914 rough running

[rhtrudder]

My engine does not like to run in the boost range if the fuel has gone a bit on the stale side which doesn't take long , unsure what is happening inside the combustion chamber to make it run rough , below 30 on the map gauge its fine , would the higher compression cause it to detonate , air box temps are cool so I guess internal temps would not be the cause. It took a while to figure out what was going on. as soon as I swapped the fuel over for fresh it came good , tipped the old fuel in the bike.

 

 

[Downunder]

Lots of reasons for bad fuel.

 

Some like 98.

 

Some think 95 is more stable.

 

General consensus is that in vented tanks it degrades faster.

 

I've taken to emptying my aircraft tanks into Jerry cans (therefore sealed) if not flying for a week or so.

 

I was putting the older fuel in my car but have a diesel now...

 

 

[rhtrudder]

So do you think it could be detonation that is causing the engine to falter

 

 

[Birdseye]

Is it a possibility that fuel flow is insufficient to cope with the demand from a high MAP?

 

 

[AVOCET]

If it runs better with fresh fuel , good bet its the fuel .

 

Ive had similar issues with stale &or contaminated 95 & 98 , ive gon back to avgas , and have resolved the build up of crud by running a tank of fress mogas when its available and i'm about to do a lot of flying .

 

I will pull the heads off at 200 hrs anywhoo. This isnt a rotax , LCH 3300 jab . Same issues with the cooler running heads .

 

I found by draing tanks and leaving them dry for longish periods the fuel lines tend to dry out and on one occasion i had fuel leaks when i filled up again

 

I leave a few litrs of avgas in the tanks ( fibro glass ) metal tanks are kept full , keeps everything moist .

 

Mike

 

 

[Yenn]

It could be detonation. Wht are the CHTs doing at this time. Detonation would cause them to go high, and EGTs could drop. Whatever is happening it is not good.

 

 

[rhtrudder]

Engine temps would have been low as it wasn't long after warm up , unsure about EGTs , the engine is fitted with a intercooler thanks to the previous owner so the air box temps are always low . I realize it was poor fuel but wondered what was happening internally ,once I eased the throttle back it ran OK ,only seemed to falter in the boost range. Thanks for the input.

 

 

[AVOCET]

Engine temps would have been low as it wasn't long after warm up , unsure about EGTs , the engine is fitted with a intercooler thanks to the previous owner so the air box temps are always low . I realize it was poor fuel but wondered what was happening internally ,once I eased the throttle back it ran OK ,only seemed to falter in the boost range. Thanks for the input.

Are the intercoolers a common Mod . on these engines , ???

 

Mike

 

 

[rhtrudder]

I haven't seen any others but I don't think there are many 914' s out in there, looks like it was made to suit this aircraft. I fitted a temp probe in the air box and they rarely get above 40c . I bought the plane off the bloke who was building the Spitfires in Queensland so I guess the intercooler was made locally , it is a tight fit inside the cowl.