Turbo mx-5 injector size

Russellb · Postby **Russellb** » Tue Jul 17, 2007 8:24 pm

550cc RX7 injector do get a bit hard to control at Idle
But with a Sard Regulator have managed to get them to perform
correctly.
depening on the power you want the 440 cc injector will handle up to
170RW KW

blackster · Postby **blackster** » Wed Jul 18, 2007 1:55 am

01-05 NB injectors are 265cc and can handle 135rwkw with the stock fuel pump.

Fuel Injection Sizing Formula

After much research it has been found that there are several different formulae used to determine injector size. It appears that most of the various formulae in use are basically identical, with only 2 real variables, being whether or not an 80% duty cycle is accounted for and what the desired Brake Specific Fuel Consumption (BSFC) should be. This is the formula with the correction based on the duty cycle:
Flow rate (lbs/hr) = Max Hp x BSFC / no. injectors x duty cycle

BSFC = 0.45 - 0.55 for naturally aspirated engines
0.55 - 0.65 for forced induction engines
Conversion from lbs/hr to cc/min = lbs/hr x 10.515
Simplified max Hp x 1.807 (nat) Simplified
max Hp x 2.136 (turbo)

450 cc should handle 170rwkw with the OEM fuel pump with about 10-15 % left before hitting max duty cycle. With a decent fuel pump you could push more.

How many ponies are you looking for?

16bit · Postby **16bit** » Wed Jul 18, 2007 8:52 am

I would avoid 'over injecting' your car. If you are going for say 150rwkw which is probably all you will get safely with a stock motor then I would go for familia gtx 330cc injectors. I have got 200wkw out of 440cc injectors but that was with a malpassi reg (avoid sard regs - i have heard nothing but bad about them) and bosche motorsport pump. So there is no need to go that big with a stock 5 motor

The Pupat · Postby **The Pupat** » Wed Jul 18, 2007 1:00 pm

16bit wrote:I would avoid 'over injecting' your car. If you are going for say 150rwkw which is probably all you will get safely with a stock motor then I would go for familia gtx 330cc injectors. I have got 200wkw out of 440cc injectors but that was with a malpassi reg (avoid sard regs - i have heard nothing but bad about them) and bosche motorsport pump. So there is no need to go that big with a stock 5 motor

I've heard exactly the opposite.

Malpassi are poo.

Sards are good (but expensive). My mate got a turbosmart one SH cheap but the car hasn't been tuned yet so no comment if it's any good or not. They are supposed to be alright though, he usually researches the crap out of stuff and usually avoids buy stuff that won't work.

16bit · Postby **16bit** » Wed Jul 18, 2007 1:14 pm

The Pupat wrote:
16bit wrote:I would avoid 'over injecting' your car. If you are going for say 150rwkw which is probably all you will get safely with a stock motor then I would go for familia gtx 330cc injectors. I have got 200wkw out of 440cc injectors but that was with a malpassi reg (avoid sard regs - i have heard nothing but bad about them) and bosche motorsport pump. So there is no need to go that big with a stock 5 motor

I've heard exactly the opposite.

Malpassi are poo.

Sards are good (but expensive). My mate got a turbosmart one SH cheap but the car hasn't been tuned yet so no comment if it's any good or not. They are supposed to be alright though, he usually researches the crap out of stuff and usually avoids buy stuff that won't work.

Well I have used malpassi and it was good and very consitant. can't say i have used a sard but people who have used it through it out within a week of it being installed. could have been a dud batch of sorts.

Blue94t · Postby **Blue94t** » Wed Jul 18, 2007 1:18 pm

Apsilon,
It's still putting out 160rwkw. Still got the 370cc injectors
It now has a larger capacity in tank pump and I got rid of the Bosch pump that had been put in in series after the in tank pump. It will be getting a surge tank set up soon.
Jake

hot rod · Postby **hot rod** » Sat Jul 21, 2007 9:56 pm

The Pupat wrote:
16bit wrote:I would avoid 'over injecting' your car. If you are going for say 150rwkw which is probably all you will get safely with a stock motor then I would go for familia gtx 330cc injectors. I have got 200wkw out of 440cc injectors but that was with a malpassi reg (avoid sard regs - i have heard nothing but bad about them) and bosche motorsport pump. So there is no need to go that big with a stock 5 motor

I've heard exactly the opposite.

Malpassi are poo.

Sards are good (but expensive). My mate got a turbosmart one SH cheap but the car hasn't been tuned yet so no comment if it's any good or not. They are supposed to be alright though, he usually researches the crap out of stuff and usually avoids buy stuff that won't work.

Aeromotive products have a pretty good rep in this department.

Boags · Postby **Boags** » Mon Jul 23, 2007 7:18 pm

Go to http://www.miataturbo.net.

As much as all the members are red neck hicks, the info is good. Just troll the site and find the info on injectors. The have formulas for the injector size you need based on the power you want, engine capacity, fuel pressure and boost.

Everything you need and a metric sh!tload that you don't.

Boags

Fatty · Postby **Fatty** » Mon Jul 23, 2007 7:21 pm

i don't get why you need a rrfpr. i thought that 440's would be good for 200 rwhp with the stock fuel pump, and no additional assistance, but i could be wrong ( i often am :mrgreen:

)

Boags · Postby **Boags** » Mon Jul 23, 2007 7:25 pm

Fatty wrote:i don't get why you need a rrfpr. i thought that 440's would be good for 200 rwhp with the stock fuel pump, and no additional assistance, but i could be wrong ( i often am )

I think the only issue would be fuel pressure. AFAIK 440s should be good for 200wHP on the stock pump though.

Silverback - save your money on the 255 and get the 190. The 255 has been known to pump too much fuel at idle (some have said that their idle is fine with it though...).

Boags

blackster · Postby **blackster** » Sun Jul 29, 2007 11:45 am

silverback2002 wrote:I already have the equipment and the pump is installed. I just need some injectors now to complete everything.

Has anyone every used RC engineering 550 cc injectors. Not sure what they are like.

I been told to use siemans they are ment to be good quaility.

Low imped or High??? will run with my wolf v500

Flyin miata resells the RC 550 cc injectors with there hydra, they are low impedance therefore you will need to manipulate the fuel harness to get them to fit (NB models). That being new connectors have to be spliced into your injector harness, unless you purchase a second harness that supports direct drop low impedance injectors.

It would be easier and cheaper just to purchase 450cc or 550cc that are high impedance.

Boags · Postby **Boags** » Thu Aug 02, 2007 10:21 am

Boags'MX5 wrote:Go to http://www.miataturbo.net.

Your questions have been asked and answered around 4 gazillion times on that forum. There is sticky in the DIY section called the DIY FAQ. It explains everything. Read it. Read it again, then search that forum if you are still confused about anything.

A 255 and 550cc injectors will not be easy to idle well. Good luck.

Boags

4sfed5 · Postby **4sfed5** » Thu Aug 16, 2007 8:52 am

im running 145RWKW or so on my 330's in my 1600...getting about 75% duty cycle at redline......

I wouldnt put any weight on those injector size calculators.......thet just dont stack up with real world numbers produced on the dynos.....Americans LOVE to overfuel thier cars.....440's will be fine....