fuel/air mixture question, when changing headers and muffler

[mark '87 930]

I just recently replaced my stock exhaust for a B&B. So no more Cat. or stuffy muffler. I also just purchased a set of GHL headers which I'll be doing in the next month or so to come.

My question is this, with the better breathing exhaust, it should be taking in more air no? Would that not then require a richer mixture? If so, I presume (By presume, I really mean hope) it's the simple turn of a screw on the CIS system?

[RarlyL8]

The air meter plate will work in conjunction with the WUR and the fuel head to deliver the proper mixture regardless of the mods. You should need to do little more than verify your mixture readings at idle and on boost.

[mark '87 930]

How do I go about doing that. What tools do I need?

[klaucke]

You can use a wideband Air/Fuel meter like an LM1 to monitor your air/fuel ratios, and adjust your mixture accordingly. I know the air meter should, theoretically, account for the increased flow, but other intangibles (such as the inertia of the meter plate) make it impossible for it to account w/ complete accuracy. Similarly, carburators should in theory atomize more fuel with greater air flowing them, but you still need to rejet carbs when you do exhaust mods that result in greater flow.

[KCinBR]

I'm no expert by any stretch of the imagination but,.....I see your car is an 87 model and probably has a DME box with a chip. I would think that a performance chip like the ones by Steve Wong would be in order. they are available on this site or at 911 Chips.
If you have a special need Steve can custom program a chip just for you

[javadog]

Assuming he is talking about the '87 930 in his signature line, it has CIS, not Motronic injection. Therefore, he isn't going to be able to do anything with a chip.

Install the exhaust and have the CO set with a 4 gas anaylzer. If you have access to a dyno as well, check the mixture through the RPM range under load, after you have set the idle CO.

JR

[mark '87 930]

There is no chip. JR, you are correct, it is a CIS based vehicle.

I don't have access to a dyno (not without paying for it). So maybe I'll do that after I get all of that installed.

I'll also look into the LM1 gauge.

[RarlyL8]

Adding an aftermarket exhaust system should not constitute a trip to the dyno. Just get an A/F gauge and verify your ratios throughout the operating PRM of your engine. If your car is in spec now it probably won't change. Be sure to install the gauge BEFORE you make the changes to see what you have now.