Great video, I thought I would add a bit to help. Firstly programming a 123 dizzy. As an example lets simulate a 25D41288 MGB dizzy. I would add the two points at 500 rpm and 1000 rpm and make these both the dynamic timing for that dizzy - 14 degrees, which is a combination of 10 static plus 4 degrees centrifugal advance. Then at 1600 rpm I would add 22.5 ( 10 static plus 12.5 centrifugal ) and the 30 degrees at 2200 rpm ( 10 static plus 20 centrifugal ). That is the end of the advance curve for this dizzy. This is where the 123 is brilliant, because we can enhance this curve beyond 2200 rpm. 32.5 degrees at 2600 rpm, 33.5 degrees at 3000 rpm, 34 degrees at 3300 rpm, 34.5 at 3700 rpm and 36 at 8000 rpm. The vacuum advance can be obtained from the case of the dizzy, for the 25D41288 advance starts at 87KPa and finishes at 20 degrees at 69 KPa . Then continues at this level. In practice I do not set vacuum advance above 10 degrees using the same points. On the 123 dizzy I use the feature that enables me to turn off vacuum advance below a certain Rpm, I do this at 1100 rpm so idle has no advance. With all the points above you can experiment according to the tune of the vehicle. If you can get a workshop manual all of the curves for each engine and dizzy type are given, alternatively you can get them on the web, www.mgb-stuff.org.uk/curvestext.htm. Timing a 123 dizzy. Set to TDC as the green light comes on. The car should start immediately. If you have access to a programable strobe, set it for 14 degrees, disconnect the vacuum advance and check 14 degrees on the program corresponds to TDC, adjust the dizzy as necessary. Remember to reconnect the vacuum advance tube. Timing done. You can change the program and NEVER have to change the timing. Then balance and adjust the carbs. Your car will be smoother, with better low down pick up and mid range torque. Much more drivable than even a good original dizzy. 123 dizzy gets you about 90% of the way there. A megajolt takes you to the next level of incremental gains. Given its extra cost and complexity I would add it to a balanced, gas flowed with better cam type of engine on an MGB, but then I would probably also add a 5 speed gearbox, change the rear axle ratio, put GAZ rear dampers on with a Panhard rod, a slightly stronger anti-roll bar and front lever arm dampers that can be adjusted for damping and adjustable camber.
If you set up your timing light you can use the static advance feature on the 123 to get perfect agreement between what the 123 is reporting and what it actually is. Also, to tune the vacuum advance you should check your vacuum level on the app at cruise and under WOT, set lower end of curve so you have full advance at cruise (on a flat road, very little engine load) and no vac advance at WOT with some margin (ie, if WOT vacuum is around 80 to 85kP then set zero at 75kP).
Cheers Chris, I'd not thought of that, I'll change the static in the app... it'll be particularly useful with the SC. Il get back to the vacuum.... I'd be good if it could record parameters from a drive in the app.
@@Exhausted-autos I have asked them multiple times to enable logging but the best I have managed is recording the screen and then syncing the video with my other logged parameters like AFR from the wideband.
Great content I had a 67 roadster in the early eighties with a lot of performance mods and harder suspension used to drive it to the track thrash it and drive it home again, nothing ever went wrong with that car, watching your videos I am getting the urge to find a B that I can restore, my dad and myself did the first one. I am nearly retired so I think it would be fun, still have the old workshop books cheers from NZ.
In general not a bad little video, so please do not take the following comments as a criticism of any way. So firstly, if the car is a runner before the distributor upgrade, its worth taking the cap off the existing distributor and taking a quick photo. This can become a reference position for the new distributor installation. Showing people the compression stroke via valve closure is a great idea, just as you've done in the video. Some sadly don't know which way to turn the crank shaft pulley, so this can a be a good time to explain the distributor rotor should be turning 'anti-clockwise' as you rotate the crankshaft pulley. Or depending on ground conditions, the same can be achieved by pushing the car forward whilst in gear (handbrake off of course).OK.....now on to the base/static ignition timing.......you've always got to check this with a strobe. If you were 2, 3 or 5 degree out from the static applied, it then makes your whole mechanical advance curve into a joke, because every key check position is than also 2, 3 or 5 deg out also. So now onto the top end of your mechanical advance curve.....throttle open and under load, you do NOT want to me aiming for late 40's to 50's crank degrees!!!! Let me give you an example why. One of the most highly regarded Lucas Distributor curves of the day was the same as used in the Mini Cooper 23D4 S/N40819/41033/41210. If people upgraded their MGB with the typical mods (cam , head, exhaust) this is what they fitted, direct from the mini to the MGB because of it's 'sporty' advance curve. So......if I now told you that with the 'S' distributor fitted from a base idle of 10 deg BTDC full mechanical advance at 4000rpm gave between approx 28 and 32 deg BTDC of crank shaft degrees. We'd now all be wondering why you were aiming for late 40's to 50 at wide open throttle!!! When you go on to supercharge your engine, you'll probably find a full mechanical advance required is even lower....24 to 28 BTDC depending on other factors. Again, no offence meant, and some great content in the video......just extreme caution about mechanical advance up there in the late 40's of crank deg, it's a definite No No...
Thanks for the detailed comment, I'm always happy to learn You're spot on re the supercharger and that's why ive fitted the 123 in the first place to give better control and limit the advance. Ive not gone back to rewatch, but thought I was pitching at 40s on the dizzy and not crank. Either ways il be very cautious with the sc set up and then get it on a rolling road with someone who properly knows what they're talking about.
@@Exhausted-autos ....no probs at all. 40' on dizzy equates to 80's at the crank. Very easy to mix the two. Luckily the MGB engine is quite robust, and the worst I've seen is 42 BTDC crank at idle (vac disconnected) 62 with vac and somehow it survived.
Should the curve on the app just be the advance without the vacuum amount added? I've got one of those dizzys on my v8 but it's an early one with just a fixed set of curves to choose from and I found I needed to ad extra by turning the dizzy too but they are nice bits of kit.
The vacuum should be independent. You want vacuum advance on cruise, but zero on Wide open throttle... but as it's ported on the carb the vacuum drops away as the butterfly valve is fully open.
