Weber jets??All who live for their triples please read this

[steve260z]

If anyone needs 40 pump jets here is a good deal:

 

http://www.ebay.com/itm/WEBER-DCOE-PUMP-JETS-SIZE-40-SIX-GOOD-USED-/151066901452?pt=Motors_Car_Truck_Parts_Accessories&hash=item232c49fbcc&vxp=mtr

[AZGhost623]

Has anyone tried the "colortune" product for tuning each cylinder with their webers? Concept sounds good, but not sure how well it works in all practicality. Anyone have experience with this? With our webers it looks like you may only get part of the fuel delivery circuit tho since this is done at idle. 

 

http://www.youtube.com/watch?v=xEZ0-uN0NA4

Edited July 4, 2013 by AZGhost623

[Leon]

Has anyone tried the "colortune" product for tuning each cylinder with their webers? Concept sounds good, but not sure how well it works in all practicality. Anyone have experience with this? With our webers it looks like you may only get part of the fuel delivery circuit tho since this is done at idle. 

 

http://www.youtube.com/watch?v=xEZ0-uN0NA4

 

Don't waste your money. You have a wideband already which is WAY ahead of what a colortune can do.

[AZGhost623]

Don't waste your money. You have a wideband already which is WAY ahead of what a colortune can do.

 

I kinda thought that too, but the thing I found interesting about the colortune was that it was per cylinder, where the wideband is overall for the entire system. I found another vid of a guy using it on his 260, but it also has SU's.

 

Edited July 5, 2013 by AZGhost623

[Ricksilvia]

ok so i have a 83' 280zx fitted with some old weber dcoe 42 8s on a cannon manifold. holley red fuel pump 3psi pressure with a return line unregulated. heres my issue: i checked my timing tonight with an inductive timing light just to see what was going on down there {gigity} and @1000rpm shes at about 30* initial, and @3000rpm shes somewhere like 45* if i rotate the distributer in the retarded direction i get pops and bursts of flaming hell fire out of my air horns??  Im Rick hello all

[T-Bone028]

I think you need to verify TDC and re-mark for 0...if you search a bit, some folks have seen similar issues with timing marks being off.

[Leon]

I kinda thought that too, but the thing I found interesting about the colortune was that it was per cylinder, where the wideband is overall for the entire system. I found another vid of a guy using it on his 260, but it also has SU's.

 

 

Sure, it's fun to play with but it's just not a very precise tool. If you're that concerned about cylinder-to-cylinder variations, get 6 EGT probes or better yet, 6 widebands...

[Lazeum]

I'm trying to understand on my setup, why I do have a lean spot at high rpm. As rpm go up, AFR become leaner.

I've got 40DCOE with 32mm choke & mallory 4070lp pump.

Engine is F54 with P79 ported/polished by Braap with "street tight lash" Rebello cam

 

Mallory pump for some reason is not able to deliver more than 2 psi of pressure which is fairly low. Flow is good, lean spot happens at 2nd or 3rd gear (4th & 5th are too high for open roads test). I suffered no fuel starvation on highway being at WOT on 4th gear.

 

So I suspected 2 causes:

- Too small chokes

- Too small fuel pressure

 

So I've switched the fuel pump with a Carter unit at 3psi. It didn't solve my problem but AFR readings allow me to show how fuel pressure (hence fuel bowl level) could impact AFR. It is very significant.

Lesson learned: fuel level is very important, so fuel pressure. It makes no sense to compare settings between cars if fuel pressure is not documented.

 

On the following chart, carb settings hasn't been changed at all.

 

Edited October 9, 2013 by Lazeum

[T-Bone028]

Lazeum, that would definitely concern me going that lean at what appears to be 5800-6000 rpm. I don't believe it is necessarily related to main Venturi size though...32 mm main venturi should run richer than a 36 mm main venturi if mains and airs are unchanged. what is your main, air, and etube? I know this may not be the correct way to do it, but decreasing the size of your airs should make you slightly richer on the top end.

 

I'm sure Leon could chime in on some of Keith Francks designs that might address your issue...

 

I believe you are running mega jolt correct? What is your timing in that range?

 

Do you run a fuel return line and/or a fuel pressure regulator? I believe the carter unit suggests that it is internally regulated, but I wonder if you would see more consistency with a FPR after the last carb in a system with a fuel return line.

 

Just spit-balling over here.

[Leon]

I'm trying to understand on my setup, why I do have a lean spot at high rpm. As rpm go up, AFR become leaner.

I've got 40DCOE with 32mm choke & mallory 4070lp pump.

Engine is F54 with P79 ported/polished by Braap with "street tight lash" Rebello cam

 

Mallory pump for some reason is not able to deliver more than 2 psi of pressure which is fairly low. Flow is good, lean spot happens at 2nd or 3rd gear (4th & 5th are too high for open roads test). I suffered no fuel starvation on highway being at WOT on 4th gear.

 

So I suspected 2 causes:

- Too small chokes

- Too small fuel pressure

 

So I've switched the fuel pump with a Carter unit at 3psi. It didn't solve my problem but AFR readings allow me to show how fuel pressure (hence fuel bowl level) could impact AFR. It is very significant.

Lesson learned: fuel level is very important, so fuel pressure. It makes no sense to compare settings between cars if fuel pressure is not documented.

 

On the following chart, carb settings hasn't been changed at all.

 

 

Sounds like your e-tube is dumping too much air into your main circuit. Does your e-tube have holes above the fuel level? If so, plug those. You may need to play with your air jet as well.

[AZGhost623]

I'm trying to understand on my setup, why I do have a lean spot at high rpm. As rpm go up, AFR become leaner.

I've got 40DCOE with 32mm choke & mallory 4070lp pump. Engine is F54 with P79 ported/polished by Braap with "street tight lash" Rebello cam

 

AFR gets leaner because of more air being drawn in, interacting with your fuel supply at WOT. Your choke size can be ok, its doing just that choking down the air flow, you just have to match your jets to it, which from the sounds of it, something is too small or delivery isnt right (etubes). 

 

What are your settings on your main circuit for your carbs? Size Jets? Tubes? Air Correctors? I think the consensus is you want somewhere around 3psi for fuel pressure. Mine is dead on at 3psi with a Carter 4070 fuel pump.

Edited October 9, 2013 by AZGhost623

[Lazeum]

I'll extend a little bit my setup for some thoughts

 

First, I'm running a L28 with flat tops, P79 modified by Braap. CR is around 9.5:1.

Cam is a Rebello unit made for the street: lift is around 0.49", rev band should be 3000-6000rpm roughtly.

 

I'm indeed running megajolt system. At WOT I'm running 33° max timing for now.

I've tested timing at 35°, I did not feel any difference in performance, AFR were about the same. So I put timing out of the picture for lean AFR.

 

Lean AFR starts at 4500-5000rpm. I need to get rpm signal from Megajolt to be sure but it's in the ball park.

 

Regarding carb setup:

40DCOE-18

Chokes: 32mm

Aux chokes: 4.5"

Idle jet: 45f9

Accel jet: 45

Bleed jet: 0

Main: 120

Air: 165

etube: f11

Needle jet: 200

 

Fuel level on every carb has been set according to Weber manual with gages. So they are even.

 

Regarding root cause analysis:

- Issue did not exist with previous setup with previous head, stock N42. I was actually running too rich at high rpm.

- Air jet did not help much - I was running 180 before, lean spot was not impacted that much

- Main jet helped a little. Getting main jet bigger made the lean spot coming later.

- Fuel pump / fuel pressure did not change anything - So it is not a fuel starvation issue.

- There's no misfire or anything to believe timing is not OK. It is quite the opposite actually, engine performance has gone up tremendously with MJLJ system.

 

Difference between old N42 head and P79 is important. I had to lower every jet in my setup to get the engine running ok. P79 head is more efficient than N42 for sure.

 

etube could be the root cause but intake pressure at WOT should be at atmospheric pressure ideally.

Too small choke will make intake pressure lower, by increasing chokes, I would increase intake pressure at WOT (less restriction), I'll see what happen with choke change then.

 

Regarding Keith Frank's work, I'm following closely what he's doing. Obert Etube & gravity etube are very promising.

[Leon]

I've got Obert e-tubes and Hypojets in my orange car, and the fueling control as well as driveability has tremendously increased. Get yourself some 05 e-tubes and H28 Hypojets to start, I think Keith accepts returns in the unlikely case that you're disappointed. The nice thing is that if you want to change jetting, you can swap with Keith instead of buying more and more jets.

[Lazeum]

I got it but shipping between Keith and me would outweight the benefit of the swap for free, unfortunately.

If I would be in the US, it would make my life much easier. I would have got some etube from him for a while

 

I'm curious to see how chokes will affect AFR. I'll see from here what I could do.

I've got also some retired engineers responsible for the Alpine A110 program in Rallies back in the days who could probably help me locally with DCOE's.

I've got small problems (because car is still awesome to drive - with no AFR readings, I would not suspect any problem) but it is part also of my hobby to solve problems, so it's all good (I know you've made the same comments some time ago  )

Edited October 10, 2013 by Lazeum

[Leon]

I got it but shipping between Keith and me would outweight the benefit of the swap for free, unfortunately.

If I would be in the US, it would make my life much easier. I would have got some etube from him for a while

 

I'm curious to see how chokes will affect AFR. I'll see from here what I could do.

I've got also some retired engineers responsible for the Alpine A110 program in Rallies back in the days who could probably help me locally with DCOE's.

I've got small problems (because car is still awesome to drive - with no AFR readings, I would not suspect any problem) but it is part also of my hobby to solve problems, so it's all good (I know you've made the same comments some time ago  )

 

In your case, I'd try to at least plug some of those upper air holes in your e-tube. The F11 really sucks for DCOE applications, it was made for down-drafts where the fuel level is higher relative to the tube (as Keith has shown) so that the air holes are submerged. The Sidedraft site has some great suggestions for modifying Weber e-tubes, seemingly with the F7 (I believe?) being the best candidate. If you have access to Weber guys, I bet they'll have a nice collection of stock e-tubes that you can play around with.

 

I know what you mean about the problem solving, keep it up!

[Lazeum]

I'll put etube modification on my to do list then.

How would you plug the top holes? Wooden tooth pick? Copper wire?

I've got JB Weld also (but something inside my head is saying "no-"no")

 

There's a classic car event this coming WE in Le Bourget (where the Paris plane show occurs if you have heard about it), I'll ask around but people, even pros, are not as knowledgeable anymore about DCOE unfortunately. I'm usually the one explaining them how to tune DCOE for specific operation. 

Edited October 10, 2013 by Lazeum

[Leon]

Keith has recommended a toothpick before. I read on the side draft forum about guys using tips of zip-ties, Loctite, etc...

 

Well you're in Europe (and right next to Spain, assuming that's where the jets are being manufactured since the carbs are made there), so I'd imagine buying Weber jetting isn't difficult where you're at.

[Lazeum]

I'm buying them in UK I did not look for spannish source but I've never seen anything about Weber in Spain besides DCOE 151's & 152's.

 

Still it isn't cheap when you start having main jets from 115 to 145 for L6, same goes for air jet with 165, 180, 195, ditto for idle jets, etc.

 

Etube are definitely more expensive so I did not mess with them yet.

[Leon]

I'm buying them in UK I did not look for spannish source but I've never seen anything about Weber in Spain besides DCOE 151's & 152's.

 

Still it isn't cheap when you start having main jets from 115 to 145 for L6, same goes for air jet with 165, 180, 195, ditto for idle jets, etc.

 

Etube are definitely more expensive so I did not mess with them yet.

 

That's exactly why I went to Keith's jetting, considering he was local. Not only did the car run better, but it's cheaper for me in the long run as I don't need a library of jets (although I managed to make a small collection at this point anyway ). I saved on idle-jets and e-tubes at least...

 

Playing with these things is definitely not for the feint of heart.

Edited October 10, 2013 by Leon

[Lazeum]

I've tuned last week a stock L28: N42 block, P90 head, dished pistons, stock cam

It has 40DCOE 22-23 & 6-1 headers with 2.5" exhaust system.

 

Car was previously tuned with 34mm chokes, good transition, AFR in 14:1 range at steady state, 12.5:1 at WOT.

Carb setup was:

idle: 45f9

Main: 135

Air: 170

etube: F7

 

We have changed to 32mm chokes, Car reactivity/power at WOT is better, car feels more powerful which is good at WOT.

Problem is the car was pig rich at cruising speed. WBO2 measured AFR at cruise at 10:1 !!!!! 

We did not have anything smaller than 45 with __f9 idle so we've switched to 55f8 to get AFR at 14:1 at cruise but transition is now very poor, engine sputters with low throttle input.

 

Something is not right to me & I'm not sure it is carbs related.

First I though choke size would not impact much AFR with idle jet whereas it has changed it by 4 points.

Secondly, I don't think stock L28 with 40DCOE and 45f9 should be that rich.

 

I drove the car (280zx) and I did not think power was high (comparison point is my tuned L28 in my 240z with Megajolt, so I might not be very objective) Owner is also having a Ford Capri with a V6 2.8L, single carb which is more powerful also.

Do you think problem could come from timing? Apparently it was check to be 34° max and around 10° at idle. I haven't checked it that day

Do you think we should check something else?

Edited October 19, 2013 by Lazeum