Hi John,

At what boost should a Stage2 turbo with MAF and other mods make 340rwhp?

I've got mine set at 16psi, and I haven't dynoed it again yet. My head is stock, no porting, no O-rings, but I'm running a wide fire-ring head gasket. I'm not sure if I want to crank things up to 20psi+, I've heard a lot of stories about blown head gaskets.

I tried turning the boost up to 17psi, but my seat-of-the-pants dyno felt no difference from around 15psi to 17psi. The tuner that was helping me set up my A/F asked about the specs for my HR Stg2 turbo, and wonders if perhaps the additional heat generated at higher boost is offsetting the benefits of further compressing the intake air.

According to the A/F readings, my mixtures are safe, and I should be able to dial things up. Could my turbo be the limiting factor? Need to vent my header panel to allow more airflow through the intercooler?

 

Everything running at 100% your can make 340 @ wheels at 19-20 PSI of boost. Caution though you may not have enough fuel to do so. We set the 'safe' limit to 330 @ wheels on stock injectors and for the Stage III MAF.

 

David & Ian, I've got similar mods to and ran into the 300rwhp leanness barrier. I put down 290rwhp @ 12psi last June. Well, I really had it set to 13psi peak-boost, but lost 1psi of boost as it got to the power-peak and redline.

That would translate to 340rwhp at 16.5psi of boost.

But there's no way I could run that. The leanness up at the high-RPMs would kill me (actually it did). Derrek fiddled with the fuel-pressure and ARC2 to no avail. Nothing could get rid of the leanness up top (and not make it too rich in the mid-range as well).

I'll try again after I upgrade to the Ver.2 of the ARC2 unit.

 

Thanks Danno,

I'm probably in the right ballpark, the car certainly feels like everything is running perfectly. I'll see what the dyno tells me in a few weeks. I'll do some runs at various boost levels, and monitor air:fuel.

The fuel side seems to be set up now, perhaps I should now pay more attention to the ignition side? Danno, I remember you saying that the APE Stg2 chips are programmed for too much ignition retard. A lot too much? I just sent you an email, to ask your opinion of the MSD BTM (Boost Timing Master) ignition system. Anyone have any experience with this? It allows you to dial in how much retard you want for every pound of boost (1-3 degrees per pound, up to a total of 15 degrees). I'm also looking for peoples opinion regarding the potential benefits of simply installing a high-output coil in an otherwise stock ignition system. I've recently replaced my ignition leads with new factory ones, and I'm considering purchasing an MSD Blaster 2 coil. Thoughts? Waste of money?

 

I still can't fugure out why you cannot get it set right, or close. I would try 40psi of fuel again, and try and limp it onto the highway. Don't fiddle too much with the settings, just get it close enough to rach the highway. Then, try and get to 4th gear at 55 or 60 mph and start playing with the throttle and the ARC 2 HIGH setting. Once you get stoich while crusing, try some slow acceleration runs while still in 4th gear. This is where you will start to knock back the high, and up the mid. Once you have it close, go ahead and come off the highway and try the low setting. You will get it.

When I tuned mine, I messed with it daily for 2 weeks and could not get it. I finally set everything at 0, reset the fuel, and headed out on a road trip. I limped it onto the highway and tried to set it up in reverse order, going high to mid to low to accel. By the time I got to where I was going, I had the tune nailed.

I will try the 48lb injectors and we will see what happens. Thing is.. it will probably be June before that happens.

As for the Blaster 2 Coil.. I have on on order. More spark cannot hurt. I am not sure about the MSD pack or timing control. With that much cash into the system, you can get custom chips mapped to the car, and still have the power from the Blaster 2. (That's my thought and plan anyway!)

 

Well,

Another update. My local Porsche Dealer had an idle adjustment screw in stock so I picked it up. Like I said before, my idle screw was broken in half, and the car was overrevving to 1300 rpm with the big injectors, cutting out, and doing it again. I drilled out and used a broken screw extractor (reverse threads) to unscrew the old idle screw. No problem. I popped the new one in and started my tuning process again. Wow!! I can control the idle now !! I simply dial back the screw to get an idle of about 950 rpm. I am even able to turn my fuel pressure up to any level without losing my idle. Amazing. Well, I put my fuel pressure at 40 psi and tried to tune the ARCII. I have to admit that it is a challenge. (Its also raining so that doesnt help) My setting are'nt perfect yet, but they are close Low 9:30 Mid 12:00 High 1:30 Accel 2:00 My boost is only set a 15 psi. The other great news is no white smoke any more. Perhaps the DME was sensing a lean condition with my idle screw too open and started cranking up the injectors?? STill mystified. I'll give you another update after a dry day of tuning.

 

Most likely it was due to an overly rich mixture. At high-boost, you had a large volume of air that flowed past the MAF. However, a lot of it went out the idle-adjuster screw, so the actually volume getting into the engine was less. But the computer didn't know that and just dumped in fuel for the original amount of air, resulting in a rich mixture.

When I lost my idle screw, the boost rushing out of that hole completely blew away the insulation under my hood. Gave me a clean 10" circle. It even blew away the adhesive!

 

Well, After a good dry weather day of tuning, my ARCII setting were very different than my previous post. I was able to unleash a lot more power with the low at 10:30, mid 2:30, high 9:30, accel 12:30. My fuel pressure is set at 40psi, and my boost is at 18 psi. The ARM1 at idle does not dither with my low up to 10:30 setting, but the car is much more powerful. The ARM1 reads last green, first blue at idle, but my car idles beautifully now at 1000 rpm with the new idle adjustment screw. There always seems to be a little tweaking required, but that is half the fun. There is nothing like being able to change boost, power, air/fuel ratios etc easily from the cockpit. I am trully addicted!!