What do most you guys have your onset PSI at? I have mine at 70psi and im barely hitting 11.7afr at WOT. Also have the bleeder valve screwed all the way in; highest rate of gain.
Also, running about 8-9 psi of boost.
"You can only feed them semen for so long before their legs fall off."
the begi goes up to 12:1 ratio if not mistaken,so @8psi you should be reading 12 x 8=96psi,unless something is wrong with diaphram inside.
Given the calculations per BEGI worksheet and others for adding fuel (based on an assumed boost pressure ratio and proper boost reference signal you are supplying) - your fuel pressure may need to be as high as 112~120 psi at maximum boost if you're still running a stock base pressure. But if you're running those 36 lb injectors I assume you have tweaked your base pressure to improve the idle and offboost mixture unless you are using HP tuners.
http://www.bellengineering.net/templates/BEGi/images/Manuals/FMU_Instructions.pdf
But this doesn't necessarily answer your question about "onset" - I thought the BEGI site said onset could be anywhere from 50-80 as there is no "magic number" as each engine and fuel system is different.
Are you running anything other than the the stock FPR?
I thought it was an 8:1 ratio...huh.. Also, that's after hitting boost and leaving vacuum. There's no stock FPR in my system, only the BEGI. I have the base pressure set at 70 with the rising rate as high as it can go. Im wondering if there's something wrong with it or I just need to up the base pressure a little more.
Also, at idle the AFR's are usually always the same no matter what pressure.
"You can only feed them semen for so long before their legs fall off."
70psi!!!! are you crazy? injectors begin to fail at that pressure. you need to scrap that rising ratio fmu crap and install a 1:1 fuel pressure regulator with custom tune. off boost your engine ecu is trying its hardest to keep your afr at 14.7 so your fuel trim is probably ridiculous. at that pressure theres not a lot of flow. your fuel pump is probably hurting.
At idel it says my fuel pressure is 20psi. When I unhook the signal line the gauge jumps to 70 psi which is what I have it set at. Re-attach the signal line and it goes back to 20psi. Im going to buy another fuel pressure gauge (electronic most likely) just to double check. BUT if it's 6:1 or 8:1, whatever it is, that means im hitting between 124psi-140psi at WOT at 9psi of boost. WTF mates????haha!
"You can only feed them semen for so long before their legs fall off."
JOE L wrote:70psi!!!! are you crazy? injectors begin to fail at that pressure. you need to scrap that rising ratio fmu crap and install a 1:1 fuel pressure regulator with custom tune. off boost your engine ecu is trying its hardest to keep your afr at 14.7 so your fuel trim is probably ridiculous. at that pressure theres not a lot of flow. your fuel pump is probably hurting.
Nonsense! If injectors failed at 70 psi a lot of boosted cars would not be running. Increasing pressure does increase flow - and yes there is a limit based on the current drivers,duty cycle, and fuel pump. Talk to Bill Hahn - he'll explain away for you. Or talk to QWK LN2 (aka ImPhat0260), or John Benham. Also look for this thread for other examples:Hahn Stage II - Idle AFR's ??? - Tuning Forum
Also this guy is running a drop-in Racetronix - so his pump is fine (or hope so - it was on his future list).
But I agree - as a base fuel pressure 70 is too high for your set-up.
If you're keep the rising rate-begi fpr with little/no tune on your car I suggest putting the stock FPR or an adjustable back on it - the BEGI is designed to work with a stock FPR so that it only raises pressure at the onset of boost. With those injectors and an adjustable FPR it could be set at 28~35 psi base pressure and likely have enough fuel off boost. Or you can use HP tuners to modify your injector constant and keep your stock base pressure and skip the adjustable FPR.
Now - on boost the BEGI will bump up the pressure as needed - and as reminder the BEGI goes between the Stock FPR and the tank return line. Or HP tuners with closed loop PE modifications can supplement the on-boost fueling strategy and refine the AFR's.
Edited 3 time(s). Last edited Tuesday, February 16, 2010 11:36 AM
Dont have the racetronix in yet...actually just opened the UPS box with it in it!
"You can only feed them semen for so long before their legs fall off."
once a specific fuel pressure is reached the injectors get held open and or need more amperage to open because of the extra force of the fuel pressure. this causes injector damage. not to mention, 70+ psi fuel pressure is not safe. raising the fuel pressure at a ridiculous rate compared to boost is a cheap way of boosting a vehicle but its not the right way. an fmu only creates an ideal afr at a specific rpm and the rest of the rpm the afr is incorrect. theres more to boost than afr so i would scrap the fmu and get a custom tune. the higher the pressure the less flow you have unless the proper fuel pump has been installed to work with those high pressures. the stock fuel pump is definitely not going to be able to survive that kind of pressure.
I'm definitely an advocate of Hp tuners and using less fuel pressure but Hahn has been using RRFPR's or (FMU) for a long time. And you can search all of this forum and find that the early days of boost always used that method of adding fuel. Now that we have HP tuners and other methods to drive larger injectors and tune fuel maps that is certainly a cleaner way to do it. But i'm not going to knock a guy for using the old method if it works.
Safety is achieved through proper pumps and OE fittings or AN style and high pressure hoses - never use low rated hoses or clamps. The FMU is boost referenced adding pressure as the boost rises with rpm, so I don't see how it can be completely "not ideal" throughout the rpm band. I don't have logs to prove it but I'm sure someone does. So with that said - I advocate a good tune but i don't knock the FMU.
i have to agree with joe l at roughly 65 psi the injectors start to "clip" i think is the term because the pressure is to great for them to work properly . if you really want it to run right get bigger injectors and get it tuned . i also like he said invest in a good 1:1 ratio fpr boost dependant areomotive sells a nice one for about 135.00 well worth it compared to a replacing the motor when it runs lean and pops . fmu's are a cheap quick way to raise your fuel pressure not allways the correct way . i'm also sure the guys at hahns did alot of tunning trials to make it work for them before they put it out there .
if you arent spraying your just playing !!!
slowfire99 wrote:i have to agree with joe l at roughly 65 psi the injectors start to "clip" i think is the term because the pressure is to great for them to work properly . if you really want it to run right get bigger injectors and get it tuned . i also like he said invest in a good 1:1 ratio fpr boost dependant areomotive sells a nice one for about 135.00 well worth it compared to a replacing the motor when it runs lean and pops . fmu's are a cheap quick way to raise your fuel pressure not allways the correct way . i'm also sure the guys at hahns did alot of tunning trials to make it work for them before they put it out there .
Not so. Our stock FPR is 1:1. With a supercharger you will see 65psi, and they do not clip.
FU Tuning
If one was to use a 1:1 FPR as suggested earlier in this post and tune with HPT as suggested earlier in this post results will look something like this: WOT fuel presure is around 50psi, and you are runing 9psi of boost, that would give you 59psi of fuel pressure. I'm running this now no issues. Others have ran this and more no issues. My 96 has a fuel pressure gaug inside the car. I could see 100psi and then the fuel pump would cut out. Usually with a FMU you are running higher than 1:1, like 6:1, or 8:1, or 10:1, or even 12:1, so you are going to see higher than that. I would be more worried about the fuel pump not keeping up.
FU Tuning
a 1:1 fuel pressure regulator is not an add on like an fmu. it replaces the original fuel pressure regulator. so the static fuel pressure is set at ~36-42 psi so at 9 psi boost the fuel pressure will be 45-51psi.
read this it starts out about injectors but a few paragrapghs down it explaines diff senarios w/fmu and why they're misunderstood.yes you need to have a fuel pump for f/i and fmu.youcan get away with smaller injectors by using fmu as it increases flow up to 40%from original stated flow rate.80-85psi seems to be the limit before clipping as alot of research i've done that's what's said.if idle press is 40psi and you go to 80psi ,your boost is 8psi,minus 40 from 80=40divide by boost[=5:1ratio . i may be wrong here but that's what it seems.
http://www.superstallions.com/tech/eng/inject/injector.html
JOE L wrote:a 1:1 fuel pressure regulator is not an add on like an fmu. it replaces the original fuel pressure regulator. so the static fuel pressure is set at ~36-42 psi so at 9 psi boost the fuel pressure will be 45-51psi.
Jbody's stock have a 1:1 FPR.
FU Tuning
Senorguitar wrote:At idel it says my fuel pressure is 20psi. When I unhook the signal line the gauge jumps to 70 psi which is what I have it set at. Re-attach the signal line and it goes back to 20psi. Im going to buy another fuel pressure gauge (electronic most likely) just to double check. BUT if it's 6:1 or 8:1, whatever it is, that means im hitting between 124psi-140psi at WOT at 9psi of boost. WTF mates????haha!
.... 70psi (at atmospheric or 0 gage pressure), and 20psi at full vacuum which is (~30 in-Hg or -14.7psi)
.....some math: (70-20)/(14.7)= 3.4 ratio of gain. But this is from vacuum to 0 gage pressure - technically the begi only works from 0 gage pressure and up, unless you have a fancy all-in-one unit.
If your onset pressure is 70 and you're running 9psi of boost, below is your theoretical max pressure achieved:
70+(9*3.4) = 100.6 psi --> since the Begi should only be working from 0 gage and above. Your ratio could be much higher than 3.4 ratio of gain. You'll need to log or check your pressure at say 3 lbs of boost to get an idea of the on-boost rate of gain and do this calc: (new fuel pressure at 3 lbs boost - minus onset pressure) / divided by the 3 lbs = ratio.
As mentioned, for a
guy with no tune it may be 10~20 psi low to get the
fuel flow you need based on the boost you're running. Since the injectors and drivers don't do so well above 100psi, I suggest an alternate method like a tune and using your stock FPR in series like it's supposed to be run with...
Below is some more rambling but giving it some time to sink it in I think I'm not far off base at all.
BTW - At 20psi fuel pressure you're creating fuel droplets not fuel spray. I read somewhere you want at least 2 Bar or 29psi.
One more thought - you essentially have injectors that are almost twice as large as stock and you're running that FMU and no tune on the car - I think your stock pump is acting deficient for the boost level given the pressure and flow your FMU should be supplying, and it not being extremely rich.
With your 36lb injectors, if you were running a stock base pressure of 43psi, those injectors would only need the 1:1 ratio to supply enough fuel for 250HP. But you dropped your stock 1:1 FPR and so your base pressure dropped to 20psi due to the flow area increase. So your car may be over rich and down on fuel economy and you don't have the fuel control off-boost and your onset is completely controlled by the BEGI. You get no stepped increase in pressure as you would have with your stock FPR in series with the BEGI FMU. This fueling situation need some refinement.
Two ideas:
1. Get an adjustable 1:1 FPR that fits in the stock location, reduce fuel pressure to 29psi, keep the rrfpr BEGI for the on boost.
2. Get a tune for your larger injectors, and put the stock regulator back on and chuck the rrfpr BEGI.
Edited 1 time(s). Last edited Thursday, February 18, 2010 6:56 AM
Well, i installed the fuel pump yesterday, turned on my car and i was running wicked lean! Would push the gas and it would kill the engine. SO, dropped the tank again today, re-did the install, and it works. Idle fuel PSI is up, and the onset psi is lower and running rich... So yes, my stock fuel pump couldnt keep up with the demands of the turbo.
I also have the harness from racetronix, but im going to put that on once I start hitting higher horsepower numbers. Also planning on doing the cut out in the floor for easy access.
Thanks for all the tips and advice guys!
"You can only feed them semen for so long before their legs fall off."
Too Whiney wrote:JOE L wrote:a 1:1 fuel pressure regulator is not an add on like an fmu. it replaces the original fuel pressure regulator. so the static fuel pressure is set at ~36-42 psi so at 9 psi boost the fuel pressure will be 45-51psi.
Jbody's stock have a 1:1 FPR.
uhm nooooo!!!!!!!!!!
why would a non boosted vehicle have a 1:1 boost reference fpr???????????
dont confuse a vacuum fpr to a 1:1 boost reference fpr.
stock vacuum fuel pressure regulator works from ~40 inhg to 0 inhg (vacuum). when the engine is idling the vacuum is high so the fuel pressure goes down. when you stomp on the throttle vacuum is lost and fuel pressure goes up a bit. add boost to a stock fpr and it doesnt raise the fuel pressure anymore past the 0 inhg mark .
on a 1:1 boost reference fuel pressure regulator you set the base pressure (usually same pressure the stock fpr idles at. ~36-42 psi) the engine runs off the base fuel pressure until boost is seen. when the 1:1 fpr sees boost it will raise the fuel pressure 1 psi for every 1 psi boost. this setup gives you a quick rich condition and makes tuning a bit easier.
Senorguitar wrote:Well, i installed the fuel pump yesterday, turned on my car and i was running wicked lean! Would push the gas and it would kill the engine. SO, dropped the tank again today, re-did the install, and it works. Idle fuel PSI is up, and the onset psi is lower and running rich... So yes, my stock fuel pump couldnt keep up with the demands of the turbo.
I also have the harness from racetronix, but im going to put that on once I start hitting higher horsepower numbers. Also planning on doing the cut out in the floor for easy access.
Thanks for all the tips and advice guys!
As mentioned above - now you're wicked rich with the new pump as expected so go with Option 1 above for your least expense - you will need the adjustable 1:1 stock type vacuum operated regulator if you don't get your injector constant tuned for your 36lb injectors.
As you progress with your tune get someone with HP-tuners to help you and move to Option 2 or a combination if necessary that way you can get more out of car like like timing control, fuel refinement, etc.
Its not too bad. I just need to tune the begi a little more...and get a nice electronic gauge that I can place in the car. But I plan on getting the tune once I purchase the larger turbo, which im hoping will be in the next couple months. Looking at a T3/T4E
"You can only feed them semen for so long before their legs fall off."
If you're adding 9 lbs of boost on an otherwise stock internal set-up and running a bit rich that is just fine in my opinion. I don't know what others think but conservatively speaking I would not go much higher unless you build up the motor. If you invest in a tune the car will respond better, run better and put down more power. Good gages and correct positioning of the sensors are paramount. You will be happy with your results so get a dyno session and find out where you are some time.
I think at this point you have some decent reliability..if you go larger on the turbo you will sacrifice some low end response, but gain power at the top end. This where you need to think about the streetability, your goals, and how deep your pockets may be as increases would require another injector change, turbo change, internals etc.
Great job on your build and success..happy boosting.
I would run 17psi on a stock motor wiht no problems.
FU Tuning
Too Whiney wrote:I would run 17psi on a stock motor wiht no problems.
That sounds agressive on a stock internals, but sweet if it can be reliable. So what do you think I can run with my set-up? I was planning 13 psi to start.
Yeah, look at Hypsy...he ran big numbers on stock internals...but he's also slightly crazy.
Going to the dyno in the next month with the car club here so that's good. Also, putting a .63 a/r turbine on so the power band will be shifted into the higher rpm range. Mainly making this a drag car, hopefully. But for now it's my DD.
"You can only feed them semen for so long before their legs fall off."
