Hesitation

[laptopheaven]

I know this has been beaten to death, but I had a few comments.

I was talking to a friend who has a addiction to RX-7s. I had mentioned the hesitation problem the MSP has. He explained to me that all Mazda turbo cars have the same problem. He explained that it's either the point where the ECU switches from the O2 senor to the internal map. OR Mazda programmed the ECU to dump a bunch of fuel, keeping the car nice and rich and safe. Both seem like viable ideas.

Has anyone dynoed the MSP with a wideband O2 senors to track the A/F with some accuracy? If not, I might see if I would get in to the dyno 2morrow and borrow my buddies wideband O2.

 

[funnylittlman]

DO it and keep us informed please!

 

[OrangeAppeal]

if you can and will....DO IT

even if someone has done it already, it will back up their findings...if they haven't, well then, you've set the benchmark.

thanks

 

[ping]

There's some informal research (a/f gauge and boost gauge) that supports this, have to check the other hesitation posts. (See thread http://www.msprotege.com/vbb225/showthread.php?s=&threadid=19749&pagenumber=3)

The Injen intake is purported to allow more air (hence more air to the "rich" mixture), alleviating part of the problem, but I think only 1-2 people actually have the intake...

I think Mazda will take care of us if enough people get to their dealers, write Mazda, and make it all known.

 

[I-Am-Chris]

it runs at 10.5-1 at 10 psi.

 

[MemphisRacer]

would you consider 10.5-1 a little lean for 10psi? I was under the impression that 14-1 was a good stoich point.

 

[OrangeAppeal]

would you consider 10.5-1 a little lean for 10psi? I was under the impression that 14-1 was a good stoich point.

10.5:1 is rich, not lean. And yes 14:1 is a good stoich point, but it is better to run rich than lean (detonation = bad), especially with a turbo motor.

 

[kwiktsi]

I have a friend in FL who dynoed his car and right around the switching point (4500?) it went pig rich on him.. If you have an AF gauge, you can see this for yourself- if you slowly "roll" on the throttle *just* as it comes into boost, you can feel a decent pull and see the o2's cycling, once you push the throttle past that point (both throttle percentage and RPM), you can feel the car fall on it's face and see the AF gauge get pegged in the rich. I got to play around a lot on my drive to FL and learned a lot about how the car reacts.

Here's what I did-
1. get more air in and out of the motor to compensate for the fuel- more boost, K&N and 3" turbo back- helped, but not not perfect yet.

2. Cool down the underhood temps- cooler air needs a richer mixture- I removed the weather stripping from the back of hood (cowl actually) to let the hot air out while driving- helped keep the car running more consistant.

3. pull some fuel out under boost- made a huge difference, but will not disclose exactly how to do it until I am done testing- don't want everyone to go out and do it, blow their car up and blame me .

Once I get the fuel situated a bit, I am going to work on cooling the motor better via a cooler thermostat and then see what issues I have ECU/coolant sensor wise and work out a way around them.

This is the only post I have seen where someone actually has the "right" explanation as to why a CAI helps- but it is only half right- it is more air PLUS the cooler air hitting the rich mixture- even then, the climate/temp plays a big role in it. I noticed while in FL that my car ran great at night and after long highway drives where the underhood temp stays cooler and like crap after stop and go traffic where it got hot as hell under the hood.. That is pretty common in turbo cars anyway, but worse with our over-rich mixture!! I was considering even some type of extractor hood similar to the Evo if necessary.

I'll keep you posted.
Joe
PS- I did manage to get the car to go 14.5@96 once I got the fuel leaned a bit and removed the weather strip from under the back of the hood (actually before the exhaust also) on 10 psi and pump gas.

 

[kwiktsi]

Oh yeah- I will try to get the dyno sheet from my friends car to show you what I am talking about.. It went from like 12.x:1 to like 9:1- TOO RICH .
Joe

 

[ARunto]

9:1...omg that's crazy

 

[kwiktsi]

Yeah, way too much fuel... The problem is the injectors either go static and hold open and it relies on fuel pressure for fuel increase or it just has some ridiculously rich mapping up top.. I have heard both- either way, it is too much fuel.. I have been working with pulling fuel pressure out up top and have had some very good results, but I want to find out for sure what the ECU is doing before I go 100% after fuel pressure. I would rather take care of it electronically if possible.. I'll keep you posted.
Joe

 

[saided18]

I think Mazda will take care of us if enough people get to their dealers, write Mazda, and make it all known.

(rofl) what is that a joke? it's been a year nice mazda has know about the "clunk" on MP3 and MSP and they haven't done anything to fix it. and alot of people have complianed to mazda. it does no good.

 

[laptopheaven]

Joe:

Do you know the output of the MAP sensor? Maybe we could alter the output of the MAP sensor and lower the voltage out the senor, telling the ECU there is a lower amount of boost?

courtneyb

 

[kwiktsi]

First I have to figure out if the map is responsible for the boost cut or the MAF. I have heard both, but judginh from how it is worse in different temps, I am assuming it is airflow based. If it were tha map, you can easily add a ball and spring type adjustable bleeder to the vacuum line going to it. If it is MAF based, you need to either create an air leak after the MAF (not the best way to do it) or electronically make the ECU see less air via an AFC or FCD. I was thinking of going with the OLD style AFC (the kind with the knobs on it) to fine tune the part throttle mixture and to get rid of the fuel cut if that is the case..
Joe