Will this fuel setup work?
04-16-10 | 01:14 PM
#1
Will this fuel setup work?
I'm currently running 15psi on non-sequential stock twins on a race ported motor. I'm running a Walbro 255 and 4x850cc injectors for fuel. The problem is that my injector duty cycles are ranging from the low 90's to the upper 90's and I know I'm going to have to do something about it.
I was thinking of installing 1300cc secondaries and leaving the 850's in the primaries. I just wanted to make sure that the stock fuel pressure regulator will be able to keep up or if there might be any potential problems that might come from running this setup.
Any input from you guys would be great.
I was thinking of installing 1300cc secondaries and leaving the 850's in the primaries. I just wanted to make sure that the stock fuel pressure regulator will be able to keep up or if there might be any potential problems that might come from running this setup.
Any input from you guys would be great.
04-16-10 | 01:26 PM
#2
While I have your attention I do have another option. I have 2 extra 1000cc top feed injectors from another RX-7 build that I could potentially use in the secondary spots.
This is what they are. http://www.rx7store.net/product_p/ro...r%201000cc.htm
Does anyone make a top feed rail that would work with these. Also, would this work with the stock fuel pressure regulator
This is what they are. http://www.rx7store.net/product_p/ro...r%201000cc.htm
Does anyone make a top feed rail that would work with these. Also, would this work with the stock fuel pressure regulator
04-16-10 | 09:47 PM
#3
just about any top feed rail will work with those top feed injectors, why don't you just go big and get 1680s and a top feed rail? Doing a top feed rail in the secondary location is an absolute bitch with the LIM still on the motor, I just finished doing mine, not fun.
what exactly are you goals? I keep howards post's handy for figuring stuff like fuel needs out
what exactly are you goals? I keep howards post's handy for figuring stuff like fuel needs out
Much of this post can be found scattered around this board but i thought it would be a good idea to put it all together and add in alternative fuels such as ethanol and methanol.
The rotary is, of course, unique and as such it would be a big mistake to use piston metrics when planning setup.
How unique?
Let's talk airflow:
A piston engine can generally make ten hp for every pound per minute of air, so a 70 pound per minute turbo can make 700 piston hp. As we navigate the web looking at turbos we often see a hp tag... for instance a 73 pound per minute TO4Z/GT500/PT67 is often rated at 730 hp. If you are looking for 730 you'd best look elsewhere because they are talking PISTON lingo.
Should you wish to translate to rotary you'd take the pounds per minute, or the estimated HP number, and divide by 1.3.
73 pounds per minute is 561 ROTARY rwhp.
BTW, that doesn't mean the rotary takes a back seat to the piston engine. While it does take a discount due to lower volumetric efficiency (VE), it makes up for lower VE by being able to flow more air V displacement.
O K, let's get into it starting with airflow and hp.
FDs are all about airfow from turbos.
Most turbos have a compressor map which sets forth maximum airflow in pounds per minute and other metrics such as efficiency and airflow at differing boost levels etc. (see Sean's How To Read a Compressor Map thread sticky in the Single Turbo Section).
This thread is about properly sizing the fuel system(s) so let's just focus on the maximum air as set forth on a commonly used GT3582R compressor map.
Airflow is represented in pounds per minute. The GT35 makes approx 62 pounds per minute max.
Rotaries require 1.92 CFM (cubic feet per minute) to make one rear wheel hp. Transposing pounds per minute to CFM, we multiply by 14.471.
14.471 times 62 = 897 cubic feet per minute.
Now that we have CFM we divide by 1.92 to get rear wheel rotary hp.
897/1.92 = 467 max rotary rwhp.
TO4Z, GT500, PT67 turbos make 73 pounds per minute.
73 X 14.471 = 1056 CFM/1.92 = 550 max rotary rwhp
The GT4294 puts out 85 pounds per minute.
85 X 14.471 = 1230 CFM/1.92 = 641 max rotary rwhp
Now that we have an understanding how to get CFM from pounds per minute and then rw rotary hp let's move on to solving for fuel requirements from air generated.
AFR
Air Fuel Ratio... 10 to 1, 11 to 1, 12 to 1. These ratios are for air and fuel measured in POUNDS.
Back to the GT35r and let’s calculate fuel injector sizing.
I suggest we use a couple of "givens."
"Given" we want to have enough fuel to run 10.0 to 1 AFR if necessary.
"Given" we want to run our fuel injectors at no more than 85% capacity (expressed as duty cycle).
Assuming 62 pounds per minute of air, at a 10 to 1 ratio we need 6.2 pounds per minute of gasoline.
62 pounds air
6.2 pounds gasoline
We wish to limit our fuel injectors to 85% duty so we divide 1 by .85
1/.85 = 1.1764
We now take our adjuster (1.1764) and multiply it times our 6.2 pounds per minute of gasoline.
1.1764 X 6.2 = 7.294 pounds per minute of fuel delivery capacity.
The next step is to convert the pounds of gasoline to gallons. Gasoline weighs 6.35 pounds per gallon.
7.294 pounds / 6.35 = 1.14868 gallons per minute
Off to my favorite "converter" website (http://online.unitconverterpro.com/u...ha/volume.html)...
Select “Gallon” converted to “Cubic Centimeter” (CC) and find that 1.14868 gallons is 4348 CC
So 4348 CC/Min at 85% delivery is 3695 CC/Min net of duty cycle.
That number will produce fuel necessary to service the max air GT35r at a 10 to 1 AFR.
Given the above calculations we can now answer some common FD injector questions…
“If I run my 550s as primaries what do I need as secondaries with my GT35?”
4348 - 1100 = 3248 CC/Min needed in addition to 550 primaries
Run a couple of 1600s and you are fine!
“How about 850 primaries and 1300 secondaries?”
4348 required…
(850 X2) = 1700
(1300 X2) = 2600
Total = 4300… fine.
Moving up to the larger 73 pound per minute turbo... Let’s do it simply by just multiplying by the increase in air delivery V the GT35r..
73/62 = 1.1774
4348 X 1.1774 = 5119 CC/Min
“Will 550s work as primaries?”
5119 - 1100 = 4019 required for secondaries so given our assumptions the 1600s won't work.
“What do I need w 850s as primaries?”
5119 - 1700 = 3419 CC/Min. 1600s will probably be O K, especially considering 1600s generally flow 1680 each.
“How about a GT4294 at 83 pounds per minute?”
83/62 = 1.3387
4348 X 1.3387 = 5820 CC/Min
“What do i need in addition to my 850 primaries?”
5820 - 1700 = 4121 CC/Min
As I understand, the Bosch 1600 injector is no longer being made. There are a few new injectors that have become recently available. I believe there is a Siemans injector that is around 2000+ CC/Min and there is at least one brand of aftermarket injectors that offer increased deliverability w good spray pattern.
Additional injector option info welcomed.
So far, we have been talking gasoline.
We also need to understand two other fuels since either they, or water, must be introduced into the combustion process or we will be destroying our turbo'd rotary in short order.
Fuel, whether gasoline or some derivative of alcohol (ethanol or methanol), is really about BTUs.
A combo of oxygen and BTUs creates energy as in Torque and HP.
BTUs per Gallon
Gasoline (any octane)..................................116,090
Ethanol (alcohol)......................................... .76,330
Methanol (alcohol)......................................... 57,250
Gasoline wins the energy per gallon contest, so why would we want to run methanol or ethanol?
Alcohol delivers immense cooling compared to gasoline. Cooling is expressed as “latent heat.” The bigger the number the higher the cooling capacity. (BTU/Gal)
Gasoline.......................952
Methanol.....................3136................. ..........3.29 times more cooling than gasoline
Ethanol........................2398............... ............2.52 times more cooling than gasoline
The immense cooling provided by alcohol allows boost to be raised without encountering motor destroying knock. Note that methanol delivers 31% more cooling than ethanol which is why methanol is the non gasoline fuel of choice amongst many pro racers.
Real world proof is provided by Jose LeDuc's 13 B-REW (two rotor) 1000+ rear wheel horsepower drag racing RX3. Powered my methanol alone, the 1150+ flywheel horsepower two rotor doesn’t even use an intercooler! The upper intake manifold is freezing to the touch after a 180+ MPH quarter.
An excellent indicator of rotary health is absence of knock. Low knock equals low CCP Low knock equals less calls to your engine builder. Running about 20% methanol with 93 octane pump gas my 507 SAE hp FD shows less than 10 knock at 20 psi! My motor ran in this state of tune for four years and generated it’s highest compression just as I decided to pull and examine it. (Purely out of curiosity) All was well inside thanks to the methanol.
Rotaries generally fail due to warped apex seals (loss of compression), broken apex seals from knock or blown out coolant seals from too much CCP/heat. Alcohol ‘s ability to defeat heat solves the problems.
Another benefit of alcohol is that it’s autoignition point is much higher than gasoline.
gasoline...........................495 F
methanol..........................867 F
ethanol.............................793 F
Methanol ignites at a 75% higher temperature than gasoline. This delivers important benefits should a piece of carbon decide to glow in the motor.
Our 159 cubic inch 2 rotor motors routinely put out 300, 400, 500 rwhp w the help of turbocharging. Corrected to flywheel hp this is 345, 460, 575 flywheel hp and is 2.16, 2.89, and 3.61 hp per cubic inch! These are all stratospheric compared to the $300,000 AMG hotrodded twin turbo SL65 Benz at 1.81 or the $106,000 Corvette ZR1 at 1.69.
That's why it is necessary to use either water or alcohol derivatives to cool our motors at higher output/boost levels. (please see my thread "the Fix" in the 3rd Gen section for the details.)
Let's get back to the details relative to ethanol and methanol so you can properly size your total fuel needs...
BTU content is the key.
We know what we need as far as gasoline to make "X" hp from above. Since gasoline contains 116,090 BTUs and meth is 57,250 BTUs per gallon, if we are to replace, say 20%, of our gasoline w meth we need to replace it on an equal BTU basis.
Back to the GT35r…
3695 (net of 85% duty cycle) CC/Min Max gasoline is .9761 gallons per minute. (thanks converter site).
.9761 gallons times 116,090 BTUs/Gal = 113,315 BTUs.
Let’s assume we want to take our gasoline injector duty cycle from 85% to 70% using methanol.
That’s a drop of 21.1%. We would be removing 21.1% of the BTUs. .
.211 X 113,315 = 23,996. BTUs removed by cutting base fuel (gasoline.)
To replace those BTUs…
One gallon of methanol has 57,250 BTUs.
23,996/57,250 = 42% of a gallon which is 1586 CC/Min. I run two FJO 700 CC/Min injectors to deliver my meth and am around 76% duty cycle on base fuel w 850/1600 injectors at 11.3 AFR.
As you can see it is a pretty simple procedure to dial in fuel combos. Since the alcohols are “fuel” you can run as much or as little as you wish. I suggest around 1000- 1400 CC/Min.
Finally, there’s water, which can also be an important solution to rotary longevity and increased power.
Water of course is not a fuel, and as such adds no energy.
Water’s big attribute is subtractive! It subtracts/removes heat in a big way.
Heat (BTUs) removed per gallon
Gasoline....................952
Ethanol....................2398
Methanol..................3136
Water.......................8087
Three things jump out.
Water, as far as cooling, is king.
Methanol is king of fuels as far as cooling
Gasoline is lame, very lame. This underlines the inefficiency of purposely tuning to a rich AFR with gasoline. A rich gasoline tune carbons up the motor and adds little cooling-wise compared to water or methanol.
In addition, both methanol and water clean carbon from the rotary interior.
The addition of water is not unlimited since it doesn’t burn. FD tuners generally use between 300 and 500 CC/Min to cool CCP. Should you be wishing to raise boost and make more hp, water in the amount of 700+ CC/Min, has been utilized and 700 rw rotary hp has been made using water and pump gas. An uprated ignition system is required as you start using more than 400 CC.
Howard Coleman
The rotary is, of course, unique and as such it would be a big mistake to use piston metrics when planning setup.
How unique?
Let's talk airflow:
A piston engine can generally make ten hp for every pound per minute of air, so a 70 pound per minute turbo can make 700 piston hp. As we navigate the web looking at turbos we often see a hp tag... for instance a 73 pound per minute TO4Z/GT500/PT67 is often rated at 730 hp. If you are looking for 730 you'd best look elsewhere because they are talking PISTON lingo.
Should you wish to translate to rotary you'd take the pounds per minute, or the estimated HP number, and divide by 1.3.
73 pounds per minute is 561 ROTARY rwhp.
BTW, that doesn't mean the rotary takes a back seat to the piston engine. While it does take a discount due to lower volumetric efficiency (VE), it makes up for lower VE by being able to flow more air V displacement.
O K, let's get into it starting with airflow and hp.
FDs are all about airfow from turbos.
Most turbos have a compressor map which sets forth maximum airflow in pounds per minute and other metrics such as efficiency and airflow at differing boost levels etc. (see Sean's How To Read a Compressor Map thread sticky in the Single Turbo Section).
This thread is about properly sizing the fuel system(s) so let's just focus on the maximum air as set forth on a commonly used GT3582R compressor map.
Airflow is represented in pounds per minute. The GT35 makes approx 62 pounds per minute max.
Rotaries require 1.92 CFM (cubic feet per minute) to make one rear wheel hp. Transposing pounds per minute to CFM, we multiply by 14.471.
14.471 times 62 = 897 cubic feet per minute.
Now that we have CFM we divide by 1.92 to get rear wheel rotary hp.
897/1.92 = 467 max rotary rwhp.
TO4Z, GT500, PT67 turbos make 73 pounds per minute.
73 X 14.471 = 1056 CFM/1.92 = 550 max rotary rwhp
The GT4294 puts out 85 pounds per minute.
85 X 14.471 = 1230 CFM/1.92 = 641 max rotary rwhp
Now that we have an understanding how to get CFM from pounds per minute and then rw rotary hp let's move on to solving for fuel requirements from air generated.
AFR
Air Fuel Ratio... 10 to 1, 11 to 1, 12 to 1. These ratios are for air and fuel measured in POUNDS.
Back to the GT35r and let’s calculate fuel injector sizing.
I suggest we use a couple of "givens."
"Given" we want to have enough fuel to run 10.0 to 1 AFR if necessary.
"Given" we want to run our fuel injectors at no more than 85% capacity (expressed as duty cycle).
Assuming 62 pounds per minute of air, at a 10 to 1 ratio we need 6.2 pounds per minute of gasoline.
62 pounds air
6.2 pounds gasoline
We wish to limit our fuel injectors to 85% duty so we divide 1 by .85
1/.85 = 1.1764
We now take our adjuster (1.1764) and multiply it times our 6.2 pounds per minute of gasoline.
1.1764 X 6.2 = 7.294 pounds per minute of fuel delivery capacity.
The next step is to convert the pounds of gasoline to gallons. Gasoline weighs 6.35 pounds per gallon.
7.294 pounds / 6.35 = 1.14868 gallons per minute
Off to my favorite "converter" website (http://online.unitconverterpro.com/u...ha/volume.html)...
Select “Gallon” converted to “Cubic Centimeter” (CC) and find that 1.14868 gallons is 4348 CC
So 4348 CC/Min at 85% delivery is 3695 CC/Min net of duty cycle.
That number will produce fuel necessary to service the max air GT35r at a 10 to 1 AFR.
Given the above calculations we can now answer some common FD injector questions…
“If I run my 550s as primaries what do I need as secondaries with my GT35?”
4348 - 1100 = 3248 CC/Min needed in addition to 550 primaries
Run a couple of 1600s and you are fine!
“How about 850 primaries and 1300 secondaries?”
4348 required…
(850 X2) = 1700
(1300 X2) = 2600
Total = 4300… fine.
Moving up to the larger 73 pound per minute turbo... Let’s do it simply by just multiplying by the increase in air delivery V the GT35r..
73/62 = 1.1774
4348 X 1.1774 = 5119 CC/Min
“Will 550s work as primaries?”
5119 - 1100 = 4019 required for secondaries so given our assumptions the 1600s won't work.
“What do I need w 850s as primaries?”
5119 - 1700 = 3419 CC/Min. 1600s will probably be O K, especially considering 1600s generally flow 1680 each.
“How about a GT4294 at 83 pounds per minute?”
83/62 = 1.3387
4348 X 1.3387 = 5820 CC/Min
“What do i need in addition to my 850 primaries?”
5820 - 1700 = 4121 CC/Min
As I understand, the Bosch 1600 injector is no longer being made. There are a few new injectors that have become recently available. I believe there is a Siemans injector that is around 2000+ CC/Min and there is at least one brand of aftermarket injectors that offer increased deliverability w good spray pattern.
Additional injector option info welcomed.
So far, we have been talking gasoline.
We also need to understand two other fuels since either they, or water, must be introduced into the combustion process or we will be destroying our turbo'd rotary in short order.
Fuel, whether gasoline or some derivative of alcohol (ethanol or methanol), is really about BTUs.
A combo of oxygen and BTUs creates energy as in Torque and HP.
BTUs per Gallon
Gasoline (any octane)..................................116,090
Ethanol (alcohol)......................................... .76,330
Methanol (alcohol)......................................... 57,250
Gasoline wins the energy per gallon contest, so why would we want to run methanol or ethanol?
Alcohol delivers immense cooling compared to gasoline. Cooling is expressed as “latent heat.” The bigger the number the higher the cooling capacity. (BTU/Gal)
Gasoline.......................952
Methanol.....................3136................. ..........3.29 times more cooling than gasoline
Ethanol........................2398............... ............2.52 times more cooling than gasoline
The immense cooling provided by alcohol allows boost to be raised without encountering motor destroying knock. Note that methanol delivers 31% more cooling than ethanol which is why methanol is the non gasoline fuel of choice amongst many pro racers.
Real world proof is provided by Jose LeDuc's 13 B-REW (two rotor) 1000+ rear wheel horsepower drag racing RX3. Powered my methanol alone, the 1150+ flywheel horsepower two rotor doesn’t even use an intercooler! The upper intake manifold is freezing to the touch after a 180+ MPH quarter.
An excellent indicator of rotary health is absence of knock. Low knock equals low CCP Low knock equals less calls to your engine builder. Running about 20% methanol with 93 octane pump gas my 507 SAE hp FD shows less than 10 knock at 20 psi! My motor ran in this state of tune for four years and generated it’s highest compression just as I decided to pull and examine it. (Purely out of curiosity) All was well inside thanks to the methanol.
Rotaries generally fail due to warped apex seals (loss of compression), broken apex seals from knock or blown out coolant seals from too much CCP/heat. Alcohol ‘s ability to defeat heat solves the problems.
Another benefit of alcohol is that it’s autoignition point is much higher than gasoline.
gasoline...........................495 F
methanol..........................867 F
ethanol.............................793 F
Methanol ignites at a 75% higher temperature than gasoline. This delivers important benefits should a piece of carbon decide to glow in the motor.
Our 159 cubic inch 2 rotor motors routinely put out 300, 400, 500 rwhp w the help of turbocharging. Corrected to flywheel hp this is 345, 460, 575 flywheel hp and is 2.16, 2.89, and 3.61 hp per cubic inch! These are all stratospheric compared to the $300,000 AMG hotrodded twin turbo SL65 Benz at 1.81 or the $106,000 Corvette ZR1 at 1.69.
That's why it is necessary to use either water or alcohol derivatives to cool our motors at higher output/boost levels. (please see my thread "the Fix" in the 3rd Gen section for the details.)
Let's get back to the details relative to ethanol and methanol so you can properly size your total fuel needs...
BTU content is the key.
We know what we need as far as gasoline to make "X" hp from above. Since gasoline contains 116,090 BTUs and meth is 57,250 BTUs per gallon, if we are to replace, say 20%, of our gasoline w meth we need to replace it on an equal BTU basis.
Back to the GT35r…
3695 (net of 85% duty cycle) CC/Min Max gasoline is .9761 gallons per minute. (thanks converter site).
.9761 gallons times 116,090 BTUs/Gal = 113,315 BTUs.
Let’s assume we want to take our gasoline injector duty cycle from 85% to 70% using methanol.
That’s a drop of 21.1%. We would be removing 21.1% of the BTUs. .
.211 X 113,315 = 23,996. BTUs removed by cutting base fuel (gasoline.)
To replace those BTUs…
One gallon of methanol has 57,250 BTUs.
23,996/57,250 = 42% of a gallon which is 1586 CC/Min. I run two FJO 700 CC/Min injectors to deliver my meth and am around 76% duty cycle on base fuel w 850/1600 injectors at 11.3 AFR.
As you can see it is a pretty simple procedure to dial in fuel combos. Since the alcohols are “fuel” you can run as much or as little as you wish. I suggest around 1000- 1400 CC/Min.
Finally, there’s water, which can also be an important solution to rotary longevity and increased power.
Water of course is not a fuel, and as such adds no energy.
Water’s big attribute is subtractive! It subtracts/removes heat in a big way.
Heat (BTUs) removed per gallon
Gasoline....................952
Ethanol....................2398
Methanol..................3136
Water.......................8087
Three things jump out.
Water, as far as cooling, is king.
Methanol is king of fuels as far as cooling
Gasoline is lame, very lame. This underlines the inefficiency of purposely tuning to a rich AFR with gasoline. A rich gasoline tune carbons up the motor and adds little cooling-wise compared to water or methanol.
In addition, both methanol and water clean carbon from the rotary interior.
The addition of water is not unlimited since it doesn’t burn. FD tuners generally use between 300 and 500 CC/Min to cool CCP. Should you be wishing to raise boost and make more hp, water in the amount of 700+ CC/Min, has been utilized and 700 rw rotary hp has been made using water and pump gas. An uprated ignition system is required as you start using more than 400 CC.
Howard Coleman
Last edited by KKMpunkrock2011; 04-16-10 at 09:51 PM. Reason: make it shorter
04-17-10 | 10:28 AM
#6
just about any top feed rail will work with those top feed injectors, why don't you just go big and get 1680s and a top feed rail? Doing a top feed rail in the secondary location is an absolute bitch with the LIM still on the motor, I just finished doing mine, not fun.
what exactly are you goals? I keep howards post's handy for figuring stuff like fuel needs out
what exactly are you goals? I keep howards post's handy for figuring stuff like fuel needs out
Just out of curiosity though, why is it hard to install a top feed rail with the LIM still in the car? Seems pretty straight forward to me.
04-19-10 | 02:50 AM
#7
it's a bit of a tight fit in there, I ended up getting shorter bolts and a swivel socket and it made it 10x easier, also the fitting that is on the secondary rail where the hose from the primary rail attaches is a tight fit by the water temp sensor, but I did have to use a reducer which extended that particular fitting another half inch +. I'll try and take a pic this week sometime.
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04-19-10 | 11:47 PM
#8
i would remove all emissions , simplify vacuum lines and solenoids...to make some room
you will need LMI spacers and they need to be pressed in...there is another option CJ-Motorsports LMI spacers they have rubber o-ring for a positive seal....
http://www.cj-motorsports.com/catrx7injadp.htm
if you go with low impedance injector like the ones you have you will need injector driver or resistors...
for secondary injectors i would recommend
Injector Dynamics 2200cc high impedance injector...you will not need injector driver or resistors and they come static flow matched they also make 1000cc injectors if you wanna run 4x1000cc...
http://www.t1racedevelopment.com
04-20-10 | 01:24 AM
#9
those 2200 injectors would be awesome, I wish I had seen them before I payed for my 1600's and resistors.
in regards to the LIM spacers, you can use the rubber/plastic diffuser things if you clip the prongs and sand them down smooth, at least that's what I did. It is sufficient until I remove the LIM to have the spacers pressed in.
Thursday night I'll get that picture for ya if I remember.
in regards to the LIM spacers, you can use the rubber/plastic diffuser things if you clip the prongs and sand them down smooth, at least that's what I did. It is sufficient until I remove the LIM to have the spacers pressed in.
Thursday night I'll get that picture for ya if I remember.
04-24-10 | 12:04 PM
#10
those 2200 injectors would be awesome, I wish I had seen them before I payed for my 1600's and resistors.
in regards to the LIM spacers, you can use the rubber/plastic diffuser things if you clip the prongs and sand them down smooth, at least that's what I did. It is sufficient until I remove the LIM to have the spacers pressed in.
Thursday night I'll get that picture for ya if I remember.
in regards to the LIM spacers, you can use the rubber/plastic diffuser things if you clip the prongs and sand them down smooth, at least that's what I did. It is sufficient until I remove the LIM to have the spacers pressed in.
Thursday night I'll get that picture for ya if I remember.
04-24-10 | 03:54 PM
#12
Sorry to hear that. Yea I forgot the stock FPR is on the secondary rail and you can't reuse it.
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