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> Cylinder head temps and spark plugs, can it make a 20-40 degree head temp difference
DRPHIL914
post Apr 13 2021, 07:41 AM
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so sunday afternoon i decided to take a look at my plugs, last changed out 3 years ago, and wanted to see how they look, check gaps etc, while out i just changed them out for the Bosch super than i had on the shelf since i got them at okteenerfest a few years back,

now, i watch my CHT gauge and temps really close and ive been driving the car more past few weeks with the good weather and ive been sorting out a lot of issues, but watching my temps at certain speeds and RPM levels.

So yesterday and today i noticed that where cruising on the flat at 60mph ive been right at 280 or so but not over 300, and yesterday and today i was at 320-340. and passing pushed up to 350, and i had not touched 320 in the past 2 weeks driving the car regular.

so, ambient temps are not up that much it was 60-65 past 2 days. my question is , could the plug change make that much of a difference ? or did something happen with the thermocouple around the #3 plug that is making it read higher? thats 30-50 degrees higher than where i was at just days ago.

I did some more plug research and i know tha the Capt. and others recommend the
Bosch W7CCor W7DTC
or NGK BP6es, or theBR6es/ B6es , the difference being r for resistor, p protected.

so with this , what do you guys run on a 2.0 or any for that matter,
can the change in plug make that much of a difference?
- I will look at the plug box closer, but outside of the box just says Bosch super

- also plugs looked pretty good no black soot build up, actually looked like tune is pretty good but maybe just a touch on the lean side, but he AF indicates highway levels being at about 13.5 but vaires from 12.5-14 more on the lower side on idle and lower rpm crusing around town and more lean on higher speeds , it does drop quite a bit to 12. 5 on WOT.

Phil
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DRPHIL914
post Apr 13 2021, 07:52 AM
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here are pics of the plugs i took out,


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rfinegan
post Apr 13 2021, 09:58 AM
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I recently hook up my CHT and mine read 350, high too. Will be watching..Stock 2.0djet 75 with 2.0 SS exchangers
I will perform a reality check with some boiling water to baseline the set up
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DRPHIL914
post Apr 13 2021, 10:17 AM
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QUOTE(rfinegan @ Apr 13 2021, 11:58 AM) *

I recently hook up my CHT and mine read 350, high too. Will be watching..Stock 2.0djet 75 with 2.0 SS exchangers
I will perform a reality check with some boiling water to baseline the set up

about same set up as me - i read you will have to use oil, as the water boiling point will be too low to test the sensor up to 450.

Phil
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MM1
post Apr 13 2021, 10:52 AM
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Wow-350- I didn't realize the temps can get that high. I'm new to aircooled (cars - we never checked on our motorcycles) - I wonder what temps are when the weather is 92-100 in the East and 100-115 in the West?

Just read a couple of quotes from thefabricator.com:

https://www.thefabricator.com/thewelder/art...t-for-aluminum-



"Now to the question you didn’t ask, which is whether it’s a good idea to use aluminum at service temperatures of 400 degrees F (or worse, 600 degrees). Even if the maximum temperature is 400 degrees, the answer is probably not. Just like steel, aluminum alloys become weaker as the service temperature rises. But aluminum melts at only about 1,260 degrees, so it loses about half of its strength by the time it reaches 600 degrees.

This means the strength of welded 6061-T6, which is 25 KSI at room temperature, is only about half of that (12 KSI) at 600 degrees. Even at only 350 degrees, its strength is only 17 to 18 KSI. Most codes do not give allowable stresses for aluminum alloys for service temperatures above 350 degrees. So aluminum pressure vessels and piping systems are usually restricted to a maximum service temperature of 350 degrees. Trying to use aluminum at a service temperature of 600 degrees is probably a very bad idea.

I know a few of you reading this will probably dispute this considering we use aluminum alloys for cylinder heads and cylinder blocks, where the combustion chamber gets a lot hotter than 350 degrees. While that is true, it doesn’t mean that the entire head or block gets very hot. Remember that there is cooling water is constantly flowing in the heads and block, keeping the service temperature at 200 degrees or less for the bulk of the material. It is only a very thin layer of aluminum immediately around the combustion chamber that is exposed to high temperatures, while the bulk of the aluminum stays at fairly low temperatures."


Good thing we don't use that nasty "water" stuff . . . (IMG:style_emoticons/default/evilgrin.gif)

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76-914
post Apr 13 2021, 11:07 AM
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QUOTE(rfinegan @ Apr 13 2021, 08:58 AM) *

I recently hook up my CHT and mine read 350, high too. Will be watching..Stock 2.0djet 75 with 2.0 SS exchangers
I will perform a reality check with some boiling water to baseline the set up

Water will only reach 212F in the open atmosphere @SL. Or close to 60% of the value you want to verify. This leaves a lot of room for error. I found oil to be a better medium to work with when verifying temps above 200F. (IMG:style_emoticons/default/beerchug.gif)
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BeatNavy
post Apr 13 2021, 11:34 AM
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QUOTE(MM1 @ Apr 13 2021, 11:52 AM) *

Wow-350- I didn't realize the temps can get that high. I'm new to aircooled (cars - we never checked on our motorcycles) - I wonder what temps are when the weather is 92-100 in the East and 100-115 in the West?

Ambient temps don't impact head temps all that much. They absolutely DO impact oil temps a lot, however.
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DRPHIL914
post Apr 13 2021, 12:12 PM
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from another thread on head and oil temps from Jake- , first take away is 2.0 d-jet run hotter, so tune is very important. another is you just don’t want to go over 400, bad no matter what.
need to stay under that , staying under 350 even better unless for short periods of running hard or up hill. i was super happy i was just staying around 280-300, - according to his research 320 is ok, but i don’t see what changed. i changed plugs no tune adjustment so either the plugs are running hotter or the sensor is reading hotter now, hope i didn’t mess up the thermocouple . i may get an NGK 6, they are supposed to run cooler.


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VaccaRabite
post Apr 13 2021, 12:16 PM
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350 for head temps is totally fine when pushing the car on the highway.
I don't usually back off the throttle until I start getting above 370 - which will happen on hot days driving the LONG PA hills at 80+mph once the engine heat soaks (IE - longer drives).

Remember - if you are smart, you have the thermocouple on Cyl 3 and that is the hottest cylinder.

Zach
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Highland
post Apr 13 2021, 12:29 PM
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Just curios what gauge you're using.

I'm using a VDO CHT gauge which I know is not temperature compensated and readings can vary based on engine compartment temperatures.

https://www.ratwell.com/technical/VDOGauges.html#cht
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djway
post Apr 14 2021, 12:25 AM
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Baywindow T4 guys would kill for temps talked about here.
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GregAmy
post Apr 14 2021, 05:29 AM
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Dr Phil: http://www.914world.com/bbs2/index.php?sho...mp;#entry377466
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DRPHIL914
post Apr 14 2021, 06:06 AM
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QUOTE(Highland @ Apr 13 2021, 02:29 PM) *

Just curios what gauge you're using.

I'm using a VDO CHT gauge which I know is not temperature compensated and readings can vary based on engine compartment temperatures.

https://www.ratwell.com/technical/VDOGauges.html#cht

@Highland
my CHT is Dakota Digital,

i agree with Greg and others that for the most part my temps are good, what i was wondering the most is the increase suddenly under identical conditions, but one factor changed was the plug change and if that was possible for a plug to run 20-30 degrees hotter.

Zac, yes its on the #3
@VaccaRabite

Greg, thats a great referrence for proper running temps. I think once i get the stock 4th and 5th gears back in this car it wll help keep my rpms up higher and cool the heads better, right now, today on the way in to work i was around 290-310 cruising in 4th gear at 60-65 mph, which is just fine, but going to 5th at about 70 i went up to 340, rpms too low lugging motor causing increased head heat. but like i said that is a bit higher than before the plug change, so either i effected the thermocouple connector, the plugs running hotter, or its a coincidence and our warmer days over the past 3-4 days is making that much of a difference. Oil temps are just fine.

@GregAmy

Transmission is getting pulled saturday to put in new TO bearing and return gearing to stock
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era vulgaris
post Apr 14 2021, 06:57 AM
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QUOTE(DRPHIL914 @ Apr 14 2021, 07:06 AM) *


today on the way in to work i was around 290-310 cruising in 4th gear at 60-65 mph, which is just fine, but going to 5th at about 70 i went up to 340, rpms too low lugging motor causing increased head heat.


I spent two years with a 4 channel Stratomaster Velocity head temp gauge on the last 914 I owned, and learned alot about head temps. One of those things was that above 60-65 mph, aerodynamics matter ALOT.
With the top on and windows closed, you should see a roughly 20 degree increase in head temps above 60-65 mph vs below it. I always called that the "air wall", and it was the speed at which the air starts to noticeably push back against the car. If your windows are down or if the top is off the car (both of these things disrupt the aero significantly) you may see an increase as much as 30 degrees as the engine has to work even harder to push the car through the air.

My 2270 typically ran around 325 on #3 with an AFR between ~12.5 and 13 at cruise below 60mph. Above 65mph with the windows up and top on I was around 340 degrees. And I never shifted into 5th until I passed 70mph because of this, so that I had at least 3k rpm in 5th gear. If I had the top off, I was around 350-360 above 70 mph.
Now imagine what that does to a person whose car is in a bad state of tune or missing cooling tin, driving 75mph with the top off! It's easy to see how valves get stretched, seats drop, or heads crack.

BTW, have you tried changing back to your old plugs to see if it takes the temps back down? Spark plugs were one thing I never experimented with, as I only used the plugs McMark recommended for the engine he built.
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GregAmy
post Apr 14 2021, 07:32 AM
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Based on Raby's post, I don't think your numbers are out of whack with D-Jet.

For reference, I'm using BPR6ES and seeing around 275-290 when cruising on the flats. But my experience is not necessarily relevant since I'm using Megasquirt on the D-Jet induction.

I'm using a Sensor Connection Type K on #3 ported through an adafruit amplifier and data logging through the Megasquirt. Not really helpful for those that need a gauge but it's a neat-o cool piece of kit so I wanted to share. If you can do data logging and can do w/o a gauge I highly recommend it:

https://www.adafruit.com/product/1778?fbcli...klxpgfZe5JzOnjA
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Mark Henry
post Apr 14 2021, 08:05 AM
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I average 300F but I see my temps go up as much as 50 degrees on a real long steep hill. With
375f you start into heat soak issues and by 400F the heads start to get soft.

Biggest killer of heads is dirty, greasy crap or mouse nests clogging the fins and oil cooler.
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DRPHIL914
post Apr 14 2021, 08:45 AM
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QUOTE(Mark Henry @ Apr 14 2021, 10:05 AM) *

I average 300F but I see my temps go up as much as 50 degrees on a real long steep hill. With
375f you start into heat soak issues and by 400F the heads start to get soft.

Biggest killer of heads is dirty, greasy crap or mouse nests clogging the fins and oil cooler.

true. i should point out that while the motor was out 3 years ago during body work,
i went thru and had all the tin replaced or redone and finally got all the air guide tins for the full back dating, so it was completely cleaned up and put back with new clean tin and air guides, bellows etc the flaps all work correctly. what is interesting is how fast that head temp comes back down too, not like oil temps that take a while of course to come back down, i see the head temp change once load changes and RPM come down very quickly.
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FlacaProductions
post Apr 14 2021, 08:47 AM
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I agree w the suggestion of putting the old plugs back in and seeing if the readings return.
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DRPHIL914
post Apr 14 2021, 09:57 AM
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QUOTE(era vulgaris @ Apr 14 2021, 08:57 AM) *

QUOTE(DRPHIL914 @ Apr 14 2021, 07:06 AM) *


today on the way in to work i was around 290-310 cruising in 4th gear at 60-65 mph, which is just fine, but going to 5th at about 70 i went up to 340, rpms too low lugging motor causing increased head heat.


I spent two years with a 4 channel Stratomaster Velocity head temp gauge on the last 914 I owned, and learned alot about head temps. One of those things was that above 60-65 mph, aerodynamics matter ALOT.
With the top on and windows closed, you should see a roughly 20 degree increase in head temps above 60-65 mph vs below it. I always called that the "air wall", and it was the speed at which the air starts to noticeably push back against the car. If your windows are down or if the top is off the car (both of these things disrupt the aero significantly) you may see an increase as much as 30 degrees as the engine has to work even harder to push the car through the air.

My 2270 typically ran around 325 on #3 with an AFR between ~12.5 and 13 at cruise below 60mph. Above 65mph with the windows up and top on I was around 340 degrees. And I never shifted into 5th until I passed 70mph because of this, so that I had at least 3k rpm in 5th gear. If I had the top off, I was around 350-360 above 70 mph.
Now imagine what that does to a person whose car is in a bad state of tune or missing cooling tin, driving 75mph with the top off! It's easy to see how valves get stretched, seats drop, or heads crack.

BTW, have you tried changing back to your old plugs to see if it takes the temps back down? Spark plugs were one thing I never experimented with, as I only used the plugs McMark recommended for the engine he built.
QUOTE(FlacaProductions @ Apr 14 2021, 10:47 AM) *

I agree w the suggestion of putting the old plugs back in and seeing if the readings return.


yes, i had considered that, and will try that either tomorrow or friday depending on the weather/ rain. and i may go get the BPR6ES NGK's and experiment with those, that was one recommendation the B6ES either P or R or PR(p=protected R=resistor) by the late Capt. Crusty in an older thread on this subject.


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DRPHIL914
post Apr 14 2021, 10:24 AM
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so i took out Bosch WR7DC+, put in WR7CC+,
which according to the Capt. is correct, he says don’t use the extended tip, so not BP not 5 on the NGk, but “6” on those and the WR7 on Bosch


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