Just wanted to share a recommendation for Keith Franck’s new BP emulsion tubes for any of you running Weber 40DCOEs and 30mm chokes - my little 7 makes me smile everytime in it, but with these tubes installed it is truly a sh*t-eating grin. Don’t try them if you like endless tweaking, but if you are ready to eliminate the off idle hesitation and have great tractability and power throughout the rpm range, well, I think he’s found it with these. I’m very impressed.
By curiosity (and the never quenched thurst of the perfect tune and extra hp I must admit) I tried last October the new at the time AB “hypotube”(recommended by him for my specific application), and was not convinced by the dyno session: in retrospect these appear to me as a yet an other variation of emulsion tubes, and I did not see them improving on a decently set up road car (actually minus 5HP on a road engine of around 130, and no “magical” effect mid range or wherever). Maybe it’s just me…
The standard for the Seven is 115 fuel jets and 180 dry jets in the F16 emulsion tube, with a 50F9 idlejets, Keith’s NF and now BP tubes seem to be much more efficient at pulling air into the mixture, so my initial test was with 115 air jets. With the NF jets, I was not getting the impact on lower rpm mixture (to the extent I could feel it, I’m not doing it by proper testing, I acknowledge) I expected by big shifts in the air jets. So, those tubes were better in the midrange and at high rpm than stock F16, and also better at lower rpms but still left a bit to be desired that I was not being successful in tuniing with jet changes. The newer BP tubes eliminated the low rpm stumble immediately with 115/115 and kept performing throught the rpm range. I have not yet had time to tweak, but will see if I can improve
He also makes idle jets (what he calls a hypojet version for engines with strong manifold vacuum and I don’t remember the name of the other for engines with less vacuum. I have not experimented witth these, yet, as I don’t have a reliable way to test vacuum.
Phil - I’d be happy to loan you my older version NF tubes for trial if you’d like.
Keith sells H and W idle jets, the W jets are for 18"hg or less.
I have a set of his W40 idle jets and currently have them set up to 12.5 afr cruise, i think they are much smoother than stock jets and easier to set up with his sliding cover over air holes.
As for the Tubes, i have the VF tubes with 36mm chokes and it goes like a stabbed rat although they needed a bit of tweaking to lean out the tip in.
I’d be interested to hear someones opinion on the new tubes that have driven a car with the VF tubes fitted.
Apologies for butting in on this chat, but I notice you are in France and clearly someone who is always looking to optimise the performance of your Elan. Do you know someone with a dyno that has good knowlede of tuning the TC engine, preferably not too far from Normandie, Gaillon/Vernon? Where in France are you?
I’m near Paris on the east side, went to an understanding dyno less than an hour away (south part of 77) as many of them do the tuning themselves using lots of electronics (on modern cars run by maps): the owner did not have experience with carbs but let me do it with my equipment, spare jets etc. while he was just launching the pulls on the dyno. My car had been equipped with a wideband lambda sensor, which helped me get closer to a decent tune prior to that. Hopefully you should be able to find someone closer to you, but if you want to get in touch with him this is Carprog in 77690 (fyi it took us a good hour to strap the car on the dyno, quite small for the setup - and he was very helpful with that, too).
Hi Chris,
I’ve been running with Keith’s VF tubes on my Sprint-spec TC for a couple of years now. Recently, I also moved up from 33mm to 36mm chokes and immediately noticed the engine pulling more strongly at higher revs, right up to the red line.
Initially, found that the W40/2 idle jets (that had been working nicely along with the 33mm chokes), now ran out of steam around 2k rpm, before the VF tubes tipped-in. Moving to W45 idle jets filled in the gap and made the car driveable again!
Great fun now, but I still think there is some room for improvement at transition. So I’m interested to hear what “tweaks” you applied to achieve this on your Elan.
My current set-up: 40DCOE18, 36 chokes, VF tubes, 130 main, 145 air, W45/2
Cheers, Doug
In the Alfa community a lot of folks use AFR dataloggers such as the wideband Zeitronix ZT-22 for tuning webers. This allows you to log AFR versus rpm (but not load like a true 3D system), but nonetheless shows where transitions are weak and what the impact of each change made is. A lot of the modified ETs out there have been shown (using data) to be subjective at best. You can create you own modified ETs via obtaining a set of jet drills and a soldering iron and experimenting with both placement and size of the holes drilled to change the emulsion and when this happens (with respect to fuel level, etc).
Without the data, sometimes a transition from rich to weak (or viceversa) can feel like an improvement due to the change in mixture. Generally we aim for around 12.5 to 13.5 as a target AFR (which is pretty difficult to obtain across all rpm with Webers), but it’s especially important not to go weak at high rpm!
In the US you can get a AEM wideband for $130. I’ve just spent ~$17 on a serial connector and serial to USB-C cable that allows me to log the data straight to my phone.
It doesn’t do RPM directly but I expect to be able to figure it out from the data if doing repeatable things. If not I’ll point the camera at the tach and record the rpm on a video. Then cross reference the time stamp between data and video.
Fascinating stuff. Can anyone tell me the difference between BP tubes and ordinary ones? A phot comparison perhaps. Also are these available in Europe or does Franck do mail order? Cannot find him on the internet. Cheers.
Try looking up :-
Keith franck sidedraft central, on google. That should give you a way in. He is a retired scientist who has been working on improving Weber and other carburettors for many years now.
some fascinating stuff there. You may have to join a yahoo group for access. eventually you will find a webstore.
Eric in Burnley
S3SE
A link to his group is in the first post in this thread. He sells through a “WebStore”, and I’m pretty sure that link is on the sidedraft central group site, though it may be embedded in one if the topic discussions.
I’ll try to grab some side-by-side photos when I’m playing with it this weekend, but what you need to know if you decide to try his bits is that Keith is constantly experimenting, tweaking and further developing to try to make more predictable and efficient air/fuel mix and flow.
The BP tubes were specifically designed (recently) as an improvement over the prior NF (non-frothing) tubes for small chokes after he discovered that with smaller chokes while the NF ran well they did not respond to air/dry jets changes. Most of his recent work has been to try to make the BP tubes work well for medium and large chokes, in hopes of creating a single tube design.
I’ve tried the NF and BP tubes and found both an improvement over the standard weber e-tubes - better and more consistent through the rpm range, though admittedly by feel and I have not dyno’d or tested AFR.
I thought it might be interesting to recount my experience with Keith Franks NF tubes in my Elan S3 S/E. I was impressed with the information on the Sidedraft website and took the plunge and bought them. I fitted them and was very disappointed. Rough running no oomph and so on. It turned out that I had not read the instructions properly!! Anyway KF was very patient and steered me in the right direction and soon I was experiencing a LOT more power but still issues with rough running at steady throttle and jerkiness at times. I have a really good chum who is an engineer in the classic car business and between us we fiddled with jet sizes and have now hacked all the problems. The car now goes, like I said before somewhere, like a greased weasel, pulls from 1000rpm in top if I am gentle and accelerates like an electrified cheetah!!
Remember I am the silly old fool who had a 3:1 CWP made instead of faffing around throwing money at a 5 speed.
I thought I would give you my final set up which is working wonderfully.
1700cc engine with QED 420 cams, Distributor Doctor electric ignition and Webers jetted as follows.
34mm chokes - Main jets 150, Air correctors 185 and Idle jets 50F8
It may not align with some of the charts I have seen but it works. Happy Bunny now and cannot wait to get back to the French Alps and chase motorbikes.
FF has been endlessly supportive via email and I heartily recommend his NF tubes but be prepared to fiddle about a bit. D