Cranking fuel tables

[crans]

Having a lot of issues getting my car running ATM

Cranking it over and over it will not start. Changed plugs and car started. Old plugs were extremely black

This has just happened again so tonight i will attempt to clean the 0KM brand new fowled plugs.

Problems happening since upgrading to Deatschwerks 740cc injectors on my RB25 I have not been able to get it running nice.

How do I adjust the amount of fuel used when starting the car, I would like to actually tune the car rather than continually work on the same crappy issues.

Cheers for the help guys.

[PL]

Which ECU? Some have cranking maps/tables available. Some don't.

This stuff can be very frustrating to sort out when running big injectors because everything gets so critical. 740's should be fine - I've done lots of SR's with 740's (and one RB25 with 850's) and they behaved sweet. They were all OEM JECS 740's though - not the drilled out ones. I refuse to tune any car with drilled out injectors!!

PL

[crans]

It is an rb20 ecu from an R32 skyline. Running an rb25 in my R33 skyline.

Deatschwerks injectors are meant to be pretty decent and have factory like spray pattern

I found the cold and warm crank tables, are these it?

[PL]

Yeah, that'll be them. Give them a go and see if you can lean her out a bit while cranking. I don't have NIStune in front of me (I'm at work!) but from memory these tables are in % (not ms) and results are NOT reported via consult (which is weird). So go easy cos that % means 0 to 100% duty.

If you have no luck drop me a line and I'll do some bench testing to verify what's going on.

PL

[crans]

Thanks for the help. I have halved the values as my injectors are double the normal size.

40% of 370 = 148
20% of 740 = 148

Kinda makes sense to me.

I will put new plugs in tonight and do a test run

[PL]

Sounds like a fair approach. Getting this stuff right with big injectors can be somewhat troublesome. There are tables for cranking and tables for what happens for the first few seconds after startup too. Not all of these tables are known at this stage but we're getting there.

While doing some bench testing I found that some of them (different ECU families use different strategies) use cranking values first up and then the ECU interpolates between that value and the next table that's used after the engine fires. This can get quite confusing as you also have things like coolant temp and throttle position coming into play.

Fortunately these tables rarely need to be touched. And this is why information in this area can be a bit sketchy.

PL

[hudsontec]

Did you get your car straightened out?

[Matt]

RB20 tables are pretty much sorted. You will see during/after cranking which tables are used by the table highlighting feature added to the software

First time is used during cranking, and after start immediately after cranking

Cold/warm enrich are used based on coolant temp @ cranking. If < 15degC then cold, otherwise locks onto warm. Map highlighting reflects this also. I suggest make both tables the same when adjusting these. Some ECUs only have a single table and most ECUs have exact same valu for both tables

Temp enrich is used in addition both both cold/warm as another % on the total enrihcment, tapering to 0% adjustment when warm

[bachig24u]

while we are on the topic, as some tables are percentage based.
Does this mean they are not related to a change in 'K' and require adjusting based on the percentage change of the replacement injectors?

KR
Sime

[Matt]

Some adjust a percentage on top of K constant (eg based on temp)

However the initial crank tables dont use K constant (use a fixed injectin time and based on crank RPM)

[PL]

That's right- some are purely percentage based. I've seen this on the CRO while bench testing. So if you have a value of 10 that means the injector will be open for 10% of the cycle. Go to 100 and the injector will be on all the time!

Bottom line is to be careful with these tables. Go in small increments and always adjust a group of cells rather than just one.

PL

[Torque]

Does this mean I have to adjust these manually on Z32ECU as well?
On top of K?
(I don't want to drown my engine ...)

[PL]

Not sure on that one - would have to do some testing. Does it run OK?

PL

[Torque]

Have not installed them yet ..

Not sure on that one - would have to do some testing. Does it run OK?

PL

[BlueRB240]

Come to think of it my car gives me hell when ever I try to start it for the 1st time. 800cc sard top feed injectors on the RB20 ecu. I have to hold the throttle down when it's cranking to get it to fire up. I'm not 100% I'm getting a cold start signal even tho my friend that did the harness said he wired it up.