Staging 550/1600 injectors
 

Staging 550/1600 injectors

I have an LT8S, and I’m running a street-ported 13BT with a GT35R turbo, 550cc primary / 1600cc secondary injectors, SX FPR set to give 40psi, large Bosch fuel pump and an Apexi GT FMI/C.

I’m having problems with injector “staging”. I have read the ‘sticky’ threads about Microtech staging and understand how it is supposed to work. But in practice, my current setup of 550/1600’s is proving very difficult to tune. Has anybody else had problems with staging 550/1600’s?

I‘ve attached a WORD Doc that has screen dumps of my PLX Datalogger charts and LT8S Fuel/Ignition Maps, if anybody wants to comment on them. Note that I have to post these separately as there is a 100K limit on file attachment size in this forum.

If anyone has a similar setup to mine, could they please PM/Email me with some info on their maps?

Here’s the problem in detail:-
I set Staging values at 2000rpm, -12”Hg, and 99% (I’ve tried other combinations too but this seems to be the best I’ve found so far).
At the point just before staging, approx. -15”Hg, the AFR is climbing up to 14. The primary injectors seem to be struggling to supply enough fuel here. I have tried increasing the fuel values around here, but this also has the knock-on effect making the gradient of the fuel curve very steep. This causes problems because the fuel values need to be much lower when the secondary injectors start firing at -12”Hg. If I try to keep the pressure between -15”Hg and –10”Hg, first the engine splutters (AFR rises to 14+), then it bogs down (AFR drops to 9) as the secondary injectors wake up. I’m left wondering whether these injectors are opening too slowly! What is the average opening time for the 1600cc injectors? Or maybe the LT8S starts firing them too late ie. when they’re at –10”Hg instead of –12”Hg! Has anybody had similar problems staging with 550/1600’s?

Thanks,

Adrian

Staging 550/1600 injectors
 

here's the 2nd PLX Log

Staging 550/1600 injectors
 

here's the LT8S LOAD map

Staging 550/1600 injectors
 

here's the LT8S WOT map

Staging 550/1600 injectors
 

here's the LT8S RPM Cruise map

I've been told that 550/1600 is too large of a gap for the LT8's to manage smoothly without at least a little hiccup.

Smallest he recommended was 750's.

I am running 550 and 1600 and have no problems at all... Had to drive on the street and lean out some areas in the cruise maps to perfect any hesitation of the 1600's opening after we dyno tuned.. G

Have you tried the staging around 3000 and 0psi? I got it there and its just a hiccup when they hit. Its really not that bad. Although I have the gslse secondaries as my primaries which gives me a 700/1680 combo.

I am having the same problem, its like hitting a brick wall at 4k, and sputtering. I am pretty sure it has something to do with the pump functions, so I played with those, but I think I made it worse, because now I am just blowing flames. So yea if anyone has some maps they could share with us, that would be great. thanks

87 tii
Cosmo 13b-re
550/1600 combo
60 trim turbo
1:1 FPR @ 40psi
3" exhaust.

injector combos
 

RE: "I am running 550 and 1600 and have no problems at all... Had to drive on the street and lean out some areas in the cruise maps to perfect any hesitation of the 1600's opening after we dyno tuned.. G"

G, Is there any hesitation at all when the 1600's open? You must have a good map. Any chance you could PM me with some Map screen shots? I'm going to post the remainder of mine.


RE: "Have you tried the staging around 3000 and 0psi? I got it there and its just a hiccup when they hit. Its really not that bad. Although I have the gslse secondaries as my primaries which gives me a 700/1680 combo."

Crusader, I've tried staging at 2500 and 0psi before, and it just seemed to make the problem worse. On part throttle, the AFR kept climbing to approx 15-16 until the 1600's finally kicked in and then just bogged the engine down at AFR 9. It seems like the 1600's have a delayed reaction / slow response! When I floor the throttle at 3000rpm they kick in straight away though.


RE: "I am having the same problem, its like hitting a brick wall at 4k, and sputtering. I am pretty sure it has something to do with the pump functions, so I played with those, but I think I made it worse, because now I am just blowing flames. So yea if anyone has some maps they could share with us, that would be great. thanks"

Rex, I'm going to post some more of my maps here. My LT8S Pump maps seem fine, its just the 'staging' / Load map that have problems. Have you got a wideband (AFR) sensor / meter to tune with?

Thanks,

Adrian

LT8S Maps
 

Here's my IDLE map.

LT8S Maps
 

Here's my t_rpm map. (sets timing at each rpm point)

LT8S Maps
 

Here's my t_map map. (sets timing at each 'Load' point)

LT8S Maps
 

Here's my t_gap map. (sets timing diff between primary and secondary ignition firing)

LT8S Maps
 

Here's my t_inj map. (sets time delay, in degrees, before injectors fire). Has anybody modified this map? I left it as standard.

AFR log
 

Also, here's a log of AFR at WOT from 3500-8000rpm. AFR in 11-12 range.

It sounds like it is too rich. I have mine set at:

%stg - 99%
rpm - 3k
vacuum - 5hg

The trick is to lean out the rich points.

87 TII
13b-re
550/1600
T66 BB
Aeromotive FRP at 40
3" exh

well from what adrian is saying its leaning off . first you need to listen to the boys and stage at around 3000 and 0 hg it depends on how big is your turbo and soon you hit boost, you dont need the 1600 under 3k rpm and you dont need them if you are not hitting boost . mine stages at 3k rpm and 2psi .
your injection ms will go up to around 6 ms before the 1600 open and it should drop immediatly to about 2.8 ms when the 1600 kick in. now remember these are rough numbers and you should have your wide band ready when you tune

Yes, Adrian seems to be running lean. I was referring to RexRyder's post when I mentioned running rich.

yea, I had it setup 3k rpm stage and 2 psi. but then the primaries get to 12st, and it reads max duty when datalogging, then drops down to 6ms. that stage was perfect for when I had 720 primaries, but 550 not sure.

staging
 

I think I'll try staging at 3000rpm and -5"Hg or 0"Hg, as that seems to be the way people are going. I'll get the throttle maps, and post those too.

Thanks,

Adrian

LT8S Pump Maps
 

Here's my Pump maps:-

Pump1 ammount +5%
Pump1 pulse +02
Pump1 trig +14
Pump1 stop 0"Hg
Pump2 start 2000rpm
Pump2 ammount +30%
Pump2 time +10
Pump2 trig +16
Pump2 stop 0"Hg
Pump 1 ADV +05
Pump 2 ADV +05
Pump cold 0%
Pump dwell 3.50

These work well with the rest of the LT8S Maps on my FD, although I might try lowering the Pump2 ammount to 15-20%.