Glowing exhaust manifold

[RadioFlyer]

Pulled off the interstate in the '80 900t last night when engine tone deepened. The exhaust manifold was glowing red hot right around the middle of the manifold. Cat was normal as was everything else. Any tips? I'm thinking either timing or a blockage.

[SwedeSport]

You must have been beating the shit out of it.

I have had mine glowing many times, but it's usually when I am really beating on the car.

[RadioFlyer]

Ha. I wish. I baby that car. Barely touch the turbo, but cruise at about 75 on the interstate if that counts as beating it. But even creeping it home with no boost, driving the speed limit and stopping twice to let it cool, it was still glowing when I rolled into the driveway.

[Jordan]

retarded timing or running very rich can do that and make the exhaust note deeper.

[RadioFlyer]

Is the timing procedure different for the B-engine than the 16v? Just wondering if I timed it correctly in the first place. Also, is there a way to check the timing advance? Maybe my vacuum diaphragm is busted?

[Jordan]

Never done a B-turbo, but have done a B motor. Timing procedure is usually the same, but the specs are different, distributor advance unplugged and vac line capped. Specs are usually @ some RPM value, so make sure you match those up with what you are looking at.

[RadioFlyer]

Ok, I'll check the shop manuals - full set came with the car. Man are they handy.

[Geoff]

Its probably on the sticker on the inner fender too.

[DrewP]

You can check the advance and retard with a handheld vacuum/pressure pump (like a MitiVac, handy for lots of things.)

If you don't have that, you can check the vacuum advance by sucking on the vacuum reference line and plugging the end of it with the tip of your tongue (handy for checking BPV's and the check valve in the 16V C900's vacuum reservoir that sits in the passenger side inner fender) and check the pressure with a bike pump while holding the hose up to the pump fitting.

Do the B20 turbo engines have any centrifugal advance? I've only had D-Jet 99's and the N/A B20 900 EMS, and I'm away from where I can check the service manual, but it should be in there too.

[RadioFlyer]

Tried timing it last night - set timing to 20 degrees at 2000 rpm according to the shop manual. Sounds better, slightly lower boost, but exhaust still glows after light interstate driving on a cold night. Not as bright a glow, so it's slightly better, but still glowing. I'll try checking the vac advance next.

[DrewP]

If you suspect the exhaust is clogged that badly, you can also either unscrew the O2 sensor or loosen the downpipe flange to let the exhaust leak around the flange on purpose and see if that has any effect after a short 5 minute or so drive. Was thinking back lately how I ID'd clogged cats.

If you get under the car and bang on the muffler and the cat and hear lots of rattly loose bits inside then they may well be plugged up.

[RadioFlyer]

Good call. I'll give that a try. I doubt it's a clogged exhaust - performance is great. My wife's 9k aero had a clogged exhaust last year and it lost all boost. It's worth a try though.

[DrewP]

Yeah, if it's clogged really badly it'll make low boost and usually misfire.

[Crazyswede]

Light red glowing seemed to be the norm for all of my 16v turbos after running down the interstate for a while even at normal speeds and engine revs. Long ago when I tried running EZK and APC together I did a test run on a local road one night. The car built a ton of boost but didnt seem to do anything with it. When I opened the hood...in the dark...the exhaust manifold was glowing yellow as was the turbo and part of the down pipe. I think the EZK was retarding timing further and further and the turbo was boosting more and more as there was no knock...made 0 power though and I sonn gave up on making those work together.

[RadioFlyer]

I actually brought it up on Saabnet last night for the heck of it and a guy said something similar:

"The first time you see it seems shocking , but that is how hot they run! I remember popping the hood of my 1979 900 turbo and thinking the thing will melt! Most big diesel trucks have a "pyrometer" which measures the exhaust manifold temperature. That high temp is the reason many people leave the engine running awhile after a long pull to cool down. I always marvel at how the gaskets/diaphrams/o-rings survive the temp."

I don't know if I would agree that that's how they normally run, but maybe it's just that it seems more shocking when viewing it in the dark? I'm still concerned that it happens during pretty normal interstate speeds and even non-interstate speeds. Would an intercooler help at all?