243 replies to this topic

[LC-GTR-1969]

What AFR are you getting from idle through to say 4000rpm now with the new etubes?

 

Can you log the following data here- under load not in the shed..

 

AFR at the following;

1000rpm

1500rpm

2000rpm

2500rpm

3000rpm

3500rpm

4000rpm

 

Log the data and shoot back. 

 

This is more for collaborative learning and analysis though..

 

Please don't spend any more money on the carbs until you have bought some new chokes- id go with 34 and 4.5 Auxiliaries. I fear you will spend a lot of time and make very little improvements until the chokes are changed- the large chokes will cause issues with any combination (whether it be F2 emulsions or VF emulsions- air speed is air speed and you wont have any under 5000rpm)... The VF tubes will likely be fantastic but I dont personally see much advantage tuning the car to the VFs when you are still running chokes that wont work with either tubes very well.

 

I am just worried that you will spend a lot of money on new jets to suit the 40mm chokes, only to change the 40s to smaller chokes in a months time as you will never obtain good tractability running oversized chokes. If you buy more jets to suit the 40mm chokes they will not likely be able to be used when you go down in choke size (hence I fear you could be throwing money away). 

 

If you are adamant you want to try to get it right with the 40mm chokes, please buy a soldering iron and jet drills so you can solder up and re-drill for testing purposes. 

Edited by LC-GTR-1969, 02 December 2017 - 05:08 PM.

[jd lj]

Changing the emulsion tubes is just one piece of the puzzle and not a lone magical cure. The idle circuit will also need to be adjusted to provide a seamless transition from the idle circuit to the main circuit. Your manifold vacuum level is rather low and should be tuned accordingly by using idle jets with a larger diameter internal bore. To be honest I can't say that I've tried this myself but I have faith in my source of information due to the extremely thorough and persistent testing that has been carried out.

James

[Brian Pascoe]

155 main,air 190 & 210 soldering iron yes jet drills yes and a few idle jets

[LC-GTR-1969]

155 main,air 190 & 210 soldering iron yes jet drills yes and a few idle jets

In your setup have you ever ran the 190 airs?

[Brian Pascoe]

not yet, also have you guys had any 02 sensors only lasting a short time and where exactly do you place them.I place mine as per the  innovate instructions ,but still have no joy with them lasting.

[LC-GTR-1969]

not yet, also have you guys had any 02 sensors only lasting a short time and where exactly do you place them.I place mine as per the  innovate instructions ,but still have no joy with them lasting.

 

I placed mine on top of the exhaust just after the collector. It needs to be higher between 9pm and 3am to avoid condensation. Also, I know octane boosters and the like can prematurely kill 02 sensors- not sure if you're running any but just a thought. 

[jd lj]

If your O2 sensor is the Bosch 4.2 as used in the Innovate lm-2 AFR meter then from some recent research of mine it appears that the VZ commodore uses the same sensor. I have yet to confirm it but I think it's got the correct plug also. If this turns out to be correct then it should be possible to save a few dollars and get a few from the wreckers.

I don't know if this will apply to your AFR gauge Brian but the later Bosch 4.9 sensor can be used with the lm-2 if you get the appropriate cable and run an update on the lm-2. The benefit of the 4.9 over the 4.2 sensor is that it doesn't require a free air calibration and the calibration can be done whilst still fitted in the exhaust.

If you have to calibrate the 4.2 sensor you can cheat and do it whilst in the exhaust by either removing the spark plugs and having someone blow fresh air from an air compressor etc up the exhaust pipe whilst you run the calibration or have someone blow the fresh air up the exhaust whilst you hold the throttles at WOT, they're should be enough valve opening to allow for airflow.

The sensors are apparently sensitive to various chemicals such as some gasket silicones etc. Always check the label and make sure that the product is O2 sensor safe. I've also heard that if water gets inside the cable that it can ruin the sensor as this is where the sensor draws some air from or something along those lines. Running the engine without the sensor powered up can also burn them out within minutes.

I haven't had first hand experience with these problems as I'd rather learn from other people's mistakes and take the appropriate precautions.

James

[Brian Pascoe]

MTX-L: Digital Wideband Air/Fuel Ratio Gauge and the sensor is a Bosch 4.9 wideband

Brian

Edited by Brian Pascoe, 04 December 2017 - 07:17 PM.

[Brian Pascoe]

Finally ordered 34 chokes and 4.5 aux. What wet and dry jets shall I begin with.

Brian

[LC-GTR-1969]

Finally ordered 34 chokes and 4.5 aux. What wet and dry jets shall I begin with.

Brian

 

JD will need to advise here as I have not run these VF style tubes before. 

 

If you were running typical F2 or F16 tubes as most holden 6 fellas do when using typical emulsion tubes, I would run about 140MJ and your 190Airs which will would get you ballpark- maybe a tad rich but you would be safe.

[jd lj]

I'd suggest that you try around a 130 main jet. Keep in mind that with these VF tubes that the main jets are only to adjust the WOT high rpm's mixture.

As for the air correctors it's just going to be trial and error but maybe try around 170+ and if the hesitation is still there increase the air corrector size. As you've probably read Keith is currently working on another version of these tubes for engines that require a higher tip in flow rate, so be sure to keep him updated if you need those.

Don't forget to clean up the AV's to improve the air flow past them. And definitely double check that you've fitted them with the hole pointed to the AV passageway to the e tube well and that they're not back to front. This sounds silly but it happens. A friend of mine recently bought a set of triple dcoe's and 4 out of the 6 AV's were back to front. No wonder the seller didn't like them and sold them, they were almost brand new too.

Everyone else who's using these VF tubes is giving great feedback in terms of increased performance so hopefully we can make them work just as well for you. But if they don't then don't despair a solution for your application is either available already or just around the corner.

James

[jd lj]

Yesterday afternoon I sacrificed a 45f12 idle jet and drilled the internal bore to 3mm. I fitted this in one side of a spare carb body I have which is attached to a box with a clear lid and a vacuum attached to the opposite end. When comparing the two jets the unmodified jet appeared to be flowing more fuel.

Next I plugged up the existing air bleed hole on the modified jet and drilled a new one just above the bottom of the jet and tested it again. Now this jet flows much more than the std one even though both jets have the same fuel inlet and air bleed holes. The reason for this is that it now works as a venturi vacuum pump.

Brian remember that your idle circuit needs to be optimised to transition smoothly to the main circuit regardless of what type of tubes you're using.

James

[jd lj]

Just going back to our recent comments about machining out the chokes to bigger sizes for a moment the following sizes are the maximum choke size for these dcoe carb sizes. This is calculated by subtracting the cross sectional area of the spindle etc from the throat size. It may be possible to physically fit a bigger choke than what is listed but any increase in flow would be minimal.

40dcoe = 34mm

45dcoe = 41.35mm

48dcoe = 42.63mm

50dcoe = 44.64mm

55dcoe = 49.66mm

These are taken from some old notes I have and could probably do with being double checked but they should be close enough for a guide.

[LC-GTR-1969]

It might be worth pointing out that Brian is running a 9 port head, so will be slight differences to carb signal when compared to 12 port heads or 9 port heads running dividers. The 9 port heads will inherently have a little less airspeed at lower rpm hence they tend to want a little more jet.. not a lot more but the siamese port heads naturally have slightly different tune characteristics than 12 port heads with true IR runners. His 9 port head also exacerbates the effect of the oversize chokes as there is some cross feed... the whole port area kind of becomes/ behaves like a plenum.  34mm chokes in a 9 port will behave more like 35 or 36mm chokes in a 12 port. The differences aren't huge but there are differences.

 

EDIT- I added this mainly to help when others search the forum looking at choke selection and tuning... its important to consider the port design as it has a degree of effect on tuning- basically that when running a 9 port you can afford to run a slightly smaller choke than a comparable 12 port and vise versa (ie a 12 port will tolerate a little more choke).

Edited by LC-GTR-1969, 07 December 2017 - 09:04 AM.

[Brian Pascoe]

thanks fellas for the input , I will keep you up to date

[jd lj]

https://www.flickr.c...2478@N02/rK96P6

The attached photo above shows a f2 emulsion tube in position in the emulsion tube well. You'll see the ring of bubbling holes 2mm above the fuel level. Due to this they do a poor job of raising the fuel level and this causes a delay in the tip-in timing of the main circuit. What those holes are actually doing when used in a dcoe is leaning out the main circuit and delaying it's start

There are situations where the f2 does work ok (not in Brian's situation). For this to happen you need a higher manifold vacuum level and a model of dcoe that will extend the dynamic range of the progression circuit.

James

[jd lj]

https://www.flickr.c...2478@N02/cMRR92

This next illustration shows a F16 emulsion tube on the left and one of Keith's O6 tubes on the right (which is what I'm currently using myself).

As you can see the F16 tube suffers from the same problem as the f2 emulsion tubes when used in a dcoe, which is that the ring of bubbling holes is situated above the fuel level and is therefore unable to assist in raising the fuel level to make the main circuit tip in early enough. Instead they are actually leaning out the start of the main circuit just as the f2's do. The F16 emulsion tubes are a larger diameter than the f2's and this slows down the rate that the fuel level can rise even more due to the fact that this creates a narrower passage for the fuel to flow past which slows it down.

The O6 tube on the right however has the ring of bubbling holes submerged by 2mm which means that as the air from the air corrector is drawn through the tube that the 2mm column of fuel above the holes is pushed out by the air (like a plunger) which helps raise the fuel level and once this has happened then the air starts flowing out of those submerged bubbling holes which raises the fuel level even further. The next advantage with these tubes is that you can open or close more of these bubbling holes to adjust the mixture strength at tip-in, remember earlier in this thread when I said that if you blow through a straw into a glass of water that the water level will rise and that by using more straws or straws of a bigger diameter and therefore more or bigger bubbles that then the level will rise faster and further, well the same thing applies to the bubbling holes on these O6 tubes. The air corrector size is then calculated by the number of holes being used so that the minimum size air corrector is used to supply the correct amount of air for the bubbles, doing this also stops the mixture leaning out at high rpm's like normal emulsion tubes do.

The new VF tubes are making even the O6 tubes likely to be obsolete at this stage.

I must give credit to Keith Franck at Sidedraft Central for working all this out and for the illustrations and sharing his vast knowledge.

[Brian Pascoe]

Finally installed 34mm chokes & 4.5 aux. Also have VF installed. The rest is as follows.

155 mains

190 air correctors

50F8 idle

Fired it up & balanced the carbies  Took it for a run, goes good , still a very small hesitation,not sure at what revs, to busy looking at the road. What next fellas.

Brian

Edited by Brian Pascoe, 12 December 2017 - 03:00 PM.

[jd lj]

I expect that you probably need to tweak your mains and air correctors. What mixture readings were you getting at various rpm's.

It may be worthwhile modifying the idle jets as I've previously described if you have a spare set that you can dedicate to the task.

How'd the 34mm chokes feel compared to the previous 40's, I'd expect that they'd be much more enjoyable.

James

[jd lj]

Finally installed 34mm chokes & 4.5 aux. Also have VF installed. The rest is as follows.
155 mains
190 air correctors
50F8 idle
Fired it up & balanced the carbies  Took it for a run, goes good , still a very small hesitation,not sure at what revs, to busy looking at the road. What next fellas.
Brian

If you can tell us what rpm's you still need to work on then we can advise you from there.

What pump jets, discharge valves, springs and rods are you using on your pump circuit?

James

[Brian Pascoe]

Will be doing some road testing at the weekend to collect as much data as possible for you guys. 

Brian

Edited by Brian Pascoe, 13 December 2017 - 06:50 AM.

[LC-GTR-1969]

Glad to hear you have the 34mm chokes... 

 

I think your mains and air correctors will be too big for ideal, but a rich side of tune will always run better than a lean side of tune. 

 

Once you can log the data, we should be able to help identify next steps to help you get the fine tuning down pat. 

 

I generally aim for a lean cruise and lean idle (street cars benefit from lean idle in traffic etc)- low to mid 14s if I can get it without causing issues etc... 

 

Then I generally aim for low to mid 12s on WOT through to redline. Some will aim for high 12s like 12.8:1 but its just a number- and I have found my engine was happy on the rich side for WOT and made most power there (verified through back to back tests on dyno then drag strip).

 

A video may help in the car- drive around with the camera pointed towards your wideband and drive normally, then give it a squirt in a safe place and take it to redline. Your tune will likely be fairly rich with current MJets so it should be safe. 

 

It would also help if you could describe the hesitation- is it when initially opening the throttle/ tramping your foot down or does it stumble when cruising and slowly working up the rpm, at say 2500?

Edited by LC-GTR-1969, 13 December 2017 - 10:09 AM.

[Brian Pascoe]

Pump jets = 50,

spill jets = blank in it at the moment , have a size 50.

The spring is 45mm long x .65mm cross section dia.

Pump Rod  A= 58.5. B = 38.55 P/N 10410.016

[jd lj]

Your pump jets are most likely a bit rich, 40's to 45's would be more suitable with 34mm chokes.

I'll cross reference your spring and rod sizes later to confirm which ones they are.

The pump circuit can be complicated as there's 4 different components that all interact on each variable differently. I don't have time right now but I'll elaborate later.

There's the following adjustable aspects,
-Volume per second
-Total volume
-Pressure of the shot
-Duration
-Throttle opening that more pump shot is available.

James

Ps, soon I'll be testing the enhanced VF tubes that may be suitable for you too.

[jd lj]

If you don't have any smaller pump jets at the moment I'd stick the size 50 spill jets in whilst using the 50 pump jets.

James