Zaz1920

iTrader: (1)

Hey guys,

So I'm going single and have decided on the Turblown Borg-Warner 7670 EFR kit. Target is 350-375 rwhp. Right now I have a 850cc primaries and secondaries, supra fuel pump, stock lines, stock rails (with a modified primary to fit 850cc's). Do I need to upgrade my secondaries to meet my power goal? I talked with someone from Turblown and he was very helpful but didn't have much experience with the square injector setup I have. Anyone else have any advice?

Thanks,
Ryan

Topolino

iTrader: (2)

Try playing with this fuel/HP calculator by changing the secondaries to 850 and the duty cycle to 85%. Looks like you'll be fine with your setup.

Fuel System Calculator - Wannaspeed

Should you feel the urge to upgrade your fuel capabilities further, and you want to do it in a very simple/practical/cost-effective manner, here is another good link for you. Keep it simple, friend!

https://rotaryperformance.com/collec...00cc-injectors

Note: Unless you are planning on running boost higher than mid-teens and or running non-pump gas, expect to achieve closer to 325 HP (vs 375) as the eventual power output for your turbo selection.

Slides

Yeah 4x 850 with enough pump to maintain pressure should take you very close to choked air flow on that turbo.

Zaz1920

iTrader: (1)

Thanks so much for the help guys. The fuel system calculator is nifty. I hadn't seen or heard of one of those before.

I did forget to mention that I have a Judge Ito 'Aggressive Street Port' which is why I expect to make slightly more power than the 325rwhp I've seen made on a stock motor with that turbo.

In talking with the guy from Turblown he said that where my fuel system will be stressed is when I'm making max torque lower in the rev range instead of max power later on. That makes sense to me but makes it harder to calculate exactly what I need.

I don't plan on running higher than mid-teen boost and plan on using pump gas.

Slides

Midrange injector dead time:available open is less. Peak power is the critical point for fueling. Peak torque usually shows ignition limitations.

Skeese

iTrader: (11)

That's where the max VE numbers will be in the fuel map, which are not directly representative of the actual pulsewidth and resulting fuel flow going on. VE numbers are just arbitrary scalars to the VE calculation.

Peak actual fuel consumption will be at max horsepower, and HP is simply a mathemaical calculation based on torque and rpm, where as rpm increases, horsepower insreases and as the motor is spinning faster you'll have to flow more fuel to hold the same afr as at lower power/ lower rpm

not the same as VE

Skeese

cr-rex

iTrader: (114)

If it's any help, I made 350whp with 1300/850 and a supra pump with the 12v rewire as the only fuel mods on a street port and gt35r at 10lbs. Not sure how your turbo compares but those were my results.

RoboticsRacer

I think weather or not your fuel system will be sufficient may depend on how rich you are looking to run at high load high rpm. I’m running stock primaries and ID1700 secondaries with a fuel pressure of 42psi from a "relayed" walbro GS3S42. My fd is stock port and made 344 WHP at 13.5psi with the Turblown 7670 cast iwg kit. I’m running right around 15psi now but pretty rich (about 10.7afr under high load). At 15psi I see about 80% duty cycle max on my secondaries.

Howard Coleman

iTrader: (6)

as always, you start w max air from your turbo.

64/66 pounds per minute. let's use 66. absolute stall at 66. no more air.

66 pounds air. at 10.0 AFR is 6.6 pounds per minute of gasoline.

6.6/ 6.35 = 1.04 gallons per minute. 3937 CC/Min NET into the engine.

adjust for 85% duty and lag and you need 5315 GROSS at 10.0

66 pounds per minute is 497 rotary rwhp. (remember this is absolute max from the turbo)

your max target is 375 so 375/497 = 75%.

.75 X 5315 = 3986 Gross injector you have 3400 which is pretty close and you will not be tuning for 10.0 AFR, probably 11.0 at that power level.

ideally, when you set up fuel it should be enough to run the turbo max at 10.0 so if you have a boost malfunction you are covered.

the last Judge Ito secondary port i saw ate sideseals so hopefully that is all corrected.

Zaz1920

iTrader: (1)

First of all, thanks for taking the time to walk through it all Howard - it's greatly appreciated. I had a few comments/questions/concerns for you regarding the math.

First of all, I found this forum post that lists 497hp @ 66 lb/min of air for the BW EFR 8374. Since I'm looking at the BW EFR 7670 I corrected to the values provided for that - 391hp @ 52 lb/min of air.

https://www.rx7club.com/single-turbo...urbos-1029558/

Next, for correcting for the 85% duty cycle and lag you added 35% to get from 3937 cc/min to 5315 cc/min. Why didn't you just divide by 0.85? I understand the duty cycle but I'm still not sure I fully understand the injector lag correction. If there's a latency for the injector to open, isn't there also one for the injector to close mitigating the need for a flow correction?

Lastly, isn't an AFR of 10 quite rich? I know there should be enrichment at WOT but 10 seems a little excessive. Is 11 or 12 reasonable?

I'm not trying to nitpick with these but since I'm right on the border of needing bigger injectors being overly conservative will just push me over the limit.

With the numbers for the 7670 I found that I have enough injector for an 11.75 AFR at 375hp using the following calculations:


Does that look correct? At this rate I'm thinking I won't need to upgrade because I'll probably be going below 375hp, but we'll see.

Thanks again,
Ryan

Howard Coleman

iTrader: (6)

as you can see the 7670 maxes out at 66 pounds per minute. of course you can elect to run it at any output level with your wastegate and boost controller. i suggest when fixturing a turbo setup that you include enough fuel delivery to match air output so you can use the turbo at max output if you wish and also be able to tune it to any AFR. of course 10.0 is rich but there can be line losses etc. i am just being conservative. feel free to do as you wish.

once Net fuel is calculated you have to plus up to get to Gross which is the number most people reference. there are two factors. Duty Cycle which many often use as 85% and Lag. the amount of Lag varies w the type of injector, battery voltage as well as pressure. Lag is simply opening and closing slippage. it is empirically derived and i use 13%.

100 X.85 = 85 X .87 = 73.95
100/.7395 = 1.352

3937 X 1.35 = 5315 Gross CC/Min to match 66 pounds of air per minute at 10.0 AFR

as to your 375 and 11.75 AFR...

375/497 = .75

3937 X .75 = 2952 Net at 375 at 10.0

10.0/11.3 =.884

2952 X .884 = 2609 CC/Min

2609 X 1.35 = 3522 CC/Min Gross Injector to make 375 at 11.3 AFR

you have no safety net for any higher air output and no ability to tune below 11.3.

i personally would never assume that you will not get overboost at some point although i will say there are tuning options that might protect you depending on your ECU. you could also raise static fuel pressure a bit but you only get the square root of the increase... i e, pressure up 9%, flow up 3%.

important other considerations:

anyone running a single needs a hardwired fuel pump. pump output is hugely related to voltage. pump output is generally rated at 13.5 V. if you have not hardwired your pump it is seeing much less.

i mentioned line restriction. my ECU measures Differential Fuel Pressure (DFP). the stock return line over (around) 400 hp adds 10%+ restriction thereby decreasing system flow. many who don't measure DFP are not aware of this and as they ramp the boost they compensate by increasing injector ontimes but this is a losing battle.

you do run AI?