I've got my 1915CC up an running smoothly starts like a dream!!
But I have some problems with peak EGT at high throttle settings.
I'm trying to get the needle in the carb right by precision sanding it to the perfect finish.
But before I go to far Id like some advice...
Now it runs well up to 2300rpm then it starts to Choke (to much fuel) and then comes back running smooth at 3000+
I use CHT and EGT on both rear cylinders and the CHT is in the green area all the time regardless of throttle setting.
But the EGT peaks at 1400+ when giving full throttle.
Is there something that I have missed or should I continue with the needle?
Type 1 Low CHT High EGT
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FJCamper
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Re: Type 1 Low CHT High EGT
Hi Pizzant --
Wait before emorying the needle.
First question, what kind of carb(s), and your jet specs.
FJC
Wait before emorying the needle.
First question, what kind of carb(s), and your jet specs.
FJC
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pizzant
- Posts: 14
- Joined: Fri Nov 11, 2011 5:26 am
Re: Type 1 Low CHT High EGT
Hi Camper nice to hear from you again! =)
The carb in use is a Stromberg 175CD (I also have an 150 just for info)
This is what I've found out today...
I get the EGT to halt at 1300 when I fixed ann sanded a new needle but no matter if I sand more it doesnt help a bit. So I changed the jet to one that is 0.2mm wider to get more fuel into the system. Lets face it that it run like CRAP up to 3000rpm then i smooth out but still 1300... and when I hit 3200 it starts heading for 1400+ So I'm very confused right now since this jet gives alot more fuel but still at higher RPM the same results.
As a remark I notice today that the CHT also starts to move (it took some while att 3000) and when hitting fuel throttle for a shortwhile It also hit 400.
I'm very confused right now....
The carb in use is a Stromberg 175CD (I also have an 150 just for info)
This is what I've found out today...
I get the EGT to halt at 1300 when I fixed ann sanded a new needle but no matter if I sand more it doesnt help a bit. So I changed the jet to one that is 0.2mm wider to get more fuel into the system. Lets face it that it run like CRAP up to 3000rpm then i smooth out but still 1300... and when I hit 3200 it starts heading for 1400+ So I'm very confused right now since this jet gives alot more fuel but still at higher RPM the same results.
As a remark I notice today that the CHT also starts to move (it took some while att 3000) and when hitting fuel throttle for a shortwhile It also hit 400.
I'm very confused right now....
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FJCamper
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- Joined: Wed Nov 14, 2007 2:19 pm
Re: Type 1 Low CHT High EGT
Hi Pizzant,
This is for aircraft use?
FJC
This is for aircraft use?
FJC
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pizzant
- Posts: 14
- Joined: Fri Nov 11, 2011 5:26 am
Re: Type 1 Low CHT High EGT
Yes thats correct Camper
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FJCamper
- Moderator
- Posts: 2910
- Joined: Wed Nov 14, 2007 2:19 pm
Re: Type 1 Low CHT High EGT
Hi Pizzant,
Earlier on when you were having apparent icing trouble (and how did you sort that out?) we were doing some long-distance guessing, but you have just documented some carb characteristics most people never see ... how mixtures are erattic throughout the RPM range ... and by example, why fuel injection has an edge in mixtures.
Also, the 175CD carb you have would be the classic example of mixture variations because of its variable-venturi design. I'm presuming you have good O-rings on the throttle shaft. Most guys will tell you to change needles or smooth the needle, and that has effect, but as you see, not enough. Also, has anyone removed the temp compensator from your carb? And if you have it, is it working smoothly? And what oil are you using in the carb, ATF or 30w motor oil? The 30w allows more gradual changes.
On an automobile, such mixture variations are not much concern. On an aircraft, you want to "tune" your carb so that it had the mixture you want at your cruise RPM. Above and below that, the mixtures will be off.
If we were together, we'd have that Stromberg pursuaded in no time. As it is, you'll have to locate the fix and tell us what you did.
FJC
Earlier on when you were having apparent icing trouble (and how did you sort that out?) we were doing some long-distance guessing, but you have just documented some carb characteristics most people never see ... how mixtures are erattic throughout the RPM range ... and by example, why fuel injection has an edge in mixtures.
Also, the 175CD carb you have would be the classic example of mixture variations because of its variable-venturi design. I'm presuming you have good O-rings on the throttle shaft. Most guys will tell you to change needles or smooth the needle, and that has effect, but as you see, not enough. Also, has anyone removed the temp compensator from your carb? And if you have it, is it working smoothly? And what oil are you using in the carb, ATF or 30w motor oil? The 30w allows more gradual changes.
On an automobile, such mixture variations are not much concern. On an aircraft, you want to "tune" your carb so that it had the mixture you want at your cruise RPM. Above and below that, the mixtures will be off.
If we were together, we'd have that Stromberg pursuaded in no time. As it is, you'll have to locate the fix and tell us what you did.
FJC
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pizzant
- Posts: 14
- Joined: Fri Nov 11, 2011 5:26 am
Re: Type 1 Low CHT High EGT
I installed the engine last year around october.
I didn't have any EGT installed back then. It was something I added when I remade the instrument panel a month back.
The issue before was that I didnt get as much thrust out of the engine as I wanted.
I just didn't match my old (broken pistonring/leaking oil/rusty) 1835cc using a dynamometer.
This was actually not very strange... the 1835cc was an Yard coverted High comp VW with comp ration of 9.5:1 (that I didnt know when I was testing my 1915 back in the winter)
This did ofcourse lead to the fact not only that it was burned out but also the reason why I installed an EGT on my new GPAS 1915cc.
So the 1915 has a comp ratio of 7:1 which explains why I can't get the same thrust. Altho I made a test last week and it's very close to the 1835... only 50N difference.
My thoughts on the carb and after some talk to local VW guys let me down on the path that I need to sand a needle my self to get the engine to run smooth on the howl rpm range.
So yes I have achieved just that but it runs to hot at 3000rpm+ on the EGT....
and the biggest and most strange thing was that I changed the jet to one that was 0.2mm wider and the engine did ofcourse run to rich and rough at the 1000-3000 range but when reaching 3000 it smooth out but still same temp problems.
I'll might make a test flight today to see how the engine behaivs in the air, (if the weather premits)
Indeed your right about fuel injection it is also something I prefeer but as always it's a matter of cost and time.
The carb oil is an AFT for Stromberg/Zenit carbs.
I will check the temp correction etc as well.
Thx for help camper I'll inform you on the progress =)
I didn't have any EGT installed back then. It was something I added when I remade the instrument panel a month back.
The issue before was that I didnt get as much thrust out of the engine as I wanted.
I just didn't match my old (broken pistonring/leaking oil/rusty) 1835cc using a dynamometer.
This was actually not very strange... the 1835cc was an Yard coverted High comp VW with comp ration of 9.5:1 (that I didnt know when I was testing my 1915 back in the winter)
This did ofcourse lead to the fact not only that it was burned out but also the reason why I installed an EGT on my new GPAS 1915cc.
So the 1915 has a comp ratio of 7:1 which explains why I can't get the same thrust. Altho I made a test last week and it's very close to the 1835... only 50N difference.
My thoughts on the carb and after some talk to local VW guys let me down on the path that I need to sand a needle my self to get the engine to run smooth on the howl rpm range.
So yes I have achieved just that but it runs to hot at 3000rpm+ on the EGT....
and the biggest and most strange thing was that I changed the jet to one that was 0.2mm wider and the engine did ofcourse run to rich and rough at the 1000-3000 range but when reaching 3000 it smooth out but still same temp problems.
I'll might make a test flight today to see how the engine behaivs in the air, (if the weather premits)
Indeed your right about fuel injection it is also something I prefeer but as always it's a matter of cost and time.
The carb oil is an AFT for Stromberg/Zenit carbs.
I will check the temp correction etc as well.
Thx for help camper I'll inform you on the progress =)
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pizzant
- Posts: 14
- Joined: Fri Nov 11, 2011 5:26 am
Re: Type 1 Low CHT High EGT
After installation of cowling and some final taxi test I made a short test flight yesterday.
Results was intressting, During cruise I was able to get the engine up to 3400rpm and keepeing the EGT at 1400.
And the CHT stops around 400.
This is good and it told me I have to coarse pitch the prop a little more.
Im still very confused why a wider jet don't help at the higer rpm range and infact giving the same results...
My 175CD actually and strangely don't have any temp correction so that's not a issue.
Results was intressting, During cruise I was able to get the engine up to 3400rpm and keepeing the EGT at 1400.
And the CHT stops around 400.
This is good and it told me I have to coarse pitch the prop a little more.
Im still very confused why a wider jet don't help at the higer rpm range and infact giving the same results...
My 175CD actually and strangely don't have any temp correction so that's not a issue.