i'm in europe
so i suppose that both my tib and Elantra are MAP based.

are those engines less sensitive to intake mods such CAI BBTB and IM ?

will i see any improvement from bbtb and IM???
or in a map based engine i will only loss my money??

 

First, making sure everyone knows what these acronyms mean. The wording is very important here, if you don't know what the sensor name actually MEANS, then the next parts won't make sense.
MAP = manifold absolute pressure.
MAF = mass air flow.

Let's say that you live exactly at sea level and your car is 100% stock. The barometric pressure for today is 900 millibars. If you don't know what barometric pressure is, watch your local news station for the weather. Listen for "barometer reading and "low and high pressure cells"...

If you hold the car at wide-open throttle, foot to the floor balls-out, then your MAP (manifold absolute pressure again) should read almost exactly what the "normal" outside pressure is... In this case, your MAP sensor should read almost 900 millibars. It will be slightly less, because your manifold is never completely free of vacuum unless you're driving a VERY modified car. So maybe instead of 900 millibars, the MAP is reading 870...

Ok, so now let's bolt a cold air intake to this creature.

We go for a drive on the exact same day and again at wide-open throttle, our MAP sensor will read almost exactly what the "normal" outside pressure is... Let's say it reads 880 millibars this time.

The problem here is that your car is not measuring the MASS of air that's rushing in, it's only measuring the PRESSURE on the manifold. Even though it's likely that your airflow (mass) has increased by 10-15%, your little MAP sensor sees an increase of about 1% (give or take).

Since the MAP only sees this tiny little increase, the computer applies an equally tiny little increase to the fuel. The result? Your car runs lean...

This is why nearly all MAP cars with a big handful of parts (ie Honda, Acura the most popular) need more fuel pressure: the computer can't see all the upgrades, but you definately need more fuel.

This is ALSO why having more fuel pressure on a MAF-based car is wholly unnecessary until your stock injectors can't provide any more. A MAF sensor (mass air flow) can see all that extra air coming in and adjust for it accordingly.

With just an intake, the amount that your car leans out will actually likely do more GOOD than bad. All new computer-controlled cars come with a large margin of safety in tuning by all running a bit too rich. My Tiburon seemed to run as much as 17% rich at the top of the RPM band.

So just an intake may provide the best balance on your stock MAP car. Anything significantly more than an intake may require a bit more fuel pressure to make sure it's running correctly on your MAP setup.

Hope that long-assed reply made sense smile.gif

 

Hey Red, On the topic of running rich... I am dyno tuning my car this weekend, just for the record what were your settings for the S-AFC and what (8) NE points did you use? I used:

1 1000
2 2000
3 3000
4 4000
5 4500
6 5000
7 5500
8 6000

Can I ask what settings you had at each point? I will use this as a base... Did you use Lo-Hi throttle or just modify the HI? Thanks!

-Steve

 

Great answer Red!!! It helped a lot for me! wink

 

your answer was very helpful
now i understand why my custom cai
doesn't make very big difference.

if so i will not go for BBTB IM .
DAMN MAP BASED CARS !!!

 

ops sorry for double posting
but ... i've got a questions
can i tweak the MAP sensor to run a little more rich without get a cel?
with a resistor for example ?

 

Hey Fastiburon i dont think you got the point there....If you increase air quantity you also have to increase fuel quantity.Map based cars are not damned at all.You can put your custom cai on,,and then remapp your ecu for more fuel.How this can be done?????You will reprogamm the EPROM in a way that the injectors spray more time{increase spraying duration}.You can also adjust your rev.limiter about 7300/7800 rpms.....
Then check your performance and youll see your car is not DAMNED at all...
BTW where are you from???

 

BV1,

I used these NE points:
1000
2000
3000
4000
5000
5500
6000
6500

With these parts on my car:
MHP CAI
HVE Throttlebody
BBIM
Ported head, 3-angle valve job
1.8L (and then later Elantra GT) intake cam
HVE 4-1 header
2.5" dynomax cat and full 2.5" exhaust
PowerChip "Gold" ECU swap from Oz

The S-AFC went *about* as following (note it's been a while, memory is subject to being old wink )
1: 0%
2: 0%
3: -3%
4: -5%
6: -9%
7: -14%
8: -17%

LO throttle set to 75%, HI throttle set to 90%, and all the settings I just gave you were applied to the HI throttle map only.

If you start adjusting the low throttle map, this is where the OBD2 system will start to "learn around" your setings. But at wide-open throttle, the ECU doesn't listen to feedback from the O2 sensors because it just dumps fuel and expects everything to be horridly rich -- which it's generally correct until YOU fix it wink

With the parts I listed, I gained 8 wheel horsepower on the dyno rollers in a single hour of tuning with a wideband O2 sensor. IIRC you want to aim for about 13.5:1 to make these cars happy...

 

Hey Red that's a very illustrative answer. Are MAP based cars less expensive to build? Because I don't understand why manufacturers (Hyundai also since new gen Betas on 2001 Elantras and Tibbs) use MAP when aparently MAF is more efficient. I know if only production going to the states uses MAF, it would be great to standarized and convert ALL production to MAP, but why not use MAF on cars for Europe, and every other marjet too?

 

There are drawbacks to MAF as well, most of them being either manufacturing cost or later support costs. MAF sensors are more expensive to produce than a MAP sensor, and are also more fragile. Also, having something "measure the air" as it's going past will naturally cause a restriction in that air; MAP sensors don't do that.

BUT as we pointed out above, MAF sensors are much more likely to pick up modifications and variations in air flow. Their added expense to the OEM market usually results in better performance vs the "cheaper" MAP sensor.

All things considered, if you have NO control over the computer, a MAF sensor is the best way to do it. But if you have a method of programming your own ECU (or have a full standalone like some of us lucky bastards wink tongue.gif ) then a MAP is the best way to go.

For those of you with MAP-based cars who want more mods, just bolt on an adjustable fuel pressure regulator and your problems are solved. Remember that every Honda/Acura out there is MAP based, so it's not like the cars are impossible to upgrade or anything smile.gif