3.9 EFI Megasquirt idle and low speed running problems

BenL · Post by **BenL** » Mon Jun 28, 2010 8:31 pm

Hoping to get a few ideas about how to solve the idle problems with my 3.9 EFI Rover P6 Estate. I won't go into too much detail but it is a 3.9 EFI (40000miles) with Piper 270/110 road cam and standard heads. It's fitted with a Megasquirt injection system running an EDIS 8 ignition system. It's been set up on a rolling road and produces about 190 to 200 hp max. Quite nicely mapped with good throttle response, smooth acceleration and about 25-30mpg.

HOWEVER! I'm not entirely happy with the idle. It's a little fluffy and the car shakes around with some fluffy sounding misses from the exhaust. Very frustrating as I has expected a rock solid idle from the injection set up. I've spent a lot of time experimenting and replacing anything that I suspected could be at fault (fuel pump, plugs, leads, regulator etc etc)

This is a short video of the sorst at idle. Frustratingly it wasn't actually too bad but....

http://www.youtube.com/watch?v=FlJhg3od-KM

In the back ground you can hear the new bosch fuel pump. I replaced it because the old secondhand one made the same noise but worse. Does anyone know it's cause and if it could be related to the idle problem? My guess is air in the fuel but the pick up is from the very bottom of the tank. Good filtration before and after the pump.

http://www.youtube.com/watch?v=HBDEWLopJEk

Car being blasted up the local bypass!

http://www.youtube.com/watch?v=gc2aTQtg6Ak

Basically I would like to get the engine to idle at about 650-750 rpm (it's about 850+ at the moment) but I just can't get rid of the slight misfire and have been round in circles. Has anyone had similar problems? Could it be the fuel pump noise is a clue?

daxtojeiro · Post by **daxtojeiro** » Mon Jun 28, 2010 8:44 pm

Blimey, is that cracking noise the fuel pump? If so replace it asap as thats not a great sign.

To be honest your first job to do is to replace the pump and try it again to see how it goes. If its still the same come back and let me know as Im sure we can cure that,
Phil

BenL · Post by **BenL** » Mon Jun 28, 2010 9:17 pm

Hi Phil! You may remember where the MS11 came from!

That is a new pump and as I said the old one made the same noise but was actually marginally quieter overall. When I check fuel pressure it's spot on and the regulator is working correctly.

The cracking noise actually sounds like air bubbles being sucked through the pump but as the intake is a 15mm bore hose directly from the bottom of the tank I can't understand how it could be aerated. Is there some detail in the plumbing of the fuel pump that I have missed?

Is there some way I could rig a temporary fuel supply arrangement that would definitely not suffer any problems that could affect the idle? I can see how small quantities of air in the fuel could affect the metered fuel at very low idle pulse widths.

stevieturbo · Post by **stevieturbo** » Mon Jun 28, 2010 9:49 pm

Its 15mm from tank to pump ? no obstructions whatsoever ?

And what form of baffling etc is inside the tank ? When static not a problem, but I assume the tank is suitable for feeding an efi pump when the car is moving ?

Is the tank adequately vented ? ( ie, as fuel is used, a vacuum isnt created ? )

Is the pump rubber mounted or solid ?

The noise doesnt sound good, but may not be a major issue. When hot, my pumps dont always sound the nicest. But there are never any running issues. ( ie hot day after a lot of driving....fuel temp isnt a cause, as its not that warm )
Is a bit odd really, but they do sound horrible at times

As for the idle. Too hard to make out from a video really

BenL · Post by **BenL** » Mon Jun 28, 2010 10:01 pm

The only thing in between the tank and the pump is a filter. A good quality bullet one with a washable element in it. The tank isn't baffled but it has a small sump in the bottom from where the fuel is taken.

Never any problems on the open road just at idle or very low throttle openings.

Will try and get a more convincing video of the idle problem. Like I say it was actually running reasonably well there but it's still rough enough to shake the car. I'm pretty sure it should be possible to get a rock steady idle from a rover v8 in such a mild state of tune.

I suppose though i can't really ask for much more help until I cure the fuel pump noise.

stevieturbo · Post by **stevieturbo** » Mon Jun 28, 2010 10:03 pm

What size is the filter ?

BenL · Post by **BenL** » Mon Jun 28, 2010 10:13 pm

It's one of the SYTEC Motorsport ones that is intended for use as a pre-filter.

I've just been reading a little information that I can find about fuel pump cavitation and wondering whether to give it a try without the filter. Restrictions etc are mentioned as posisble causes.

The tank is pretty spotless inside now as most of the poop has been filtered out and removed when i've cleaned the filter.

stevieturbo · Post by **stevieturbo** » Mon Jun 28, 2010 10:23 pm

Where is the filter in the video ? it looks like the fuel supply is direct from the tank ?

It does sound like cavitation, but with a setup like that, it shouldnt realy happen.

Ive only a 15mm outlet on my tank, and it feeds a pair of 044's via a single filter. Not ideal, but it would be major work to alter it. As I say, its only when very warm my pumps make not nice noises. At all other times they are smooth running

BenL · Post by **BenL** » Mon Jun 28, 2010 10:31 pm

The filter is behind the pump and there is a pic here. Elbow out of tank and U-shaped section of hose between the filter and pump. Could be asking for cavitation problems?

I've been here a million times though, I think i've identified the problem make the changes. Start the engine and..... nothing changes!

The pump is not a genuine bosch tho'. I was assured by the chap who ordered it for me that it would be but it looks to me exactly like the 3rd party aftermarket ones sold on Ebay.
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BenL · Post by **BenL** » Mon Jun 28, 2010 10:32 pm

BTW That pic shows the original secondhand pump that I had fitted at first.

DaveEFI · Post by **DaveEFI** » Mon Jun 28, 2010 11:22 pm

BenL wrote:Hoping to get a few ideas about how to solve the idle problems with my 3.9 EFI Rover P6 Estate. I won't go into too much detail but it is a 3.9 EFI (40000miles) with Piper 270/110 road cam and standard heads. It's fitted with a Megasquirt injection system running an EDIS 8 ignition system. It's been set up on a rolling road and produces about 190 to 200 hp max. Quite nicely mapped with good throttle response, smooth acceleration and about 25-30mpg.

HOWEVER! I'm not entirely happy with the idle. It's a little fluffy and the car shakes around with some fluffy sounding misses from the exhaust. Very frustrating as I has expected a rock solid idle from the injection set up. I've spent a lot of time experimenting and replacing anything that I suspected could be at fault (fuel pump, plugs, leads, regulator etc etc)

This is a short video of the sorst at idle. Frustratingly it wasn't actually too bad but....

http://www.youtube.com/watch?v=FlJhg3od-KM

In the back ground you can hear the new bosch fuel pump. I replaced it because the old secondhand one made the same noise but worse. Does anyone know it's cause and if it could be related to the idle problem? My guess is air in the fuel but the pick up is from the very bottom of the tank. Good filtration before and after the pump.

http://www.youtube.com/watch?v=HBDEWLopJEk

Car being blasted up the local bypass!

http://www.youtube.com/watch?v=gc2aTQtg6Ak

Basically I would like to get the engine to idle at about 650-750 rpm (it's about 850+ at the moment) but I just can't get rid of the slight misfire and have been round in circles. Has anyone had similar problems? Could it be the fuel pump noise is a clue?

How are your injectors grouped?

My 3.5 auto idles nicely at 600 rpm with the A/F ratio set at 14.1:1. But it's a standard EFI apart from the MegaSquirt 2 V3 and EDIS.

ChrisJC · Post by **ChrisJC** » Tue Jun 29, 2010 7:15 am

Is it a 3.9EFi inlet manifold?
What air filter is fitted?

I wonder if there's a resonance in the inlet at idle speeds.

Chris.

BenL · Post by **BenL** » Tue Jun 29, 2010 1:56 pm

@ ChrisJC: The manifold is standard 3.9 EFI but the air filter is a K&N fitted as shown. I made an ally spigot to take the K&N with a nice radius, it uses the original air-hose. I hadn't considered a resonance problem but the idle problem occurs at a variety of speeds. Also the MAP signal is very good and solid. An idea worth investigating tho'. I could try extending the inlet hose quite easily.

@DaveEFI: I'm jealous! Every time I hear a rover v8 idling well i'm filled with envy! Injectors are banked L & R as per the original 3.9 set up. I have to admit I can't remember now how they set to fire in terms of pulses per rev. I did try various settings to little avail. Did you find there was a big effect from this setting. Would be very interested to know more about your set up. Do you have any information about it online? Whereabouts in the country are you?

Thanks for replies

Ben

stevieturbo · Post by **stevieturbo** » Tue Jun 29, 2010 6:16 pm

Is the U hose definately not kinked at all between filter and pump ?

BenL · Post by **BenL** » Tue Jun 29, 2010 6:57 pm

It's been changed since that pic was taken and it's now go a piece of copper with two elbows in it.

Going to make a up a piece of 15mm copper tube tonight using a tube bender and run it between the tank outlet and the pump (take out the pre-filter). To see if that has any effect on the pump noise.

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3.9 EFI Megasquirt idle and low speed running problems

3.9 EFI Megasquirt idle and low speed running problems

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