Well, I'll preface this with this is not about hondas, or really related to them at all; this is the board I post at most, and I don't know where else to ask.

Ok. My brother has a 1992 Lexus SC400. Seeing as I have the turbo fever, we were talking about turbocharging it. Mmm 4 Liters of V8TT power - sounds like a dream.
Anyways, my question deals with boost and MAFs. I know how a MAF works, but I don't quite get how factory turbo cars with MAFs adjust fuel to go along with boost. The 1UZFE (4L V8), like most (all?) Toyota engines, has a MAF sensor. Now, if I install Twin Turbos on this car, how should I go about computer control over fuel enrichment? Bigger injectors and a new fuel pump will be installed to take care of the increased fuel.
Could I use an AFC and a bigger MAF, and put it before the turbos? The only TT Lexus I've read about used the stock MAF and put it after the turbos.
I'll probably use a good old BTM or MSD Digital to handle timing, unless someone has a better idea.
If someone could help, or at least link to another site...

 

Call Gary Hein with Go Rilla motorsports @ 713-302-7969 he's done lots of SC300/400 cars with turbos

 

also try checking out http://www.clublexus.com

 

what is MAF? sorry if this is a stupid question.

 

Mass Air Flow sensor. There are two types of computer systems. Speed Density and Mass Air. Speed density measures manifold pressure and figures fuel accordingly. Mass Air sensors measure the volume of air coming in and adjusts fuel accordingly. They are very accurate, but they are a restriction on the intake tract.

Has you're buddy considered using a motec or something? This would take all the worries out of trying to wire it all up and would give you total adjustability and more power. Just a thought...

 

In most maf systems, you can install the mafs on the inlet side of the turbos and it will add the extra fuel as required depending on how maxed out the stock injectors are to begin with.

 

If I'm not mistaken doesn't Lexus use Bosch? If so look for a Saab dealer for fueling and MAF needs. Saab has a very extensive aftermarket in Europe.

 

this is true. the MAF on my car sees 5volts at around 8psi from a t25, talk about restrictive!


[Modified by javierb14, 10:22 PM 12/29/2002]

 

The restrictive part is not always true.
The old style Bosch Jetronic had a 'flapper' or door that ALL the air entering the
engine had to go around to get into the engine, this IS a restriction since the
door is spring loaded closed.

Nowadays Bosch uses a HOT film sensor to measure air MASS, basically
the shape and size of a butter knife, with the sharp edge facing incomming air.
NOT a big restriction.

The trick to setting up a MAF sensor car is keeping the sensor 'in-range'.
Like putting a 3-bar map sensor on a Honda. The sensor was designed to
see 'x' amount of airflow if you attempt to flow too much you can't measure
the air and the ECU screws-up because it doesn't know how much fuel to add.

You'll need to calibrate the MAF sensor to measure more air, typically done
by installing a larger housing, this will change the sensors range from
(0 to X) to a new range like (0 to 1.5x).

You just need to keep the sensor output below 5V so as not to
go past the ECU limits. The sensor's output is typically 0 to 5V.

If you're seeing 5V on your MAF you are probably going beyond the ECU's range
and using an RRPR to get the fuel you need at 8 psi.

For the LEXUS 400: Just re-calibrate the MAF, to run the car with bigger injectors,
then add FI. If you have enough range in your MAF set-up the ECU will
add the proper amount of fuel and you'll be all good. MAF systems don't care
about pressure, just about FLOW, as long as you don't try to flow more air than
it can 'read' you'll be fine. Also put the MAF before the Turbo and the blow off
valve, it shoud dump back into the intake inbetween the MAF and turbo inlet.
(see stock VW 1.8T stuff for example) (setup a diverter valve)

Jeffrey Atwood