Honda CR-Z Hybrid Car Forums banner
1 - 20 of 100 Posts

· IMA Enthusiast
1,677 Posts
Discussion Starter · #1 · (Edited)
Tuning the Lithium cars for more IMA power.

You will have seen my long thread on tuning the Nimh system for more IMA power.

In that I hacked the current and the voltage to double the motor Kw output. It was very lively. :p

It involved swapping in a Lithium car inverter and dc-dc converter and using the cars original Nimh BCM/MCM module along with an up-rated 200A fuse.

So what can we do with the Lithium cars?

Well we can hack the current in exactly the same was as we did for the Nimh setup.
This will likely get us another 5-7kw or so. Taking us to ~20kw+...

The voltage is more tricky in the Lithium cars especially if we want to keep the Lithium control modules.

The Lithium MCM/BCM gets it's voltage data from three places.

1) The four BMS CAN boards on the pack.
2) A HV input into the BCM. (We can fake this as per Nimh with a very low current HV supply)
3) Serial data from the IPU IGBT module. (We can fake this as per Nimh)

So to tackle 1)

Can we make an interceptor type device that will send out perfect 75% SOC equivalent cell voltages on the CAN bus?
I'm saying 75% as at that voltage equivalent about 3.8V per cell the car will allow full assist and regen.

Yes I think we probably can fool the voltages, but this only gets us to around 190V which is where the OEM Lithium DC-DC and IGBT module max out.

To go higher we might need to use the HCH2 DC-DC which goes to 220V and possibly the HCH2 IGBT module which probably goes to a similar voltage.

That should get us firmly in the 30kw+ camp with a suitable battery pack.

Now to go even higher we need more voltage.. :eek:

So what IMA cars have higher voltage packs?
Do these dc-dc converters and inverters use the same data stream for control as the CR-Z etc? I bet they are similar.

So would a CRV 2019 or Jazz dc-dc and inverter work in a CR-Z????? Only one way to find out..

But before I start buying expensive parts.........

I'm going to need access to the Honda workshop manuals for these later models to check specs and wiring for compatibility.
Does anyone have current Honda subscription access to this data? Can you message me please.
If people want to support this research in some other way then feel free to message me.

Have a good Christmas and Thanksgiving etc. Peter UK

· IMA Enthusiast
1,677 Posts
Discussion Starter · #11 ·
The FSM Link for the CR-Z is useful. Thanks

In these newer higher voltage (260V) packs the inverter is up on the engine asfaik.

In the couple of CR-V ones I have disassembled here in UK the battery unit only contains the cells, battery management, contactors/fuses and dc-dc module etc.

I agree getting a complete unit might be best for most people but I have tons of spares/batteries here so don't need all the bits for a prototype test bed asfaik.

· IMA Enthusiast
1,677 Posts
Discussion Starter · #21 ·
A hunch... :unsure:

I'm following a bit of extrapolation and suspicion here but I suspect the HPD IMA tuned 30+kw CR-Z was basically using a hacked HCH2 IMA setup.

I've been studying the workshop manuals of the CR-Z and the HCH2 IMA side and the basic signals all seem to be present in the right places.
The CAN data on IMACAN & FCAN looks very similar so I am suspecting an HCH2 battery/control assembly might actually work in a CR-Z.

The HCH2 was a higher voltage setup and I know from testing the DC-DC can take 220V
(Almost double the Nimh CR-Z 100V and +50% over the Lithium 144V version)

So plenty of potential for pure voltage increase power there.

Also looking at the HCH2 phase and current sensors they might be easily fooled with some resistors to allow higher currents as well. Double whammy.

So I'm going to buy a complete HCH2 IMA assembly and plug it into my Lithium car and see what happens!
If it works I'll then increase the voltage and current.


· IMA Enthusiast
1,677 Posts
Discussion Starter · #22 ·
Just looked at the HCH2 Inverter on the bench and the U,V,W phase sensors and it does look like they can be fooled with resistors to allow higher currents.
Basically they are a 3 x 5v powered 2.5V = 0A bidirectional sensors.

The output can be manipulated by inserting a 220R resistor in series with the output and then 2 x 1k resistor pull up and down to +5V and GND on the output end.
This basically forces the signal to remain at 2.5V more strongly and reduces the voltage swing by about 30%. So for 10A flowing the inverter sees 7A.

So the inverter effectively only sees about 70% of the flowing current.

Basically it says I want 100A but only sees 70A, so has to open the gates wider to let more power through until it sees the 100A
In order for it to command a detected 100A it has adjust the phase control to allow ~140A (+40%)

If we assume a 200V system then 200V x 140A = 28kw = ~37hp

That's a nice increase and the same % as we currently run in the G1 Insight systems.
Of course we can/will likely start with lower % increases and crank it up in +5% or 10% increments until it falls over or blows up!!


· IMA Enthusiast
1,677 Posts
Discussion Starter · #28 · (Edited)
The core is split with a little 4 pin hall sensor in the gap. It's marked 9 6G

R8 (330k) and C2 are in parallel and connected to the output to the MCM main pcb.

I agree digital pots would be good.

There are no markings on the main 16 pin IC chip even under the scrapped off goo on top of it :(
The reverse of the pcb is just a big ground plane.

I'm assuming the main IC is some sort of OP amp?
Pin 1 appears to be bottom right in the pic.

The circuit appears to have some temperature compensation going on as well with VR1 & 2...
It will get quite toasty in the working inverter and the sensors could see 100C variation between below freezing and nearly boiling.

Passive circuit component Circuit component Hardware programmer Electronic component Electronic engineering

Gas Metal Auto part Machine Screw

· IMA Enthusiast
1,677 Posts
Discussion Starter · #29 ·
The 5V powered battery current sensor feeds into the BCM module and has two outputs that both sit at 2.5V when no current is flowing.
I'll have a look at one of those on the bench in due course as all the current sensors have to be in sync or the car will detect an imbalance fault.

So if we fool the phase sensors by -30% then we have to do the same with the battery current sensor.

· IMA Enthusiast
1,677 Posts
Discussion Starter · #35 · (Edited)
More cross checking and seeing what is possible today while I wait to acquire an HCH2 IMA setup.
I'm also cycling an old HCH2 pack I had in storage for the testing.

It looks like the HCH2 IMA setup will plug straight into the CR-Z wiring harness with perhaps only a minor pin swap on the HCH2 connector. (y)

If this does work then in a Nimh car it would be an immediate +50% IMA boost compared with the stock 100V pack in the early cars. ;)

· IMA Enthusiast
1,677 Posts
Discussion Starter · #47 · (Edited)
Interesting tables but I know nothing about roms. I can see a steep learning curve ahead. :unsure:

I suggest the roms dumps etc and disassembly would be better in a separate dedicated thread or this one will get very confusing.

I don't have an openport 2.

· IMA Enthusiast
1,677 Posts
Discussion Starter · #53 · (Edited)
@da-coder so how would you modify that circuit to reduce the voltage swing for a given + or - current?

My idea in the example being simulated in Proteus (used in the G1 and HCH1 and CR-Z so far) is along the line of the below.

Rectangle Slope Font Parallel Symmetry

The phase sensor is 0-5V output with 2.5V being 0 amps.
So in the simulation with 1.25V input the output is 1.66V

2.5 - 1.66 = 0.84V change instead of 1.25V

67.2% of the voltage swing is being passed through. 32.8% reduction.
67.2% would have to be increased by 50% to get back to 100% = full output.

R3 is already on the main MCM pcb so that is why I added R2 to avoid any offset.

R1 could be variable as the sensor seem to have quite a good current drive capability.
Making R1 variable with the above values would give you a 0 to +50% current adjustment range. (y)

So each sensor needs four tiny resistors adding.

EDIT To make it simpler to implement I would like to swap out the 10k on the MCM board for a 1k. Then add another 1k pull up to +5V.
This reduces the resistor count and complexity. In effect losing R2 & R3 from the above demo circuit.

Sadly though you can't access the 10k without removing the entire pcb from the IGBT modules. So that's not happening. :(
1 - 20 of 100 Posts