Boosted TwEECer Datalogs needed

[sho_sc]

Would any of you be willing to share a couple of datalogs from your boosted SHOs?

I've been working with Lance on some on my datalogs and we both are seeing some interesting MAF signals. The voltages are not consistent between data points. The voltage swing occurs all of the time and gets especially wide during boost, which makes for difficult tunning. I've run into some other "major" issues and I need to get the MAF problem figure out before I try and tackle the rest ....

I'm running a T-Trim to a SHOShop tube (contains the BOV) to a PRO-M MAF orginally calibrated for a forced Mustang with 42# injectors then into a custom 3.5" to 3.0" tube into a large double core intercooler.

 

[Axianator]

Ransom,

If you are still running the MAF in a post-blower, blow-through configuration (as per the original SHO Shop tubing setup), then you may have the answer to some or most of your immediate tuning problems already.

Out of curiosity, are you also seeing this "swing" at idle?

 

[sho_sc]

The answer is yes to both questions. During idle, it isn't as obivious, but it is still there. I've also datalogged with the blower to MAF tube removed and eventhough the voltage swing is still there, it is reduced some.

 

[kzoosho]

i thought trying to use the maf as a blowthrough is hard to tune? am i corect? also i am going to run mine pre turbo is that the best way?

 

[Toolman]

The only drawback to running your MAF pre turbo is that it requires you (so some say) to use a recirculating valve, not a BOV. FWIW, I have a vented to atmosphere BOV and a DTM (draw-through-MAF).

 

[twr]

I can tell you on my S/C application that venting to atmosphere resulted in a pig rich condition under part throttle and decel.

 

[somedude_001]

i'm running a blow through maf on my turbo setup with a atmosphere dump. tuning seems to be going pretty smooth on my car even though it is justa basic street tune. I haven't had any mojor problems.

 

[AutoSHO]

Ransom, I've seen this on all three of the Sho-Shop style blow-through SHO's that I've had my hands on.

At one point, two of them were draw-through. They didn't have the bouncing MAF signals, but the volume of the piping is so large that above 2500 rpm, decelerating the BPV cannot divert enough air to keep the piping from being pressurized... Resulting in an extreme rich condition.

 

[Axianator]

i thought trying to use the maf as a blowthrough is hard to tune? am i corect?

Of the two popular supercharger configurations that are currently available for the V6 SHO, the belt-driven SHO Shop kit seems to be the harder kit to tune when utilizing the original air charge piping and SHO Shop-sized BOV/BPV assembly for the reasons that Chris gave above, regardless of final MAF placement or metering type (blow-through or draw-through). OTOH, the shaft-driven FPS kit seems to a bit easier to tune because of it's shorter, less complex air charge tubing configuration and matching draw-through MAF setup.

Note that the above only applies to the two popular V6 SHO blower kits. When it comes to the added components of a turbo-based system and the sheer number of possible turbo configurations (even on the V6 SHO), the dividing line isn't so cut and dry...

Ransom, I've seen this on all three of the Sho-Shop style blow-through SHO's that I've had my hands on.

At one point, two of them were draw-through. They didn't have the bouncing MAF signals, but the volume of the piping is so large that above 2500 rpm, decelerating the BPV cannot divert enough air to keep the piping from being pressurized... Resulting in an extreme rich condition.

FWIW, Ransom, I personally have also seen these same type of MAF voltage fluctuations and associated tunability issues with two of the local SHO Shop blower cars that I tuned and may be looking at a third car with the same issues in the near future. I also have to agree with Chris's assement of the situation, which has been echoed elsewhere on the forum in the past. With a little bit of patient re-engineering and some new parts, I think that a properly engineered draw-through MAF configuration would solve all of the tuning problems that we have previously seen with the often insufficient SHO Shop air charge tubing setup.

 

[yamahaSHO]

Yeah, the SS setup sucks for tuning... Abso-freaking-lutely sucks! I would have some data logs for you to look at, however, the HDD on my laptop just failed and I lost everything. At least I had my new "test" tune for the built motor saved on my Media Center PC, since I won't have old DL's to look through, nor a saved program (aside from what is currently in the TwEECer).

When I had a draw-through MAF, it ran GREAT at WOT and moderate cruising, however, during any type of engine deceleration, the motor ran so rich, it would literally trip the computer so it would not longer learn (and possibly apply fuel trims) and I had to shut of the car and pop-start it on the freeway. In the end, I went with the SS setup as I don't really want to fabricate anything on this car anymore...

 

[sho_sc]

I've "improved" the off throttle and PT conditions by going with a Greddy Type R BOV. However, I had to "rob" the spring from my Greddy RS to get the R to open at idle and low speed driving. I'm not seeing compressor surge or pressurized MAF tube condition like I did with the RS (I've only tested this to 5200 RPM).

Here is the best I can explain it about the MAF voltage variations. It's there ALL of the time. With the blower tube removed, allowing the engine to be N/A, it is reduced, but still present. Some of this could be the fact that I am using a MAF with such a steep curve, tops out a 2440 kg/hr .. but it's needed. It could be some interactions going on with the intercooler, don't know. HOWEVER,my datalogs shows variation with the boost along with MAF in the same way, in other words, you can plot both curves and they vary at the same (time) points in the same way.

 

[2L8V8_4sho]

As stated by Tim if you run the MAF pre-turbo/supercharger then you should ideally use a boost bypass valve that recirculates the boost instead of just venting it into the atmosphere. If you vent the air into the atmosphere with pre-turbo/super you'll get a temporary rich condition due to the absence of the already metered air and the (now) too much fuel which could result in flames out the tailpipes (which could also ruin your cats if you're running cats.)

 

[Toolman]

Since I am not running cats, I opt for the cool flames!

 

[kzoosho]

Since I am not running cats, I opt for the cool flames!

me toooooooo sweeeeeeeet i cant wait .. so tim have you got anywhere with the pipping for me?