87 930 engine rebuild dyno results!

[RarlyL8]

TurboKraft out of Phoenix makes the digital WUR.

The WUR on a 930 has a vent connection for boost. I'm thinking you could plumb in a manual boost controller to hold the reading to atmospheric until it hits 0.3bar (or whatever you set it at). Should be a simple inexpensive adjustable valve that you could test with a compressor.

Ask Brian Leask about this and see what he thinks.

[porschett]

Oohh. I think your method may work. I have a Dawes BC that I'm not using. Put this inline from the TB to the WUR. Set the BC spring to .5 bar (or whatever). Once manifold pressure reaches past .5, woosh, full fuel dump. Like you said, dumping fuel as a function of boost pressure is much better.

Now question is what psi to set it to? My car cruises around 13.5-13.8 AFR. Once boost pressure up to .3 bar hits, I'm around 12 AFR. At .5-.6 bar, I'm around 10AFR! and is maxed out on fuel dump. As boost/RPM rises, the AFR leans out until around 6000RPM, where ideally, I should be around 12AFR.

So is it save to be at 13AFR around .5 bar? If I time the release of the BC spring correctly, after .5 bar, AFR will slowly drop hopefully to no lower than 11AFR. By the time I get to 1 bar, the AFR should have leaned out to 12AFR.

Thanks for the idea!

[81 930]

I like the digital WUR idea and would love to get my hands on one and do some testing. Maybe after I get my "new" headers fabbed...

Using an EBC to control the WUR is a nice idea, but unfortunately it won't work for most 930 applications. If you examine the dyno chart for a typical street build (IA fuel distributor, K27 or K27HF, & headers) you will find that 1 bar of boost is usually achieved in the 3500 RPM range. When examining the AFR chart for said engine, you will notice that enrichment is not needed until somewhere after the 4500 RPM range. An EBC will not be able to delay the enrichment late enough because the engine will already be seeing 1 bar at 3500 RPM. I can manipulate a stock WUR to delay enrichment until full boost is achieved without even using an EBC. Here's an example that shows "the best you can get" using the WUR alone. The blue curve is my car with my fully adjustable WUR and the red curve is David's car prior to adding adjustability to the WUR enrichment circuit. You can see that my car delays full enrichment until full boost is reached.



It's a big improvment, but still not good enough. The engine still runs way too rich in the mid-range, which is not only diluting the engine oil with fuel but also giving away horsepower and throttle response. By using an RPM switch, the boost signal to the WUR can be delayed until the exact RPM range that enrichment is needed. I think Brent 930 from the C2Turbo board pioneered this mod years ago on his car. It's a relatively easy mod to do and I have come up with a slick way to integrate it onto my car. Check out the pics.





I am using a factory solenoid valve normally used to control the smog pump to control boost signal to the WUR. I have connected it in normally open (NO) fashion, so that its failure mode will be to provide full enrichment. The mounting bosses for the AAV work perfectly as a place to mount the solenoid valve. It almost looks factory, don't you think?

Once I get the cracks in my headers repaired, I will put my car back on the dyno and post the results here. Stay tuned.

[Craig 930 RS]

I just received this exact setup in the mail today from Brian Leask.
A quality piece of work!

Coincides nicely with the first day the 930 is back in business -

[porschett]

Here's the results after the Brian's RPM Switch mod...As you can see, the AFR curve is flat as EFI. This is running 1 bar and VP MS 109 and it is a little lean over 5500. Which I plan not going over anyways for the street and even if I do, it'll be a sec or two max. Seeing that max HP is around 5400, anything over that is wasted. If I bring it back down to .8 bar, I should not have any problems.

The original AFR curve was way below 10 (off the scale of the WB sensor) and caused a lot of rich stumbling as you can see from the torque curve. Now that it's 12ish, the TQ curve has smoothed out dramatically.


I gained 30-40 RWTQ through out the RPM range! So this puts it around 480HP and 475 ft-lbs*! * 15% drivetrain loss.

[Craig 930 RS]

What is your idle CO? This is pretty important to my setup which I will work on Monday -

Thanks!

[youngkang]

Subbing to thread.
That looks great!