Cold Air Intake
 

K, another big one, I was thinking about moving my battery into the cavity that removing the giant exhaust will make, then splitting the two banks into two seperate cold air intakes, and I have some questions as I'm not very familiar with the electrical A/F methods of this car.

1) If I didn't use a second MAF on would the ECU automatically adjust the pulse width to adjust for the extra air or would the ecu have to be re mapped?
1b) If the pulse width were increased would the duty cycle of the injectors get too high (aka above 80%)
1c) Would the stock injectors be able to handle a pressure rise to create a higher fuel flow rate to account for the extra air?

2) If I were to get my hands on another MAF, is it possible to wire the two together to get a proper air flow reading? (Take into consideration this is an OBDII '97 ECU, I know LAN has this mod with his ECUTUNE but that won't work for my car and I can't afford the standalone ecu just yet)


I figured that once the car is running in a closed loop system as long as the injectors would be able to handle the extra duty, the ECU would automatically adjust to account for the extra air, changing the injectors wouldn't really help me, cause I would need to reprogram the ecu anyways because its' open loop tables would be way off.

The ECU doesn't adjust to any extra air, it adjusts to what it is told by the MAF.

Adding a second intake that large, that is un-metered would not work. I haven't dug to far into the ECU programming and how it all works but some people have talked about doubling the reading that the MAF gives the ECU. I don't see how that would work because the MAF has a fixed voltage range (0v-5v, I believe anyways) that it sends. Maybe you could half the signal it sends and then tell the ECU to read it as doubled? But this is just all guess work.....

Two MAF's could work, but again there is gonna be alot of programming behind it.

A stand-alone running speed density would be awesome, IMHO. But then you'd need a stand-alone that can run speed density, and a professional tune.



Dustin

The performance gained from running twin intakes would not offset the amount of work that would be, I'd put that effort into fabricating a single cold air intake, as that will flow more than enough, and be a lot less effort. (Won't look as cool though.)

Um, something, something, something, NO. I guess you have been looking at something like a JWT for the 300zxtt to get these ideas?

Well Thanks for the input odepaj, and Yourconfused...well negativity never gets you anywhere, there's always a way of engineering things to work, we run a speed density plot on our SAE car, so I'm sure it wouldn't be too much more work to dyno the EG33, just more mechanical work to get it out of the car and onto the dyno...wish I had a test engine :rolleyes:

I'll probably just run the one cold air intake for now, then see where i'll go from there :cool:

I ran two intakes when I was trying the best combo,mine was two tubes with conical filters that came together into a single going into the maf meter,I truly didn't gain nothing.Anyway you are on the right track by trying different things.

sorrry, didn't mean to be so negative, but i was tired and lazy in my response. I figured you would get the JWT reference though.

Hve you looked at how large the twin 2.5" t.b.'s are really in comparison to the size of the motor? the 3" maf shouldn't be the restriction as much as the basic design of the intake tractt going to the t.b.'s really, so modifying that should be your only concern.

would smoothing out the intake give you any noticable/worthwhile gain? i understand how the air would flow better, there is no doubt about that, but what kind of improvements can you expect? would it make it only sound different, or actually give you a noticable, physical (as in performance, not visual) change?

Use the search buton on Tomyx

It simply would adjust for the amount of air going through the maf sensor itself. You will not know how much more (or less) air will come through until it is measured (air/fuel ratio). Only then you'll know if the ECU is handling the intake design properly or not.

If there are such things, I'd say you would need:
1) A voltage 'totalizer'

2) Two adjustable voltage regulators.

Just making these up since I am far from an electrician.

There are heaps of assumptions of linear readings in this thread. Half the flow through a MAF does not necessarily return half the signal. Consider a temperature sender; the results there are on a curve. :cool:

For the "Hey, this would be cool" factor, you've got a maybe, depending on your definition of cool. For the "Hey, this might be beneficial" factor, you've got a maybe, depending on whether it works. For the "Hey, this provides gains that are worth the extra hardware and research and monay", I've got to be honest and say that I'll play odds against. :( If half the flow through each of two MAFs create half the signal and they can be combined, then you're in good shape from the start, but in my experience with sensors, I can't say that I'd expect that to be the outcome. Once you wind up programming a processor to produce a single signal from the two MAFs that matches the flow of a single MAF (see (1) above - spot on, K), you're where you came from, but with less accuracy.

Negativity is not defined by contradiction with justification. "A trampoline will not get you to the moon" is not negativity! ;)

not being a mechanic, i cant flame. but being a physics student, maybe i can give some insight.

someone long ago suggested eliminating the injector bottleneck in the stock svx by doubling the intake volume and doubling the injector volume.

i was planning on doing something similar to what you're thinking about. if you remove the batt and stick it in the trunk, you get a real nice cold air intake chamber. then u take another maf-to-tb intake pipe from an old svx and attach to a cone filter, drop the cone into the cavity where the batt used to be and attach it to the plastic t.b. intake box. this would probably have to be done with a dremmel and some silicone. voila, increased airflow by 200% because your pressure is halved. the MAF consequently will read 50% airflow, telling your ecu to tell your injectors to work 50% less of the time, resulting in **** performance, somewhere near 100 hp, or 50%.

so you double your injector size, say to a DET20 or whatever they call the 300z engine. you eliminate the injector bottleneck, add a cold air intake, and set up nicely for possible internals work.

http://www.electricsupercharger.com/...ock_w-text.jpg


Maybe try something similar to this?

I just thought of something around using two intakes. Let's say you have two separate intake tubes but the working maf sensor is only connected to one of them. All you'd have to do is monitor the air/fuel ratio at part and full throttle and make an adjustment via an SAFC (for part throttle) and an SAFC plus a fuel pressure regulator (at full throttle). Simple enough?

Your ECU is only reading half the amount of air since half is going to the other three cylinders, through the one tube. You can compensate for this with a fuel controller and an adjustable fuel pressure regulator if you pay attention to your air/fuel ratio and EGTs. Am I correct?

I thought about doing that too, but it's a real mechanics way of looking at it, it would work, but not very precisely. Both intakes are not going to have the exact same resistance and the maf may be reading even less than half of the air because the side with the maf would more than likely have more resistance. For a really accurate solution one would have to find a way of wiring two maf's in series in such a way that the ecu would see the it's getting twice the air.