Noob Rotrex reciculation valve questions
 

Folks,

I joined MT.net in 2011 when I was purchasing one of the early Kraftwerks kits. It did not materialize. I have one now. Greetings. I drove the car back from the tuner the other day, almost all highway driving. Very impressed. This is my HPDE car. I wanted a low boost setup for the track. I'm running a 90mm pulley and got a max of 7psi at ~7000rpm. It turned out exactly as I wanted.

I have spent the last couple of weeks refitting my undertray and front brake ducts. I drove the car for the first time today around town. I get normal AFRs when I'm accelerating, even just a little, but if I lift to establish a constant speed, say 35mph in third gear, the AFRs jump up into the high 15s, and I hear the change in the intake sound, which I'm sure means the recirculation valve is open. Just a little gas drops the AFRs and changes the intake sound. I never let it go long enough to see if the AFR settled back down. I don't have issues at constant highway speeds.

Is this normal? Anything I can or should do?

Thanks,

poormxdad

This could be normal. I run a PD SC with a Turbosmart BOV configured to do this on purpose. What happens is the reference pressure (presumably the manifold) drops with respect to the inlet pressure as the engine load is reduced. This allows the "extra" pressurized air from the SC to recirc. I consider this to be desirable as it reduces the pressure differential across the SC in load conditions where the flow is not required. Under these circumstances the charge temp drops due to the reduced pressure. The AFRs are at 15 because you are in a cruise region of the fuel map. Under dynamic or sustained loading (acceleration, up a hill, passing, high speed...) you enter a boost region of the map and the AFR responds accordingly.

I do re come d a high quality and high flow BPV. I have experience with several. If you are running the traditional Bosch stocker style, you may be losing performance or choking.

Is there an AFR number that I should be concerned about during the recirculation? BTW, I'm running one of Rev's MS3 Basics.

Here's the link to the BOV.

155-99-0100 - Supercharger Accessories - Performance / Accessories - KraftWerks USA

Comments appreciated.

Thanks,

poormxdad

That looks like it should be a good valve. You want a piston style with a decent diameter. At 7psi (1.8L), that one should fit the bill. Nice Work.

Do you have a manifold pressure gauge (boost)? If so, you should be comfortable with AFRs in the 15-ish range while in manifold vacuum, and AFRs in the 12-ish range while in boost. This is a simplification obviously. If you have your target AFR map from the tuner, then you can reference that for what you are actually trying to hit in terms of AFR.

What kind of engine/fuel management are you running? Edit - you answered this question. Check out the target AFR map.

I just went for another ride. Coming down my street at a whopping 25mph in second, I was seeing AFRs in the 16s, but she was running smooth as silk. Before the Rotrex, anytime I saw AFRs like that, she would run horribly.

If this is a by-product of the recirc valve or the intercooler, does that mean I can't tune it out?

Worry or not worry?

Thanks,

poormxdad

Rotrex and megasquirt at the same time?

Well, no, not exactly. The MS3 Basic has been installed for two years. Just now adding the Rotrex. I also have a squaretop, MSM intake cam, RB header, and it's the MTX-L that is making me ask all these questions... Even with the 90mm pulley, she pulls like a beast. Unfortunately, I'm a forced induction virgin.

But you have somebody tune it for you?

Hook it up to timerstudio when you are driving. See what the AFR target is during these situations. It is not uncommon for people to tune lean in the cruise region of the map. Additionally, if fuel cut on decel is not turned on, you can see all sorts of variation in low load regions unless you have precisely tuned the deadtime and flow rate of the injectors.

An AFR of 16 is acceptable under the right conditions, and totally unacceptable in others. Post your tune for further analysis if desired.

Yes, dyno tuned using their machine's O2 sensor. I told the tuner I would sacrifice horsepower for reliability. The spark curve is very conservative. It runs great, even when my MTX-L is showing less-than-good numbers.

If I did not have the MTX-L, I would think everything is just fine.

poormxdad

Does tunerstudio match the WB?

Ted,

I am not the smartest guy to answer that question, but doesn't it have to be yes? If not, I need a complete gyro reset.

poormxdad

This is not nearly as scary as it sounds.

Do you have a laptop with the Tunerstudio software loaded on it? I do not know what Rev sends with his builds, but if he sent you a CD, it probably has Tunerstudio on it. Install it and update it when asked.

Edit - cross threading. Whoever sold you the MS3 should have also sent the CD.

Yes, I have TunerStudio. And when it reads AFRs, it's using the output from my MTX-L. Not sure where you're going with this, but I'll play along...

Does the output in the software match what the gauge is telling you?

I would say that since I can't read both absolutely simultaneously, they are close enough. But... again... how could they be substantially different?

You tell the megasquirt what scale to use based on what kind of WB controller you have.

It would be helpful if you could post your tune file (*.msq) for review.

You can also add an indicator to your dash that tells you the AFR target. Do this by right clicking the dash, switching to developer mode (working from memory here) and either copy and paste the AFR gauge in the dash and change the input to AFR target, or create a new indicator. Another route would be to open the AFR target map while running. You will see a little dot that tells you what cell the car is working with. The value in this cell should be pretty close to what your gauge is reading.