LT-8S and LS coil question
 

hi everybody

is been a while since i'm been around tuning rx7. well i'm finally back on my rx7 after 3 years and i have a lt-8s programmed to used on stock coil setup. i have msd coil with stock leading igniter and stock trailing and is been reliable but i want switch my ignition to LS1 coils and i'm just wondering if is posible to use them without replacing the ecu and if so what would be my options?

thanks
Eddie

if programmed for stock coil ( waste spark leading ) then it needs to go back and be flashed to be fullt sequential ignition



sucks to have a microtech,, and want choices

i know, well i keep it the way i have it. thanks

eventually you find a point where you blow out sparks and you wish 4 coils and sequential operation
this is to double the width of the window of dwell at high revs and allow you to increase the coil charge period

those of you with waste spark leading ecus have only the option to go to a CDI leading ignition
this will improve things at revs.. but may cost a little down low
( where mazda put all that effort into getting a long duration spark.. and you have removed it )

How aggressive can you raise dwell on a lt8 that uses the stock fd ignitor instead of x4 box. I know Kilo Racing in florida years ago told me not to raise dwell any higher then 3.50ms or x4 ignitor box usually burns up. I installed a haltech sprint re on a fc early this year and noticed that dwell on a base map for a T2 by default is 4.00ms. So my question is how much can you raise dwell on wasted spark. I would assume you get a better spark with a higher dwell and better performance on top end.

Im running a LT-8X and I have some LS2 coils around the house. I can use the LS2 coils with the LT-8X by somehow disabling internal igniters on the LS2 coils?

the 3.50 ms limit in wastespark leading engines was not there to protect the igniter or the coil

at 9000 rpm there is 6.66 ms between each peak compression event

in wasted spark leading .. that means 6.66ms to fire twice
in a 4 coil sequential ignition ,, that means 6.66ms for one fire

if you account that the spark event itself may take up to 1 ms to discharge

then running a wastespark leading ignition with more than 3.33 dwell
is not going to get a full charge on the second spark
and it will be cut off and sent early at part charge

as is, many coils will take more than 3.5 ms , i run my ls1 coils at 4.5 ms
and yes,, there is a point where saturation of the coil goes too far and the igniter can overheat or the coil split
many brands of igniter may have a trip to protect against over current / overheat

but if stuck with wastespark leading then you need to find a COP coil that gets its saturation at around 2.0 ms dwell and still has 90 + mJ of spark energy

or go for a CDI setup.. which can run down to 1 ms of dwell and still get full spark

note,, that your trailing is also now condemned to that low dwell.. and probs needs a couple of CDI channels there itself

a bit OT but-

in the LTs programmed as 4 coil sequential and wishing to drive stock coil setup
( 3 igniter setup )
then hooking both the positive wires to the one coil with a stock dwell wont initially work
as the dwell period that starts on each igniter wire will overlap
.. thus keeping the coil in charge and never letting it fire

if the dwell period is reduced to 1 ms ( and the coil using a CDI unit )
then the overlap no longer occurs till extreme revs
and essentially, your 4 wire programmed ecu is driving a 3 wire coil setup

however,, you now need CDI units at the trailing side too
( as it too is subject to only 1 ms charge )

and in the end it would have been far easier ( and cheaper ) to have just wired up four individual coils


just dont blame me for your microtech shitiness and non user adjust features
as i have been pointing them out more than most , for years

if you are in the market for a new ECU,,
look elsewhere at more capable choices that have user adjust of config,, free firmware upgrades and true internet program exchange


the LTC still falls far short of the mark set by others a decade ago

nope


you need dumb coils . suggest 1GN-1

i understand, i have a msd 6a on the leading that i forgot to mention. and like i said, is been super reliable. i blew the engine 2 years ago due of over heated spark plug, i was using the wrong heat range for the king of power i was making and i'm getting it back together again and i thought about changing the ignition for something more cleaner. but if it involve re flash of my ecu and possibly a x4 i might have to pass for now.

Thanks alot. :icon_tup:

Bumpstart, in one of my previous threads, I asked this question regarding an LT12s and LS1 coils. You stated that the LT12s could drive coils with in-built igniters or standard/external based coils. It was simply a matter of setting in setup menu 31.

Why is this different for the LT8s?

the LTs 8/10/12 has no inbuilt igniters

..and it will drive dumb coils,, via the x box igniter pack or via a s6 igniter, or another multichannel igniter

else it will drive the ls1 or ls2 coils or stock coils or others ( with inbuilt igniter ) directly

it must however ( despite the S for sequential ) be ordered in either three trigger or four trigger mode from the outset
,, and this is factory locked
( ie.. 3 igniter mode is wastedspark leading for stock coil setup and 4 igniter channel mode is for direct fire sequential )

see note above about running four trigger/channel setup on the three coil config //
it can be done .. it is not practical.. and it will hit a window at revs where the leading will stay in dwell
and the microtech factory and the postman have you over a barrel if you wish to have it reflashed

so dont blame me as i do my best to put you to a haltech or adaptronic for exactly this jip

it is forever my albatross to be helping microtech users
not cause i like the ecu ( far from it )
but because it lacks factory and forum user support and i have a fair bit of exposure across all the models
( cause all the rotor heads here in my closed market are sheep,, and have no real idea how backward and limited this brand is compared to others )

while there is lots of misinfo out there, i do my best to set people straight and one or two times it has been misinterpreted by cherry pickers and wishful thinkers

of all the microtechs only the LTX model has its own inbuilt igniters and that must be wired to dumb coils only

screen 31 config allows you to alter the dwell period and alter the input trigger polarity
( ie.. stock FC coils and ls2 coils often have a different input trigger edge to the norm and it will need to be altered for ls1 and others )

I understand now. Your input into the microtech forum is very useful. Hindsight, I wish I had gone Adaptronic. I purchased my ECU used along with 6 LS1 coils. Hopefully, its been flashed for direct fire mode, which would make the most sense considering it came with these coils. Otherwise, I will sell this product and switch.

Thanks again

FC and LS2.. rising edge trigger

LS1 = falling edge trigger