103 replies to this topic

[Bruiser]

Thanks Trevor
If I had known about fuzzypumper’s write up before, I’d have saved myself the trouble
That’s far more thorough and in-depth than my ramblings here
Didn’t think there was anything out there blue motor bosch specific
I’ve been well and truly shown up hahah

[LJ RB30]

No way mate, you have given me & obviously others the motivation to have a crack at tweaking these units! 😁👍 That’s a good thing😁
I had trouble finding fuzzys write up so I had to crank up the computer and see what it was called as I saved it many years ago
Keep up the good work mate & please keep us updated on your results as it all helps us keep these old girls cranking 😁😁😁👍

[claysummers]

Just bumped it to make a bit easier to find hopefully.....

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[73TORANA!]

Hey Bruce how did it all turn out?

I got given a Sun Dizzy tester the other day so I thought I would check out my dizzy that was recently graphed by scorcher here in Melbourne and i came up with these figures. They said to set static at 14 deg so I will add the mechanical to the static in my figures to give the total advance, Cam is a standard XU1 or 373 wade, 11:1 comp. The dizzy has a 10 deg mechanical advance, it also has 8 deg vac advance.

14 @1k rpm

16     1700 

18     2100

20     2600

22     3000

24     3300

26     3800

28     4200

30     4700

32     5000

34     5600

No further advance after 5600rpm

Cheers, Geoff.

[Bruiser]

Hi Geoff
Turned out all ok, I haven’t changed anything from the last graph I drew up.
My tuning activities are on hold for now as the engine is out for a new set of bearings etc at the moment.
The motor behaved well, for such a big cam the power seemed more biased towards the lower/ mid rpm’s
than I had expected. Not weak, but not “here’s the cam coming on now” if you get what I mean
Thanks for putting up your numbers, it’s terrific to get to see what a place like
Scorcher ignitions chose to match your setup.
You’re a lucky man having the graph machine, much better than my protractors and stickytape hehe
Interesting how your curve doesn’t peak until 5600 rpm - I wonder if the 11:1 on that cam played
much of a part in their choice of curve for you.
My last cam was the same as yours running at 10:1 , didn’t think you’d get away with 11:1

This all just makes me wonder again if there could be an
improvement in slowing down the curve a bit…

How does your motor behave with that dizzy setup?

[73TORANA!]

Hi Bruce,

The 11:1 doesnt seem to be a problem that i have noticed although I did a lot of work to keep the AFR in control.

My set up is basically an XU1 with CD175's but with a 161 head with 1.75 inlets and 1.5 exhaust valves, but Schorcher didnt seemed phased by that, they were mostly interested in the cam profile and compression, Oh they did ask auto or manual and if I ran vac advance.

The engine is very responsive down low and will pull very well up to 6k. (NGK BP5ES plugs )

As a bench mark It will out perform a std XU1 with a 3.36 diff, easily with out any problem; mine has a 3.08 so it seems to go ok.

 

You could be right with the 11:1 and the curve finishing at 5600, incidentally in the XU1 book by Fiv Antoniou there is a graph for the LJ option that also shows a max advance at 5600. stating a max mechanical of between 22 and 26 deg plus a static of 10 making a possible of 36 total. Have you seen it?

 

If I lower the static from 14 to say 10 it is quite noticeable in its responsiveness ( better with 14 ) and the vac advance makes a big difference under light to medium throttle. 

 

I put it on a dyno years ago with this same dizzy and it ran best with 2 more deg up top, it dropped off with 4 extra up top so for me 34 total is a good safe amount.

 

The only issue i have is that in cruise at between 60 and 80 kph I have what feels like a slight surge or cam jerk which is why I was looking at dizzi stuff and found your post.

Had this issue for years with different engines ( same head ) different dizzi, AFR's good, no vac leaks, strange though if you give it a hard time them back to cruise its great then it slowly creeps back haha. Definitely changes with fuel batches although AFR stays constant , any way thats off topic.

 

Yes very lucky to score the tester. I was looking for point scatter in mine due to the issue mentioned above but its solid and I got told to keep the tester. Hell yeh 

 

I put a stock black motor dizzy on the tester and it seems to put all its advance in by 3k with a steep ramp from 1700 to 2k then its all over by 3500

So I dug out an old stock 186 dizzi and it started at around 900 and rose steeply to around 2k then a steady climb to 4800 with a max mech adv of 22 plus 6 static would be a total of 28 deg.

 

Good on you for giving it a crack, its great to see people still experimenting and teaching them self's engineering, I prefer this way than with a lap top but im old haha 

Cheers.

[Bruiser]

Sounds like a good setup you have there
Mine used to like 16 initial, and had 16 mechanical on top
with that cam, from memory.
Don’t know how early it came in though, had no idea about it back then
Funny how the xu-1s , your professionally curved one , and the popular
Efi black dizzys all hit maximum advance after 5000 revs
I the other school of thought of getting advance in by 3000 - 3500 or
even sooner seems just as common..
Looks like I will have some more questions to ask and more experimenting to do.
Like you said, the smart money is on a dyno session to get the most out of
what you got, I suppose.
Cheers, mate

[73TORANA!]

Yeah I hear what your saying, I dont know enough about that side to make a judgement whether 3500 or 5000 is better.

Pitty your not in Melbourne we could put yours on the tester hey.

Cheers.

[Bruiser]

Yeh, sounds like a good time, that
distributor graphing machine and beers
If I ever find myself near Melbourne I’ll give you a hoy
We can talk car shit and bore the girls
I can see what my timing is doing on the balancer to map the curve,
it has marks on it going up to 50
tacho, graph paper and a pencil
If you’re going to do something,
might as well do it the hard way
You’ll soon have dozens of new mates with a toy like that

[73TORANA!]

Hahaha 1005

[73TORANA!]

100%

[Bruiser]

1005%

[claysummers]

Interesting topic and read there, thanks Geoff and Bruce. I've been hearing the all in by 3k or so dogma for a while.

A feller on the Humpy forum has a fully programmable dissy in his injected grey motor. It got me wondering......



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[Bruiser]

Hmm yeh Clay, all that adjustability would have to be the ultimate for getting it right.
Like Geoff said, he had his on the dyno and found out what his liked.
That is the only way really, so far I have been playing a guessing game
as far as the target numbers to shoot for goes
Silly to spend so much on go fast bits and then not have it fine tuned.
Improvements can be noticeable using seat-of-pants technology
but I’d still never know if there was some more to be had

[73TORANA!]

So you guys got me thinking more about the all in by 3k thing.

Dont forget mine has a Vac advance of about 8 deg and 11:1comp.

I fitted a dizzy vac leak tap to see how much it effects light loads, cruise and medium throttle applications and it is very noticeable and feels sluggish with out it so not using vac then yeah it would like a lot more early, ( in my case ) I guess thats why Schorcher asked if I used it.

 

For what its worth I had a look at my Toyota 86's timing map for curiosity, comparing apples and limes and it has a gradual increase then backs off up top ( heavy loads), but it does seem to peak at around 4800 under heavy loads but keeps going up under light loads; simulating vac advance ??

 

Mind you its 12:1 comp direct injection and a lot more cams and things.

On the base timing table RPM on left, engine load across the top.

Engine load of say around 0.4 is idle, cruise at 100kph is 0.5 and flat out is 1 to 1.2 so at idle its around 16 deg

 

Note everything from and including load of 0.5 to 1.4 has a knock correction of 6 deg (2nd table ) that is added to the base time table from 800 to 7600rpm. 

 

So at 4000rpm at an eng load of 1 (WOT) its 20.62+6=26.26 total advance ( base time +knock correction = Total)

 

Timing gets pulled from the knock correction table if it pings.

I know its modern tech with no points but interesting I think.

Cheers

 

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[Bruiser]

Good on ya Geoff, and thanks
That table is interesting, I reckon I might learn something if I scratched my head over it enough
Goes to show just how much better it could all be tuned using that setup
Is that one a custom mapped thing or as the factory had it?
I’ve never even looked twice at those, “no laptop’s ever coming near my car” hah

Found a few boffins on speedtalk debating this, a few of them swear having mid 20’s or so
around the peak torque rpm and rising to max degrees around peak hp is the way to go
Hmmm the plot thickens

[73TORANA!]

Hi Bruce,

The knock correction table is simplified down to just the one number I.E 5.98 deg but it comes into effect at 0.5 load on wards the same as the stock table; I.E no correction factor below 0.5 load.

The factory correction table numbers are all over the place meaning more timing can be pulled in certain areas.

As the custom table only uses a correction of 5.98 is way easier to work out total adv when modifying the Base time table.

 

Mid 20's around peak tq..... my timing is in the mid 20's, between  from around 3300 to about 4500 and actually that is in the max tq window for the std xu1 cam in my set up.

Interesting, and down the rabbit hole we go hahaha

Cheers.

[Bruiser]

Yerss, that did remind me of your numbers
Looks you’ve already caught that rabbit, you’ve had your dizzy done by one of the big name mobs
who do this for a living, AND had your car on a dyno
while I faff around in the shed playing diy
I reckon I could alter my curve in that direction, and I think I will have a go, eventually
A couple of spring changes and tweaks would get there.
There’s a guy not too far from me here in Adelaide who does dizzys,
Was thinking of giving him a call to get his opinion
He might not want to give out his secrets, and I wouldn’t hold it against him either
But you can only try

[claysummers]

A feller I spoke to at Paralowie sent his off to Victoria. Would that be scorcher?

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[Bruiser]

I think Frank from the old Pro Action spares shop operates on Stanbel road Salisbury
Not sure if he still does carbys

Ah, yes Holley specialist as well

Edited by Bruiser, 09 July 2024 - 08:34 PM.

[73TORANA!]

A feller I spoke to at Paralowie sent his off to Victoria. Would that be scorcher?

Schorcher is in Nunawading vic, not sure of the guys name. A couple of old duffers run it. I think there are a couple of places in vic. I was to them recommended by a friend that races.
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Edited by 73TORANA!, 09 July 2024 - 09:06 PM.

[claysummers]

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[Bruiser]

Did you ever ask your mate Glenn how his is set up, Clay?

[claysummers]

Crank trigger Bruce. So I think it is fully programable somehow. At one stage he offered me a GM, I think Delco one with the coil in the cap. They are easy to vary the curve apparently, without even removing it from the engine. It is in his mate Red’s HZ now. I should have acted sooner…..


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[yel327]

Those are cheap as chips on Ebay Clay.