Colortune device

Tweety · Post by **Tweety** » Thu Jul 30, 2015 5:39 pm

Today I got in the mail a box of jets from the USA and a colortune unit. My recoed ea81 has done about 6000 kms since total rebuild with 9.5:1 CR, a SPFI manifold (likely about double volume of stock - 6mm larger diameter) and 15/55 cam

Jets in my 32/36 carb were Primary- main 130,idle50,air 165
Secondary-main 140,idle 60, air 160

I attached the colortune to the number 1 spark plug hole and found, after warming the engine, that it was colored light blue at idle. Meaning the mixture screw needed turning out anti clockwise until a Bunsen Burner blue color was achieved. Having done that I turned the engine off and counted the turns the mixture screw was out....3.5 turns..wow!! An ideal number was 1.5- 2 turns which when the correct idle jet was installed (ie larger) this could be achieved.

So this now required for the primary idle jet to be changed to a larger jet to achieve 1.5-2 turns on the mixture screw. I ended up with 65 as my primary idle jet and 1.7 turns out with that mixture screw. This gave me the mid blue color on the colortune device. At this stage the device has paid for itself IMO. Took the trike for a run,much more power and smooth as...

Reading the colortune guide it is not unusual to see yellow color from the device when under acceleration particularly fast revving due to the accelerator jet squirting fuel. So rich under those circumstances is ok. What I did, when the engine was idling was place a screwdriver on the secondary jet lever to see what color the device would be when that was revved without the primary throat opening more than idle. It went very yellow. = lean. I needed more air.

Next step I made the following changes- primary main from 130 to 140, primary air from 165 to 180, secondary main from 140 to 145, secondary air from 165 to 180.

So at the end of the task I ended up with-

Primary- Main jet 140, idle 65, air 180. This gave a rich blue color with the colortune from idle right up to 3000 rpm. Very happy with these jet sizes.

Secondary- main jet 145, idle 60, air 180. This gave good revving result with rich blue on the device when revved over 3500 rpm after the yellow color went away after accelerator jet finished operating...only 2 seconds.

Test ride. Wow, never had this performance with the 38/38. No hesitation, not surging etc. Really nice. Then WOT, very good, the engine howls. I'm of the opinion however that the secondary mains could be raised from 140 to 155 or 160- even 165. Would I need a larger air jet as well to do this (is 180)? It just lacks a little at top end. Not much though.

I'm going to leave it now for a few runs to see how it impacts overall. I'm also of the view that the SPFI manifold might well be allowing a performance advantage now. That's how it feels. Means jets sizes from others I've read about might well be on the small side for this engine.

What are your thoughts? Tony

Post by **TOONGA** » Thu Jul 30, 2015 7:14 pm

Nice write up Tony it made me curious, so I went to youtube and found this video.

What did the colour tune cost?

TOONGA

https://www.youtube.com/watch?v=Y9t8XhFlKbk

Tweety · Post by **Tweety** » Thu Jul 30, 2015 7:28 pm

Hi Jules,

Ebay $104 free delivery. all are around that mark. Got mine from SA I think.

I used your jet sizes as well as several others. Did a lot of reading over the last few weeks. Also read up on jets for similar sized engines like the BMW 2002 Escorts etc etc. Just to get an idea. We know that changes to primary jets can effect secondary jets etc. So it really is an art and an art I'm willing to become knowledgeable about.

The fact that 65 on the idle jet is so high tells me that something if working well in my engine. Either the high compression (better combustion?) or larger manifold (but the entry into the heads is the same? is a mystery.

And because of this factor I'm wondering if the same effect would be on the secondary jetting also. EG instead of going 145 on the secondary mains and 180 in the Air, perhaps I can go 160-170 in the mains and get the full benefit of this near new engine.

This is the only area I'm wondering on.

The colortune is really good and easy to use. It takes the guesswork out of things. I mean I was 1.5 turns in from where the mixture screw should have been on the original jetting. 3.5 turns out told me immediately I had the wrong jet in the idle primary. That is a very good start to jetting. To jet that primary idle correct so you get 1.5-2 turns out from all the way in.

The colortune device when it shows yellow at low revs is easy to see. Then screw in the mixture and as soon as the yellow disappears and turns a mid Bunsen burner blue that's it. No point going further as the blue turns a lighter blue and is too rich.

But the secondary jets is more guesswork than that.

tambox · Post by **tambox** » Thu Jul 30, 2015 8:42 pm

Out of interest, tried it in all the plug holes or just No1?

Tweety · Post by **Tweety** » Thu Jul 30, 2015 8:52 pm

arhhh, Greg, you read my mind. I thought of it but I'm going away for 3 days and time ran out.

I cant see it being any diferent but you never know.

When I tackle the last of the adjustments eg the secondary main jet (larger) I'll swap plugs and see if all are the same.

Silverbullet · Post by **Silverbullet** » Thu Jul 30, 2015 9:22 pm

Wow!

Never even knew a device like this existed even though research tells me it's been around for donkeys years...and for $100 or less why aren't we all using this with our Weber 32/36's?

Nice writeup Tweety, it seems too good to be true that it would be this easy to tune a carbie engine. I think I'm going to have to get one now! How long did it take from starting out, fiddling with swapping jets over to the final result? How many new float bowl gasket do you go through?

Tweety · Post by **Tweety** » Thu Jul 30, 2015 9:39 pm

When I got this second hand but very good condition carbie I ordered the top and bottom gasket. I didn't damage the top one on this exercise. The float had been previously set correctly (38mm) as it had come off an ea82 anyway.

All up from the time I sat down at the rear of the trike to the end of the last test run- 90 minutes.

The procedure was running in my head a lot prior to today. eg

I already knew that the idles and mains were likely too small judging from other threads on www. I didn't think they'd be that much too small though. As I said there must be a reason for this - manifold size or CR.

To figure out it quickly the primary jet was way too small gave me confidence. Once that was done the correct blue flame continued all through the rev range of the primary only jet. But I also read that the secondary idle jet has some influence on the transition from primary to secondary operation. So logic told me (which is questionable) that if the primary jets are larger than commonly used for this engine due to manifold size or CR then the others might need to be also.???? and so I continued along that path.

My worry was that I'd end up with hesitation or surging when cruising etc.

Of course the secondary Main jet is my concern and you cant ride around with both jets open so often that the spark plug colour with give you an indication if its too rich or lean. Hence sticking with riding for a week or three and climbing a few hills and see how it goes.
Its not the be all and end all but it could easily save you a few dynoes and something to add to your tool chest.

Silverbullet · Post by **Silverbullet** » Thu Jul 30, 2015 10:01 pm

It seems like the sort of thing I would be quite confident doing, and since I don't think the Weber on my ute is quite right I probably will end up doing

Will come in handy when tuning those two carbs on the wagon as well...whenever that will be

With the secondary mains; I guess you can't really get an accurate measure with this device and just forcing the secondary open on its own? You mentioned you did similar somewhere in there, but say you had yellow = lean needing more air? I thought that yellow would have been rich, needing more air or less fuel.

Probably not recommended to blast around the hills with this thing connected, mirror scope sticking out through the bonnet?

Maybe a bit harder to see in your case.

tambox · Post by **tambox** » Thu Jul 30, 2015 10:02 pm

How do you read it whilst riding?

Tweety · Post by **Tweety** » Thu Jul 30, 2015 10:03 pm

Prior to today I'd tuned the mixture screw by er. You know, turn it in till it splutters a bit then half a turn out. That was. But in reality that adjustment was for a jet too small. Adjusting the mixture with a jet too small is only part of the picture. This tool opens the picture far wider. By knowing the ideal point -1.5 to 2 turns out gives you an idea of how out of range your prim idle jet really is. So just over 2 turns say 2.25 turns to 3.5 turns to where the colortune told me its fuel/air mix was good was a wake up call. From 50 on the prim idle to 55 then 60 and I was slowly screwing in the mixture...then 65 before it went beyond the two turns out. I haven't read anywhere that a e81/2 has 65 on the primary idle jet.

Tweety · Post by **Tweety** » Thu Jul 30, 2015 10:08 pm

you dont read it whilst riding Greg. Mainly stationary. I could leave it on and use the mirror extension and get Debbie to ride it and me look at it from the passenger seat. No, usually it isn't for that purpose. I suppose a usb camera with extension lead would be ideal. memories form the SPFI days Greg. pity you didn't see much countryside that day lol

Silverbullet, think I got the colours mixed up there. All I remember is that the larger jets were needed.

Tweety · Post by **Tweety** » Thu Jul 30, 2015 10:09 pm

My VW trike mates are using it on their twin carbie set ups 1916cc with great success.

Tweety · Post by **Tweety** » Thu Jul 30, 2015 10:20 pm

So Tambox, you mean under load it will be different. how much different I wonder?

I think, as a guess, the primary jetting can be adjusted better than anything apart from a dyno but I have reservations with the secondary circuit.

One can go by others secondary jetting and go from there?

Tweety · Post by **Tweety** » Thu Jul 30, 2015 10:30 pm

I've got this topic on USMB.

A ea82 owner has on his secondary the same jets as me but 162 on the main. Same air and idle jets. So think I can go larger with that as see how it goes.

Post by **Bantum** » Thu Jul 30, 2015 10:52 pm

Like the simple methods, will have to get one for the tool box.
I wonder what the clear material is made of ?

Cheers, Bantum ...

Tweety · Post by **Tweety** » Thu Jul 30, 2015 10:57 pm

looks like glass. for ea series you need to order the 14mm one.

Tweety · Post by **Tweety** » Thu Jul 30, 2015 11:09 pm

Even if this device gets the jetting in the ball park. Think a quick dyno and assessment would get a result i.e. "yes you can go one up or one down on the mains etc. " to satisfy that under load criteria.

tambox · Post by **tambox** » Fri Jul 31, 2015 7:41 am

Sorry Tony, I've lost track of the carbie swaps.
Do you have this carbie dynoed or just the other one?
Your going in fairly bit jet steps when you are changing them.
Because you have changed many of the jets, these will all interact with each other, hopefully getting the whole lot in the ball park.
Interesting to see what happens to your fuel economy.

Subydoug · Post by **Subydoug** » Fri Jul 31, 2015 8:46 am

Interesting device, Nice one Tweety. I always found with my motor that it likes to idle rich. I have a wideband in it so I could see the mixture but I always tuned for the best manifold vacuum which was around the 13-1 range. Mixture will most definitely be different under load.

Regards

Doug

Tweety · Post by **Tweety** » Fri Jul 31, 2015 8:48 am

When I recoed the engine early this year the first carb was a new 38/38 synchronic. It did prove too big.

My dyno man (with the 38 ) had trouble tuning it to run good ie not hiccups on slow bends etc. Economy wasn't good IMO at 20-23 mpg light foot.(hand)

The 32/36 was sort after and I bought a good s/hand one. No wear anywhere.

There are some variables. My 32/36 doesn't have a choke. This results in a little less restriction in the throats. The larger size manifold 6mm diameter could be as much as double the internal volume. I can only see that as a positive. Good flowing ramflow filter.The heads were ported a little by the engine builder but he said "nothing to get excited about". He had good knowledge of the engine and had recoed a few in his time for aircraft.

Stock issue from redline for the 32/36 for an ea81 is-

Stock from Redline for the Subaru is on the left, mine on the right:

Primary Main: 140 .....................140
Secondary Main: 140 .................145
Primary Air: 170 ........................ 180
Secondary Air: 160 ..................... 180
Primary Idle: 50 ............................65
Secondary Idle: 55 ...................... 60

Emulsion tubes were untouched as recommended "everywhere".

At one stage I had 155 in the secondary main. It was rich. So went the 145. Then I read last night that being a little rich on the secondary circuit isn't bad at all. I think I'll go back to the 155 main sec and see how it performs.

Economy will be interesting. In this cold weather riding isn't being done much to find out.