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Discussion Starter #1
I'm about to embark on building a turbo kit for my 00 GT-S. I finally finished the kit for my S14 so I can swap that for my daily driver.

Have any of you guys tried the Hacked MAF setup for running larger injectors? It would be a very cheap way to run larger injectors and I know for a fact it works on the Skyline/240/Silvia/180. Any thoughts on this?

Thanks in advance...

Brian
 

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I have not heard about hacking MAF.... If you are able to get some info or a link as to how they do it I am sure there are people here who are technical enough *wink* Boosted 2.0 *wink* to know if it is workable :D
 

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Discussion Starter #3 (Edited)
Here's a better explanation. I guess I should have posted this up earlier. This is a common mod in the Nissan community. Bare in mind this is for a 240SX.

The theory:

To run bigger injectors without an S-AFC or upgraded ECU on a KA24DE turbo, you can 'hack' your stock Mass Air Flow Sensor (aka MAF) to sneak a proportionate amount of extra air into the motor to match the extra fuel being sprayed due to bigger injectors.

If you want to run bigger injectors (say the 370cc side feeds form an SR or Z32 TT motor) you need to compensate somehow, otherwise you'll run VERY rich, and have poor performance.

The easy ways to accomplish in the past was to get an Apex'i S-AFC, which is a piggy-back controller that alters the airflow meter signal before it gets to the ECU and tricks the computer into spraying less fuel as desired...

To understand how this works, you need to understand how the Nissan MAF works - It has a hot wire in it that sees a cerain voltage. As air passes over the wire, it cools it, and the ECU sends more voltage to try and keep the wire a constant temperature. Based on the amount of voltage needed to sustain a certain temp, the ECU determines the total mass of air entering the motor. But it works based on a few assumtions, one of which is the cross sectional area of the MAF tube.

So if we increase the cross sectional area by some percentage, we get that much more air entering the system unmetered...so it can compensate for the extra fuel being dumped by the larger injectors.

An example:

370cc injectors are 37% larger than stock [270 * 1.37 = 370]

So we need 37% more cross sectional area in the MAF tube to be close to being "calibrated"...

Remember, the area of a circle is [ Pi * radius^2 ]
So we need to know the stock S14 KA MAF inner diameter (ID).

By my best measurement, it's 2 29/64", or 2.453". Divide by 2 to get the radius (1.2265"). Square the radius, multiply by 'Pi' (3.1416), and you have the stock cross sectional area:

1.2265 * 1.2265 = 1.5043 * 3.1416 = 4.7259 square inches

Now, increase that by the same increase in the injector size (37% in this example), then divide by Pi, and take the square root, and multiply by 2 to get the new, recalibrated ID.

4.7259 * 1.37 = 6.4745 / 3.1416 = 2.0609 [square root] = 1.4356" * 2 = 2.8711" ID

So theoretically we need a 2.87" ID tube - Conveniently, some 3" exhaust tubing is 3" outer diameter with 1/16" wall thickness, leaving 2.875" ID...

But I have found, with more and more testing, that 2.875" ID is too lean. Apparently the hack introduces enough inaccuracy that we need to be bit smaller to keep a proper A/F - I had to play around A LOT to figure out what worked for my setup, which is ~2.75" ID.

So we have an *almost* exact tube, for relatively cheap, and easy to find. Now you just hack your MAF down to nothing but the square box on top and the hot-wire sensor, and insert it into the 3" tube in the same manner as it was installed form the factory. JB Weld works well for this...
 

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No it won't work for the Celica. Our ECU are much smarter than that. Even with my S-AFC, the engine learns to compensate and adjust for the modifications in the fuel curve by the piggyback, so the only way around it is to make small changes hopefully undecteded by the ECU and/or reset the ECU once in a while.

Your best bet is get a ECU like Apexi PowerFC.
 

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Discussion Starter #5
Here's where I think your wrong. The ECU gets it air volume data straight from the MAF, your not altering the signal in anyway, your simply allowing air to pass by unmetered. If I had a spare MAF I'd try it out with my wide band just to see.
 

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sure it gets data from the mafs; he's saying the ecu is smart and adjusts.

from my experience going to a larger diameter pipe makes the air/fuel mixture leaner. the air velocity in the pipe is decreased and the stock mafs is calibrated for a certain diameter 2.5", so less fuel is sent b/c less air is detected.

One way around this is to have a dual air paths in one intake. Use two filters, and two paths going to one throttle body, and have the mafs on one path. The air path without the mafs will be smaller. Yes this is a custom job. But it won't cost too much to have that extra tube welded on your intake.
ok for a turbo you wouldn't have two filters like all motor. you would have split paths to the throttle body and the mafs on one path.
please don't turbo with the stock ecu for your motor's sake though. and if you don't use the stock ecu, you could just send the right amount of fuel to match the air coming in. so don't do the hack and don't do my suggestion for turbo.
 

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sure I offered a solution in line with your inquiry but I wouldn't do it.

just get a PFC, expensive but worth it.

you're trying to hit something by mechanical means/math which is I have to say a little silly on EFI cars. yes maybe it kinda of works to do this hack on other cars, but you won't get maximum hp and torque on the Celica (I don't care if other cars are slower by doing this funny hack stuff though, just don't make Celicas look bad) :). you need complete fuel control at all rpms and all loads, something you can't do by just plugging in bigger injectors and sneaking more air in no matter how you do it.

uh, you're really not planning on turbo with a stock ecu, are you? uh oh...
 

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Discussion Starter #8
QTRMLR_1 said:
sure I offered a solution in line with your inquiry but I wouldn't do it.

just get a PFC, expensive but worth it.

you're trying to hit something by mechanical means/math which is I have to say a little silly on EFI cars. yes maybe it kinda of works to do this hack on other cars, but you won't get maximum hp and torque on the Celica (I don't care if other cars are slower by doing this funny hack stuff though, just don't make Celicas look bad) :). you need complete fuel control at all rpms and all loads, something you can't do by just plugging in bigger injectors and sneaking more air in no matter how you do it.

uh, you're really not planning on turbo with a stock ecu, are you? uh oh...
Do you have any idea how many times I've been told, "it won't work" only to do it and have it work just fine. Has anyone tried it...no. We're talking about a large gap between a free mod and a PFC. Not to mention the damn Celica can't handle much power without puking up a tranny anyway. So for a few lbs of boost this mod may actually work fine. We'll see though, It can't hurt to try since I can get a MAF for a couple bucks at the junk yard.

The big hurtle with using the stock ECU won't be the AF curve but the NA timing map. That mixed with 11.5/1 compression makes it difficult to do. But I've been using alcohol and methonal injection for the last 6 years on my Skyline, so I'm going to try the same route.

Thanks for the input though. Hopefully I can make this happen.
 

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The theory is sound, but the application would be very tricky - the thing is if ALL you want to change is injector size you might get away with it. But if you need bigger injectors you probably have a turbo, which means you need a richer air fuel mixture as well. Plus air flow is not constant throughout all areas of the cross section of a pipe. You have the potential to change the percentage by substantially more or less than you intend.

Anyways - this has been tried (in reverse) to try and get a richer mixture for turbo cars. The problem is the factory O2 sensor picks up on anything and everything you do to try and screw with the A/F ratios and will eventually tune it out.

So long story short if you just want to change injectors, you are happy with the stock air fuel ratios, you have a way to stabilize the airflow )extended honecomb or vanes), you are confident in the math for the percentage change and you have the patience to try it a couple times in a row to make adjustments then I think it might work to an extent. I would think chaning the total intake pipe size would be more effective than actually tampering with the MAF itself.

The S-AFC does not work in the slightest however.
 

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Discussion Starter #12
Well, I have a LM1 wideband to screw around with and a knock meter. So I'm just gonna play with various sizes. Starting with a slight increase and increase until I get suitable AF levels. I'll be running 42lb injectors. I can also increase/decrease the fuel pressure to adjust baseline af's as well. A DIY return system isn't very difficult to make, I already have a bunch of fuel rail stock, fuel line, connectors...etc you get the point.

While I'm on the return system topic. Has anyone tried the Vortech FMU for say 6-8 lbs of boost. I imagine you'd need the 12/1 type. If its that simple I may blow off the MAF deal and just use the FMU with a alky kit.

Thx for the opinions by the way.
 

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WDRacing said:
Well, I have a LM1 wideband to screw around with and a knock meter. So I'm just gonna play with various sizes. Starting with a slight increase and increase until I get suitable AF levels. I'll be running 42lb injectors. I can also increase/decrease the fuel pressure to adjust baseline af's as well. A DIY return system isn't very difficult to make, I already have a bunch of fuel rail stock, fuel line, connectors...etc you get the point.

While I'm on the return system topic. Has anyone tried the Vortech FMU for say 6-8 lbs of boost. I imagine you'd need the 12/1 type. If its that simple I may blow off the MAF deal and just use the FMU with a alky kit.

Thx for the opinions by the way.
You will not be able to change the A/Fs from stock without a Power FC with the exception of under WOT. The oxygen sensor feedback control logic is way too aggressive

SF sells a really nice FMU with his turbo kits that works well in conjunction with a SS piggyback. Still can't make as much power as you can with the Power FC though.

Also - just FYI - most folks who deal with imports refer to injectors in terms of CC rating not pounds - makes it easier to get an idea of what a person is running if everyone uses the same lingo
 

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Discussion Starter #14
Boosted2.0 said:
Also - just FYI - most folks who deal with imports refer to injectors in terms of CC rating not pounds - makes it easier to get an idea of what a person is running if everyone uses the same lingo
LOL, thanks for the tip. I've been in the import bussiness for 7 years. I've had 3 Skylines, 1 Silvia and an EVO. I buy my injectors in bulk. Usually in sets of 8 from Summit or a Mustang site. In which case they're listed lbs. I use both terms all the time so...

As far as the ECU goes, what a royal PITA. The Celica in general is getting on my nerves. The mission is horribly weak, the ECU is un-moddable and it lacks a return fuel system.

I just hate buying a kit when I can build most of the crap DIY style. Perhaps I'll leave this car in NA form...............
 

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Originally posted by WDRacing
I just hate buying a kit when I can build most of the crap DIY style. Perhaps I'll leave this car in NA form...............
Seems like the PowerFC will solve all your problems, and if you've owned 3 skylines I don't think the $1000 needed to pick it up will be a problem ;) If you can fab the rest of the kit from there, go for it!
 

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Originally posted by WDRacing
The Celica in general is getting on my nerves. The mission is horribly weak, the ECU is un-moddable and it lacks a return fuel system.

true, true, true. But why get frustrated? C2Power Tranny. PFC. (you said you can do it, so do it).
 

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Discussion Starter #18
S|Lv3rBu||et said:
Seems like the PowerFC will solve all your problems, and if you've owned 3 skylines I don't think the $1000 needed to pick it up will be a problem ;) If you can fab the rest of the kit from there, go for it!
I have a ton of money getting dumped into my 240, but the Celi is definitly getting boost. I got beat up by turbo Civic last night for the first time in my life...

I was in Japan for 6 years, thats where all the really nice cars came from. WAYYYY cheaper...lol.
 

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I am wondering if those kinds of cheap power additions are not going to be made much more difficult with all the crazy newer ecus. Its the same trick that folks do on mk3 supras using the lexus v8 afm. damn computers are getting too smart.
 
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