Crappy Dyno Results on 3.4L Rebuild

[Lapkritis]

Originally Posted by lindy 911

Also, if it got hot enough to partially seize it's very likely it was detonating which pounds the crap out of the rod bearing. Could end up being the source of the noise from the right bank.

x2... same with the wrist pin.

[jungspike]

Thanks guys, I'll ask for new rings and look at the wrist pins

[jungspike]

Pistons and cylinders are off to EBS to be reconditioned.

[lindy 911]

Did you find the cause of the knock?

[jungspike]

Knock is from rod bearing.

[lindy 911]

Thought that might be the case.

[PFM]

Jungspike,

FWIW the dyno shop has some hand in this as well IMHO. On the dyno at the shops I have been at the AF ratio you had would have been cause to shut it down and resolve the problem not make another pull. We would then sneak up on the second pull after making some change to resolve the issue. If it stayed that lean it would be off the dyno and heading home with you.

[scarceller]

The O2 sensor at WOT can NOT cause any issues in the 3.2L Motronic. This is because the O2 signal is ignored in the following conditions:
- any injection pulse width greater than 9.6 milliseconds
- RPMs > 5120
- And most importantly if the WOT switch is closed.
Any of the above 3 conditions does not monitor the O2 sensor.

But you should check these things:
- With accelerator pedal to the floor check that the throttle plate is fully open.
- Also with throttle plate fully open check that the electrical WOT switch on the TB is closed.

It's possible that the WOT switch is not closing and thus you will not run out of the WOT maps in the DME, this results in power loss.

Also have you tested fuel pressure? The lean condition can be caused by low fuel pressure.

No matter you are way lean for WOT, the stock chip usually runs on the rich side at WOT down in the 12s AFR.

[jager911]

Considering taking my 3.2L to 3.4L, was your issue resolved and did you re-run on the dyno? If so, what was the final hp and torque numbers?

[jungspike]

Jager911, great question, because I just picked up the car two days ago.

I cannot report any numbers. Would I increase to 3.4L again? I'm not sure. The cost of just the parts for 3.2L to 3.4L conversion at a MINUMUM $2200 ($1200 to bore & plate the cylinders plus $700 for used 98mm pistons and $300-ish for rings), HP gain is the percent increase in displacement (6%=13 HP). It seems like there are a lot of other things that can be done that will give you more bang for your buck (cams, intake, chip & headers). But if you need new pistons, definately do it. My whole project (parts plus labor) came to about $7,000--which I consider very cheap. Unfortuantely, I will probably not dyno the car for awhile. I need to do some tuning and brake in.

As for the status of by engine: The stock flapper box is back on (took hotwire off). I did a couple of runs with a Gtech meter up to 5,000 RPMs. The Gtech and my butt dyno both say it is still not performing great. It seems to lack low end torque. It is easy to stall when staring out. I bought a wideband AFR gauge which I will install this weekend. I really don't want to do any driving until I get that installed. Last night I checked the WOT switch--it is not clicking and is rotated full counter clockwise, so I'll fix this first.

I plan on going through the whole Motronic system ensuring everything is operating correctly. I made a list of stuff to check, but off the top of my head:
- Fuel pressure
- Vacuum leaks
- Idle control valve
- Pull plugs look at color
- Disconnect O2 at idle and check RPM change.
Basically, go through the "Motronic Tuning" thread, and check EVERYTHING.

[jager911]

Keep us posted on what you find. $7k is really cheap for parts and labor and a warranty that fixed your issue. I'm planning to buy new Mahle hi-comp Ps&Cs, cams, bigger valves and headwork but evaluating if I threw 3.4L in the mix as well, I could probably get close to 250-260hp with tuning.
My budget is $10k doing most of the work myself.

[PFM]

Jungspike,

It will take some work to get the rings settled in to get the real results. Please go through the fuel system carefully as the dyno run was very lean. Also check the ignition timing with a known good light, I have seen 5 degrees between two lights that both had good names on them.

As for the delay to dyno I get that but the street dyno can cause troubles too.

Best of luck.

[jungspike]

Here is what I've did with "Crappy" today:
- Tested WOT switch (Ohms + click): checked good.
- Adjusted WOT so it clicks as early as possible (any problem with this?). It was the opposite; full counter-clockwise and not clicking.
-Installed Innovative LC-2 AFR Gauge (see picture). At idle and cruising around at 3,000 RPMs, AFR was around 14.5 +/-.5 (bounced around a lot, so hard to say exact reading). Under WOT:
2,000 RPM = 10.4
3,000 RPM = 11.5
4,000 RPM = 12.6
5,000 RPM = 13.6
I got these measurements from my Poor-Man-Porsche data acquisition system. I taped my GTech above my AFR gauge. Then my wife came along for a ride and videoed the GTech (for RPMs) and my AFR gauge. I did 5 runs and took the average. Data was very repeatable. I did not take it above 5,000 RPMs because still breaking in engine.

Builder said he turned up the fuel pressure a little and could dial it back, so I'm not too surprised that now I am running rich. My butt dyno confirms the very rich condition at 2,000 RPMs (I feel no power/torque). However, I thought the AFR would be invariant with RPMs.

Tomorrow I'll continue to check the rest of the Motronic. Oh, and don't worry the cardboard in picture will be replaced with wood covered in black vinyl.

Oh and my the way... my wife says to all the other wives, "Let your man buy the more expensive wideband O2 sensor with RPM data logging."


[IMG][/IMG]

[scarceller]

Some feedback:
- Don't alter fuel pressure from the stock settings. Not a good idea to do this as it results in some fuel maps not working correctly. Plus it will never fix the issues your seeing.
- At WOT the stock chip is setup to be slightly richer at WOT in the lower RPM area, it's common on the stock setup to be rich below 12.8AFR in the <3000RPM area and then lean out above 3000RPMs. However it's common tuning approach by chip tuners to target around 12.8 to 13.0 AFR across the RPM range at WOT but to do this the tuner MUST tune the WOT fuel map, you can never reliably achieve this any other way.

EDIT: skip this point, just saw you are running a MAF not AFM.
- The other possibility is that someone messed with the spring tension in the AirFlowMeter (AFM). Often folks open the meter and loosen the spring tension a notch or 2. This is NOT desirable and should never be done! Messing with the spring tension alters the calibration of the AFM. For example: if you loosen the spring tension it will result in richer AFRs but not in a linear fashion. It results in AFRs getting richer and richer as air flow increases. I wrote an entire document on the operation of the AFM, if you want the doc PM me with your email id.

Looking at te dyno result in post #1 I do think a fuel pressure test to confirm your fuel pressure is in order. Low FP can result in those lean WOT readings. As for the AFR curve over the RPM range it's not that bad, it's not so bad that you went slightly leaner in the 4800 to 5500RPM area. What's bad is that the entire curve is to lean.

You also mentioned matched injectors? What do you mean? Are these stock injectors that where simply flowed to be sure they are all flowing the same? Or are you running some sort of non stock injector?

Also, are you 100% certain you don't have a dead cyl? Like no spark or fuel in one cyl? A dead cyl would result in power loss with lean AFR since the dead cyl will pump unburned air (lots of extra O2) into the exhaust stream and the WBO2 will read lean. You can do a quick test for dead cyl at idle just unplug the each injector, testing one at a time, will result in RPM drop and the RPM change should be the same for each cyl as you test each. Also if monitoring the exhaust stream in LHS bank (cyl 1,2,3) with the WBO2 you will see the AFR go lean as you unplug an injector.

[jungspike]

I'm moving this to the Technical Section:

Crappy Dyno Run (Part Deux)

Why? It is not about rebuilding anymore. I don't want to wear out my welcome because I appreciate all your help.

Thanks,
Tim