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I like the idea of running a down draft Weber 38 dges on your auto 2.2L.

Heck I mentioned that when you first posted how much trouble you were having with your dual side drafts.

The Weber 38 dges are wonderful carburetors. And as you mentioned, your previous experience with yours was very positive
 

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Opel Rallier since 1977
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There is nothing in the DCOE's, except if they happen to be oversized, that will hold you back from getting the desired response like you had before. But if you have a 2.2 engine, those do not seem to be oversized. From your description, it sounds like you are having leaning out of the mixture in several modes.

The off-idle response being lacking is from what Knorm65 discusses: a match of idle bleeds and jets, and the emulsion tubes, needs to be changed out. Been through this years ago on a 1.6L Mitsubishi rally engine. Just had to try and try, and read plugs, and try some more, and we finally got it all sorted out, and the engine was great after that; great torque from 2500 RPM to 6500 RPM. Finding the right emulsion tubes were the big key; they have a lot of control fuel mixture as you transition through off idle.

But it takes:
  • time and effort
  • some learning to understand what is doing what as far as the different parts effect different modes
  • some way to read the mixture (an AFR meter is far easier than learning to read plugs, which has become harder with the newer fuels)
  • maybe hundreds of $$ in tuning parts; a better combination to try based on the experience of others may short cut some of this cost
So they may not be the best if you are frustrated and not ready for the learning mode and parts cost.
 

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Do you have your choke cable cable connected ? When your driving and hit the "bog area" pull your choke out some to see if your "bog" is corrected then you know it's running lean.
This should be a quick way to see what might help.
 

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Have you considered installing a wide band air/fuel/ratio (AFR) sensor and gauge? Kyler has been a big proponent, and now that I have one to assist in jetting my 38 DGES, I am convinced that jetting a carb without an AFR is pretty damn hard, bordering on silly. They cost under $200 for the full kit, are quite easy to install, and if you decide to leap into a smart EFI, you are locked and loaded.

That suggestion applies no matter if you stay w/ the DCOE's or go back to the 38 DGAS.

My experience has been that, while it is helpful to have a starting position for jets and air correctors etc, the only way to properly tune a carb across the operating range is to actually SEE the AFR under various conditions (rpm, load, throttle position, etc) and then make systematic changes to determine the effect, and improve the results.

Here are two photos of when I was doing some simple checking while I was still stuck in my garage. Since I have been able to get the car on the road, I have made a dozen changes, in step-wise form, of pump jets, main jets, idle jets and air correctors. Without being able to see what changes, that would have been simply impossible.

And as a comment, while reading spark plugs for general mixture is useful, it is totally useless for specific issues such as mid-range bog, off-idle transition, etc etc, etc....

JM2CW
 

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Opel Rallier since 1977
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1,455 Posts
An AFR meter indeed sure makes life easier. They are reasonably accurate. Not accurate when the engine is not warmed up however.

I like the Innovate ones. You don't have to install it permanently; just put the gauge in the cab where you can see it. I can move mine from car to car; just needs an O2 sensor bung welded into the side of the exhaust pipe.

IMHO, you aren't totally blind without this. Emulsion tubes description are well published in the Weber tuning manuals that give you a general idea which will do what. And there are good seat-of-the pants symptoms that you can easily learn to know if you are lean in particular. I've been tuning up a '75 Opel FI system just by symptoms like how it responds to various throttle positions, and even the smell of the exhaust at idle.
 

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The biggest issue with DCOE’s, especially on a GT, is intake runner length.

I ran some 40 DCOE’s on a Manta (with automatic) years ago. Prior to that I had a 38 DGAS on a ported intake.

It felt very strong with the DGAS, but with the DCOE’s and short Irmscher intakes, it felt very slow off the line. I documented the 0-30, 0-60, 0-100 mph, and top speeds.

My butt dyno proved correct, as it was slower from 0-30 compared to the DGAS. It was 2/10ths quicker to 60 mph. It was however about 8 seconds faster to 100 mph. Top speed was 118 with the DGAS, but I had it to 130 mph with the twin DCOE’s and it was still accelerating somewhat.

I think with long runners and air horns it would’ve all worked out. But short runners favor top end power, regardless of venturi size.
 

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Opeler
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Discussion Starter #88
First of all, thanks for all the responses on this, I truly do appreciate them. Before I respond to each of the posts, I have another question:

Is the carb choice (I know it still needs fine tuned) giving me the lack of what I was used to (I.e. torque) or is the cam choice (specs: intake duration 222 w .455 lift, exhaust duration 228 w/ .448 lift, lobe separation of 112) factor?

I like the idea of running a down draft Weber 38 dges on your auto 2.2L.

Heck I mentioned that when you first posted how much trouble you were having with your dual side drafts.

The Weber 38 dges are wonderful carburetors. And as you mentioned, your previous experience with yours was very positive
I know, and I’ve really been deliberating that in the past month or so.

There is nothing in the DCOE's, except if they happen to be oversized, that will hold you back from getting the desired response like you had before. But if you have a 2.2 engine, those do not seem to be oversized. From your description, it sounds like you are having leaning out of the mixture in several modes.

The off-idle response being lacking is from what Knorm65 discusses: a match of idle bleeds and jets, and the emulsion tubes, needs to be changed out. Been through this years ago on a 1.6L Mitsubishi rally engine. Just had to try and try, and read plugs, and try some more, and we finally got it all sorted out, and the engine was great after that; great torque from 2500 RPM to 6500 RPM. Finding the right emulsion tubes were the big key; they have a lot of control fuel mixture as you transition through off idle.

But it takes:
  • time and effort
  • some learning to understand what is doing what as far as the different parts effect different modes
  • some way to read the mixture (an AFR meter is far easier than learning to read plugs, which has become harder with the newer fuels)
  • maybe hundreds of $$ in tuning parts; a better combination to try based on the experience of others may short cut some of this cost
So they may not be the best if you are frustrated and not ready for the learning mode and parts cost.
I’m starting to hit a point that I’m not sure if the money I’m spending to get my desired result is all that worth it. Especially if my chance of achieving what I want (use to have) isn’t all thag

Do you have your choke cable cable connected ? When your driving and hit the "bog area" pull your choke out some to see if your "bog" is corrected then you know it's running lean.
This should be a quick way to see what might help.
No choke on my carbs, so that isn’t an applicable option.

Have you considered installing a wide band air/fuel/ratio (AFR) sensor and gauge? Kyler has been a big proponent, and now that I have one to assist in jetting my 38 DGES, I am convinced that jetting a carb without an AFR is pretty damn hard, bordering on silly. They cost under $200 for the full kit, are quite easy to install, and if you decide to leap into a smart EFI, you are locked and loaded.

That suggestion applies no matter if you stay w/ the DCOE's or go back to the 38 DGAS.

My experience has been that, while it is helpful to have a starting position for jets and air correctors etc, the only way to properly tune a carb across the operating range is to actually SEE the AFR under various conditions (rpm, load, throttle position, etc) and then make systematic changes to determine the effect, and improve the results.

Here are two photos of when I was doing some simple checking while I was still stuck in my garage. Since I have been able to get the car on the road, I have made a dozen changes, in step-wise form, of pump jets, main jets, idle jets and air correctors. Without being able to see what changes, that would have been simply impossible.

And as a comment, while reading spark plugs for general mixture is useful, it is totally useless for specific issues such as mid-range bog, off-idle transition, etc etc, etc....

JM2CW
I have been looking in to an AFR over the mast two weeks, as I do think it would help with the tuning, both now and for later should I decide to go another route.

If you ditch the 45s I may be interested in buying them.
If I do, you’ll have dibs in m


The biggest issue with DCOE’s, especially on a GT, is intake runner length.

I ran some 40 DCOE’s on a Manta (with automatic) years ago. Prior to that I had a 38 DGAS on a ported intake.

It felt very strong with the DGAS, but with the DCOE’s and short Irmscher intakes, it felt very slow off the line. I documented the 0-30, 0-60, 0-100 mph, and top speeds.

My butt dyno proved correct, as it was slower from 0-30 compared to the DGAS. It was 2/10ths quicker to 60 mph. It was however about 8 seconds faster to 100 mph. Top speed was 118 with the DGAS, but I had it to 130 mph with the twin DCOE’s and it was still accelerating somewhat.

I think with long runners and air horns it would’ve all worked out. But short runners favor top end power, regardless of venturi size.
I didn’t go with the really short intakes, I ordered a pair of slightly longer ones (but it near the Cannon length) from Risse Motorsport in Germany to help provide a slightly longer runner length to help with torque. I want off the line power, and up to speed limit quickness; going to 100+ or more isn’t happening for me.

I’m all ears to any other suggestions or comments. I’m going to dive in to my Weber book again to see what I can try next.

Thanks again

Eric
 

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Can Opeler
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3,260 Posts
I forgot what chokes you have in it now. Since you aren’t concerned with high rpm power as much try 30mm or 32mm. I bet you’ll be happy but you will have to retune.

I have mine set up more for midrange power. Mine will hesitate if I slam the throttle but so will nearly every other carbureted car that isn’t severely under flowing. I can still do a burnout and launch etc, it just takes throttle control.

The smaller chokes will get you a lot more oomph down low if you try that.

Also it might be your cam. If you went with a hotter cam the chance of you getting the get up and go on the low end that you had with a stock cam ain’t gonna happen. You can still tune for it, but it’s not the same.

Lastly are you sure on your timing? My Opel likes nearly 15° initial advance to accelerate nicely with a DCOE. I’ve compromised with 12° initial though to get my high rpm advance where I want it. My advanced curve hits hard above idle and really helps.

You have that fancy new tunable distributor don’t you? Give yourself a generous amount timing at say 1800rpm. I’m already at around 25° at 1800, try 30° for kicks. If it pings drop it until it doesn’t. Go for 36° max at about 2800rpm or heck shoot that girl up to 50° and drop it down 36° before 5000.

Here’s the curve on one of my cars. I think I bumped up my max the 34° but I can’t remember.
 

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Opeler
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759 Posts
Discussion Starter #90 (Edited)
I forgot what chokes you have in it now. Since you aren’t concerned with high rpm power as much try 30mm or 32mm. I bet you’ll be happy but you will have to retune.

I have mine set up more for midrange power. Mine will hesitate if I slam the throttle but so will nearly every other carbureted car that isn’t severely under flowing. I can still do a burnout and launch etc, it just takes throttle control.

The smaller chokes will get you a lot more oomph down low if you try that.

Also it might be your cam. If you went with a hotter cam the chance of you getting the get up and go on the low end that you had with a stock cam ain’t gonna happen. You can still tune for it, but it’s not the same.

Lastly are you sure on your timing? My Opel likes nearly 15° initial advance to accelerate nicely with a DCOE. I’ve compromised with 12° initial though to get my high rpm advance where I want it. My advanced curve hits hard above idle and really helps.

You have that fancy new tunable distributor don’t you? Give yourself a generous amount timing at say 1800rpm. I’m already at around 25° at 1800, try 30° for kicks. If it pings drop it until it doesn’t. Go for 36° max at about 2800rpm or heck shoot that girl up to 50° and drop it down 36° before 5000.

Here’s the curve on one of my cars. I think I bumped up my max the 34° but I can’t remember.
I’m using 32mm chokes on my carbs currently.

And on the timing front, yep, I’ve got a totally digitally tuneable distributor that I can set the advance to be whatever I want it to be at any rpm from my app. Here’s what I’ve got it set up to be right now....

426900
 

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Opeler
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Too bad that you are discouraged. I am huge fan of DCOE carbs. I can testify that I didn't have any flat spots using them on 2.0 engine (2x40DCOE) and now on 2.5 (2x45DCOE). Hell, I even used them on 1.9 low compression engine.
True, DSD carbs are seldom bolt-on option. They require experienced butt-dyno or AFR assistance. Usually several sets of jets and emulsion tubes must be tried. Then, the device for proper balancing is a must. Poorly balanced DSDs will not work properly but once those carbs are set, they work for a long time without need for adjustments.
I only hope that your ignition is working properly. No carburetors tuning will help if there is something wrong with the ignition or the timing.
I am showing video of my GT acceleration, 5-speed Getrag, 3.44 differential. I didn't want to tear the drivetrain and tires, so I stomped on the gas at about 2500 rpm but I can assure you the same response is from idle rpm. Hope it will convince you to stay with DSDs.
 

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Opeler
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759 Posts
Discussion Starter #92
Too bad that you are discouraged. I am huge fan of DCOE carbs. I can testify that I didn't have any flat spots using them on 2.0 engine (2x40DCOE) and now on 2.5 (2x45DCOE). Hell, I even used them on 1.9 low compression engine.
True, DSD carbs are seldom bolt-on option. They require experienced butt-dyno or AFR assistance. Usually several sets of jets and emulsion tubes must be tried. Then, the device for proper balancing is a must. Poorly balanced DSDs will not work properly but once those carbs are set, they work for a long time without need for adjustments.
I only hope that your ignition is working properly. No carburetors tuning will help if there is something wrong with the ignition or the timing.
I am showing video of my GT acceleration, 5-speed Getrag, 3.44 differential. I didn't want to tear the drivetrain and tires, so I stomped on the gas at about 2500 rpm but I can assure you the same response is from idle rpm. Hope it will convince you to stay with DSDs.
Discouraged is probably the best way way to say it PJ. I’m not giving up on them, but I am being realistic about trying to uncover if I can achieve my goals. If I can achieve my desired results, then I’m going to stick with. There are 3 things that I need to get figured out:

1) Starting the car easier
2) Power/torque from idle
3) Fitting an air-box & air filter

If I can figure those items out, assuming my current carb & cam can achieve those results, then I’m good to go.

I’m all ears and willing to learn to tackle this.
 

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Opeler
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861 Posts
Your really need to invest in a AFR meter. Once you get it close then you can use seat of your pants. I don’t agree with smaller chokes, but whatever works. I have a similar build 2.2 but my cam has more duration. I’m using 36 mm chokes and have no flat spots, I can stomp on the pedal with no stumble. Everybody’s setup is going to be different and if you keep listening to different suggestions without getting some AFR numbers you’re going to keep chasing your tail. Once you get it close then you can start fine tuning it for where you want the power. I would suggest in also investing in a set of jet drill bits, buying jets four at time while you’re experimenting will get expensive. OH, and you HAVE to be sure the carbs are balanced, as said before. There’s no getting them close and there’s no seat of your pants either.
 

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Can Opeler
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Opeler
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Discussion Starter #95
Your really need to invest in a AFR meter. Once you get it close then you can use seat of your pants. I don’t agree with smaller chokes, but whatever works. I have a similar build 2.2 but my cam has more duration. I’m using 36 mm chokes and have no flat spots, I can stomp on the pedal with no stumble. Everybody’s setup is going to be different and if you keep listening to different suggestions without getting some AFR numbers you’re going to keep chasing your tail. Once you get it close then you can start fine tuning it for where you want the power. I would suggest in also investing in a set of jet drill bits, buying jets four at time while you’re experimenting will get expensive. OH, and you HAVE to be sure the carbs are balanced, as said before. There’s no getting them close and there’s no seat of your pants either.
I’m on the hunt for one. May be a delay in installation with everything going on right now, and I don’t weld. Any brand/unit recommendations?

I’ve really been picky on getting the carbs balanced. I haven’t tried to change jets again, because I until I get them perfectly balanced, it’s pointless.

If we have a similar build and 2.2 engines, I’m curious to know what jets you’ve got in your carbs...manual or auto trans?

1. Starting easier: install the choke. I’ve never understood why people skip this step. I use my manual choke lever everytime.

2. Tuning. Also get an AFR gauge.

3. Air filter. Carburetor AIR FILTER 75mm 3" RAMAIR foam Weber DCOE Solex ADDHE Dellorto DHLA | eBay I like these a lot. They will smash to fit where you need them. If you get the angled air horns a lot of the euro guys use you can fit more filters.
The choke, that’s another item on the list. You’re talking about this right?

426903


What AFR do you recommend?

Thanks for the link on a filter. I’ve got an airbox to use, I just have to get creative on how to install air horns and still get the air box installed. I may need shorter air horns. I’ve considered angled air horns, but again the cost of them is absurd. I’ve contemplated seeing if a motorcycle or muffler shop could fab some up since overall length from (runners+carb+manifold) to head is supposed to effect torque curve. However if I can’t get things to work out, then I’d have to go the filter route.

Thanks again.

Eric
 

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Opel Rallier since 1977
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JHJ, looking at your long post above, DID you change the cam at the same time as the carbs? I am not clear on that part. If you went with a larger cam than before, then that is almost certainly a contributor to the loss of lower RPM torque.

Your cam specs listed above don't look terribly radical, but they are not mild either. What cam is this new one, and what cam did you have before? (And IDK your pistons and all to work out the dynamic compression ratio, but let's start with the cam.) Be aware that if you did not time the cam, and its timing is retarded, then that will hurt the low RPM torque. IIRC, your cranking compression numbers were quite high (very high for pump fuel IMHO but that is another story); high cranking compression numbers typically will mean good low RPM torque; so that is conflicting with the info on cam size....

Yes on the cold-start choke. If you want easier starting, that is a no-brainer. Otherwise, you can pump the accelerator pedal a lot while warming up to push more fuel into the engine via the accelerator pumps.... but I suspect that is what you are trying to avoid.
 

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Opel Rallier since 1977
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1,455 Posts
Here is the AFR gauge that I like; straightforward.

Remember: they are not accurate when the engine is warming up; they will read lean when the reality is otherwise.

I canot rceall if this kit had the bung for the exhaust; I think it did. If you do not weld, you might be able to get it to stick with this:
Metal Repair, High Temp, Dark Gray, 3 Oz!
You can find that at auto parts stores.

Or a muffler shop can put the bung in the exhaust pipe in for you. Put it downstream from where all 4 pipes join.
 

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Opeler
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759 Posts
Discussion Starter #98
JHJ, looking at your long post above, DID you change the cam at the same time as the carbs? I am not clear on that part. If you went with a larger cam than before, then that is almost certainly a contributor to the loss of lower RPM torque.

Your cam specs listed above don't look terribly radical, but they are not mild either. What cam is this new one, and what cam did you have before? (And IDK your pistons and all to work out the dynamic compression ratio, but let's start with the cam.) Be aware that if you did not time the cam, and its timing is retarded, then that will hurt the low RPM torque. IIRC, your cranking compression numbers were quite high (very high for pump fuel IMHO but that is another story); high cranking compression numbers typically will mean good low RPM torque; so that is conflicting with the info on cam size....

Yes on the cold-start choke. If you want easier starting, that is a no-brainer. Otherwise, you can pump the accelerator pedal a lot while warming up to push more fuel into the engine via the accelerator pumps.... but I suspect that is what you are trying to avoid.
The cam I listed in a previous post is the cam I put in the car when the motor was rebuilt. Prior to that, it was a stock 2.2 cam. The 45 DCOEs went on the car at the same time. Compression readings are across all cylinders

Here is the AFR gauge that I like; straightforward.

Remember: they are not accurate when the engine is warming up; they will read lean when the reality is otherwise.

I canot rceall if this kit had the bung for the exhaust; I think it did. If you do not weld, you might be able to get it to stick with this:
Metal Repair, High Temp, Dark Gray, 3 Oz!
You can find that at auto parts stores.

Or a muffler shop can put the bung in the exhaust pipe in for you. Put it downstream from where all 4 pipes join.
Thanks for that, I appreciate it.
 

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Can Opeler
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3,260 Posts

Also here is the cheapest and best Afr gauge on the market IMO

AEM (30-4110) UEGO Air/Fuel Ratio Gauge https://www.amazon.com/dp/B00N3VGPYS/ref=cm_sw_r_cp_api_i_gKtXEbXEMHD2X
 

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Opeler
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861 Posts
First, I'm not clear what you mean that you're "trying" to get the carbs perfectly balanced. How are you balancing them? Once properly balanced, they shouldn't need adjustment for quite a while unless you change the placement of one of the carbs, e.g. removal and reinstall.

Second, I don't like suggesting a particular setup because every engine will respond differently, but since you asked......Manual transmission, Jets: 145 Mains, 190 Air Corrector, F8 65 Idle, 50 Pump. 0 Exhaust Bleed (I think). I think the last standard emulsion tubes I was using were F16, I'm using some customer made tubes now. I don't use the cold start circuit. I have an electric fuel pump and let that run for few seconds, then pump the pedal 3-4 times when cold, and it starts immediately. I'm using a Compu-Fire ignition. I'm very intrigued by the ignition you bought but I like NOT having a cap and rotor too much. I'm probably running a little rich and need to put the AFR meter on again, I've made some recent changes.
 
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