Injector ratings

[Bill@HPTuners]

Alot of people are confused by the terms and the rating system so I'll try to explain a bit. A few people have come to me saying "I've got some 30lb injectors I wanna install how do I figure out what my IFR table should be" The first question I always ask is "What psi are the injectors rated at?" and undoubtedly the answer is always "I don't know" lol. So first things first Understand there is a ratings system when it comes to injectors where they are rated in bars or psi...1 bar=~14.5psi so when a company says "We've got 40lb injectors rated at 3 bar" that also means they are flowing 40lb/[email protected].

Now here's where it gets tricky & most people don't know whats going on...LS1's generally have their fuel pressure at ~58psi not 43.5 MEANING those 40lbers@58psi are going to flow closer to 45lb injectors and can mean a HUGE difference in fueling characteristics. Most places that sell injectors will show you their ratings similar to this http://www.racetronix.com/17113739.html

You all know about the excel IFR calculator thats already in the sticky so I wont go over that, but it'll basically do MOST of the work for you.

Bottom line to this new sticky is to verify YOUR fuel pressure as well as the fuel pressure the injectors are rated at.

Im leaving this thread open for discussion or corrections of any inaccuracies in the info I've given.

[Dirty Howie]

"I've got some 30lb injectors I wanna install how do I figure out what my IFR table should be" The first question I always ask is "What psi are the injectors rated at?" and undoubtedly the answer is always "I don't know"

hahahahahahaah...how dumb can you be


DH

[WS6FirebirdTA00]

very true

[jimmyblue]

It's a pretty muddy situation because you have a
variety of rating pressures, and your own pressure
is variable (but not well modeled) - fuel fade, line
drops, dirty filter, blah blah. You will probably have
to fake one end of the other, idle or WOT, to get
the result right. A manifold referenced, rail mounted
regulator and some fat forward plumbing would be
the fix for a lot of that.

Someday.

[EC_Tune]

It would have been NICE if GM would have spent a couple extra $$ like FORD did and actually MEASURED the fuel pressure but, alas, they didn't. So it is up to us to make and take those measurements and integrate them into HP Tuners.

[Dirty Howie]

It would have been NICE if GM would have spent a couple extra $$ like FORD did and actually MEASURED the fuel pressure but, alas, they didn't. So it is up to us to make and take those measurements and integrate them into HP Tuners.

Doug

So when everybody (not necessarily here) states 58 lbs for Vette feul pressure that in actuallity we need to measure it ??


DH

[Bill@HPTuners]

Basically, yes. Fuel pressure does play an integral part in fueling obviously and when available yes you should see what is sitting at...the more you know the better off you'll end up being.

[Dirty Howie]

Basically, yes. Fuel pressure does play an integral part in fueling obviously and when available yes you should see what is sitting at...the more you know the better off you'll end up being.

For a shop with the right equipment this should be a really quick and simple task.....correct??

THANKS

DH

[Bill@HPTuners]

yeah...I think electronic fuel pressure gauges are only like $100 from autometer as well and can be logged right into hptuners as well so theres another option for ya

[WorkingManPerf.]

Off topic but relavent to fuel injectors.

Is the voltage offsets for fuel injectors. That confuses me the most.

Like 60lbs'er are around .055 sec's at 14 vac. which is just one line of data on the whole table. What about the rest of the values??

[BADSZ28]

So what are stock injectors rated at then? My green tops are rated at 42lbs at 43.5psi. So if I offset that to 58 they are really 56lbs @ 58psi. So assuming the stockers are rated at 28lbs @ 58psi I would get a 0.5 multiplier. So do I then take that and multiply it against my closed loop proportional base vs. airflow mode? That is quite a change. I just want to be sure I am doing this correctly.

[SRT10KLLR]

Injectors rated 42lbs at 43.5psi would be 48.5lbs at 58psi. When you did the math you forgot to take the square root of the quotient before you multiplied.

So, 58 divided by 43.5 = 1.3333333333. The square root of 1.333333333 is 1.1547000. You take that and multiply by 42 and you get 48.497.

[WS6FirebirdTA00]

Green tops are not rated at 43.5 either.

[SRT10KLLR]

Yes, the Ford Motorsports catalog shows the following "All injector flow rates are quoted at a delta pressure of 39.15 psi. To convert to a delta pressure of 43.5 psi, multiply flow rate by 1.054".

[redhardsupra]

you can believe some specs or you can believe empirical testing, your choice:

http://redhardsupra.blogspot.com/200...vo-42s-is.html

[BADSZ28]

They are made by Bosch and rated at 43.5psi. So looks like your test data proves this and that they are about 49lbs at 58psi. So then it would be 28.8/49 to get a multiplier of 0.588.