Autronic Sm4

[roba]

Ive just finished my RB 25/30 build and plan to run a Autronic SM4 ecu. Aiming for 350rwkw as this stage.

Im not sure what the best road to take is regarding the ignition system. As far as I see it I have 2 options:

1) Replace problematic coils with splitfires and hope they run well for ??? years.

2) Buy a Autronic CDi unit and associated coils.A far superior setup however, as far as im aware the 500r

has only 4 outputs so have to run wasted spark. Which is not ideal?

Any ideas or alternatives would be appreciated.

rob.

[Swiper the Fox]

Ive just finished my RB 25/30 build and plan to run a Autronic SM4 ecu. Aiming for 350rwkw as this stage.

Im not sure what the best road to take is regarding the ignition system. As far as I see it I have 2 options:

1) Replace problematic coils with splitfires and hope they run well for ??? years.

2) Buy a Autronic CDi unit and associated coils.A far superior setup however, as far as im aware the 500r

has only 4 outputs so have to run wasted spark. Which is not ideal?

Any ideas or alternatives would be appreciated.

rob.

i run splitfires with HKS amplifier...very good

[Adriano]

Wasted spark is also fine, thats what ill be running on my 26/30

[roba]

Id perfer to go the splitfire route without an amplifer as it is much cheaper.

I know they will be fine up to 350rwkw but if I go further in the future - say 400rwkw will they still be fine or would I be better off with a different ign system.

I want to do this once and do it right... the cheapest way possible.

cheers

rob

[Adriano]

Youll have to factor in the cost of the ignition multiplexer to run the splitfires if you dont want to run them in wastespark, as the SM4 only has four ignition outputs

[battery]

dose anyone have a reason why a Wasted spark setup is bad?

[FATGTS-R]

Like adriano said if you get the autronic cdi or not it only has 4 ignition drivers. The multiplexer will give you six if you wish.

I run an old autronic smc in wasted spark and cant tell any difference from a sequential setup.

[2BNVS]

i use autronic cdi with my SM4 its great i luv it, was running 375rwkw previously with smaller turbo, hoping for mid 400rwkw's with the new set up

ben....

[shanef]

the new plug and play autronic Sm4 has the extra ign outputs required so u dont have to spend the extra ~175 for the expander

on topic. the autronic cdi and some mercury coils would be the bees knees (without going to an M&W cdi lol). That combo is going to cost you near on 1400. (get the coils from ur local motec dealer)

[roba]

on topic. the autronic cdi and some mercury coils would be the bees knees (without going to an M&W cdi lol). That combo is going to cost you near on 1400. (get the coils from ur local motec dealer)

I agree, but you still have to run wasted spark. Numberous people say its not good, any may more say it fine. I personally have tryed it and found I had to reduce my spark plug gap from 0.8 to 0.6 to stop missfiring. I wasnt impressed and switched straight back to std coils.

Wasted spark with 500R CDi would be a different story altogther id imagine, but as u say the cost is getting a bit out of my league. (when i first posted this thread a mate had one for sale cheap... but it has now gone

I be running RB plug and play SM4 which comes with 6 channel multiplexer. The easiest option for me is to combine this with some splitfires if people think it will do the job...?

Edited December 23, 2007 by roba

[Adriano]

the new plug and play autronic Sm4 has the extra ign outputs required so u dont have to spend the extra ~175 for the expander

on topic. the autronic cdi and some mercury coils would be the bees knees (without going to an M&W cdi lol). That combo is going to cost you near on 1400. (get the coils from ur local motec dealer)

But unfortunately the autronic cdi is only 4 channel, so to do a direct fire cdi is mare like $2600

PS how much are you getting the sm4 P & P for?(PM me if you like)

[shanef]

But unfortunately the autronic cdi is only 4 channel, so to do a direct fire cdi is mare like $2600

PS how much are you getting the sm4 P & P for?(PM me if you like)

ahh yes i forgot about that!

well then that makes the M&W + mercury coils cheaper

[Adriano]

Im running a MSD dis-4, and 3 M&W double ended cdi coils, fat as spark, only about $800

[roba]

PS how much are you getting the sm4 P & P for?(PM me if you like)

Their seams to be only one distributor here in NZ, he has quoted me $2,650 plus installation/tuning costs.

[Warpspeed]

Numberous people say its not good, any may more say it fine.

Wasted spark works fine with standard cams. If you are planning to run some fairly radical aftermarket cams, and very high boost pressure, you may have problems.

Try to imagine what happens if the intake valve opens at say 35 degrees BTDC to very high boost pressure (air + fuel) then you fire the spark plug ten degrees later with the intake valve still open. If you can figure out what MIGHT happen, you will begin to understand the problem.

Guys with the original factory cams will have the inlet valve opening only a very few degrees just before TDC, long after the plug has fired on the exhaust stroke. The cylinder will be full of exhaust gas only. These guys say wasted spark runs fine, and they are undoubtedly right.

Nothing really wrong with wasted spark on the right engine. High boost and big cams are not the right engine. Even GM run wasted spark on the supercharged Holden V6, but only with a wimpy emissions cam. Put a big cam in it, and have the potential for some interesting effects under boost.

[DCIEVE]

Wasted spark works fine with standard cams. If you are planning to run some fairly radical aftermarket cams, and very high boost pressure, you may have problems.

Try to imagine what happens if the intake valve opens at say 35 degrees BTDC to very high boost pressure (air + fuel) then you fire the spark plug ten degrees later with the intake valve still open. If you can figure out what MIGHT happen, you will begin to understand the problem.

Guys with the original factory cams will have the inlet valve opening only a very few degrees just before TDC, long after the plug has fired on the exhaust stroke. The cylinder will be full of exhaust gas only. These guys say wasted spark runs fine, and they are undoubtedly right.

Nothing really wrong with wasted spark on the right engine. High boost and big cams are not the right engine. Even GM run wasted spark on the supercharged Holden V6, but only with a wimpy emissions cam. Put a big cam in it, and have the potential for some interesting effects under boost.

seem unusual then that there are quite a number of rb's running aggressive cam profiles and autronic cdi (4ch) without any issues...

[Warpspeed]

seem unusual then that there are quite a number of rb's running aggressive cam profiles and autronic cdi (4ch) without any issues...

It is not unusual at all. As I said earlier you can sometimes get into trouble with waste spark, but not always. It depends on what you have.

I only offer this, so the smarter people can think a bit more about what actually happens during the second plug firing at the very end of the exhaust stroke.

If you do not care, well neither do I, it is your engine.

[SirRacer]

mitsi evos run wasted spark standard dont they?

thats enough info for me to stop worrying

im going to be running 3 mitsi evo coils with a 3 channel ignitor on a computer with 4 outputs simply to save a bit of cost. the tuner whos tuning it has an evo running 430kws atw on .8 plug gap. seems ok to me!

Edited December 28, 2007 by SirRacer

[Adriano]

Warpspeed, i was wondering if you have any more imformation on this problem with wastespark(ie where you have seen it occur)

I would have thought blowing back through the inlet valve would be most likely to occur at idle, as there is the least amount of ignition timing out of the whole map there. I also would have thought it would be far more prevalent in a N/A motor, as they have far more overlap and duration. Looking at this, would indicate that this camshaft selection would have the problem, as the inlet valve is defiantely open when the sparkplug fires, and this defiantely isnt a big cam, however the fact that the piston is still rising means that i can only conclude that there cannot be any scavagening, and no A/F mixture entering the combustion chamber.

I think the only reason the inlet valve starts opening BTDC is so that once the piston starts to decend, the valve already has enough lift to allow the A/F mixture to enter. One car i built years ago that would be most likely to have this problem was a V6 commodore that made 240RWKW with N20 N/A, it had wastespark with multiple spark discharge(which could only make it more likely to blow back) and a camshaft duration of over 300deg which is far more than almost all turbo motors??

[DCIEVE]

But valves open, no compression... piston speed at its lowest not to mention we consider 270deg dur as aggressive like adriano points out

be very interested if people have had problems at this level?