Injector sizes

[diy guy]

you guys are missing the point. true, more fuel is consumed at high rpm but that is because there are more cycles. The pulse width per cycle is less at high rpm. think VE.

this is your typical 3d map (fuel @ load vs rpm):

and back to my high tq/low hp comparison, lets take it a step further. this is a little extreme but think about caterpillar construction diesels. low revs and tons of torque. lets say they make 1000tq peak at 1000rpm redline, thats only 190hp. would injectors for a 190hp sports car supply enough fuel?

 

[siman]

Not neccesarily,

Its always better to have that "extra" tuning window if need be.

550's and 660's are the same price if I remember correctly...so I personally would go with the 660's anyways.

You never know when that 400whp might get "boaring" and you want to go bigger and badder! :biglaugh:

-Jonathan

 

[siman]

diy guy,



Your basing all your information off of TORQUE.

Of course if you have an undersqaure motor that revs to 3K rpm you would not need HP in the scenario.

In our motors being square ( or damn near close to it ), you really concentrate on HP numbers.....the HIGH rpm power that you speak of.

In that being said, this is the reason we based the judgement of cc=hp measurement.

Your a little off in saying that since the injectors have smaller pulse widths at higher rpm that there is less fuel injected.

It does not matter about pulse width, for that breif milisecond, say at 100% duty cycle with a 550cc injector, there WILL BE 550CC fuel injected per minute calculated.

Par with this,

You need bigger injectors when you are adding a larger turbine ( more air ). Its an all inclusive package DIY GUY.

If we were going for TQ, we would have a small turbine and limit the rpm rev range and have smaller injectors.

But we are out there for max HP. We need large injectors to deal with the large amounts of air. And again, the bigger the injection maximum, the more area we can move the fuel maps.....

In that being said, our whole power curve can be rearranged soley on having BIGGER injectors.

1. you can up the boost by keeping the WG closed longer
2. You could add cams for higher powerband HP.
3. you can succeed in that with a fuel tuning device ( SAFC ).

Its an all inclusive package...you really cannot do one without the other.



-Jonathan

 

[figgie]

you guys are missing the point. true, more fuel is consumed at high rpm but that is because there are more cycles. The pulse width per cycle is less at high rpm. think VE.

not only are you mistake but you are dead wrong. As the VE of the engine increases thanks to RPMs the injectors have ZERO CHOICE but to increase the amount of fuel injected to keep up with the higher OVERALL VOLUME of air. Guess what this produces...... if you didn't guess HP you are way off base.

this is your typical 3d map (fuel @ load vs rpm):

Correct

notice as RPMS increase regardless of MAP fuel injectors Pulse MUST increase to keep up with the higher volume of air flow which correlates to MORE HP Has nothing to do with Torque peak.

 

[siman]

not only are you mistake but you are dead wrong. As the VE of the engine increases thanks to RPMs the injectors have ZERO CHOICE but to increase the amount of fuel injected to keep up with the higher OVERALL VOLUME of air. Guess what this produces...... if you didn't guess HP you are way off base.



Correct

notice as RPMS increase regardless of MAP fuel injectors Pulse MUST increase to keep up with the higher volume of air flow which correlates to MORE HP Has nothing to do with Torque peak.

So I was right?:icon_conf

 

[figgie]

So I was right?:icon_conf

umm yes!

is that like amazing or something??

 

[siman]

It should not be.:rofl:

I know a little bit here and there but not everything.

 

[arz]

I saw several errors, ommisions, mistakes, whatever you want to call em.

1st
Sinman

Old School rule of thumb:

100CC per 100hp.

So our stock 440cc injectors can hold UP TO 440hp at the CRANK ( not whp)

550cc=550hp
750cc=750hp and so on.

-Jonathan

this only applys to 6 cylinder motors with 6 injectors.

I would be very surprised to see someone getting 400WHP out of 4, 440 injectors in a 4 cylinder with no other suplimental fuel (nos, meth, anything).

2nd
Diy guy

yes, it needs to open/close faster @ higher rpm, but but that's irrelevant. flow, as measured by the mfg, is tested at 100% duty at a predetermined pressure, not by how fast it can open/close. duty cycle is higher at peak torque than at redline, where torque declines, is it not?

Injectors always open and close at the exact same speed. It is the duration they are open that changes. Once any injector gets above 80% duty cycle it becomes inaccurate at measureing fuel because it is assumed that the injector takes some (albiet very small amount of) time to open and close. It is generaly accepted that above 80% duty cycle the injector will be open so long that it will get the command to close, and before it can totaly close it will get the command to open again. This is the reason for the inaccuracys above the 80% duty cycle. Injectors vary radically in design and recommended pressures so this 80% does vary from design to design and manufacturer also.

I made a few calls to local injector places and none could verify if a particular manufacturer measures an injector at WFO or teh 80% duty. I will next time I have some tested just to satisfy my curiosity. My local injector places do a baseline and just compare the percentages at 40 psi. They couldnt say what PSI an injector is measured at. Im sure it varys from manufacturer to manufacturer. I could be wrong but I dont think they measure them wide open because its not good for the injector coil.

duty cycle is higher at peak torque than at redline, where torque declines, is it not?

this statement supports what my WB shows when I am nearing the limit of my injectors/boost level. By that I mean my WB displays a decrase in fuel ratio in the middle of the powerband where my torque is the greatest.

 

[arz]

The whole reason I was surfing this thread was to find out if anybody has ACUALLY installed 650's or 660's with an SAFC II and all other supporting mods (IE: not with a CT26 turbo of any kind). Will the SAFC II be able to control the fuel properly when not in WOT mode. Will it run rich every where else?

 

[siman]

SR20's/B18C's all can get over 400 WHEEL horsepower on 400CC injectors.

Belive me, I have seen it in the flesh:icon_bigg

 

[diy guy]

ok i see where i'm wrong. it doesn't matter whether a motor is over/undersquare, x amount of fuel is required for the same amount of air in either. what i didnt realize is that, at lower rpm, the injector is open for a longer time. in other words the same injector even at the same pulsewith delivers more fuel as rpm rise. twice as much fuel at 1k rpm than at 2k, 3 times as much as at 3k and so on. so yeah, a 190hp@9k (i was thinking type r) sportscar's injectors probably would deliver enough fuel to power a 1k redline to 1000tq. thats 9 times as much fuel than at 9k. makes sense since 1000tq/9 is roughly the tq a hype r makes at that high rpm i hope that wasnt too confusing

now to redeem myself...

It does not matter about pulse width, for that breif milisecond, say at 100% duty cycle with a 550cc injector, there WILL BE 550CC fuel injected per minute calculated

that brief milisecond matters a lot, otherwise we wouldnt tune our motors at 6k rpm, 20ms is all the time you have to inject fuel (100% duty). 1ms=5% fuel

notice as RPMS increase regardless of MAP fuel injectors Pulse MUST increase to keep up with the higher volume of air flow which correlates to MORE HP Has nothing to do with Torque peak

take a second look. focus on the peak load line (top), you can see that it ramps up, settles, and heads back south towards redline.

It's no secret that a motor's Volumetric Efficiency is highest at peak torque and declines towards redline, it doesn't keep on rising as rpm rise.

I could be wrong but I dont think they measure them wide open because its not good for the injector coil.

rc tests them fully open

Will the SAFC II be able to control the fuel properly when not in WOT mode.

yes, you can use the low throttle map to adjust fuel in open loop operation

 

[arz]

Quote:
Will the SAFC II be able to control the fuel properly when not in WOT mode.

yes, you can use the low throttle map to adjust fuel in open loop operation

Cool
So you have experience with the SAFCII? Or an SAFCII with a motor that has injectors 50% bigger than that car came with? Or better yet 650~680's in a MK3 with an SAFCII? I have yet to hook mine up and Im just worried Im gonna run out of fuel.

Right now I have a T4 60-1 AT 21 PSI with a Lex/AFM on stock 440's and the WB looks a tad lean between 3400-4400 hoping to turn the boost up after I get the SAFCII and some injectors. Just cant make up my mind about 550's or something bigger.

 

[Dirgle]

P.S. The 7M motor IS undersquare.

7M-Undersquare-less revs more torque.
2JZ-Square-Balance between the two.
1JZ-Oversquare-More revs less torque.

 

[figgie]

...
take a second look. focus on the peak load line (top), you can see that it ramps up, settles, and heads back south towards redline.

psst

we are turbo VE changes for turbo/supercharged app.

yes, you can use the low throttle map to adjust fuel in open loop operation

Haven't worked to long with the 7m ecu have you?

adjusting the "low" map is an excercise in futility. Any adjustments you do will be undone by the tccm adjusting for the new values. Minus well chase your own tail.

 

[kssweeper28]

Old School rule of thumb:

100CC per 100hp.

So our stock 440cc injectors can hold UP TO 440hp at the CRANK ( not whp)

550cc=550hp
750cc=750hp and so on.

-Jonathan

Ill remember that one. THX Siman

 

[diy guy]

psst

we are turbo VE changes for turbo/supercharged app.

turbo or not, VE reaches a peak before redline.

Haven't worked to long with the 7m ecu have you?

adjusting the "low" map is an excercise in futility. Any adjustments you do will be undone by the tccm adjusting for the new values. Minus well chase your own tail.

from http://supraforums.com/forum/printthread.php?threadid=248033

What you'll probably want to do is tap the vf pin on the diagnostics block and adjust the AFC to get a 2.5v output on it. Drive it on the dyno at cruise and adjust the low throttle settings on the AFC to get to 2.5v.

I'd probably set the settings on the SAFC to start at 3000rpm and go up from there. At the low throttle setting you can adjust the 3000rpm point and it will adjust all the settings 3000rpm and below. I'd set the lo/hi throttle points at 74 and 75%, and the next RPM point at 3400rpm if it's an SAFC II (3500 if SAFC)

Once you have the AFC adjusted so that the TCCS is not adjusting from the basic fuel calculation, that point will be the new 0% fuel adjust.. so if you end up doing going -20% on the SAFC, -20% will be the 0 setting on the Hi Throttle setting. so if you need to add 10% under full throttle, you will need to set it at -10%.

Here is a link for some info regarding the TCCS Vf output.

http://www.supras.com/~riemer/lexus...lexusnotes.html

If it's reading 3.75 or 5v is means the ecu is adding fuel to the basic fuel calculation to get to it's stoich reading, if it's 1.25v or 0v it means the ECU is taking away fuel from the basic fuel calculaion to get it's stoich reading. More than likely right now it's probably reading 0v at cruise where it's trying to remove as much fuel as it can to run properly. It can only adjust up to 20% and the injectors are 25% which is probably causing the unstable a/f ratio The Basic Fuel Calculation is the base map that the ECU is programmed with. With everything stock and running correctly, it should be at 2.5v.

If you have any questions give me a call.