Changed headers from B&B to Fabspeed today

[Speedy Squirrel]

This is a part load effect, not full load. The pressure in the exhaust is very unsteady. On average it is above atmospheric, but the pulses also go slightly below atmospheric under low load, letting air aspirate into the exhaust.

If you have CIS you don't care. You are pig rich all the time and there is nothing you can do about it. With EFI you usually run closed loop at part load, and then it matters. The false lean readings walk the adaptives rich over time.

[RarlyL8]

CIS is only pig rich if not adjusted properly. Any gap in a slip joint large enough to throw off AFR readings is unacceptable.

[911st]

SS, where is your O2 located and do you have a short straight through muffler?

[Speedy Squirrel]

Mine is located in the Fabspeed location shown in this thread. I agree that no leaks are the goal, but at WOT there is no aspiration as the exhaust pressure is too high. For CIS the part load leaks won't bother you much. You don't have closed loop control, unless you have the PWM lambda sensor. It has no adaptive, so it probably wouldn't cause much problem even with that. I know a lot of cars with slip joints and CIS that seem fine.

Pig rich might be a little
mean, but a lot of people ha their CO cranked up to richen up the top end. They are usually at 13.2 or worse at part load. That is pig rich compared to 14.7 IMO. EFI can easily do 14. That's why the fuel consumption is
so much better with EFI.

[smurfbus]

My CIS runs fine at 14.7AF part load and even 15.2AF runs fine part load. Over 15.3 it started to do hick ups on light load.
I hope my B&Bs will last but the WG pipe looks to be beaten even narrower where the turbo oil canister rests? Must have been some sort of fitment issue?

[RarlyL8]

Fuel consumption is generally not any better for EFI vs CIS if the CIS is adjusted properly. Problem is that most CIS is not adjusted properly. This has been covered in other threads.

The stock turbo oil sump tank will not fit with B&B, maybe someone tried to make it fit.

[911st]

Originally Posted by Speedy Squirrel

... I got rid of the slip joint because I have seen them randomly throw off the lambda sensor readings when they are leaking.

So you had the closed loop accelertion lean condition with the old slip joint but it went away with the woven style conector?

My first thought would have been there might be a need for some type of compensation triggered by throtle angle or maifold vac for times when acceleration is allowed under closed loop.

Otherwise I would think any acceleration during closed loop would naturally make for a lean condition at first untill the Lamda function could compensate.

I do not know that an O2 sensor can compensate that fast. Expecially if it is an older sensor.

Just a thought.

[pdx930]

My understanding of the way our lambda systems work is that they permit a relatively small adjustment to the mixture that is primarily determined by the cone shape in the airflow meter and the control pressure inside the fuel distributor just as in CIS without lambda control. As a result, there is no need for the lambda system to react in an ultrafast way to throttle changes while it is operating in closed loop.

That said, big air leaks into the exhaust at light throttle can certainly fool the O2 sensor into thinking the motor is running leaner than it really is and richening the mixture in response.

[911st]

Was refering to SS's EFI lean spot.

CIS suffers from a lean surge to a small degree with acceleration and dose not shift AFR's in any special way from cruse to accel or accel on boost AFR's. Just the meterin position changes with air flow. Some WUR's do lower control pressure with acceleration but not th 3.3's.



CIS turns the Lamda on and off mostly by throttle angle I belive.

[Speedy Squirrel]

Originally Posted by smurfbus

My CIS runs fine at 14.7AF part load and even 15.2AF runs fine part load. Over 15.3 it started to do hick ups on light load.

Yeah, after you bought an adjustable warm-up regulator, a wide range O2 sensor, and adjusted the crap out of it for a couple of weeks!

My own experience with EFI was about 3% better fuel consumption on my mostly highway drive with just injection, and about 6% with fuel and timing control. I could see where EFI could not produce any benefit though. It depends on the tuning, the hardware, and what you are after.

[911st]

double post, sorry.

[911st]

CIS at 14.7 and EFI / MAP can have the same AFR but that dose not mean they will get the same MPG.

The metering assembly on CIS adds restriction to the intake plus there is a lot of extra plumbing, twists, and turns. This adds work to the piston during the intake stroke. I think the term is pumping losses.

Then as SS notes, an EFI car can run more aggressive timing. Some run over 40 deg at cruse compaired to about 26 for a 930.

Also there is a much better ability to bend the ignition curve and part because it can be run closer to an ideal knowing that with intake temps and other changes in environmental conditions it can compensate.

Thus, more power is made with the same fuel.

Just changing the stock muffler to a low restriction can reduce pumping losses and increase MPG.

[smurfbus]

Cis has no overrun fuel cut which also makes mpg go down. my bl wur was really easy to get set. Two test drives was all it needed to get the cruise set. Now I need to hack up a suitable bolt to get the accel a bit richer. If anyone knows the thread on the bolt end that goes to bl wur please PM me.

I think I will go EFI later on but only because I like to tinker with my cars.

[Ed Bighi]

Ok. The headers have been for a couple of weeks. No leaks. As for performance compared to B&B, at least as good. But for me I've found other pluses. I run without a rear valance and a zork and I really appreciate a more even look to the tubing without those huge heater boxes. Also, I'm one of those guys who is obsessed with ease of removal and funny bent wrenches aren't my idea of things I would like to use to remove finicky nuts on studs. With the way the heat exchagers are done on these, a long socket is all that is needed. Or an extension with a flex joint. Getting a torch up there is a lot easer as well. Anway, I like them a heck of a lot more than B&B. I also threw in a two oulet muffler since they are made to be removed from the flange that attaches to the turbo. I like this since I don't really care for messing around with whatever is holding the flange to the turbo. At least not often. A 15 mm socket onto a nut on a v-clamp, loosen it, pop the muffler off, then slide the zork onto the same flange, is my cup of tea. It's also, like Brian's mufflers, one of those that's so even when seen from behind that I can run without a valance. I run my zork just under the bumper for clearance reasons and to provide an easier exit for hot air. Anyway, so far I'm pretty happy with his stuff. Easy guy to talk to as well.

[DDDD]

I am puzzled by this thread. This guy bought not one, but two sets of headers which are known to be inferior products to what is available.

I would have gone for the most power gains possible for the money, which is neither of these headers. That just seems like the point of putting headers on the car. Extra power.

It seems like a lot of rejoicing about settling for less.

[Ed Bighi]

Thanks for your concerns regarding my header purchases DDDD, but you don't need to worry. And my friend is very happy with the B&Bs. I am very happy with these. I feel the power is fine, the fit is excellent, and the heat every bit as good. The most hp for the money? I don't really care. I just needed heat with a little less lag and they did the job. As did B&B. As for buying 2 sets of headers, it's ok. Back in 92-93 I tried every muffler possible in my 911. Borla, B&B, Monty, some others, SSIs, back to stock exchangers, my own design, etc... Hence, I'm used to trying different things. Right now these provide all that I require. Easy to take off if need be. If something happens to one during one of my off road snow excursions, I can call them up and have a new set in 24 hours. I could join the cool header of the year club, but for me these suit me perfectly.

[fusionhead]

Ed, I want to thank you for sharing your experience. I was leaning towards Fabspeed before I read your posts but this really convinced me.

I've got a 79 930 and I ordered the Panamera Turbo/S/C4S Complete System: X-Pipe and Maxflo Mufflers with Dual-Tips.

I'm also ripping out my old intercooler and will be done with O-Rings and leaks that has been a pain to say the least, with turbo lag to boot.

You're criteria is similar to mine. I'm not looking for absolute top power. I want a trouble free easy to work on, quality piece that is held to tight tolerances. I don't want to hack or bend anything to make it fit and I want it to sound good. I think this is a winner. Thanks again for your very helpful post with picture!

I will report back when it's all done.

[fusionhead]

DDDD, I realize this is an old post but maybe you are subscribed to it.

So tell us, what is better than Fabspeed? I'm always looking for more data, information and ideas. You tear down Ed while not offering anything constructive. If there's something better I'd like to hear your opinion as to why. Or is it that the name Billy Boat on your Driver License?

[wcc]

Originally Posted by A930Rocket

I'm surprised they weld the O2 bung right before the turbo flange in both cases. Not the best place IMHO, but then you have to have one somewhere on the system to match the factory.

Anyway the fabspeeds look great. Let us know how the finish up and perform.

Since this thread has been brought back up, I am curious about this as well. So fabspeed, b&b, and even my glh set have a bung right before the turbo. I read on here somwhere that after the turbo is ideal spot. I plugged mine and put one in after the turbo. Is that still the censensus?

Fusionhead- *I think* they are refering to RarleL8 header design. See page one...

[RarlyL8]

The stock location for the O2 sensor is before the turbo on the J-pipe. My headers (yes RarlyL8 is what D4 is referring to I assume) have bungs located on both secondary pipes as an option when tuning. My mufflers all have a bung after the turbo and before the muffler body, for a permanent installation.
All these locations work but there is that rare but fatal possibility that an O2 sensor tip can shatter sending shrapnel through your turbo. I have one of these sitting on a shelf and man is it ugly.