38 or 42 lb injectors
05-07-2004, 11:00 PM
#4
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38 lb injectors will be fine .......svo 30 lb injectos are good for 550 rwhp.....i know a lot of 450-475 rwhp cars with stock 28.5 injectors.....bosh 30 lb injectors are good for 692/554 fwhp at 100%/80% @0.4 bar...bosh 36 are good for 832/666 fwhp at 100%/80% @0.4 bar .........
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05-15-2004, 07:23 PM
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I have never seen it reported but I would think that a car under boost would need a larger injector for the same HP, It is not part of the calculation but still having a pressurized manifold would need the offsets changed and since the tables arent built for over 1 Bar I would suggest that the 38# injector that make 500RWHP may not do it in a supercharged manifold.
05-17-2004, 10:30 AM
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It is part of the math calculation.
A boosted engine has a BSFC of like .7 where a NA engine is .5
If you did the math :
500 FWHP*.7 BSFC/8 injectors/.8 duty cycle = 54.69 lb injectors needed and that was 500 HP at flywheel.
This assures injectors never fall behind and cause LTFTs to maintain high lean values, injectors are cooler with the shorter pulse widths and also the PCMs hardware logic for injectors are not overdriven.
General ballpark rule for every 1 HP needs 1lb/hr of fuel
I'd always go with the larger injector over the smaller ones.
A boosted engine has a BSFC of like .7 where a NA engine is .5
If you did the math :
500 FWHP*.7 BSFC/8 injectors/.8 duty cycle = 54.69 lb injectors needed and that was 500 HP at flywheel.
This assures injectors never fall behind and cause LTFTs to maintain high lean values, injectors are cooler with the shorter pulse widths and also the PCMs hardware logic for injectors are not overdriven.
General ballpark rule for every 1 HP needs 1lb/hr of fuel
I'd always go with the larger injector over the smaller ones.
05-17-2004, 11:05 AM
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Hmm, good info. The reason I chose the 38lb, they were off my friends Camaro that had a Vortech. He dynoed 544 rwhp with those Injectors.
05-18-2004, 08:17 AM
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Originally Posted by Team ZR-1
It is part of the math calculation.
A boosted engine has a BSFC of like .7 where a NA engine is .5
If you did the math :
500 FWHP*.7 BSFC/8 injectors/.8 duty cycle = 54.69 lb injectors needed and that was 500 HP at flywheel.
This assures injectors never fall behind and cause LTFTs to maintain high lean values, injectors are cooler with the shorter pulse widths and also the PCMs hardware logic for injectors are not overdriven.
General ballpark rule for every 1 HP needs 1lb/hr of fuel
I'd always go with the larger injector over the smaller ones.
A boosted engine has a BSFC of like .7 where a NA engine is .5
If you did the math :
500 FWHP*.7 BSFC/8 injectors/.8 duty cycle = 54.69 lb injectors needed and that was 500 HP at flywheel.
This assures injectors never fall behind and cause LTFTs to maintain high lean values, injectors are cooler with the shorter pulse widths and also the PCMs hardware logic for injectors are not overdriven.
General ballpark rule for every 1 HP needs 1lb/hr of fuel
I'd always go with the larger injector over the smaller ones.
This is the link that I refer to
http://www.rceng.com/technical.htm , there is an injector selection routine here. It is not clear if the BSFC is based on more fuel required for the AFR or is it a factor for the manifold influence or both?
The injector that is adequate at 5 PSI boost would have a different duty cycle at 15PSI for the same HP. Consider that the injector is at 58PSI and the manifold pressure varies 10PSI which in this calculation is a loss of 10% of the HP and at 15PSI is a 14% loss.
Im my situation when the MAF is at 428 gm/sec the 42LB injectors are at 85% duty, I am guessing 450RWHP 6000 rpm on an A4 /LS1/ 11.7 AFR.
05-18-2004, 10:27 AM
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Review the Aeromotive website, at
http://216.242.145.16/products/content_p.phtml?pk=11
Their math for flywheel HP and fuel needs are the same as I posted
Notice with the BSFC for boosted the injector size about doubles for the
same amount of HP of a NA engine.
http://216.242.145.16/products/content_p.phtml?pk=11
Their math for flywheel HP and fuel needs are the same as I posted
Notice with the BSFC for boosted the injector size about doubles for the
same amount of HP of a NA engine.
05-18-2004, 10:47 AM
#14
you also need to take into consideration for fuel pressure,. and if its rising rate regulator or not
My setup, 42's will problay be fine for that, but at X pounds of boost, i will have 58+X PSI at the rails, so it keeps a constant 58psi differential between tip and rails.
if you use the stock fuel system, say 12# of boost, your 42# injectors are only about 42#, instead of almost 50# (approx) with the ls1's 4 bar fuel system. As boost rises, injectors get smaller... NOT GOOD
Ryan
My setup, 42's will problay be fine for that, but at X pounds of boost, i will have 58+X PSI at the rails, so it keeps a constant 58psi differential between tip and rails.
if you use the stock fuel system, say 12# of boost, your 42# injectors are only about 42#, instead of almost 50# (approx) with the ls1's 4 bar fuel system. As boost rises, injectors get smaller... NOT GOOD
Ryan
05-18-2004, 11:22 AM
#16
stock fuel system, 58psi static.
if your fuel pressure does not rise, the injector basically gets smaller, as instead of 58 psi at the rails, and 0 at the tip, you can be at 58 at the rails, and 8 at the tip, with a differential of 50# vs 58#'s you can see how this will effect flow.
if your fuel pressure does not rise, the injector basically gets smaller, as instead of 58 psi at the rails, and 0 at the tip, you can be at 58 at the rails, and 8 at the tip, with a differential of 50# vs 58#'s you can see how this will effect flow.
05-19-2004, 03:42 PM
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you want to never exceed 85% duty cycle, calculate that in. Once you do you lose control of the injectors due to "static" operation.
Besides i think 42# are cheaper than any other size right? $299 new MSRP from steeda.com and less for other brands. oddball sizes are usually more expensive.
If you dare you can hit up a ford shop, alot of the new SVT fords have to ditch the 42# so they have some used ones for the low low. Cash talks.
Besides i think 42# are cheaper than any other size right? $299 new MSRP from steeda.com and less for other brands. oddball sizes are usually more expensive.
If you dare you can hit up a ford shop, alot of the new SVT fords have to ditch the 42# so they have some used ones for the low low. Cash talks.
05-20-2004, 09:02 AM
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I am being told that the spray pattern and fuel offsets are not right if you use the SVO (I have 30# now) I am being told to go with the GTP 38# for my 427. Any comments?
05-22-2004, 12:17 AM
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Well either the injectors were not enough or I need a fuel pump.
But went real lean on the dyno today with the 38's. FP dropped from 60 to 40 psi.
But went real lean on the dyno today with the 38's. FP dropped from 60 to 40 psi.