech) listened to my story and agreed with me on all of this because infact they get the same problems around 60k miles, my Pontiac friend was awe struck as if a giant lightbulb appeared over his head brighter than the sun, because he had a Solstice he was working on with the same problem (missfire) that was at 80k Miles.

Now as I am aware all the DI engines use Bosch technology as of this point, as it being fixed in the future, couldnt tell you, but this is my thread on why Direct Injection sucks!

Reason for posting this is I want the people purchasing the SS/TC to atleast be aware of this problem, I contacted Bosch and they are aware of this problem, however there is no solution as of this moment, infact the only solution would be a complete ECU reprogram and new cam shafts to alter cyclinder scavaging time, but that costs to much money, and we know companies hate spending money.


SO a summary.

DI engines suck because they have no lubrication on the intake valve seats from the gasoline, and tend to missfire after about 80k+ Miles

DI engines suck because they waste fuel because of the scavaging process.


Anyways my friend from pontiac is going to call me tomorrow after he reseats the valves to see if it goes away. Il keep you all updated

 

DI engines also suck because it's harder to give modified engines more fuel

 

Ehh yeah thats true but its a PITA working on them, we had a fuel line recall on our 3.5L engines and one tech (the stupid one, every shop has them) pulled off the line while under pressure, shot fuel right into his hand, yeah that was scary ******* hilarious as ****.

 

Betcha that felt real good.

 

The medics had to cut his hand open to drain it because it was swelling up like crazy. We still give him **** all the time.

 

Ouch

I know from experience that cuts and gasoline don't get along

 

hes lucky that didnt kill him. DI engine fuel pressures are no joke. Im pretty sure in SI it has a bolded red heading that says make sure to bleed the pressure. hes lucky he isnt in a hospital.

 

Nice write up. Very interesting stuff.

 

Well that's definitely something to keep in mind when I start seeing Solstice GXPs come in the door.... Thanks

 

That was a pretty good read! Thanks for sharing! One of my best friends has a GXP solstice so I will be sure to pass this along to him.

 

Could there be a way to lubricate the intake valve seats, kind of like a fifth injector?

 

LOL

"Yeah, I have Pam Injection, Bitch."

 

it has been suggested to continually run the cold start injector, atleast the Lexus's have a cold start injector in the intake plenum, however it cuts off after the vehicle is warmed up.

the only problem with this is you would need a ECU calibration and MPG would go down. Plus some DI vehicles do not even have a cold start injector so installing one would require wires ran, a fuse, ECU calibration and a new intake plenum to mount the injector itself. Its not cost efficient.

 

So running a dry or wet nitrous kit could actually be beneficial to the engine but lubrication the seats then correct?

 

I dont get it - diesels have been DI for a great number of years - and they dont have this problem

 

diesels work on different principles than your standard gassoline engine

 

No **** - I used to tune diesels. The valvetrain works on the exact same principles - dry valves. My diesel had DI and dry valves - they never stuck and were always clean - even after 100K miles. So I say again - I dont get it.

 

Yeah... I've worked on a VW/Audi TDI a few times... with nearly 150k miles, the valves are perfectly clean and dry... and still work absolutely flawlessly.

 

i wouldnt know much about that

diesle motors are made with more clearence and what diesle do you know that runs up to 6-7k redline, they do not have to advance timing as much.

but good question though.

 

I guess in general that is true - the only reason a diesel cannot rev very high is due to the long stroke and high compression. diesels can have very advanced injection timings in some conditions - they do have mild cam specs though.

 

V12 TDI LMS...

 

Good read. Thanx for sharing

 

LOL that is a precision machine though

 

ya them poor mazdaspeed3 arent making any power

 

The high compression stroke of the diesel is going to push diesel oil fumes against the valve seats from the inside and the combustion temperatures are much lower most of the time. The old GMC 8V71T two stroke diesel with unit injectors, a Roots Blower and two turbos I used to work on certainly didn't have the dry valve problem.

Good info on DI and potential problems with the LNF. The High Pressure fuel system is really a hazard for the do it your selfer...