Advice on hesitation & Piggy Back ECU/Redom/ any non standard fd ecu

[m4drx]

hi guys need your advice please,

can anyone advise if a piggy back ecu/redom or anything cheaper than an apexi hlp me?

i have an aftermarket exhaust & intake and i am experiencing some hesitation/bucking but its intermittent another symptom is that boost is good in 3rd 4th but feels like it is going lean at high rpm in the lower gears and even the higher.

this bucking/hesitation has begun to lessen with work to a few pipes in the nest & check valve replacement and spark plug replacement however still present.

however when a apexi pfc was plugged in running a rich base map (with no alteration to ignition etc) this went away...?

would this point to a vacuum leak perhaps or is this a fueling issue?

if i bought one would this also be able to safely support more mods such as a decat?

any help would be appreciated.

i would have posted in the wanted section because although i cant really afford an apexi i thought i could afford a piggy back or redom but i was made redundant yesterday so im not even sure i may even have to sell the rex.

[Grizzly]

This is Simple, First if you have it Put the Cat back on, This will help your Spike/Creep Problem.

Then get enough Cash together for a Power fc then refit the Decat and have it set up properly, I don\'t want to sound off but Piggy back ECU\'s are not worth the money (there are not many people that can set them up properly on a Rotary)

I would not think about doing it anyother way becouse Rotarys WILL bite you in the Wallet if you run them Lean.

[m4drx]

cheers griz, it actually has standard cat etc and a hks super dragger exhaust fitted. I\'m just looking for a way to make sure its not running lean.

i know an apexi is best by far but i couldnt afford it including the commander, fitting and mapping.

do the guys using these piggy back systems and redom ecu\'s have mods etc.

i have a greddy E-01 so i can see a boost graph and it is not spiking but sometimes when i put my foot down however hard it hesitates and other times its ok. is that boost creep?

[Grizzly]

If you have a E-01 just set it to stock boost, If its like my Profect B it won\'t let it over Shoot the Target Boost.

Alot of the Redom\'s and Piggy back\'s where fitted in Japan so even before they hit the road alot of people remove them and Fit PFC\'s its realy not worth the Risk (you don\'t know what most of them have been set up to?)

If you just have an Exhaust and E-01 as long as you have not turned up the Boost you should be fine.

Out of intrest Do you still have the Air pump fitted? and have you Changed the Plugs recently?

[m4drx]

what is the standard boost exactly? i had it set to 0.65 bar previously but i was told the 4.5k changover wont happen unless it makes more than 11psi or thereabouts which would be about 0.74 right?

but if this doesnt solve the bucking have a feeling it may not because of when it was set at 0.65 then is there anything else i should be looking at? i do have a large re-amemiya intake on it

[m4drx]

didnt see that last line griz, it does have the air pump and i did the plugs on saturday, what do you think?

[Carl]

Hi Tariq,
Why don\'t you sell the boost controller and get the car back to the stock ecu controlling boost if you want to save money.The stock ecu along with a catalytic convertor on the car is quite capable of controlling the boost,when you have sorted out the other related boost control issues that you have.


Regards
Carl

[m4drx]

i fixed the boosting issues and now both turbos work and changover fine, just slight intermittent hesitation so i\'m sure this has to do with fuelling etc to be causing the problem as with the apexi it went away.

however as we all know sometimes you can compensate with extra fueling for example without actually tackling the problem, if this is the case then i assume it will either be a small vacuum leak, leads or underfuelling due to induction and exhaust. if i set the boost controller to normail parameters it should neither help  nor hinder this as i have tried running 0.80 bar/12 psi and 0.65 with no difference either way to the intermittent hesitation.

im not sure this is about boost necessarily as it boosts perfectly sometimes and esp in higher gears where im guessing the ecu can handle the fuelling better as the boost and revs are more gradual

[Carl]

Be very careful with the stock ecu.
They are not able to detect over a certain boost level and add fuel.
The stock ecu just knows that it\'s map is fixed for the conditons of a stock setup. That is why cars blow up with too many mods. The after market boost controller is probably most of the problem,let the stock ecu control everything,that is what it is designed to do in this instance.
Regards
Carl

[Grizzly]

Is the E-01 the same as the Profect (if you turn it off everything returns to the control of the ECU)

[m4drx]

well i realise getting rid isnt going to help me in any way anyway, but i think grounding could bemy problem according to this; what do you think? -

Good grounds are important because poor grounds cause voltage drop. The consequence of this voltage drop is that the systems in that circuit can malfunction. How do bad grounds cause voltage drop? Well, the answer is Ohms Law.

Ohm\'s Law states that V=IR. This means that the voltage drop (V) is proportional to the current through the circuit (I) and the resistance (R) of the resistor (or bad ground in our case). An easy example is attempting to draw 10 amps through a bad ground with a resistance of 1 Ohm. So V=10(1) thus making the voltage drop a whopping 10V. This leaves only 2 volts available (in a standard automotive 12V system) to power the circuit and means that all that extra power must be dissipated as heat at the resistor (bad ground). Generally this heat makes the condition even worse, causing more voltage drop and more heat. In the most severe cases the ground will function under light loads yet fail under high current draws causing what appears to be an intermittent failure. Many people have seen this behavior caused by a loose (high resistance) battery terminal.

In a car with a relatively modern fuel injection like the RX-7, the chief problem associated with poor grounds is that sensor readings can be effected. All the sensors in the RX-7 are ground referenced meaning that the ECU passes a current through them to ground essentially measuring the voltage drop across the sensor and using it to adjust engine parameters. If another resistance if introduced into the circuit this value changes and thus the ECU sees the wrong sensor reading. The ECT (Engine Coolant Temperature) sensor/water thermo sensor, IAT (Air Intake Temperature) sensor, TPS (Throttle Position Sensor), pressure/boost sensor, atmospheric pressure sensor and AFM (Air Flow Meter) are all essentially variable resistors with the ECU on one side and a ground on the other (this is a great simplification but good enough for our purposes). The O2 sensor and knock sensor both generate their own voltages but are still connected to ground on one side with the other wire feeding the ECU through a shielded conductor. These sensor errors can cause all kinds of drivability problems that range from the common 3800 RPM hesitation, bucking on decel, poor performance or even sporadic CEL (Check Engine Light) illumination.

Aside from fuel injection issues, bad grounds can cause poor performance in almost any circuit. Voltage drop can manifest itself as dim headlights, one circuit malfunctioning when another is switched on (a common symptom is that the heater blow slows and dash lights dim when the brake pedal is pressed) and all kinds of other random weird issues.