MSP at dealership for service (hesitation/clunk/oil)

[turboge]

The intake so far as I've seen is the piping size and routing. The Injen is large and almost a straight shot to the turbo. The stock has all kinds of rediculous bends and is fairly small and restrictive.

The boost loss is not due to the BOV, it is intercooler efficiency and turbo efficiency. When I hit 10psi it holds till about 5000 and slowly starts to decline to 7-8 at redline. This could also be the factory wastegate being inefficient.

 

[BremertonMSP]

Here is my theory...stock BOV (Bypass Valve) is poor quality and it may leak. The leak is creating some sort of abnormality in flow with the MAF sensor and that is creating the hesitation/stumbling? Soo, the people who are not experiencing the hesitation aren't experiencing any boost leak and therefore have a properly functioning BOV (Bypass Valve).

Soo, this problem is a hit or miss kinda thing that starts with the BOV. THIS IS PURELY SPECULATION, I HAVE NO PROOF TO BACK THIS UP

Any opinions? [/B]

If that's the case, then the guys running aftermarket BOV's should not have this problem.

IMHO, if I were a Mazda Tech/Engineer, I would look at the MAF, ignition system and timing issues. I don't like the fact they put a cover over the engine, and are using stock coil packs and stock spark plug wires. Heat is not good for iginition parts. I've got a slight stumble/hesitation in gears 2-5, and it's annoying. I need to get my boost and AFR gauges hooked up so I can see what's going on during this situation.

Let's keep the ideas comming guys, it's interesting to see what you guys think of this.

 

[MSP Pro]

Nerd Alert!!!! Caution: Math & BS!!!!

The boost loss is not due to the BOV, it is intercooler efficiency and turbo efficiency. When I hit 10psi it holds till about 5000 and slowly starts to decline to 7-8 at redline. This could also be the factory wastegate being inefficient.

Braden: This sounds like turbo efficiency. 10psi up to 5000 and then slow decline tells me that the turbo ran out of capacity as the revs topped 5000. Takes 20% more air as the revs go up 1000 from 5000 to 6000. Of course, the turbo is supposed to spin faster as more exhaust gases are output at the higher revs.
Hmmm, maybe it's not flowing enough intake air to keep the turbo well supplied? Gee, even with the Injen intake? Anyone do any air pressure measurements at the turbo intake? If the inlet feed pressure dropped off, then we'd know it was the problem.
Anyone know how to do an air consumption calculation for a four cylinder four stroke? Let's see, two cylinders fire every rpm; total displacement is two liters, so that's one liter per rev (assume no boost; I'll add that in later). 5000 rpm is 5000 liters at normal atmospheric pressure. If boost is 7psi, that's actually 7psi over atmospheric, which is about 15psi. So that's another 50% air flow to achieve that. OK, 7500 liters/minute is how many cubic feet per minute? (Conversion factor nerding left out...) 7500 liters/min divided by 28.85 liters/cu ft = 260 cfm.
This actually sounds reasonable! Thinking back on old carbs, a big Holley would flow 750 cfm for a 6 liter engine normally aspirated.
So, 260 cfm through a 3 inch pipe, yeah, you might be starving the turbo for inlet air! Lots would depend on the air flow resistance of the cone filter.
SNAPS AWAKE AGAIN...
Sorry about that. Err, got any dyno charts of 10 psi and the Injen intake?? THAT would be interesting...

 

[unwrittenLaw]

Just wanted to say this is a great thread and I hope it keeps going...

I have a K&N and I still notice slight hesitation/stumbling in 2nd and 3rd usually between 4-5K rpms...

Hopefully someone will pinpoint the problem..cause the stumbling is kind of annoying...

Anyways, hats off to everyone troubleshooting this...I wish I could help more, but I'm too dumb.

 

[turboge]

Redmptions MSP holds boost at 10psi to redline. This is with the Injen. The stock intake has an effect as a restriction.

 

[Street KingFD]

I think someone needs try a GROUNDING KIT on teh MSP and see what it does. Should ground the exhaust to the chassis, engine to the chassis, and the ECU to the chassis. I bet this helps out a lot.

 

[turboge]

Hook me up and i'll run some wires.

 

[122 Vega]

"Let's see, two cylinders fire every rpm; total displacement is two liters, so that's one liter per rev (assume no boost; I'll add that in later). 5000 rpm is 5000 liters at normal atmospheric pressure. If boost is 7psi, that's actually 7psi over atmospheric, which is about 15psi. " - MSP Pro

This is considering 100% volumetric efficiency, which no n/a motor has. The best is probably 80%. Obviously the turbo Provides motivation for the air to get into the cylinders, but VE depends on one thing, degree at which the intake valve closes in relation to the piston. This motor with the turbo is still probably 95% at best.

But again, once I was told that I was a nurse, not an engineer, so stop trying to talk like one.

Britt

 

[boostisgood]

Well guys,

I got my boost and a/f gauge in, and the damn car runs uber rich, even before the ECU goes Open Loop. I also notice that the boost pressure drops off in 4th and 5th gear after about 4.500 rpms. It will hit 7 psi then drop down to 5 psi. (I would also atribute this to the warmer air, and inefficiency of the IC)

just thought I would provide some data from my end. hope it helps, Ill see what I get out of the Mazda tech saturday too.

 

[MSP Pro]

But again, once I was told that I was a nurse, not an engineer, so stop trying to talk like one.

Hey, Britt, I never said that! I always think that as long as people are curious and want to learn, then let the discussions roll! Are you going to be at PIR for the autox on May 17th? It would be cool to do some lunch afterwards and talk cars. Or Sunday, if that's better for you. Lemme know.

 

[122 Vega]

I will do some autocross this summer, but I work every weekend until July. Then I am on paternity leave for july and August. I would love to come out and run the MSP, STS I guess. Or I could run PAX. I haven't done any autocrossing since I sold my green Vega with the 400hp Vette motor in it, that was a blast.

The comment was from a Pontiac engineer (retired) in my other car club, I just thought it was funny. Another way for me to say "In my opinion..." He's kind of an ass.

I will have to check out the schedule to plan ahead for some weekend fun, I haven't had this much time off sine the summer of 1990 before I went in the Army. I should have kids more often!

Britt

 

[03MzdSpdSTP]

I am hoping when i get the MSP the break in period ends before Auto X season starts!