which pump to run with 20 psi on t61?
09-02-11 | 07:18 PM
#26
Racing Rotary Since 1983
iTrader: (6)
Joined: Oct 2001
Posts: 6,136
Likes: 563
From: Florence, Alabama
"what would the resulting BSFC @ peak power be using petrol only?"
looking at the data from my run (post 24)
506.83 call it 507 SAE
507 X 1.92 = 973 CFM
973/14.471 = 67.26 pounds of air per minute
12.0 AFR so 67.26/12 = 5.605 pounds of fuel per minute
5.605 pounds per minute X 60 = 336.34 pounds per hour
336.04/507 hp = 66.3 BSFC
this number is based on the actual fuel delivered as opposed to the indicated duty cycle calculation.
i note that RC Eng simply uses duty cycle times injector capacity to figure BSFC. they don't take into consideration the lag haircut.
as to lag resulting in a 30% deduct in net fuel delivered all i can tell you is that was the case in my run posted above.
lag may differ depending on injector type, pressure, voltage, and many other factors. others more knowledgable than me, and there are many, pls feel free to enlighten..
looking at the data from my run (post 24)
506.83 call it 507 SAE
507 X 1.92 = 973 CFM
973/14.471 = 67.26 pounds of air per minute
12.0 AFR so 67.26/12 = 5.605 pounds of fuel per minute
5.605 pounds per minute X 60 = 336.34 pounds per hour
336.04/507 hp = 66.3 BSFC
this number is based on the actual fuel delivered as opposed to the indicated duty cycle calculation.
i note that RC Eng simply uses duty cycle times injector capacity to figure BSFC. they don't take into consideration the lag haircut.
as to lag resulting in a 30% deduct in net fuel delivered all i can tell you is that was the case in my run posted above.
lag may differ depending on injector type, pressure, voltage, and many other factors. others more knowledgable than me, and there are many, pls feel free to enlighten..
09-02-11 | 07:22 PM
#27
Rotary Freak
Joined: Dec 2001
Posts: 2,402
Likes: 0
From: chandler, AZ
i do agree with you re dead time and flow.
given the fact i have not taken that (as it turns out important) fact under consideration i thought i would visit one of my logs and do the calculations.
i am working on a log where i made 506.83 SAE hp at 7296 RPM at 75.1 duty cycle.
12.0 AFR
506.83 X 1.92 is 973 CFM is 67.24 pounds of air per minute.
at 12 AFR that is 5.603 pounds of gas per minute
5.603 pounds is .882 gallons per minute.
.882 X 116,090 = 102,448 BTUs to make 506 rotary at 12 AFR
i was injecting 1419 CC/Min of meth or .374 gallons per minute
.373 GPM X 57,250 = 21,411 BTUs from meth
102,448 - 21,411 from meth = 81,037 needed from gas.
according to my logged duty cycle (75.1) and my injectors
call them 880 & 1650 X 2 i can make 5060 nominal.
5060 X .751 = 3800 CC/min
3800 = 1.003 GPM or 116,438 BTUs
but i actually was using 81,037 BTUs
therefore in this case deadtime/lag decreased net delivery by 35,401 CC/Min or 30%
At that particular RPM
i imagine lag varies a bit between injector designs which have greatly improved over the years. further, since part of dead time is probably a constant due to it being mechanical in nature, lag probably decreases w ontime. ( less than a Ms at low load/rpm and 20 Ms higher up the load rpm range.)
With injector models and designs aside, lag varies with voltage and differential fuel pressure. That's what our alternators and fuel pressure regulators are for.
Ontime doesn't effect lag, but lag effects duty cycle and overall fuel flow potential depending on RPM. Lets look at your low load vs. high load comparison. At low load the cycle time is very large and pulsewidths are small. Lets say you need 2ms worth of fuel flow at idle for a particular injector that has a 1ms lag time. The ecu needs to open the injector for 3msec and that lag time accounts for 33% of ontime while increasing the duty cycle only very little. At high load, we have much shorter cycle times (10msec @6000 rpm for example) and the same 1msec lag takes up a bigger portion of duty cycle, 10% of fuel flow potential.
Your injector supplier should be able to give you this data so that your calculations can be as accurate as possible.
the above run was in 09 running obsolete V the newer EV14 injectors. i ran an FJO Peak and hold converter on the secondaries.
anyway, bottom line is it appears you are quite correct as to including deadtime and it is consequential.
i am quite certain it decreased gross delivery by 30% and as such that needs to be cranked in to the calculations.
my error.
it will be interesting to see where i end up on the dyno shortly. i may need a bit more capacity.
howard
given the fact i have not taken that (as it turns out important) fact under consideration i thought i would visit one of my logs and do the calculations.
i am working on a log where i made 506.83 SAE hp at 7296 RPM at 75.1 duty cycle.
12.0 AFR
506.83 X 1.92 is 973 CFM is 67.24 pounds of air per minute.
at 12 AFR that is 5.603 pounds of gas per minute
5.603 pounds is .882 gallons per minute.
.882 X 116,090 = 102,448 BTUs to make 506 rotary at 12 AFR
i was injecting 1419 CC/Min of meth or .374 gallons per minute
.373 GPM X 57,250 = 21,411 BTUs from meth
102,448 - 21,411 from meth = 81,037 needed from gas.
according to my logged duty cycle (75.1) and my injectors
call them 880 & 1650 X 2 i can make 5060 nominal.
5060 X .751 = 3800 CC/min
3800 = 1.003 GPM or 116,438 BTUs
but i actually was using 81,037 BTUs
therefore in this case deadtime/lag decreased net delivery by 35,401 CC/Min or 30%
At that particular RPM
i imagine lag varies a bit between injector designs which have greatly improved over the years. further, since part of dead time is probably a constant due to it being mechanical in nature, lag probably decreases w ontime. ( less than a Ms at low load/rpm and 20 Ms higher up the load rpm range.)
With injector models and designs aside, lag varies with voltage and differential fuel pressure. That's what our alternators and fuel pressure regulators are for.
Ontime doesn't effect lag, but lag effects duty cycle and overall fuel flow potential depending on RPM. Lets look at your low load vs. high load comparison. At low load the cycle time is very large and pulsewidths are small. Lets say you need 2ms worth of fuel flow at idle for a particular injector that has a 1ms lag time. The ecu needs to open the injector for 3msec and that lag time accounts for 33% of ontime while increasing the duty cycle only very little. At high load, we have much shorter cycle times (10msec @6000 rpm for example) and the same 1msec lag takes up a bigger portion of duty cycle, 10% of fuel flow potential.
Your injector supplier should be able to give you this data so that your calculations can be as accurate as possible.
the above run was in 09 running obsolete V the newer EV14 injectors. i ran an FJO Peak and hold converter on the secondaries.
anyway, bottom line is it appears you are quite correct as to including deadtime and it is consequential.
i am quite certain it decreased gross delivery by 30% and as such that needs to be cranked in to the calculations.
my error.
it will be interesting to see where i end up on the dyno shortly. i may need a bit more capacity.
howard
Good luck on the dyno.
And back to topic: I would go with a single walbro feeding a surge tank with a Bosch 044 taking care of the high pressure side.
09-07-11 | 05:14 PM
#30
wat hp setup do u have ball joint?
i thought i read somewhere that those aermotive pumps were giving problems?
think kris johnson posted it on his facebook
"Sixth car in a row running on one of these new 340lph in-tank fuel pumps dropping pressure as the fuel heats up. Decided to do a simple test tonight. Left car idling for like 30 mins and sure bet base pressure went from 40 to 25psi! It never fails. I have yet to see one application not experiencing this problem.
So far this is only happening on one particular brand. Care to guess? LOL!"
and
" Last week on another application it started happening after about 10 dyno runs where the pressure would start to drop at high rpms. Let the car sit for 20 mins and problem went away. Once they a replaced with walbros the problem went away."
i thought i read somewhere that those aermotive pumps were giving problems?
think kris johnson posted it on his facebook
"Sixth car in a row running on one of these new 340lph in-tank fuel pumps dropping pressure as the fuel heats up. Decided to do a simple test tonight. Left car idling for like 30 mins and sure bet base pressure went from 40 to 25psi! It never fails. I have yet to see one application not experiencing this problem.
So far this is only happening on one particular brand. Care to guess? LOL!"
and
" Last week on another application it started happening after about 10 dyno runs where the pressure would start to drop at high rpms. Let the car sit for 20 mins and problem went away. Once they a replaced with walbros the problem went away."
Even after numerous runs and heavy driving the fuel pressure has stayed solid. What kind of cars/setups has your friend tested these pumps on?
09-18-11 | 06:57 AM
#31
I have the most recent rx7.com denso pump. Ran 17 psi and made 425 on 93 octane (35r) . It was solid. I am now going to run 20psi on 93 w/ an aquamist 2D system. Probably going to install a ken belle boost a pump to be safe. I am running 550/1600 for fuel. The higher injector cycles will help my injection system as it sprays accordingly to the % of injector output. Hoping for 450 @ 20psi. G
09-18-11 | 09:51 AM
#32
There is a BMW shop that also sells a kit but you dont need the whole kit and last I checked with him he wont sell just the one fitting, I have it pictured below.
if you are going to run new fuel hose with AN fittings then the 044 usually comes with the adapters you need
That is my pump set up in my FC, if I were to change turbo I would just build my fuel system from the pump to the engine compartment which is the last of the stock system left.
03-12-12 | 06:09 PM
#34
FWIW, i have run a Denso and made 507 w zero pressure fall off at 20 psi w the aid of a Kenne Bell Boost A Pump set at a 20% Volt gain. i have run this setup since 1999 and am still using the same pump. Voltage is key to output. the study does not disclose the V. all of the above pumps will output more w higher V.
do remember that the rotary requires approx 30% more air and fuel V a piston engine so don't use piston hp numbers unless you make the correction.
howard
eventually i couldn't compensate with maps and we noted the pressure was dropping to 25psi after 15psi of boost. the fuel pump wasn't just running out of steam, it was progressively dying. this is NOT a good attribute for a pump when it is failing.
it only took that one time for me to try and steer away from the supraTT denso pump. we dropped a walbro 400lph into it and finished up the tune without any further issues. the KB was still pushing 17+volts so it wasn't a matter of the boost a pump failing either.
wasn't but a few years ago the denso pumps changed, i assume the quality also took a nosedive when pushing them to their limits. i never used to have any problem with them and this was not a knockoff pump. could be the pump windings on the new style pumps do not much like the voltage bump and it cooks them inside out. the pump also began getting quieter, it was a strange death.
the kenne belle was also pulling alot of amperage with the supra pump, i had to add a second 40a relay to push enough juice to it to keep from cooking the single relay, unfortunately the pump did not wake up after fixing the relay still.
Last edited by RotaryEvolution; 03-12-12 at 06:16 PM.
03-12-12 | 11:30 PM
#36
Could go with http://www.turblown.net/store/index.php?productID=69 thats the pump I am going with to get over 500 with.
03-13-12 | 01:12 AM
#37
My future setup will be capable (hopefully) of 550whp, will the Walbro 400 be enough without the KB BAP?
03-13-12 | 11:17 AM
#38
after testing we figured the pump was the culprit after checking everything else out in the fuel system and it all checked out ok. it was late and the walbro was the only thing any shop that was still open carried locally and the car was still on the dyno, the dyno shop also is only open late, the car made 450whp on the old walbro 255lph pump pushing ~17volts with the KB for years so it was proven to do the job with the kenne belle.
when we switched to the walbro 400lph i turned the kenne belle down to static, so it was basically turned off. the walbro did perfectly fine pushing battery voltage at the same ~500whp level. even though the injectors and 35R were basically maxed out, at least the fuel pump now has room to grow versus being pushed to it's limit as the supra pump was.
when we switched to the walbro 400lph i turned the kenne belle down to static, so it was basically turned off. the walbro did perfectly fine pushing battery voltage at the same ~500whp level. even though the injectors and 35R were basically maxed out, at least the fuel pump now has room to grow versus being pushed to it's limit as the supra pump was.
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