any problems with TB42 EFI???

[CRUSHU]

I'm looking at a GQ with the EFI 4.2, and want to know if there are any likely problems?

also, can they be turbo'd with low boost and standard computer??

[Boopa]

I'm looking at a GQ with the EFI 4.2, and want to know if there are any likely problems?

also, can they be turbo'd with low boost and standard computer??

http://www.airpowersystems.com.au/safar ... tudy1.html
I'm sure I've seen an article on a 4.2 they've done also?

[CRUSHU]

i am looking at a 4.2 efi GQ at the moment. it suffers from detonation on petrol only, under load. i also have a turbo system to suit a gq straight gas. i hope all i need to do it fit a map sensor that can cope with boost, and hopefully the ecu will compensate for the rest.
any tips for curing the detonation? if i get it it will recieve a service, and a reset of the rockers. maybe the injectors will need servicing?

BTW, i am looking at running about 6lb boost, with maybe a small air to air cooler under the bonnet.

[Dirty Dave]

I am bout to start mine on a TB42 carbie feed for the low compression and bolting on a late model efi manifold with a gas carbie, I doubt the std nissan computer will handle the boost without you adding another injector if you are still going to run petrol, I am running dual fuel and it cost a f*#k load more.....Remeber I was interested in your turbo kit a while back?? But went brand new turbo and wolf 3d instead. And a front mount.

[CRUSHU]

why wont the computer handle it?? that is what computers do, change fuel metering to suit incoming air. if more air goes in, it supplies more fuel. i can't see it being a problem unless you go big boost.

[Mytqik]

why wont the computer handle it?? that is what computers do, change fuel metering to suit incoming air. if more air goes in, it supplies more fuel. i can't see it being a problem unless you go big boost.

having tried to turbo an existing efi car before, here are some of the problems you will encounter:

1. The standard injectors will soon run out of duty cycle. The standard injectors are sized to deliver the corect amount of fuel for maximum power @ maximum load + a *small* safety factor. Easy way to check is to put an automotive multimeter which measures duty cycle onto the back of one of the injectors & take it for a hard drive. You will soon see 80-95% duty cycles appearing. If you try to use these without adding further injectors, then you will run it extremely lean & will be searching for a rebuild kit in no time.

2. When you try to add injectors you will have to run them in parallel with the existing ones. The standard computer will only be designed to drive 6 injectors not 7 or 8 etc, so you will need to put a relay inbetween the computer & your injectors. Now a TB42 spinning at only 4000rpm will fire the injectors 2000 times a minute. Now a standard off the shelf light relay isn't going to do this, so you are going to need to source a solid state fully electronic jobbie. Not expensive, not they are delicate items which need to be sealed against moisture etc.

(Note: standard computer fires the injectors twice every 4 cycles. This is so the injectors can be smaller, as they only need to flow half as much. It is also a time thing, as the inlet valve is only open for a short duration at maximum rpm, the injector fires once when the valve is closed, & then when it opens. This allows a charge of fuel to be in the inlet when the valve opens, along with the second which is fired when the valve opens). It also simplifies the electronics, as every injector is fired at the same time. Some of the more expensive aftermarket (called sequential systems) will fire injectors independantly, but for the added complexity, the gains are not worth it.

3. You said you were going to add a MAP (Manafold Absolute Pressure) sensor. WHY? What is going to read the output? The standard computer is setup (I assume here as I have never done a TB42) with an airflow meter. The outputs of these sensors are different, so the standard computer will think the Airflow meter is broken as it is pumping out the wrong signals. Airflow meters are used by 300ZX & the GTR skyline instead of MAP sensors. I would suggest you look at using a GTR skyline Airflow meter as these are designed to accept much larger flows. They also dont need to handle positive & negative pressures, but still tell the computer how much air the engine is drawing in.

4. Normal MAP sensors are quite cheap, however they are designed for N/A cars where the inlet is under a negative pressure. MAP sensors for turbo'd cars are more expensive because they need to read both positive & negative pressures. A standard MAp sensor will implode if it sees a positive pressure.

5. A standard computer has a standard fuel map. This map is programmed specifically for the TB42 N/A, no if you start stuffing way more air into the system than normal, the airflow readings will not correspond to the rpm setting on the fuel map, therefore the computer will return an error message, because in its eyes, the TB42 can not physically draw in that much air, for that rpm. So at the very minimum you will need to have your standard computer reprogrammed. This involves extensive time on a dyno, with exhaust gas analysisers etc, which all add up.

I am not trying to be a kill joy here, but just letting you know some of the pitfalls you are most likely to come across. They can be extremely frustrating, especially if your car is a daily driver & you have no other option.

PM me if you have any further questions.

Cheers,
Mytqik. (Mighty Quick)