Speedtoys

MAF today, SMAF "mater O days"

Speedtoys

Cool Rob.

Is that a "plain" GTS, or mods?


Zzzzoooom!

Rob Edwards

Its from the stroker.

Speedtoys

Full BWWAHHH is nice isnt it...

Rob Edwards

It is, 'cept I always chicken out about 800 rpm shy of full bwah. Need to see what absolute MAF says at 7000 rpm....

Speedtoys

Rob Edwards

It is, 'cept I always chicken out about 800 rpm shy of full bwah. Need to see what absolute MAF says at 7000 rpm....

John Speake

I've attached the graphs of MAF and SMAF volts measured at the input to the LH ECU versus predicted power..... as stated previously, the "MAF volts" on the ST are the volts registered by the A/D convertor in the LH which maxes out at 5.1v. But the LH also processes the MAF signal in another circuit and this goes to 6.1v.

The signal to use is MAF signal Absolute which is the same as "Load" on the fuel map.

FredR

Hi John,

So this explains the system limits of 440 hp or so on the stock MAF and your SMAF at that voltage is about the same output as an F15 correct [effectively no practical limit in the scheme of things]?

John Speake

Exactly right Fred - at the onset of the 5.1v limiting point of MAF volts, with a SMAF the crank power is approx 560HP.

However these graphs assume various constants for volumetric efficiency, fuel etc. they they are approximate.

FredR

John,

I would be a happy punter if I could see 5.1V on my MAF!

I am still trying to fathom out why on stockLH/EZ MAPs I am running are somewhat rich across the board when my WOT switch is not working. I am starting to wonder if for some reason my [relatively new] MAF is over reading air which, considering it is showing MAF values that I suspect are a bit on the low side to start with, is a bit worrying. The AFR's I am seeing on fullload [now high 12's -they were 11's] can be further corrected in ST2 more than I have done already but I am struggling to work out what is going on here.

I may try fitting my spare MAF that you calibration checked for me just to see how that works out. I may even pull the inlet manifold tomorrow and check out/replace the WOT switch. The tickover contact works fine but seemingly not the WOT contact [I read an earlier post on this a few weeks ago].

I also purchased a "balanced set of 30lb design 2 four hole injectors" recently just to see what if any impact that they may have. The part number on them when traced to some of these online injector guides suggest they may in fact be 28lb injectors- even so I suspect ST2 can deal with them one way or another.

Our air temps are starting to drop a bit now so it may be possible to collect some 30C air in the evenings. I am even thinking of going back to the stock exhaust albeit with my crossover pipe on just to make sure that is not throwing any curved *****.

I am starting to wonder if the fitment of the EIS inlet system has done more than I expected in terms of modifying the MAF signal- I may try to some runs with the stock air filter back on. The only other mod I tried was the inlet plenum spacers.

Guess I'll sort it out sooner or later- that or buy a 9** twin turbo and have done with it.

Guess it is a never ending search for the Holy Grail with these things!

Regards

Fred

If the enrtichment puzzle was not mystifying enough then given I am running a bit on the rich side I cannot understand why at full load and high rpm's I got some knocking on the std maps [around 6k rpm] unless it is a fuel type of thing.

dprantl

Um, wait... that means that when my SMAF is reading 5.11V @ 5,000RPM, I am making 560chp? I need to go back to the dyno to see what it is at 6,600RPM... The supercharger can't be sucking up more than 65hp.

Dan
'91 928GT S/C 475hp/460lb.ft

John Speake

Hi Dan, I would appreciate any real world figures from dyno, as the curve for the SMAF volts vs power is a mathmatical projection.