A/F lean under boost BIG MOD

vins480t · Post by **vins480t** » Thu Apr 26, 2007 7:02 am

I finally got the T3 running again.

the big injectors, the upped maf and big mod ecu are in the car.
it now runs proper without boost.
when i try to get some boost 0.1 -0.3 bar it instantly runs lean.
im thinking of the external map, that it wont register the right boost.
Mart, have you got the stuff from rich telling how to connect it?
and how can it be tested?
the rest of the engine is ok. no probs anymore with always running lean.

martinholmesuk · Post by **martinholmesuk** » Thu Apr 26, 2007 11:16 pm

Try the max ron petrol you can find.

the wires from the 3bar map sensor go direct to rich mod ecu.
Johnturbo can help as i gave him the wires and the ECU.

you have volvo 740 v6 injectors?

JohnTurbo · Post by **JohnTurbo** » Fri Apr 27, 2007 7:29 am

Haha! He did indeed. I also have some bosch 804 injectors and a t25.

I have no idea how its wired up though, and am lackin the 3 bar map.

vins480t · Post by **vins480t** » Fri Apr 27, 2007 7:35 am

Thanx
yeah i have them 740 injectors

the ecu has 3 wires. a green and a gray witha dubble core red and copper.
these have to go to the map. and the map has to be grounded to the injector ground.

i use 105/110 ron fuel now (98 and ron booster) but it hasnt got to do anything with that.

martinholmesuk · Post by **martinholmesuk** » Fri Apr 27, 2007 9:49 am

crazy... After my MAF failed I changed to a standard MAF and it still worked. Rich said that would be ok because of the injectors being the correct ones.

try new maf

vins480t · Post by **vins480t** » Tue May 01, 2007 12:34 pm

How did you change the map then?

ive tried all sorts of maf's
the bigmod, the original (93 to 95)
non of them make any difference.
it will lean out at any boost

martinholmesuk · Post by **martinholmesuk** » Tue May 01, 2007 9:59 pm

errrrm with a supermod the ecu has wires to connect onto 3bar map sensor.

i know for a fact that a supermod will not work right without a 3 bar map sensor.

vins480t · Post by **vins480t** » Wed May 02, 2007 7:15 am

I know, thats what i mean.
ive got the 3bar map sensor connected directly to the ecu. there are 3 wires to connect it.

RPruen wrote:Wiring details:

Map sensor:

Green: +5V from ECU Terminal (a)
Copper: 0V signal earth from ECU (b)
Red: MAP Signal to ECU (c)

Note: The fixing lug with the metal eye MUST be electrically connected to the engine-lifting eye or any other position on the engine. DO NOT connect it to the bodywork, or battery earth lead.

Adjust the full range pot on the MAF (access Via a small hole on the air intake end of the MAF) turning the pot clockwise reduces the mixture, and turning anticlockwise increases it.

I have done all the above to set up the big mod.
for as far as i can remember i connected the colors to the numbers correct.

Can i use a normal mod ecu with the inbuild map to test the injectors and MAF?

haz@nocturnal_development · Post by **haz@nocturnal_development** » Sun May 13, 2007 4:37 pm

the maf reads from 0-5 volts, the map sensor just has more refined points on the fuel map, still workin with the 0-5v readout from the maf tho.
have you tried usin the original maf??

rpruen · Post by **rpruen** » Sun May 20, 2007 9:00 pm

vins480t wrote: I have done all the above to set up the big mod.
for as far as i can remember i connected the colors to the numbers correct.

Can i use a normal mod ecu with the inbuild map to test the injectors and MAF?

Yes you can use the normal ECU to test the MAF and injectors.

You will need to connect the vaccum hose to the ECU, but that should be all.

The MAP sensor will not effect the mixture at all, so you can rule that out for a start.

It sounds like you need to increase the mixture using the adjustment on the MAF. At idle closed loop control will correct the mixture, but it could still go lean at higher load.

The adjustment on the MAF has more effect at high load (with high airflow) than at idle. The CO adjustment has more effect at low load (low airflow). This gives you a zero and span typ adjustment of the MAF, so you should be able to set the mixture so it is ok at idle as well as at high throttle.

Hope that helps

Richard

rpruen · Post by **rpruen** » Sun May 20, 2007 9:05 pm

haz@nocturnal_development wrote:the maf reads from 0-5 volts, the map sensor just has more refined points on the fuel map, still workin with the 0-5v readout from the maf tho.
have you tried usin the original maf??

The origonal MAF will not work (it would run far to rich). The output of the MAF is reduced, to take into account the bigger injectors. The mixture can be adjusted using a screwdriver.

The modified MAF can measure much more air before it reaches 5V on the output, so the ECU with bigger injectors can see the higher airflow.

Richard