MX-5 OC Forum

Morning,

I've got a 1.8 with JRSC plus the big boost kit fitted running the standard AFPR and JR powercard.

What size injectors could I run with this sort of set up? Currently they are just stock, however no2 cylinder is running a little hot and just want to ensure nothing goes pop....

Plus stupid question - I'm fairly new to the supercharger business and on the JR powercard I have knob to adjust - boost / retard +/-. Question is - when rotating the knob, am I increasing or decreasing the boost or the timing? I'm guessing the timing, but just checking!

thanks

Rob

that's a hard one but try this link it should help:

http://www.gtsparkplugs.com/InjectorSizeCalc.html

you may find that fitting an air/fuel ratio meter will help, but always run on the richer side.

Cheers.

Whats the flow rate for standard injectors? The calculator comes up with a flow rate of 354/min..

G'day mate. My car is a 1.6 with the JRSC and I run 4x Denso 330cc injectors with new O rings

 Sounds good - I'll probably have to find a more local supplier though

robpick:

Whats the flow rate for standard injectors?

Stock 1.8 Mk.1 injectors (tan coloured tops) are 230cc/min.

Any particular supplier recommended for uprated injectors? What 2nd hand ones fit?

robpick:

...What 2nd hand ones fit?

There's an often-quoted list on miataturbo.net:

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
01-06     Mazda Miata              240cc - Thin Lt. Prple #195500-4060
          Toyota        4AGE       250cc – Green Top   
          Toyota        4AGE       250cc – Violet Top   
94-97     Mazda Miata              265cc - Tan Top        #195500-2180

          Toyota        3SGE       295cc – Green Top   
89-92     Toyota Supra  7MGE NA    305cc – LT 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
89-92     Mazda RX-7    NA         440cc - Blue Top       #195500-5740
89-91     RX-7          NA         460cc - Red Top        #195500-2010
89-91     RX-7          TURBO      550cc - purple top     #195500-2020

(You'll see that the tan 1.8 MX-5 injectors are listed there as 265cc/min instead of 230.  I don't know why.)

All of the above are high impedance injectors with the same Denso connector as stock, so they're electrically and mechanically compatible with MX-5s, but you need to be aware that the stock ECU won't be able to control injectors much larger than the stock ones unaided.  For example I believe the 1.6 ECU can cope with swapping its stock blue-top 205cc injectors for 230cc tan tops from a 1.8, but any larger size needs some supplementary electronics (or a replacement ECU) to enable it to cope.

If you did go down the route of changing the ECU then you would also be able to consider using faster-opening low impedance injectors instead.  (There's a similar list of those types.  They use an almost identical Denso connector but with a tab that needs to be filed down to make them plug and play.)

Whn it comes to new injectors, there's a model (EV14, I think it's called) which quite a number of people have tried and seem to like.  There's some kind of issue around making sure you get the right spacers with it, as it's physically shorter than the Denso pattern.  Don't know the exact details though.

I think that you would be safe to up grade to the Supra 305cc green top.

I did toy with the idea of changing mine.

But i'm no expert.

Martin Young:

For example I believe the 1.6 ECU can cope with swapping its stock blue-top 205cc injectors for 230cc tan tops from a 1.8, but any larger size needs some supplementary electronics (or a replacement ECU) to enable it to cope.

That's my understanding also. I've got a whole bunch of other stuff on my SC setup, here's a lift from my notes, comments are from my mate who I bought the system from

May 16th 2008
Supercharger fitted by Danny Irvine
Jackson Racing M45 supercharger kit, plus full standalone plug and play ECU (MSPNP)Megasquirt. Other bits include:
•    Jackson Racing BBK "Big Boost Kit" crank overlay pulley (gives 10psi)
•    Innovate LC-1 wideband oxygen sensor and controller
•    4x Denso 330cc injectors with new O rings (swap straight in)
•    Bosch throttle position sensor (bolts onto standard throttle body without modification)
•    Plug and play harness for TPS
•    Plug and play harness for air intake temp sensor
•    fully programmable ECU comes with two 4 bar map sensors (one for barometric correction, good for mountain runs) and has been modified by the manufacturer for the Bosch TPS. Everything is tuned and ready to go but it is still under warranty if you need support. The ECU plugs into the standard Mazda loom and nothing has to be cut or modified. The ECU has wideband O2 feedback, datalogging with autotune, launch control, flat shift and heaps of other features.

I have sacrificed a standard TPS to create the plug and play harness, so to fit this kit you won't have to cut any wires or do anything irreversible to your car at all. Everything has been done properly, no "band aid" solutions have been used.

cheers guys.

Will the JR boost controller cope with bigger injectors? I know its not programable, just a set of maps that you adjust with a dial...

thanks

Rob 

 My Google-fu appears to be weak, as I can't find instructions for the JR boost controller, but assuming it's designed to add fuel when the car's in boost, it won't help you at all.  The problem with combining big injectors and the stock ECU is trying to stop it injecting too much fuel when you're not in boost, rather than too little fuel when you are.

Cheers - thats the problem I'm having - can't find anything on the JR stuff. I've got some partial installation instructions from the previous owner, but bugger all else...

I'm getting a new hood done next week, then I was planning to look at a proper ECU kit when I've saved up another £500 or so!

 Go at it a different route.

Fit a intercoolers and drop the intake temps.this will help.

Or

for abou £80 you can fit a AFPR which will increase the fuel presure (more presure per injector cycle = more fuel) when you go into boost.

Or

cheapest is to fit a dual feed rail so that at high revs no 4 (the furthest away from the feed) dosnt start to run lean due to the 3 other injectors "stealing" the Fuel from the rail

you can make one quite easily.

http://clubroadster.net/vb_forum/showthread.php?t=22379

buy one

http://949racing.com/m-tuneddualfeedfuelrail.aspx

Alan

Cheers.

I've got the big boost kit fitted which comes with an uprated fuel pump and AFPR.

I've thought about the fuel rail - so thanks for the links...

ta

Rob