911addict

My garage says don't remove it. Don't know why, could be to do with messing up the mixture, or emissions illegal....

Megatron-UK

On most cars, if the O2/Lambda sensor is removed, then the car usually runs rich to compensate for not being able to know the content of the exhaust gas (rich usually being safer than running lean) - so I would normally completely agree with that reccomendation. But most cars with an O2 sensor are EFI systems these days, what does the partly mechanical CIS system do when it is removed?

nathanUK '81 930 G50

It still affects the mixture somehow, possibly altering the control pressure.

Disconnecting the sensor is OK as long as you have the CO checked & adjusted if need be after disconnecting. Oh, won't it kill your cat (if you have one) if you do this ?

So maybe you shouldn't John.

Please correct/comment guys.

Diverwes

Where in Chicago are you? What Sub?

FastCarNut

Ah yes, I would still like to think of myself as a hip city-dwelling urbanite but I have to admit that we in fact moved to the burbs; Elmhurst.

I would like to thank everybody for contributing to the discussion, your insights are greatly appreciated. Any future mods will be documented and reported.

JamesE

The lambda is a complete waste of time. It does not work on WOT and can cause issues if you have adjusted your CO level in excess of factory spec. It was only really included to help the car pass emissions, rather than offer what we are now used to on modern cars with closed loop operation.

Muffler bypass is worth 5hp on a 3.3T and slightly better responce. Cat bypass made big difference about 15bhp. 1bar spring made about 25hp. A stock car with 1bar, cat bypass, and filter should make 360-375hp.

I would not add a cat to a car that didn't need one. I'm spending yet more money removing as much post turbo restriction as pos.

I have the LWT flywheel and it is no more difficult to drive than normal.

Headers are great so long as you makesure the wastegate circuit is efficient enough to dump boost else you'll get boost creep.

911addict

What is boost creep?

PS: James, i have sent you a pm.

Megatron-UK

Boost creep is when the wastegate cannot flow enough gas at high rpm/boost situations, so the boost will start to 'creep' up past what it is set to. e.g even with a 1bar spring it could well be 1.1 or 1.2bar.

I don't know the Porsche system, but this often happens on other engines when the wastegate is either old and not working properly and you increase boost, or when you fit a downpipe from the turbo that is much more efficient than the OEM design (some OEM designs are purposefully restrictive in order to eliminate this problem.)

cobalt

I think your a bit high with those numbers. A 3.3l with 1 bar spring, stock exhaust, cat delete and muffler delete should be closer to 350-355 hp. The muffler delete gains nothing but weight loss. The stock muffler is nothing but a can with 2 perforated pipes to begin with. The sport version of the same Dansk muffler just adds a straight pipe between the 2 perforated pipes.(they claim no HP gain) Some may also argue the filter adds nothing others say it may rob you of power. To bring the power up above 350 I think you would need to change out the stock exhaust with headers.

I would recommend modifying the air box by drilling 7 1 " round holes on the bottom of the box. This allows more air into the system and increases throttle response. I actually drilled out the box using a 1/2" bit and used a Greenlee hole punch to make perfectly round holes.

Most dyno numbers I have seen for 3.3l cars with fairly extensive mods were only showing 315 - 320 RWHP. These cars had B&B or GHL headers, 1 bar spring, cat delete and K27 Hf turbo and dyno tuned.

JamesE

Those where fly figures as measure by myself same day (Dyno Dynamics), same dyno. The stock muffler does add restrictions once bhp starts to increase. Once I added the headers (GHL) I saw no increase in BHP because of boost creep and not enough fuel. At this point I stopped f'ing around and went to MoTec. I have a file full of dyno sheets for all the mods i have done, including the above.

nathanUK '81 930 G50

James, did you dyno a CIS air filter/intake ? I would like to know which is best for CIS.

cobalt

I understood you were talking Flywheel numbers. I guess every car is different I have been told the Dynapacs are most accurate for these cars. I guess it also depends on atmospheric conditions and corrections used along with the overall condition of the engine when you start. The headers alone (at least B&B) do increase power and reduce spool up on the turbo. I have seen numerous dyno sheets on 3.3l engines and have never seen any evidence that the RMB increases HP. Although if the tests were done without a cat in both cases then I can see a slight hp gain. I would think with a cat in place all the restrictions would result there. I believe GHL has resolved their boost creep problems and the B&B is not an issue. It may be possible to see the numbers you are stating I just have never seen that much gain from those mods myself. Like I said the best gains I saw included a full header, cat delete, 1 bar spring, air filter, Billet BOV and HF turbo and they were just seeing 370-375 at the flywheel. These mods usually show equal Hp to the wheels as what is stated by the factory at the flywheel +/-.

Did you run a chart on the engine before you made the improvements and what numbers were you seeing?

911addict

Cobalt
I know you were talking wheel bhp, and most of us (inc. the Porsche handbook) talk about flwheel bhp, but remember that the book gives the 3.3 320bhp and you yourself mentioned this was conservative. So with a spring (+25hp) cat bypass (+15hp) we are already up to 360 conservatively. If you then add a few bhp for conservatism (is this a word?) and performance airfilter, we could easily be at James's figures, and that's before we look at headers or anything else.

cobalt

I will give you that one difference is Porsche has 320HP for ROW models and 315 for US. I honestly doubt you will see a +25hp increase with just adding a 1.0bar spring. I think you are looking at closer to 18-20 Hp on the 3.3l engines with stock exhaust and yes 15hp sounds about right for a cat delete. If you combine this with headers you might see a +25 hp increase with a 1 bar spring but not with the stock set up.

Y65MPH

I agree 100% with Anthony's horsepower claims. On a 3.3T with all the possible bolt on do-dads. 315 WHP is all you are going to get. The best you can hope for is to lower turbo spool RPM and increase throttle response. The only was to get big HP gains is to improve the NA side of the engine i.e. cams, head work, etc. But then you will hit a wall with the fuel supply from the CIS system. So if big HP is what you want look at EFI or Motronic. Then your wallet will set the limit on HP. Remember the Kramer K3 935's of the late 70's developed close to 900 HP out of a 3.3L. So the block can hadnle just about anything. I plan on finding out how much HP it can handle

Craig