Weber Jetting - Standard Engine

[Chrispy]

This might be opening a small can of worms but here goes

For those of us running standard Twincams with Weber's what jets are you running?

I have a standard +2 with factory C type cams (one groove). When I got it the engine was down a bit of compression and had the following fitted:

Chokes/Venturi: 30mm
Low speed jet: 45F8
Main jet:120
Air corrector: 150
Pump jet 35
Emulsion tube: F11


I understand the following is the factory fit for c type cams/SE engines:
Chokes/Venturi: 32mm (30mm)
Low speed jet: 50F8
Main jet:115
Air corrector: 150 (200 - to match the 30mm venturi)
Pump jet 40
Emulsion tube: F11

Now I've rebuilt the engine to standard specs I've got a bit of a hesitation around transition, and a bit of spitting on light throttle when cruising. I read around the place that modern fuel does burn a bit different. Do the standard jetting specs still work well? There aren't many places around here that specialise in this sort of thing and before I buy a bucket of jets and a WB02 I thought I'd see what others are doing

[Grizzly]

Depends on how well you want to set it up? First thing to do is sign up to Keith Francks sidedraft_central yahoo group and read his White paper!!

I ran the stock big valve set up for a while, it did run ok but i bought a wideband o2 kit and that pointed out just how bad the cruise / off throttle set up was. Ironically the full throttle set up was relatively good which made me think Lotus did it like that to cover other lean holes in the tune. People more clued up on this than me suggest the stock Weber idle jet design is flawed for use on an engine that pulls under 20hg which may well be why it's like that.

After months of messing and experimenting i went with Keiths low vacuum W Idle jets,VF tubes and 36mm chokes....... the VF tubes were almost plug and play (i would guess 10 more hp under wide open throttle through the rev range with the stock wet/dry jets fitted, enough hp increase for you to really feel it) but the Idle jets weren't a direct swap, i'm currently running W40 jets in my Sprint and it's giving me 13-13.8 afr through the progression holes. From my experience like for like afr's you need a size smaller wet hole in the W jet. I found with the W jets you can get much closer to the magic 14.7afr without any big lean holes appearing which means quite a big difference to your MPG, the smoothness of the Cruise is improved and my plugs last much longer too.

I'd say it's now a dam sight closer to the 126hp peak it's supposed to be now.

[nmauduit]

Depends on how well you want to set it up?
... you can get much closer to the magic 14.7afr ...

14.7 is for best fuel economy as that corresponds to the stoichiometric ratio (best combustion)

for maximizing power one usually shoots at a target in the 13-13.5 range...

[mbell]

I have the older Kieth Frank Jets in mine. I had to go up a size on the idle Jets to get rid of the stumble, fuel here is rubbish thou. I find have have to adjust the carbs between summer and winter fuels.

The good thing about the updated Jets, appart from them being better, is they are configurable. So often you just need one and then adjust it rather than buying lots of standard Jets.

My personal advice would be to buy a afr gauge. They can be had for relatively little money and avoid doing it in the dark.

[Grizzly]

Depends on how well you want to set it up?
... you can get much closer to the magic 14.7afr ...

14.7 is for best fuel economy as that corresponds to the stoichiometric ratio (best combustion)

for maximizing power one usually shoots at a target in the 13-13.5 range...

My full throttle (main circuit) is bang on 12.5afr (does lean out a bit as it approaches redline) but thats just 36mm chokes and VF tubes dropped in (pulls like a train!!) as you say 14.7 progression is the ideal cruise afr but achieving it with no big holes is a totally different story.

I had to go up a size on the idle Jets to get rid of the stumble.

I had a similar story, what Keith told me to do is set the idle afr to 12 which covers the lean hole as you come off idle, once that was fixed i dialed out allot of fuel in the progression. Only down side is it makes it a pain to start from stone cold (i need to use the choke which i never had to do with the stock jets)

[prezoom]

There is a lot of discussion about O2 gauges, Keith is set on one or more of the Innovate gauges. I noticed an AEM gauge on his bench when I was at his shop, but he did not recommend that unit. What are you guys using. Currently trying to set up my S2 with a standard engine, using the VF tubes and 20 Hypo idle jets. My Zetec Plus2 was a piece of cake to set up with the VF tubes and its standard jetting, and the tubes really woke up the mid and top range. In the S2, I having a problem with the transition portion.

[mbell]

I just have a cheap aem unit, fitted in place of the clock. Not going to claim is best ever but gives you an idea of what is going on. Something with lots of data capture would be a better but then your paying 10x the cost. For Keith that would be well worth it, for me doing one setup and monitoring it's not.

I think the aem was around $100, so when you factor jet costs for experimenting etc and your time it is closer to no brainer for me.

[Grizzly]

There is a lot of discussion about O2 gauges, Keith is set on one or more of the Innovate gauges. I noticed an AEM gauge on his bench when I was at his shop, but he did not recommend that unit. What are you guys using.

I have done most of my messing with an Innovate LC-2 but i've just bought a Techedge 2j9. Both units have similar software (Innovate is slightly better imho) but the Techedge can add RPM and Throttle position for the same price (you need a weber TPS kit as well to do that but it does have the option) you would need the Innovate LM-2 to get the same options at quite a big difference in price. Personally i'd try and steer towards the later LSU4.9 sensor too, i have had a play with a LSU4.2 and the range is much smaller, plus the 4.9 i have been using has had some abuse and (touch wood) keeps on going.

I haven't used the Techedge enough to recommend it or not yet but the Innovate is junk, when it's working it works fine but i've had all sorts of problems with it disconnection and reconnecting at the most inappropriate times (very temperamental), another reason not to use Innovate is the customer service.... they are genuinely poor!! the place i bought my LC-2 from tried to help as much as they could (even lending me an LC-1 to try) but Innovate was having none of it.

Also i'd advise away from using an afr gauge, i tried that when i started having problems with my Innovate and it's just not fast enough to see lean holes...... Now i don't know if thats just the Innovate gauge i was using but some thing to bear in mind.

Just my Opinion.......

[Chrispy]

Thanks everyone. I've previously had a AEM UEGO WB02 years ago on a turbo car which worked fine for me. Very reliable connecting to the tuning software etc. Seemed to react very quickly as well.

I've been trying to get onto Mr Franck's forums for some time with little luck! I did find his white paper, and I also have a few other books along with the Weber tuning manual.

What are these VF tubes?

[StressCraxx]

Thanks everyone. I've previously had a AEM UEGO WB02 years ago on a turbo car which worked fine for me. Very reliable connecting to the tuning software etc. Seemed to react very quickly as well.

I've been trying to get onto Mr Franck's forums for some time with little luck! I did find his white paper, and I also have a few other books along with the Weber tuning manual.

What are these VF tubes?

Hello Chrispy,

Sorry to hear you are having such grief with getting on the weber forum. Please PM me your email address and I will forward to Keith for you. The Yahoo forums are very clunky for admins.

I have a set of his earlier E-tubes and hypojets and the improvment is striking.

Regards,
Dan Wise

[prezoom]

Thanks for the information. Every little bit helps. When I was with Keith, he was evaluating some other options on O2 gauges, but had not reached a decision at that time. For me, something is better than nothing. Not adverse to upgrading at a later date. The VF tubes in the Zetec were sort of a butt dyno thing. Would like to fine tune main circuit to see if I can make it better. We were able to get the idle circuit set properly, and the transition to the main is seamless. The S2 is proving to be another story. Hollywood3645 just got a set of the new smaller/shallower grooved VF tubes from Keith Friday. He was having massive rich condition with the main circuit. Between the two of us, we need to get properly instrumented.

[Grizzly]

Rob, did you change the chokes with the VF tubes? i noticed the VF tubes were coming in too early so i would get a big overlap until i reduced the mains vacuum with bigger chokes (Keith actually told me to do that from day one but i hadn't received them at that point)

I'm not sure which version of VF tube i have fitted but they work really well (think i got mine about February)

[prezoom]

Keith and I discussed choke sizes during our visit. The Zetec was equipped with 38mm which worked well. Keith was running basically sleeves, 40mm, in his car. Wanting to be a little more in line with a venturi, I installed 38mm chokes in the 18's. Since then I have tried the original 30's, 32"s and 34's, None of which helped with the transition between idle and main. I have an extra set of 32's, which I will turn into 36's, so will have a good selection to mess with. Keith is insistent that you cannot correctly tune the carbs without establishing the vacuum level at idle. He uses a small one way check valve between the intake and the vacuum gauge to stabilize the reading. These can be found from swimming pool companies as used in some sort of ozone equipment. They have a viton diaphragm, which is fuel resistant. Checked with my local pool stores, and they had nothing on hand. Found them on line and ordered a couple of two packs for Holywood3645 and myself. Mean while, I will keep trying to fix the passenger door latch push button, which no longer functions.

[UAB807F]

Hi folks,

I apologise in advance for veering off topic slightly, but can someone chip in about these Air/Fuel devices you're all using ?

I'm only a DIY guy but I can see the advantages of being able to measure exactly what's happening with the fuel ratios and after sitting on the fence for several years I think it's time to spend something. I don't need an all singing/dancing professional outfit and would like something that I can move between the Elan/Europa as & when needed, not something I need to permanently install on the dash. I'll put a blank bung in each exhaust but probably remove the sensor after a session.

Although they seem to be everywhere, I've read mixed reviews on Innovate and as I don't know the market it makes me a bit hesitant to buy their kit.

Given that I have almost zero knowledge, this one looked as if it would do the job

https://www.tpl-parts.co.uk/product/PLX-0106/PLX-Devices/C6AFRG4/DM-6-52mm-+-SM-AFR-GEN4-Combo

but as I said, I have no real knowledge here. Ideally I'd like a digital display and the option to record it onto a laptop or android tablet for later reference. So the question is, what are you guys using and how easy/reliable are these kits ?

Cheers,
Brian

[Grizzly]

Brain, Be careful that the Wideband kit you look at has a serial or usb output you can connect to your laptop, if it doesn't you will need a separate data logger to connect to a laptop or you will be stuck trying to do a set up in real time (which is a pain)

Another thing to look at is the software it comes with, Innovate wins accuracy and ease of use because of it's quality Logworks program (plus the fact you have to keep fresh air calibrating the sensor which is a pain). Innovate would be a great package if the unit wasn't cheep junk.

In my opinion being able to log a drive is key, if you have the ability to log revs and throttle position too it makes it 10 times easier.