How does the EZ efi determine what AFR the engine will run at? We use the heck out of the new Holley HP system, it is self learning and tuning, but we still have to determine the AFR we want it to run at

you plug in desired a/f at idle, cruise, and wot.

So you're telling a guy that has experience with EFI of different types and 2 cars that run very well with a particular setup that they don't work properly?

Yes, the referenced fuel pressure regulator is a must for any EFI system... especially EZ EFI.

Most people... even experienced tuners miss this one because they don't understand how it works.

I understand the reason for it, but I will disagree that it's a must on all systems. I've done many with and without the reference line, and they all ran perfect.

I also understand and I also must disagree. When you say "must", it means the system can not function without it. That is clearly not the case. Maybe separating preference from requirements is the issue here. :cheers:

No, for it to work properly... and if you actually did some testing with the injectors and saw what they did when you didn't reference them... you would know why.. For the EZ EFI it is a must since the ECU uses fuel pressure as a reference.

Really all efi systems should be this way. People get lazy or think there is no reason for it but there is.

So, if you understand how it works then your saying it is correct for the injector to flow more fuel at an idle than it does at WOT?

of course not. But referencing the regulator will lower the fuel pressure at idle/cruise/higher vacuum areas, and increase it as the load increases and vacuum drops. In an adjustable system (not the EZ EFI) you can set the injector pulse width to compensate for a non-changing fuel pressure. Now an injector has a minimum amount of time it takes just to function, so if you have a real large (or too large) injector you can have idle issues and the lower fuel pressure with referencing would help. But I've run 95# injectors without issue. I boost reference for blown engines, but again have done many N/A setups without referencing and never noticed a single hiccup.

I am not challenging your knowledge, I'm just a home hobby tuner guy. I just can't see the issue you're describing.

ok, so you really don't understand. I am not having a pissing contest either... Greg is a really nice guy and from the same area I'm from too. I am just trying to debunk some bad info that I read.

So, really the reason you touched on is the injector flow... yes they have a minimum time it takes to open "dead time" but what we want it to keep the pressure differential across the injector constant so we just tune the fuel curve and not chasing an injector that flows different amounts of fuel at different engine vac.

when you do not reference the regulator here is what you have. At idle and cruise when you have hi vac the injector will actually flow more fuel without the line connected because the pressure is say 45psi and under vac to it helps pull fuel out of the injector, so....net you have more fuel flow if you have no vac reference. So 45psi and -10psi equals a net of 55psi flow... the injector will flow more fuel in this vac area without the line connected. The problem is worse as the injector size gets larger.

Now if you do reference the regulator you have 45psi fuel pressure... and say -10psi vac you have 35psi fuel pressure and -10psi still equals 45psi net... the injector flow rate stays the same. As the injector sees less vac then it keeps the same net flow rate across the injector no matter what the engine vac or boost does. That is why you actually boost reference the regulator... so the boost does not push the fuel back into the rail. 45psi... 10psi boost 45psi + 10psi = 55psi but still a net of 45psi fuel pressure since the intake has 10psi in it.

You will find that if you use the vac referenced regulator and actually use it all the time it will make tuning easier.

Now "opening time" or "dead time" is something totally different... it is the minimum actual time it takes for the injector to open and start flowing fuel.. That is a different table and not a table for tuning... it should be a compensation for each style of injector. If that table isn't correct then when you ask for a 5% change in fuel you may only be getting a 3% change actually. Having a referenced fuel pressure regulator effects the opening time some since the vac makes it easier to open the injector but that is part of the reason the reference helps there too. Most aftermarket ECUs only use injector dead time as a reference in voltage vs time and don't take in account fuel pressure as a third axis. GM does in the KPA vs flow rate in the LS computers. And a second table as injector flow vs battery voltage.

Injector dead time/opening time is a value added back to the commanded injector pulse width that is programmed into the ecu... it is even more important as RPM gets real hi and the actual time to get the job done gets shorter.

Now that we said all of that... the EZ EFI especially needs this because when you enter the fuel pressure... it assums that the given pressure is at rest with no vac line... that decided how much pressure you have off what the map sensor shows. Then it decides how much PW it needs to maintain a target A/F ratio. It will have a harder time tuning itself when it is assuming the fuel pressure is lower than it really is.

Boosted I reference it, N/A I sometimes do and sometimes don't. I like to run rear-mounted regulators too so that's a whole 'nother area we might argue about........... :D

I appreciate the info.

Brian --

Good discussion!

So.... if the A/F ratio is set for 14:1 and the actual, and set, match - what possible difference does it make? I.E., you set the idle A/F and the ECU with the help of the O2 sensor makes sure that's where you're at.... I would ASSume then that the PW is properly set/adequate etc for the situation?

I too appreciate this discussion. You said exactly what I was thinking Greg. I ASSumed that this is what made the EZ-EFI easy! You set the A/F ratio you want and based on the spent gasses tested by the wide band O2 sensor the computer changes the settings necessary to maintain that AFR. I understand Brian's explanation and don't disagree with it. My thing is, I went with the EZ-EFI so I didn't have to know all that. We didn't want to spend 5k on the induction and another 5k in tuning and dyno time. And yes I think we all know there are people doing that. I also wanted to do as Jody said and use a rear mounted regulator. As he said this is a whole different discussion. For me I will go back to my previous comment. "Must" implies no other option. I think you Greg have proven that the EZ-EFI system works well when applied to the correct application and without vac. ref. to boot. Jody has also found an application that did not suit it with Charlie's Cammer. In Jody's case, I don't think it had anything to do with the lack of a vac. ref. regulator. To me this concludes it is not a "Must". I'm not trying to maintain a pissing match here either, but as we have discussed in the past, there are many people that read these posts who do not participate in the discussion. For them to read this and feel they "must" do this I think is not right. Anyway, I am comfortable with what he have done so far. When the truck is on the road, I will know whether I just stuck my size 14 in my mouth! :cheers:

I gotta say this, these type of threads can contain the best information. And Brian, I'm not trying to be a Jackwagon. :lol: A debate over this stuff is better than a lot of other things! :thumbsup:

I did move the regulator up to the engine and ran a vacuum reference and it made no difference in how it ran or the issues I was having. The issue with Charley's car is that the EZ EFI is not the right system for that combo, he's going to an XFI.

Agreed, that the EZ EFI is good for what it was intended for... not something as radical as that car maybe.

I do totally disagree that the vac line does not have to be connected to the regulator in the EZ especially.. it will run rich in most cases if you do not do this. If you switch it from not hooked up to hooked up then it will take time to learn out the areas where it was trying tune around the perssure differential. The more vac the engine makes the more this will be a problem.

I am saying this for the exact reason you are saying it "does not matter" so other people on the board that read this do it the right way and don't try to over think it... like you said if you wanted to know this then you would buy a tuning EFI system. In this case just follow the directions and don't think about it.

When I do things... especially EFI.. there is only one way to do things.. the right way. This is a clear cut right way to do things, so why would you do it any other way?

PW proper... no.... works yes... here is why. Without the regulator hooked up and lowering the fuel pressure to maintain the same flow, the ecu has to trim out the extra fuel and really lower the numbers to get there. It sometimes can do this and sometimes cannot. There are several guys complaining about having engines that run too rich and the EZ will not tune it out. Most have found this when there was no vac line connected. If you read the CPG Nation board.. this is one of the basic settings people mess up.

I had a shop in your neck of the woods calling and calling me, since I was up there... had a EZ... one of Bobs... 10 different people whith o scopes looked at it and no one could get it to run... I went and reset the wizard.. went through the screens... hooked up the vac line and wow it runs without any black smoke. They were also told there was no need to hook up the line.. not true.

You understand what the regulator is actually doing? Correct?

The rear mounted regulators... yeah.. another problem there.. I had two burned up offroad cars because of that last year.

I wasn't speaking of the EZ. I've only done one of those, and it doesn't work for the combo (750 HP 494 Cammer Nascar twin throttle body engine). I made several changes to get the vacuum up, but being rich is not the issue...............

Again, we're just discussing your claim that the reference line must be used. I was speaking of all EFI, but even with the EZ Efi I'm not sure I agree. It's obvious many people have them running fine without it. Is it a good idea to help it self tune, apparently so. A "must"......... no. I have tuned too many EFI systems without it to agree.

It's all semantics. When you speak in absolutes you'll invite people to give examples that contradict what you're saying. If you said that the system is designed to have the reference line attached, and it helps the computer learn the tune much faster, I don't think that anyone would disagree with you. It's the absolutely "must have" wording that doesn't fly, because we have examples of that not being true.

I've done countless rear regulators without burning any of them up. GM does it on the late model Vettes and other cars. Of course they bump the fuel pressure in those, which I also do. There are several cars on this site that are tracked and street driven with the rear mounted regulators, either as a separate regulator (still bypassing, just doing it at the rear of the car) or using the GM Vette filters that regulate/bypass right from the filter.

Why won't this work? Well, it will, but curious why you think it's wrong. One of the main benefits is eliminating all that hot bypassed fuel from heating the tank and leaving you stuck on the side of the road (ask the dozens of Power Tour cars that experienced that from year to year how much fun it was).

Put an engine on the dyno sometime with 8 O2 sensors and play around with regulator placement and you will see why.

Even with running the regulator in the front and looping the rails can show as much as 1 AFR point from side to side.

What stops the fuel from just bypassing the fuel to the tank insead of going to the engine? It will follow the easiest path.

There are other ways to dealing with hot fuel than bypassing it in the back.

bypassing in the rear works for a low performance engine but when you start to get something that really needs fuel flow it will not work. You will end up with burned valves and or broken pistons.

So you agree how it works... but since I explained why it is the right way to do it... and since you can make it work the wrong way then... it's not necessary? Come on. I can make an engine run with the .008 piston to wall clearance... does that make it right? No.

Look at all the OEM pump engines that don't use PWM pumps and they all have vac referenced regulators... OEM changed to that in the early 90s.

It is an absolute. Must have and the right way. If you don't agree then you are saying the injectors should flow more fuel at part throttle.... and you already said that isn't the case. Besides how hard is it to hook up a vac line?

still don't get the bolded part. There's more than fuel pressure that affects how much fuel the injector sprays. Of course idle needs less fuel than wot or load areas. But you don't HAVE to lower the fuel pressure to accomplish that, you can change the pulse width. I'm not arguing which is "more correct" I'm simply saying it is not a "must" to run the reference line. If it was a "must" then eliminating would not allow the engine to function. That's how absolute a "must" is. Do you get what I'm trying to say? I can take a car you've tuned with the reference line and disconnect the line, re-tune the VE or fuel tables, and make it still run fine. I'm speaking of an end-user tunable system, though I ran Charleys car with EZ EFI both ways and it ran, started, and drove perfectly. The problem with that combo is learning harder throttle areas.

I've done a few 700-850+ rwhp cars with the regulator in the rear. Haven't broke one yet, and I'm not afraid to drive them hard. I had one that broke after I sold it, but that wasn't due to a rear regulator; that was nosing it over with an EFI tank that wasn't baffled well enough to work at 1/2 tank or lower with the acceleration of that particular car. Those were boost referenced though, so you'll be happy about that. :thumbsup:

My Cobra was n/a and had a front regulator, but still no reference line. Ran fantastic. All of these cars had O2 bungs on both sides and the sides were always within a couple tenths in A/F; nowhere near a full point difference. That was with comparing the computers wideband to the in-dash wideband gauge, to the handheld Innovate.

As far as fuel taking the path of least resistance, it seems like you'd see the pressure issues on a gauge. I have the gauge on the rail, and on the regulator, and I am not seeing any movement, fluctuation, or dropping pressure on mine.Seems like the regulator is working fine if the pressure is dead steady, a/f basically match side to side, and the car runs great. I do not doubt what you've seen, just that I do check and don't see it on mine. A/F differences from side to side can be due to heads, intakes, etc. as you know. Interesting that you've seen a difference with just moving a regulator. I've just been doing it a different way and my stuff runs good and doesn't blow up. And I never do a mild engine................ :lol:

Again, it's just the "must" wording that I cannot agree on.

Ok, if you still don't get it then lets look at the straw example.

This is the whole key... think of it as a straw that you blow through.. if you blow normal with no pressure or vac then you blow x amount of air. (WOT sea level 0 vac and 0 pressure)

If you have a suction on the other side and blow the same pressure then you actually get more air through the straw. (engine vac)

If there is someone blowing on the other side of the straw then you need to blow more pressure than they do to get the same amount of air out the other side. (boost)

So the way you are tuning is... there is actually more differential pressure at idle and cruise (more fuel flow)... then you lower the PW more than you should have to since the line is disconnected.... then you chase the fuel injector fuel flow change AND the VE air flow through the table while you are tuning.

This will get you in big trouble when you have say a 4.6 mod engine with 160# injectors that makes decient engine vac at part throttle. You can't lower the PW enough to make up for the extra flow the injectors are flowing....

It is a must and the correct way to do it PERIOD... if you say it isn't then you are just passing bad.. efi info around yet again.

It is the exact same reason you boost reference the regulator... and everyone does that.

Appreciating the dialog gentlemen, and learning a lot. Keep it up! :thumbsup:

Put 8 O2 sensors in the headers then tell me how constant they are, especially on a bank to bank EFI system. Moving the regulator from one at the end of the one rail to a setup with a y feed in and out made a huge difference. Two collectors are just an average of 4 cylinders each. You can have two really lean and two really rich and wouldn't even see it.

If you really think you will see pressure drop on a gage you are kidding yourself.. you lose fuel flow long before it actually hits the gage. By the time the gage actually moves you are OUT of fuel.

Brian --

I'm calling Brizio to have him hook up a vac line to the pressure regulator.... Well -- maybe not -- this is something I'd rather do myself. When the car was built - the line was run - just not used - so is a simple deal now. SMART HUH?!

Just 'cause the next time I see you (SEMA) I can say I did it right.... ">)


It all makes "sense" --- but on a little crate motor... I'm doubting it changes much... but then again -- I'm TOTALLY ready, willing, and able, to learn. You'll never hear me say that I know it all.

First off, your example of a 4.6 Ford with 160# injectors is not something that's seen every day. :lol: Yeah, with that large of an injector idle issues are a concern.

I have not had a single idle issue yet doing it my way. I've never had the pulsewidth go "too low" at idle and cause issues. I've never "chased" the tuning because of this.

You seem to take it personally that I have made it work well in a way different than you think it should be. You've given good advice, I see the purpose of referencing the regulator. But with a rear mounted regulator it's just one more line to run, plus I'm not sure there may not be an issue with the length of the line. Couldn't see an issue with the forced induction builds and the line length, but never tried on N/A.

I don't try to hand out bad info, I simply try to help with things that work for me. I have no problem with your view and would recommend people follow your advice, you're the pro. What I don't agree with is you keep saying that the reference line must be used. That's where you lose credibility. It's obvious that it isn't required or none of my cars or any of the other examples in this thread would run. I mean, they wouldn't even start up according to the "must" claim. That's my point.

I understand all that, was simply asking a question. You may not mean to but you come across as talking down to people if they question you, and for someone who instructs that's not good. Just some feedback, take it as you wish.

I'll stick with Jody's tuning. I know his works well.

Same here, I've seen numerous bad-as-sed cars come from Jody's hand. Plus, he's a righteously nice dude to boot. His cred here is well established.

Since this is clearly Brians meat an potatoes, I'm sure he knows what he's talking about. With that said, there is perfection and damn close. Engines don't require perfection to run well or cars likely wouldn't exist. I'm pretty certain my 850 holley isn't perfect. :D

I agree Todd. I'm positive he has much more experience and knowledge, and I appreciate his participation on the site. He gets paid for what he knows, and we get some of his knowledge for free, that's good for all of us.

We'll agree to disagree on the definition of "must". ;)

This is all I was talking about as well! :cheers:

Jody :thumbsup:

I have tuned 4 ~ 4.6 Fords this week that had that same combo. You are chasing the fuel curve weather you want to believe it or not.. that is fine. Take it personally... no not at all, you just don't seem to get it. One more line to run is no big deal... it's just cheap vac line... line length shouldn't matter.

It's not my credibility... it would be yours to keep arguing that it really does not matter. If you really understood what was happening you would say... I will always do it that way now that I understand. To tell people bad information that is does not matter or everyone here has always done it this way and it worked isn't a good argument.

I never said an engine wouldn't start.. or run... just not "right" most EZ EFI systems wont run very well at all. The real problem is where you try to lean out the idle down around the 1.2-1.4 ms of PW and you keep getting a rich condition you can't get out.

Like I said, you can machine an engine with .008 piston to wall clearance.. would it run.. sure.. but would you do that? No.. So if you now it is better and the proper way to run the regulator with the vac line then why wouldn’t you?

Lets face it the industry is full of people who see one thing and copy everyone else who is doing it that way. If the points leader uses brand X oil then it must be the best stuff out there. If this guy uses these gaskets then everyone should use that gasket. There is more bad info out there than there is good especially in the EFI world. My day usually consists of helping people tune their stuff after 5 other guys just took their money and gave them the tune out of the XFI folder. Part of why I have done well as a EFI tuner is I do a lot of dyno testing trying different stuff and have access to some really cool datalogging stuff most people don't even get to play with ever. I try to help out on a few boards and offer advise on what works and what does not. If I see something people don't get or understand then I try to help them in the right direction at least. This topic is something that I cover in every EFI101 class I teach and usually get blank stares from the students that say... wow everyone else does not do that. When I draw a picture on the board... most get it. There is lots of other stuff like, adding fuel stops detonation.... fuel is power... lots of stuff we debunk on the chassis dyno live at our classes.

Not taking anything personally and not talking down to anyone just trying to educate some bad info.

If I see you at SEMA the first beer is on me... you will see me at the FAST boost a lot after Wednesday. I will be up in your area the week before that working on a LS1 V12 with Motec.

Don't mean to at all. Typing can be taken very differently than what is meant. I am open for questions, that is why I keep answering.

ok, I understand you may tune (4) 4.6 Mod motors with 160# injectors on a regular basis, but come on............:lol: I doubt there's many here that run that size injector. Yes, I already said when you're dealing with something like that you can have idle issues and lowering the fuel pressure with the reference line would be beneficial. I also said that I was mostly talking about EFI in general, the systems that are end-user adjustable. However I tried with and without the reference line on the EZ EFI system and it adjusted for the difference in a few seconds, and after that ran exactly the same. As far as chasing the fuel curve, I start with a base fuel map with BS3, FAST, Accel, etc. that will need everything changed anyway. Even the ones that take engine info to build a base map are off a lot, some so far they won't even start and idle. Simple datalogging shows exactly where and how much you're off, and with some simple math you adjust the VE or fuel map numbers (or maf curve or? depending on the tuning system and EMC) and datalog again.

not true. You kept saying you "must" run the reference line. Even when I gave you the option to admit that "must" is not correct you clung to it. "Must" means there is no option, it will not work. That's why we've been going in circles here. But then you said if you disconnected the reference on an EZ EFI that it would have to learn the new fuel map which it does; so maybe it's not a "must". As I found out with the one I worked on it ran great at idle with or without that line. You also mentioned many tuners still don't use one; their cars must run I would assume.

I've been doing my own tuning since 1994 when I had a program to burn my own proms. I have done many N/A cars with and without reference lines. Not a single one had an idle issue or tuning issue. I have seen countless other cars in that period of time that didn't use one and ran fine. I am not challenging your knowledge. I can see why you want the reference line there. It makes sense to me and I'll start using them again on the N/A stuff. The only reason I didn't use them is because of the rear mounted regulators I use, and I was told by a tuner that the length of line would cause tuning issues. So thank you for telling me it won't. The only part that we disagreed on was that it is required on all EFI systems. If you would have said it's the best way to go and here's why, it can help with the EZ EFI if you have a fat idle and can't get rid of it, or if you're dealing with a large injector and having idle issues this can help we would have had no disagreement.

My only point was on the "must" part of what you were saying. Hopefully you get what I'm saying, because I really can't explain it any better. Thanks again for your time and info, it is appreciated.

I say "Must" because it is the right way to do it for no other reason. I still think even after all the posts you still don't get it. It's not lowering the pressure but more the reason is the pressure differential between the intake and injector remain the same, no matter if you are in boost, vac or no vac.

Do you get that part?

Then the ecu just tunes the actual fuel curve and not the fuel curve and the pressure differential too. This gives the ecu a better ability to tune at the lower PW for any injector size.

If line length was an issue then your rear mounted regulator wouldn't work under boost. The long line will make the change slower but it will still work just the same.

I get it and I give up.............. :faint: :lol:

:faint: :lolhit: :beathorse :clap:

Go Steelers! How's that for agreeable Jody?