ok just what the title says. How much hp would be safe with this combo??? Also how much hp is safe on the stock 550/550 combo?

edit: now I'm talking about these injector combos with a fuel pump upgrade and rewire.

 

just let me know

 

no input on the subject??

 

LOL!!! I wouldn't know, but if it makes you feel any better,



SURE!!!

 

thanks for the input :-P

 

Most I have heard of on the stock inj/pump is 249rwhp from a friend of mine who saw it on the dyno. Spd racing claims he saw 269rwhp on stock inj/walrbo. Personally I maxxed out the stock cleaned inj/walbro @ 11psi on my s4 turbo/motor. I'm not sure on 720s 300-300rwhp safely?

 

see thats what I've been saying but someone else on this forum is saying not possible. Can anyone else confirm this??? Also it says 300-300rwhp what exactly did you mean??

 

http://rx7.com/cgi-local/2ndgencalc.cgi

rx7.com has a fuel calculator

 

I've seen this calculator before just to dumb to use it correctly. I guess I would just put in the max duty of 550's witch I believe isn't smart to go above 80% right? if that is true than the stock should be good to 250hp. the 720cc's would be good for about 300hp at 80%

oh ok just saw the warning if you go above 85%

so stock would be 270hp and 720cc would be 311hp.

 

Fuel calculator are kinda worthless unless you know your BSFC....
http://www.maxcooper.com/rx7/how-to/...tem/calcs.html

More accurate site...

 

I used that calc to plot out my setup. 332hp w/ 720cc all around, 300 hp with just the 720cc secondaries.

I think that's pretty safe.

 

... and fuel pressure.

It's probably not a good idea to mess with your car if you guys don't know this stuff.

 

use a bsfc of about .85 on a stock ecu/stock mixture application

 

Prior to upgrading injectors, a Walbro 255 with proper voltage should be installed and the fuel pressure checked in the line... Of course, we should all know that already.

 

Asked my tuner, Tom at RotaryRX the same question. He said that without upgrading the exhaust system the benefits on upgrades to fuel system would be minimal. This makes sense to me, as a NooB, since logically it is the fuel and air combination that drive hp. So I'm going with the RB 3" exhaust system and upgrading secondaries to 720s or 750s with a Walpro FP. Also a lightweight steel flywheel.

Is this observation too simplistic?

 

well I mean I would just like to know how much hp is possible out of these injectors, period, with all the mods. I think the general rule of thumb is 550s all around is 250-260 hp where the 720cc secondaries are good for 300-315hp.

 

720's are about 15% more fuel, so that gets you from about 250 to 285

 

how is more fuel going to just get you the same as what the stock injectors are good for??? The stock injectors are good to about 250-269hp so 15% more would be in the 300hp range.

 

I was gonna say about 280.

BTW 250-269 hp is a big range, I think the correct number is 250 for the stock setup. Sure some people go more--but they are rolling the dice. Remember fuel requirements depend on many factors and 9/10 times could be OK, but it just takes that one set of conditions to pop your motor.

HTH,

Scott

p.s. I'm running that exact setup with the Rtek 1.7

 

so if the stock ECU limits the max. injector duty to 58%, does that mean even with a SAFC you can't increase past 58% without an ECU upgrade?

 

from what I've heard the that 58% deal is just a myth!

 

It is.


There is however a raw afm limit before the secondaries come online. This is all covered in henriks various threads on teamfc3s.

With stock fuel pressure and 11:1 air fuel ratio, I believe a 550/720 combo will max out a little north of 270. (had a typo in the other thread covering this) This is a conservative estimate, but it's somewhere in the ball park.

What I really would be worried about is being able to run lean before the secondaries come online. I know the rtek ecu has the secondary activation point dropped a few hundred rpms, but with a large hybrid turbo it's still feasible to be making some serious boost before the secondaries can come online even on the modified ecu.

 

hey what kind of numbers are you making with your bnr stage II??? I thought that thing was good for about 310hp???

 

I have no idea. I haven't been to a dyno in nearly a year and a half. I'll try and get an old IC kit on the car then take it the dyno by spring sometime. I do plan on taking it to the track again this thanksgiving. It feels like a high 12/low 13 second car right now. I'm expecting a trap speed of around 108-109.

 

do you still just have the 550's and 720's??? If so don't you think you are making 300 or so with the stage II??? and if you are wouldn't that setup not be enough for the 300 or so you are running?