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Choosing Injector Size

15292 Views 10 Replies 6 Participants Last post by  Motorhead, 
John90
How do you choose the right injector size for you setup, obviously you want to keep them a low a cc rating as possible for your application for idle reasons so how do you choose what you need or how do you calculate the psi or bhp you can get out of the ones you have?

I have Supra Green Top 320cc's and have a Jackson Racing high pressure fuel pump. (I also have a new Walbro in the garage, is this the same at the JR?)

Obviously its a 1990 mk1 running a JR M45. I want to know what psi/bhp is possible with these, are they up to the 12psi 150/60mm pulley combo, and if not how do I calculate the size required?

Thanks in advance

John
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Motorhead
Not sure how you'd go about working out the psi available from a supercharger/pulley combo. But on the injector front this could be useful:-

http://www.rceng.com/technical.aspx

As you've an uprated fuel pump you'll need to work out what your fuel pressure is and this will then affect the 'real' cc delivery of your injectors, which in turn will give a bhp figure.
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John90
Cheers, anyone know the original pressure for the mk1 at the fuel rail and also the difference with one of my different uprated fuel pumps?

Also is there a list of compatable plug and play inectors list for the mx5 anywhere?
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Motorhead
John90 said:
Cheers, anyone know the original pressure for the mk1 at the fuel rail and also the difference with one of my different uprated fuel pumps?

Also is there a list of compatable plug and play inectors list for the mx5 anywhere?
Click to expand...
How about this, I don't know if it's exhaustive (or even totally correct)....

Year Make/Model Engine Size/Color Part #
87-88 Toyota MR2 4AGE NA 213cc ? Beige Top #23250-16080
89-91 B2220 Truck 224cc - Yellow Top? #23250-74040?
99-00 Mazda Miata 240cc - Thin Red Body #195500-4430
Toyota 4AGE 250cc ? Green Top
Toyota 4AGE 250cc ? Violet Top
94-97 Mazda Miata 254cc - Tan Top #195500-2180
01-05 Mazda Miata NA & TURBO 265cc - Thin Lt. Prple #195500-4060
Toyota 3SGE 295cc ? Green Top
89-92 Toyota Supra 7MGE NA 305cc ? Light Green Top #23250-70080
93-95 Toyota Supra 3.0L 312cc - Maroon Top #23250-46030
Toyota 3SGE 315cc ? Pink Top
90-92 MX6/626/Probe Turbo 326cc - Gray Top #195500-2150
89-91 B2600 Truck 326cc - Gray Top #195500-2150
Mazda 323 GTX TURBO 360cc - Black Top #195500-2130
Celica/MR2 3SGE NA 370cc - Green Top #23250-74160
Mazda RX8 420cc - Yellow Body #195500-4450
Subaru WRX 425cc - Lt. Blue Body #3920
89-92 Toyota Supra 7MGE TURBO 430cc ? Black Top
89-92 Mazda RX-7 NA 440cc - Blue Top #195500-5740
89-91 RX-7 NA 460cc - Red Top #195500-2010
Subaru STi 540cc - Thin Pink Body #3910
89-91 RX-7 TURBO 550cc - purple top #195500-2020

low impedence

89-92 Toyota Supra (7MGE) NA - (295cc ? Yellow Top) - #23250-70040
88-91 Toyota Collora GT-S Turbo (4AGZE) ? (365cc ? Red-Orange Top)
92-95 Toyota Collora GT-S TURBO (4AGZE) ? (365cc ? Red-Orange Top)
86-92 Toyota Supra (7MGTE) TURBO ? (430cc ? Black Top)
Toyota MR2 (3SGTE) TURBO ? (430cc ? Black Top)

Dunno what the standard fuel pressure is on a mk1...sorry. How many litres per hour is your fuel pump rated to?
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UTU (Rich)
The PSI will depend on your particular setup - exhaust, engine, intercooler, etc - but here's a chart from TDR showing the blower RPM of particular combinations:

http://www.trackdogracing.com/website/sc_accessories/pulley_chart.htm

Though it probably won't help you! Probably looking at what people are running with a similar setup is a good gauge of which there are plenty!
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R
iirc Mk1's fuel pressure is 43psi, Mk2's have a higher fuel pressure of somewhere around 60psi. You might want to google those figures though as they're just from memory.

useful place to look for info is the miataturbo.net FAQ section.

the 320cc inectors should enable you to hit 200bhp, but as mentioned above a lot of that depends on other factors, it's ony a rough figure.
I'm at around 190Bhp on my 320's and see just over 80% duty cycle. Personaly I wouldn't go much above 85% duty cycle just for safety's sake.

I know very little about the JR or Walbro fuel pumps, and wheher they actualy raise your fuel pressure from stock, I guess an adjustable afpr could be used to raise the pressure a ittle and give some more headroom on the injectors but really if you want to aim for bigger power figures you need to upgrade the inectors.

get a fuel pressure guage fitted and see what fuel pressure you're runnng at the moment.
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UTU (Rich)
jimbob said:
iirc Mk1's fuel pressure is 43psi, Mk2's have a higher fuel pressure of somewhere around 60psi. You might want to google those figures though as they're just from memory.

useful place to look for info is the miataturbo.net FAQ section.

the 320cc inectors should enable you to hit 200bhp, but as mentioned above a lot of that depends on other factors, it's ony a rough figure.
I'm at around 190Bhp on my 320's and see just over 80% duty cycle. Personaly I wouldn't go much above 85% duty cycle just for safety's sake.

I know very little about the JR or Walbro fuel pumps, and wheher they actualy raise your fuel pressure from stock, I guess an adjustable afpr could be used to raise the pressure a ittle and give some more headroom on the injectors but really if you want to aim for bigger power figures you need to upgrade the inectors.

get a fuel pressure guage fitted and see what fuel pressure you're runnng at the moment.
Click to expand...
IIRC Mk2 injectors also have a better spray pattern.
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friendly1_uk
yep, stock is around 43.5psi but remember at 12psi that will be 12psi higher and every online calc ive seen ignores this as there for nasp but with boost enrichment corrections. They never ask the boost to be able to calculate it propperly.

The bigger pump wont raise pressure. Pressure is set by the fuel pressure regulator.

Off the top of my head, 12psi will produce around 230bhp and using 320s you would need near 80psi of fuel pressure. They are ofton seen to flow 370cc though which would require little or no extra fuel pressure. Your probably not going to get past 10psi with the stock fpr and 320s
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John90
skir67 said:
Cheers, anyone know the original pressure for the mk1 at the fuel rail and also the difference with one of my different uprated fuel pumps?

Also is there a list of compatable plug and play inectors list for the mx5 anywhere?
Click to expand...
How about this, I don't know if it's exhaustive (or even totally correct)....

Year Make/Model Engine Size/Color Part #
87-88 Toyota MR2 4AGE NA 213cc ? Beige Top #23250-16080
89-91 B2220 Truck 224cc - Yellow Top? #23250-74040?
99-00 Mazda Miata 240cc - Thin Red Body #195500-4430
Toyota 4AGE 250cc ? Green Top
Toyota 4AGE 250cc ? Violet Top
94-97 Mazda Miata 254cc - Tan Top #195500-2180
01-05 Mazda Miata NA & TURBO 265cc - Thin Lt. Prple #195500-4060
Toyota 3SGE 295cc ? Green Top
89-92 Toyota Supra 7MGE NA 305cc ? Light Green Top #23250-70080
93-95 Toyota Supra 3.0L 312cc - Maroon Top #23250-46030
Toyota 3SGE 315cc ? Pink Top
90-92 MX6/626/Probe Turbo 326cc - Gray Top #195500-2150
89-91 B2600 Truck 326cc - Gray Top #195500-2150
Mazda 323 GTX TURBO 360cc - Black Top #195500-2130
Celica/MR2 3SGE NA 370cc - Green Top #23250-74160
Mazda RX8 420cc - Yellow Body #195500-4450
Subaru WRX 425cc - Lt. Blue Body #3920
89-92 Toyota Supra 7MGE TURBO 430cc ? Black Top
89-92 Mazda RX-7 NA 440cc - Blue Top #195500-5740
89-91 RX-7 NA 460cc - Red Top #195500-2010
Subaru STi 540cc - Thin Pink Body #3910
89-91 RX-7 TURBO 550cc - purple top #195500-2020

low impedence

89-92 Toyota Supra (7MGE) NA - (295cc ? Yellow Top) - #23250-70040
88-91 Toyota Collora GT-S Turbo (4AGZE) ? (365cc ? Red-Orange Top)
92-95 Toyota Collora GT-S TURBO (4AGZE) ? (365cc ? Red-Orange Top)
86-92 Toyota Supra (7MGTE) TURBO ? (430cc ? Black Top)
Toyota MR2 (3SGTE) TURBO ? (430cc ? Black Top)

Dunno what the standard fuel pressure is on a mk1...sorry. How many litres per hour is your fuel pump rated to?
[/quote]

Cheers guys, is it high impedance that are p+p with no need for resistors?
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G
Just for reference, my peak boost is a nats hair under 10psig / 24.7psia. injectors are deatsch werks (inj-mia-350) these will flow circ 400cc @ MK2.5 fuel rail pressure (57psig typ) Power is 250hp with a DC of 88%
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Motorhead
John90 said:
Cheers, anyone know the original pressure for the mk1 at the fuel rail and also the difference with one of my different uprated fuel pumps?

Also is there a list of compatable plug and play inectors list for the mx5 anywhere?
Click to expand...
How about this, I don't know if it's exhaustive (or even totally correct)....

Year Make/Model Engine Size/Color Part #
87-88 Toyota MR2 4AGE NA 213cc ? Beige Top #23250-16080
89-91 B2220 Truck 224cc - Yellow Top? #23250-74040?
99-00 Mazda Miata 240cc - Thin Red Body #195500-4430
Toyota 4AGE 250cc ? Green Top
Toyota 4AGE 250cc ? Violet Top
94-97 Mazda Miata 254cc - Tan Top #195500-2180
01-05 Mazda Miata NA & TURBO 265cc - Thin Lt. Prple #195500-4060
Toyota 3SGE 295cc ? Green Top
89-92 Toyota Supra 7MGE NA 305cc ? Light Green Top #23250-70080
93-95 Toyota Supra 3.0L 312cc - Maroon Top #23250-46030
Toyota 3SGE 315cc ? Pink Top
90-92 MX6/626/Probe Turbo 326cc - Gray Top #195500-2150
89-91 B2600 Truck 326cc - Gray Top #195500-2150
Mazda 323 GTX TURBO 360cc - Black Top #195500-2130
Celica/MR2 3SGE NA 370cc - Green Top #23250-74160
Mazda RX8 420cc - Yellow Body #195500-4450
Subaru WRX 425cc - Lt. Blue Body #3920
89-92 Toyota Supra 7MGE TURBO 430cc ? Black Top
89-92 Mazda RX-7 NA 440cc - Blue Top #195500-5740
89-91 RX-7 NA 460cc - Red Top #195500-2010
Subaru STi 540cc - Thin Pink Body #3910
89-91 RX-7 TURBO 550cc - purple top #195500-2020

low impedence

89-92 Toyota Supra (7MGE) NA - (295cc ? Yellow Top) - #23250-70040
88-91 Toyota Collora GT-S Turbo (4AGZE) ? (365cc ? Red-Orange Top)
92-95 Toyota Collora GT-S TURBO (4AGZE) ? (365cc ? Red-Orange Top)
86-92 Toyota Supra (7MGTE) TURBO ? (430cc ? Black Top)
Toyota MR2 (3SGTE) TURBO ? (430cc ? Black Top)

Dunno what the standard fuel pressure is on a mk1...sorry. How many litres per hour is your fuel pump rated to?
[/quote]

Cheers guys, is it high impedance that are p+p with no need for resistors?
[/quote]

Yes that's right
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