GoRideSno

Tim,
Are you saying that you are an engineer?
Andy

worf928

O&N and JimB beat me to it.

Andy, I won't say that fatter rails are not bad. But, if they are bad, surely it cannot be for the reason you write above? We are not talking about a constant mass of gas at steady-state that obeys PV=nRT inside a rail that changes its volume dynamically.

Sure, it takes longer to build the pressure from zero to the desired pressure because more fluid mass is required by the larger plenum and the mass flow rate from the pump is more-or-less constant. But, once at the desired pressure it is a matter of mass entering vs. mass exiting.

TM mentioned 'tip-in detonation.' My question was directed solely at that concern; I don't want to confuse the issue by considering high-flow-rate but steady-state conditions - i.e. throttle mashed to the floor for a long time. TM didn't indicate that he previously blew gaskets due to tip-in detonation.

To the latter - sure. You need to be able to raise the pressure - fast - because by the time a vacuum-actuated pressure regulation system can react to go-pedal movement you are already too late. So, if you can find a FPR that reacts faster, then by all means...

I don't buy the lower pressure argument on rail volume size though.

It may very well be that the plenum volume required to make a useful difference in managing a transient fuel pressure gradient is so great as to be impractical.

Carl Fausett

Woah! Great thread - but that last comment just ain't right. And the Ford Lightening rails? The reason that the rail diameter to each injector is the same size as the fuel line from the tank to the engine is... the firing order. Only one injector is open at a time. Only one injector fires at a time.

Conversely - although Porsche made the individual injector lines on the CIS cars so little - they got bye with that because they shoot continuously.
Funny how you 32v guys are swapping fuel pumps and increasing line sizes.... very, very much down the same road I am going with my track car (read: EXPERIMENTAL CAR). Our 16v Stage 1 and 2 kits have enough fuel, but the race car - I am trying to find more fuel for it as I turn up the boost.

Here's a picture of those larger fuel lines - they helped - but I think I have a "maximum flow potential" problem stemming from the ***-end of the car that I am trying to work on now.

GoRideSno

Carl,
I am glad you know more than RC Engineering which is probably one of the premier FI shops in the country. EDIT: I went to their site and they claim to be the best in the world.

The Lightning rail is NOT the same size as the line to EACH injector. ALL injectors share the same rail and that rail is NO bigger than the fuel supply line in our cars. Can you not see that in the picture? END EDIT

Regardless of the firing order of the Lightning injectors, the same amount of fuel has to flow to make the same amount of power.

Maybe you could answer this. Why is it that the curves on Tim's last dyno chart posted cross at 5750 instead of 5250?

Thx,
Andy

Z

Maybe it's just me, but this sure seems like a good thread for anybody planning on supercharging their car to pay close attention to what's been said.

Tim:
And you guys wonder why I don't follow this stuff or post anymore?

Carl:
You make everyone think that you're a CIS guy, and then you make a post like that stating one of the differences between sequential and batch fire EFI?

Jim:
I don't want to tell you how to do your job, but it might not be a bad idea to check your piston inventory. No matter who's right, it seems like you may very come out a winner. $$$$

Andy:
Because the charts horsepower and torque scales are different. The curves only cross at 5,250 RPM if the horsepower and torque scales are the same. You can make the curves cross at any RPM point you want, or never cross at all, if you adjust the scaling of the individual charts in the dyno software. Neither the horsepower or torque numbers change at all at any one RPM point, just the height of the curve on the fixed height chart in relation to the other curve with the different scale set to it. Depending on what data you want plotted on the same chart, you may want different scaling. You can have the software set to "Auto Scale", "Force Scaling" which makes both scales the same, or manually adjust the scales to whatever range you want. The dyno software was apparently set to "Auto Scale when Tim's chart was printed. Most of the time the dyno operators seem to leave the software set to "Force Scaling", so that those not as familiar with dynos and dyno charts aren't so easily confused.

Well, download complete so...

mspiegle

But if the equation is:

T = (5252 x HP) / RPM

At any point in time, if RPM = 5252, then it will cancel out the 5252 on top, and you are left with T = HP. That is why T and HP cross @ 5252 - because they are equal.

Are you saying that this equation is wrong?

Carl Fausett

Andy: just semantics - what I meant was "the rail is the same size as the line from the tank" I think you and I are saying the same thing.

I kinda like Jim Baileys observation about the CIS cars having a pressure accumulator and the EFI cars not - as he says, it holds about 1/2 cup of fuel under system pressure to release so there is no system "make up" lag under sudden WOT. Interesting...

About this whole volume vs. pressure conversation: a common trick engineers will use in fluid systems when it all gets too confusing is to convert the equations as if it was electricity. Use Volts (pressure) Amps (volume) and Ohms (resistance) - in almost every way, the elctrical analogy is a perfect match and will behave the same as fluids.

Can two wires - a big one and a small one - carry the same volts, but have different amp capacities? Of course.

Will the smaller wire resist a drop in voltage when the "juice" is on better than the bigger wire? Hell no.

Does this help?

John..

We need a computational fluid dynamics program to really figure this one out. It is really all about mass off fluid flow, isn't it? If the pump can keep the rail fed and the lines are adequate to support that mass flow of fluid, then all will be fine. The injector needs the fuel pressure to maintain flow and the lines and pump have to be large enough to deliver that flow. I don't think this can be analyzed by looking just at the size of the lines, as the pump is an integral part of the entire system.

You could all just drop the fuel pressure down and go with a much bigger injector. Your pump and injectors will be much happier in the end!

The 5252 comes directly from the fact that there are 550ft-lbf/second in one HP and the fact that there are 2pi radians in one revolution and 60 seconds in one minute. 550/(2*3.14/60)=5252. It is a unit conversion. Perhaps we all need to start plotting in Newtom Meters and KW? In the end the highest torque across the entire range will build the most HP across the board. I'll take the setup with the higher torque across the entire RPM range any day over higher peak HP with less "average" torque.

And the boost wars continue...

Z

The equation is correct. Your statement is wrong. T and HP ARE equal at 5250, but the curves do NOT cross at 5250 RPM UNLESS the scales for both are the same. Here's an old chart of Tim's where the curves don't ever cross at all because of the different horsepower and torque scales used when it was printed. Notice that at the 5,250 RPM cursor HP=Torque, but the curves are nowhere near each other because of the different scales for each. Go ahead and try the values from any points on the chart in the formula, but make sure that you use the left scale for the horsepower number, and the right scale for the torque number.

GoRideSno

Welcome back Z. It's good to see you. Every time you show up someone buys a kit from me. Come around more often and maybe I'll get this on rennlist , by rennlister, for rennlisters venture paid for one day. I guess it would be smart to commission you as I would pay it off faster. I don't think a bank would cash a check made out to someone named Z though. Who should I make the check out to? I guess I'll need to pay your Rennlist membership too. You would have to give up your name for that though.

Andy K

Tim Murphy

So Andy, with all these supercharger kits that you have been selling we are all wondering when we will actually hear about someone getting one installed. I am only aware of one person on the list that was installing your "kit" and that person stopped reporting his progress over a month ago. You claim to have sold more than twice as many kits as I have and I am wondering why we haven't heard of any results yet or testimonials from any of your customers. Maybe they are just a quiet group like the FAST guys perhaps?

Z

I'm not exactly back. Someone mentioned this thead to me and said I ought to take a look, so I did since I had nothing else to do while downloading some stuff.

As long as I get that commision on kits that are sold, and not just on ones that are installed kits.

Tony

Guys....Guys....

Go to your nuetral corners!!

bcdavis

It was bound to happen...

Obviously, the MURF kit is complete, with full instructions, testimonials, and dyno results.

Andy's kit is more of a do-it-yourself thing.
It is probably taking people longer, because of that fact.
They have to source parts, get things figured out, etc...
With the MURF setup, you just bolt it all on, and go...
But you pay for that...

People are willing to wait for Andy's parts, and wait for the instruction manual, etc, because they are saving quite a bit of money...

John..

It is still nice to be the black sheep...uh I mean Gold sheep.