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I have been waiting ten months for a set of custom headers from Mintor for my 110. They finally arrived yesterday. I ordered the originals from TopDawg and there was no way they would fit my 35% Dalton Extra 260 not enough drop and way too long with no way for the front exhaust to drop. Both Mintor and TopDawg state that the header must be a given length. Well the new custom headers have enough drop but the length factor is again too long. I just cannot wait another ten months or longer for another attempt at getting it right. So can someone advise me as what the downside of cutting 27mm off of the new headers would be.

If you know what header length you need and you can fit the rest of the exhaust system
to the plane with the shorter header you can cut them.....But if the header length is correct for
a given tuned wxhaust system then shortening the header is not a good idea.

@ WRK Thanks I really do understand that the preference is on the side of not trimming them down. There is no way they will fit in the current conformation as supplied. The exhaust would have to go through the landing gear. I spent a $100 a pop to have them custom bent to my parameters it took ten months to receive delivery and they are still little over an inch too long. They were supposed to bend them so the correct amount of tube would fit within the available geometry of the airplane. A 35% Dalton Extra 260 which has pretty much a standard spacial configuration seen in most IMAC 3D ships. My question is what is the downside if I trim them by an inch and an eight?

ElfinS,

With all due respect, I'm not sure what sort of answer you expect. Only a select few of us run tuned exhausts and I don't know anyone running such of a 55cc jug except for me. What I've learned with my DLE55 is that the exhaust length can vary down to some minimum (around 29" for the 55, from exhaust flange to the reflection baffle in the pipe).....It can be longer by as much as 3" with no practical performance difference ...but not shorter than that.

If you are running a can, again I wouldn't shorten beyond that minimum.

Then again, since you have some practical issues to deal with, you may just have to try it on your own and see what you get. I'd bet no body has the exact answer you seek so why not develop it yourself.

I have made careful measurements and have determined that the new headers in the factory geometry will just clear the landing gear so I will chop a hole in the bottom of the airplane just aft of the engine vent outlet in the cowl. With this modification I will not have to alter the designed geometry of the exhaust. My thanks to those that offered their advise.

I can contrast my experiences cutting headers... not with the same engines as you, but it really makes no difference. Physics is phyisics...

I had the same quandry, trying to fit a 3W157 with canisters into a 40% Giles 202. There was NO WAY the 'recommended' 3W headers would fit so I shortened them by 2 inches. I assumed the massive 3W cannisters would still provide MORE than enough volume for the exhausts.. but the result was an engine that would NOT throttle up in a clean, linear fashion. The mid-range was 'peaky' and the engine would "come on the pipe" after I would throttle up such that I simply did NOT have a linear throttle response. I tried various props and carburetor adjustments, but the bottom line was that I had negatively impacted the mid-range of the engine by shortening the headers. The engine screamed on top and idled great, but the mid-range suffered.

My next experience was with a DA120 and Zimmermann headers and canisters. I installed them at their full length (as I had plenty of room in a 38% Hempel Decathlon). This was literally 'plug n play' as I did NOTHING to change the headers, connectors, or anything. The result was a very SWEET handling engine that exhibited linear throttle response throughout the RPM range.

Exhaust pulses are timed. 'Tuned' exhaust systems are designed to exploit these pulses by being designed around the exhaust timing. Shortening the exhaust system generally makes the engine more 'peaky' and hurts linearity and mid range. This is fine if all you intend to do is run the engine at full throttle, but NOT if you intend to use the entire throttle range as in IMAC and 3D.