Lowering Boost made more power

[KaliCali]

Hi all,

Interesting happenings just recently. I daily drive my MSP at 8.5 psi with spikes at 9. I have a full turboback, injen, and fmic. Been working at Vishnu Performance for half a year now... and never took advantage of Shiv and his dyno. Finally found time to put the car on the dyno and put down about 155whp (Dyno Dynamics mind you). What dropped our jaws was the AFR dipping off the charts at 9:1.

More room for boost? no... instead we found that by using resistors to modify MAF sensor voltage, we leaned out the AFR. Also took out the MBC and found more low/mid range power. So now I boost at about 7psi and the car made an additional 20whp.

At the time we've been working on putting an Xede on the MSM. We've found similarites in the two, so I hope that an Xede will be compatible with the MSP in the future as well.

I'll be getting the Dyno Sheets later on today. Just thought I'd let everyone know since there aren't that many fuel managment choices for our cars. Just kinda interesting what you can do with a couple resistors.(hump)

 

[BlkZoomZoom]

And boost pressure sensors... lol. I've been through all that.

 

[Dexter]

So, not lowering the boost, but modifying the A/F ratio is what made you the power...

 

[KaliCali]

mm... yea... leaning out A/F ratio but made more reliable power, espcialy more mid range power, by going with stock boost as opposed to 9 psi.

Anyways, aspects of having the Xede available for the MSP would be great news to many.

 

[Mallard]

What kind of a/f's are you running? Care to post a dyno sheet?

 

[ND4MSP]

and a quick how to pretty please

 

[Shadow102]

first off thats kool u work at vishnu probably see alot of great cars go through that shop.

neway as far as adding the resistors to the MAF how did your AFR look and would that be a reliable daily driver fix or is it too unstable to rely on the set resistance (i would assume not reliable because of the varied readings of the maf)

 

[Mallard]

Also, on Xede's site it says it works with the SP20 2.0L. Isn't this the same wiring harness as the MSP?

http://www.xede.com.au/

 

[KaliCali]

The Familia they have in Aussie land is a wire in, so there is no plug in play harness yet. Just haven't had a chance to take a look at the ECU wiring.

As for the A/F ratios at WOT they dip to 10:1 at mid range and go to 11.5:1 at redline (7200 rpm) So far as daily driven the car runs great, way better than before. The car would consistantly pull back timing every pull on the dyno before the "resistor tuning". From the first pull of 155, with 3 min cool downs, the last pull was about 145. I saw the same thing when running road courses, if I didn't run higher octane gas the car would just kill itself after 3-4 laps.

Only thing that has changed with the car is the idle. The car idles a little rougher, very similar to if you were to have higher duration cams lol... other than that its run fine at full and partial throtle.

Dyno sheets tomarrow when i get to work =P

 

[Shadow102]

well if that is the case spill the beans on what kind of setup you are running for the resistors

 

[TX Speed Demon]

^^ Yeah what he said. Give some of us with no clue what these resistors are or how they work some info or links to them.

I'm running an un-flash 03 MSP and my dyno charts were pegged at 10.0 (the lowest it would read) from 2300 RPM to about 6000 when it jumped up to a whopping 10.6. I've since upped the boost which helped, but not as much as I would like.

I'd love to get some additional resources to learn more about how these work, where to buy, how to install etc.

 

[Shadow102]

as far as how they work basically you are sending an altered signal to the ecu from the maf so the ECU thinks the maf is seeing something different. This is all basically the idea behind a AFC. The thing i was asking about earlier was how it works in daily driving was because by just putting reisitors in there you show where the AFC has the advantage of altering fuel mixture values based on what the MAF sees where as the resistors stay constant throughout the range of the MAF signal. As far as buying them resistors are a $1 at the most from radio shack

 

[BoOsTiN]

Nice work. It would be cool to see the exede come out for us. What did you dyno at stock? I hit 138 on their dyno.
If curious how our #'s compare stock.

 

[TX Speed Demon]

as far as how they work basically you are sending an altered signal to the ecu from the maf so the ECU thinks the maf is seeing something different.

So how do you know how the signal is being altered by your resistor? Just slap it on and see what happens? Or are there specific applications that do specific things?

 

[BlkZoomZoom]

This is not something for someone with little understanding of how modern day cars work. You have to know what signals the pcm is looking for, what sensor puts out what signal under what conditions. Its ALOT of work to get something set-up that works under all conditions. On top of that you need a really good scan tool woth datalogging or the wds.

I went through this last year with pretty good results, however whenever you change something its another full day of testing before it runs good again. Thats why I switched to the MPI. Same results that are repeatable and easy changing.

 

[Shadow102]

So how do you know how the signal is being altered by your resistor? Just slap it on and see what happens? Or are there specific applications that do specific things?

well i am not sure how much you know as far as how a maf works but it takes in what it sees from the air and sends a signal voltage back to the ecu and from there the ecu uses that input (along with some other ones) to tell the injectors how long to stay on (or how much fuel to dump in). Now say an unaltered signal is 5v straight to the ECU and is putting say 10.1:1 AFR in the engine but you want to lower that voltage so the ecu thinks you are putting in less air and therefore will put in less fuel when in essence you are still putting in the same amount of air. Say you want 11:1 AFR which could be say 3v from the MAF all you do is put a resistor inline with the signal wire to eat up those 2V and it will send 3v to the ECU. But the biggest thing here is it will take away signal voltage from the entire range of AFR so at idle you will be running leaner than normal which is what is happening hence the rough idle.

***BTW all those numbers are what if's and are not real i was just using them to illustrate my point

 

[Shadow102]

I went through this last year with pretty good results, however whenever you change something its another full day of testing before it runs good again. Thats why I switched to the MPI. Same results that are repeatable and easy changing.

thats why i agree a AFC is the better route to go the resitor method just seems like a temporary fix until i could afford a AFC but i do know there would be no way i would just put a random resistor in the signal wire without seeing that it works firsts on paper

 

[TX Speed Demon]

So there is no way to tell what the resistor will do prior to installing it?

 

[BlkZoomZoom]

Not only is every car different, the atmospheric differences will change the outcome for everybody.

However if you ever wondered what a fcd is, it is a resistor hooked in line of the Maf signal with a boost pressure sensor to activate it.

 

[Shadow102]

well i am sure there is a way to tel by comparing signal voltage to AFR but other than that no there is no other way to tell. Basically you just have to have the equipment which in Kalicali's case i would definatly have to say vishnu has the knowledge, resources, and equipment to do it