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View Full Version : What are the cons of bigger injectors?



sd_iconoclast
08-13-2004, 01:03 PM
I am currently rebuilding my SC engine and I have made the following mods:
Ross forged pistons
Eagle H-Beam rods
207* camshaft with stiffer springs
Harland Sharp 1.73 roller rockers
Ported (by me) heads and intake
Kooks headers
SCP exhaust
BBK 70mm throttle body

In the future I would like to upgrade to the Magnum Powers front mounted intercooler or the Autorotor blower.

I am considering upgrading my fuel injectors to 36# or 42#. Do I need it now?
Are there any disadvantages to larger fuel injectors?

wezar
08-13-2004, 02:21 PM
Minimum of 42# er's for that mill.


Don't foget the new 255 LPH fuel pump.


Bigger injectors may hurt your mileage a bit. Still its a lot cheaper than when the smaller ones reach the limit and you burn a hole in one of your nice new Ross pistons when the engine goes lean.

BT Motorsports
08-13-2004, 03:13 PM
As Rick said, at least 42's I would consider 50s if you plan on an autorotor. Make sure the fuel pump is a 255 forced induction model.

injectors: www.racetronix.com
fuel pumps: www.autoperformanceengineering.com

Stay away from a rail mount AFPR, so far we haven't found one that hasn't failed.

Paul

XxSlowpokexX
08-14-2004, 07:19 AM
You said cons>>...The possability of poorer idle quality and loading up at idle, More gas usage as well just driving around.....42's arnt bad and 50's are the limit..Depends what you are considering to be large

XR7 Dave
08-14-2004, 10:25 AM
Can't report on mileage yet but I've been running 60's for awhile on the XR7 with no issues that I know of... The first thing I was concerned about was loading up at idle so the first thing I did was let the car sit and idle for about 20 minutes. Ran perfect and never missed a beat. Startup is excellent.

On another note, I am running a C&L 80MM MAF with a black sample tube. With the necessary scaling adjustments made I found the mixture to be still off by about 15%. I also found that the meter is not pegging at 6000rpm so that was good news. It's nice not to have to worry about fuel delivery for once! LOL

XxSlowpokexX
08-14-2004, 11:10 AM
How come I have 65lbrs and everyone else has 60's..I just dont get it

T-bird4vr
08-15-2004, 02:57 AM
David or Damon, can one of you explain the idle load up to me?

RancherV6Lee
08-15-2004, 06:51 PM
I have absolutly NO issues with 42# injectors on my car, Its ALL in the tune. My gasmileage is just as good if not better now with my vortech supercharger on my 96' 3.8L compaired to stock.

sd_iconoclast
08-30-2004, 02:50 PM
Stay away from a rail mount AFPR, so far we haven't found one that hasn't failed.

Paul

Have you tried the BBK Adjustable Fuel Pressure regulator? I have had one on my (stock) SC for about a year without problems. I did have to do a lot of gringing to get it to fit though?

BT Motorsports
08-30-2004, 06:52 PM
Have you tried the BBK Adjustable Fuel Pressure regulator? I have had one on my (stock) SC for about a year without problems. I did have to do a lot of gringing to get it to fit though?
Been there done that. It happens to be the same exact unit Holley offers, just with a rebranding. Holley, BBK, Aeromotive rail mount regulators are all the same and all of the diaphragms have been known to rupture on an SC.

Paul

edspringer
08-30-2004, 07:11 PM
You said cons>>...The possability of poorer idle quality and loading up at idle, More gas usage as well just driving around.....42's arnt bad and 50's are the limit..Depends what you are considering to be large

Damon........I switched to 38# injectors about 6 months ago on my 94 SC and have had a rough idle (it almost shakes my radar detector of the windshield) problem every since. My mileage has got worse except for long trips it is pretty good. I have a C&L MAF and I got the BLUE 38# tube but it runs worse with the 38 tube then it does with the 36# tube. You can see my mods below and I read your posts since you have gone with your SC where most probably won't. Any suggestions on how to fix the rough idle problem. I'm seriously considering going back to the 36# injectors.

OBTW my 90 XR7 runs real strong, idles great and gets right around 18 MPG stop and go driving. As you can see the only difference is the injectors

Ed Springer

90 Black XR7 5-speed: 142,740 miles, 70mm TB, Fresh Air Intake, '94 Supercharger Upgrade, 36# injectors, 190 l/h fuel pump, 5% SC Pulley, Raised SC Top, I/C Fan, Under drive Pulleys, Headers, Magnaflow Muffler (no cats) with stock resonators, 3:27 Gears, Rear Spring Air Bags, Ripper Shifter, 73 C&L MAF, Magnacore Wires, NGK Iridium Plugs, Royal Purple Synthetic Lubricants.

94 Red SC Auto: 93,660 miles, 70mm TB, Fresh Air Intake, Stock 90 SC Pulley, 38# injectors, 190 l/h fuel pump, Raised SC Top, I/C Fan, Under drive Pulleys, Headers, Raven Muffler (no cats) with stock resonators, 3:73 Gears, 73 C&L MAF, Magnacore Wires, NGK Iridium Plugs, TRANSGO Shift Kit, Haydon Auxiliary Transmission Cooler, ProTorque 2500 TC, Tokico Struts & Shocks, Royal Purple Synthetic Lubricants, American Racing 17 Sniper Wheels, Michelin Pilot Sport A/S, dynode 235 RWHP at 315 LB-FT. Torque.

XxSlowpokexX
08-30-2004, 07:14 PM
I think there is a problem getting the right calibration for 38lb injectors. You probably should have gone with the 42's. Maybe a Pro M would help you out

Also keep in mind calibratiion for the 94-95 is different then earlier models

edspringer
08-30-2004, 07:28 PM
I think there is a problem getting the right calibration for 38lb injectors. You probably should have gone with the 42's. Maybe a Pro M would help you out

Also keep in mind calibratiion for the 94-95 is different then earlier models

I may try 42s and a Pro M. Does that fit the 94-95 calibration better then my current 38 and 73 MAF setup?

XR7 Dave
08-30-2004, 09:27 PM
Damon........I switched to 38# injectors about 6 months ago on my 94 SC and have had a rough idle (it almost shakes my radar detector of the windshield) problem every since. My mileage has got worse except for long trips it is pretty good. I have a C&L MAF and I got the BLUE 38# tube but it runs worse with the 38 tube then it does with the 36# tube.

94 Red SC Auto: 93,660 miles, 70mm TB, Fresh Air Intake, Stock 90 SC Pulley, 38# injectors, 190 l/h fuel pump, Raised SC Top, I/C Fan, Under drive Pulleys, Headers, Raven Muffler (no cats) with stock resonators, 3:73 Gears, 73 C&L MAF, Magnacore Wires, NGK Iridium Plugs, TRANSGO Shift Kit, Haydon Auxiliary Transmission Cooler, ProTorque 2500 TC, Tokico Struts & Shocks, Royal Purple Synthetic Lubricants, American Racing 17 Sniper Wheels, Michelin Pilot Sport A/S, dynode 235 RWHP at 315 LB-FT. Torque.

Accoding to this:
73 MM_ _ _ _ _ _ _ _ SC Model Years_ _ _ _ _ _ _ _ _ 76 MM
_ _ _ _
Color_ _ _ _ _ _89-93_ _ _ _ _ _ _ 94-95_ _ _ _ _ _ _ _ Color

silver*_ _ _ _ _ 30_ _ _ _ _ _ _ _ 36/38_ _ _ _ _ _ _ yellow
blue_ _ _ _ _ _ 36/38_ _ _ _ _ _ _ _ 42_ _ _ _ _ _ _ _ _orange
red_ _ _ _ _ _ _ _ 42_ _ _ _ _ _ _ _ 50_ _ _ _ _ _ _ _ _ purple
green_ _ _ _ _ _ 50_ _ _ _ _ _ _ _ xx_ _ _ _ _ _ _ _ _ green
from the members section, the correct sample tube for a 73mm MAF on a 94 is the silver or "clear" tube. I hope you also kept the electronics from the 94 WITH the 94 because they are very different from 89-94. At your HP level I would recomment going back to the stock injectors and MAF anyhow. Both OE units in this case are good to at least 260rwhp.

sd_iconoclast
08-31-2004, 03:26 AM
XR7 Dave,
I just ordered a C&L 76mm MAF for my '89 SC with 42 lb injectors. C&L told me that I needed the purple sample tube. I am having trouble reading your table. Does this recomendation sound right to you?

Randy N Connie
08-31-2004, 07:52 AM
sd_iconoclast
I use a purple sample tube in my 76mm C&L MAF,with #42 injectors.
1990 SC.

Randy

edspringer
08-31-2004, 08:06 AM
Accoding to this: from the members section, the correct sample tube for a 73mm MAF on a 94 is the silver or "clear" tube. I hope you also kept the electronics from the 94 WITH the 94 because they are very different from 89-94. At your HP level I would recomment going back to the stock injectors and MAF anyhow. Both OE units in this case are good to at least 260rwhp.

Dave......thanks for the info. I probably will put the 36# injectors back in when I change intake gaskets. The 94 stock electronics is installed in the 73mm MAF. That should make my 94 run as good as my 90 XR7.

Ed

edspringer
09-01-2004, 01:40 PM
sd_iconoclast.........go to the C&L website and it is explained clearer.

http://www.cnlperformance.com/index.shtml

Ed Springer

BlackbirdSC
09-03-2004, 02:02 PM
Been there done that. It happens to be the same exact unit Holley offers, just with a rebranding. Holley, BBK, Aeromotive rail mount regulators are all the same and all of the diaphragms have been known to rupture on an SC.

Paul

Try a Mallory. I've had one for about 3 years and it doesn't seem to be giving any troubles. It does bleed down quickly after being turned off, but holds steady while running and doesn't blow fuel through the vacuum line. I don't recall the number offhand, but I used a 95 SC fuel rail and PR for a 94-95 Muskrat.