Stock jap injector duty cycle with high air mass but low pressure.

[carl0s]

We know, thanks to Ian C's observations, that the Jap ECU goes all-out on the injectors when it sees more than 1 bar of manifold pressure.

 

What happens if you had a single turbo, so you had a large mass of air but the pressure was still within the stock system's range (0 - 0.99 bar)?

 

Has anybody measured the reactions of the stock fuel system to differing levels of air mass? If I went single-turbo, I could just use an A/F meter and see if everything's OK, but it would be pretty dangerous raising boost until things started to go lean. I envisage that with a 58/60 sized turbo, I wouldn't be exceeding 0.9bar or something, so would be within the stock fuel system's sensor-reading range, but the air density would be much higher than with stock turbos.

 

I'm a little mystified because I've just read about how MAP systems work, and it seems like all MAP does is provide a way of coming out with a MAF measurement. So why not just use a MAF sensor in the first place?

 

From what I read, MAP systems measure manifold air pressure and density (which is inversely proportional to the air's temperature) and refer this against an engine speed map which tables how much air the engine gobbles up for a given rpm, the end result being a calculation of mass air flow, according to Wikipedia.

 

So why would people want to change from MAF to MAP, i.e. with a MAP2 ECU ?

[michael]

The MAF is restrictive at higher power levels, you can get aftermarket ones that are better than the Toyota one in this respect but I don't know of anyone who has tried alternatives on the Supra.

 

http://www.granatellimotorsports.com/images/artlr/350111small.jpg

 

(Granatelli items)

 

With the MK3 Supra you can get a MAF converter that lets you use a less restrictive GM MAF but again I don't know if you can get anything like this for the MKIV

 

http://www.maftpro.com/vstinfo.shtml

[carl0s]

The MAF is restrictive.

 

Is it a flappy type MAF rather than a wire then?

[michael]

Is it a flappy type MAF rather than a wire then?

 

If memory serves me right the UK has a MAF that looks like a an egg suspended in the middle of 4 plastic blades, I may be wrong though

 

Not sure what the VVTi cars use.

 

Edit: I think this is a Supra MAF on the right:

 

[carl0s]

Ah, I see. Thanks!

[carl0s]

you can get aftermarket ones that are better than the Toyota one in this respect but I don't know of anyone who has tried alternatives on the Supra.

 

http://www.granatellimotorsports.com/images/artlr/350111small.jpg

 

(Granatelli items)

 

Those are the wire-type that I was thinking of. Apparently another type is a kind of flappy thing, like a potentiometer that is turned by the moving air. I can see this type being restrictive.

[michael]

Those are the wire-type that I was thinking of. Apparently another type is a kind of flappy thing, like a potentiometer that is turned by the moving air. I can see this type being restrictive.

 

My old MR2 had one, an AFM or Air Flow Meter, the later cars have MAP.

[Sean1933]

Those are the wire-type that I was thinking of. Apparently another type is a kind of flappy thing, like a potentiometer that is turned by the moving air. I can see this type being restrictive.

 

Your thinking of the vane type airflow sensor. These will not work well when increasing inlet pressure as they reach their maximum (100% open) quite easily as they are setup to give the best resolution for the stock systems.