Topic: HPFP or in tank pump... whats the real limiting fuel factor?

[rlhammon]

I've been doing some thinking about this again (dangerous when I'm thinking), and wondering a few things:

1) Has anyone pulled apart the new Buick fuel pump with is E85 capable (LHU engine).

I'm wondering how the issues of fuel supply from the HPFP is resolved.  Does the cam have a 4th lobe, or did they increase the output from the pump per lobe?  According to BOSH we need 1.1 cc/rev to fully supply E85 requirements, we don't need bigger injectors, we need for fuel.  So... one could get a new cam with a 4th lobe (each gives 0.3cc/rev, 4=1.2cc/rev), or one could increase the output from 0.3cc/rev to 0.4cc/rev.

Increasing would mean a bigger bore, and new diaphram though... and not sure which route the LHU engine takes.  I'm guessing others have looked at the LHU fuel HPFP and it's not a direct fit... but what about modifications to our HPFP to achieve the LHU design in our package?  That, of course, assumes we can achieve the fuel flow we need with our stock cams, since Bob, and I (and Dr. Jones) can't change our cams.

Thoughts?

[kennysabarese]

Here is some info on the buick pump from Rock Auto including part numbers.

http://www.rockauto.com/catalog/moreinfo.php?pk=2783336

[joshmass]

What I'd like to see actually is a datalog from an LHU engine running E85 so I can see how it handles the fuel pressure, inj angles and inj duration compared to the LNF. I've been playing around with the tune for a while now and have found some definite patterns of how they all affect each other as well as performance.

For those of you running the stock turbo though, I still don't see how any of this HPFP stuff is going to benefit you. The stock turbo has airflow limitations that you should hit way before fueling becomes an issue. I'm still struggling to understand why you feel that running E85 is going to change any of that. Once you're that far out of the efficiency range of the turbo, spraying water pre-turbo would be the only thing I could think of to try to cheat it and get more power. Unless I'm completely missing the point. I've been known to do that too.

[kennysabarese]

I'm sure there's a Buick forum, someone should ask to HPT log one of them running E85.

[snaponbob]

For those of you running the stock turbo though, I still don't see how any of this HPFP stuff is going to benefit you. The stock turbo has airflow limitations that you should hit way before fueling becomes an issue. I'm still struggling to understand why you feel that running E85 is going to change any of that. Once you're that far out of the efficiency range of the turbo, spraying water pre-turbo would be the only thing I could think of to try to cheat it and get more power. Unless I'm completely missing the point. I've been known to do that too.

If you referring to stock (non-performance) tunes (other than adjusting for E85), no changes in pumps would be needed. BUT, when people start tuning for all the power that can be made, the demand for the amount of liquid needed goes WAY up. Look at it this way - when performance tuning for straight gasoline tuners adjust the fuel tables (on F.I. engines) because if you can burn more gas you can make more power, or conversely as you try to make more power the engine NEEDS more gas. Just changing to E85 with similar power tuning the engine will need at least 25-40% more liquid because E85 latent heat is so low. None of this has anything to do with forced or non-forced induction. Start cranking in more aggressive tuning on an LNF on E85 the demand for liquid volume WILL tax the system to it's limits. The need for more liquid is satisfied with the dwell period for the injectors going way up. At high demand the HPFP may not be able to keep up with demand and the fuel rail pressure can drop down to the point (about 900psi) to drive the ECM into limp mode.

Hope that helps, Josh.

[joshmass]

If you referring to stock (non-performance) tunes (other than adjusting for E85), no changes in pumps would be needed.

I wasn't referring to the stock tune. I was referring to the stock turbo. If you can't upgrade the turbo then you're going to hit the limit of airflow prior to running into fueling issues. The work that was done a while ago http://www.solsticeforum.com/forum/976295-post15.html to plot the LNF against the K04 map shows that it's going to end up in the 50% efficiency range once you're up to 34 lb/min. I know that some have reached 40 lbs/min on the stock turbo but it can't be sustained for long periods.

So if this is the case, how does running E85 or any other blend of ethanol change it? The max power is the max power regardless of the fuel used. I feel that you can tune for the max power of the stock turbo on either fuel without running into the limits of the HPFP.

For those of us running upgraded turbos it's a different story. We can push more air so we need the extra fuel to keep it going.

[rlhammon]

So if this is the case, how does running E85 or any other blend of ethanol change it? The max power is the max power regardless of the fuel used. I feel that you can tune for the max power of the stock turbo on either fuel without running into the limits of the HPFP.

i wish I could give you a better answer than this Josh, but this is all I have.

I've tuned (Trifecta, so Vince has tuned) for 93/95/100/104 octane gas, and I've tuned for pure E85, and E47.

The best "power" I've had has been on E85; however I run into issues as Bob pointed out, the car can go into limp mode under sustained WOT conditions due to lack of fuel - because fuel rail drops to 900 psi.  I have no on track data for this though, as I don't have a way to run with a mounted computer safely during an event.  This issue has *never* happened on the street, and only happens in certain instances (long WOT states, approx. 3 or 5 seconds in I see the issue) when on a course.

Now.. .I put "power" in quotes, because Bob and I are looking, in many cases for maximum torque to get us moving again out of driving elements.  Horsepower is great, torque (IMO) is greater for us... I don't see the same torque numbers under gasoline that I do under E*, E* has always been better.

So... I'm looking for a route to provide more fuel.  BOSCH indicates we need 1.2cc/rev of E85 to sustain fuel pressure and flow for use.  We know our pump doesn't do that... BOSCH also indicates no need to increase air flow, even with the stock turbo to run E85.  The other issue with this is that their test vehicle isn't trying to put down max hp/tq, and I think if I wanted to keep things street manageable, I don't need more fuel even on E85... seeing as on E85 I can drive on the street without issues today if I wanted.

Not trying to be confrontational (in case any of this reads that way)... but trying to learn.  You all here have more knowledge in this than I, and I've picked Josh's brain via FB for some time on this trying to learn.

[joshmass]

The best "power" I've had has been on E85; however I run into issues as Bob pointed out, the car can go into limp mode under sustained WOT conditions due to lack of fuel - because fuel rail drops to 900 psi. 

Now.. .I put "power" in quotes, because Bob and I are looking, in many cases for maximum torque to get us moving again out of driving elements.  Horsepower is great, torque (IMO) is greater for us... I don't see the same torque numbers under gasoline that I do under E*, E* has always been better.

I know why E85 is allowing you to put down better torque numbers than a lower octane fuel so that's not what I'm questioning really. I guess what I'm trying to ask is what are those peak numbers? I'm also really curious to know how you guys feel that it's the pump too since you can't datalog while it's happening.

For the record, I'm also running into the same issue with limp mode (while under sustained boost at 30psi.) I'm not using E85 but I do have a water/meth kit that is adding octane. The difference is that I'm datalogging while this is happening and I can tell you that it's not fuel pressure related. I've linked one of the screen grabs I posted to my FB page to illustrate the point. You can see that the fuel pressure isn't even close to being maxed out and it continues to hold pressure past the point where limp mode kicks in and kills the throttle.

http://www.flickr.com/photos/43695877@N05/6997106559/#

[kennysabarese]

Can you have a passenger hold the laptop while you are on the track?

Or just make a mounting system for the laptop on the floor.

Or just get HPT pro and you don't need a computer at all.

All worthwhile in diagnosing these, and future problems you will have while racing. Heck I'd setup a test autocross just to figure out these issues.

[snaponbob]

Josh, if you are using gasoline, even with spray, the existing system will keep up with demand. EVERYTHING changes with E85. As I explained, the VOLUME of fuel required goes UP solely because it IS E85, and not gasoline. I am confident that my explanation above answers your question. The requirement, under racing conditions, for the VOLUME of liquid is greater than the pump can supply. Vince, DDM, ZZP, Werks, and many tuners know this, and this is where I am getting my info. Kind of like one KNOWS there is not enough air in the tire if it's FLAT !!!! The symptoms of the power loss LNF's running E85 are already known. We aren't making this up.   

[joshmass]

Guys:

I understand everything you're saying about E85. I also know exactly what you're talking about when it comes to the limitations of the fuel system in the LNF in combination with E85. I'm not even questioning the problems you're having per se. Obviously E85 is going to give you better TQ numbers down low versus pump gas. The knock resistance of ethanol allows Vince (or whoever else) to advance the timing down low more than pump gas would allow for so you're gonna get the extra performance from using it. And at low rpm fuel volume is not an issue. But you're talking about the fuel system quitting up top and that's where I'm trying to understand the thought process.

In my mind, it all comes back around to what kind of HP/TQ numbers are you trying to reach and where are you at right now? What PSI are you peaking out at? How close are you to running out of turbo? What RPM are you at when you trigger limp mode? In the big scheme of things, are you beating your heads against a wall to gain 2HP?

I'm really not trying to be argumentative here either. I know that tone is a hard thing to get across on the web. I'm genuinely curious to know these things in order to better understand the issues we're all facing with this motor/ECU. I've spent too many hours of my life culling the web for answers

[tazz]

Does anyone have a dyno graph of a tuned E47 vs E85 tuned car that is stock or close to stock in all other aspects?
The reason I ask is the study I posted in another thread states that "For fuel blends above E20 the maximum torque curve was not significantly limited. E20 can provide 97% of the peak torque of E85."
If that's the case were talking about 10wtq difference between E47 and E85 and IMO not going to make a difference but I don't AutoX either so I might be missing something.
Im running a E47 tune right now and it's crazy withn ton's of power and ton's torque from 3.5K on to 6.5K but I also have an automatic.  On average I'm adding 17% more fuel and when im in max boost I'm adding about 4% on top of the 17% so 21% more fuel and no fuel starvation issue.
Im at 23* timing on the top end and only 23psi of boost since I dialed it back from 25psi and I can hold 23 all the way to 6.5K.
 

[joshmass]

The reason I ask is the study I posted in another thread states that "For fuel blends above E20 the maximum torque curve was not significantly limited. E20 can provide 97% of the peak torque of E85."

I read the Delphi white paper that was posted and it's exactly my point here. But not knowing where they're at or where they want to go makes it difficult to understand what they want to get out of the fuel system as it stands.

[rlhammon]

Guys:

I understand everything you're saying about E85. I also know exactly what you're talking about when it comes to the limitations of the fuel system in the LNF in combination with E85. I'm not even questioning the problems you're having per se. Obviously E85 is going to give you better TQ numbers down low versus pump gas. The knock resistance of ethanol allows Vince (or whoever else) to advance the timing down low more than pump gas would allow for so you're gonna get the extra performance from using it. And at low rpm fuel volume is not an issue. But you're talking about the fuel system quitting up top and that's where I'm trying to understand the thought process.

In my mind, it all comes back around to what kind of HP/TQ numbers are you trying to reach and where are you at right now? What PSI are you peaking out at? How close are you to running out of turbo? What RPM are you at when you trigger limp mode? In the big scheme of things, are you beating your heads against a wall to gain 2HP?

I'm really not trying to be argumentative here either. I know that tone is a hard thing to get across on the web. I'm genuinely curious to know these things in order to better understand the issues we're all facing with this motor/ECU. I've spent too many hours of my life culling the web for answers

Josh, I've corresponded enough with you to know you're not being argumentative.. I just wanted to make it clear in case the proper tone wasn't seen in my message.  Seeing as I couldn't answer your questions with data, I didn't want it to come across poorly.  Thanks for understanding.

As for datalogging an autocross run, I need a wireless way to do it.  I can't have loose wires in the care, and frankly while I'm sure I could wire up something that's safety approved, I'd be borrwing equipment / setup etc.  Now.. if I did this at a test and tune that might be different (which is essentially what Kenny was saying when he said set up your own).  As far as datalogging, I have Vince's Trifecta dealer package (which I can't read the logs from, unless someone else know how to) which I can send the logs to him, and I have the Torque app on my Android phone.  That has limited access to PID's, but I believe fuel rail pressure is one of them... that might work for our issue.

As to where I'm at, and where I'm trying to get to... 1) I don't know currently, 2) MORE.  I know... that doesn't answer anything.  I do know that my E47 tune does not feel as strong as my E85 tune.  I'd have to get on a dyno with E85 in the tank, and then make some pulls, and top off to a 50/50 mix to get to E47 and make some pulls.  Maybe I can get ZZP to work me on that... they are only 20 mins. from my place.

To Tazz's comments... when I was running E85 I had timing to 25*+ and was at 25 psi (which tailed off to 23 in the mid 5k's).  We dropped timing back and limited to 23 psi, but even then I had issues on a course run.  After that I moved back to 93 octane with a 25 psi setup and was quicker on course the next day (in comparison to my competition), but that's because the car never lost power as it did with E85 the day before.

Part of my issue is it's hard to test the driving conditions Bob/Alex/I drive under when autocrossing.  It's also hard to give up an event trying to test a fueling issue... but I'm an engineer, and understand the need for data to make decisions.

Back to Josh's comment, I'm find maxing out the system before a failure, even if that means I'm 90% of a hypothetical maximum.  However, in the few events I've tried dialing it back, I still had the issue.  If I can find a way to datalog while on course, I've got some test and tunes I can do this at.  Alex has HP Tuners... so that might be an option if he is available depending on what he has credits unlocked for since we both have '07 GXP's.

[snaponbob]

The fuel delivery problems are not so much turbo related as it is tune related. As I said, the way the E tunes are taking advantage of ethanol IS the ability to advance spark curves, about the tuner's ability to put MORE fuel in to burn. If MORE fuel can be burned for a LONGER period of time, there will be more power produced. As I understand it, that is it. Forget ethanol for a moment, and consider higher octane gasoline. The higher the octane the more advance can be dialed in and the gasoline burns longer. Tune to and run 100 and you get more power than 93 tuned to 93. E85 just makes that burn time so much longer. BUT, it takes a LOT more fuel if you are running methanol because it has less latent heat so MUST burn longer.

My biggest performance issues (and many other E tuned LNFs) above 5-5500 rpm have been all sorts of farting and popping racket. Everyone I have spoken with have said is the fuel rail is dropping pressure. THAT is the HPFP volume limits. At those rpm's boost is below 20. When I switched to E60 the problem all be vanished. Why? More gasoline content is a reasonable conclusion because there was enough liquid being delivered because the injector dwell was rolled back some, and so the fuel rail was not emptying out. It isn't boost related - it's the dwell period of the injectors being so long that the HPFP can not keep up.

That said, the stock turbo is still the stock turbo, and they poop out (at least don't do much real work) above 5200 rpm regardless of what is in the tank. The reason the E tunes make so much power above that point is more fuel/more advance. Above 6500 it get lame, but STILL has more pull than straight gas tunes. I have run 91 and 100 octane Wester tunes and Trifecta E tunes. The 100 had lots more mid range and a more stretched out power band above 5200, and the E tunes 'made the weather change' in the mid range and pulled further than 100. I didn't ask for a specific power number, I simply said give me what can be produced without risking the engine. My gas tunes easily peaked at about 25psi but slipped away because the computer STILL manages stuff. My E tunes run to about 23 and slip off. As for  a few horsepower - no. We are  over DOZENS of horsepower.

[joshmass]

My biggest performance issues (and many other E tuned LNFs) above 5-5500 rpm have been all sorts of farting and popping racket. Everyone I have spoken with have said is the fuel rail is dropping pressure.

I'm surprised to hear that, seeing that when I had the same issue occurring in my tune it had nothing to do with fuel rail pressure. It was more a function of the duration of the fuel injection pulse and the limited window we have to spray fuel in the cylinder. By increasing the injection window we were able to get more fuel in there (same fuel pressure mind you) and the stuttering went away. The timing of the injection had to be advanced as well to compensate. It would make sense that this would be more of a problem at high RPM for obvious reasons.

[snaponbob]

I'm surprised to hear that, seeing that when I had the same issue occurring in my tune it had nothing to do with fuel rail pressure. It was more a function of the duration of the fuel injection pulse and the limited window we have to spray fuel in the cylinder. By increasing the injection window we were able to get more fuel in there (same fuel pressure mind you) and the stuttering went away. The timing of the injection had to be advanced as well to compensate. It would make sense that this would be more of a problem at high RPM for obvious reasons.

Were you on gasoline or E85?

[joshmass]

Were you on gasoline or E85?

Gasoline. But you and rlhammond both see where this becomes a greater issue with E85. You're fighting time not pressure. That's also why the ZZP cams work. As a function of the lobe design working on the pump you're adding fuel volume within the same window. The lobes aren't changing the fuel rail pressure at all.

So how is pressure dropping in the rail? I wonder if it's more of an effect of limp mode and not the cause of limp mode. 

[rlhammon]

Gasoline. But you and rlhammond both see where this becomes a greater issue with E85. You're fighting time not pressure. That's also why the ZZP cams work. As a function of the lobe design working on the pump you're adding fuel volume within the same window. The lobes aren't changing the fuel rail pressure at all.

So how is pressure dropping in the rail? I wonder if it's more of an effect of limp mode and not the cause of limp mode. 

So, you are exactly right in what needs to (and in our case *has been*) done.  A longer injector window has been achieved by copying what GM did with the turbo Buick.  We start the injector spray sooner, because we can't end it later in the cycle.  I've been told (don't shoot the messenger) that the BOSCH ECU can not control an injector window greater than 12ms, and I'm pushing that envelope by starting sooner in the cycle.  Beyond that 12ms window it's my understanding that we demand more fuel at the injectors than is being supplied by the HPFP.  Lack of fuel in the rail will drop the pressure... and the car protects itself from failure (thankfully).

That's my understanding of how the pressure drops.  I've played with the fuel rail pressure, and say no performance advantage with higher fuel rail pressures than stock.  I'd have to pull out my fluid dynamics books from college, but I believe there's a squared factor in the relation to volume and pressure, so the rail pressure head room we have above stock doesn't provide us enough to overcome the pressure drop.

[snaponbob]

Gasoline. But you and rlhammond both see where this becomes a greater issue with E85. You're fighting time not pressure. That's also why the ZZP cams work. As a function of the lobe design working on the pump you're adding fuel volume within the same window. The lobes aren't changing the fuel rail pressure at all.

So how is pressure dropping in the rail? I wonder if it's more of an effect of limp mode and not the cause of limp mode. 

I never said it was a pressure issue. You did. I have repeated said it was a volume issue. The pressure drops in the fuel rail because the dwell period is so long that the injectors are emptying the rail faster than the OEM HPFP can fill it. It IS the cause of the limp. "Limp" is induced to protect the engine. As for resolving the problem, that is a different issue.

Somehow I am failing to explain E85. The use of E85 requires MORE liquid to be injected than the HPFP can supply to the rail in very high demand circumstances. Somebody help me understand what I am failing to explain.

[rlhammon]

I never said it was a pressure issue. You did. I have repeated said it was a volume issue. The pressure drops in the fuel rail because the dwell period is so long that the injectors are emptying the rail faster than the OEM HPFP can fill it. It IS the cause of the limp. "Limp" is induced to protect the engine. As for resolving the problem, that is a different issue.

Bob, you did say (900psi)... so your response could be read as a pressure issue.  I tried explaining above, that it's the lack of volume in the fuel rail, because the injectors have sprayed out more than the HPFP has supplied.

I guess we could look at it like this:

1) What is the volume / time that the injectors deliver?
2) What is the time the injectors are spraying? (12ms max, as I've been told)
3) What is the volume the HPFP can supply (.9cc / rev)
4) How does the equation balance out:  fuel sprayed vs. fuel supplied

That should show us *if* there is a volume issue, which would/could manifest itself as a drop in pressure, due to the lack of supplied fuel, right?

[snaponbob]

Bob, you did say (900psi)... so your response could be read as a pressure issue.  I tried explaining above, that it's the lack of volume in the fuel rail, because the injectors have sprayed out more than the HPFP has supplied.

I guess we could look at it like this:

1) What is the volume / time that the injectors deliver?
2) What is the time the injectors are spraying? (12ms max, as I've been told)
3) What is the volume the HPFP can supply (.9cc / rev)
4) How does the equation balance out:  fuel sprayed vs. fuel supplied

That should show us *if* there is a volume issue, which would/could manifest itself as a drop in pressure, due to the lack of supplied fuel, right?

Vince told me the threshold is 900. If there is not enough volume, the pressure will drop. Imagine blowing up a balloon. If there is not enough volume of air, the pressure will not increase.

[joshmass]

Bob, you did say (900psi)... so your response could be read as a pressure issue.  I tried explaining above, that it's the lack of volume in the fuel rail, because the injectors have sprayed out more than the HPFP has supplied.

I guess we could look at it like this:

1) What is the volume / time that the injectors deliver?
2) What is the time the injectors are spraying? (12ms max, as I've been told)
3) What is the volume the HPFP can supply (.9cc / rev)
4) How does the equation balance out:  fuel sprayed vs. fuel supplied

That should show us *if* there is a volume issue, which would/could manifest itself as a drop in pressure, due to the lack of supplied fuel, right?

Yes. That was the specific information I needed to know and it was the volume calculation in your points above that I got stuck on months ago. With port fueling the math is fairly easy to calculate fuel requirements and injector sizing. DI changed the game and without some sort of way to calculate it I think that every tuner out there had to figure it out by trial and error.

I also remember a European tuner telling me about cavitation occurring in high pressure fuel lines if the low pressure fuel pump wasn't pumping enough volume. Unfortunately it was a brief conversation and I never pressed him for more details. I wonder if this was the scenario he was talking about. He had dealt with Audi/VW tunes.

So coming full circle, has anyone tested an upgraded low pressure pump in conjunction with these extended injection times to see if it will affect the HPFP pressure? If you're saying that the low pressure condition is caused by the fact that the injectors are outpacing the HPFP, then it would seem that the low pressure pump could be the culprit.

[miller11386]

bottom line, someone who has the fueling issue needs to replace their in tank pump with a double pumper/similar crazy volume low pressure pump.

I started this thread on the theory that a higher pressure  & volume on the low side may increase pressure/volume on the higher side. Diesels have done this for years to increase their power.

Throw this in the tank and see if it solves your fueling issues. .. 800lbs per hr at 80psi!

 http://aeromotiveinc.com/products-page/fuel-pumps/11104-eliminator-fuel-pump/

[joshmass]

The pressure drops in the fuel rail because the dwell period is so long that the injectors are emptying the rail faster than the OEM HPFP can fill it.

That's what I wasn't getting from your earlier posts because....

Somehow I am failing to explain E85.

....this is what you kept trying to do when it wasn't necessary.

I just went back and read the entire thread again and you came close a few times but just never quite got there. :p

I can now wrap my brain around the problem and this gives me some more food for thought on my own tune. Thanks guys!