RV8 Injector Wiring

General Chat About Electrics, And Ignition Systems.

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DaveEFI
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Post by DaveEFI »

One thing I sort of omitted is the SD1 has a series resistor in the pump feed.
IIRC to cut down noise, as the pump is never needed to run flat out. Could be that restricts the maximum pressure the pump is capable of. And it could be larger versions of the engine dispense with this resistor while using the same pump.

But the point you made stands good. Within reason, the pressure isn't going to matter that much if it is mapped at that pressure. It might matter at maximum load if the injectors are close to their maximum flow, as the pressure does effect that.

What I'm unclear about is why autotune didn't seem to work correctly - I've found it pretty good, apart from at very low revs. Which is likely because my O2 sensor is rather a long way down the pipe, and I've set the compensation for that.


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Post by Cobratone »

Autotune can only tune the ve table according to other parameters like afr and spark tables, if they are not right then no matter how much you autotune it then the ve table will be incorrect!

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Post by richardpope50 »

I think I'll close this post by saying that the whole point of the rolling road session was to correctly map and set up the ECU. Up until then I had been using a map given to me for this engine with very little changes at all apart from a few to get the engine to fire in the first place.

Speaking as a layman, the MS ECU set-up is so complex (or rather so confusing) with the documentation being pretty poor as it assumes one knows all there is to know before one starts. Prior to buying the whole kit, I had assumed that it was a kit that would 'Plug n Play' with a straight forward set of documentation one could follow logically to set things up to an average level. Having said that, I had always planned to have an expert finish the job off and Dale, IMHO, did / does just that.
Richard.
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Post by stevieturbo »

richardpope50 wrote:I think I'll close this post by saying that the whole point of the rolling road session was to correctly map and set up the ECU. Up until then I had been using a map given to me for this engine with very little changes at all apart from a few to get the engine to fire in the first place.

Speaking as a layman, the MS ECU set-up is so complex (or rather so confusing) with the documentation being pretty poor as it assumes one knows all there is to know before one starts. Prior to buying the whole kit, I had assumed that it was a kit that would 'Plug n Play' with a straight forward set of documentation one could follow logically to set things up to an average level. Having said that, I had always planned to have an expert finish the job off and Dale, IMHO, did / does just that.
Rarely is anything ever truly plug and play as far as a finished map goes, unless it is from a supplier who has done many many of them, and your setup is very very similar or identical.

Ive only ever looked at the MS software a couple of times...and it is rather strange in some respects.

But same with any ecu or computer, GIGO. People see names like Autotune and think "Hey, it will map the thing for me without me doing anything".
Rarely is that the case, as many factors need to be correct for such features to actually work.
Get some of them wrong, and you'll always be chasing your tail until they're right.

Once you're on the right path though, everything after should be a lot easier and more straightforward
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Post by DaveEFI »

Very pleased to hear it's running properly at last.

I was just curious about the fuel pressure thing. As altering that dramatically will have a big effect on the fuelling across the entire range. If you change that, you'll then need to re-map.

Recently, James who is one of the Extra code developers has revised the instructions which are now in PDF form. That may go some way to addressing the problems of finding the info you need, when installing and tuning MS.
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richardpope50
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Post by richardpope50 »

I suggest my very final post on this …

Stevieturbo, yes I agree with you but presumed I would have an average map to get the engine running and driveable and then always planned to take it to a RR to get it set up 100%. I still cannot believe that you cannot seem to have a map and settings for each engine in a standard configuration off the shelf with a simple list of re-set this for xxx, this for yyy. (I’ve had a life-long career in IT and often used this approach.) However …

Dave, once the injector pressure was fixed the map was then able to be sorted. Dale found that he could not sort the lean fuel issue until the fuel pressure was sorted. However, I’m on the right road now.
Richard.
Dax Rush 5.0l TVR V8, EFI with Megasquirt ECU and wasted spark, Racelogic Traction Control and Quaife LSD ....... Now nut and bolt restoring a TR6

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Post by r2d2hp »

My Griff engine came with 2.5 bar pressure reg and 214cc injectors.

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Post by stevieturbo »

richardpope50 wrote:I suggest my very final post on this …

Stevieturbo, yes I agree with you but presumed I would have an average map to get the engine running and driveable and then always planned to take it to a RR to get it set up 100%. I still cannot believe that you cannot seem to have a map and settings for each engine in a standard configuration off the shelf with a simple list of re-set this for xxx, this for yyy. (I’ve had a life-long career in IT and often used this approach.) However …

Dave, once the injector pressure was fixed the map was then able to be sorted. Dale found that he could not sort the lean fuel issue until the fuel pressure was sorted. However, I’m on the right road now.
You can have a map like that, but as said, given engines vary so much it is difficult unless the person supplying it has huge experience and a vast array of maps, and can ensure all sensor settings are correct for your specific application, your fuel and ignition system are exactly the same etc etc

There really are just loads of variables. Add to that the huge number of variables within the software...and it's easy to spiral into oblivian

If he had no control over fuel with the lower pressure it does sound like your injectors are beyond their max flow, so even now with slightly raised pressure, IDC's may well be very high. So worth checking.
Whilst 80% is the preferred value, I'd often pushed injectors to 100% with no issues.
But if the engine might spend a lot of time at those high loads, then something within the fuel system definitely needs upgraded to get away from 100% duty
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Post by DaveEFI »

What confused me was you saying it was initially running very rich, and that the fuel pressure was too low. I presume you meant weak?
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Post by richardpope50 »

DaveEFI wrote:What confused me was you saying it was initially running very rich, and that the fuel pressure was too low. I presume you meant weak?
No, it was initially very rich then with spark plug gaps being reduced, a load of settings needing a change plus the timing was way out. In fact the engine was trying to start from fuel vapour in the oil! So, after changing the oil, the timing, loads of settings and starting mapping, it turned to be very weak. Dale could not get it richer without increasing the fuel pressure and only then was he able to map so that the air fuel ratio was pretty much spot on. Then my cooling problem stopped power runs and further fine tuning.

As for my engine, it is a standard TVR Griffiths 500 with about 41k on the clock. I took it out of the donor myself.

Still, I'm happy now everything is fine as far as the engine and ECU are concerned.
Richard.
Dax Rush 5.0l TVR V8, EFI with Megasquirt ECU and wasted spark, Racelogic Traction Control and Quaife LSD ....... Now nut and bolt restoring a TR6

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Post by baileyperformance »

Hi Folks,

Regarding fuel pressure -

The 5.0 uses the same injectors as the 3.9 (and some 3.5s) These injectors are around 220cc.

On the higher output engines 220cc injectors are getting very close to been maxed out, 95% duty is common.
To reduce the duty cycle on the injectors changing the fuel pressure to 3.0bar make a worth while difference, normally reducing the duty cycle from 95% to 80-85%.

We are fans of high fuel pressure, our conversions use Weber alpha 4.5bar regulators as we found better MPG and throttle response when running high fuel pressure compared the normal 2.5/3.0bar.

Cheers Dale

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DaveEFI
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Post by DaveEFI »

Don't most current injection systems use rather higher pressure than the Lucas systems did as standard?

Other thing is, of course, if the injectors ain't reasonably close to maximum at maximum demand, you might have problems getting a decent tune at idle, etc.

Thanks for clearing up the mystery.
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Post by stevieturbo »

Not so much. For a return style, 3-3.5 bar is still fairly normal. Dead end systems would tend to run higher though with 4-4.5 bar being normal.

Modern injectors certainly like higher pressures, not sure how very old injectors cope.

But usually spray and atomisation will be better at higher pressure

But some injectors are designed with different spray patterns in mind
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