ptuomov

Yes. My garage is too big for the two of us, me and this stock long block.

Spare parts are in the mail for debugging. I am missing the Porsche meeting today taking the car apart. Sucks.

On other news, Tass made me a new part! Check this out, better than stock fuel pump cover! I was so excited to get the part that I forgot to pay him. He's probably thinking now WTF what's up with this guy! ;-)

Old vs. new:





And here's vibration dampening coating "Spectrum" being applied with scientific precision to the inside:

John Speake

Louie has a spare SMAF in stock. He would also be able to test your SMAF to see if it is the problem.

I have known one MAF to fail on a s/c car that had part of the boosted side of the intake blow off on shutting the throttle quickly (due to faulty blow off valve). It was unrepairable.

ptuomov

The MAF screen was crumbled inside the outer sensor housing.

I finally got some use out of my stainless steel cats cats and used them to straighten the screen on my workbench! ;-)

The sensor wires themselves are protected inside the inner housing and look intact.

John Speake

Hmm, that was some back pulse ! The MAF that failed on the s/c car did not damage any of the sensors in the airflow, but seemed to kill the main electronics thick film circuit. There is a small air path (about 1/16" dia) from the sensor assembly into the area underneath the black lid that holds the electronics.

BC

I think this show that you need to properly integrate a large enough blow off valve. Maybe two.

ptuomov

I have TWO (2, zwei) Bosch Motorsports bypass valves. One of them is enough to work on 500 hp 30 psi four banger. I think I am covered. Consistent with this, the boost doesn't spike much when I shut the throttle, the peak hold boost is never much higher than the set point.

My most likely hypothesis is that the 18 psi boost blew off the MAF out of the lower boot an instant before the throttle was closed, and in process the ring that holds the screen back got loose. Then the throttle shutting and the shock wave wrecked havock with the scree dangling sideways, it probably has a much higher air flow resistance sideways. The mangled screen was then blocking the air flow at one spot and forcing a bigger fraction than normal of air flow thru the inner sensor housing.

I am still hung over Carl's party last night. Powered by Advil, I've had the turbo system cold side on the floor today and now it's back in the car. Time for a test drive, I'd probably even pass a breathalyzer at this point...

John Speake

The MAF was blown out of the lower boot before you disassembled ?

ptuomov

I assume so, since it came off without me loosening any screws and also because we heard a pop on the dyno when the trouble started. But can't ever be sure, since it's not like you can see the MAF boot, really.

Just did a long test drive and visited the Boston 9/11 Porsche party. Lotsa cool cars. Mine was filthy and with a cable hanging out of the window, fuel pump cover off, etc.

PorKen

Delete the bottom screen? Heck, delete both.

Has anyone actually tested whether removing the top one makes the MAF read incorrectly? Reading differently than with shouldn't matter with a custom tune?

John Speake

Removing a screen increases the voltage out so there is some resistance there, so the air moves faster through the MAF on my constant speed fan rig.

I would think that the registered increase accurately reflect the increase volume of air that then passes through.

hacker-pschorr

This one?

http://www.034motorsport.com/turboch...n-p-18712.html


Stock boot or did you upgrade to the unit George Suennen had created through 044?
http://www.034motorsport.com/fabrica...t6e88t3bqptor3

I wonder if high boost applications would benefit from t-ing off this piece to a BOV. Downside to this idea is bleeding off post IC air, maybe use an adjustable one that only opens at the absolute peak of boost.
It would be interesting to have a boost log between the MAF and TB. Mike already has at least eight different locations I'll have a MAP sensor logging pressure on my car.

Todd didn't have a lot of miles on his S4 at 30psi before going to a MAP based Autronic system. So not a lot to compare to.
Since day one Todd has been using one of the big TiAL units like this:
http://www.tialsport.com/prod_bv_50.htm

I'll be upgrading to this unit too.


Tass - that cover looks awesome!! I would be interested in one on my car, maybe Todd too. Even the 044 pump can be a tight fit under the stock cover.

mickster

Man this thread is awesome. And the torque numbers are just mind-blowing. What a setup and what an engine...

ptuomov

John's plenum box has some pretty trick stuff inside, it's not just a box. It's got baffling and inside shape that looks nothing like the outside shape. It was designed and tested with the MAF screens on, with the MAF screens regulating the airflow to controlled level of turbulence. I don't know if the screens are necessary.

I think (but do not know) that a controlled level of turbulence may be important in a situation where the MAF may get the same amount of air flow at the same rpm in two different ways: small throttle angle with higher boost or large throttle angle with low boost. I need the same mass air flow measurement for both situations, since it's the same cell on the LH map either way.

John's talked about Reynolds numbers at different points on the flow path so he's probably thought this thru.

Assuming that removing the screens would not have any adverse impact on the accuracy of the MAF, there's still the question whether there's a flow benefit from removing the screens. It's true that removing the screens will give an increase in flow in a flow bench if the MAF is tested in isolation. However, this is not necessarily the case when the MAF is tested with the throttle body and intake manifold attached. The MAF is likely not the binding restriction, much like the throttle body is not the binding restriction on otherwise stock manifold. If someone is doing flow-bench development of these stock parts and doesn't mind sharing the R&D results, I'd be interested in hearing about the results.

I verified from the data logs that the MAF popped off from its boot an instant before the throttle was closed. The boost started dropping before the the throttle position changed and while Dynapack was still increasing the revs according to our programming. Nice to have some logs in trying to figure out what's going on! There's no reason to believe that my two bypass valves are in any way insufficient.

The yellow line is run during which boost suddenly drops off when the MAF pops out of the boot and causes a boost leak. The leak is small because the MAF can actually fully come out of the boot since the plenum box on top is attached to the block via brackets:



I am running dual Bosch 110's, part number 0 280 142 110. The 710N in your link is the part that is stock on Audi's, I think. It's my understanding that the 110 has a stiffer spring, which causes the boost to drop less during shifts. Both are mature, production quality units, with the earlier model's flaws fixed and the choice between the two is mainly driven by shift behavior and one's preferences.

Bypass and blow-off valves are another topic in which I have opinions that differ from most people's opinions. Call me crazy or something, but here's what I think:

1. Bypass valves are superior to blow-off valves. There are a number of reasons why car manufacturers don't use blow-off valves in their turbo cars.
2. Most (but not all) aftermarket bypass valves are crap while the current Bosch units are not. (Some aftermarket units with a selection of springs are ok.)
3. If one's Bosch bypass valve runs out of capacity, one is usually better off adding more Bosch valves than going to aftermarket units
4. Many people leave speed on the table by using bypass valves with too weak springs, causing excessive boost drops during the shift. The purpose of the bypass valve is to relieve only just enough pressure that it doesn't cause problems to compressor or the ducting.
5. If your intercooler has excess capacity, it's better to bypass the air after the intercooler and feed it to the compressor inlet. Why? First, air is compressed and it gets hot. The intercooler cools it to merely warm, and now it's warm and compressed air. The bypass valve vents the air to the compressor inlet, in which it expands. When expanding, the air cools dramatically and is now cold, colder than the ambient air. This cycle is great if intercoolers have excess capacity but not so much if the intercoolers don't have excess capacity, for obvious reasons.

I know may people disagree with me on the above topics, I've debated these points in the past over beers a couple of times!

The silicone MAF boot looks like a nice unit. However, based on one day of thinking about this, I don't think ther problem is with the stock MAF boot. The problem is with the MAF housing itself. The problem of MAF popping out is really IMO caused by the fact that the MAF sensor housing has no "lip" in the ends. Dave Lomas has a good idea, namely making a clamp-wide groove to both ends of the MAF. The groove doesn't have to be deep to be very effective in holding the MAF attached to the boot. I am thinking that JDS should offer this as an additional-cost option in their super MAF product.

When you get around to logging your pressures, please post the data. It's not directly applicable to my S4 engine, but it'll give some indication of what's going on in there. (Also, let us know when you get more pictures up on Todd's twin turbo.)

It's beautiful, for sure. Since he charged me $0, he's unlikely to make a profit on it! ;-)

Imo000

Those Bosch bypass valves are standard on the VW/Audi 1.8T. Just looked at one yesterday while changing the spark plugs. I can't imagine how they cna handle 500hp as the opening is around 2cm. I have two on mine (different make) and only making 400hp at the crank. With only one (a 300ZXTT) was nto enough, it kept pushing the pipes apart. I think you need to get one or maybe two very large bypass valves and and get rid of the Bosch ones.

PorKen

Any screen will reduce airflow in a system. On the stock airbox, there is at least a short section of straight pipe before the the sensor for the air to calm somewhat?

Does your aftermarket brainbox have a dual rev limit option for 'no-lift shifting' to keep the turbo spooled during shifts?

I did this with LH22 with a little programming, using an unpublished input for the clutch switch. It makes full throttle, near redline shifts nearly as fast as an automatic. (With LH23, I would reuse/reprogram the auto-idle-speed-drop input, pin 30.)