Walbro 255; stock FPR?

[Eclipse98_RS]

Ok, first off I did a search and couldnt find any of these two linked together and I had a question about it. I am going to be getting a walbro 255 in my car very soon. The question I have is " If I have 550cc Injectors, and a wally 255, will it overpower my stock FPR?"
Any info is welcomed, and like I said I did a search and couldnt come up with anything, so if you find some info please point me towards that.
Thanks,
-Dan

 

[oldman]

I don't think many people are saying they have no overrun, rather they are skeptical that overrun is hurting their car.

Some are debating whether overrun occurs at all, some are claiming overrun can be tuned out.

Isn't idle a consistent condition? It won't be "load based" or affected by "non linear" changes.

I'll use dsmlink as an example. If you notice that your LTFT lo's were maxed out subtracting fuel wouldn't that be a clue of overrun? If at idle you had a wideband installed and it was reading very rich wouldn't that be a clue of overrun?

Now what if at 50hz airflow slider you starting subtracting airflow? Of if you had a wideband and tried to tune for 14.7 at idle using airflow sliders.

Overrun absolutely is load based and the changes are absolutely non-linear. Your fpr will not rise 1:1 until YOUR SYSTEM USES UP THE EXCESS FUEL VOLUME caused by overrun, the quicker you use up the excess fuel the quicker your fpr goes back to functioning 1:1, reason why it is load based and non-linear. Sure you can come close at idle, depending on degree of overrun, by playing with the 50 hz slider at idle but what are you going to do at 10% throttle, 15% throttle, 1k rpm, 5k rpm, -10inHG, 0psi, 2psi, 8psi, changes in ambient temperature, going up hill, down hill..........etc.? Too many variables to be considered creating too much inconsistencies where your LTFTlow mid high and even some WOTs differs from log to log, run to run. Think of it as trying to tune out venting your BOV, how will you predict at what psi, rpm, intake temperature...etc. one will blow off? Now try and imagine doing all this with a piggyback system where adjustments are RPM based only.

Why would anyone who pays $800 for a DSMLink setup and cheap out on $150 AFPR setup? To prove a point? That's like using 87 octan on a 911 turbo. The key to precise tuning is consistency.

 

[elfroggo]

As an alternative to using an afpr, couldn't you wire the pump such that it had reduced voltage at idle?

Basically I'm referring to this thread
http://www.dsmlink.com/forums/showthread.php?t=469

But thanks for the last post, it did clarify some things.

This is a page on RRE's site about varying pump voltages

http://www.roadraceengineering.com/evo/tech/fuelpumpinfo.htm

 

[oldman]

As an alternative to using an afpr, couldn't you wire the pump such that it had reduced voltage at idle?

Basically I'm referring to this thread
http://www.dsmlink.com/forums/showthread.php?t=469

But thanks for the last post, it did clarify some things.

This is a page on RRE's site about varying pump voltages

http://www.roadraceengineering.com/evo/tech/fuelpumpinfo.htm

Oh great more reading , I need to get under the car now, I will study the Link link later and get back to you on whether it's a real fix or just another bandage.

 

[CanadianTSi]

Take this for what it's worth...

I've run a 255 on the Stock FPR for years with Zero driveability problems, even with the S-AFC controlling my 650's my wideband always read a solid 14.7-15.0.

I am about to Install an Aeromotive Adjustabe FPR just so I know that my FP is actually where it's supposed to be.

 

[oldman]

I've run a 255 on the Stock FPR for years with Zero driveability problems, even with the S-AFC controlling my 650's my wideband always read a solid 14.7-15.0.

Correct me if I'm wrong Tyler, wasn't it the 190 that you have been running for years? In any case, I'm glad you've decided to do things the "right way".

 

[Eclipse98_RS]

So hopefully I dont miss anything, but the main symptom of over run will be bad gas mileage? Let me know so I know what to look for. Thanks

 

[Benag]

I have a question concerning the stock fpr and injectors with a 255 (which is what I am running)(right now anyway). Because the 255 causes overrun then I'm assuming that there is plenty of fuel pressure which is why you guys are saying it will cause you to run rich. Well when I am boosting say in 5th at not too high rpms I have misfire and my a/f gauge shows lean during the brief misfire. Replacing the fuel filter helped after the 255 install, when my car kind of seemed to run like a turd. What would be causing the lean condition?

 

[nightspeed87]

So hopefully I dont miss anything, but the main symptom of over run will be bad gas mileage? Let me know so I know what to look for. Thanks

Dude just get a stinking afpr.
Old man has already told you everything to look for and all the sympthoms.
If you dont have money for one yet then fine, just get one when you do get the money.
I dont think a little fuel pressure over run is that bad because between high rpm shifts that extra fuel
can help to cool the cylinder down a bit.. Evos purposely have a bit of overrun because of this.
But when it becomes excessive your just waisting gas at idle and like Oldman said, washing out the cylinder walls.
Putting a 255 on a stock fuel return system could result in what I just mentioned as excessive.
But will you initially damage anything, no. Waist gas yes. Hurt injectors, no. Give you a sloppy tune, yes.


Now anyways, my question concerning my fuel situation which is a little different.

According to a few things ive gathered, and a few things old man said,

For one he said the smaller the injectors the longer the duration of over run..

That statement makes sense considering a larger injector lets more out per opening.
Therefore should mean that it runs even richer during over run with a bigger injector, just for not
as long a period of time vs. the small inj... Correct?

FYI I run 850s...

Now to complicate things a little bit,
I have a rewired high pressure walbro 255 ( No afpr )
And I run a dsm chip tune at 11.1 afr and i am running the non turbo fpr which gives a base pressure of 47.6 I believe which we compensated in the size the injectors should be to run that fpr in the chip so it would run correctly. ( Turned out being like 900ccs we had to tell the ecu I cant remember if thats the exact compensation number off the top of my head )
and 30 injector deadtime. Which when Jeff from keydiver previously had burned me a chip awhile back he ran a tad less deadtime then what we have our current chip set up with ( That we burned ourself so its not a keydiver chip this time.)

Also according to some other info on this page, appears the higher the base pressure the less harsh the over run. According to what was said about how 2gs can deal with over run better and they run 43psi vs 1gs running 37 psi.
If thats true i wonder what that would suggest on my set up of 47.6psi.

And one last thing, I am changing out the walbro for the denso 260lph fp ( TT Supra )
Because my walbro is obnoxiously loud... I mean you can hear it from 15 feet away.
Therefore id like to assume putting that supra pump will increase fp over run.

 

[dsm5150]

Not running a regulator is like entering an infant in fightclub.

DSMParts.Com Bolt on fuel pressure regulator. 149.99 http://www.dsmparts.com/customer/product.php?productid=403&cat=&page=1

Summit for the gauge 17.95 http://store.summitracing.com/partd...art=SUM-800199&N=700+-127729+115&autoview=sku

If anything, forget it all and do it to save the gas at idle...the prices will never go below 2.00 a gallon again.

damn their out of stock

 

[Afroclipse]

The fact of the matter is it does overun and thats not good for you, the biggest symptom you will have is crappy idle. Now you will hear a lot of different opinions on this topic but the fact of the matter is that you shouldn't do it, i run a 190 and its at 65 where as stock is 43ish where do you think a 255 will be ( i don't know) higher i would guess, so just get a afpr and you won't have to worry about it.

Just like a condom you don't have to worry about pregnancies or std's as much as you would if you didn't strap on, point being "prevention is better than cure protect your ride".

Just my .02, i just brought it back in to play

 

[DallasN2O]

I just installed 550's, 255lph, s-afc neo on my car w/ stock fpr and it seems that after reading all of this, I'm having overrun problems. I can't get the fuel trims on the logger to read less than 100% even leaning it way out with the afc. Also the exhaust is dark and smells like gas. I am getting random knocks on the logger even if i zero the afc out with should be very rich with the 255 and 550s. So I'm pretty sure its not PK. My O2 readings at WOT are at like .84 which is supposed to be lean not rich so I'm confused. Oldman would you say that an afpr would alleviate most of these symptoms?

Sorry to hijack.

 

[oldman]

It certainly can. As for why you're lean under WOT?

1. FPR overrun has little effect under WOT at higher RPM.

2. O2 reading is not to be used or trusted for WOT conditions.

 

[MidShipCivic]

Thanks old man, I just had to say that.

 

[DallasN2O]

It certainly can. As for why you're lean under WOT?

1. FPR overrun has little effect under WOT at higher RPM.

2. O2 reading is not to be used or trusted for WOT conditions.

Would the overrun cause my fuel trims to stay at 100% exactly or will mmcd even show a number higher than 100? It doesn't move from 100.. all 3 trims.

 

[oldman]

Would the overrun cause my fuel trims to stay at 100% exactly or will mmcd even show a number higher than 100? It doesn't move from 100.. all 3 trims.

If all three of you LTFT (Long term fuel trim) are stuck at 100, it can only mean the following.

1. You have just reset your ECU and you have not driven the car enough for the trims to be update.

2. Your car is not getting into closed loop. Does your O2 cycle up and down during idle and part throttle? Does your STFT (short term fuel trim) move at all?

 

[DallasN2O]

Ok after my last post I installed the dejon intake with the 2G MAF and reset my ECU. BIG improvement. Although the exhaust still smells rich, I get lots less knock and my fuel trims move now. Although my O2 does not cycle at idle.. it sits at like .03v and does not cycle even at part throttle. Does this mean the O2 sensor is bad? My AFPR will be in tomorrow and hopefully that will take care of the overrun I still seem to be experiencing.

 

[oldman]

Although my O2 does not cycle at idle.. it sits at like .03v and does not cycle even at part throttle. Does this mean the O2 sensor is bad?

Bingo!

 

[pickens]

Not to add to what you probably shouldn't do.....but I've been running my 255 pump for years on the stock AFPR. And yes I use a fuel guage.

Basically, my fuel pressure is super high during idle. The car still idles very smooth even with my FP1 cams. However, I either can tune so my fuel trims are in the 5% range during idle but then nearly maxed out under cruise, or I can do it vice versa. Other than that I haven't seen any negative effects (mpg, knock, rich, etc). The ecu does a decent job compensating. FWIW, my wideband just about always read 14.8 under idle or cruise.

So it shouldn't hurt to do it, but its not a bad idea to have an aftermarket FPR.

 

[fmb1987]

What about 2 x 255 and 1000cc ???

 

[fuzzydoodle]

So then because I am ready to get an upgraded fuel system apart from the 550's I have in now, controlled only by an afc2..I am wondering if an evo fuel pump will work with no overrun, and no afpr? Or are evo stock pressure regs set different or to hold different pressures? Only because I was going for a 255 re-wired with an afpr, till someone told me this alternate setup will work, and I would like to keep under the hood as un-flashy as possible.. Oh and because evo's come with 560's? And are pretty capable of picking up a moose's ass and running with it (theoreticaly speaking) with only small tuning changes?

 

[DallasN2O]

Ok I replaced the O2 sensor and the coolant temp sensor and my car is still stuck in open loop (voltage doesnt cycle at idle or at part throttle). This started after I installed the AFC.. also I can't get the afc to show my rpms and I've tried two different wires for the rpm wire. Don't know if these two problems are related but they're both strange.

 

[oldman]

Ok I replaced the O2 sensor and the coolant temp sensor and my car is still stuck in open loop (voltage doesnt cycle at idle or at part throttle). This started after I installed the AFC.. also I can't get the afc to show my rpms and I've tried two different wires for the rpm wire. Don't know if these two problems are related but they're both strange.

What are your coolant temperature readings? I would also go back and double check your AFC wirings, installation can be some what confusing depending on which way you're looking at the plugs.

 

[DallasN2O]

Readings? If you are talking about the temp guage it sits in the middle once warmed up. Is there another reading I should check? Also, I just took it out for another test run.. I disabled the wastegate and my car wont boost past 10 psi. I thought my mbc was broken so that's why I unhooked the wg. Could my wg be stuck open and causing my af to be off enough for the car to stay in openloop? Just throwing out ideas.

 

[turbotalon1g]

Just to help you out, another vote here for upgrade the AFPR when you do the pump.

 

[DallasN2O]

update on the fuel trims.. i reset the ecu.. now my low fuel trim is going down to like 81.2% and it hardly moves at all. Is the low trim supposed to jump around pretty quickly or is it very slow? 81.2% = extremely lean?