720cc's safe for streetport, etc...?
 

Hey everyone,

I'm reading around and trying to find out some info on 720's and using them for my new setup. I do not want to risk running out of fuel. I recently blew my motor in my TurboII @ 121k original miles. Setup that I ran for about 3.5 years.

-GReddy fmic kit
-GReddy profec-B spec I
-S5 turbo and manifold
-Rtek 1.5 w/ 550 (primary/secondary)
-HKS SSQV bov
-Racingbeat REVII turbo-back
-10psi

Upon tearing my old block down we noticed that my rotors, exhaust ports, turbo manifold etc were white and brownish. But regardless... here's what I'm doing now.

-Streetported rebuilt motor
-GReddy fmic kit
-GReddy profec-B spec I
-S5 turbo and manifold
-GReddy type-RS bov
-Racingbeat REVII turbo-back
-PLX wideband
-10psi

I'm wanting to hear from some of you who might be running a similar setup if possible. I'm currently dwelling on the thought of the following:

-Rtek 1.8 ECU
-720 primary/secondary
-FD or Supra pump

Any info or advice would be appreciated. Anywho... thanks for your time.

-Allen G.

First problem I noticed on your first setup is the lack of a bigger fuel pump.

for stock turbo 550/720 is enough.

that looks fine to me. you might be able to run with 550/720s but it can't hurt to have dual 720s.

one thing you might want to look into if you have stock high impedance injectors are Injector dynamics 725cc high impedance injectors, otherwise you'll need inline resistors.

http://injectordynamics.com/

it's an early '87 so it already has the resistor pack. Thanks for the input guys! :)

Run low impedance injectors with the resistor pack and you are Fine.
I got the 1.8 with 750's and a FD upper conversion..It runs very well.(just a Wierd Tps issue that I can't figure out,but all in all the car Runs like a Scalded Dog when I hit Boost!)
My Fuel pump is a walboro 255 with aftermarket lines running a parallel setup on the rails.the Fuel regulator is set to 45.
.Oh,and the Wiring harness is an S4 N/A put on the S5 keg with s4 components..BNR Stage 3 Turbo.
So far,it has been Good,So if that is your Cup of Tea,I can suggest that it would be OK for you too.
I am going to go to an RTEK 2.1 shortly to Maximize it's potential,as I am not really familiar with Haltech ECU or others.
anyways,I hope the Parts I mention give you insight as to what kind of setup you can depend on.Cheers STYX.

I use to run a similar setup:
-streetported TII s4
-walbro 255
-750 secondaries
-fmic
-rtek 1.7 with a safc neo
-stocker turbo on 10-13 psi


AFR's usually stayed around very low 11's at 11psi based off a NGK AFX wideband.

i like the 720 + bigger pump route. the 10% more injector and 20% more power works out really well on the stock ecu

Wow thanks guys! So if I fan find 750s then those will work as well with the 1.7 or 1.8 if going both primary and secondary?

You'd be better off with the Rtek 2.1 it woudl allow you to get the most out of your current setup. 4x720's sounds good, but take that extra 2x720 money and put it towards the 2.1 because 550/720 is good to 300hp (as is an FD pump) and you'll never make that on the stock turbo anyway (auxillary injection/ NOS/Jesus aside....) Plus the 2.1 allows you to control timing which will provide an added safety factor and allow your to account for that streetport properly in tuning.....oh, and then there's the datalogging. /Rtek commercial :lol:

The Rtek isn't a permanent setup... Merely a "safer than a stock ECU" crutch until I'm finished with the break in... one that can run the fuel setup. I would like to eventually move over to a Haltech E6K or Platinum 1000 after the break in.

750's will work fine on 1.8

How do you know the difference between high impedance and low impedance?

What turbo do you plan to run after break in?

you can measure the injectors with an ohm meter.

high is 12-15ohms

low is like 2-5 ohms

if you're looking at an assembled car, the low impedance cars have a resistor pack under the airbox.

Ok. I was thinking something along those lines but I wasn't sure.

I'm really undecided between a BNR hybrid or a Borg S360. Granted the 750s wouldn't be sufficient for either but I can sell those and run 550/1680s on a haltech when I go that far.

Correct me if I’m wrong but when upgrading to a FD pump or Walbro 255, don't you need to run a fuel pressure regulator?

^No.

No, you cannot run w/o a FPR. :wink:

With an upgraded pump you 'might' overwelm the stock FPR and have an elevated Fuel Pressure, resulting in flooding, richness over all rpm.

With a Walbro 255 and fuel pump variable resistor bypassed I had to have a Adj FPR to retain Factory Base Pressure. Actually, just from the rewire, I had to lower it.

^ That’s what I was talking about (sorry I should have said aftermarket/adjustable FPR), so then it is a good idea to get an aftermarket FPR when upgrading your pump.

Sorry OP we kind of got off topic, but the reason I asked this was because in your list of mods you didn't put down an aftermarket FPR and seeing as how you’re asking about running 720cc injectors for safety reasons then I would suggest running an aftermarket FPR also. Just my 2c.

It depends on the pump. If it's like a walbro and flows a ridiculous amount at low pressures, you'll benefit from using an aftermarket FPR. An FD pump flows very similar to a stock TII pump at low pressures, but it has the benefit of actually being able to flow well at higher pressure levels.

Some pressure info:
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/measured-flow-stock-tii-pump-524944/#post9154530
http://www.stealth316.com/2-fuelpumpguide.htm

^exactly what I was looking for, thank you!