Is A Newer Piggy Back ECU Viable?

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Is A Newer Piggy Back ECU Viable?

Post by MR2T_Jake »

Hi All,

I've been looking into ecus etc to try and squeeze some power right out of my mr2 and have been informed by a local turbo owner a company literally around the corner are the main dealer for Unichip, and he had a Q+ installed on his turbo!

He only has an intercooler and exhaust, and they are able to get him pushing 300bhp without cramming 17+psi down a stock block!

Now I understand all the stigma during the early 2000s of piggyback ECUs, but I would assume the tech has gone through a fair amount of changes over the 20 so years?

Anyone got any first-hand experience with any piggyback ecus? And comments and knowledge to help me decide.

And yes I know I can get a Link for £1000, but then I would need to add a few more £100s on sensors and solenoids, then £500 or so on tuning... whereas these Unichips can be supplied, fitted and tuned for £800 including a boost solenoid.


I can't figure out how to put in an image here, so this is my cry for help. :confused1:
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Re: Is A Newer Piggy Back ECU Viable?

Post by MR2DI4 »

You need to be far more specific. We are talking that made up flywheel Hp here for the sake of keeping it simple because everyone ends up using this fictional number.

You will never get 300Hp out of the Rev 1 Turbo on the 440cc injectors, the stock ECU is not the limiting factor the injectors are. Even changing the CT26 to the CT20b will still not get you there. 17psi is about the limit and then you run out of fuel.

You can get a little over 300Hp on the later gen with the 550cc injectors, The stock ECU is probably still not the limiting factor to more power. The CT20b will be banging out 19psi.

What I'm really saying is you could spend up large on even a link ECU and get bugger all power increase if thats all your changing.

The reason you go for a different ECU is you can tune it for much bigger injectors and thats where you will get significantly more power. You simply cannot get enough fuel into the engine using the stock injectors to make massive gains.

Piggyback is really only delivering what my stock ECU is doing but its cleaner. My setup has a string of little external boxes attached to the stock ECU for fuel cut and speed limit removal. Its a birds nest of wiring but it works.

There are lots of ways to get more power from the stock ECU before it needs to be thrown in the bin but its both time consuming and expensive to do the mechanical support work required. Personally if I couldn't have done all the work myself I would have never bothered modifying the car at all. The gains were not huge but it was a great project.

Would be really interesting to know what maximum power has been achieved with a really nice engine build and the stock ECU and injectors and the CT20b. Problem is that never seems to happen as a nice engine build usually automatically jumps to bigger injectors and aftermarket ECU.

I think the stock ECU is highly underrated. You can get another 15% power over stock but you have to realise at that point all the factory safety "Over rich" condition is gone that allows for things like the fuel pump pressure dropping off over time. My car is no longer "Idiot proof" you have to watch the fuel pressure gauge, the AFR gauge and run it on 98 octane fuel all the time and look after the oil. Everything is now maxed out so if something drifts out of the new spec it will go bang.
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Re: Is A Newer Piggy Back ECU Viable?

Post by MR2T_Jake »

MR2DI4 wrote: 23/09/21 22:12 You will never get 300Hp out of the Rev 1 Turbo on the 440cc injectors
So my engine is pretty decently modified, gen2 block with gen3 efi meaning i dont have am AFM i have gen3 540cc injectors, decat, intercooler, big single exit exhaust, the bottom end if forged too so my car is well the point of being stock. Oh and a CT20 not CT26

The newer unichips seem to be able to do everything a standalone can, albeit by fooling the oem ecu.

These chips are fully tuned to the car they are fitted onto on a rolling road.

From speaking to the company that supply and tune them along with 4 or 5 of their customers these new Unichips outperform all the old style piggyback ecus and dont require the same kind of rats nest the the others did either.

The main thing i am looking for is an answer if we think it can help me out alot, obviously the gen3 efi fights with the Volumetric efficiency of the gen2 engine and as alot have said this causes super rich conditions which are fixed with standalones all the time.... which the unichip can also replicate for £2200 less.
I can't figure out how to put in an image here, so this is my cry for help. :confused1:
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Re: Is A Newer Piggy Back ECU Viable?

Post by MR2DI4 »

The "Super Rich" conditions quickly disappear when you increase the boost above the stock levels even with the stock ECU.

So the increase in power is only really coming from what is technically a "better tune" . AFR's change from 10:1 into the 12's under boost and you get more power.

There is no magic in tweaking the stock ECU really, there is a theoretical Hp limit and its pretty much all based on the size of the injectors. Doesn't matter what ECU you put in there, the injectors are the bottleneck.

Your fuel pump becomes quite important, it needs to be up to the job and your base fuel pressure wants to be at the top end of the specification not the bottom end.

There is bugger all difference between the generations of 3SGTE. The later gens get more power from a few extra psi of boost and bit of extra valve lift. Where the big difference is because of the scope for tuning, the bigger injectors.

Essentially my Rev 2 puts out the same power as the stock Rev 3, all it took was to modify the CT26 and up the boost.
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Re: Is A Newer Piggy Back ECU Viable?

Post by MR2T_Jake »

MR2DI4 wrote: 23/09/21 22:48 The "Super Rich" conditions quickly disappear when you increase the boost above the stock levels even with the stock ECU.
As ive stated in previous posts, its maxing out gauge (10:1) at 18psi boost this could easily be in the 9s for afr and does not seem to be affected by the boost I throw at it.

From reading, very common with gen3 efi on gen2 blocks
I can't figure out how to put in an image here, so this is my cry for help. :confused1:
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Re: Is A Newer Piggy Back ECU Viable?

Post by MR2DI4 »

Sounds a bit weird what gauge have you got ? does it read 14.7:1 just cruising and not under boost ?

That's what you should get when the ECU goes into closed loop using the stock O2 sensor.
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Re: Is A Newer Piggy Back ECU Viable?

Post by MR2T_Jake »

MR2DI4 wrote: 24/09/21 8:30 Sounds a bit weird what gauge have you got ? does it read 14.7:1 just cruising and not under boost ?
Yup the AFR is perfect, idle 14.7:1 cruise fluxes around 14.7:1 and under boost it will slowly get richer and richer by around 4700rpm its maxing the AFR. Its a AEM AFR.

From reading and speaking to others with a gen3 efi with gen2 engine it seems pretty standard to be super rich higher up.
I can't figure out how to put in an image here, so this is my cry for help. :confused1:
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Re: Is A Newer Piggy Back ECU Viable?

Post by MR2DI4 »

Could probably run a bit more boost in mine, its up at 17psi and the tailpipe is still a little black but probably not worth the risk for the last few Hp.
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