Piggy Back ECU?

[andydckent]

Hello!

I have just been doing some reading and wondering about these piggy back ecu's 'map ecu' ect. The claims of increased hp and more importantly for me greatly improved fuel consumption sound almost too good to be true. Does anyone know where I would look to get one of these and have it set up properly? Also will the initial outlay be repaid in reasonable time in fuel savings? Also if I was planning to put a boost controller etc would I be better to do this first or does it not effect the ecu's set up?

Thanks

Andy

[Nick Mann]

Your better fuel economy is unlikely to be more than a couple of percent. So don't go into it thinking that fuel economy is a good excuse to go for it!

If you want a good set up at reasonable cost by people who love doing their job, then the MAP ECU from Eurospec is a good way forwards. Give Ben a ring there. The MAP ECU 2 will control boost as well as fuelling and is a good choice IMO.

[andydckent]

Does anyone have any hard figures of the type of gains I could expect (hp and fuel) and how much I might expect to pay?

[Nick Mann]

What your asking is a bit of piece of string question.

MAP 2 ECU bought, fitted and mapped, £1000ish.
Power gains depend on supporting mods. You could potentially add as much as 25%. Mileage gains I'm not sure I could quantify, but don't expect vast improvements.

[Turbo_Steve]

Generally gains in MPG are down to better low-down power and responsiveness.....read better fuelling and more ignition advance. On the VR-4 it also needs the partial throttle delta enrichment correcting somewhat.

I don't think there is a piggyback that can really do this properly, though of course I could be wrong

A standalone is likely to get you the best improvements in performance and driveability and economy - it allows for better throttle corrections, cold corrections, more adaptable advance and potentially superior knock compensation.
Of course, it will cost you an arm-and-a-leg.

If you're after economy, it's not the way forward. If you're looking to spend some serious money and are planning a lot of other modifications (e.g. injectors, turbos, inlet tract, exhaust etc) then I'd invest now. Those who have spent the money (and there are few...it's expensive) haven't regretted it.

[aboo]

Sorry to hijack this thread but keep seeing this knock crop up what is it?

[Wodjno]

On the VR-4 it also needs the partial throttle delta enrichment correcting somewhat.

I don't think there is a piggyback that can really do this properly, though of course I could be wrong

What engine metrics are you using to map the above

[Wodjno]

Sorry to hijack this thread but keep seeing this knock crop up what is it?

http://en.wikipedia.org/wiki/Engine_knocking

[aboo]

http://en.wikipedia.org/wiki/Engine_knocking

Thanks now I understand

[Subaru ETA]

Hello!

I have just been doing some reading and wondering about these piggy back ecu's 'map ecu' ect. The claims of increased hp and more importantly for me greatly improved fuel consumption sound almost too good to be true. Does anyone know where I would look to get one of these and have it set up properly? Also will the initial outlay be repaid in reasonable time in fuel savings? Also if I was planning to put a boost controller etc would I be better to do this first or does it not effect the ecu's set up?

Thanks

Andy

if you are going for economy you are probably better off saving the money and buying a 1.5L hatchback.....

[Turbo_Steve]

What engine metrics are you using to map the above?

On a standalone I will always try and allow the MAF to do it's thing rather than get Throttle Delta Enrichment involved: IMO the MAF is usually good enough and definitely fast enough to do what needs to be done.

However: If you end up using MAP, which so many people seem convinced is better, then I would want EGT (either an infrared thermometer, or exhaust mounted EGT) and Wideband AFR, and repeatedly simulate various throttle changes to see what happens. The temps will always climb very quickly once you've pulled too much fuel out (and, of course, you may see some knock).

The problem is generally more to do with injector timing than anything else:
Changing the injectors seems to result in huge changes to this, moreso than just their flow-rate would indicate.

Part-throttle enrichment on the Legnum (whilst being logged on a proper laptop, not using a display) showed it dropping below 9.0 (and heading outside the accurate range of the probe) on throttle change: an astonishing amount of fuel. I'm not ruling out the possibility of an ignition problem (I seem to have some) but even then that's a lot of fuel!

[Eurospec]

With any standalone and with some piggybacks (map 2 and EMU) you can change the stock afr target for closed loop. Doing this will enable better fuel economy, but in fairness its buttons. If you went from 14.7 to 15.9 (verge of a lean missfire) you would save 8% of fuel. You then get into the issue that you need to dump a load more fuel to transition from cruise to acceleration, which in the real world of constantly being on and off the gas is not gonna help much on balance. I tend not to bother with anything leaner than 14.7 for the cruise.

My best gain on a map 2 was (IIRC) a before dyno of 256bhp to 324bhp. That was by best. Most come in around the 300 to 310 mark, but you are often fighting fuel cut, and if you can go to bigger injectors you can get away from it and you dont have that issue. As a result you can push a little more power.

Cheers,

Ben.

[Wodjno]

With any standalone and with some piggybacks (map 2 and EMU) you can change the stock afr target for closed loop. Doing this will enable better fuel economy, but in fairness its buttons. If you went from 14.7 to 15.9 (verge of a lean missfire) you would save 8% of fuel. You then get into the issue that you need to dump a load more fuel to transition from cruise to acceleration, which in the real world of constantly being on and off the gas is not gonna help much on balance. I tend not to bother with anything leaner than 14.7 for the cruise.

My best gain on a map 2 was (IIRC) a before dyno of 256bhp to 324bhp. That was by best. Most come in around the 300 to 310 mark, but you are often fighting fuel cut, and if you can go to bigger injectors you can get away from it and you dont have that issue. As a result you can push a little more power.

Cheers,

Ben.

So changing the injectors gets rid of fuel cut! This is in conjunction with na Piggy like Map or EMU i take it.. As you tell the ECU it's running larger injectors therefore it knows it can supply more fuel for the larger airflow/boost. Does this mean you still have to build an airflow map above and beyond the OE Ecu has.. I would have thought you would ? Or wouldn't you ? Are we still clamping the MAF signal or not ???

Now i'm confused

[Turbo_Steve]

The ECU doesn't know what injectors it has on it. How it works is (basically):
Say you put injectors that have double the flow rate of normal.
Then you tell the piggyback to either halve the injector outputs of the ECU (i.e. you have a full correction map, but you get the idea)
OR you tell the piggyback to halve the MAF signal, so that the ECU has double the headroom, and correct it's outputs appropriately.
By the time you've done all this, and had to correct the ignition maps as well (as you're in totally different load-points) then you'd pretty much be better off having mapped a standalone, as the results are invariably a lot better. If you do double the injector size, then you're also in danger of running out of MAF scale, as it will only flow so much (and measure so much). So you end up running a bypass pipe and rescaling the MAF (or junking it and using MAP > MAF conversion).

This is an exaggeration: nobody really doubles the injector flow rate (as it'd mean going from 350s to 800s or more) so it's not that big a deal: most people go to 500s, which means the MAF has sufficient flow & scale, the ECU isn't being lied to as much, and the outputs need less correction.

That's a gross oversimplification, but I hope it conveys the idea?

This is why I argued that something like an EMU ends up actually doing MORE work than a standalone: not only is it intercepting and changing ECU input signals, but also intercepting and correcting Ignition AND injector signals. If it's that clever (and reading ECU signals takes more processing grunt than you'd think!) why not just set it up as a standalone and have done with it: leave the factory ECU and it's false signals to deal with stuff the EMU won't but have the EMU run the engine on it's own. It virtually is anyway!

[Wodjno]

Cheers Steve

Makes sense now

Everytime you post something about the EMU, it sounds like you understand a little more why it's such a great bit of kit for the money

And should probably cost twice the price ??

And i like it cos everyone else hasn't got it

[Turbo_Steve]

I think it IS a great bit of kit for the money....never ever said it wasn't a perfectly good solution to a lot of peoples problems.
It's the age old thing, though, of doing it cheap or doing it right:
Re-interpreting ECU outputs will always be a fudge. At low levels of modification, I have no issue with it at all: it's a cheap way of correcting the ECU shortfalls.

The problem arises if you want to get the "best" map out of the car, or if you want to go to silly levels of modification (i.e. huge injectors, more complicated ignition system etc etc etc) then the piggybacks start to look a little limited.
Valmes has got good results, and professes to have retained an entirely driveable road car with no sacrifices at all. Without having driven it, I can't (i.e. nice smoorth responsive throttle, no bogging, no hesitation, good idle, good ignition curve >VERY tricky< and good boost and fuel control for notmal driving, no overfuelling on throttle change...all these things are difficult!) at that level of modification takes time, and time costs money, especially when it's a mapper. My worry is that if you're buying a days mapping on a more modified car, it may simply involve the same amount of work (and cost) as buying and fitting and mapping a standalone as it does to get the piggy back "just so".

I am being deeply picky here, as most people will never reach that state of tune and are looking for a few extra bhp, in which case the piggyback is great.

But for every Scoob I've setup, we've found that we can get more power AND better mpg from a modified car with a standalone on it.
A good example was the GT40R on the EJ257. This ran with an EMB on it that someone else set up. We fiddled and fiddled with the mapping on there, and the car was fast fast fast...but it was always boggy off boost, slow to build boost from low RPMs, and a bit gutless, and a sharp throttle change would result in a loss of power, no matter how much we tried to trim the injectors and put it in the map, or to change the throttle delta or all sorts. The car was driven to events and typically returned 18mpg. It dyno'd 504bhp at 1.4Bar boost IIRC.
In the end, we chucked it and bunged in an M800. After a days mapping, we had a driveable car that, again, dyno'd 508bhp, though lower in the rev range.
This is just the usual mapping rubbish.

A second days mapping made the big difference: the car became positively driveable: we were able to add a couple of RPM points and load points around the area where the turbo would suddenly spool up. This allowed better interpolation, and a smoother transition to boost.
If you lifted off whilst building boost, it no longer backfired!
Suddenly nailing the throttle didn't result in a wash of unwanted fuel, but a well managed boost target, a touch of advance and just the right amount of fuel.
We were able to have an auxilliary table setup to control the flap in the exhaust, so it was no longer a switch on the dash for "quiet / loud" but truly active - it would only open up when the engine needed it.
Fuel economy became 32mpg, as you could drive the car "NA" rather than always having your right foot down for power / boost.

Now a lot of this was down to the mapper, rather than the technology: I suspect that persistance with the EMB would have got us the same results in the end. But I also suspect we would have been chipping away at it for days...maybe weeks, rather than two days of core setting up, and then a little bit of finessing. With the closed loop knock monitoring and AFR targeting on the M800, it virtually mapped itself! It later allowed us to control the WI as well as traction control and would have let us control a centre diff if one was fitted, and could have managed a NOS system too.
It also has extra "neat" features, like allowing control to disengage the alternator when accelerating over 50% TPS. Or on a drive-by-wire car, it will improve throttle pedal response by taking over the throttle butterfly control.

It also allowed us to have a little green rocker switch on the dash that we could flip when we loaded the car with C102, and flip it back when it was next filled up with Optimax. It would even have allowed us to run a cat with pre and post sensors, and do all the usual emissions shenannigans, though I've never tried this.

I am not knocking the EMB or the EMU, but I think you have to have your eventual aims in sight before you plump for an ECU. Race cars aren't run on piggybacks for a reason: it's not that they don't deliver the performance, it's that they're harder to work with.

[Turbo_Steve]

Just to add:- Bradc is using an SM4 and returns pretty good economy for a modified car. I am speculating, but if it's giving him good throttle response and low down power, as well as a better throttle enrichment, AFR targets (in closed loop) and correctly setup for the available fuel, it is like to be improving his MPG, no?

More low down power will almost always improve economy, as people generally try and cruise at the cars "sweet spot" subconciously...and that's usually just on the point where boost starts to build. So that, if they should press the pedal, the car responds rather than spools, IYSWIM?

[elnevio]

Brad's secret is out!

Superb info Steve - you should do this for a living...

[Mitsiman]

The ECU doesn't know what injectors it has on it. How it works is (basically):
Say you put injectors that have double the flow rate of normal.
Then you tell the piggyback to either halve the injector outputs of the ECU (i.e. you have a full correction map, but you get the idea)
OR you tell the piggyback to halve the MAF signal, so that the ECU has double the headroom, and correct it's outputs appropriately.
By the time you've done all this, and had to correct the ignition maps as well (as you're in totally different load-points) then you'd pretty much be better off having mapped a standalone, as the results are invariably a lot better. If you do double the injector size, then you're also in danger of running out of MAF scale, as it will only flow so much (and measure so much). So you end up running a bypass pipe and rescaling the MAF (or junking it and using MAP > MAF conversion).

This is an exaggeration: nobody really doubles the injector flow rate (as it'd mean going from 350s to 800s or more) so it's not that big a deal: most people go to 500s, which means the MAF has sufficient flow & scale, the ECU isn't being lied to as much, and the outputs need less correction.

That's a gross oversimplification, but I hope it conveys the idea?

This is why I argued that something like an EMU ends up actually doing MORE work than a standalone: not only is it intercepting and changing ECU input signals, but also intercepting and correcting Ignition AND injector signals. If it's that clever (and reading ECU signals takes more processing grunt than you'd think!) why not just set it up as a standalone and have done with it: leave the factory ECU and it's false signals to deal with stuff the EMU won't but have the EMU run the engine on it's own. It virtually is anyway!

I couldn't agree with ths more. This is an exact reason why they are too much trouble We tried using an emanage on Madhavs vehicle and instead went haltech and it was done in 1/2 time with better results

[Eurospec]

Ultimately, a standalone will always deliver a better result than a piggyback. The 2nd generation piggybacks are very good, but you are still limited by whats in the stock ecu- example, on a cold start you cannot get rid of the cold start pulse width enrichment that the stock ecu does. If you have big injectors, that is gonna deliver a LOT more fuel than you want at cold crank.

I have been trying to help a guy with a UK mk4 supra who bought a map 2 from a dealer in the US. He runs 850cc injectors and a big single (T88) instead of twin sequentials.

Personally i would never have sold him a map 2 to cope with those mods- its too extreme for the stock ecu. He has a problem whereby the car leans out on boost. This is coming from the underlying lean spool of the 2nd turbo in the stock sequential map in the ECU. You cant change that. Hit a certain rpm and airflow and the stock ecu deliberately leans out to spool the stock 2nd turbo.

The problem is that because hes running bigger injectors he is using the map2 to tell the car its seeing less air than it is to get it to do a smaller squirt on the bigger injectors. As a result the load is assessed as lower, and it puts it right where the lean spool of the stock 2nd turbo is in the stock map when its making about 10psi on the big single!

Now the guy he bought it off in the states said foxtrot oscar, you bought it, TSB! He then proceeded to rain his discontent on me and anyone who would listen. In fairness, not my problem! He bought the wrong thing for your application, from a non UK source, but nevertheless i tried to help him out.

Anyway i digress, the point is if you do something extreme, then a piggyback is gonna have its work cut out to run it well. A standalone would do it easily.

So basically, pick the product suited to your application- if you have gone for extreme mods, but you want it to behave nicely and drive to the utmost, then go standalone. If you are doing fairly basic mods then a piggy back will do it.

You can even go with fairly extreme mods if you keep things within certain parameters- example- my gto runs huge turbos, 1000cc injector in place of stock 360s, cams etc etc etc all on a map 2 and stock ecu, but i dont care that it runs too rich on cold start, so thats fine. If i had sequential turbos the stock ecu would **** a brick and the map2 couldnt compensate it.

Cheers,

Ben.