blakep82
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| posted on 26/9/11 at 12:04 PM |
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exhaust heating up very quick
... i think
had the truck running a bit better last week, but only sort of 30 secs at a time 2 or 3 times, and the exhaust seems to heat up very quickly. i had a
bit of colvoluted plastic tube resting against it as i didn't think it would be a problem and thats melted, and the cleaner i put on the exhaust
ages ago smoking quite a lot.
seems a bit quick to get that hot.
flange plate distorted a bit with welding so it doesn't sit flat against the head just now (will get it ground flat soon) and a pin hole in the
welding. could it be air getting in causing it?
carbs are straight off a zx9r with no mods so far, running too lean? (or too rich?)
any ideas? not really sure how hot it should get and how quick, but it didn't seem right really. I've got no way to measure the
temperature, or exhaust gases
[Edited on 26/9/11 by blakep82]
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adithorp
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| posted on 26/9/11 at 12:30 PM |
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Ermm... could it be the superheated gas coming from the explosions going on inside the engine?  
Seriously... tubular manifolds will heat up very quick compared to cast ones, as there's a lot less metal to heat. Running weak or badly timed
can/will cause exhaust temps to be higher but probably not noticably after just that time.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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britishtrident
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| posted on 26/9/11 at 12:35 PM |
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Hot exhaust gas temp usually points to retarded ignition timing, because there is a shorter burning time available the, combustion is still
continuing in the exhaust gasses after the exhaust valve opens. Not unusual to see exhaust manifold glowing bright cheryy red at fast idle if the
ignition is retarded.
Weak mixture can also cause it because weak mixtures burn slower (and hence weak mixtures need more ignition advance) but think you would notice
more missing and sputtering and popping back.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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blakep82
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| posted on 26/9/11 at 12:36 PM |
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quote:
Originally posted by adithorp
Ermm... could it be the superheated gas coming from the explosions going on inside the engine?
Seriously... tubular manifolds will heat up very quick compared to cast ones, as there's a lot less metal to heat. Running weak or badly timed
can/will cause exhaust temps to be higher but probably not noticably after just that time.
well, of course the gas is hot
hadn't really thought about cast manifold having more metal in them, but i guess that makes sense! though i had a tubular manifold on my BMW
(still have, but its not working now...) and didn't remember it getting so hot so quick, but i guess i'm just in a panic that i'm
going to end up melting my engine!
also it is just running at 10 degrees fixed advance, which i think isn't in the proper range for this engine (13-32 degrees is what i've
got a map for) so i guess its a bit retarded (doesn't sound right lol) but i was just a bit surprised it was that hot after just 30 seconds
how can i tell if the mixture is set right? not got any money for buying tools,but any simple pointers?
[Edited on 26/9/11 by blakep82]
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adithorp
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| posted on 26/9/11 at 01:01 PM |
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Without any tools then the only thing you can do is have a look at spark plug colour. center electrode should be biscuit colour, white would indicate
weak and darker, rich althugh after just a few min's running it'd be hard to tell. Beyond that you're looking at
"colour-tune" or ideally a CO meter.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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blakep82
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| posted on 26/9/11 at 01:17 PM |
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ah cool, it'll be quite happy running for longer then? scared of burnt valves etc. want to run it for a decent length of time. 5 minutes or so
(don't have a radiator fan yet) but i don't really do engines. any engine part needing repair, i get someone else to do it! thats why
i'm a bit worried about it not running right!
________________________
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tomgregory2000
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| posted on 26/9/11 at 01:26 PM |
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iirc: the bmw tubular manifolds are double wall ie a pipe within another pipe so each has its own heat shild the full length
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Dingz
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| posted on 26/9/11 at 04:06 PM |
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Just a thought 32° advance seems very high to me for a 16 valve engine or is it an 8 Valve?
Phoned the local ramblers club today, but the bloke who answered just
went on and on.
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blakep82
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| posted on 26/9/11 at 05:04 PM |
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quote:
Originally posted by Dingz
Just a thought 32° advance seems very high to me for a 16 valve engine or is it an 8 Valve?
hmm, it might be. i'm just taking that off a map i downloaded from the megajolt forum/website thing.
 
Description
its a 16v engine, think that map is for a red top, mines an ecotec, so should give a good starting point i'd have thought?
not got the megajolt connected up yet though, til i can get the wiring loom done and get it all put together properly
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don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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cs3tcr
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| posted on 27/9/11 at 03:13 PM |
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From what i've read, 32 sounds about right for a 4 valve head (pent roof construction). 8 valve heads vary due to different combustion chamber
designs (wedge, hemi, bowl in piston etc).
As for the manifold heating up quickly, i had the same issue with my latest car and it was down to retarded ignition. It sure baked the manifold
paint on.
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