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FD LT10s help with bigger injectors

Old 06-27-14, 08:26 PM
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BC FD LT10s help with bigger injectors

Hello everybody.
I have a 93 FD R1 model, and I finally have my KG parts fuel rails installed with 850cc primary and 1680cc secondary injectors. Previously I was running the stock 550cc primary and 850cc secondary injectors. I have a mictrotech LT10s as well. I have not started the car up yet, as I am fairly confident it would flood with the old tune on it. Can anybody help me with a tune that will get it started?
From my understanding, I should only need to change the Load Screen, since everything else is based on percentages, and the %stage since the difference in flow between the new injectors is larger.
The current Load map for the old stock injectors is as follows
Load
Screen 3

30" ... 0.48
25" ... 1.00
20" ... 1.57
15" ... 2.14
10" ... 2.86
05" ... 3.62
00" ... 4.38
2psi ... 4.48
4psi ... 5.05
6psi ... 5.62
8psi ... 6.19
10psi ... 6.81
14psi ... 7.43
16psi ... 8.00
18psi ... 8.62
20psi ... 9.24

REVstg is at 3000
%stg is at 65%
MAPstg is at 05”Hg

If the current tune has the MAPstg at 05”Hg and the %stg at 65% does this mean that all the values from 30” to 5” have an extra 65% added to them, and only the primary injectors are firing over these values?

If this is true then for 30”Hg, currently at 0.48ms I would add on 65%, since the %stage is at 65% to get a total time of 0.48x1.65=0.792ms
Then multiply it by the flow rate of 550cc to get 435.6
Then I can work backwards and take that and divide it by the new injector flow rate to get a total time.
435.6/850=0.512
If the new %stg value is at 85%, then I would divide it by 1.85 for the new value with the new injectors.
0.512/1.85=0.28ms


In summary.
Old 550cc injectors at 65%stg with a time of 0.48ms
0.48x1.65x550=435.6
New 85cc injectors at 85%stg with a time of 0.28ms
0.28x1.85x850=440
Both calculated numbers are pretty close, so the overall tune should be fairly close, right?

Since my MAPstg is at 05”Hg then could all values from 00” to 20psi could be calculated the same way, but with the total flow since both primary and secondary injectors would be active?

Also, I believe I don’t have to worry about the difference in the injectors impedance, correct?

I apologize if this is totally off. I did not want to just ask for a tune without trying to learn the system first. This way I may be able to help others later on, if I ever get a solid understanding of it. I have been doing my best to understand the microtech, but am obviously still confused.
Any help as to where my thinking is off, or what other things I need to be mindful of would be greatly appreciated.

Here is a list of things that have been done to the car along with the microtech maps for the stock injectors, in case they are relevant.
3” exhaust
Power steering rack converted to manual
Power steering and air pump removed. (just running 1 belt for the alternator and water pump
Turbo’s in parallel
KG parts fuel rails with 850primary and 1680 secondary injectors
Apexi air intakes.
Wideband O2 sensor

Idle Map
Screen 1

30" ~ 1.38
25" ~ 1.33
20" ~ 1.48
15" ~ 1.81
10" ~ 2.38
05" ~ 3.14
00" ~ 4.05
02" ~ 4.95
04" ~ 4.95
06" ~ 4.95
08" ~ 4.95
10" ~ 4.95
18" ~ 4.95
20" ~ 4.95

Load
Screen 3

30" ... 0.48
25" ... 1.00
20" ... 1.57
15" ... 2.14
10" ... 2.86
05" ... 3.62
00" ... 4.38
2psi ... 4.48
4psi ... 5.05
6psi ... 5.62
8psi ... 6.19
10psi ... 6.81
14psi ... 7.43
16psi ... 8.00
18psi ... 8.62
20psi ... 9.24

RPMwot Screen 17

0500 ... +00%
1000 ... +00%
1500 ... +00%
2000 ... +00%
2500 ... +00%
3000 ... +00%
3500 ... +00%
4000 ... +00%
4500 ... +00%
5000 ... +00%
5500 ... +00%
6000 ... +00%
6500 ... +00%
7000 ... +00%
8000 ... +00%
9000 ... +00%

RPMcrs Screen 18

0500 ... +00%
1000 ... +00%
1500 ... +00%
2000 ... +00%
2500 ... +00%
3000 ... +00%
3500 ... +00%
4000 ... +00%
4500 ... +00%
5000 ... +00%
5500 ... +00%
6000 ... +00%
6500 ... +00%
7000 ... +00%
7500 ... +00%
8000 ... +00%
9000 ... +00%

Pump
Screen 19

Pump1 Amt ... +10%
Pump1pulse ... +2
Pump1Trig ... +14
Pump1Stop ... 02"Hg
Pump2Start ...2000
Pump2Amt ... +30%
Pump2Time ... +10
Pump2Trig ... +16
Pump2Stop ... 02"Hg
Pump1ADV ... +5
Pump2ADV ... +5
Pump Dwell ... 4.00
Pump Timers ... NO
Pump1 Sync ... NO
Pump Spare ... +08%
PumpCold…00%

Water
Screen 20

124 C ... +00%
99 C ... +00%
82 C ... +00%
68 C ... +08%
60 C ... +12%
46 C ... +15%
38 C ... +20%
31 C ... +30%
24 C ... +35%
18 C ... +45%
11 C ... +50%
5 C ... +50%
-1 C ... +55%
-9 C ... +60%
-17 C ... +70%
-25 C ... +00%

Air_t
Screen 21

124 C ... +00%
99 C ... +00%
82 C ... +00%
68 C ... +00%
60 C ... +00%
46 C ... +00%
38 C ... +00%
31 C ... +00%
24 C ... +02%
18 C ... +04%
11 C ... +05%
5 C ... +06%
-1 C ... +06%
-9 C ... +06%
-17 C ... +08%
-25 C ... +00%

Crank
Screen 22

124 C ... +00%
99 C ... +00%
82 C ... +00%
68 C ... +05%
60 C ... +15%
46 C ... +20%
38 C ... +26%
31 C ... +31%
24 C ... +41%
18 C ... +50%
11 C ... +57%
5 C ... +62%
-1 C ... +67%
-9 C ... +72%
-17 C ... +72%
-25 C ... 72%

t* rpm
Screen 23

500 ... +10
1000 ... +20
1500 ... +25
2000 ... +25
2500 ... +25
3000 ... +25
3500 ... +25
4000 ... +25
4500 ... +25
5000 ... +25
5500 ... +25
6000 ... +25
6500 ... +25
7000 ... +25
8000 ... +25
9000 ... +25

t*map
Screen 24

20 psi ... -10
18 psi ... -09
16 psi ... -08
14 psi ... -07
10 psi ... -06
8 psi ... -05
6 psi ... -03
4 psi ... -02
2 psi ... +00
00"Hg ... +00
05"Hg ... +00
10"Hg ... +02
15"Hg ... +03
20"Hg ... +04
25"Hg ... +04
30"Hg ... +00

t*air
Screen 25

124 C ... +00%
99 C ... +00%
82 C ... +00%
68 C ... +00%
60 C ... +00%
46 C ... +00%
38 C ... +00%
31 C ... +00%
24 C ... +00%
18 C ... +00%
11 C ... +00%
5 C ... +00%
-1 C ... +00%
-9 C ... +00%
-17 C ... +00%
-25 C ... +00%

t*gap
Screen 26

0500 ... +15
1000 ... +15
1500 ... +15
2000 ... +14
2500 ... +12
3000 ... +10
3500 ... +10
4000 ... +10
4500 ... +10
5000 ... +10
5500 ... +10
6000 ... +10
6500 ... +10
7000 ... +10
8000 ... +10
9000 ... +10

t*Inj
Screen 27

0500 ... 120
1000 ... 150
1500 ... 180
2000 ... 180
2500 ... 180
3000 ... 180
3500 ... 210
4000 ... 210
4500 ... 210
5000 ... 210
5500 ... 210
6000 ... 240
6500 ... 240
7000 ... 270
8000 ... 270
9000 ... 270

t* wat Screen 28

124 C ... +00
99 C ... +00
82 C ... +00
68 C ... +00
60 C ... +00
46 C ... +00
38 C ... +00
31 C ... +00
24 C ... +00
18 C ... +00
11 C ... +00
5 C ... +00
-1 C ... +00
-9 C ... +00
-17 C ... +00
-25 C ... +00

Thank you very very much!
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Old 06-29-14, 12:15 PM
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Im confused by all this as well. Just bought a Mtech haven't installed it yet and will be running the same injector sizes.

I thought you'd want 50% stg. When the secondaries come on-line, the map will be reduced by 50% to maintain the same amount of fuel as the secondaries are double the size of the primaries?

It would then seem logical that once you have the staging setup, you'd want to somehow subtract a blanket percentage of fuel across the entire map by 35% as your overall primary injector size is 35% larger. With an 85% stage, wouldn't your fuel remain the same on the low end, just as rich, except when the secondaries kick-on you'd now see an overall 85% reduction off the primaries. Holy crap, lol I'm so confused as well.
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Old 06-30-14, 07:56 PM
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BC

Monsterbox, thank you for your reply, it has got me thinking. I re read the manual and decided to follow it, insetead of this post
https://www.rx7club.com/microtech-11...-works-182032/
The manual tells me that the %stg is the time that the secondary injectors are open, based on a percentage of the main load map. If my %stg is at 65% then when my secondary injectors are activated, their open time is 65% of what the primary injector open time is.
To further clarify, if I am over the set REVstg and MAPstg, all 4 injectors will be firing. The primary injectors will be firing for the time set in the Load Map and the secondary injectors will be firing for a percentage of that time, set in the %stg .

This makes sense to me, but here is where it gets weird.
I can calculate the old flow rate when all 4 injectors are on at a given load, say 00”Hg.
(The primary flow is 550cc and secondary flow is 850cc and the %stg was set to 65%)
In the original load map the time for 00”Hg is set at 4.38ms
So we would have the primarys at 4.38 x 550cc for a total flow of 2409
The secondaries would be open for 65% of the time of 4.38ms (4.38 x 0.65 = 2.847ms) at 850cc for a total flow of 2419.95.
Add the flow of both the primary and secondary injectors together and you get a total of 4828.95. This is roughly 200% more fuel than if just the primary injectors were firing.

For the new injectors ( 850cc and 1680cc) we can figure out the new %stg by taking the same flow rates and working backwards.
2409total primary flow / 850cc is 2.83ms
If total flow is 4829, as figured out with the stock tune. Then the total flow of the secondarys is equal to 4829-2409 = 2420
If they are open for apercentage of the given 2.83ms above we can figure the %stg this way…
2.83 x %stg x 1680 = 2420
Simple algebra tells us that the percent stage should then be 51%

The reason this is weird, is because what I have read so far has told me that bigger gaps in injectors is equal to a bigger %stg, yet the math tells me differently.
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Old 06-30-14, 08:38 PM
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% stage value is added to the map look up table when the engine is in a pre staged condition

as such the numbers in look up tables represent the real time values when all four injectors are in operation

and the % stage is a bandaid applied to the look up table value when there is only two injectors running



if you previously had 550 and 850 pairs.. your volume at 100% duty was 2800 cc

your now combo of 850 and 1700 is 5100 cc .. increase in size factor is 1.8 . almost double

so your main look up tables should ( for sake of ease) ...approximately halve

if before.. we had 2.3 ms ( in the real time value ) at idle with 550 cc injectors
[ on most mild engines the primary 550 injector pairs will be idling between 2.1 and 2.5 ms ]

this amounts to 2.3ms x 550 cc required to idle
the same ( in realtime numbers ) volume on an 850 cc injector happens in 1.49 ms

if before with 550 if the realtime value was 2.3 ms and the staging value was 50 %..then (2.3/3) x 2 = 1.5 ms
( you have 1.57 for 20 inch vac .. and 2.14 for 15 inch vac.. the ecu will be co-relating this to about 1.6 at 19 inch vac.. so you can see my quick math is close )

if now the real look up table is slashed by 50 % ( the difference in our total injector math volumes )
then your values at 20 inch vac will be 0.8 ms and for 15 inch Hg it will be 1.07 ms

at idle of about 18-19 inch vac it will co-relate these values and i expect is using around 0.9 + the staging %

to get 0.9 back close to a 1.49 ms we need staging set to 70% ( = 1.53 ms )

( the slightly larger end result will account for the slight changes in injector latency,, expecting more latency with the larger injector )



rough math.. but basically you need to half all your look up table ( or more accurately .. divide by 1.8 ) ,, and set stage to 70%.. and fiddle very minimally with the idle setting to maintain idle

Last edited by bumpstart; 06-30-14 at 08:41 PM.
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Old 06-30-14, 10:22 PM
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PS save your current map to your memcal for a reference point and program in normal mode

before building it out in matrix mode
the normal mode map ( becomes the 4000 rpm map in matrix mode ) must be as close as possible

Last edited by bumpstart; 06-30-14 at 10:25 PM.
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Old 07-01-14, 12:19 AM
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if you are following

you will see that the main algorithm for the new main map is purely X = V2/V1

.. where V1 is the volume of the original injector setup, and V2 the volume of the latter setup


when the injectors are all in operation ( for most ,, above -5 inch Hg and above 3000 rpm )

then the total volumes are the same .. give take small discrepancies for the injector latency changes

basically , use pen and paper and jot down all the old ( normal mode ) load and idle values ( against vac/ boost points )
then use the calculator to apply the X factor to the old look up table to form a new one
( always save original un-modded map to memcal )

presto .. most of the work is done


///////////////

the change to the staging % is a little more tricky
.. here it is in a simplified form that takes advantage of the math already used above to form the prestage map , irrespective of the staging % of old



essentially you need to know the idle vacuum and realtime ms of old

( not the value in the look up table.. but the value displayed on the screen in realtime , which is look up table + staging % )

in the examples above.. i used 2.3 ms .. a pretty standard figure for most engines on 550 injectors idling around 18- 19 inch Hg

in your engine.. those values may be different

..especially if heavily ported

use the value you have at idle
a change of 2.3 to 2.6 does have large effect on our staging calculation..
at any rate.. the %stage and prestage values can be corrected by a prudent method when you start to tune it . more on that later

you need to then multiply your original idle ms value
.. by the factor that is the original primary injector divided the latter primary injector
ie.. 550/850 = 0.647

0.647 x 2.6 ms = 1.68 ms

while in the original calculation above with 2.3 ms -

0.647 x 2.3 ms = 1.49 ms



this is the period the new primary injectors need to be open to maintain the idle it used to ..

with the main look up tables now modified, you need to make a co-relation of your idle number
given that most ( 2 bar ) maps have waypoints for 15 and 20 inches Hg
and your idle was originally somewhere between 15 - 19 inches vacuum
( each engine depending )

if you have 15 or 19 inch Hg as your normal idle point , then just modify the bins directly involved .

if you idle somewhere in the middle.. average the numbers in either bin to arrive at close approximation of the new lookup tables value at your idle point

note ..
it is prudent on setup to put any idle values beyond idle vacuum
( under braking vacuum ) to the same minimum idle value to prevent idle hunts
and on heavily ported engines it may be prudent to put both bins either side of the idle point to the same value


in the rough example above.. we arrived at a 0.9 in the new look up table around idle point

but applied to your map then originally you had
20" ~ 1.48
and
15" ~ 1.81

if you idle at 18 inch Hg , and a factor of 1.8 is applied to the original then the new look up table will read
20" = 0.82
and
15" = 1.00

in that example then 0.9 ms is the value the ECU is adding the stage % to

so..

to get 0.9 in the look up table to 1.68 ms realtime we need to use a staging factor of 87% ( 1.68 ms )

to get 0.9 [ look up table ] ( in the example ) to 1.49 ms ish.. realtime then we use 70 % stage ( 1.53 ms )


a wide variance.. but here is the kicker
they only effect the values in pre-stage .. not when the engine is loaded up in boost .. they will not hurt the engine during setup to dial in the staging

however.. if you use the guide above ,, and find you had to use say 5% to the mixtrim to keep the idle ( when warmed up )

then you simply re-zero the mixtrim .. and add that % value to the % stage value
using the mixtrim initially will have fixed the idle.. but also fattened the post stage map considerably
putting it back into the % stage corrects this , and also effectively accounts for injector latency changes



having done all this .. the prestage values will be the same fuel as before
,, and the post stage values will amount to the same fuel as before

and all the duty times made by the injectors will have dropped by X factor , so much more in reserve for power ups
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Old 07-05-14, 03:47 AM
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Originally Posted by bumpstart View Post
if you are following

you will see that the main algorithm for the new main map is purely X = V2/V1

.. where V1 is the volume of the original injector setup, and V2 the volume of the latter setup


when the injectors are all in operation ( for most ,, above -5 inch Hg and above 3000 rpm )

then the total volumes are the same .. give take small discrepancies for the injector latency changes

basically , use pen and paper and jot down all the old ( normal mode ) load and idle values ( against vac/ boost points )
then use the calculator to apply the X factor to the old look up table to form a new one
( always save original un-modded map to memcal )

presto .. most of the work is done


///////////////

the change to the staging % is a little more tricky
.. here it is in a simplified form that takes advantage of the math already used above to form the prestage map , irrespective of the staging % of old



essentially you need to know the idle vacuum and realtime ms of old

( not the value in the look up table.. but the value displayed on the screen in realtime , which is look up table + staging % )

in the examples above.. i used 2.3 ms .. a pretty standard figure for most engines on 550 injectors idling around 18- 19 inch Hg

in your engine.. those values may be different

..especially if heavily ported

use the value you have at idle
a change of 2.3 to 2.6 does have large effect on our staging calculation..
at any rate.. the %stage and prestage values can be corrected by a prudent method when you start to tune it . more on that later

you need to then multiply your original idle ms value
.. by the factor that is the original primary injector divided the latter primary injector
ie.. 550/850 = 0.647

0.647 x 2.6 ms = 1.68 ms

while in the original calculation above with 2.3 ms -

0.647 x 2.3 ms = 1.49 ms



this is the period the new primary injectors need to be open to maintain the idle it used to ..

with the main look up tables now modified, you need to make a co-relation of your idle number
given that most ( 2 bar ) maps have waypoints for 15 and 20 inches Hg
and your idle was originally somewhere between 15 - 19 inches vacuum
( each engine depending )

if you have 15 or 19 inch Hg as your normal idle point , then just modify the bins directly involved .

if you idle somewhere in the middle.. average the numbers in either bin to arrive at close approximation of the new lookup tables value at your idle point

note ..
it is prudent on setup to put any idle values beyond idle vacuum
( under braking vacuum ) to the same minimum idle value to prevent idle hunts
and on heavily ported engines it may be prudent to put both bins either side of the idle point to the same value


in the rough example above.. we arrived at a 0.9 in the new look up table around idle point

but applied to your map then originally you had
20" ~ 1.48
and
15" ~ 1.81

if you idle at 18 inch Hg , and a factor of 1.8 is applied to the original then the new look up table will read
20" = 0.82
and
15" = 1.00

in that example then 0.9 ms is the value the ECU is adding the stage % to

so..

to get 0.9 in the look up table to 1.68 ms realtime we need to use a staging factor of 87% ( 1.68 ms )

to get 0.9 [ look up table ] ( in the example ) to 1.49 ms ish.. realtime then we use 70 % stage ( 1.53 ms )


a wide variance.. but here is the kicker
they only effect the values in pre-stage .. not when the engine is loaded up in boost .. they will not hurt the engine during setup to dial in the staging

however.. if you use the guide above ,, and find you had to use say 5% to the mixtrim to keep the idle ( when warmed up )

then you simply re-zero the mixtrim .. and add that % value to the % stage value
using the mixtrim initially will have fixed the idle.. but also fattened the post stage map considerably
putting it back into the % stage corrects this , and also effectively accounts for injector latency changes



having done all this .. the prestage values will be the same fuel as before
,, and the post stage values will amount to the same fuel as before

and all the duty times made by the injectors will have dropped by X factor , so much more in reserve for power ups
Please tell me if I'm understanding this correctly:

The new combination of 850/1680cc is double the total volume of fuel delivery at 100% duty than the factory 550/850 combination. To account for this difference in the mapping, we must slash all the values in the lookup table ~-50%.

Next, we must address the % staging. Although the overall fuel output has simply doubled from the original setup, the ratio of fuel between primary old : primary new has changed. In previous setup, primary injector is 65% of the secondary injector size. In the new setup, primary : injector ratio is now roughly 1:2 (50%). Therefore, if you would like the actual fuel output to remain relatively the same with the new table, we must adjust the %stage to roughly 65% to account for this change in ratio while utilizing a table that is been slashed 50%. After having performed these commands, the car should behave as though injector size hasn't changed (to an extent).

Thanks for this great post!!!!!!!!
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Old 07-05-14, 10:02 AM
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staging will be somewhere between 70 and 87% once the 1.8 factor has been applied to the duty times in the look up table

if you can whack on the mix trim just to get the engine warm
( to get the coolant warm up maps out of play )

then rezero the mix trim and instead bring the stage % up slowly till you find the point the car warm idles as it did before...

.. you will have found the magic staging number that corrects out all the prestage values in your new map

it is that simple
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Old 09-26-14, 09:27 AM
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Hey bumpstart, lets say that the user went from 550/1680 to 850/1680. The only variable changing is the primary injector size. Total change in volume is a factor of 1.13.

Divide every value in the look-up table by 1.13 (13% reduction) for each cell, to account for the increase in injector size.

Then, proceed to adjusting the staging percentage. However, since the end combination of 850/1650 is the same you mention last post, the staging should be the same correct? Somewhere between 70-87%



Conclusively, whether you started with 550/850 and moved to a 850/1680 combination, or you started with 550/1680 and upgraded the primaries later on, the staging percentage remains around 70-87% for an 850/1680 combo?
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