boosted ignition problems, and fixes

[1slickRED89]

after trying narrow gap (.025") and finewire plugs and still having 'blow out' problems, I decided something else was wrong with the car, it sees about 5 PSI of boost.

I set up a bench to test the DIS, coil pack and high voltage wires. this is what I found out. at about 12 KV (~60PSI air pressure) coils 1 and 3 would run out of voltage whereas coil 2 could go up to 25 KV (150 PSI).

I swapped DIS modules with two different 2.3 DP DIS (same as SHO but with 4 coil drivers) same result. tried using a different coil (2.3 DP 2 coil), and BANG, 25 KV. so I think 2 of the three coils are bad, although the resistances are in spec.

will try the same test with a new coil pack (wells?) and see what kind of voltages I can get out of it. I wanted to see 45KV so either my scope is setup wrong or there is another problem.

whats a story without a pic. plugs 6 and 7 are not connected. it may be hard to see but only plug 4 and 8 are firing (coil 2) at this pressure, the other two coils ran out of a55.

pic

 

[1slickRED89]

new $67 coil and still have the same problem. I only get 30 KV out of two of the coils and 50 KV out of the other, (15 KV and 25 KV at each plug respectively)

so I tossed a current probe on the coil primary wires and it looks like two (the same two that have low voltage) of the primary currents don't saturate the coil (2-3 amps vs 5.5amps). I tried three DIS modules and they all have one coil with more current than the other 2. WTF.

I guess that's enough for it to run at idle and at N/A cruise speeds, but get into some boost and it really needs all the primary current it can get.

any Ideas?

 

[Revere sho]

huge shot in the dark but would MSD igniton help? or any thing form MSD ignition?

 

[sho_sc]

At the levels of boost that I run, any A/F ratio greater than 10.5:1 the flame kernel blows out ... falls flat on its face ... and I run a MSD with a "top secret" extreme high voltage coil pack (only 2 that I know of) ...

 

[1slickRED89]

At the levels of boost that I run, any A/F ratio greater than 10.5:1 the flame kernel blows out ... falls flat on its face ... and I run a MSD with a "top secret" extreme high voltage coil pack (only 2 that I know of) ...

is the amount of boost you see secret too? that's really a disconcerting post as you still can have problems and obviously have a well preped car.

I build a heavy gauge wiring harness to run this system on the bench tester and will try it out on the car, maybe triggering the DIS the way I did confused it and the real CKPS will somehow trigger it better. for refrence, I used a 1.5volt, 60 hz square wave (sine would have worked too) with 50% duty cycle on the PIP and spout.

 

[sho_sc]

if the A/F ratio bottoms more than 10.5:1 and I'm seeing 12+psi , then it falls flat and/or miss. Copper core plugs gapped at 0.32".

The coil pack I use, I am under contractural obligation not to discuss.

 

[1slickRED89]

I see, if your richer than 10.x:1 it misses. i thought you meant if it was leaner than 10.x:1 it would miss, and I was confused.

I have heard that's due to fuel droplets shorting the spark gap when it's super narrow and the AFRs are very rich. anyway, I tired to program lean and it looks like I'm around 13:1 when it firsts starts to noticeably cut out, around 4K rpm.

 

[1slickRED89]

looks like my coil pack was *mildly* miswired from the start.

there appears to be a number of publications with coil pack wiring *different* between the SHO and SC 3.8, but really the plug is just turned 180 degrees.

Apparently, the car will still run with +12 on coil one and primary wires on the rest. all better now.

proper coil pack wiring

Firewall<--->coil 1---coil 3---coil 2--- +12 V<--->front of car.

DIS wiring for HD wires:
top
ignition diagnostic monitor (really handy. if it's not blinking, your misfiring )
coil 2
empty
coil 3
coil 1
IGN grd
bottom

what good and bad primary currents look like. the two small ones are due to the miswired coil pack. I would expect all three 'bumps' or 'dips' look like the third one now.

 

[1slickRED89]

still blowing out. looks like it's time for plan B, this will get ugly. two ignition systems in a coil per plug config.

 

[sho_sc]

at A/F of 13:1 and 5 psi boost (stock piston compression?) are you sure your not detonating? OR which fine wire plug are you using? and are they gapable??

 

[somedude_001]

i thought most of the boosted SHO's are running stock ignition without a problem.

also 1slickred89 you have a pm

 

[twr]

i thought most of the boosted SHO's are running stock ignition without a problem.

also 1slickred89 you have a pm

Most are. I running 10psi with no ignition problems. Hope you get it figured out. Off the top of my head, I can't think of anything that would cause a spark problem, other than the usual suspects (wires, coil and plugs)

 

[yamahaSHO]

I was running 11 PSI with stock ignition and plan to run stock ignition with 13 PSI. Pat is running stock ignition on both his cars, so I'm certain I'll be fine.

When I went richer that 10:1 here's what happened...

http://download.yousendit.com/182DA0725BB53A18

This video was taken the first night I had it supercharged. We were playing with A/F ratio's and since it was raining and the MAF was 8" off the ground, we initially thought that might be the problem. When we watched the WB display show "rich" (richer than 10:1), when dialed out some fuel.

 

[1slickRED89]

at A/F of 13:1 and 5 psi boost (stock piston compression?) are you sure your not detonating? OR which fine wire plug are you using? and are they gapable??

it's a stock 3.2L, but up to date on maintenance and compression tests OK. I have a device to alert of knock from the knock sensor, but I have to have a BOB installed to use it, so I took it out. when it was installed it went off once in a while, but I had a 17+ PSI WG spring in it then too. also, the knock sensor is mostly blind to knock over 4K regardless.

I have new 3924XP autolites gaped at .035" right now. I had the same plugs down to .025" and it was no better or worse. colder heat ranges foul out.

yeah it's weird that everyone seems to do very well with the stock components and I'm having such a hard time. either my car is super special or I'm doing something wrong. the wires are newish and have fine low voltage resistance(9-11kohm) and they did hold 40KV on my pressure bomb. also a new ignition coil didn't help, neither did a different DIS or heavy gauge (and correctly wired) primary wires.

pm replied too.

 

[twr]

also, the knock sensor is mostly blind to knock over 4K regardless.

Actually, that is not true. The knock sensor is not blind above 4k, it works just fine as it is looking for a specific wavelength of sound. I know somewhere on the internet it is says otherwise, but after talking with Gary M. about it, he indicated otherwise. One quick question, did you replace the plugs after you rewired the coil?? My 89' had a leaking fuel injector causing a mis-fire, after replacing the injector, the car still had a mis-fire until I replaced the plug.

Terry

 

[1slickRED89]

they are the same spark plugs, they where not carbon fouled and had OK low voltage resistance so I reused them. I do have some autolite racing plugs I want to try though.

I don't know about that knock sensor thing. This knock system, and it's computer strategy, are atleast 12 years old. some newer v6's have two active knock sensors, one at each end of the engine. I would guess that if one was even remotely workable, why spend the money to put on two?

 

[1slickRED89]

the experiment, six coil drivers

to drive six coils, I'll need six drivers. if it don't work, I'll just grab a new crossover tube and I'll be back to stock.

3 drivers *13.8 volts *5.5 amps = 222 watts of ignition power.

6 drivers *13.8 volts *5.5 amps = 455watts of ignition power.

 

[somedude_001]

maybe a different brand of spark plug? i'm wondering why your having problems when nobody else is. i wonder if your coil pack has a bad ground to the engine, have you cleaned up the bracket to head and bracket to coil surfaces?

 

[1slickRED89]

I measured .5 ohm between the bracket and ground on the battery, same on the DIS. I'm using autolite plugs, there is none better (but I might be slightly biased).

 

[Lance Cheney]

I measured .5 ohm between the bracket and ground on the battery, same on the DIS. I'm using autolite plugs, there is none better (but I might be slightly biased).

If it really were 0.5 ohm then that wouldn't be that great (using your current measurements: 5.5 amps * 0.5 ohm = 2.75V of loss, so you're really only seeing 11.1V to your components).

Luckily most multimeters are crap for measuring DC resistance, especially on the low end. If you put the two probing leads together do you get 0.5 ohm as well?

-Lance