Fuel Pressure Regulator lag. A15 SOHC

[Richieb]

I have been studying the engine set-up, and noted that the FPR on the fuel rail is controlled by the engine vaccuum from the end of the inlet manifold on the A15 SOHC engine.

This vaccuum pulls the Fuel pressure regulator to low pressure fuelling at idle and over-run. (some enviro experiment for GM/Delco).

This means the injectors are not getting the full pressure/flow when you snap the throttle open!!, and there will be a lag in the time the vaccuum takes to collapse, which means of course, that the fuelling takes a moment to come up to fuel pressure/flow for the engine to get a big feed of fuel and air.... kind of like the old Carby type of problem when the accellerator pump was not set-up correctly.... it just needed a split second or so to get itself together.

Now we probably know that the Lanos 1.5 was slow on the start from a standstill, which was one of the coments from the "Car Journalists" about the vehicle, hence the 1/4mile was slow by numbers... but we all know when it gets moving, it does pick itself up, and goes quite well.

I feel that the "Off-the_mark" time/response will be better if the fuelling is more predictable. The trim of the fuel will not be affected by the ECU, as it is in closed loop idle, and it cannot monitor the O2 in the exhaust, as it runs too cool for the O2 sensor to operate at this engine speed.

I am going to put a regulator in its place which will hold the fuel at 43.5PSi at the injectors at idle, or perhaps more. I will have an experiment.

Its not an increase the pressure at the injectors type of mod, as we all know this can damage the seal in the tip of them. They are designed to run at this pressure, which is what they are rated at, although 70 PSi for good injectors is the max I would take them to, as they then struggle to meter fuel correctly.

I work with performance engines, and one of the ways to increase fuelling is to increase the pressure at the injectors once the engine is under load, so my guess is, that apply this to the Lanos engine, or in fact any other that will respond to a fraction more fuel, and it should clear out that familiar slight hesitation we all feel with the car.

I have an adapter, which will fit on to the rail, and am going to use a Malpassi RRFPR(two stage model), without the pressure feed being used(this is for the pressure side when used in force inducted engines only), as I know these to be good responsive FPR's. Pressure I will set to the prescribed 43PSi, and see how well the theory comes to practice. THEN.. I will see how well it benefits by a few extra PSi as far as that slight hesitation when opening the throttle from normal road speeds.

Theory is that when the throttle is part open, a vaccuum exists in the manifold as we drive it, and once again, the time taken for the vaccuum to collapse equates to the slight hesitation effect.

Will post the results in next 4-5 days.

[PrecisionBoost]

It would be interesting to see your results, if you have a wideband you could throw into they system that would help show what's happening.

One thing to consider is the timing advance, a hesitation could easily be explained by poor software algorithms in the ECU.

[Richieb]

That's what I was thinking.

I have an LM2, which I have to figure out how to put this in before the cat as yet..!!

I feel the ECU has been seriously pulled right back to eco friendly mode, so the plan is to just force its hand a little.

I have 3 of the MAP sensors in the garage, and all exhibit the same hesitation, which quite rightly could, and do affect its timing adv.

One thing that passed through my mind was flow from the pump, and is there a chance the fuel lines are restricted in any way. Pressure will still be high at low volumes, but as the demand for fuel is bumped at demand, it could starve it slightly, and pressure will drop momentarily in-line with the flow.

The only thing I cant get to test with an on the run scenario is this.

The one thing I shall do is to extend the Pressure gauge into the cabin to observe is behaviour. This combined with the LM2's info should tell quite a bit about the conditions.

[RichieOzzie]

Well, here I go.

I installed the Malpassi from the end/exit of the fuel rail with an adapter, and set the gauge to +/- 45psi.

Fired the car, and watched the gauge, and fine tuned it to compensate for any system voltage drop as it runs at idle.

I just blocked the vacuum feed at the manifold end, and vented the Malpassi to air via a bit of foam and ty-wrap.

The car has now improved dramatically at mid-range. The torque to pull the gears is 100% noticeable, even via the seat-of-the-pants "Dyno" it is another car. It works!!!

Been running it on mixed roads for the last 3 days, morning to evening rush hour traffic. Freeway, it certainly pulls smoother, and harder. On normal 50/60km roads, it is more driveable without a doubt. when I use the Air-con, it has more power too,. It ssem s to have increased the fuelling across the range, and first gear is all but redundant as it quickly pulls this out to the rev limiter, put her in second gear, and you can feel it pull quicker to third, once again without doubt.

It tried her this morning on a freeway 5th gear run-on from 80 -> 150, and it left a 1.8 astra in the dust, he could not keep up with the constant acceleration the Woo had..... I then backed off having spanked the tool that was on my tail-gate. Lesson learned I guess... the Woo is a force to be considered next time they try to dust it to one side.

Heres the back-ground bit.

I changed the standard FPR 2 weeks ago, and was not overly impressed with the thing.... It is a cheap device... period. So, having done this with engines on Skis before, took the same route, and fitted a real FPR that can handle its position with precision. So, for sale... 1x OEM FPR... used for 2 weeks, redundant, and surplus to requirements.

Ya gotta do this mod with the Woo.

Like was said prior, I would like to see what the LM2 shows if I can figure a way to get it into the manifold before the Cat, and see what it says is going-on in the mixture, but, I am sure this mod works now.

[benzino]

how's fuel consumption?

[MMamdouh]

congrats on the success of your experiment

can you please but what you have done in very simple explanation so that an average guy like me can understand what you have done?

pics will be very helpful as well

MMamdouh

[benzino]

yeah, agreed

pics would be awesome and what adapter did you use?

[RichieOzzie]

Ok, Here we go..

Fuel consumption, as far as I can deduce is the same, and I guess it probably would be, as fuelling, therefore power is more efficiently created, rather than a leaned-out mixture failing to deliver the goods when the throttle is opened and the fuelling is more accurate.

I will nip and get some photos in the next 24hrs and post up a detailed way I did it.

Just more info now. I decided yesterday to set the base pressure of the FPR a little higher close to 50psi, and then use the vacuum side of it as a "Just to see" experiment yesterday. This was positive in results also!!. More driveabilty was clearly felt in the seat of the pants, and it didn't seem to have any real ill-effects on running. Tried it on the freeway this morning, and she pulled well up to the limiter, and cleanly.

My conclusion is the FPR (Fuel Pressure Regulator) in the car as standard is a cheap device, which just works, and that's it..!!, fit a real FPR, and, like Honda drivers know, it makes a difference.

I bought this one as a nearly new one from Ebay, and the sourced an adapter that fits on the end of the fuel rail. Fitted them up, and instant pleasure.

I will get the pics shortly, and a bit of detail with it.

The FPR I originally set to 44psi by bridging out the relay contacts, and tweeking it to the pressure required, locked her in, and off I went. Now I have extended the vacuum hose to it, and set the base pressure, which is what it runs at when no vacuum applied, to 48psi, hooked-up the pipe to the manifold, and it is a great result.

The things I am almost certain about is that the OEM FPR's are mass-produced, and lack the response and accuracy of an aftermarket item. This 'I have proven.

This was the ebay Regulator... http://cgi.ebay.com.au/ws/eBayISAPI.dll ... K:MEWNX:IT

This was the adapter ...... http://cgi.ebay.com.au/ws/eBayISAPI.dll ... K:MEWNX:IT The one I got was the bolt holes in a "T" and "L" pattern so I could be sure it fit.

The original FPR was a real pain to remove, as the thread-lock they used was pretty well solid. So, I just took the top of the bolt off with a Junior saw, and the FPR came out. grabbed the rest of the threaed part with self-grips, and turned it out easily... after all the fighting to get the bolt off, it was satisfying that it almost came out with my fingers.!

One thing to be weary of is make sure you use clamps for Fuel injection hose, and not the ones with slots in them for the screw that tightens them, and good hi-pressure fuel hose. Check the adapter is seated correctly, and doesnt seep out fuel under pressure. Check it after your first few runs. Keep the hoses off any very hot surface. I used the return pipe from my original FPR I dumped because it wasn't holding back the pressure. I cut it off at just before it bends around, and pushed this into the hose at one end, and the ither end clipped into the return line to the fuel tank as per normal. These are the same as the ones on the Fuel filter, so I guess an old filter tip may be useable if you can get enough length to hold in the fuel pipe.

Photos to follow very soon.

[benzino]

The FPR I originally set to 44psi by bridging out the relay contacts

was that the fuel pump relay?

[Richieb]

Yes, sorry about the ambiguity.

[Daniel]

Ok, Here we go..
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I used the return pipe from my original FPR I dumped because it wasn't holding back the pressure.
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Could it be the problem of your poor engine response?
What was the fuel pressure prior you replaced it?

Thanks,

[benzino]

i think he meant it was large enough to re-use and not create a large amount of backpressure

[RichieOzzie]

I changed the orig FPR for a replacement new OEM FPR, and ran it. It improved for sure, but still lacked that"Response" aspect. That's why I decide to go Real FPR to see if the item was just a cheap way to control emissions and fuelling.

[benzino]

so are you still at 50psi?

also, I'm guessing it's not rising rate?

and... pics?

[RichieOzzie]

Yes, It's a Rising Rate one I have put in there.

I have now set the base pressure to 50psi, and now connected the vacuum take off.

When fired over, the stable idle is 43psi at the moment.

I know that the standard is supposedly 43.5psi(3bar) for injector ratings. Remember the pressure increases, the injector will flow more fuel in the same open time by the ECU. A more accurate way to alter the fuelling on motors now-a-days.

My personal feeling was that the car/s always seem to run weak, even the spark plugs confirm this. Always look at the bottom third of the plug nose... never anything else but too weak.

I guess once running on steady throttle opening, this is a good thing, so that's why I put the vacuum feed to the RRFPR as a later plan.

Economy doesn't appear to be affected in our weekly use, which is a mixed bag of traffic lights, carriageways, freeway and village/local running around.

IT DOES make the car more tractable now for sure.

So will get the pics, in next few days, as the Girl has it today, so can't get chance until later.

If you look at the pics(Ebay ones in prev post), the vacuum/pressure feed will make it RRFPR. Rising rate will work with all setups to be honest. whether Forced induction or N/A blocks.