Rx7carl

Heres the info I promised. First lets start with the MAF. It flowed better than I anticipated, but with some tweaking Im sure it can be improved. I used 20.3"/H2O as the test depression (same as for a 4bbl carb) just so you have something to compare it to.

MAF- 352 CFM's. Not bad for the crappy design. Some work with the grinder should yield better numbers, we'll see. Thats flowing it without the inlet pipe. I made a radius guide to try and get the most I could out of it. Anyway, I do see room for improvement. If anyone wants to step up and loan or donate the section of intake thats prior to the MAF, it would make for a more accurate study.

As for the TB.

Stock- 445 CFM's

Modified- 540 CFM's.

Whats the mods? Well I'll list them out.

The shafts were halved and then further thinned to be less of an inpediment to flow. Also low profile round head screws with no threads sticking out the other end for the same reason. And the last thing is the iron base. The bores are actually smaller than the aluminum body bores, leaving a nasty step in the flowpath. 2 ways to solve this. One is bore it out and make new butterflies. Not gonna happen. Way too much work sorry. Other solution was to chamfer the top of the iron plate and trim the gasket so at least theres a smoother transition from the body to the base. And apparently it worked. Thats all for now. Stay tuned for the next installment of "As the rotor spins"! Or, "how we got the MAF to actually flow a decent amount of air"!

Rx-7Doctor

iTrader: (13)

I'm sure you meant to say AFM instead of MAF. Sorry to correct you on the nomenclature of Inj. lol. When you are referring to the ducting between the AFM
and the throttle body. Are you referring to the stock inlet tube? And if so how are you going to modify that.? I just remove all of it up to the T/Body. Leave the adapter to the T/Body and run pipeing (3 inch) between that and the AFM. Then
drill and tap the pipeing and relocate the Air temp sensor. rx7doctor

LongDuck

Great information for those of us who want to stick with the stock intake system. Thanks for posting - I'm very interested in the end result.

On a somewhat related note; I've always wondered what airflow improvement there would be in replacing the stock rubber airpipe (from MAF to TB) with a polished aluminum tube of the appropriate ID? This should help to get a straighter path to the TB and might even reduce some surface parasitic drag inside the pipe.

What do you think?

smnc

Am I on crack or:
MAF = Mass Air Flow sensor?
AFM = Air Flow Meter?

Isn't that the same thing with a different name?
Like EFI or EGI?

Or ATM and ABM?

gsl-se addict

iTrader: (3)

^You are right on the acronyms. But basically, the AFM and MAF measure the same thing (amount of air entering the engine) but in different ways. Here is a link that tells more about them in detail:

http://www.autoshop101.com/forms/h34.pdf

Carl: Glad to see that you got numbers on that AFM I sent you. I don't have an extra intake box or inlet ducting, but if I find one I will let you know. Good luck with the modifications. It is very interesting.

Kent

Rx-7Doctor

iTrader: (13)

Carl i have one that i can loan you along with the stock air intake box.
Wouldn't the gain be better off measured with pipeing and a cone filter though?
Let me know if you wnat me to ship you the parts anyways for testing purposes.
rx7doctor

steve84GS TII

Very interesting Carl,but I have one question.....

For arguement sakes,say at 50% open,the AFM passes 150CFM and sends an ouput signal of 3 volts. If you increase the AFM's ability to pass air by porting it,its still gonna send the same 3 volts at 50% open,but could now be passing 180CFM of air.With more air passing through,but the same voltage output would the mixture not go lean?

smnc

There's a thought... my -SE runs to rich anyways...

rotarygod

iTrader: (1)

Carl when did you get a flowbench? I love mine.

You can improve the stock afm but you don't necessarily have to grind it out. Only a little bit. I actually added epoxy to mine in areas to improve the flow. I don't remember the flow numbers but anymore but it was improved.

This may sound backwards to making power but instead of using a 3" pipe between the afm and the tb, use a 2.5" pipe. You'll need to do some epoxy work to the afm to allow it to mate up to this in size. You're just going to have to trust me on this one! You will need an expansion cone to mate up well with the tb. Make sure the inlet side of the afm has a nice radius on it somehow or use a cone filter that has one.

Try this. Flow the entire assembly as one giant unit on the bench. Make the mods I just mentioned and do it again. Rather than testing only one area at a time, flow test as much as you can. Only address the area that need it. In other words, the restrictions first such as the afm. The tb will increase the throttle response but it won't give you more power. There isn't any power to be had from touching the intake manifold unless you want to ditch the auxillary ports. Remove the sleeves and rods from the airstream. Just leave them all out. Don't worry about a radius at the end. You'll gain a whopping cfm of flow (depending on your test pressure) anyways. Obviously you'll lose low end though. I kept mine installed. That's about all you can do until a standalone is used. I have one of those now too btw.

It's nice to see someone else flowtesting! You'll learn alot really fast.

karism

Very Nice Mr Carl!

hehehe,this proves that the GSL-SE`s injection is NOT as bad as everyone says it is.I allways thought it would be better than anticipated.

karis

RX7Rox

very good info here....another thing I was thinking about, for those of us still running the smog pump....Isn't the T/Body and smog pump fighting against each other using the same source of clean air from the stock airbox? Seems to me it would act as a restriction.
Granted most of you have already ditched the pump and stock airbox, but would think removing the smog pump tube from the airbox and using a mini-filter would be a cheap mod if there was anything to gain.

Rx7carl

Thanks Doc, yes I meant AFM. Sorry about that. <embarressed> LOL. No actually I meant from the box to the AFM. But Id love to see play with the rest of it too.

LongDuck, I havent seen the rest of the system in hand so I'm sorry but I cant speak intelligently about it. I assume that the inside of the tubing isint convoluted but is rather smooth?

gsl-se addict, a big thanks to you for sending me the AFM. Ya'all owe him for this.

Doc, that would be great. It would give me a better chance of studying it in its entirety. Not sure, I havent had the chance to see the stock unit up close and personal.

Steve, good point, but what tunes the fuel curve? Isint A/F used in the fuel delivey schedule of the computer? I thought that A/F as measured by the O2 sensor was the primary input once it went into open loop? Sorry again old boy, Im not that hip on EFI stuff. Im kind of a dinosaour.


rotarygod, Ive had a flowbench for over like 2 years. I built it myself. How do you think I have measured our carbs vs. the stock one? BTW- the Sterlingcarb now flows 465 CFM's! We've reached the end of the development of it. It's now equal to the Holley. Much thanks goes to Sterling for his brilliant ideas on getting us there without boring out the venturis anymore so as not to lose precious velocity! Hope you enjoyed that 20 year old scotch I sent ( I lost a bet, he was right, I will eat crow and admit defeat. ) I agree, its not all about necessarily hogging out the AFM, but more smoothing of the flowpath. I'll post results when I get to it. Hmm havent messed with the AFM to TB pipe, but I like the idea of an expanding cone to control the flow and velocity rather than a big *** 3" pipe connecting the two.

Whew, Id love to flow the ting as a unit, iron housings and all but I dont have those in my possesion. I have only the AFM now as the TB and UIM went back to Hector. You dojnt think a radius (ala pineapple) will help with the transition? My gut tells me they would work. And as far as seeing real fine changes I like 28"H2O. Having studied Smokey's work I believe thats the magic point.

Oh believe me Ive learned a bundle in the past couple of years. Anyone who does this kind of work and doesnt back up their claims without a flowbench sheet is full of it. It's certainly not all intuitive as you so well pointed out.

Karis, funny how it showed to flow so well eh? I didnt think it would either.

rox, I cant answer that sorry, Im just not that familiar with the SE system.

steve84GS TII

Im no Guru on modding the stock EFI,but from what I understand......
The AFM is the primary measuring tool for determining fuel injection.The TPS provides instant info to the ECU about "demand" from your right foot.The boost/MAP sensor provides info about how fast the engine is drawing air after the throttles(manifold vacuum depends on RPM and throttle position)....but when it comes down to measuring the amount of air that is being drawn into the engine,regardless of RPM or throttle position,it all goes through the AFM first.

The O2 sensor is really just for fuel economy when cruising and low RPMs.Thats why the engine will still run fine if the O2 sensor is unplugged or wasted,its just "fine tuning" device on our cars.On later,OBDII and speed density type EFI the O2 sensor is more involved with the fuel delivery since there is no AFM and/or emissions are more of a concern.

Rx-7Doctor

iTrader: (13)

Carl the inside of the inlet tubing from the AFM to the T/body is ribbed. This is done as to quiet the air flow noise from the factory. It would be quite difficult to remove that inside ribbing. Much easier to adapt pipeing from the AFm to T/body. Auto zone is supposed to start carrying fabrication kits made from Spectre with all the necessary adapters and pipeing to make jusst about anything.
Rox. The flow of air to the air pump is so minimum that nothing would be noticed
by eliminating the hose. The biggest restriction is the stock air box and AFM.
Carl, i wonder what would the gains be with your improved Afm and the S4 t/body and induction system on the SE.
I have run the S4 T/body and induction system but with the stock se AFM. It did seem to run very well but with a modified Se AFM and some tinkering with the internal adjustment of the AFM, Who knows? Worth a shot. I'd like you to modify
My se AFm for flow then try it with the S4 system.
As far as the o'2 signal on the Se. It's only inputed when in 5th gear.
As far as my experimental porting of the stock Se induction system. I took almost 3/8 inch of metal from the runners and matched everything. It pulls alot harder at
higher rpm's than it used to even after i removed the header and put on the cat replacement pipe. rx7doctor

riceburner1r2001

iTrader: (4)

how did u port the whole intake runners. what kind of tool cuz thats a long runner i dont know what tool you would use.

Rx-7Doctor

iTrader: (13)

An extended shaft that i bought at osh/sears. rx7doctor

riceburner1r2001

iTrader: (4)

did u also port the part inside where its says rb-egi