Hi guys. Merry Xmas!

 

Hoping someone else will have installed the Doolz system and may have had the same problem. Mine is set up with extensions to relocate the filters in the stock intercooler locations (I have an FMIC so no room for two filters in stock location).

 

I doubled the injection multipler (K constant) as the air flow has been halved. It runs poorly at idle like this - despite the idle AFR being quite good (around 14:1), it seems to be hunting some of the time - a bit like an intake leak would cause, it can suddenly increase to 9:1 or drop to 18:1. It may idle happily for 5 minutes or more. So I increased K, to richen it up a bit, it does idle a bit better like this but makes it very rich when I'm on boost. I'd previously set it up nicely with a single intake, it was hitting about 11:1 on full boost. Adjusting latency doesn't seem to help either.

 

If I set K to give me correct AFR when on boost it will most likely stall when I slow down.

 

So I'm wondering if the MAF sensor is struggling to read the lower air volume at idle?? It's reading about 900mV at idle, seems to be working right..

 

It's extremely quick when on boost, just seems to be idle and low speed that's now a problem :-\

 

I suppose it's really critical that the filters are in identical condition and getting the same airflow.

 

Any suggestions appreciated

 

Cheers

H

Your best PMing John Dixon on this one, I think you need a total remap on a chip for your setup.

He will have the values if you have an AME, or send you a chip if you only have a socketed ecu

 

Hope this helps

 

Allan

Perhaps a selin jobbie would have been easier mate?

Check out this old thread.

http://www.twinturbo.net/nissan/300zx/forums/general/view/2381006/Installed-Selin-Dual-MAF-Translator-today-Big-thumbs-up.html

 

Smithy

I doubled the injection multipler (K constant)

Bit much for a Doolz set up. Think from memory you need a 70% increase not 100%

Thanks guys.

 

I'm ok with changing the injection settings, I'm using Nistune and a wideband O2 sensor to remap it on the fly. Unfortunately it just seems to be really erratic, went for a drive today and although it makes good power and idles fine on warm up, after a good run sometimes when idling it hesitates, stumbles and is generally erratic. The wideband shows the AFR is all over the place when it's doing this - I don't think it's the map or k constant that's the issue as this would be a constant problem rather than an erratic one. It's almost as though there's a bad electrical connection, too much of a coincidence that it wasn't there before the new install though...

 

70% would put my AFRs dangerously lean, 100% increase actually ran lean (and very badly at idle), I've had to set it to 150% of what it was (i.e. K has gone from 177 to 440, using 555cc injectors) to make it driveable.

 

The Selin device looks like a good idea, I'm still stuck with the extensions to relocate the filters due to FMIC being in the way though, if it needs two MAFs I'd also have to do some extra wiring as the MAFs are now at each front corner of the car.

 

I think I'll be putting my single intake back on tomorrow - bumper off again - bah! :(

 

Cheers

H

If you are running the Nissan ECU, it will be trying to sort the idle mix out and when it runs out of control range, it resets itself to start the relearn process. This is when it goes rich then starts to lean out again. Had exactly the same problem. Perhaps try this to see if it sorts the idle then go from there.

It's a Nissan ECU with a Nistune daughterboard, the code is a basic JDM MT map which I've modded for bigger injectors etc. I made some changes to increase the minimum theoretical pulsewidth (TTPMin) and this seems to hold the idle much more steady, it was dipping too low and the ECU was chasing it - TTPMin won't let it drop that low now ;) . It's still far from perfect and feels a bit lumpy at low revs and steady throttle, more driveabe than it was though...still think I'll revert to single intake, the gains don't make up for the losses overall.

 

Cheers

H