Toyota Celica GT/GT-S Tuning on the AEM Infinity

For a little change of pace I want to discuss the AEM Infinity retrofit we did on a customer’s Toyota Celica, what really prompted this change and the features of the AEM Infinity we implemented on this platform — as well as a few others that are available.

The Background

We had the customer’s car in the shop for a fair amount of time — installing the Monkey Wrench Racing turbo kit he had purchased with the engine management package. The turbo kit did require quite a bit of customization to fit, but we took care of all that and the car was ready to tune.

I spent a good 3 weeks on the stand alone ECU that was included with this package as I was never quite content with the drivability of the vehicle with the included engine management. I don’t want to name any names, but it is the “accepted go-to” EMS for this platform — with fairly hefty price tag (customer paid something like $1500 for it). Unfortunately it is not a very good EMS and is very dated — it’s comparable to running something like an AEM V1.

Did the car make power? Sure — it’s not hard to make power. However this EMS was plagued with random misfires and quite a bit of time was spent chasing the misfires (hardware, coil dwell, sync, etc) and eventually they became very rare — but not quite gone. When taking the car off the dyno and on the street no misfires were apparent — I’ll get into that more later.

After the car was off the dyno, I put in a week of street tuning for drivability — cold start, cold start driving, warm start, warm start driving, the works. The transient response that was achieved with this EMS was not remotely what I would call “great” — warm or cold. Many would consider it to be “acceptable”, but in my book if the car doesn’t put a smile on my face from the moment I fire it cold and tear off down the street without giving me weird moments of hesitation — it’s simple crap. Why? Because I work with dozens of different EMS and dozens of different platforms — I have a very intimate understanding of what “great” drives like.

And before people start questioning — yes, all the cold start, post start, throttle pump, throttle enrichment, delta tables were tuned, every single parameter that was exposed was tuned to try and improve overall drivability.

Finally we had no choice but to let the customer try the car out and see what he thinks — and we went in not at all happy with the results this EMS let us achieve.

So What Now?

Sure enough, he brought us the car back a week later as agreed to let us fit a much more modern and advanced EMS on the car — an AEM Infinity.

Before I go into the details of this EMS, let’s go into what we expect to be able to do with our EMS and how it compares to what the previous EMS (these are some basic features as this car was run at 10psi on wastegate — no boost control):


As can be seen, the basic features look quite similar (the AEM Infinity is capable of much more — including traction control and DBW), so why would the Infinity be so much “better”? Let’s look into a few bullet points.

The Misfire Issues

This is the most annoying part of the previous EMS — once we retrofitted the AEM Infinity on the vehicle, we did not experience a single misfire. The AEM was sync’d and tuned without experiencing a single misfire during the tuning session. This leads me to believe the previous EMS was having trigger sync issues and/or problems running the coils/injectors. The coils & injectors themselves were not a problem (and neither were the cam/crank sensor) as they all functioned perfectly on the AEM Infinity.

VVT-i Control

A picture is worth a thousand words. Yes it works with the AEM Infinity — just requires proper install & configuration. Not a “big deal” to get it working. And the feedback/control is completely adjustable.


Closed Loop Fuel Control

This was extremely lacking on the previous EMS — in fact I’ll go so far as to say it was completely junk. When you’re paying $1200 or more for an ECU you would expect a modern EMS to have wideband O2 control already without having to pay extra and depending on a narrowband O2 sensor — which amounts to slow feedback and inaccurate feedback (fueling swinging back and forth, etc).


As you can see, with the AEM I configured feedback well into boost (in fact the system is so fast and accurate you can run it full time on high boost applications as well).

The previous EMS? It simply didn’t have this ability — and I wouldn’t trust it using an analog input into the ECU. It’s not accurate and the EMS has no control over the O2 sensor directly (since it requires a separate controller) — so if the sensor has a fault the EMS would know. The AEM *does* control the O2 sensor and is very quick to detect a fault (from experience), and you can chose to put the ECU into protect mode if the sensor faults. Fantastic.

Knock Control

Two words: It works. Here’s a short clip from the street tuning session with the AEM while I was out touching up the car (IE: drivability adjustments, finding any spots it may knock with “real” load on the car on the street).


This is just a small glimpse at the control — we also have the option to enrich lambda during knock events and individual cylinder knock thresholds.


This was a real source of frustration with the previous EMS — 8 channels of datalogging (and not real time at that — you have to record and then view) is horrible. To use the term “unacceptable” is an understatement — the more data you have to view the better you can tune the EMS and you get a much better picture of what the EMS is doing if you have to do any diagnostics. Not enough data and you can be left chasing your tail — at the very least it takes up much more of your time as you’re stuck with scenarios of “oh I wish I had logged that parameter… but all 8 channels are already used..”.

The AEM lets you record everything. And the “on board” datalogging is expandable by the size of the USB drive you plug into it if you need “on board” datalogging. The fact an EMS company advertises “256K” of onboard datalogging is just laughable — that’s NOTHING and utterly useless (not enough data, or not enough data at meaningful refresh rates).


This was the biggest point of annoyance for anyone driving the car previous — the throttle response, transient response and drivability just wasn’t there with the previous EMS. Sure if you had a race car, you put your foot down and it worked fine. However with the new AEM Infinity installed and tuned (which I might add only took two days to fully tune on this vehicle — yes you read that right) the drivability of the vehicle soared to perfection.

No I’m not exaggerating — I could fire the car up cold or hot and stab the throttle immediately without any delay or hesitation. Off I went down the street to do further fine tuning.

The best part? I was able to deliver the car to my customer driving perfectly in every scenario. Awesome.

So What?

I guess what I can say about the faults of the old EMS lie in a couple of points.

  • Old outdated hardware.
  • Poor software — on the EMS and desktop (yes the software does matter).
  • The fuel film model in the EMS was basically non-existent or poorly modeled — this caused our drivability issues/concerns.

Does that EMS look good on paper? Mostly, yes. But looks and practice can be completely different things.

Why is this old EMS so popular? I think this mostly comes down to what select groups have learned and push adamantly on this platform — simply put they are stuck in their ways and either don’t know anything better or don’t want to try anything that could be better. It “works for them”, as I hear a lot.

However if you are looking for something better on this platform that can improve your vehicle — we have better options available that don’t break the bank.

jason_celica_aem copy