Well guys went out to the car to try something so i lowered the esm voltage down from 2.80 to 2.70 and something interesting happened at wot the fuel pressure stayed at 100!!!!!!!!!!! what the hell is going on no more drop in pressure so i wonder if i lower it more it should stay above 100psi through the range.any thoughts guys why the pressure is now staying at 100psi?before it went down to 90psi and now it doesnt move down at all.

 

I don't know much about the ESM, but a few weeks ago I kept an eagle eye on the FP gauge during some WOT highway runs and my FP did drop at the high rpms. It never went below 100 psi, but I could see it drop from the pegged position down to 100.

Do you measure the voltage with the car running, and where do you measure it at?

 

you measure it at the esm it has 2ports to insert + -

 

Re: eric
Eric ,
Interesting but coincidental somethhing else is going on here .Your fuel pump runs at one speed it is not a variable unit and the fuel pressure regulator is vacuum operated not electrical in any way .SO I fail to see how changing the ESM is affecting the fuel pressure .ALtering the ESM voltage is not wise as you are telling the PCM that you are not at full throttle even though you really are .
Jens thanx jens for the info i guess ill put it back

 

It is actually pretty simple.

The fuel pump will only flow so much fuel at so much pressure. The reason the pressure drops is that as the revs climb the duty cycle increases (the amount of on-time) but the pump cannot supply the flow at the set pressure.

By lowering the ESM voltage the ECU reads a lower MAP signal; it reads more vacuum. Since the MAP signal constitutes about 50% of the load calculation (estimated) a drop in this signal will cause a lower load value to be calculated. This will then command a smaller pulse width. A lower pulse width is a lower duty cycle and would amount to less fuel consumed.

With less fuel being consumed there is more fuel remaining in the lines. This means that the pressure can remain more constant as less if being "bled" off.

But this doesn't mean that you are getting more fuel. The injectors are not opening as long but more pressure is behind them. It might just be a wash up top. However, it might be helping the bottom end though as it would probably help to lean it out a little since there probably isn't a flow limitation down low.

 

Car running?

 

key in full on but car not running

 

so steve what your saying it doesnt do any good so put it back to 2.8volts?since i might be leaning it too much

 

I'll try to illustrate this point; the values used are somewhat hypothetical but should fill in the blanks:

Let’s take 6000 RPM with an ESM setting at 2.9 VDC. This 2.9 VDC would provide a vacuum reading to the ESM of about 29.5 inHg. Let's say that the ECU will determine 100% load calculation which translates to a pulse width of 15ms.

A pulse width of 15ms at 6000 RPM is a duty cycle of 75%. Let’s say the pump can only support 95 PSI at a duty cycle of 75% with the stock sized injectors.

Now the ESM is turned down to 2.7 VDC which gives a vacuum reading of about 28 inHg (again, just a guess but I will confirm this). This is about a 5% change in vacuum. Without knowing the actual fuel mapping in the ECU I will assume a somewhat linear relationship. This would in turn adjust the pulse width down by about 5%; or 14.25ms. This is a duty cycle of 71.25% at 6000 RPM.

So there is less flow demand on the pump so it is now able to support more pressure. This pressure increase would be of about the same ratio so that 95 PSI might now be 99.75 PSI.

I had hypothesized this but it is nice to see it is confirmed. I'll try it out too and report back with the results.

But Jens is correct in that at some point the ECU will not think you are WOT. What it does with fueling timing and ignition timing when not at WOT might impact us negatively. But without testing we will not know for sure. But I do feel a range of about -10% would be within reason as the MAP is an absolute pressure transducer. In other words it will see a lower output at elevation and I am sure they adjusted for this. Plus, my experience with other ECUs suggests that any throttle input over 75% is considered WOT to most of the ECU mappings.

But we'll need to test this further to glean the complete aspects.

 

Yup I was going to go to go there as well Scalbert with the duty cycle of injectors etc etc but I think this car of Eric's has other issues I can only guess at .

Jens

 

hey jens my car has no issues it runs awesome just tweaking a little.no pinging whatsoever since i pulled the imrc it runs much better and smoother all the way to redline as jens said their is no need for the imrc on a blown car and does not affect my performance at all!!!!!!!!!!!!!!its been disconnected for 2months now and love the smooth power delivery without the imrc

 

Well ok then if it is running good why are you fiddling with the ESM yet again? BAD BOY stop playin with yer knob boy .LOL just kidding glad to hear it's running well .
Jens

 

im going to see you soon at paa

 

Leave the knob at home LOL

Jens

 

jens you biatch lol

 

Anybody check to see if lowering the ESM voltage is the way to keep fuel pressure from dropping or is this a bad idea.
Tool462's fuel pressure is dropping as well and wants to know if he should try this.
Please advise.

 

It will, but read above!!!!.... your asking for detonation problems by leaning the car out....

Rest assured that issue is still being addressed.... I dunno if the unichip will have any affect on it, but we shall see...

I for one am not losing any pressure in the higher rev band.

 

His car is detenating at high RPM's already, so this seems to be a bad idea in his case.
The chip has been coming for two years, so We'll believe it when we see it.

 

Read above... It will tell you the whys and hows...

 

Well if fuel is what we are after here the solution comes in the form of a fuel pump that swing with this .On virtually all of the NOS kits there is usually a secondary pump to keep up with fuel demand .As Scalbert pointed out the problem here is basically the pump (even the upgrade ones) can only flow so much fuel .So the next step for real fuel junkies is ofcourse a secondary pump the reinforce the primary .Bosch makes a great big fat pump that I installed many years ago on NOS systems .The bastard sounds like a berserk Hoover under the car but fuel pressure was never an issue in fact often times I wondered if perhaps the fuel rails would simply explode .Anyway perhaps a call to NOS systems is on order to determine what they supply on their heavy hitting 100 plus shot systems .

Jens

 

So I assume you were running the pump in series??

I was thinking about pulling the current pump assembly and seeing if I can come up with a way to run the another of the same pump in parrallel. That should be more than enough fuel for our needs.

 

Also, the issue with the voltage drop needs to be addressed as this will be enough to give 10% - 15% more fuel from the current set up. I plan on having this done by the time the IC is on the car.

 

Yeah we ran the the big Bosch pumps inline after the main in tank pump .If you ran out of fuel with that thing hanging under the car you had other issues .
Jens

 

Maybe the stock pump and the one with our S/C kit in series?

 

Not the correct style; both are in tank pumps.

 

There is not a lot of room in the tank anyway .Better to just a hang an add on pump underneath the car .Only thing that will make it a pain are the hard plastic fuel lines .

Jens

 

So this pump is run in series with the our oem pump (or the upgraded Comptech pump)? Would this help? I am getting the supercharger installed next week so if this would be a good thing to do I'd like to do it now. Opinions please (and the model number of the Bosch pump )
Is ther such thing as too much fuel pressure? TIA!

 

You would be the first to do it Topgum... It is used with the Wilboro pump that comes with the S/C'er kit.

 

Any comments on the following? How much pressure does the Walboro pump supply? I would think Comptech would provide a pump beefy enough for demand. Maybe it is the voltage supplied to it is insufficient like you guys where researching? Is the S/C FPR a front or rear pressure regulator?

Calculating Fuel Requirements


Determining how much fuel your fuel pump needs to be able to provide is no mystery. It's simple mathematics. The engine in your car takes in air and fuel and converts them to horsepower. The amount of horsepower your engine can make is a function of things like the size of the engine, the compression ratio, the boost (in turbo/super-charged applications) and several other variables. To make this horsepower, your engine will consume a certain amount of fuel. That amount is referred to as the "Brake Specific Fuel Consumption", or BSFC. The BSFC is generally estimated to be between 0.45 and 0.50 for most naturally-aspirated (non-turbo/super-charged) engines, and between .55 and .60 for turbo/super-charged engines.

By way of an example, let's say that you have a naturally aspirated car that makes approximately 200 HP. Using the more conservative BSFC of 0.50, your engine requires approximately 100 pounds of fuel per hour. Now, fuel pumps are typically rated in flow of volume over time and not weight over time, and so we convert this to an international-standard of 63 liters per hour by dividing by 1.58. For a turbocharged engine that makes 300 HP, we use a BSFC of 0.60 to come up with 114 liters per hour.

It is critical that the fuel pump in your fuel-injected vehicle is able to produce at least as much or more volume over time than the engine requires. If the fuel pump is unable to meet the fuel requirements then the fuel mixture will become lean and the engine will go into pre-detonation and will eventually destroy itself. Unfortunately, many stock fuel pumps are capable of providing enough fuel for only the capabilities of the engine as designed and installed by the manufacturer. Users who seek higher horsepower output from their vehicles increase fuel requirements. The stock fuel pump often becomes dangerously inadequate to provide fuel to the heavily modified engine. Since additional flow above engine requirements will simply be returned to the fuel tank, too much flow is a far better thing that too little.





How is Fuel Pressure Regulated?


Just as there are different fuel pumps for low pressure (carburetor) and high pressure (fuel injector) fuel systems, there are different ways to regulate the pressure of these pumps. most low-pressure systems use a front-pressure regulator.

This system uses a simple spring-pressure to increase or decrease the pressure of the fuel coming from the fuel pump. high pressure systems, on the other hand, are almost exclusively back-pressure regulated. that means the regulator is located after the fuel injectors and allows enough fuel to flow back to the tank to maintain the required pressure.

High pressure systems therefore require that the fuel pump is able to provide more pressure and flow than is actually needed by the fuel injectors so that effective regulation can be enabled. When the vehicle is making little horsepower (such as when it is at idle) the fuel pressure regulator is returning large quantities of fuel back to the fuel tank to keep the fuel pressure from spiking about what is required. when at maximum horsepower output, a smaller amount of fuel is being returned since more is being used by the engine to make power.





"High pressure" vs. "Standard pressure"


Walbro makes the same fuel pumps (as far as mechanical fitment is concerned) in two different styles. These styles are normally referred to as standard pressure and high pressure. This reference is a bit of a misnomer, since either pump will produce approximately the same amount of flow at standard fuel injection system pressures. However, well above the standard fuel injection system pressure the flow of the standard pressure fuel pump will drop off whereas the flow of the high-pressure fuel pump will see less impact. This is important to users who are trying to use higher fuel pressures to push more fuel through their fuel injectors than is normally done at standard fuel pressure levels. While this may be a cost-effective solution it can lead to other concerns, including safety considerations. Fuel-Pumps.net recommends that you use an injector that is able to inject the proper amount of fuel into the engine without requiring the fuel system's pressure to be increased significantly above stock levels.

 

The pump is more than fine for the kit as provided by Comptech, we are just planning ahead. However, doing away with the voltage drop won't hurt either.

The problem IMO is that we are trying to run too much pressure with the higher boost pulley. The pump is strong enough but can only support so much pressure at a certain flow rate. If we were running 70 PSI at WOT but had increased the pulse width we would be fine. This is just too much pressure to support at the higher flow rates.

So instead of changing or adding a pump lets first get the voltage level where it should be. This would be more than enough for use with the higher boost pulley alone. If after the IC and/or more boost is run and there is a problem, then a supplemental pump can be installed.

But if the need does come up; when run in series, always have the stronger one second. But this does not provide total fuel supply equal to the sum of each pump; it is about 120% - 130% of the stronger pump. When run in parallel the volume potential is equal to the sum of each pump.

 

Yes, the injectors are not rated for very high pressure. As the pressure is consitently high it weakens the injector since it is harder for it to open. Also, if pressure is too high it can lock the injector open during WOT.

I think we are safe right now but we really need a way to control the pulse width.

 

Yea, not fun but not too terribly bad with the correct adapters. That or just replace it with larger metal lines...

 

 

Scalbert,I have not really looked but is there a significant voltage to the pump?If so how much?

Jens

 

I was reading only 12.8 - 12.9 VDC at the pump. This is with a system voltage running at about 14.3 VDC, right where it should be. When I unhooked the pump the stock power feed jumped up to 14.3 VDC so there is a noticeable voltage drop in the circuit. I normally go by the idea that 0.1 VDC drop is too much and we are 10 fold greater than this.

I ran a test where I used the feed for my Pioneer amp to the fuel pump. This gave me about 13.9 VDC which raised the base pressure about 4 - 5 PSI and about 7 - 8 PSI at WOT.

 

If I get chance i will look at a few cars to see what sort of voltage we are running back here .I remeber I saw a gadget once that ran the stock fuel pumps at a higher voltage to get moire performance out of them .For the life of me I cannot remember the name of the damn thing but if I do I will post it .Might be worth checking out .

Jens

 

Kenne Bell has a Boost-a-Pump unit which increases voltage to a pump.

http://www.kennebell.net/accessories...boostapump.htm

However, the drop should first be addressed as this appears to be an issue of undersized wiring for the current requirement. But aftre the wiring is corrected then this might be the next step.

 

DId you check the fuel pressure on the car when it was stock? I doubt Acura would build it with intentionally thin wiring .I wonder what difference in pressure there is at stock (no boost levels) .

Jens

 

No, I didn't check the pressure stock nor would they design the car with too small of wiring. I suspect there was a drop with the stock pump. But they do normally size it just large enough for the stock needs.

However, since this new pump probably pulls more 150% more current than the stock pump the wiring may now not be completely up to the task for what we will want.

 

Ok sounds good to me .I would use the existing wiring to operate a relay .Then run some serious grade cabling to run the pump itself .

Jens