jets for 3sgte with 650 cc injectors

[zakshaker]

Hello,

which jets & restrictor would you recomend for a celica GT4 3sgte with 650cc injectors which will be boosting 1.5 bar on a Garrett GT28rs. (that should be around 90% injdutycyle)
we plan to have a jet before IC and an other one after.
we want jets to inject 18/20%

[zakshaker]

So let's see if I have welldone my math
650*4=2600cc
90% = 2340cc max duty
20% jets = 468
PUMP 160 psi minus 22 psi BOOST = jet flow 138 PSI

So that would mean, if one jet would be used only I would need a 0.9mm which I would trim gain just a bit down.

and if I want to use 2 jets, then I need a 0.4 before IC and a 0.5 after. which I would also need to trim gain down a bit. or I could use two 0.4 jets that I would trim gain up.

In both case I would need to use a 0.7mm restrictor

am I right ?

[zakshaker]

While I'm at it.
what about those 2 setups .
same 1350cc engine. both boosting 1.5 bar on TD04H turbo. one use 440cc injector almost to max IDC, the other one use 550cc on much lower IDC. I would guess they both should use same jets.

440*4= 1760cc
90% = 1584 max duty
20% = 317cc jet flow


PUMP 160 psi minus 22 psi BOOST = pump flow 138 PSI

both setup would need 0.6mm jet and 0.5mm restrictor installed (550cc setup will need to have jets gain trimed up)

am I right ?

[Howerton Engineering]

We typically leave the DC of the injectors out of the calculation unless some odd application is apparent as since we are pulsing at an IDC it's a relative item.

For example, if you have 650cc injectors(4 cyl) at 90% and want to spray 25%, you would use 650 of Aquamist injector. If your car is at 90%IDC, then the Aquamist, barring any gain/trim adjustment will be at 90%IDC as well.

So your two engines with 440 and 550 injectors, would use different size jetting to deliver the same amount based on IDC readings.

Other than that, once you get you jet amount, I would add 10-20% for pumping losses. The jetting chart is ideal conditions, depending on how you set your system up(tubing lengths tee's, etc.) each applications losses are a bit different.

Here is a page laying out a few samples:

http://www.howertonengineering.com/Jet_Calc.html

[zakshaker]

thanks a lot for your help and link.

yeah, I know the HFS-3 follow IDC. my thought was low jet idc might not be very accurate.
so when using only 60% of Fuel IDC, it might have been better to use smaller jets and play on gain to optimize jet range. if you see what I mean
my way of thinking might not have been the best thought :(

the reason why the 1350cc turbo has larger 550cc injectors is cause it was running 90% ethanol for some race (straight in the tank)
but now it is running on regular RON92 fuel. so it doesn't use more than 60% injection duty
about restrictor in that case, what should I do ?

550cc injectors means I would have 2200cc total injector
20% = 440cc jet flow.

so that would mean I would need 0.8 jets and 0.7 restrictor

0.7 restrictor is meant to use up to 680cc, but as I would never use more than 60% injection duty cycle, it would means the pump would never actualy need to flow more than 265cc/min. so should I use 0.5 restrictor instead ? (as they are meant to be use up to 380cc/min)

[Howerton Engineering]

If the IDC is artificially low, as in the case of 60%IDC being max then two things can be done. 1) is two take IDC into the calculation and run an artificially large jet to get the CC's you want, or 2) use the gain function of the controller to set the Aquamist to hit just about 95%DC at your rev-limiter/redline with the jetting to get the job done.

The restrictor is used to match the inlet orifice of the valve to the jetting. So regardless of any IDC, match the total jet size CC to the restrictor size CC.

Low IDC jetting can be accurate depending on how you setup the system. Many folks can make a mess of a perfectly good system, with proper installation, and looking at the setup, as you are, they can be made to function very well.

The .8 jet and .7mm restrictor are about right for the injectors. If you want to use a smaller jet and restrictor and use the gain to get 100% from the jet you can do that as well.
You are using the dynamic range of the system a bit better in the latter scenario.

[zakshaker]

thnaks for you help,
so my thoughts were not that bad :)

Back to the celica 3SGTE engine.
we have installed and checked flow today with "SYS" connector bridged

the celica has a GT28rs with 650cc injectors
will be boosting around 1.5 bar

so 650*4 = 2600 cc
20% = 520 cc/min

we have tested our installation, with two jets : 0.6 + 0.7
we get 545 ml/min
now do I need to apply a ratio to that figure to know what will be the real flow at 1.5 bar ? shoud I use smaller jet, or are we spot on ?

thanks

[Howerton Engineering]

You are spot on. You only loose a few percent at those boost levels, it's splitting hairs at that point. I would leave it as is unless you need to do something else during tuning.

[zakshaker]

hmm, I'm confused.
we need to loose at least 5% to get under 520cc/min at 1.5 bar (which is 20%)
otherwize it would mean we would inject more than 20%
I understood 20% is the max percentage to use with 50:50 watermeth. Am I wrong ?

[Richard L]

Zak,

The 20% value is only a guideline. There is no limit what you can inject as long as the igbnition system can cope with it.