Nistune Forums

hey guys im finally working out all the bugs with my setup this year but this is the one thing that is haunting me and making it so annoying to drive my car. heres the deal....

with my rb25det, DW 740cc injectors, gt35r set up, with z32 ecu and type 2 board i have a pretty decent tune on it, its idling nicely around 14.7, cruises afrs are good, under boost its good. except for starting, mostly when warm..

during the first start of the day it usually always fires up on the first crank, takes about 2-3 seconds maybe a little quicker if i touch the gas pedal while cranking.

anyway once the motor is up to normal operating temp the thing is so hard to get started back up. say i shut it off for literally 5 seconds, 5 minutes, 1 hr. its always SOO hard to get it fired back up. i usually have to try cranking it over 3-5 times and i never let it turn over for more than 5 seconds when turning the key. sometimes it will fire but won't catch enough when i let go of the key for it to run on its own. 90% of the time i HAVE to pump or open the gas pedal for it to fire as well.

im really stumped here as i have tried different mafs, different ecus, i NEVER had this problem last year when the motor with stock on a stock RB25 ecu. my entire electrical system has been checked out by me and friends and everything seems to be fine, its got a new battery, new alternator, grounds have been added. cleaned, inspected. im really just narrowing it down to something with the ecu and i cannot figure out where to start. if anyone has any help that would be greatly appreciated becuase its a huge pain, esp at the track while drifting say i spin out and the car stalls. it takes me 30 seconds to get it to fire up and makes it unpleasant for other drivers who are waiting for their run. help me fix this problem please! would be so nice to have a perfectly running motor and this is the only thing stopping me.

what kind of values do you have in the 'first/after start enrichment' tables ?

for first time its
deg- value
20 - 10
30-7
40-6
50-5
60-4
and all up its 4

for after start its
30-51
40-38
50-24
60-10
70-6
and the rest is 6

looks normal,

what values holds your first TWST ( first time enrichment PW) table ?
for 740cc's it should be similar to this from 20 celcius and up: 8,5,4,3,3,3,2,2,2,2

not sure what you are asking for. that was the value i posted for first time enrichment

Is idle control system performing as it was? inspect/test/check/etc.

has it been setup as per service manual? (if relevant)

Possibly choking the motor which is making it easy to fire when cold and
harder to start when warm.

Could still be an injector sizing or latency issue, even if AFR's seem right at idle the mixtures can be a few points too rich as readings are greatly affected by large exhaust pipes or lambda near bends or even very close to tail pipe.

ursin wrote:not sure what you are asking for. that was the value i posted for first time enrichment

I think...
What Eric asking is if your First time enrich table (crank start enrichment) is not well tuned, you might have this problem.
Try doing this, adjust this table accroding to the coolent temperatue (suppose your engine does not have another problem),
Stop your engine at the hard start temperature , and try to crank start again, subtract the number in the same temperature cell if you smell unburnt fuel on your exhause gas, increase if no unburnt fuel. if no starting problem on that temperature, keep your engine running to the next temperature cell and do it again, finally you will have your own table and can start easily on whatever temperature.

never thought of doing it that way Louiswun....

Also...

... it's always best to change a bunch of values rather than just one cell. Particularly when you're just poking around trying to see what works and what doesn't. So choose the value it's sitting at and select 1 or 2 cells either side of it as well - then hit the +/- keys. The ECU's usually interpolate across multiple cells, so adjusting 1 cell won't usually make much difference until you get radical with the values.

Just something I've noticed during bench testing...

PL