osiris7442

I was just hoping I coudl get a feel for how extensive a fuel system i need to safely run 12-15 psi
can I go with injectors, walbro pump, run by an safc....or do i need a full blown stainless setup with new rails and all the sexy red and blue fittings i've seen lately

also would an safc be adequite with the extensive setup..or is standalone manditory?

slo

iTrader: (1)

12 PSI on small turbo is not the same as 12PSI on a big turbo.

osiris7442

well BNR stage 4 for example

feel free to flame me if im being retarded, i do try to answer questions without asking

rx7legend

to run 12 psi safely ill say you need injectors preferably 720cc secondarys, safc or an Rtek, walbro fuel pump and ill say your good to go but this is if you are still running stock turbo, if you're running a bigger turbo then its a different story. ohh and if your running stock turbo don't pass 12 psi because after that your not getting almost hp and the turbo will start to blow hot air. if you don't have an exhaust consider doing one or buying one because is goona give your TII a lot of live.

later

slo

iTrader: (1)

I would go with 1000 CC injectors primary and secondary. Assuming you have a good standalone and a good tuner you will have no problem running this combo.

This would give you a good saftey margin for the BNR stage 4.

JCurry

iTrader: (6)

maybe im stupid but wats the deal with 12 psi isnt the same on a big turbo as a small turbo, isnt 12 psi, 12 psi?

slo

iTrader: (1)

efficiency, A bigger turbo has a lot less pressure in the exhaust side for a given boost pressure. Many people here can explain the why allot better than me.

A good example of this is a well tuned car with the stock turbo making 250 WHP at 12 PSI. As compared to the same car with a monster turbo making 400 WHP at the same 12 PSI.

Fuel mods need to be made by considering HP and BSFC, not PSI or some other variable.

Juiceh

iTrader: (4)

I believe the idea is that the larger compressor can flow more volume while at the same time being more efficient and not heating the air as much at the same psi. So you basically get more dense, cooler air comming out of the turbo at the same psi.

sleepydave

its pure geometry. blow through a coffee stirrer, now blow through a mcdonalds straw, or a toilet paper roll for that matter. 12psi in the coffee stirrer is less cfm of air than 12 psi in the mcd's straw.

osiris7442

excelent analogy guys thanks for your help

RotaryEvolution

iTrader: (30)

the analogy is flawed because the straw would not be the turbo but the intake system, it is hard for people to understand because the intake system is not changed yet the volume of air is greatlyincreased at the same PSI. i can't even think of an analogy to properly describe it.

slpin

iTrader: (9)

wow orsis... do you even know what psi is?

buttsjim

So, I guess both turbos flow the same VOLUME of air, but because the more efficient larger turbo heats the air less, and the air is therefore more dense, the larger turbo will flow a higher MASS of air.

buttsjim

^ Never mind my comment about the same volume. The larger turbo would move a higher volume and mass--the air would just be moving faster. I guess my brain must have been on break, or something.

slo

iTrader: (1)

In a stock turbo system at 12 PSI there can easily be four (or more) times that amount of pressure in the exhaust manifold before the turbo. This is half of the efficiency equation. A turbo isn't free power. The engine has to push against this back pressure. A good aftermarket turbo system depending on the AR and exhaust can easily have half the back pressure behind the turbo.

This is why the BSFC for a turbo engine goes up. A rotary engine looses allot more of its energy through the exhaust than a piston engine. The BSFC of a turbo rotary actually changes far less (when compared to the same engine being NA) than the BSFC of a piston engine of equivelent power because of this fact.

PSI being equal (such as 12 for example) and intake air temprature being equal, such as after going through an ice box. you have the same CFM of air going into the engine.

How quickly and efficently the engine can intake a particular boost pressure is another matter entriely. It stands to reason than (provide all internal components can stand up to the punishent) an engine that make the most power NA will make the most power in a turbo application.

slo

iTrader: (1)

I actually didn't mean the same CFM I mean you have the same mass of air in a given space at the same pressure and temprature. CFM is a measure of flow. The reason why you don't have the same CFM is because of the more restrictive exhaust side of the turbo. The analogy above of a straw is correct well sort of, but the straw is't the intake its the exhaust before the turbo.

To make a sligtly more complicated but effective example immagine if you supplied forced air into an engine on an engine dyno from a remote source. got the engine making say 200 hp at 10 PSI. Then you put a very restrictive exhaust on the engine. The engine would not be able to pump as efficently. Your HP would drop and for the same cfm of air the boost pressure would rise, yet the engine would take the same amount of fuel to run the same AFR. The intake and exhaust temps would go up.

To get back to 200 HP you would need to supply the engine with more CFM of air and more fuel which would concequently bring the boost up even more.

NOPR

um, no. there is absolutely no need to run 1000cc primaries. 550 primary 1000 secondary would be more than enough, and 550 x720 would work. but trying to tune 1000cc injectors to idle at 1000rpm would not be something i'd ever want to do. not to mention its pointless.

slo

iTrader: (1)

I actually didn't mean the same CFM I mean you have the same mass of air in a given space at the same pressure and temprature. CFM is a measure of flow. The reason why you don't have the same CFM is because of the more restrictive exhaust side of the turbo. The analogy above of a straw is correct well sort of, but the straw is't the intake its the exhaust before the turbo.

To make a sligtly more complicated but effective example immagine if you supplied forced air into an engine on an engine dyno from a remote source. got the engine making say 200 hp at 10 PSI. Then you put a very restrictive exhaust on the engine. The engine would not be able to pump as efficently. Your HP would drop and for the same cfm of air the boost pressure would rise, yet the engine would take the same amount of fuel to run the same AFR. The intake and exhaust temps would go up.

To get back to 200 HP you would need to supply the engine with more CFM of air and more fuel which would concequently bring the boost up even more.

slo

iTrader: (1)

He said a BNR stage 4 turbo. A BNR stage 4 turbo made over 400 WHP thats what 450 FWHP. Are you telling me that 550 720 or 550 1000 would support that much power at a resonable duty cycle with any reserve what so ever. I don't think so.

http://www.injector.com/injectorsele...55c5c363a00c9c

With a BSFC of .65 and a limit of 80% duty cycle marren suggests 4 850 CC injectors for 400 FWHP. The BNR stage 4 is easily capable of 400 FWHP at 15 PSI. That significantly more than 1000/550.

I have seen rotaries that idled just fine on 1000 CC primaries. whith a good standalone.

Go post the fact the "1000 CC primaries are hard to idle on" in the haltech section

https://www.rx7club.com/showthread.p...00cc+primaries

RotaryEvolution

iTrader: (30)

550pri and 1000sec would be pushing it, best bet with a stage 4 would be to run a standalone and 1000cc all around or 720pri and 1000sec or 720pri and 1600sec

osiris7442

would a SAFC II be abel to control the larger injectors well enough to have a safe tune? or is a full stant alone a must
?

slo

iTrader: (1)

I wouldn't try and run a piggyback fuel only computer on a 400HP car. Even if it could controll the largest fuel injectors in the world, you need full controll over the ign and the split. Thats the type of thing that is used as evidence for the "modified turbo rotary cars can never be reliable" argument