Yet another single carb thread :) Dan's 1" runners from plenum to custom head flanges

[westgl]

GL1100 transmissions and Final driver gear ratios

1st gear
80-82' 1st gear 2.50
83' 2.64 1st gear

2nd gear the same

3rd gear
80-81' 1.286
82-83' 1.250

4th gear
80-81' 1.065
82'-83' 1.000

5th gear
80-81 0.909
82-83' 0.829

Final reduction ratio
80-81' 3.09
82-83' 3.10

mcgovern61 » Tue Oct 08, 2013 5:58 am[/url]":2pxqvsvh]

dan filipi » Sun Oct 06, 2013 6:37 pm[/url]":2pxqvsvh]
Takeoffs are a little under-powered.
I'm pretty sure that has to do with some jetting size issues, a bit too rich.

Couple a questions:

Is the C5 ignition installed on this bike?

If I remember correctly, you have different transmission gears ('81?) and '83 wheels on this bike which might need more omph to get started from a dead stop?

I am only asking so that there is a fair comparison for a complete stock setup.

If there is a takeoff issue, would that be a problem if you are pulling a trailer?

 

[westgl]

I agree with Joe,

There is More torque available with the single carb. than there was with the OEM 4 carb rack.

My bike is basically stock, rebuilt

Keep the weight down on the trailer as much a possible and balanced as much as possible.

You should be fine

joedrum » Tue Oct 08, 2013 6:11 am[/url]":3j5oqfmd]
I think theres no problem at all with trailoors if it done up right ...its obvious to me the carberation is way better than stock ... especially down at tailor pulling demands

 

[KYWinger]

westgl » Tue Oct 08, 2013 6:13 am[/url]":6jc47vyw]
80-82' GL1100 has a lower 1st gear 2.50
83' 2.64 1st gear

So yes the 83' would need to have a little more revving to get away from a stop.

Final reduction ratio
80-81' 3.09
82-83' 3.10

Actually, West, it's just the opposite:
2.50 X 3.09= 7.725
2.64 X 3.10= 8.184

So the '83 would have a slight mechanical advantage.....

 

[westgl]

Yes I looked at that again.

It is higher numerically which is a lower gear ratio

But refresh and re-read that info as it has been added to.

 

[westgl]

It is not till 3rd 4th and 5th the 83' trans has a higher ratio

But a slightly lower final drive, so it probably evens out.

It is early here and I am barely on my first 1/4 cup coffee

 

[westgl]

I had a 1973' Pontiac Firebird TransAm, years ago, with a 455CI Super Duty engine, that I had gone from 3.55 rear gear to 4.10 rear gear, and it would rev much faster, and would tach higher on the freeway, and use a lot more gas.

But it was fast!

This car had Lots of torque, and the rear gears really helped the engine rev. with the cam i had in it.

I also had a 67' Camaro with a 350CI engine, and a turbo 350 auto trans, a Holley 750 double pumper carb, that my dad and i had built the engine, that had 3.73 gears in the rear end.

That car went really well, it had a Nice cam in it, and headers, it sounded great.

 

[joedrum]

ok the difference is in the secondary reduction unit ...80-82 ...is 973 ithink and the 93 is 829 ... it had to have 263 gear for better take off and to come close to matching the 250 gearing of the 80-82 witch is a little lower than 83 ... but 83 is fine gearing and the first yr of spread gearing ...its as good as 1200s just a bit lower from final drive difference in gearing as motor gearing goes the 83 is identical to 84 1200 gearing

 

[dan filipi]

Pulling a loaded trailer you'll need higher revs no matter what ignition or fuel system is on it.

My seat of the pants testing so far is take off torque with my build is very close to the stock carbs. I do feel it's lower.
Like I said earlier, the jetting isn't proper. I expect takeoff will improve with proper jets.

Gear ratio makes a huge difference no doubt about it. The low ratio of hooch has a lot to do with it being able to idle up Joe's driveway.

 

[dan filipi]

My ultimate judgement of any of these single carb installs is mpg.
Better torque is a bonus but if the mpg isn't at least 40 then in my opinion it's not worth the effort.
Granted a smoother running engine with no spitting or popping is nice but if mpg is say 30-35, for guys that put on a lot of miles yearly that adds up fast.

Mpg to me indicates how well the system is tuned.
If it's low something is wrong.

My plugs are now tan to white but that is not necessarily an indicator that it's properly tuned.
I'm posting on my phone right now so I'll explain more what I mean later.

 

[dan filipi]

dan filipi » Tue Oct 08, 2013 8:34 am[/url]":28h0ueea]
My plugs are now tan to white but that is not necessarily an indicator that it's properly tuned.
I'm posting on my phone right now so I'll explain more what I mean later.

The reason I'm saying this and want to describe what I've found in my 1" runners is to maybe help others with this information in building a manifold.
It may help someone or it may not but it also may help give an idea what to watch for somewhere along the line in fitting pipes and coupling them.

So what I've built is this:

I was not very careful in fitting the pipes into the plenum outlets because I had the idea all along I'd seal any spaces with epoxy.
What I mean is, the 1" pipes extend inside the plenum outlets.
The way it sits now is there is a space between the plenum wall and the 1" pipe, maybe an 1/8" or so.

(No comments on my 1 dimensional drawing please, I can't draw.)

I've found that raw gas accumulates in this space.
Makes sense to me now because the fuel air charge is smacking right into that pipe and interrupting the flow.

I'm pretty sure this is also making it so the idle mixture has to be set a 1/2 to 1 turn richer than it should be, which is why I'm saying good looking plugs don't necessarily mean the manifold and carb mock up are performing the best they could. Mine are tan to very light tan which would seem to indicate the mixture that does get to the cylinder IS good, but may not be consistent.

I also experience some random "loading up" at idle speed which would lower the idle, at times the idle would randomly speed up too. My guess then is this raw gas gets sucked in once it's accumulated to a point.

So anyway, I hope this helps someone.
It was sort of a knock on the head "Duh" when I pulled the carb and saw raw gas sitting there.

 

[joedrum]

well dan that's only cause it aint quite set up right ..if we had the tools to have all the edges gone this wouldn't happen ...plain and simple ...it sure brings out the point that 1" ID runners bent like yours do good in high rpm that's huge ....so there nothing wrong here it just a proto type....

 

[82a]

a quick look at other setups and imo the shortest straightest path is not necessarily the best path

looks like a combo of ~ a 90deg nicely radiused final end turn with a straight downward shot into the intake is the way to go, as it looks original

along with flowing bends where required, as opposed to short sharp kinks

https://www.google.ca/search?q=io550&cl ... h&imgdii=_

https://en.wikipedia.org/wiki/Intake

 

[joedrum]

neat pics

 

[82a]

https://en.wikipedia.org/wiki/Inlet_manifold

The design and orientation of the intake manifold is a major factor in the volumetric efficiency of an engine. Abrupt contour changes provoke pressure drops, resulting in less air (and/or fuel) entering the combustion chamber; high-performance manifolds have smooth contours and gradual transitions between adjacent segments.

interesting intake on this subaru (scroll to the bottom)

https://www.sdsefi.com/air21.html

https://www.sdsefi.com/ej22rear.jpg
https://www.sdsefi.com/ej22top.jpg

 

[Ansimp]

I keep thinking that you need bigger than 1" runners for the low speed performance. Once revs are up flow or restrictions are not an issue but I believe low speed transition needs less restriction IMO.

 

[slabghost]

Ansimp » Tue Oct 08, 2013 6:55 pm[/url]":3bz9ah8n]
I keep thinking that you need bigger than 1" runners for the low speed performance. Once revs are up flow or restrictions are not an issue but I believe low speed transition needs less restriction IMO.

Seems to me you are equating internal diameter size with restriction when there are none. We've seen that the larger diameters "require" a restriction (choke) to work properly.

 

[Dave_J]

Offenhauser made a special 360 degree "Dual Port" manifold for the Mopar 383-440 engines. All the primary's had their own small runners and the secondary's had a bit bigger ones. With smaller diameter ports, port velocity was high. Heres a picture of a port: https://www.google.com/imgres?imgurl=htt ... CD4Q9QEwBw

 

[westgl]

I had the most torque form a stop, and all through the rev range with Rev.1. it was a combination of 1.250" but reduced down to 1.125"ID at the end on the straight runner tube.

I had No Choke at the Plenum.

So if we were to increase the tube size at the plenum, then taper it down in size to say 1.050"ID at the 2/3 spot in the length of the tube runner.

This would provide speed up, and squish area for air/fuel mixture.

We would be moving the Venturi or Choke down the tube closer to just before the 90 degree tube bend.

This would be a gradual tapered reduction, to the 2/3 or 4/5 point in the tube, where this would be your smallest ID, then opening back up to full sized tube ID

 

[westgl]

when you look at the tube that enters the plenum it goes from large to smaller as it tapers down, but it never goes back to the original size.

That is where you decide taper down and stay at the smaller sized tube or taper down then open back up.

I think I can try it both ways fairly easy

 

[westgl]

Here is the tapered tubing from a Type IV

https://www.ebay.com/itm/VW-BUS-TYPE-IV- ... 4ac1992f7e