You asked for it. You got it.
Since the other FI threads are either for dead product, defective product or aimed at one particular issue or another, let this be a place to talk about the semi-on-topic stuff that clogs those threads.

The topics du jour have been:

1) MAF range/tubing size
2) Idle bleeds
3) JAB/OMP bleed

etc.

 

wouldn't it just be easier to create a thread for each of those topics and then link them all back to one "FI miscellaneous" thread page?

trying to throw a bunch of topics in one giant thread is just going to make searching that much harder than having clearly titled threads devoted to specific topics.

 

Those threads already exist on their own.
This thread is to tie them all together to practical applications.
We have 1/2 dozen or so FI options on the market that all have to deal with these issues.
This thread is where we put them to the test.

 

I have Pettit S/C.

If I needed to go to a larger tubing size which I think I may, would I ever need to go to a larger MAF sensor?

 

Great job guys!

Which hoses already have check valves in them and which ones need check valves added?

 

The OEM MAF sensor has a voltage range of 0-5 volts and is mounted in a 3-3/8" id tube. When mounted in a pull-through setup it is estimated to reach it's maximum 5 volt reading at around 47 lbs/min of airflow.

 

Given the constants in the this thread it works out to be an estimated 391.7 horsepower at the crank.

 

As is pointed out here and elsewhere, the MAF is good to about 400 HP in a draw-through setup (like you have).
With the flash recalibration you are using (and the idle air bleed that is associated with it), you will probably be good out to 450 or more since a fair amount of air is diverted around the MAF in the Pettit system.

 

a question from a beginner. The mop line. I was advised by someone much more knowledgeable than I to place a check valve on it also. Seems like the seals at times in the nozzles themselves are not up to snuf and on FI can actually bleed backward? i hope i am explaining that correctly. It was said that actual air bubbles in the mop could be seen going the wrong way. That means no oil available for injection?
Theory?
oldscdragger

 

Quick question...never really thought about this...and just so I don't clutter up the train of thought...

The voltage seen by the PCM is what is important correct? Based on the voltage and the ID of the tube (obviously being calibrated) you then determine the amount of air?

Correct?

 

Would it be allright if I took some pictures of my setup (particularly the routing of hoses) and asked some "newbie" technical questions?? I've been running F/I for @4k now and am still not completely sure about which hose does what, or purpose that is served.

If this thread isn't the place for that, could someone direct me to the right location??

 

Try creating a new thread...asking in the title for FI help...that way we keep this thread clear...

Don't worry ppl will respond...

 

Sounds good to me--probably need to identify what FI system you have?
oscd

 

The nozzles each have their own, integral check valve. If they are functioning properly, an additional check valve is not needed.

Yes. The MAF will determine the amount of actual airflow based on the voltage when passing the air through the OE tube.
By scaling the tube up in size, you increase the amount of air that would be needed to make the same reading.
Scaling the tube down would decrease the amount of air needed for that voltage.
Scaling the tube has other consequences - such as accuracy of the sensor and sensitivity.

Definitely the right place for it.
If you do it in the Pettit threads, I'll get excoriated for trying to answer them.

 

Hey...less opinions...moar answering twinkie's questions...don't make me take your gruel away!!

EDIT: MM answered...I guess you get your gruel...

 

Yes there is another oem check valve on the uim. If it was me i would purchase a better ones.
The maf voltage is only important if you are using it to run the engine? Those of us with the Int X really dont need the maf to run just the engine--correct?
It would be interesting as how the maf toward traction control etc is reacting when the int x is used and a smaller than oem intake is applied.
What are suggestions/theories out there about the vacuum hoses and a drawn through system?
thought on the VDI also?
oscd
i

 

Ok...so far so good then...let's play the hypothetical game...i'll play the role of the idiot...

outside of the complications...

could you not run a dual tube/maf solution and simply take the combined readings?

dual smaller tubes would keep the accuracy and still increase the capacity...

 

Agreed MM on the omp seals--but it seems they go bad fairly often. A second check valve is just insurance.
Good thread.
oscd

 

I like this thread.

Thanks Ray and Jeff it all makes more sense to me know.

Basically with the right tune I should be able to go with a smaller pulley for more boost and still be in a safe range for the MAF to be working properly.

 

You should still be in a safe range for the MAF but you need to make sure and keep your air temps in check. That may/may not be possible with the intercooler that ships with the kit.

 

The PCM uses the MAF to compute load. Any system that is load-dependent would want to see good numbers from the MAF.
Early adopters of the Pettit systems lost their traction control and their auto trans shift authority because the MAF was excluded from the installation.
I don't know how accurate those numbers need to be for those systems, but seeing as how closely calibrated everything else on the RX-8 is, I can't help but think there is some functionality being lost by having the MAF show bad/inaccurate numbers.

Well, draw through is, in my opinion, the only correct way to use a MAF-based system like the '8. You can do a lot of compensation with a hybrid MAF/MAP, but the loss of resolution on a blow-through system is a big problem for me.
Most of the vacuum driven accessories on the '8 are attached to check valves and vacuum reservoirs, so where they get their signal from isn't too important, as long as they get vacuum often enough to function.
The VDI and SSV require vacuum to drive their actuators, but they can be opened and closed a bunch of times on the vacuum held in the reservoir, so unless you are only driving in boost (wouldn't that be fun) you will "recharge" those accessories pretty regularly.


Its possible, but you would need a system that can integrate the two results and you would have to come up with some crazy plumbing.


Yes. Probably worth looking into as I have failed several of these over the years.

Yes, but remember, with a positive displacement blower, if it is properly sized for whatever RPM the kit is designed, going up in RPM will have very quickly diminishing results as the adiabatic efficiency of the blower (which is already pretty low) will take a nose dive and, although you might see increasing manifold pressure, you will actually be seeing less flow as the temps will skyrocket.
You can mask that with meth, but that is a very dangerous (and pointless) game.

 

Oh I understand and I'm not saying it should be used or anything...just wondering if it would even be possible I guess...

 

k...heh...thanks...

EDIT:

In a FI application, what is the relation when it comes to the distance between the filter's location and the turbo itself...

 

The Skyline and the Sylvia both used double airflow meters in their OEM JDM configuration.

 

Pretty insignificant. As long as you do not create pumping losses by making the tract too constrictive or convoluted, the length will have no effect.
The air in an FI system is moving at hundreds of feet per second.

That is why I laugh when people talk about "lag" caused by the intercooler plumbing being too long.
Its about volume, not length.