Help: Extra Info

---

Examples of various engine types

Weather in all of the following engine setups: air density: 100%; density altitude 0 feet; STP; temp. >> 60 deg. F, 0% humidity, 29.92 in. Hg. uncorrected barometer

engine	size	cyl	VE	GPM	nozzles	MBP	HS	AFR low speed	AFR high speed	psi w HS
NA VW	73 ci	4	90%	1.7	17	60	20	4.78	5.09	79
NA Ford	250 ci	6	90%	1.86	27	46	20	4.81	5.10	89
NA flat head	255 ci	8	75%	1.8	18	45	20	5.07	5.51	157 (61 @ 5000)
NA wedge	350 ci	8	100%	4	30	87	34	4.81	5.18	7
NA wedge	550 ci	8	100%	6.47	37	109	50	4.74	5.26	79
NA wedge up & down nozzles	410 ci	8	100%	4	up: 25 down: 24	86	34	4.86	5.19	59
6-71 Roots blower at 20% overdrive, wedge V-8 engine with hat nozzles only	492 ci*	8	90%	12.8	53	155	55	3.81	4.08	81
	*410 blower ci x 1.20 = 492 ci (984 is equivalent entry in NA calculator)
14-71 Roots blower at 33% overdrive, hemi V-8 engine with hat & port nozzles	1384 ci**	8	100%	15.5	hat: 54 port: 47	100	65	2.97	3.22	96
	** 520 blower ci x 1.33 = 692 ci (1384 is equivalent entry in NA calculator)
D rotor PSI screw blower at 92% overdrive, hemi V-8 with hat & port nozzles	1636 ci***	8	95%	15.1	hat: 2 x 80 below 30 psi (4 x 80 above 30 psi) port:8 x 50 (fixed) dribbler: 8 x 45 (fixed)	66	none	3.00	2.95	63
	*** 426 blower ci x 1.92 = 818 ci (1636 is equivalent entry in NA calculator)

return to top

---

Chart of fuel pump sizes

The following chart lists approximate fuel pump flows at 4,000 pump rpm and 8,000 engine rpm.

Note: Some fuel pumps may be equipped with an internal pressure relief valve/port that may limit the fuel pump flow to values lower than these when the fuel pressure goes higher than the pressure relief setting.

* Gallons per minute (GPM) values are approximate for new pumps. For used pumps with absence of internal scoring and good pump seals, GPM flow values can be typically 5% lower than these values.

Manufacturer/model	GPM new*	GPM used*
Enderle 80A-00 gear rotor	1.80	1.71
Enderle 80A-0 gear rotor	4.00	3.8
Enderle 80A-1/2 gear rotor	5.20	4.94
Enderle 80A-1 gear rotor	7.00	6.65
Enderle 80A-1 DSR	7.50	7.13
Enderle 600 gear rotor	9.00	8.55
Enderle 760	11.40	10.83
Enderle 110 gear rotor	13.00	12.85
Enderle 990	15.7	14.92
Enderle 1100	17.2	16.34
Enderle 1200	18.8	17.86
Enderle 1270	20.2	19.19
Hilborn -00 gear rotor	1.70	1.62
Hilborn -0 gear rotor	3.52	3.34
Hilborn -super 0 gear rotor	3.96	3.76
Hilborn -1/2 gear rotor	5.12	4.86
Hilborn -1 gear rotor	6.47	6.17
Hilborn -1 1/2 gear rotor	8.48	8.01
Hilborn -2 gear rotor	12.50	11.86
Hilborn -4	15.6	14.72
Hilborn -5	19.4	18.43
Kinsler TP-200 twin gear	1.86	1.77
Kinsler TP-300 twin gear	2.89	2.75
Kinsler TP-400 twin gear	3.83	3.64
Kinsler KW-400 twin gear	3.90	3.71
Kinsler 450 twin gear	4.33	4.11
Kinsler TP-450 twin gear	4.33	4.11
Kinsler KW-450 twin gear	4.35	4.13
Kinsler 500 twin gear	4.76	4.52
Kinsler TP-500 twin gear	4.76	4.52
Kinsler KW-500 twin gear	4.90	4.66
Kinsler KW-600 twin gear	5.80	5.51
Kinsler 700 twin gear	6.56	6.23
Kinsler TP-700 twin gear	6.56	6.23
Kinsler KW-700 twin gear	6.80	6.46
Kinsler KW-900 twin gear	8.60	8.17
Kinsler KW-1200 twin gear	11.50	10.86
Kinsler KW-1300 twin gear	12.50	11.86
Rons -0 vane	3.38	3.21
Rons -0 gear rotor	3.44	3.27
Rons -0 twin gear	4.00	3.8
Rons -0 1/2 vane	4.74	4.5
Rons -0 1/2 gear rotor	4.86	4.62
Rons -0 1/2 twin gear	4.86	4.62
Rons -1 gear rotor	6.00	5.7
Rons -1 twin gear	6.26	5.95
Rons -1 1/2 twin gear	9.20	8.74
Rons -2	12.9	12.26
Waterman 250300 twin gear	2.80	2.66
Waterman 200030 Sprint Ultra Lite	3	2.85
Waterman 250400 twin gear	3.80	3.61
Waterman 250500 twin gear	4.80	4.56
Waterman 250450 twin gear	4.30	4.09
Waterman 250600 twin gear	5.80	5.51
Waterman 200060 Micro-Bertha	6	5.7
Waterman 250800 Mini-Bertha	8	7.6
Waterman 250700 twin gear	6.80	6.46
Waterman 200070 Sprint Ultra Lite	7	6.65
Waterman 251300 Mini-Bertha	13.00	12.85
Waterman 320850N Nostalgia single section	14-22	13.3-20.9
Waterman 320800 Lil-Bertha	14	13.3
Waterman XXXXXX Lil-Bertha	20.8	19.76
Waterman 320850N Nostalgia single section	22	20.9
Waterman 321112 Big Bertha 2 section gear	34	32.3
Waterman 321600 Lil-Bertha	35	33.25
Waterman 321616 Big Bertha 2 section gear	68	64.6
Waterman 323200 Mega Bertha 4-section gear	115	109.25

return to top

---

Chart of standard blower sizes

blower	nominal rotor length	blower size (standard)	blower size (with tight seals)
6-71	15	410	430
8-71	16	440	470
10-71	17	470	490
12-71	18	490	520
14-71	19	520	550
screw blower	standard PSI “D” rotor	425
screw blower	standard PSI “C” rotor	476
Whipple R-980		598

return to top

---

Chart of standard nozzle sizes

 

Math to generate values in the previous list:
 The data result from the following math from Ref. jettingsmallblock, p. 26 or jettingbigblock, p. 35:

nozzle area = (nozzle flow) x SQRT (VA factor / 30 psi)

nozzle flow = Hilborn nozzle flow number x 0.01

nozzle dia. = SQRT (nozzle area / 0.7854)

Example for a Hilborn #12 nozzle:


nozzle area = (nozzle flow) x SQRT ( 0.00079 / 30)

nozzle flow = 12 x 0.01 = 0.12

nozzle area = (0.12) x SQRT ( 0.00075 / 30) = 0.0006153

nozzle dia. = SQRT ( 0.0006153 / 0.7854) = 0.028 inches

VA factor – Fuel pressure calibration: 
The VA factor is a volume area factor throughout our books & calculator. It is a calibration value developed as a simple relationship between jetting flow and jetting size. Using Hilborn nozzle flow numbers and nozzle diameters, the VA factor was calculated for each nozzle. Those are shown with each respective nozzle size. The math for that is derived from above as follows:

VA factor – Fuel pressure calibration (continued)

VA factor = 30 psi x (nozzle area / nozzle flow)²

nozzle area = (nozzle diameter)² x 0.7854

Example for Hllborn #24:


nozzle area = (0.037)² x 0.7854 = 0.0010752

nozzle flow = Hilborn nozzle flow number x 0.01 = 24 x 0.01 = 0.24

VA factor = 30 x (0.0010752 / 0.24)² = 0.00060

Fuel pressure calibration for flared inlet jetting: 
The VA factor values throughout the list indicate the approximate fuel pressure calibration values used in the math and in our calculator for a Hilborn system with flared nozzles and bypass jets. The actual fuel pressure calibration VA factor for the Pro-Calcs calculator or a racer’s own computations can be determined from a fuel pressure gauge reading at a specific engine speed. That is further illustrated in fuelinjectionracingsecrets, p. 169. The values above can help to dial in jetting combinations when no previous pressure gauge reading is available for specific jetting combinations that are of interest.

Value of fuel pressure calibration: 
Fine tuning for maximum performance in a mechanical fuel injection system requires the fine adjustment of nozzles and bypass jets. Trial & error is a very difficult alternative. The right computations significantly reduce that trial & error time and expense. Fuel pressure calibration is a significant issue in computations. The previous examples illustrate how fuel pressure, flow, and jet size relate. In this case, the examples were from Hilborn flared nozzles. Flared nozzles from other manufacturers would exhibit similar VA factor calibrations for our Pro-Calcs calculator. They would also exhibit similar VA factor calibrations for a racer’s own computations using the math throughout our technical manuals.

Actual computations for pressure from nozzle size are quite complex. The VA factor method that we developed greatly simplifies the task.

The more time I spend with normally aspirated fuel injection technology such as this, the more I realize how much improvement can be done with jetting refinements guided by preliminary math analysis.

Footnote to normally aspirated fuel injection engines: 
A lot of normally aspirated FI engines are run without a high speed bypass. That is often the case with Rons FI systems for example. If the tuner in these applications is leaning down the jetting to get color into the spark plugs, it is likely that the engine is too lean at the torque peak. That is the engine speed where the fuel demand per-engine-revolution is the max. When no high speed bypass is run, the engine is richer at engine speeds above the torque peak. The high speed bypass provides the ability to trim the fuel curve for that fuel characteristic. Care should be exercised with FI when tuning is done on a normally aspirated engine with no high speed. If we leaned down jetting so that spark plugs were colored after engine loading, then we would closely monitor engine compression. We would also check the condition of pistons and valves with a tear down. We would confirm that the air to fuel ratio at the torque peak is not so lean that it was damaging parts. More information about the high speed bypass is throughout our books.

return to top

---

Please contact us with any errors you find while using this part of the site.