E85 Injector Max lb/min Calculations

Dark_Horse · 12-28-2006, 12:45 PM

I'm posting this because I keep seeing so many questions about running E85. "Will _____ size injectors allow me to run ______ turbo on E85?" Here is a guide that will answer all of your questions.

This guide takes the following into account.

1. All injectors flow exactly what they say they will. IE: 720cc injectors flow exactly 720cc.
2. All injectors flow exactly the same. IE: All injectors are perfectly matched (which is impossible in the real world)
3. Specific gravity of E85 is 0.79.
4. All calculations use a gasoline AFR of 12:1 - this equates to 8.05:1 in E85 #'s. Meaning - your wideband will read 12:1, but your actual AFR will be 8.05:1. Your wideband doesn't care what type of fuel you use, and will display numbers based on gasoline stohic (14.7:1).

With that in mind, on to the numbers.

390cc @ 100% IDC will support 21.80 lbs/min. Global Correction: +50.00%
390cc @ 80% IDC will support 17.44 lbs/min

450cc @ 100% IDC will support 25.15 lbs/min. Global Correction: +30.00%
450cc @ 80% IDC will support 20.12 lbs/min

550cc @ 100% IDC will support 30.74 lbs/min. Global Correction: +6.36%
550cc @ 80% IDC will support 24.59 lbs/min

580cc @ 100% IDC will support 32.42 lbs/min. Global Correction: +0.86%
580cc @ 80% IDC will support 25.94 lbs/min

650cc @ 100% IDC will support 36.33 lbs/min. Global Correction: -10.00%
650cc @ 80% IDC will support 29.07 lbs/min

660cc @ 100% IDC will support 36.89 lbs/min. Global Correction: -11.36%
660cc @ 80% IDC will support 29.51 lbs/min

680cc @ 100% IDC will support 38.01 lbs/min. Global Correction: -13.97%
680cc @ 80% IDC will support 30.41 lbs/min

720cc @ 100% IDC will support 40.24 lbs/min. Global Correction: -18.75%
720cc @ 80% IDC will support 32.20 lbs/min

750cc @ 100% IDC will support 41.92 lbs/min. Global Correction: -22.00%
750cc @ 80% IDC will support 33.54 lbs/min

780cc @ 100% IDC will support 43.60 lbs/min. Global Correction: -25.00%
780cc @ 80% IDC will support 34.88 lbs/min

850cc @ 100% IDC will support 47.51 lbs/min. Global Correction: -31.18%
850cc @ 80% IDC will support 38.01 lbs/min

880cc @ 100% IDC will support 49.19 lbs/min. Global Correction: -33.52%
880cc @ 80% IDC will support 39.35 lbs/min

950cc @ 100% IDC will support 53.10 lbs/min. Global Correction: -38..42%
950cc @ 80% IDC will support 42.48 lbs/min

1000cc @ 100% IDC will support 55.89 lbs/min. Global Correction: -41.50%
1000cc @ 80% IDC will support 44.72 lbs/min

1150cc @ 100% IDC will support 64.28 lbs/min. Global Correction: -49.13%
1150cc @ 80% IDC will support 51.42 lbs/min

1200cc @ 100% IDC will support 67.07 lbs/min. Global Correction: -51.25%
1200cc @ 80% IDC will support 53.66 lbs/min

1600cc @ 100% IDC will support 89.43 lbs/min. Global Correction: -63.44%
1600cc @ 80% IDC will support 71.55 lbs/min

1850cc @ 100% IDC will support 103.41 lbs/min. Global Correction: -68.38%
1850cc @ 80% IDC will support 82.72 lbs/min

DSM90AWD · 12-29-2006, 12:17 PM

Great Info!
It's seems that on E85 the injector airflow support is reduced by 19% (based on the E10 info you posted HERE.

I assume the same equation could be applied to fuel pumps as well (hint..hint :) ) ? :dsm:

Elvenhome21 · 12-29-2006, 01:43 PM

Can you create a table for straight Methanol

or at least 800-1600cc

Dark_Horse · 12-29-2006, 05:47 PM

Quote:

Originally Posted by Elvenhome21

Can you create a table for straight Methanol

or at least 800-1600cc

It will have to wait till Tuesday as my spreadsheet that does all of the calculations is on the computer at work.

Dark_Horse · 12-29-2006, 05:48 PM

Quote:

Originally Posted by DSM90AWD

I assume the same equation could be applied to fuel pumps as well (hint..hint :) ) ? :dsm:

I thought about doing that, but I only have flow information for the Walbro 190, 255LP, 255HP & Supra pumps. I won't list information for the Walbro 190lph and Walbro 255LP because they are too small to safely run E85.

Dark_Horse · 12-29-2006, 06:16 PM

Ok, since DSM90AWD asked so nicely, here is the fuel pump information related to E85. As I said above, I only have the numbers for the Walbro series and Supra pumps. If anyone else has the numbers for different pumps, I can add those too. I just need flow rates at 15PSI & 30PSI (boost pressure, not total fuel pressure)...I can extrapolate (sp) the rest.

Notes:

1. All numbers assume you have your fuel pump rewired.
2. These numbers may not be correct. 15psi and 30psi numbers are based on the flow rates RRE supplied for the 2 pumps I will list, and I calculated the numbers in between. Though, I've seen different flow rates from different sites. I just figured RRE probably knew what they were doing when it came to DSMs.
3. Once again, all calculations based on 100% E85, with a 12.0:1 (gasoline) AFR, which correlates to 8.05:1 in E85 numbers.
4. I'm only listing the 255HP and Supra pump numbers because the other 2 Walbros are too small to run E85 with.

NOTE - The below numbers are the absolute max you can run these fuel pumps. If you run 0.01lb/min more, you run the risk of blowing your engine up. Do not take these numbers as gospel either. My calculations could be wrong, the flow rates I based these calculations on could be wrong. Please give yourself a decent margin of safety. I take no responsibility for anyone blowing themselves or their car up.

Walbro 255HP Rewired

15psi - 56.78lb/min
16psi - 56.42 lb/min
17psi - 56.06 lb/min
18psi - 55.71 lb/min
19psi - 55.35 lb/min
20psi - 55.00 lb/min
21psi - 54.65 lb/min
22psi - 54.31 lb/min
23psi - 53.96 lb/min
24psi - 56.62 lb/min
25psi - 53.28 lb/min
26psi - 52.94 lb/min
27psi - 52.61 lb/min
28psi - 52.27 lb/min
29psi - 51.94 lb/min
30psi - 51.61 lb/min
31psi - 51.29 lb/min
32psi - 50.96 lb/min
33psi - 50.64 lb/min
34psi - 50.32 lb/min
35psi - 50.00 lb/min
36psi - 49.68 lb/min
37psi - 49.37 lb/min
38psi - 49.05 lb/min
39psi - 48.74 lb/min
40psi - 48.43 lb/min

Supra Pump Rewired

15psi - 63.12 lb/min
16psi - 62.62 lb/min
17psi - 62.13 lb/min
18psi - 61.64 lb/min
19psi - 61.15 lb/min
20psi - 60.67 lb/min
21psi - 60.19 lb/min
22psi - 59.71 lb/min
23psi - 59.24 lb/min
24psi - 58.77 lb/min
25psi - 58.31 lb/min
26psi - 57.85 lb/min
27psi - 57.39 lb/min
28psi - 56.94 lb/min
29psi - 56.49 lb/min
30psi - 56.04 lb/min
31psi - 55.60 lb/min
32psi - 55.16 lb/min
33psi - 54.72 lb/min
34psi - 54.29 lb/min
35psi - 53.86 lb/min
36psi - 53.44 lb/min
37psi - 53.02 lb/min
38psi - 52.60 lb/min
39psi - 52.18 lb/min
40psi - 51.77 lb/min

Elvenhome21 · 12-29-2006, 06:28 PM

If e85 is 8:1 ratio and methanol is 5.5:1
would it be correct to say that if my system flowed 45 lbs/min of air that I would need 1687 cc injectors. 5.5/8= .6875 x 100%= 1.6875 x 1000cc = 1687cc. Or is it 8/5.5 = 1.45 x 1000cc = 1450cc

also what pressure is the scale based on.

Dark_Horse · 12-29-2006, 07:03 PM

Quote:

Originally Posted by Elvenhome21

If e85 is 8:1 ratio and methanol is 5.5:1
would it be correct to say that if my system flowed 45 lbs/min of air that I would need 1687 cc injectors. 5.5/8= .6875 x 100%= 1.6875 x 1000cc = 1687cc. Or is it 8/5.5 = 1.45 x 1000cc = 1450cc

also what pressure is the scale based on.

If you are running 5.5:1 AFR on methanol, you will need minimim of 1200cc injectors. That's 100% IDC BTW. To maintain 80% IDC, then yes, you'll need 1450cc. All are based on SG of methanol being 0.7913

Oh, and the scale is based on absolute manifold pressure (IE boost), not total fuel pressure. If you wanted the total fuel pressure, then you'll need to add 43 to the psi numbers above. If you have a 1G, then obviously, you will have greater flow from the same pump due to having a lower base fuel pressure.