Wtf?

[Bill Blue]

Bill,

How can you say what the unpredictable pressure variation is?
If you are seeing 1.5psi static error, the error is going to be at least that since the pumping variation and fluid viscosity changes will only make it worse at lower temps. The back pressure will also drop as the gasoline heats up.

The back pressure will be cross-sectional area an length dependent barring kinks and bad bends.

The pressure is going to be low (by EFI standards) so it doesnt much matter what the material is so long as it is compatible with the fuel.

Thinwall stainless is often used, I've seen thinwall aluminum too but I would worry about corrosion with all the ethanol they are putting in the fuel.

EDIT:
Looked back at the thread and saw that Bill was seeing 1.5psi static error not 1.75.
Even still that is a huge back pressure compared to what it should be.

I can't tell what the unpredictable will be. That's why I qualified my numbers to the observed data, which is quite limited and more observation is required. Those observations indicated that most of the variation in pressure is predictable.

I thought the idea of the pressure gauge was to determine the as yet unknown pressure variation, both predictable and non-predictable.

I am not familiar with the term "static error". What does that mean?

Bill

 

[RootesRacer]

I can't tell what the unpredictable will be. That's why I qualified my numbers to the observed data, which is quite limited and more observation is required. Those observations indicated that most of the variation in pressure is predictable.

I thought the idea of the pressure gauge was to determine the as yet unknown pressure variation, both predictable and non-predictable.

I am not familiar with the term "static error". What does that mean?

Bill

Static error would be that the regulator dump outlet pressure should be 0psi and you were seeing 1.5psi with the engine at light load or not running.
Static pressure would best describe the pressure you see when the pump pressure is regulated and returning all its flow to the tank.

That (dump port) pressure will be proportional to pump flow minus engine usage.
Since pump flow is going to vary quite a bit, that pressure is going to vary quite a bit too.

The reason you want to get the pressure as close as possible to 0 psi is because of how the regulator functions. That is that any pressure seen at the dump port will increase the rails regulation pressure 1 to 1.
If the back pressure were always 1.5psi and never changed due to load, temp, pump functionality or gasoline constituency then you could map around the issue. Unfortunately this is NOT the case.

An FYI would be that people who setup race cars and build out the fuel systems will typically use a 6AN (3/8 line) for a small engines, 8AN for larger and 10AN for higher outputs. It all depends on the pump capacity at the regulated pressure.

 

[RootesRacer]

Oh and the purpose of the pressure gauge in this case was to show you that you have a problem you should be concerned with, not to ascertain the predictability of the problem. Understanding the mechanics of the regulator and the physics of why the pressure would vary is what tells you that having that level of problem is something you cant ignore.

 

[Bill Blue]

Received the wire terminals yesterday afternoon, got the jumper installed last night, started it up this morning.

Huge difference. Idle was very smooth with very little rpm change, even when cold. After warm up, idle pulse width and Lambdas were very consistent. When cold, they were consistent, but ever changing as the engine warmed up, as one would expect. Once up to temperature, it responded to minor tuning changes in a predictable manner, which it never has. I tweeked the idle and tip in performance, but have yet to take it for a drive. Probably will put 100 miles on it this afternoon.

There is hope.

Bill

 

[RootesRacer]

Bill, are you running the modified map I sent you?

There may be no telling what all is in the ECU now if you didnt finish up the map download you started last week.

 

[Bill Blue]

Bill, are you running the modified map I sent you?

There may be no telling what all is in the ECU now if you didnt finish up the map download you started last week.

None of the parameters downloaded. They were all as I sent you. I manually changed them to the numbers in the 034 manual as they matched the changes you described. They appear to work pretty well. Cold start up is sort of rich, but okay for now.

Took a quick spin into town, about a 5 mile round trip with a 10 minute shutdown. The cruise tune is different than before (leaner), but it ran the same both ways! Plan to do some serious tuning this evening, then we'll see how it holds. Right now, I'm optimistic.

Bill

 

[RootesRacer]

None of the parameters downloaded. They were all as I sent you.
Bill

No, this is not the case.
There were a bunch of parameters sent before it hit that variable that got clobbered by your email.

I havent actually looked though the map to see how many of the parameters got through but be assured that some did.

So you arent planning to try the map I sent you?
I think it would be prudent to eliminate sources of grief and running a while before claiming victory.

Also just because you see examples of parameters in the tuning manual, doesnt make it right or applicable to your engine.

 

[Bill Blue]

No, this is not the case.
There were a bunch of parameters sent before it hit that variable that got clobbered by your email.

I havent actually looked though the map to see how many of the parameters got through but be assured that some did.

So you arent planning to try the map I sent you?
I think it would be prudent to eliminate sources of grief and running a while before claiming victory.

Also just because you see examples of parameters in the tuning manual, doesnt make it right or applicable to your engine.

The only compensation that is turned off is the Baro Ignition Advance. By turned off, I assume you mean zeros.

The parameters I took from the tuning manual are more conservative and smoother than mine, so I figured at worst, they would be okay. Mostly temp and baro compensations.

I fixed the -16 degrees in the MAP Ign Advance.

Fixed the VBat and MAP Dwell multipliers.

It way my understanding that most of your changes were designed to trouble shoot the tune. Before doing that, I want to determine the impact of the jumper. So I guess my answer is if, after a week, I'm happy with the stability of the tune, I'll forgo installing your tune. If not, in it goes.

No victory is, or has been, claimed. That is at least a week away. Perhaps I'm just foolishly optimistic.

Bill

 

[RootesRacer]

Be sure to set the baro fuel multiplier to all 1.00s.

The examples that 034 uses will not be appropriate for your engine.

Speed density by definition automatically compensates for baro change by virtue of its reliance on the manifold pressure (which will track baro 1/1).

You only want baro fuel compensation when using other than MAP for load calcs, or when you want a dialed in baro based fuel error.

Same goes with the ignition.

 

[Bill Blue]

"Be sure to set the baro fuel multiplier to all 1.00s".
Can't find "Baro Fuel Multiplier" Is it also called "Baro Compensator"? It has never been all 1's, but I can make it happen.

Bill

 

[RootesRacer]

"Be sure to set the baro fuel multiplier to all 1.00s".
Can't find "Baro Fuel Multiplier" Is it also called "Baro Compensator"? It has never been all 1's, but I can make it happen.

Bill

Yes.

It was all ones in the map I rebuilt for you.

 

[Bill Blue]

Air?

The jumper helped, most noticeable at idle. The injector pulse widths became more consistent, enough so that I was able to see there was not a very good correlation between PW and Lambdas. So I decided to check out the return fuel flow situation.

Purchased 12 ft of 1/4" I.D. vinyl tubing and tee'd it into the return line, returning directly to the gas tank filler, so that it has two 1/4" return lines. First think I noticed, the vinyl hose is full of bubbles. A fine stream of bubbles that coalesce into large bubbles, not disappear as one would expect if they were vapor bubbles. I can't imagine that air bubbles are normal. Problem: I can't get rid of the damn things. In fact, nothing that I have done seems to have had much effect.

The car is a Series V. I'm using the stock fuel pickup. Currently there is a single 5/16" I.D. fuel injection hose running between the fuel outlet and the high pressure pump. I can see no way it is leaking. Is it possible the pump is leaking air?

Bill

 

[Ken Ellis]

Can you put a section of clear in the main pump outlet circuit temporarily? To find out if the bubbles are coming right out of the pump, before the injector plumbing? Jim Stone was having bubbles in his standard 1725 pump... I wonder if they are "normal" after the pumping action, due to cavitation (?) or some other hydrophenomenon...

 

[RootesRacer]

Bubbles are not normal.
Sounds like you are sucking air from somewhere on the low pressure side.

You might try sucking from a suitable sized gas gas (return to the can) and see if its your tank pickup.

 

[Bill Blue]

Bubbles are not normal.
Sounds like you are sucking air from somewhere on the low pressure side.

You might try sucking from a suitable sized gas gas (return to the can) and see if its your tank pickup.

Yeah, that's about all that's left, but I hadn't thought of the proper test. Just got through swapping pumps and different plumbing bits. That makes the chief suspect the fitting welded into the crossover pipe.

Ken, any opening beyond the pump would result in a fuel leak as there is 43 psi present. At first I thought the bubbles were fuel vapor (same thoughts you are having), but if they were, they should disappear.

Bill

 

[Bill Blue]

We still get a copious amount of fine bubbles, but they seem to disappear, rather than accumulate. Looks like the crossover tube is coming out.

It makes sense that is the problem: it explains the constant gas odor in the trunk and the problems I had tuning the Weber on the Pinto.

Bill

 

[RootesRacer]

We still get a copious amount of fine bubbles, but they seem to disappear, rather than accumulate. Looks like the crossover tube is coming out.

It makes sense that is the problem: it explains the constant gas odor in the trunk and the problems I had tuning the Weber on the Pinto.

Bill

Doesnt explain the weber issue with the pinto.

You can have air bubbles in the fuel with a carb, they go away when the fuel hits the bowl.

EFI on the other hand doesnt much like air in the fuel.

 

[Bill Blue]

Rejiggered the transition from tank outlet to gas line. I was surprised to find that it was not 5/16" compression, just as I was surprised years ago when I took 5/16" compression off the original gas line. The threads on the outlet are 1/2"-20, straight thread. 5/16" compression fittings are 1/2"-24, a real oddball size in the machine shop.

The fine bubbles remain, but they seem to disappear. Before, upon shutdown, I had a 6" long air bubble in the vinyl return line. It is now about an inch. Vapor bubbles created by the turbulence and pressure drop at the pressure regulator?

Will just have to see how it runs on the road.

Bill

 

[Ken Ellis]

To my understanding, there are two sizes of British Standard Pipe Thread, Straight, with 19 threads per inch, and one of them has a major diameter of .518 inches. The first time I encountered this was in a conversation with Doug Jennings. The item in question was a Tiger electric fuel pump.

He noted that 1/2"-20 would probably fit, but it would leak air and gas a little.

I have personally not been into that particular area of the fuel system, but the comments triggered my memory on the topic... But I'll admit I've been wrong before.

http://en.wikipedia.org/wiki/British_standard_pipe_thread#Pipe_thread_sizes

 

[Bill Blue]

Ken, I have to admit I did not measure the thread directly. I came up with the 20 tpi by comparing it to a 1/2-20 tap and it looked like an exact match. But that was under less than optimum conditions.

The thread in question is male, there is no way a .500 nut will thread on a .518 diameter pipe. That said, I have no idea what the setup is. I happened to find a two piece barb fitting that was designed to fit onto a threaded pipe with a tapered seat to seal against the pipe. The Alpine fuel outlet pipe looks like it uses a tapered seal and the nut that was part of the barb fitting threaded on beautifully. I don't even remember where I got the two piece barb fitting.

"Nothing - I know nothing"

Bill