to get or not to get FPR?
 

OMG confusion, I'm getting two answers, now that i have a MSPNP and larger injectors (460cc), is there any point in having an after market FPR?

from what one person says is that i need a 1:1 so that for every 1psi of boost i get i get 1 psi of fuel so the boost does not try to force the fuel back

other guy says that i can adjust the injectors to stay open longer and that FPR is just another thing that can go wrong

are they both right/wrong or who is "mostly" right

what would you suggest?

your oem fpr is a 1:1.

you do not need an FMU whatsoever.

be prepared to support something like 300BHP as is.

There are a few ways to get more fuel.
Bigger Injectors
More Injectors
More Fuel Pressure
Longer Injector Pulse

Since extra injectors are a huge pain, if you can't modify the injector pulse length, then your stuck with bigger injectors and more pressure. But if you can modify the pulse length (as YOU can with MS), more pressure isn't needed if you use a big enough injector.
In other words... NO, YOU DO NOT WANT AN AFPR. Leave it out.

I have read on this forum and others as much as I can about the Mega and will order a DYI kit shortly but would value the opinion of you experts on this question.
The project. I have put together a DIY turbo for my 1990 1.6. The turbo is formerly from an Eclipse and I have set up a saab intercooler to go with it. Intercooler pipes come forward and over the lowered rad to the IC and back up and over to the TB. I have a BOV installed as well. The car is a project and was not running when purchased so I installed all OEM stuff and have it running perfectly. Currently I am in the process of installing the turbo and IC etc and then getting it running with OEM ECU. The car will not be driven this way just started and run to insure everything works as per good advice from several here as well.

The next step will be to build and install a mega squirt doing away with the AFM. We do not have a dyno in our town so all tuning will be seat of the pants. I also do not have a HP goal but just want a little more power. (No spec racing local either).

I have read the great turbo FAQ (Big thank you for that!)but I am not quite clear on the fuel side. I bought a rising rate FP controller but I really do not think I will need it with mega squirt. Is that correct? I do not plan to increase size of the injectors etc. although if your predictions are correct I may become addicted to the power. BTW this is my 3rd Miata, one 91 with an Escort GT 1.8 I installed, one 90 stock 1.6 and then this one as above.

that is not correct. you WILL need to increase fueling more than the stock injectors can do at stock pressures. that means even with the MS you will need bigger injectors and/or more pressure. increasing the opening time of the injectors will increase your fuel, it's referred to as the duty cycle of the injector. go with too high of a duty cycle and the injectors can get stuck open which will dump fuel uncontrollably into the cylinder possibly causing hydrolock which can bend rods.

my advice, get the biggest injectors you can 440cc-550cc and you'll have as much as you ever need.

no, you do not need the FPR with MS...im new to this as well and from all the research i have done, you do not need a FPR, larger injectors are a fairly easy uprgade with MS down the road, but save yourself some time and money and get rid of the FPR...keep reading about the MS and get real familiar with its abilities, the more you know the more you will like it
i would recommend that you at least go with the 1.8 injectors for now, which can be had for +-50 from our classifieds here, good people for the most part
GL in your build

read the firs tline of the FMU sections of my faq.


the only thing an FMU does is increase the pressure in the rail. and in return it increasing the fuel capacity of the injectors.

with an EMS that can control whatever injector it needs, you dont need to use it in conjuction with an FMU.

but if however, you had a MS and small 265cc injectors, you could use a FMU as well to support greater HP

im a bit confeused, most everything i read recommended bigger injectors vs FMU if using MS...i know im newb at this but it makes more sense to me to go with bigger injectors, just something about miatas catching fire due to blown fuel hose scares me

Dlaitini doesn't need the FMU as he has larger injectors.

Kenny will need more fuel. The FMU is one way to do it but if going with the MS larger injectors are a better solution although the MS and the FMU can work together.

thanks for clearing it up, i hate to be a thread pirate but it beats starting a new one over something already debated x# of times
thanks
Dan

OK I think I understand. I will go with 1.8 injectors (or larger if I can get them for a good price) and leave the FMU out for now. When the urge for more HP gets too great and my experience in MS has increased I will have take it off the shelf and another look at it. Thanks again guys!

several sets of supra greentops(305cc) for sale in the classifieds at good prices https://www.miataturbo.net/miata-parts-sale-trade-5/

even i'm selling a set...

until you can't start your car on a brisk autumn day... :bigtu: