The point is that MAF voltage does not go up linearally with air flow.

So your larger MAF might be 1.2:1 at low air flow but 5:1 at high air flow.

There is no linear relationship between airflow and voltage, for any MAF, so the ratio's between the 2 MAF readings would also not be linear.

 

Without an approximately linear ratio between the sensors I'd have to deal with it thru the computer, then.

Fortunately, I don't need to worry about it. but it does bring up the question of what the people adding big turbos do about it. Switch to MAP sensors?

 

Yup. If you are going with a turbo that's big enough to warrant getting something better than the stock MAF, then usually you just convert to a standalone engine management system like the Haltec. Any standalone system that's worth the money converts to a MAP system; specifically a MAP setup that can register boost.

The stock MAP sensor in the newest Elantras and 4-cylinder Tibs is not meant to read boost -- it's effective range is like -30 to +4 inches of mercury (vacuum). But if you started feeding the motor boost on a stock MAP (anything over a few positive inches of mercury), it would throw a check engine light because the computer would think the MAP is broken for sending signals above 0 wink

Aftermarket systems come with 1 bar (N/A), 2 bar (up to 15psi boost) and 3 bar (up to 30psi boost) MAP sensors. That covers just about every setup any normal sane person would run. Most standalone systems also offer even higher MAP sensors if you specially order them; Haltec offers a 4 bar (up to 45psi) and Motec even offers a 5 bar (up to 60psi) MAP sensors as optional parts.

 

smile.gif

Thanks Red and everyone.

Disappointing news though , doesn't look like I'll have the budget to do anything to the car until May, at least. I'll have to file this information away in the back of my brain for a while.

 

Actually, are you sure?

Lobert is running 8psi of boost on his US 2001 accent 1.6L

All he did was upgrade injectors

he has not aftermarket engine management or piggyback.

and he has run fine.

just in the based week he obtain a smt5.

 

Shadohh...Why'd you let the cat out of the bag?????????????????? LOL I did get the car up to 8 PSI with the up graded injectors. The car ran rich as haydes at idle and almost to lean up top but she ran. I now have the SMT5 installed and working. Now it's time to dyno this puppy and see what shakes loose

Forgot to mention that the only CEL I have gotten is not because of the MAP sensor it was Misfires due to bad plugs and one for an O2 sensor going bad.

[ January 01, 2003, 09:12 PM: Message edited by: Lobert ]

 

One last bit of info to share and then I'll shut up. I wanted to find out how much resistance there was exactly in the stock intake. One method of doing this is to measure vacuum at various points in the air intake path. Below are the results of my testing.

The tests were done during acceleration in 2nd gear at wide open throttle. (from about 30 to 60 mph) As you would expect max vacuum was reached pretty much at the peak HP RPM (5800). Numbers are all in Inches of Water rounded off to the nearest .25 inch.

Stock Intake with resonators removed.
Total - 15.5
Bottom of the airbox and filter - 4.75
Top of the aibox, flex tubing, and MAF - 9
Throttle Body - .5

I removed the stock airbox and connected a homemade "high flow" intake. Basically a cone filter and enough aluminum tubing and elbows to connect it directly to the MAF sensor.

Total - 7.5
Filter, a 45 degree elbow - 1.5
A 90 degree elbow and the MAF - 5.5
Throttle Body - .5

I kind of wish I had done measurements with the stock resonators on as well, but my gauge didn't go that high (Max was 16 In/H20)

I presume you would get similar numbers with a manufactured intake from AOS or Injen. It makes a difference in the cars performance. The car does accelerate better. I especially notice it at highway speed, like when I want to speed up from 55 to 60 or 65. No real noticable change in off the line acceleration though.

[ January 02, 2003, 10:34 AM: Message edited by: blue2000 ]

 

If you're running "only" bigger injectors and nothing else on the MAP-equipped Accent, then your motor is probably destroying itself as we speak. Literally. It wouldn't suprise me to find out your "misfires due to bad plugs" are due to metal shrapnel coming off your pistons and fusing itself to your plugs, valves and cylinder head.

MAP sensors are built for specific ranges, and a normally aspirated car doesn't use a MAP sensor that is made to detect boost -- nor does the ECU have programming to understand boost. There's no need for Hyundai to spend the money on equipment and programming that will never be used on an N/A car.

 

Well Red, Tell you what. When I tear the engine down to put in the new pistons I'll take pics for you. As far a metal fusing to the plugs. nahhhhhhhhh. I have changed them and the plugs do not show any signs of detenation.

Just my .02 cents here