Hello! Log in or Register   |  Help  |  Donate  |  Buy Shirts See all banner ads | Advertise on TheSamba.com  
TheSamba.com
 
Exhaust temps
Page: Previous  1, 2
Forum Index -> Performance/Engines/Transmissions Share: Facebook Twitter
Reply to topic
Print View
Quick sort: Show newest posts on top | Show oldest posts on top View previous topic :: View next topic  
Author Message
[email protected]
Samba Member


Joined: August 15, 2002
Posts: 4394
Location: Brew City
roy@mofoco.com is offline 

PostPosted: Wed Nov 07, 2018 1:05 pm    Post subject: Re: Exhaust temps Reply with quote

Bob Brugge wrote:
I bought an infrared heat gun today with the intention of using it to try to tune my set up a little better. I know the right way to do it is with an A/F meter, but I don't have one, nor do I have access to one. I do have access to an entire parts house of stuff, if I can figure out what I need and how to use it. I wondered if anyone had tuned their motor so all 4 are running at an optimal temp, and what that temp might be? I have a 1641 dp with twin Webber 34 ict knock offs. I live at 3300 ft elevation. I figure I want the exhaust to run as cool as I can get it and the way to get it cool is to richen it up. I don’t know what would happen if I ran it too rich, would my temps continue to go down, or would they start to go back up?
Any advice or empirical evidence?


You are going about this the wrong way. Exhaust temps are subjective, just like head temps. It depends on where you measure and also what components you are using. Exhaust temps will vary from 1100-1400 degrees depending on where you take the reading and what rpm you are at. Trying to use a infrared gun and use that to tune the engine will not work unless you have a huge amount of experience. I use an infrared heat gun when tuning but the only function is to make sure the engine is firing on all four cylinders.

BTW, set your timing to 27 degrees total advance if you have any worry of overheating, not 30.
_________________
Please "LIKE" us on facebook to see what we are working on.

https://www.facebook.com/mofoco?ref=ts&fref=ts

www.mofoco.com

Cylinder Head Reference Sheet
Back to top
View user's profile Send private message Send e-mail Visit poster's website Gallery Classifieds Feedback
Clatter
Samba Member


Joined: September 24, 2003
Posts: 7527
Location: Santa Cruz
Clatter is offline 

PostPosted: Thu Nov 08, 2018 9:12 pm    Post subject: Re: Exhaust temps Reply with quote

FWIW,

The wideband thread has a bunch of confused people babbling,
Groping,
Trying to understand...

Read what John Connelly says,
And maybe what a few smart people say,
But don’t let all the babble confuse you.

If you read what confused people say,
You’re only going to get confused..
_________________
Bus Motor Build

What’s That Noise?!?
Back to top
View user's profile Send private message Gallery Classifieds Feedback
oprn
Samba Member


Joined: November 13, 2016
Posts: 12632
Location: Western Canada
oprn is offline 

PostPosted: Fri Nov 09, 2018 6:07 am    Post subject: Re: Exhaust temps Reply with quote

There is a bit of that on this thread too Clatter! A lot of talk about main jet mixtures, I'd like to see someone hanging upside down off his back bumper at 70 mph, heat gun in hand getting exhaust temperatures... Shocked

A heat gun is useful to a limited degree at idle or in the early stages of transition only, and just sitting in your driveway! Any talk of temps at engine conditions beyond that in this heat gun thread is pure speculation. (Speculation being a nice was to say B.S.!)
Back to top
View user's profile Send private message Gallery Classifieds Feedback
ralf
Samba Member


Joined: July 08, 2008
Posts: 1215
Location: r4
ralf is offline 

PostPosted: Fri Nov 09, 2018 8:29 am    Post subject: Re: Exhaust temps Reply with quote

oprn wrote:
There is a bit of that on this thread too Clatter! A lot of talk about main jet mixtures, I'd like to see someone hanging upside down off his back bumper at 70 mph, heat gun in hand getting exhaust temperatures... Shocked

A heat gun is useful to a limited degree at idle or in the early stages of transition only, and just sitting in your driveway! Any talk of temps at engine conditions beyond that in this heat gun thread is pure speculation. (Speculation being a nice was to say B.S.!)


ambient temps.. when colder.. then ur "aircooled" system will be blowing colder ir = changing IR temp reading aft the exhaust LOL
_________________
Flow Through a Curved Conduit

porting my SP head for my brother's project
https://youtu.be/OS_mVjQuqgk
Back to top
View user's profile Send private message Instagram Gallery Classifieds Feedback
Bob Brugge
Samba Member


Joined: April 09, 2015
Posts: 721
Location: Missoula, MT
Bob Brugge is offline 

PostPosted: Sun Nov 11, 2018 9:26 pm    Post subject: Re: Exhaust temps Reply with quote

ralf wrote:
let me join in on the fun (mainly because exhaust and egt is my current interest)

Bob Brugge... i absolutely mean no offense at all andhope we can help you improve your craft/hobby amongst the more seasoned experts here..

but to say "i basically know" this or that.. or whatever.. indirectly concludes to not open to learning.. regardless (ok im not a psychic haha but guys know what i mean)

with that out of the way...

i too have read the wideband thread actually i read it to pick up certain pointers from peeps like john connolly as he sometimes has great insights (well always does) but to read that u checked it and on the 3rd page u are more confused and done with it... shows exactly what ive mentioned earlier... about "learning"

ofcourse i wont blame u as alot of "experts" spew stuff without actual experience.. it is based on what they read etc... or give u answers directly as a "guess what" or "then you will know" LOL but anyways...

a few tidbits from my experience...

EGT- can be directly impacted by airfuel... or load amongst other things... and im surprised no one has mentioned... the higher timing you run = the lower egt you get.. and the lower timing u run = higher egt... so that doesnt really tell u or me if "its in tune" or not...

that doesnt include the chances of fat jets or too small jets yet...

oh wait we havnt gotten to "load" yet ... driving on flat.. incline or downhill matters....

all that is because.. i tune EFI (on computer ofcourse lol) and so i have took the time to learn.. and sometimes (most of the time) ive learned things at times i didnt expect it...

Wideband- this it is as confusing... new plugs will change ur reading.. a slight exhaust leak (from a flange gasket or mini crack) will suck in air and show "lean" and u can tune it to the correct a/f and it will be off because.. hey there was a leak? so basing it off solely on the wideband will be unsafe too...

short story * there was a tuner local to me who tuned a car and he corrected the tune to be safe for daily driving... owner was getting 18mpg LOL so he came to me and first thing on my first test drive with wideband.. is i realized one thing... while the a/f was correct? the values showed way too much fuel like as if it was 3,000cc (its a 1500cc btw) and upon check up.. bam! exhaust leak under the oilpan... so yyes the tuner did tune it correctly... "but correctly by the wideband" tuner wasnt an engine builder so.. his notions are strictly off the wideband reading...

i say this is because.. like all tools? it is helpful if u have an idea of whats around u... in this case.. how the engine runs and how its suppose to run...

ive been tuning imports for a decade now... to this day i still learn new things.. and today i have 2 sets of PLX dm6 wideband... 2 sets of Innovate lc2 wideband.. and an Innovate lm2 wideband... im not rich... but everytime i earn thru tuning i get widebands as spare.. because having 1 and relying on just one? can show me something that is erroneous or not right... so having comparitives eliminates blindness...

now what ive all said... doesnt help you one bit Sad im sorry... but it will help you move along to a better direction with your tools and future tools to purchase...

sidenote : if u melted stuff or due to a broken head etc.. ur bearings might be too lose.. not worn but loose.. and loose clearances = kills oil pressure.. and idiot light functions as pressure light and or temperature light in a nutshell.. so have acheck on that so you can enjoy driving it more than repairing it...

oh and too much timing = accelerates rod bearing wear.. which affects oil pressure too...

sidenote x2 : with all the 5 widebands i own.. believe it or not i have not yet run it on my dad's bug or my brothers bug... mainly because if evertyhing is sound and correct? (my brothers bug) will not need a 140 main jet on his 30pict carb cuz he is a 1500 ... no wideband can show me lean and convince me it needs "bigger " jet LOL see what i mean?

sidenote x3 : as previously posted by udidwht, the diagrame is decent..
and u can see shooting for peak egt.. power is slighty after peak egt? but that egt reading also do exist wayy wayy befor peak power = slightly bfor peak EGT... so relying on xhaust temp alone.. is rather more dangerous just like relying on wideband alone... in general.. egt + wideband + engine knowledge + dyno... will be best... but hey we dont all have that or access to it...

ps. this is the longest post i have ever made in the samba time ive had...
apologies if it seems to insult you or make you feel bad... i just hope it is of help in letting you view things wider and better in the future


I am honored at the effort you put forth to help me try to understand. You don't make me feel bad, you don't come across as condescending, which usually pisses me off. Mostly I am trying to get a perfectish tune on an imperfect piece of equipment with less than stellar tools.

I understand how a motor works and how to replace shit, theory, not so much... which really screws me here. I am, or was, hoping with my trusty timing light and some other basic shit I could get somewhat of a better tune than a timing light alone. Seems like while that is possible, I need different tools and probably a more mechanically sound engine.

Mostly it runs like shit. I had everything the way I wanted it before I blow torched the head and now the whole thing seems like a p.o.s. Granted, before I melted the head, I knew it needed someone way more experienced than I at tuning to get it "right". The "expert" I took it to had it so far advanced I hated the way it ran.

I am hoping with some hard core tuning I can get this new pos configuration to run a little better. Seriously thinking about a 1776 from the guts out. True, I don't have the expertise to make what I have run right currently, but it is so far from what I had before I melted the head I don't know what to do with it other than start over. I probably should pull the new valves and springs from the melted head and put them on the replacement head. Not sure how a 3 angle valve will work with a regular valve seat. Not sure how to R&R my brand new valve guides or if it is even worth the effort. I never cc'd the head before I put it on so it could be running lopsided as hell. Seems like every single option involves a tear down. Why keep sinking time and effort into something that will never be more than a p.o.s?

My own sidenote: I love to learn new things, but some times understanding new concepts with out seeing them in action doesn't make any sense. Thats what screws me the most. I work in a parts house and know enough about cars and systems to be the top salesman. I can usually explain what I know so others can understand it, even if they are not car people. Don't let the basicness of my inquiries fool you into thinking I don't know anything. Derfinately not ASE certified, but I could almost pass most of the tests. Supension, transmissions, newer brakes, way over my head. I could be a hell of a wrench if we were still in the '70's
_________________
Keep on Dubbin'!
Back to top
View user's profile Send private message Gallery Classifieds Feedback
modok
Samba Member


Joined: October 30, 2009
Posts: 26743
Location: Colorado Springs
modok is offline 

PostPosted: Sun Nov 11, 2018 10:05 pm    Post subject: Re: Exhaust temps Reply with quote

I agree with Ralf
Widebands are very common now, and useful especially for tuning turbo and high powered engines at WOT, because at that point things happen very fast, including damaging the engine.

But widebands or any sensor, do not replace the basic ways we do this.
For instance, very simple you adjust the fuel and timing for best power at whatever RPM and throttle position, and assume this is about 13-1 afr.
If the widebnand says 13, then great, if not, I'd assume I'm right and it's wrong, and look for why.

For idle and light throttle tuning IMO it is more about what the engine will accept, which is a matter of experiment and find out, rather than shooting for any particular number.
A wideband sensor cannot know about exhaust contamination OR over scavenging, or combustion efficiency, but you can guess these things yourself by logic, and what you DO know. The more you know the better, having a wideband sensor or egt probe is great sure, but I feel people today rely too much on sensors, and not fully utilizing their own senses and brains, which is how we HAD to do it before, and still works now too.
Back to top
View user's profile Send private message Gallery Classifieds Feedback
ralf
Samba Member


Joined: July 08, 2008
Posts: 1215
Location: r4
ralf is offline 

PostPosted: Mon Nov 12, 2018 5:10 pm    Post subject: Re: Exhaust temps Reply with quote

hey wow atleast you took my post.. exactly as i intended it to be...
sort of a guideline or preview to what you would deal with
and not get offended... hey nowadays just telling people "its not daytime its night time now" they get upset hahaha

but ok reading back to ur original post a 1641dp with dual 34ict correct?

lets first establish ideal main jet window size (from 130-137) i dont know maybe the guys can help us here..
- then check urs if its correct or within range etc...

a sync tool/kit establishing that both carbs pull the same at idle and when revved = fully sync'd

...get the tming to an ideal range (say a 009.. 8btdc idle and 28 at 3k rpm)

if all that is done... then the mechanical side of tuning is next..
valve lash good etc? exhaust or intake leak etc?

- funny story.. i recently (last week) retuned a civic i tuned a month ago.. efi/ecu ... and for some odd reason when he came back the wideband reading wasnt as close to how i tuned it the month prior!? without any changes i was susprised... and as i retuned it...

i find out from owner.. he had someone else set the lash = other than my guys... so that shows how the a/f changes can change with as simple as a valve lash adjust.. not just idle but even part throttle etc...

sorry i dont mean to turn ur thread into "tuning ur engine" thread but i do believe u will get there sooner than expected...

IMO regardless if the head has different cc's etc? it shouldnt run as bad as u describe now vs how it ran before... so im suspecting something is amiss or off and u will get into the bottom of it for sure
_________________
Flow Through a Curved Conduit

porting my SP head for my brother's project
https://youtu.be/OS_mVjQuqgk
Back to top
View user's profile Send private message Instagram Gallery Classifieds Feedback
Bob Brugge
Samba Member


Joined: April 09, 2015
Posts: 721
Location: Missoula, MT
Bob Brugge is offline 

PostPosted: Fri Nov 16, 2018 7:41 pm    Post subject: Re: Exhaust temps Reply with quote

Thanks for all the responses.
The truth is it doesn't run the way I want it to. Valves are at .006 stone cold. 009 is set at 30* at WOT. Carbs are indeed 34ict's. I haven't synced them yet and that may be all or the majority of my issue, or I could have really screwed the pooch when the plug melted the head. Not entirely sure how a plug hole failure would lead to piss poor oil pressure reading on the light. I can seee how mis matched heads could potentially lead to a whole bunch of new headaches.

I still have my other head with the brand new valves, keepers, springs and guides. The head that fried has hd single springs on it and a 3 angle valve job. Not sure how terrible it would be to put ground valves into non ground seats or if I should bite the bullet and get them done. Shouldn't cost a bunch, but the head shouldn't have melted. Point being, shit happens.

How much of a variation in chamber size is acceptable? I measured my other set at something like 49cc. I have it written down somewhere. Seems to me even a few cc's would change the cr on the one side and cause havoc.
_________________
Keep on Dubbin'!
Back to top
View user's profile Send private message Gallery Classifieds Feedback
Display posts from previous:   
Reply to topic    Forum Index -> Performance/Engines/Transmissions All times are Mountain Standard Time/Pacific Daylight Savings Time
Page: Previous  1, 2
Page 2 of 2

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

About | Help! | Advertise | Donate | Premium Membership | Privacy/Terms of Use | Contact Us | Site Map
Copyright © 1996-2023, Everett Barnes. All Rights Reserved.
Not affiliated with or sponsored by Volkswagen of America | Forum powered by phpBB
Links to eBay or other vendor sites may be affiliate links where the site receives compensation.