greyzone

Heres the deal:

I just put in a Walbro 255lph HI FLOW in tank....and the fuel pressure is off the map, I mean its reading like 120psi (the gauge is stopping at max read i think)

Old pump was a Holly 255 (not hi flow) and at WOT at 10PSI of turbo boost the gauge read FP 90psi max.

QUESTION: Other than running rich, could this kind of pressure be bad for anything??

Im running stock injectors. Vortech 10:1 FMU.

Car dynoed at 200whp with 10psi and 90psi fuel pressure running a/f ratios in the 12's with the Holly pump. Pump started giving out so I replaced it with the Walbro HI FLOW, man this thing kicks serious ***, but now Im wondering if its TOO MUCH pressure.

Thinking I should probably change the FMU to an 8:1 or possibly even a 6:1...

All thoughtful, experienced opinions appreaciated.

Thanks



[Modified by greyzone, 9:25 PM 11/11/2002]

b16ahybrid

the high pressure fuel pump raised you idle fuel pressure so your fuel pressure is higher all the way to redline.
With the old pump your base pressure (idle) was probably cose to 38psi, once you put the new pump in it raised it to close to 55psi (at least that happend with mine).i have heard from a lot of people who experienced the same problem, the fix is an aem adjustable fpr with the largest orface installed...

btw 90psi of fuel pressure at 10psi doesn't sound rite....figure your fuel pressure is getting bumped up 100psi under full boost.....doesn't make sense....I know with my 6:1 and 8psi i'm at about 100psi under full boost

greyzone

My idle fuel pressure has stayed the same...right at 40-42psi with both pumps...its the hi end that really has taken off.

Still wondering tho, CAN THIS HI PRESSURE DAMAGE ANYTHING??

The Holly was not the HI FLOW, so, even tho it was a 255 it was still maxing out and not holding up the top end real well. Still, at only 80-90psi at 10 lbs boost I wonder if it was kizmo from the start, but I did run it for about 30,000 miles without problems....just 90psi, which was really that pumps max capacity.

I have known for a long time that what I really needed was the HI FLOW, but damn...what a difference!!

b16ahybrid

you mentioned that the holley pump maxed out at 90psi which is probably it's limit, since you switched to the high pressure it will raise the fuel pressure past 90psi (mine does).I have had mine up to 120+psi...
So here is whats happening....the holley maxes out at 90psi the fmu tries to raise the pressure higher but the pump won't keep up.so in reality the fmu would still raise the fuel pressure to 120psi (more like 140psi under boost) if the pump kept up.Then you installed the high pressure pump and it will raise the pressure past 90psi on up to where the fmu wants it...thats why you were leaning out in the top end before because your fuel pressure was to low under full boost.

Calculated out your fuel pressure under full boost with your set up should be as follows....
40psi+ 10psi+100psi = 150psi under full boost....
40psi is the base fuel pressure, 10psi is what the stock fpr raises the fuel pressure under full throttle,then 100psi for the fmu (10:1 x's 10psi)..
is this making sense?
you really need larger injectors if you want to run 10psi safely.Stock injectors max out at about 75psi then the flow pattern goes to ****.i wouldn't recomend going past 5psi with stock injectors.What you need is a set of 440cc (or larger) injectors and a 4:1 fmu (if you stick with the fmu)...

I'm maxing out my 310cc injectors with 8psi and 6:1 fmu....

hope this helps..............

b16ahybrid

oh and to answer your question yes that much fuel pressure can damage stuff.A friend of mine was runing a 10:1 fmu with stock injectors at 7psi until his injector got stuck open, wasn't a very pleasing mess...I wouldn't recomend runing more then 100psi on any injectors....(according to rc engineering)

greyzone

So I should put a 6:1 disk in the FMU, which should get me to 100psi under full boost at 10psi?

I think that would be right...40 base, plus 60 (10x6) = 100...

then for my low boost setting, at 7psi, I'd be at about 82psi....

sound right??

Plus, that should still allow me to run a/f in the 12's

b16ahybrid

Yeah but you will need larger injectors to do that.With stock injectors you cant go lower then a 10:1 fmu.
Stock injectors are only 240cc the largest that you can go with a stock ecu while still maintaining a decent idle is 310cc.
If you tried to run 6:1 with stock injectors you would lean out...

greyzone

That doesnt make sense...at 10psi with a 6:1 I should still be at 100psi at WOT, why would I lean out at 100psi?? Before at 90 psi I was in the 12's with my a/f all the way up to redline, with stock injectors also.

When the HOlly started taking a dive, and went down to 75-78psi at WOT I started minor pinging cause I was running lean at WOT, but at 90psi it was fine, so I would think that at 100psi it would be fine also.

I just dont like it now bumping at 120+psi....thats too high!

b16ahybrid

sounds risky to me.. i have never tried it nor do i know anybody that has so i cant back up my theory (that you would run to lean).If you do try it let us know, it would be interesting.
Most common is either 12:1 or 10:1 with stock injectors and 8:1 or 6:1 with 310cc injectors....
If you throw it on a dyno with a wide band o2 sensor and it shows that your runing rich i will have to believe you (since you have proof) once you post the dyno sheet with air/fuel ratio...

greyzone

That was at 10psi boost, 90psi FP and a/f in the 12's to redl;ine with stock injectiors one yeaR ago almost to the day

SEE OLD POST https://honda-tech.com/zerothread?id=89693


[Modified by greyzone, 11:48 PM 11/11/2002]


[Modified by greyzone, 10:04 PM 11/12/2002]


[Modified by greyzone, 10:05 PM 11/12/2002]


[Modified by greyzone, 10:10 PM 11/12/2002]

b16ahybrid

ok, well thats a little different then just using the fmu and fuel pump.I was under the impression that all you were using were the fmu and fuel pump i didn't know that you also were using the blue box and v-afc.That makes all the difference in the world.Either way the setup seems to work great for you.I would still recomend using larger injectors (like 440's) because you are really maxing the stock ones out,pushing 200whp is amazing.With the v-afc you can tune it so your idle is like stock, and driveability is the same..just a thought, well it seems to work for you so great work..

greyzone

cool man...thanks for your replies and thoughts

b16ahybrid

I gave it my best

metal-x

I have the same problem with my Jrsc setup, fuel preasure at idle is 50psi at WOT the readings are 120psi I have the cartech 2005 FMU too

b16ahybrid

whats the rest of your set-up?
fuel pump?how much boost?injector size? etc...

metal-x

JDM B18c, stock internals, Holly hi flow fuel pump, stock injectors (I have Rc 440's sitting at home) 6 psi boost



[Modified by metal-x, 12:18 PM 11/12/2002]

b16ahybrid

What ratio is your fmu?

b16ahybrid

I assume it's a 10:1 so your fuel pressure reading of 120psi is correct.
50psi idle +10psi (under full throttle) + 60psi (10x6psi= 60)=120psi....

greyzone

GReddy told me today that 120psi shouldnt be a problem with anything....although I probably dont really need anything over 100psi, 120psi shouldnt be "dangerous" on any of the fuel delivery systems/parts.

Base idle as high as 50+ becomes a real problem tho, running too rich chokes the engine out and give idle probs...

Anyway, I think I should be okay...but I am having to trim out 10 to 12% on the VAFC on WOT and even some at narrow throttle, but its good to have too much gas!!

TOo rich is always better that too lean with boost.

swrdply400mrelay

have almost your exact same setup! Greddy turbo, cartech fmu, stock injectors. But I was wondering if you have this same problem: almost everytime I get on my car and shift into 4th gear, I throw a check engine light. I pulled the code and it says defective/shorted primary O2 sensor. I figure I'm running way too rich because of the hi pressure from the fuel pump. I ordered a fuel pressure regulator and I'm waiting for that to come to lower the idle fuel pressure and hopefully that will solve the problem. Oh yea, the cartech fmu is also adjustable. I was told the **** on the side adjusts the ratio of the fuel so no discs are need like the Vortech. I've tried adjusting this but it still happens and I run lean. (EGT's hit 1600 by 3rd gear) Let me know what you do about running too rich. Thanks.


mike

TurboedGSR

wrong, base pressure makes no difference in a fmu set-up. the fmu just takes over and the stock or adustable FPR's pressure setting makes no difference, neither does the boost pressure. 10 psi on a 10:1 disk FMU = 100psi fuel pressure at full boost.

b16ahybrid

Really so let me get this right if my base fuel pressure is set at 38psi and i have a 6:1 fmu my fuel pressure under full boost(7psi) is only 40psi.....? sure buddy that makes comlpete sense .So your saying that the fmu is only providing 2psi of additional fuel pressure under full boost (7psi).
Think about what you just said read it over learn your facts before you tell me i'm wrong.I'm not claiming to know everything but i do know one thing and that is under full boost my fuel pressure is at 90psi not 42psi.
Lets do a little math here...this is what i have observed .My actual fuel pressure under a full 7psi of boost is 90psi. so take the 38psi of fuel pressure at idle, then add the 10psi of additional fuel pressure that the stock fpr adds under full throttle which equals what???? correct 48psi of fuel pressure with 0psi of boost.Are you still following me?..... ok so we have 48psi of fuel pressure and the fmu is still not doing anything.....because we have no boost.
now boost starts to build all the way up to 7psi......still following? ok....being that the fmu is a boost dependent fuel pressure regulator it adds fuel in proportion to boost (in this case it adds 6psi of fuel pressure per 1 psi of boost pressure)....still following?...ok we now have to add 42psi on top of the base fuel pressure of 48psi.... and that equals what.....?...... correct 90psi....wow and that is exactly what my fuel pressure gauge reads 90psi of fuel pressure......if I am WRONG please explain to me in detail how this who thing works and why everytime i have calculated out the total fuel pressure for my friends cars using the same formula it always equals what there fuel pressure gauge reads?
I am ready to learn.............


[Modified by b16ahybrid, 9:13 PM 11/12/2002]

TurboedGSR

the fpr and fmu are in series, fmu after the fpr. after fuel goes past the fpr the fmu holds it to build more pressure right. how can the fmu know to start building pressure from the static fuel pressure which you say is 40psi. i had always tought a fmu started from 0. am i wrong? are you using stock injectors and a 6:1 disk?

b16ahybrid

the fmu doesn't start from 0psi (actual) it starts from where the stock fpr leaves off, so in this case 40psi.So the car is actually running 40psi of fuel pressure but to the fmu it's the 0psi starting point.
the fmu sites idle until it sees boost, so if it built raied the pressure starting from 0psi or fuel pressure you would have no extra fuel for the first few psi of boost pressure.
Example in my case i'm using a 6:1 fmu and 40psi base fuel pressure.If it happens the way you are saying, i would have 40psi of fuel pressure until i reached 6.5psi of boost...make sense?nope.
Watching my fuel pressure gauge it's at roughly 48psi (38psi base+ 10psi under full throttle)under full throttle and 0psi of boost, once i hit 1psi of boost it jumps to 54psi 2psi of boost brings it to 60psi,3psi of boost brings it to 66psi of fuel and so on.It all happens so quick the fuel pressure just jumps constantly up to about 90psi.

So whatever your static fuel pressure is, thats the starting point for the fmu, which it uses as 0psi.
I'm using 310cc injectors not stock..and yes a 6:1 fmu.My aem is a 1:1 rising rate fpr, so my total ratio is 7:1 under boost.

TurboedGSR

i dont understand how the fmu can start from where the fpr left off. how would it know that psi, the only way would be to calibrate it to start from 40psi, but base fuel pressure is not the same for all cars/manufacturers and the fmu is a universal product. and yes thats what i am saying, i think you'd have 40 psi until you reach 7psi then your fmu would restrict the fuel enough to raise it to 42.

by your theory there would be no reason to even have a fpr. i could completely remove it and the fmu alone would keep my pressure at 40psi, then raise it 6psi for every pound of boost after.
but you say your gauge reads 90psi so i dont know, anyone else care to comment