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

here are pics of the plugs i took out,

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

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 . . .

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.

Ambient temps don't impact head temps all that much. They absolutely DO impact oil temps a lot, however.

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.

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

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

Baywindow T4 guys would kill for temps talked about here.

Dr Phil: http://www.914world.com/bbs2/index.php?sho...mp;#entry377466

@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

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.

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

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.

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.

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

Y'all are making me very apprehensive about the many times I have cruised interstates at about 75+MPH with my 1.7L humming, and I don't have an oil temp gauge!

While you were in there, did you examine the cooling fins on he heads ?
The 2L heads i acquired had lots of casting flash partially blocking off cooling passages particularly around the exhaust ports. Over time gunk had built up in those passages almost completely blocking off cooling flow thru those passages. i spent a LOT of time drilling out that flash to maximize cooling air flow areas. My heads stay under 300 at highway cruising speeds.

Click to view attachment

I dont run head or oil temp gauges on my 1.7, the drive is more enjoyable that way.

Use good oil, keep the revs up under load, and dont worry about it. 1.7s are pretty tough lumps.

Nice! I've been eyeballing these to send output via Bluetooth to my phone. It's the best way I can think to be able to monitor CHT and keep my stock gauges. Any recommendations on a sensor?

I'm using this one....

http://thesensorconnection.com/cht-sensors...re-12-and-14-mm

My setup is a "rub-your-tummy-pat-your-head" where the Type K is going into the adafruit, which outputs a 0-5V to the Microsquirt, which uses a .inc file to convert to *F, which can output via the DB-6 to Bluetooth, which is received by a $50 Lenovo Android tablet running ShadowTuner displaying "gauges" and doing data-logging...pshew!

All so that I can play with a computer in a 50-yr-old car. 'Cause...cause.

I use one of those sensors for each cylinder and my ECU has 8 direct inputs for that kind of sensor plug and sends all the data over bluetooth to my tablet. Pretty nifty tech but the saying "the more you know the more you worry " is definatly true. I still dont know why my cylinder 1 is running about 35-40F hotter than cylinder 2-4.

If it makes you feel any better a 30-40F delta between cylinders is almost insignificant from an air cooling perspective. Likewise 30-40F is almost insignificant with respect to running clearnaces between piston and cylinder.

1) From a cooling perspective, the convective cooling depends on the temperature delta between the object being cooled and the cooling air as a main variable. 30F just insn't that much of a %. Maybe 10-13%.

2) My theory as to why #1 runs slightly hotter for you.

As air flows out of the fan housing on it's way to #1 it has to flow over the top side of cyl #2 first picking up some heat along the way. Since #2 is closest to the fan, and static pressure is higest nearesst to the fan outlet and also flows a bit more air over #2. The way the tin is formed, you'll end up with a sligher higher static air pressure above #2 than you will on #1. Air flow depends on a static pressure delta to flow. Notice the tin decreases flow area as it moves towared #1 (and #3) to try to keep static pressure up. Higher static pressure difference = higher airflow. Cylinder # 3 is hottest because a portion of the airflow going to #3/#4 is diverted though the oil cooler so #3/#4 are starting off at a bit of a airflow disadvantage. Also, when oil cooler flap is not fully closed the bend on it probably helps divert more are over #4. Either way, since some airflow is being diverted to the cooler on 3/4 side, the 3/4 side is the one the side that tends to run hottest with #3 being the hottest of them all.

All the above depends on the assumption that your cylinder fins are equally clean and clear on all cylinders which is usually a big assumption.

Don't worry - Be happy it runs at all!

The cylinders all run at different temps and that's due to their distance from the cooling fan. Typical cruising temps on my 2270 were:
1) 300
2) 275
3) 325
4) 300

That's an oversimplification and those 25 degree margins I just listed between cylinders shouldn't be taken as a standard (could be more or less on any given engine), but what should be true if you're tuned correctly is that 2 is always coolest, 3 is always hottest, and 1 & 4 are pretty close like within 5-10 degrees of each other. And if you look at their distance from the fan, it makes sense.

But if you have one cylinder that's way out of line with this, then it's likely down to tune. Either that cylinder is running too lean or too rich, or you might also have some kind of physical blockage of cooling air.

The 4 channel head temp gauge and AFR gauge became really useful for tuning my Dells, because I would adjust until I hit roughly those temp margins and a 12.7-13 AFR, and then fine tune with the snail. Once I got to know the car really well, I eventually didn't even need the snail.

Same thing with airplane engines. We have used these things (Lycomings and Continentals) and their variants for a century without problems. Yet today, we have access to low-cost engine management systems and people are freaking the fudge out about the information they're seeing. 'Taint nothin' different than before, you only know about it now. What are you going to do about it?

That's why I removed the center console gauges in my street 914, and I don't run visible gauges in my race 914 (I datalog the race car and have a big red "park the car, monkey" red LED flashy thing when data gets out of bounds.)

There's value in "just ensuring all your stuff is in good shape and enjoying the drive."

Wise words.

thing is the 2.0 cars have a history of running warm and dropping valve seats, so i think its wise to esure its in good shape, soundly maintained and running and then enjoy the drive" and i so agree. I am at that point now i think, but i live and a very warm area, my oil temps used to be too high on long hard runs and now is fine with tha aux oil cooler, then i pulled it all and cleaned it all up, and i finally sourced all the correct cooling tins for the underside after completing the back dated exhaust, and that helped the head temps, now, i am putting the proper 4th and 5th gears back in , but just knowing that i am really fine now as i really dont go over 320 unless i went into that 5th gear , so now i know and know whats best, i will bet those head temps will be just fine once the proper gearing is installed, but i wll be able to atleast monitor this after the change and also make sure i am not pushing it too hard when up in the mountains later next month and for Octeenerfest later this year. but i do have peace of mind to know i am just fine right now with how i am running my car when i do drive it to work. Today driving to cars and coffee i was right at 290-300 at 3200rpm 4th gear cruising at 60mph, so nice and cool, just perfect. i keep it at about 12.7-13 on my AF and the plugs look perfect not too hot and not too rich on the plug analysis so i will leave the MPS alone and cruize on!!!

the new TO bearing goes in later today, wish me luck on my first solo transmission pull for swapping back in the original 4 and 5 gears too.

Later!

I don't think anyone's freaking out. I think it's a matter of wanting to understand a system, so that when there's a problem you can understand why the problem is happening. Knowledge is power.
When I had the 4 channel head temp I gauge, I didn't sit there staring at it while I was driving. I also didn't freak out at the info it was telling me. I found it fascinating to understand and learn how the engine was working under different conditions. And it was a tool that I used to ensure the car was in a healthy tune, so that I could enjoy the drive even more, knowing that there weren't any issues. That 914 with the 2270 was the most fun car I've ever owned, and the only I car I really miss and regret selling. I often wonder where it is now, and I hope that whoever owns it is treating it well.