The Autonerdz Community Forums - Question about Compression Waveform

James H Senior Member Picogroup Offline Bike Nerd Posts: 165 Waterloo Ontario Canada Gender:	Question about Compression Waveform Oct 14^th, 2017 at 7:32am This is a capture from a V Twin 1100cc Honda Rear Cylinder with free flowing aftermarket pipes. Bike appears to run fine but I question the above excessive pressure seen after the exhaust valves open. Never seen this much pressure on anything else I have checked but this is all relatively new to me. Thoughts?
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Mick

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Re: Question about Compression Waveform
Reply #1 - Oct 14^th, 2017 at 10:17am

James H wrote on Oct 14^th, 2017 at 7:32am:

This is a capture from a V Twin 1100cc Honda Rear Cylinder with free flowing aftermarket pipes. Bike appears to run fine but I question the above excessive pressure seen after the exhaust valves open. Never seen this much pressure on anything else I have checked but this is all relatively new to me. Thoughts?

Hi James
Does the front cylinder have the same characteristic hump?

Are these cams late open late close by nature on these Honda engines?

If I am looking for pressure in the exhaust I would never do a snap throttle capture Wink

I would increase the engine speed to 1200 to 1500 rpm max and hold it steady to get the results I feel would tell me I have a restriction on exhale.

Your compression tower has a slight lean but nothing I would worry about, the engine speed is not as stable as I am use to in seeing but if this is normal to you on a motor bike engine, when you have an imbalance due to the WPS in one of the cylinders then I will take that as normal.

So do you have the companion cylinder from the front?

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Re: Question about Compression Waveform
Reply #2 - Oct 14^th, 2017 at 10:31am

James H wrote on Oct 14^th, 2017 at 7:32am:

This is a capture from a V Twin 1100cc Honda Rear Cylinder with free flowing aftermarket pipes. Bike appears to run fine but I question the above excessive pressure seen after the exhaust valves open. Never seen this much pressure on anything else I have checked but this is all relatively new to me. Thoughts?

Is the rest of the bike stock?

Is valve lash adjustable?

How many miles on the bike?

Does it have manual chain adjustment or auto tension?

I am glad you did the snap! I take them on most all our captures. Cool

It gave you something to think about.

Spence

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Spence LSD Guide Picogroup Offline Posts: 8,025 Jeffersonville Pennsylvania USA Gender:	Re: Question about Compression Waveform Reply #3 - Oct 14^th, 2017 at 3:16pm James in looking at your capture I question valve timing being late. Mick made question to it as well.
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James H

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Re: Question about Compression Waveform
Reply #4 - Oct 15^th, 2017 at 4:01pm

Hi Guys, bike is hydraulic lifters, all stock except for aftermarket pipes with straight thru baffle. It is high mileage for a bike at 60,000 km and has an auto cam chain tensioner. Cam timing is not unusual in comparison to other V twins as far as I know. The hump is there on the other cylinder. I have run a similar bike with stock exhaust and the pressure was basically 0. I also did hold the revs up Wink

and the pressure went up (see attached). I also attached a capture where I pulled the exhaust head pipe back a couple of inches while it was running. Pressure dropped. I didn't get much time with the bike as it was running fine and I just happened to grab a couple of captures for my database when I noticed this, what bothers me is why when the pipes are of the same head pipe dia as stock and has a straight thru baffle versus the stock "z hemoltz" type muffler. The stock one does have linked pipes however and may have something to do with it.

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Pipe_on_and_off.psdata (9955 KB | )

Steady_2_200_rpm.psdata (5558 KB | )

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Re: Question about Compression Waveform
Reply #5 - Oct 15^th, 2017 at 4:46pm

James H wrote on Oct 15^th, 2017 at 4:01pm:

Hi Guys, bike is hydraulic lifters, all stock except for aftermarket pipes with straight thru baffle. It is high mileage for a bike at 60,000 km and has an auto cam chain tensioner.

Cam timing is not unusual in comparison to other V twins as far as I know.

Hi James, your comment above. How are you comparing? Did you do an actual measurement?

Also as far as my comment on cam timing it looks late when I consider a 4 stroke engine in general.

James H wrote on Oct 15^th, 2017 at 4:01pm:

The hump is there on the other cylinder.

I see that. Meaning the condition in not related to just the one cylinder.

James H wrote on Oct 15^th, 2017 at 4:01pm:

I have run a similar bike with stock exhaust and the pressure was basically 0.

Can you post that capture?

James H wrote on Oct 15^th, 2017 at 4:01pm:

I also did hold the revs up Wink

Excellent! Smiley

I have mentioned in the past I prefer to have both. Cool

If you look at the two you will see differences.

James H wrote on Oct 15^th, 2017 at 4:01pm:

and the pressure went up (see attached). I also attached a capture where I pulled the exhaust head pipe back a couple of inches while it was running. Pressure dropped. I didn't get much time with the bike as it was running fine and I just happened to grab a couple of captures for my database when I noticed this, what bothers me is why when the pipes are of the same head pipe dia as stock and has a straight thru baffle versus the stock "z hemoltz" type muffler. The stock one does have linked pipes however and may have something to do with it.

Is there a capture you didn't post or I missed?

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Mick LSD Guide Offline I learn every day Posts: 7,471 Toronto 400ft Ontario Canada Gender:	Re: Question about Compression Waveform Reply #6 - Oct 16^th, 2017 at 4:32am James H wrote on Oct 15^th, 2017 at 4:01pm: I also did hold the revs up and the pressure went up (see attached). I also attached a capture where I pulled the exhaust head pipe back a couple of inches while it was running. Pressure dropped. Great captures James with all the info you need
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James H

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Re: Question about Compression Waveform
Reply #7 - Oct 16^th, 2017 at 1:36pm

Here is the Front cyl as well as a capture from the same Model but different year Bike with stock exhaust. I managed to find some cam timing figures (if their right) and interestingly enough frt and rear cyl's are different. The higher pressure must be just down to a slight difference in head pipe diameter - length and muffler volume between the stock and aftermarket pipes. I'm surprised it seems to run a strong as it does considering. I am going to have to compare some dimensions of stock versus aftermarket when I get a chance.
Front
Int - 5,30
Exh - 30,5
Rear
Int - 2,33
Exh -37,2

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ICC_running_Front_Cyl.psdata (4781 KB | )

VT1100_all_Stock_Reference.psdata (7129 KB | )

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Spence LSD Guide Picogroup Offline Posts: 8,025 Jeffersonville Pennsylvania USA Gender:	Re: Question about Compression Waveform Reply #8 - Oct 16^th, 2017 at 3:54pm Okay James... What do you think of these captures eh?
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StitchB

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Re: Question about Compression Waveform
Reply #9 - Oct 20^th, 2017 at 8:37am

James,

killing time here and noticed this. Will take a little time too digest but great. Happy to see your using the Pico, looks great, and also getting some great input from both sides of the border, from 2 of the best I might add, but I have been wrong before.

Yeah, wondering about condition of exhaust, thought does this have a Cat?, 2 funny.

StitchB

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Spence LSD Guide Picogroup Offline Posts: 8,025 Jeffersonville Pennsylvania USA Gender:	Re: Question about Compression Waveform Reply #10 - Oct 20^th, 2017 at 8:42am Glad you brought this back up AKA. I'm not sold on the exhaust restriction yet. Was hoping James would hop back in here.
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Re: Question about Compression Waveform
Reply #11 - Oct 20^th, 2017 at 9:13am

Spence, howdy days. Yeah looked it over, and agree valve timing late IMO, plus maybe some exhaust issues, but you know if I'm right even a blind squirrel finds a nut once in a while.

All regardless glad to see James getting some use out of the the tool, probably @ this point a forerunner in the game in the bike world.

Would like and get him into one of the auto trade shows for some training as he will never see it in the bike world, but he is for sure on the right track with Mick and your input, good for him.

I go to the ATE one here in Seattle, 3 days in the spring, my pee brain can only digest so much of it in one fell swoop, but is great. I should fly out some day and all of us could have lunch in Canada, then dinner in the states, you'll be buying of course, LOL.

StichB.

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James H Senior Member Picogroup Offline Bike Nerd Posts: 165 Waterloo Ontario Canada Gender:	Re: Question about Compression Waveform Reply #12 - Oct 20^th, 2017 at 2:13pm Hi guys, not sure what to think. I am trying to get the bike back in this winter to check out things more things. I will revisit once I do. Larry, I did get to Nace in Chicago and got to some seminars, was really good but my brain got overloaded...lol. Hope to play some know that its getting colder here.
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Spence

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Re: Question about Compression Waveform
Reply #13 - Oct 20^th, 2017 at 7:40pm

StitchB wrote on Oct 20^th, 2017 at 9:13am:

Spence, howdy days.

Back at ya AKA

StitchB wrote on Oct 20^th, 2017 at 9:13am:

Yeah looked it over, and agree valve timing late IMO,

That's what I see in the captures

StitchB wrote on Oct 20^th, 2017 at 9:13am:

plus maybe some exhaust issues,

I don't read it as that.

StitchB wrote on Oct 20^th, 2017 at 9:13am:

but you know if I'm right even a blind squirrel finds a nut once in a while.

And I may be wrong. I had a few thoughts on some tests to prove or disprove my thoughts.

StitchB wrote on Oct 20^th, 2017 at 9:13am:

All regardless glad to see James getting some use out of the the tool, probably @ this point a forerunner in the game in the bike world.

James has put out the effort and deserves the reward for sure.

StitchB wrote on Oct 20^th, 2017 at 9:13am:

Would like and get him into one of the auto trade shows for some training as he will never see it in the bike world, but he is for sure on the right track with Mick and your input, good for him.

For the most part an engine is an engine. Learning one can surly be applied to the other.

StitchB wrote on Oct 20^th, 2017 at 9:13am:

I go to the ATE one here in Seattle, 3 days in the spring, my pee brain can only digest so much of it in one fell swoop, but is great.

I love your drive for knowledge.

StitchB wrote on Oct 20^th, 2017 at 9:13am:

I should fly out some day and all of us could have lunch in Canada, then dinner in the states,

Well get you ass on a plane and make it happen.

StitchB wrote on Oct 20^th, 2017 at 9:13am:

you'll be buying of course, LOL.

StichB.

But of course... Roll Eyes

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StitchB

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Re: Question about Compression Waveform
Reply #14 - Oct 21^st, 2017 at 1:03pm

James H wrote on Oct 20^th, 2017 at 2:13pm:

Hi guys, not sure what to think. I am trying to get the bike back in this winter to check out things more things. I will revisit once I do. Shocked

Larry, I did get to Nace in Chicago and got to some seminars, was really good but my brain got overloaded...lol. Hope to play some know that its getting colder here.

Yeah I know what you mean. Usually just throw the packet on a shelf, then some problem comes up and I say, Hey, that was in that class, now you have something to apply it too, and begines to make sense, or not. And sure does not come the first time.

If is fun too do expecially in the winter if you have a heated bay, summer is for riding.

StitchB

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