MicroSquirt.com read only forum (Jan.15,2018)

G'day all, long time watcher, first time poster

I have injected my 88 GSXR 750 and just want someone to help confirm ignition set up.

I have a 36-1 trigger wheel.
The Vr sensor was used by suzuki as the TDC mark for N#1 cylinder so i have the trailing edge of tooth 9 after the missing tooth timed to TDC.

I have set megatune as follows follow's.

teeth N# 36
missing 1
delay 8 (as the signal tooth dosnt get counted)
skip 18
Falling edge (as is timmed to trailing edge of tooth)
calculated cranking

All this is fine i think but i am struggling with trigger offset. Because my VR pickup is at TDC anyway is my trigger offset 0 or do i have to take away from 360 my expected maximum advance of say 40 to give me say -320.
I have searched and read as many post's as i can find and still cant find any clear answer.
People seem to use it in different ways, varying from the relationship between the missing tooth and the spark event and others being the difference between TDC and where the pickup is at TDC.
I have yet to try starting and really wanted to get some clarification on this as at the moment i have it set at -270 deg.
This being because, looking at the manuel and its description of the difference between tach events minus timing.
I took tach events as missing tooth and timing as where my TDC was in relation so did 90 - 360 which is -270 but i think after reading more posts this is wrong and as my TDC and VR possition are the same it should be 0 or close to it.

Sorry for the ramble and all help much appreciated.

Cheers

Slingy

I would use Delay Teeth = 9 and -10 deg (1 tooth ATDC) as the trigger offset. You want to start the first tach cycle after TDC. But you could also use Delay = 8 and trigger offset = 0 deg. Either one should work fine, but Delay = 9 would allow you to use a few deg ATDC for your cranking timing.

Thanks for the quick response Grippo

It fired straight up at 8 delay and 0 offset but i will play with the 9 and -10 t see how that goes.

At the moment its fires straight away so starting is good , just runs for a few seconds and then dies but at least it goes

Cheers all

That is good news. Then stay with 8T delay and check if it is losing synch and dies, or the engine is dying and therefore running very rough and causing loss of synch because the wheel is slowing down to very low rpm. The way to tell this is to datalog while trying to keep the engine running as long as possible by keeping the throttle open and maybe squirting in fuel. Then look at the datalog trigger +/- column. If this is counting up or down or both all over then it probably means there is VR sensor noise or wrong VR polarity. If trigger +/- is steady and only counts after the engine starts dying and reaching very low rpm, then that indicates you probably just need to adjust the after start and warmup fuel.

Ok, i will look into this next time i get a chance.

And thankyou very much fr the advice, its much appreciated.

Cheers

Slingy88