Tuned pipes engine surging issues?

[JeremyHolt]

I have a 3w 157 on KS 190 pipes. My engine surges real bad around mid range. Once you open it up, it runs okay but the mid range is terrible. I have been up and down with both needles and it is making no difference. Has any one seen this issue with any suggestions?

[Rickster]

Dick Hanson will have a more difinitive answer but... Sounds to me like you might need to either drop back on your prop load or lengthen the headers a bit.. How does it run WOT? What is your main set at to get a good top end with it a touch on the rich side?

Rick

[Tired Old Man]

The engine is trying to "get on the step". You will need to play with pipe lengths a bit more, and the prop as noted earlier.

[JeremyHolt]

I am running a 30-12 so I know I shouldnt have to drop back at least. On the high I have it set a little richer than I ran normal.

[BOSSIER_ROB]

I was going to make you a drawing simple enough for you to understand what I was talking about, but couldn't find my crayolas so this will have to do. It's kinda the same thing I was trying to explain, only a little more of a crude rig. It will work with pipes as well. Tada! No more pipes sliding off the headers. Now I can fly your aeroworks.

[JeremyHolt]

If it works you can fly it. Up high.

[aerobear]

	Quote: Originally Posted by JeremyHolt
	I am running a 30-12 so I know I shouldnt have to drop back at least. On the high I have it set a little richer than I ran normal.

Rickster was not suggesting that your engine is not capable of turning a 30x12. Dropping down a prop size is a quick and easy way of checking header length. If dropping a prop size (higher rpm) cures the problem then your header length was probably too short for the bigger prop. You then have the option of keeping the smaller prop or lengthening the header and putting the big prop back on.

You can match the prop to the header or match the header to the prop but they have to be matched.

It could be a carb problem. Two carbs from the same assembly line may not tune identically. Chainsaws and leaf blowers are only run at idle and full power. What happens in between does not matter as much to the carb manufacturer.

[BOSSIER_ROB]

	Quote: Originally Posted by aerobear
	Rickster was not suggesting that your engine is not capable of turning a 30x12. Dropping down a prop size is a quick and easy way of checking header length. If dropping a prop size (higher rpm) cures the problem then your header length was probably too short for the bigger prop. You then have the option of keeping the smaller prop or lengthening the header and putting the big prop back on. You can match the prop to the header or match the header to the prop but they have to be matched. It could be a carb problem. Two carbs from the same assembly line may not tune identically. Chainsaws and leaf blowers are only run at idle and full power. What happens in between does not matter as much to the carb manufacturer.

What he didn't state was that this engine has run great, until he put pipes on it. The pipes and headers came off another 157 and pulled like a mule on it. Think one of the pipes just slid too far back on the header, and the other didn't. That'd make it run like ass. Guess we'll see next time he fires it up.

[BOSSIER_ROB]

	Quote: Originally Posted by JeremyHolt
	If it works you can fly it high.

I'd rather be sober when I fly someone else's planes, but if you insist.......

[Rush7]

I have found that a throttle curve can help ease some of the peakiness that pipes seems to casue. I agree with the above. Change props and see what you got and then you will know what you want to do with the pipe/prop combo.