Injector Choice - 72 #ers ?

[Lynn D. Brown]

Guys - Anyone got any experience w 72 # injectors ? Not sure who makes them. One guy, I think on the GN list, is selling some at a good price. I will be needing a set, and I think I can save at least $100. I
was thinking about the 50 #'ers that the Forum sells, but not sure that they will be big enuf.

The word I get from Conley is that the 72's aren't made any more, and that they may have some tuning problems. It appears that not all injectors are born equal - some injectors R better than others. I had problems w 40 # Red Stripes (anyone want them cheap ?), good luck w Blue Tops and the Siemans 55 #ers on my GN seem OK.

I had heard that the 009's have had some problems and that the 50's were nice and linear. Any words on the injectors bigger than the 50's ?

 

[vortecfiero]

hicarumba ! that must be some build up !

 

[smeagol]

I've used 75# on several buildups, by Delphi, and they are good injectors. Just get them matched. Tony used the same on his truck I believe. I had them on my old Sy, Peter had them on his truck, I have several good calibration files for you start with too, if you do FAST.

Are you doing FAST/DFI or modded stock ECM, or other ?

 

[vortecfiero]

Brian: (sorry, Lynn, not to poach)

I've always used 9lbs of injector per 100 hp at 80% duty cycle, for a V6, to put me in the ballpark

so 32lbs divided by 9, times 100 would be ok for about 350 total hp (for a V6).

Of course Datamaster readings would be needed to fine tune, and slightly bigger is usually better...

am i off base ?

 

[smeagol]

Well figuring with a bsfc of .5 (this makes ballpark figures in your head easy), a 50lb/hr injectors is good for 600hp, 75lb/hr injector would be good for 900hp. Those are the absolute limits, since typical turbo motors have a lower bsfc, and since I'm assuming he's using FAST, I go with the injector with much higher headroom that doesn't sacrifice drivability. This way, with the closed loop wb02 correction, if you lost fuel pressure, a larger injector, coupled with the correction via the ECM, may be able to save your motor. The 75s can be tuned really well, wouldn't know them from stock using the right calibration. Well I shouldn't say that, I ain't too fond of the stock cal most of the time :wink:

Your simple calc gives you some ballpark numbers as well. It seems there are only a few choices of injector that I'd go with nowadays, because of quality, availability (both of the injector and of calibrations for them), and I've based my choices off of those factors. This is speaking for the V6 syty's, btw. In the 11s, I'd go with 50s. Looking for low 11s, to mid 10s, go with Delphi 75s. Want more? Then you need to evaluate 83s or 96s. At that point, I'd just do 96s. I've worked with 96s and 160s even. Going to 160s is a B I G step, and they are a bear, but you can work with them... gotta play games and really cut corners though :-?

FWIW, I've noticed there are people going really fast on stock injectors, and I attribute that to the fact that many of these people went that fast on stockers using HIGH fuel pressure, or running the ragged edge of lean (aka VERY DANGEROUS) but had high octane fuel in good conditions, keeping their motor intact.

 

[Lynn D. Brown]

Injector Choice

Injector Choice

Brian, et al.,

So It looks like 50 #'ers may be tight for my buildup, but doable. Then
I could avoid the modded ECM and primarily the expensive FAST right away. There R enuf new things to shake out in a totally modded engine, and I'm trying to not complicate everything right away.

It looks like we have a chip - the Ultimate - to handle this combo, and I can upgrade, as need be, from there.

 

[10secTy]

Brian hit the nail on the head. The 72's might work but they are a unknown untill I have to tune a set. The 75's on Tonys truck where at 90% duty cycle at 38 psi base fuel pressure. If you turned up the fuel pressure to 45 you would have more head room. Tony has run 128.5 mph in a 3500 lbs truck plus him in it. So if you do the math thats about 625 hp at the wheels. I am not sure what the driveline losses are but I would guess 20%.
So 625 x 1.2=750hp at the crank. Now the other thing to consider is that the engine needs more fuel at the torque peak. And the way tonys build is set up to to make HUGE torque. So I would guess his torque over the 800lbs mark. You have to take into consideration the times and mph you want to run in the 1/4 mile. If Tony upgraded his turbo he might be able to turn the fuel pressure up to supply the fuel he needs. So over shoot what you need and go aittle larger for safety sake. If you look at the PTE website the 50's are listed at $66.50 and the 75's at $62.50. No savings there. So now it comes down to if your build will work with the Ultimate Brian will have to make that call.

On some of the other injectors you listed I have a set of 009's in my wifes truck right now. The truck is stock except for exhaust and 3 bar. It drives and runs like a stock truck there is no problems with the 009's at all.

Nolan

 

[vortecfiero]

as hp increases does drive line loss also increase ?
maybe it is 20% of base hp say 280 to 300 hp so 60 hp loss?
if ya had 1000hp its still 60 hp?

 

[Lynn D. Brown]

Drive line losses

Drive line losses

I would think that driveline losses would go up primarily due to RPM.

 

[10secTy]

It is primarily a guess until some one dynos the truck on a AWD dyno and then pulls the motor out and dynos on a engine dyno.
I know that I am in the ball park as the duty cycle of the 75's is in the 90% range at 38psi base on Tonys truck. They are supposed to support 900hp at 45psi base. So pretty close.

His truck did make over 550hp at the rear wheel but due to 22% wheel slip we did not get a accurate number.

Nolan

 

[vortecfiero]

oops sorry I didn't doubt Tony's Hp, It was drive line losses in general

I keep hearing this Magical 20% figure and was wondering

by the same reasoning a 140hp engine with 28hp driveline loss (20% ) gets modified to 300 hp (turbo) and the 20% should be 60 hp on the exact same drive line.

A good friend of mine who went through a turbo build up went from around 110 hp at the wheels to 275 hp at the wheels ("before" and "after" dyno) and the "after" losses (same clutch, tranny, tires and rpm ranges )went up about 2% from about 25 hp to about 25.5 which could be just the dyno on 2 different test on two different days. The car runs low 13s

So when Tonys figured drive line losses grew to 150 hp I just couldnt figure it unless it is 150hp to begin with and that does'nt seem correct...

 

[10secTy]

With Speed the Driveline losses go up. How much loss is there at the line-none. how much at 10 mph-very little, How much at 128 mph A ton!!.
Its mostly friction. It could really could be 10% or 25%. All in all its really not that important.Whats important is that it runs 10's :wink:

Nolan

 

[vortecfiero]

aw jeez you'd think I'd know better sorry for belabouring the point

hp = work performed (or the ability to do work)

in this case the more work an engine can do, the more force it it imparts on the transmission. So more friction (the gears are imparting more force on the bearing surfaces), more resistance from the oil, tranny is going faster etc.....and we are talking acceleration not terminal velocity

and with the syclone i'll bet after 60 mph, aerodynamics really gets to be a major factor, which in turn, creates more stress/friction in the tranny

i seem to remember... at some point as the speed doubles, the aero drag squares (cd^2) and the HP to overcome must cube (hp^3)

sorta like in a road racer 600hp equals 200 mph (terminal velocity) and needs 50 more hp to go 201 mph (or better aero)

 

[vortecfiero]

nolan. I missed something in your post
YES there is nothing like a good 10 ! j/k