Glowing Exhaust!

[kfitzpat9]

Hi,

I just rebuilt and installed my 1994 3.6 turbo engine and it is running! But after just a couple minutes, the B&B exhaust (new) starts to glow orange! Other than the exhaust, the engine is completely stock.

So, I suspect it is running rich as the timing is not adjustable, so just trying to figure out why!

Any help would be appreciated and some pictures below.

[HawgRyder]

With a turbo...heat is power.
Directing it through the turbo is the important thing.
Perhaps wrapping the pipes in special pipe wrap will help keep the heat inside the tubes.
And...if you look carefully at night...you might even see "through" the pipes and observe the exhaust flow (looks like a ghost image)....very interesting and entertaining.
Bob

[Steve@Rennsport]

Late ignition timing and/or AFR issues are usually the culprits here.

You need to check the timing at idle and at 5K as well as measure your AFR's to find out what is going on.

[Winter]

I always thought that heat was the enemy of turbos, which is why turbocharged cars come with intercoolers, to cool the air charge. Add a bigger intercooler, and doesn't that help with fade, running temps, etc.?

Heat cokes oil in oil cooled turbos, right? Run an oil cooled turbo hard (like I sometimes do with my S6 avant), and you want to let it cool down before shutoff.

No insights into the OP's issue, but I'd probably go with what Steve suggests. . . . .I think he probably knows what he's talking about.

My questions are only to challenge my own assumptions. If I'm wrong, please let me know.

Good luck, that's a MEAN engine. I hope you get it sorted soon.

[nick_911]

I would definately go with timing on this one and it must be running very lean.

Heat is definately a power killer on a turbo motor. I have no experience with a 911 turbo but coming from a 550hp Nissan 200sx and a 500hp Nissan GTR the only way to make bigger power and eliminate detonation is to try and keep intake temps as low as possible.
Anyone running a turbo will definately tell you that their car will feel much more powerful in cooler weather compared to a hot day.

[RarlyL8]

Timing or fuel. Check your timing first and then fuel. Unbalanced cylinders can cause this as well as a lean mixture. If your timing and AFR's are good then measure the temp of each primary with a pyrometer; this will show which injectors are pumping less fuel at idle.

[Targalid]

My local turbo expert says Winter is right. You need to cool the intake more than you already are. He says run the air up to the front, intercool it and then bring it back to the engine. For each 3 feet of 3 inch pipe you lose about 1 psi, for which you can compensate with more boost. The alternative is to cook your motor. Also he says to cool the oil to your turbo unit or risk burning the bearings in the turbo.

[Flieger]

No need to run the air up to the front of the car. Rear fender vents are good enough. Or the traditional one mounted above the fan.

[RarlyL8]

All of this has nothing to do with his glowing header issue. Glowing headers at idle indicate a problem. That problem is generally bad AFR's or bad timing. Since the engine was just rebuilt I'd check the timing first.

[911pcars]

Originally Posted by RarlyL8

All of this has nothing to do with his glowing header issue. Glowing headers at idle indicate a problem. That problem is generally bad AFR's or bad timing. Since the engine was just rebuilt I'd check the timing first.

..... constantly dribbling injectors, restriction in exh. system?

Yep. Boost and resultant exh. heat isn't normal at idle/no load.

Sherwood

[kfitzpat9]

Thanks all and I will check the timing this evening and go from there. Although, my understanding is that the timing is not adjustable, but still an easy thing to check.

[RarlyL8]

By check the timing I mean verify TDC#1 matching the crank sensor or rotor and the pulley markings. I don't know much about the EZ69 but that is where I would start.

[kfitzpat9]

I checked the timing and it looks dead on as it should since it's controlled electronically. However, and per Porsche factory manual, it is idling high (1100-1150 rpm) as it should be at 950 (+50) rpm which tells me air might be getting in somewhere where it shouldn't.

Therefore, I sprayed brake clean around I/C to throttle body and other areas to see if there were any changes in idle, but nothing obvious thus far.

Next step is to test the AFR which I don't have the equipment for, but I do know someone that does!

Stay tuned and appreciate the help!

[kfitzpat9]

So the timing was dead on and the AFR has been adjusted and the exhaust profile is exactly where it is supposed to be (pre-cat) 1 bar.

However, the B&B exhaust still glows at around 800 degrees F which just doesn't seem like it should. The temps at the each of the exhaust ports is 450-500 but where the two come together before the muffler, it's around 800 degrees.

The Porsche shop is testing it at 2300 rpm so that may be causing the excess heat, but when testing another Porsche 911 turbo with Stock exhaust, the temperatures were nearly identical!

Thoughts?

[gshase]

I do not think the exhaust should glow till 1600-1700F. If is glowing at lower power it is too lean.

[911pcars]

Originally Posted by gshase

I do not think the exhaust should glow till 1600-1700F. If is glowing at lower power it is too lean.

The color of heated metal is temperature-dependent whether the mixture is rich or lean. If the heated metal is a specific color, it's related to a specific operating temperature range:





Sherwood

[ant7]

hi,
could be that the exhaust/turbo housing is restricing the exhaust flow, or, motor running very lean.
Hope this helps.
Anthony.

[ant7]

Also,
what compresion ratio pistons are you using, and fuel octane ?
Anthony.

[kfitzpat9]

The car in not running lean, or rich according the AFR test results. It was somewhat rich when I brought it into Porsche dealer, but it was still within the range where the O2 sensor and system would adjust to an acceptable mixture.

Timing is dead on as EZ69 is operating as it should.

Engine is completely stock other than B&B exhaust.

[lupin..the..3rd]

Originally Posted by Winter

I always thought that heat was the enemy of turbos, which is why turbocharged cars come with intercoolers, to cool the air charge. Add a bigger intercooler, and doesn't that help with fade, running temps, etc.?

Heat cokes oil in oil cooled turbos, right? Run an oil cooled turbo hard (like I sometimes do with my S6 avant), and you want to let it cool down before shutoff.

No, heat is not the enemy of a turbo. In fact, heat is what makes the turbocharger function at all. Without heat, it wouldn't even work.

There are three things flowing through a turbocharger. You're looking at the wrong two. Heat in the oil, yes, you want to reduce that by using an oil cooler. Heat in the intake air, yes, you want to reduce that by using an intercooler.

But heat in the exhaust gasses is a different story. Exhaust heat = power. A turbocharger would not work at all if the exhaust gasses were at ambient temperature. The entire reason that a turbocharger does what it does, is because of the heat. Turbos are powered by heat.

That said, I've only ever seen turbo exhaust pipes glow at WOT, never at idle.