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EGT Probe question
by
BellCityDubber
on 14 Nov, 2006 13:55
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So I've decided to get an EGT gauge and probe kit...
Now my quesiton is this:
I know that alot of people recommend pre turbo and a few like post turbo due to turbine saftey concerns. Although it will potentially save my turbo, and I'd have to add ~200* to my EGT reading.... where on my 1.6TD's downpipe should I place the bung?
Anyone have any suggestions or pictures they could share?
thank you
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#1
by
saurkraut
on 14 Nov, 2006 14:15
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Pre turbine isn't that hard. Ive done a couple. Unbolt your exhaust manifold. Take your probe adaptor to your local hadware store and get the appropriate tap and a couple of cobalt bits to drill the hole. Drill and tap in the center of the manifold below the turbo flange. I have one manifold that I did this to about 5 years ago. Many hard miles with no problems. Even saved my engine once when I hit a bird at speed. Grill/bird parts some how got into the timing cover, under the belt and had the pump retard one tooth. Holy high EGT bat man..
Post turbine EGT is a guess at best.
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#2
by
745 turbogreasel
on 14 Nov, 2006 15:31
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Post turbine also respomds much more slowly.
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#3
by
BellCityDubber
on 14 Nov, 2006 19:24
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That's a nice suggestion and all, but unbolting the exhaust manifold is more work than I'm really willing to do at the moment, seeing as the car probally hasn't been apart since nineteen ninety-never, I dont want to break a stud and render my daily driver undriveable until I have the money and time to fix it. (I've had it happen on my old audi)
From what I've been told by a vw/audi tech who's in my car club, there are quite a few audi's that have their egt gauge post turbine. which is fine enough for me. which will also give me the added benefit of not damaging my turbine in the event of the probe breaking inside the exhaust system
IMHO, it's difficult to find some of the 1.6TD parts [around my area] so instead of having someone fab up a manifold in the event of a screw up (not saying he does bad work, but I just want to be certain) I'd rather mess up the downpipe, then in that case I can order one from passenger performance.
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#4
by
BellCityDubber
on 14 Nov, 2006 19:32
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Saurkraut mentioned about drilling and tapping...
although I'm not the one doing that portion of the install, would drilling a hole and welding in something like an O2 bung be sufficient?
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#5
by
Slave2School
on 14 Nov, 2006 19:43
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I'm using a band clamp style one and that's been sufficient for a couple thousand km's so far (and a dab of JBweld) so I'm sure a bung will be 100% fine for the next 200 years.
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#6
by
anarchyx34
on 14 Nov, 2006 21:47
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Grill/bird parts some how got into the timing cover, under the belt and had the pump retard one tooth. Holy high EGT bat man..
:shock: WTF?? That had to make quite a mess...
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#7
by
BellCityDubber
on 14 Nov, 2006 22:33
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I'm using a band camp style one ...
What? Band Camp?
jk
Ok ok
On a serious note...
I tried searching because I remember a post with a picture of someone mounting an egt probe in the bottom of the manifold in one of the bracket support bolt holes.... does anyone recall this post by chance?
I tried searching and couldn't find it
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#8
by
saurkraut
on 15 Nov, 2006 06:54
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I faintly racall, somewhere, that some one drilled their exhaust manifold on the vehicle with the engine running to blow the chips out while drilling.
I wouldn't fret the exhaust studs. Typically, if the nut won't thread off the stud, the stud will will thread out of the head just fine. Get a bag full of new studs and nuts and go at it.
With the way these manifolds warp, everything is probably loose already.
Fear not the drilling and tapping as well. The cobalt bits go through the manifold like a hot knife through butter. The tapping is a breeze too. Just did one last weekend.
I use the VDO stuff, so if you want to know the drill and tap sizes, i got all the stuff in my car and i'll go out and get the sizes for you.
If you want a nice little gauge that shows a temperature, go post turbo.
If you want to measure EGT for engine mods, put it in the manifold.
Going through the bracket hole looks good in the pictures, but it looks kind of scary when you have the manifold in you hands. puts the hole mighty close to the turbo mounting flange surface. I'm fearless, but it scared me.
Take your best guess were the center on the bolt pattern is on the bottom and drill away.
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#9
by
HarryMann
on 15 Nov, 2006 15:33
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With the way these manifolds warp, everything is probably loose already.
That's true, Nos 1 and 4 on mine were 0.040" ish above the centre two... No.4 bolts loose and blowing. Took a few hours with 80# to get it all level again.
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#10
by
larry104
on 15 Nov, 2006 16:54
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So I've decided to get an EGT gauge and probe kit...
Now my quesiton is this:
I know that alot of people recommend pre turbo and a few like post turbo due to turbine saftey concerns. Although it will potentially save my turbo, and I'd have to add ~200* to my EGT reading.... where on my 1.6TD's downpipe should I place the bung?
Anyone have any suggestions or pictures they could share?
thank you
I've yet to hear/read a convincing argument for not installing an EGT post turbine. My TC mounts in a bung in the downpipe as close as possible to the exhaust flange, with the probe tip centered in the pipe.
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#11
by
Slave2School
on 15 Nov, 2006 19:43
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[/quote]
I've yet to hear/read a convincing argument for not installing an EGT post turbine.[/quote]
Here's one: post turbine you have absolutely no idea what temperature the turbine is actually seeing or what is coming out of the engine (which also has an EGT limit based on the composition of the exhaust valves correct?). The energy absorbed by the turbine is not a constant so there is no easy "add 200F" formula.
Use a thermal couple that is rated to well beyond your max allowable EGT and drive worry free, or don't use a gauge at all and drive worry free since you are already doing so by having it in the downpipe
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#12
by
larry104
on 15 Nov, 2006 20:13
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I've yet to hear/read a convincing argument for not installing an EGT post turbine.[/quote]
Here's one: post turbine you have absolutely no idea what temperature the turbine is actually seeing or what is coming out of the engine (which also has an EGT limit based on the composition of the exhaust valves correct?). The energy absorbed by the turbine is not a constant so there is no easy "add 200F" formula.
[/quote]
Have you actually measured exhaust gas temperature pre and post turbine?
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#13
by
jackbombay
on 15 Nov, 2006 20:26
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At low boost levels there is little difference in pre and post turbine temps, at high boost levels there is a big difference, the one place you want/need it to be accurate is the place that it's least accurate.
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#14
by
Slave2School
on 15 Nov, 2006 20:30
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No I personally have not. However just because I haven't doesn't mean that I don't have reasons based on facts such as the turbine sucks vast amounts of energy (heat) out of the exhaust flow to believe that the readings are virtually useless post turbine.
The only application I know of where a EGT probe(s) are used post turbine are jet engines which run in a vary narrow power band and have all the variables already calculated by the manufacture of the engine. The temperature limits are therefore useful since the engine max temps are meant to be measured post turbine.
In our case the turbos all have INLET limits so unless you mount a probe pre in addition to post, map out the difference between the two under all conditions (for each set up you run) and run a calculation in your head based on the difference...the post results will be totally useless for being used a gauge of turbo health.
To each there own but other than the slight chance of breaking off my 1" long probe (rated to 2100F) there is no reason not to have it pre turbine and actually read the proper temperature.