FMU question
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
FMU question
Ok, so as most of you know, this SC stuff is new to me, so here goes another dumb question.
The kit I have has a 10-1 fmu with it. However, I will be running 30lb injectors. So if I understand correctly I need to get a calibration kit to change it to 6-1 for the 30lb injectors. Am I correct?
The kit I have has a 10-1 fmu with it. However, I will be running 30lb injectors. So if I understand correctly I need to get a calibration kit to change it to 6-1 for the 30lb injectors. Am I correct?
Melting Slicks
Joined: Dec 2000
Posts: 2,719
Likes: 59
From: Fremont Oh
93 Ragtop,
How much power are you looking to make, and what or how much boost... that is the major determining factor...
The 10:1 is geared for the 24-26 pound injectors..
So with your boost you are or plan on making is a determining factor of what the 30 pound injectors need to "look like" with the increased fuel pressure... Are you using or planning on using a additional supplimwntl fuel pump?
mo
How much power are you looking to make, and what or how much boost... that is the major determining factor...
The 10:1 is geared for the 24-26 pound injectors..
So with your boost you are or plan on making is a determining factor of what the 30 pound injectors need to "look like" with the increased fuel pressure... Are you using or planning on using a additional supplimwntl fuel pump?
mo
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
I hope to get 6lbs boost. For now, im going to run it on the setup below in signature, and im going to add water/alky injection. I have a inline fuel pump to be added. (it came with the kit) Im open for changes or suggestions.
Melting Slicks
Joined: Dec 2000
Posts: 2,719
Likes: 59
From: Fremont Oh
Ok so it looks like yo are making roughly 360 hp..
So with 6 pounds of boost you take 14.7 +6 =20.7 / 14.7 = ~1.4
So you take 360 *1.4 = ~504 hp
With your 30 pound injectors you are going to need to be about 80- 85 pounds of fuel pressure... With the water alky, it will cut that back "some"... But you will need to be around the effective 44 pound mark, that is runnning the injectors at 85% some push them a little farther but eventually it messes them up...
Rule of thumb figuring 6 pounds of boost every thing is about a factor of 1.4
hope this helps you some...
MO
So with 6 pounds of boost you take 14.7 +6 =20.7 / 14.7 = ~1.4
So you take 360 *1.4 = ~504 hp
With your 30 pound injectors you are going to need to be about 80- 85 pounds of fuel pressure... With the water alky, it will cut that back "some"... But you will need to be around the effective 44 pound mark, that is runnning the injectors at 85% some push them a little farther but eventually it messes them up...
Rule of thumb figuring 6 pounds of boost every thing is about a factor of 1.4
hope this helps you some...
MO
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
So if my stock pressure is 43, then with 6lbs boost I would need 8 to 1 instead of the 10 to 1 I have now? Do you suggest I start looking for a set of 36 or 42 lb injectors since the injector cycle will be getting high?
Racer
Joined: Jul 2002
Posts: 313
Likes: 1
From: Dallas Tx
Originally Posted by 93 ragtop
So if my stock pressure is 43, then with 6lbs boost I would need 8 to 1 instead of the 10 to 1 I have now? Do you suggest I start looking for a set of 36 or 42 lb injectors since the injector cycle will be getting high?
Here is a good calculation:
Injector Flow Rate (lb/hr) =
Engine HP x BSFC / Number of Injectors x Max Duty Cycle
Use a BSFC of .6-.65 for FI. Therefore at 500 HP, injector flow rate is 50.78#.
Melting Slicks
Joined: Dec 2000
Posts: 2,719
Likes: 59
From: Fremont Oh
Originally Posted by 93 ragtop
So if my stock pressure is 43, then with 6lbs boost I would need 8 to 1 instead of the 10 to 1 I have now? Do you suggest I start looking for a set of 36 or 42 lb injectors since the injector cycle will be getting high?
For the few hundred dollars I would ... I used to cringe having fuel pressure that high...
The calculations that Scott also gave you give you the calculaled fuel needed for the required horsepower. The BSFC can be slightly lower with water alcohol.
Mo
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Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
I was just looking at the fmu with this kit, and on top, there is the short nipple that will go to a vacuum source, but there is a tee, which has a bolt screwed into the side of it with a lock nut. Is that the adjustment that is mentioned above?
Oh, and let me say for those that dont know. I purchased this kit used.
And thanks again for everyones help.
Oh, and let me say for those that dont know. I purchased this kit used.
And thanks again for everyones help.
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
Originally Posted by qwiketz
that sounds like what I have on mine. it's a little screw on the opposite side of the line that comes in to sense boost and vacuum.
Yes, I was looking at pictures in the installation book and it seems that a pipe nipple, tee, and that bolt assy has been added. Thanks for your help!!