slow throttle repsonse and engine shuttering
 

I have a PFC to control my rebuild engine:

engine specs:

- Judge ito large streetport
- full non seq turbo's running no boost for the moment because of rebuilt
- OEM injectors
- double throttle removed (thermowax and butterflies removed)
- all emissions gone


The car is idling pretty fine but I can't tune idle on the PFC. i have it now down to 1000rpm stationary and it's stable.

when I slowly tab th throttle, the revs go up as expected. when reving to fe. 4000rpm, I go of the throttle and tab it again to ga back to higher revs the engine shutters and moves the car. It feels like it floods or something. Sometimes the engines dies, somethimes it recovers.

When I rev the engine , go off throttle and very gently tab thorttle again it wil almost not do this.


I was told to adjust the values in the FC 'setting screen' under REV/IDLE (the 3 values under rev limiter rpm) because those values indicate at what rpm theinjectors should be activated again.

I plan to check the following things as well:

- try another throttlebody
- replace air temp sensor in UIM
- replace one way valve near MAP sensor.

any other suggestions are more than welcome

Thx

Too many unknowns!

You need to fine someone who really knows how to tune the PFC, and knows the FD.

The stock mapping in the PFC is not adequate for a large port engine that is muffled by stock turbos that will be limited to boost around 14psi due to small injectors.

Your setup is currently very mismatched.

First off start breaking the engine in. Dont worry about what it does free reving it. The base map is fine for break in as long as you are not in much boost.
Only thing you need to worry about on the PFC are the injector settings right now. As long as those are correct it should run fine in vacuum.
Once its broken in then find a reliable tuner.
You can also bump your Decel up so it doesnt stall.

boost is closed for breakin and untill I get my wideband hooked up. For teh rest I don't rev over 4000rpm.


Everything on the car is stock except for the non seq twins, the PFC and separate oil feed for the OMP (PCV adapter)

Next is a wide band (Innovative)


I t just wonders me that when revs fall back from being revved, the engiens finds it difficult to pick up again in the low revs (1000_1500rpm). Only when you really tab the throttle gently it will pick up without bogging.

Just one thing that might be of use... My PFC is not showing any knock number...

Just bump the decel up or peg the idle from the throttle body.
Knock sensor wont make a difference in the way the car runs.

Hi Jason, I appreciate you chiming in but I'm in europe and though, my technical English is quite OK, I don't really get where your reffering to. Could you be more precise abotu which menu/field?


Many thanks
Neal

Download the map, zip, and post it here.

List all engine mods.

I'm still on the PFC base map. I only adjusted the idle settings in the PFC to 900rpm (no electrics, no AC), 1000rpm (with electrics) and 1100rpm electrics and AC.

For the rest I disengaged all functions except for the idle control.

current mods are:

- new rebuilt engine wih Judge Ito aggressive streetport (big)
- PCV OMP adapter
- no emissions
- no airpump


coming soon:

- Trust 80 mm downpipe, double 60mm midpipe (silenced) and catback
- datalogit,
- Innovative wideband
- 1300 or 1680 cc sec injectors (when going to higher tan 10 psi of boost)


Engine still has OEM flywheel


Basically I'm not looking to get the car streetable for the break in period (no boost) and afterwards to upgrade to 10 psi of boost. When the bigger injectors are in, I'll turn up theboost again.

I know I need to get it tuned, and it will, but I just want to get it running an a safe basis.

Thx
Neal

As per the manual: each idle speed has an associated Fuel Cut setting. They should be set at minimum 200 rpm higher than their idle. I prefer 400 higher.