EFi mapping 3.9 and 3.5 (hotwire/14CUX)

[peterzrh]

Gentlemen,

Your wisdom please. I have a Rover 3.5 running at 10.5:1 which is to be fitted with the larger valve cylinder heads and EFi system which originated from a 3.9 Range Rover. This will run lambdas in feedback mode.

Now my understanding is that as a MAF rather than MAP that these adapt fairly well to different applications. My question is, is the 3.9 map

a. the same or different to the 3.5.
b. workable on a 3.5
c. good for a 3.5
d. optimal for a 3.5 (ok unlikely)

If the results are unlikely to be good, what's the best source of an alternative?

Any approximate estimates of gains over 2xHS6 and the small valve, dual spring heads? Unfortunately I'm bound by the crappy P6 manifolds and exhaust which will likely go dual in the course of time.

Be gentle with me, I'm new to this business. I'm not interested in alternative carb solutions, EFi it is. Thanks in advance.

[DaveEFI]

Main snag is you're dealing with 25 year old plus parts and technology. Narrowband lambda control is there to keep the mixture correct for a catalytic converter. If you don't have cats, you'll get better results by going outside the 14.7:1 AFR for better performance and economy.

Perhaps the most common way is to use a MegaSquirt and wideband O2 sensor.

Lots on here do with the RV8, and plenty help is available, as it's designed as a DIY system.

Just to add, with that high a compression (the Vitesse is only 9.75:1) ignition timing is critical. So you might consider letting MS map that too.

But you could do it in stages. Fuel only first and get that sorted, then add mapped ignition.

[SimpleSimon]

This guy can map the Lucas CUX ecu if your interested rather than being bound over by only Mark Adams try Jools at http://www.kitsandclassics.co.uk/ thats if you want to stay with the Lucas Hotwire system of course lots of the TVR brigade are very happy with his service, I dont put up piss poor traders either

[peterzrh]

Thanks guys. Experience is gold dust. TBH as it is for a Rover saloon, I'm not after the last word in performance.

I'd be more than happy with something approaching stock Rover Vitesse performance and would like to stay with standard components if possible.

Reliability and driveability are king here with a bit of extra poke.

Obviously I don't want any significant issues relating to over or underfuelling, burned valves or fouling.

[DaveEFI]

It all really depends on whether you're going to get someone to do things for you, or DIY.

I found very worthwhile benefits in changing to mapped ignition from the dizzy - if nothing else in reliability.

[DaveEFI]

Thanks guys. Experience is gold dust. TBH as it is for a Rover saloon, I'm not after the last word in performance.

I'd be more than happy with something approaching stock Rover Vitesse performance and would like to stay with standard components if possible.

Reliability and driveability are king here with a bit of extra poke.

Obviously I don't want any significant issues relating to over or underfuelling, burned valves or fouling.

Well, the Vitesse had the flapper injection. Not the hotwire. And things like a different compression ratio etc can need different mapping for best results. So there simply isn't a standard injection system exactly for your engine.

[peterzrh]

I understand that the Hotwire is a more advanced system than the flapper and this is where to start with a basic EFi conversion. BritishV8 has a few nice articles. Only four basic connections. I've done a fair bit of reading, I understand the components and my questions were framed to be quite specific because obviously a rechip is a significant consideration from otherwise £100 worth of secondhand RR parts.

I gain with higher compression but I lose through a more restrictive exhaust than a Vitesse, so I'm hoping to get SIMILAR results overall. I'd be happy with 180bhp, delighted with 190bhp. My car is also an auto (boo, hiss so can we say VdP EFi and not Vitesse?) so I can gain this way without lumpy and unfriendly cams. As I drive longer distances, a fuel economy advantage would be helpful as increased range is useful.

I'm DIY with some assistance from a friend in a local garage. I want simple and as near to stock parts as is workable. From there I may tinker later but for now it has to be as near as possible to fit and forget.

[DaveEFI]

I wish you well with your £100 worth of second hand parts.

But you appear to have decided how you'll do it anyway, so just come back here for help with any problems as you go.

[peterzrh]

OK, will do. So no one has direct experience of a 3.9 map on a 3.5 motor?

I'm not fixed on a solution, I'm looking to keep it simple. I'll follow a different route if it's worth it.

[ChrisJC]

I would expect the 3.9 / 3.5 maps to be very hard to tell apart from the driving seat!

There was a 3.5 Hotwire Discovery I believe. If you can get the ECU from that, it might help.

Chris.

[DaveEFI]

OK, will do. So no one has direct experience of a 3.9 map on a 3.5 motor?

I'm not fixed on a solution, I'm looking to keep it simple. I'll follow a different route if it's worth it.

There was an SD1 3.5 fitted with a hotwire system. Lots of problems with it on the club forum. But this could have been down to faulty parts etc or poor installation. I'm not sure what happened to it.

But I don't know the hotwire well. When my flapper started giving trouble, I went for MS after a lot of research, since hotwire was also getting on a bit by then. Although I am pretty good at auto electrics, so installing it didn't look to be much of a problem. And I've never ever regretted the decision.

[SimpleSimon]

With the Lucas Hotwire system the 02 sensors take care of fueling give or take 20% fueling either way providing your on the green tune resistor under around 3000/3500 rpm thats the good bit but after that your on the 3.9 map only be it good or bad and what the cold start enrichment will be like is anyone guess I think its a chancy move quite frankly but if you get a decent AFR gauge/wideband controller you can monitor things yourself you may get lucky the Lucas can be quite tolerant

[DaveEFI]

My auto SD1 spends a gear deal of time under 3500 rpm. The main difference I've found with the MS over the flapper is decent low revs grunt. Being an auto, if you ask for decent acceleration on the move, it will normally do so in second gear - unless you use kickdown to first. And it now pulls like a train under those circumstances. But uses something like down to a 12.5:1 AFR, depending on throttle etc. The flapper only really went rich enough pedal to metal - and never at low RPM. At cruise, it's now going closer to 16:1

To summarise, the MS doesn't seem to give more power at full throttle than the flapper. Just makes it seem a lot more lively in normal driving.

As I said, I don't have any direct experience of the hotwire. But if you're going to use narrow band lambda control, I'd say you'll loose out over what is possible.

[peterzrh]

What I will probably do is just try and get hold of a 3.5 map chip as well and just see which works best for now. I can't imagine these have much commercial value to anyone.

From what I've read the 3.9 maps are very lean. Perhaps in operation they are actually a better compromise on the 3.5 performance wise? From the maps I've examined and plotted, the differences across quite a wide range of motors is surprisingly small, so I can't imagine the difference between the 3.5 and the 3.9 being massively radical and in effect possibly nil in the operating mode of the lambdas, which on an auto is going to be almost all the time.

At the end of the day I am an electrical engineer and these EPROMS are pretty simple, I could change it myself. The issue being finding good shared maps.

I admire the ambition of you guys, I really do but the initial goals are to get a workable EFi car, nothing more. In fact the local registration testing regime here makes life difficult if you go over +20% and then +30% power increases, so a solution perhaps should not be too optimal for the time being. I'm thinking eventually a custom map with both an everyday tune and one to get through the test....

The link kindly provided above actually does have an EFi P6. It gets 150bhp, at the wheels. Given the crappy BW35 or 65, that's actually pretty good, going to be over 190bhp at the flywheel. Which is enough. Typically a P6 will have 95-105 bhp at the wheels with an auto (which is so depressing), so even if I get say 2/3rds of what this person did that is a monster difference, pushing the limit of the regulations here. It would be nice not to set off the "abgas" alarms in the carpark too....

[Quagmire]

Somehow I think the people on

http://www.kitsandclassics.co.uk/engine-ecu/

are not fans of Megasquirt... Read the bit at the bottom:

"Megasquirt to Emerald K6 ECU Upgrade

We are being asked by a few people now about upgrading their Megasquirt ECU installs to something better. We can now offer a Megasquirt to Emerald K6 upgrade from £1250.00 fitted and mapped. You keep your Megasquirt ECU and original loom to sell on aswell so reducing the overall cost. The conversion retains your existing crank sensor/trigger wheel, coil packs, HT leads, wideband lambda sensor etc and replaces the Megasquirt control unit and engine loom with a new bespoke loom for the Emerald K6 ECU.

Key benefits of going from a typical MS2 install to an Emerald K6 is real time map switching, adaptive fuelling based on targetted AFR, accurate lambda feedback, user friendly mapping software package, excellent reliability and local mapping experts easy to find (many mapping shops do NOT map Megasquirt ECUs because they can be troublesome)."


The bit I have highlighted bold is nonsense! All of the supposed "Benefits" of switching to the Emerald even my MS1 unit does! Accuracy of lambda feedback is a product of a) the unit you are using and b) making sure that your grounds are all correct, and you haven't introduced any offsets.

And as for reliability - 2 of my 3 vehicles are MS'd and have never let me down as a result of the ECU. In fact, the P6 (running MS2) has only stopped once and that was a duff EFI pump.

The Landrover (MS1) has also only stopped once and that was a problem I had made myself when the hose on the in-tank fuel pump blew off so it was merrily pumping fuel round and round the tank but not actually out of it...