Dizzy Question

[Celica_73]

Ok first I'd like to state I've search both new and old forum plus the Internet and found no information.

Cleaning my Dizzy up ready for my Hybrid Build on the weekend I discovered I've been running a 2T-B (9100-26021) dizzy in a 2T-G. Don't some research to discovers a large difference in the mapping both mechanical and Vacuum. So with this in mind was wondering what the mapping of a 3T-C and which mapping they are using on a 2TG/3T hybrid. Both mechanical and vacuum if possible.

Thanks

[Celica_73]

OK then what dizzy are people using the 3T-c or the 2T-G or is it just a straight 2T dizzy?

[MRMOPARMAN]

if it fits properly, and it works properly, it would probably be cheaper to regraph your current dissy than trying to find a TG dissy. it would probably be wise to get any dissy regraphed for a hybrid conversion anyways.. if you tell the shop doing the regraphing what your specs are (they should ask) they should be able to regraph fairly well off the bat, but dynoing after its done for tweaking may be required

[Celica_73]

thats all good but no one up here wants to touch a carby engine to tune. Hense why i'm asking for some info.

[oldcorollas]

it should be listed in one of the manuals no?

the toyota engine books should have the 2 stage info, and vac advance info as well..
usually they are "all in" by maybe 3000-4000rpm or so..

[Rodger]

Any of the T series based dizzies can be used.

There are a couple of things that can be changed that become the basis of dizzy graphing.

Toyota advance plates usually have two mechanical advance options (slots). Pick the one that has the larger degree value. These by the way are distributor advance degrees. So a 12 degree slot equates to 24 degrees of mechanical advance at the crank.

The stiffness (spring rate) of the springs determines the rate at which the mechaniclal advance, advances. Stiffer springs means advance takes longer to reach maximum. The same thing can be done with changing the actual advance weights but it is far harder to find different weights.

As you are running sidedraughts there is no need to run a vacuum advance. You can either remove the mechanism and lock the advance plate or simply leave the mech on and lock the shaft of the vacuum device.

With the way my non-vacuum T series dizzy is set up I can run ULP with 11:1 comp.

The idea is to be able to advance the ignition enough at high speed so that it does not detonate (ping) and you have the maximum power, however you need enough advance at low speed WOT to give good torque and give good throttle response and still not ping.

As oldcorollas says all advance is usually in by 3000-4000 and it is around 32-34 degrees total. Static + Mechanical + any Vacuum (usually none by then)

My settings are 10 degrees static/idle crank timing and 12 dizzy advance (24 crank) = 34 total.

Once you look at how it all works then things become clearer. So as I said before any of the T series dizzies can be modified to work well. Even ones that at best have been marked 10 degrees or even 6 degrees as the slots can simply be elongated to give what ever maximum mechanical advance you desire.

Regards

Rodger

[Celica_73]

Ok Much thanks for the info rodger and Oldcorollas the reason i'm asking what people are running in the Hybrids is the 2T and 2T-B Dizzys is a 2 stage advance and the 2T-G is a single stage mechanical.

Refering to the tractor and mechanical Publications for the Celica and Carina (pg 177)

Dizzyaaaaaaaaaaaaaaaa Dizzy RPMaaaaaaaaaa Advance
________________________________________________
2T (19100-25011)aaaaaaaa 500 aaaaaaaaaaaaa Begins
aaaaaaaaaaaaaaaaaaaaaa 1300 aaaaaaaaaaaaaa 10
aaaaaaaaaaaaaaaaaaaaaa 2400 aaaaaaaaaaaaaaa13
________________________________________________
2T (19100-25012)aaaaaaaa 500 aaaaaaaaaaaaa Begins
aaaaaaaaaaaaaaaaaaaaaa 1300 aaaaaaaaaaaaaa 10

________________________________________________
2T-B (19100-26021)aaaaaa 500 aaaaaaaaaaaaa Begins
aaaaaaaaaaaaaaaaaaaaaa 1000 aaaaaaaaaaaaaaa 6
aaaaaaaaaaaaaaaaaaaaaa 2400 aaaaaaaaaaaaaaa11
________________________________________________
2T-B (19100-26022)aaaaaa 500 aaaaaaaaaaaaa Begins
aaaaaaaaaaaaaaaaaaaaaa 1000 aaaaaaaaaaaaaaa 6
aaaaaaaaaaaaaaaaaaaaaa 1800 aaaaaaaaaaaaaaaa9
_________________________________________________
2T-G (19100-88221) aaaaaa500 aaaaaaaaaaaaaBegins
aaaaaaaaaaaaaaaaaaaaaaa1200aaaaaaaaaaaaaaa 8
_________________________________________________
2T-G (19100-88222)aaaaaa 600 aaaaaaaaaaaaa Begins
aaaaaaaaaaaaaaaaaaaaaaa1300aaaaaaaaaaaaaa 14.5

I understand how the Dizzy works and that But as i'm going to be using a Jarcar programmable adjustment I'm just wondering which comfiguration to start with.

Another question Rodger you stated theat Vacuum Advange not required with side drafts could you explain why please as the stock 2T-G dizzy has a vacuum adavnce. From what I'm adware the vacuum mainly comes into play when engine braking/foot off the accelerator for eccomony.

[TA23 Racer]

The vacuum advance works when there is a vacuum present in the intake system. That means when at light throttle loads the engine can handle more ignition advance this makes the engine far more driveable around town, the vacuum advance helps light throttle response.
Engines with racer cam profiles need more mechanical advance down low in the rpm range due to poor cylinder filling due to valve timing overlap. So quick generalisation small cam profiles benefit from vac advance big cams don't need it.
Programable ignition advance is the way to go, you get the right ignition advance for every engine speed (rpm) and load (throttle position).
Cheers hope this helps.

[Celica_73]

Ok Thanks for the info TA23 Racer. The engine has a mild grind so I've been told.

The programmer only has 2 points similar to the mechanical advance in the distributor. But has a micro switch that can be wired to the Vacuum Advance as well. Only simple as only a Carby engine.

[Rodger]

As TA23 Racer has said. The way to get low-mid range response is to advance the timing and because the mecanical advance mechanism cannot provide it at those revs the vacuum mechanism takes the role. If the mecanical advance were light enough then it would advance too fast and be to advanced in the mid range. It is all a big compromise.

Even with a mild cam there may not be enough vacuum for an effective gain of any useful mid range torque/drivability. Hence to compensate you would tend to run a bit more static advance.

I think if you look closely at the table and add the static timing of each engine all the numbers add up to the 32-34 degrees maximum advance. I had done this years ago so if my memory is wrong then so be it (I suppose I could do it again). It is just how Toyota got to that maximum advance as to why we see so many different set ups, remembering also there are several versions of each engine ie, full pollution, less polluting and anti-polluting versions.

Stock 2T-Gs are relatively poor in mid range. Toyota would have opted to include the Vacuum advance for two reasons. 1) They had a dizzy already with it on, as it is a direct derivative of the 2T and 2T-B. 2) Gain more low- mid range drivability.

I know nothing about the Jaycar unit, however, if the Jaycar unit allows, use the mechanical advance that has the higher number option so that a bit more advance is added low down and through the mid range but then set it so the maximum is 32-34 degrees.

Then it will be down to driving tests. Advance the static timing until it just pings under full load in the mid rev range say starting at 2000 rpm. Then back it off to just stop it pinging.

And then there is the question of balancing all that with jetting set up.

Regards

Rodger

[Celica_73]

Sweet as for the advise. Engine is currently at the re conditioners hope to have it back in 4 weeks. Then i can play around a bit more with it all.

As for jetting I'll be seeing how the current jets go first. As it's a early 2T-G high compression the jetting is already pretty big but if other jets are required I'll be contacting you Rodger for bigger jet.

Thanks again I'll let you know how it works out.

[TA23 Racer]

Excellent work Rodger! Remember Celica 73. The amount of ignition advance at full load will vary depending fuel mixture strength (air fuel ratio) so it's a bit of a juggle for max power but as long as it's not pinging any were through the rev range is really the main thing.

Cheers Dave.