I partly melted the exaust side of the turbo housing. (It's been replaced now) How can I tell if the cause of the heat was from turbo overspin, (18 psi at 6000 rpms) or too lean of a fuel mixture. My air/fuel ratio gauge has been showing STOICH - RICH under full boost, but LEAN under normal driving. Are the symptoms the same?

 

How is the car running? does it ever feel like its miss-firing? or does it stumble before taking off at WOT?

Do you have upgraded exhaust? How bout an EGT... what does it read if you have one? Have you data logged the car?

What mods do you have exactly?

I've seen problems with ignition (coil pack, wires etc) cause some odd reading. a poor spark in one cylinder could produce the rich and then the lean would be coming from the added boost in another cylinder while the timing is not advancing properly. (something to that effect, not sure how to put it into words)

 

Never feels like it's miss-firing. Car feels very lazy before 3000 rpms (below 3000 rpms feels much slower then when it was stock. I used to get full boost, 7psi, at 2500 rpms) at which point boost really comes on strong and the computer realizes it needs to dump all the fuel it can into the engine. When this happens the power hits hard and fast.

List of mods relevant to the engine:
Engine balancing
Port/polish
Upgraded intake/exhaust
Upgraded to larger compressor turbine in the turbo with new bearings. Turbo housing is stock.
Boost controller
Stock ECU (have an Apexi Super AFC on order)

Complete list of mods are here:
https://www.evolutionm.net/registry/...ehicleid=10&s=

 

If anything, maybe a faulty reading from the A/F gauge. With the AFC, you'll probably be more able to find out for sure. Isn't this the second time you've had to get your turbo rebuilt? Or was it the manifold last time? Maybe check that to as well...ya never know.

 

Turbo doesn't burn from over-spinning. Your bearings could get cooked a as a result of that one, turbo will not be able to spool that fast any more and it would probably make some noise.

What it looks like here is that your high exhaust temps melted that part of the housing. That could be because you where running too lean or too rich. From what you where describing, it looks to me that you where running very rich (part of the slow response until the turbo kicks in for real).

Too much of unburned fuel will create the secondary explosion in your exhaust manifold which will create the extra heat which can burn your housing and the turbine.

I would suggest more data-logging about your EGTs, and O2 readings. Check your fuel consumption too. Injectors could get stuck or something and spray way more fuel that what they where told in the first place. Fuel pressure is also good one to know about where it is. Too high one would add more fuel in the combustion chamber than what would ECU think it does.

Good luck!


Mr. AWD

 

It was the manifold and turbo, and no, this is still about the first time. I still don't really have a satisfactory answer as to what happened. I don't really want to repeat as it was way too expensive.

 

Thanks MrAWD for your reply. You gave me a couple of suggestions I haven't thought of checking yet.

 

Sorry, one more question. How do you know if your pushing a turbo too much and going into over-spin? Obviously this would cause premature bearing failure. I did have the symptoms you described above.

 

Well, the only way to know that is a boost drop that you would have at the higher RPMs that is not caused by the boost leak

There is really no other way to measure that part before it is too late. The other one is during the turbo rebuild session where you (turbo repair guy) can see what happened with the bearings and whether they where tortured too much.

Good luck!

Mr. AWD

 

So the only fix for that then is to run a larger turbo. Oh darn.

 

A lot of A/F gauges are nothing more than blinking lights... most cant give you an acurate enough reading to really do anything for you. I believe theres also a problem with the fact that most hook up to the stock o2 sensor (correct?) this in itself can give your a/f reading problems because the O2 sensor voltage decreases with increased heat, so after the car has been running for a while or has been raced etc the a/f reading (voltage) will obviously drop while your engnes a/f ratio will actually stay the same. There is some good gauges of course, i'm not trying to say his is a poor gauge, i believe greddy has a new style out that replaces the stock o2 and gives good readings on normal gauge face, which would seem ideal to me and for all i know he has this gauge .

You pretty much have to have a EGT to tune a car (well, tune it to the best of you abbility without going to a shop and having them tune it)... The EGT which is usually tapped in the #1 runner for a 4g63 is usally the warmest, because it is the leanest (which in itself is a problem w/ fuel rail), and when you start doing upgrades that need tuning you'll have to get an AFC or ecu upgrade. the bad part is, the #1 runner can be (and usually will be) to lean, while the cylinder closest to the inlet for the fuel rail will be rich... with the two middle cylinders closer to correct.

evo_dan... did you have a problem with leaving a "smoke screen" when you left a traffic light etc? should be the first sign that theres a problem with tuning or ignition (or o2 sensors sometimes)

 

I'm using a digital Autometer gauge. You know, the one with all the frigin blinking lights like Knight Rider. Don't know how accurate it is.

"Smoke screen"? Nope, no smoke screen. My boost slowly became less and less untill I could only get 2 psi max. Of course by this time the car was in the shop. In the shop all they told me was there were signs of extreme heat around the turbo housing. They said I was probably running too lean, but it seemed like they were guessing.

Looks like I'll just have to bite the bullet this summer and take the car in and have it tuned and upgraded properly. Doesn't look like Canada will be getting Evos any time soon.

 

You could probably tune it yourself once you get an AFC & EGT, in any case if you did want to go to a shop, Lowell is probably the closest and best person around... He's great with tranny rebuilds as well. i'm not sure he has as much experience with your car though.

www.lr-racing.com
Port Coquitlam, BC

 

Hey, thanks. I'll check it out.