Frank 993 C4S

My recommendation is to take it a step at a time and slowly work yourself up to the hp level in stages you desire. Headers and .9 bar boost spring are definitely a good first start and keep the car TUV legal. Going with the cat bypass pipe frees up some good hp again without significant expense and you should now be in the 350hp range.

I also recommend:
- buy new injectors or check their spray pattern (as stu mentions above)
- have the car dyno tested to make sure you have adequate safety in the AFR ratio (preventing you from running to lean and destroying the engine!)

If that's still not enough power, you can go EFI, bigger turbos, 964 cams

Enjoy the car but:

Metal Guru

Al, you say your aunt is monitoring the AFR meter while you drive? That's cool; is she a wrench?
The problem with trying to do that kind of real-time analysis is that the instrument will not respond fast enough to give any kind of indication of what is really going on. If you do have a problem, you will most certainly hear it before you see anything on the meter. This lack of response is compounded by the driver having one eye on the meter and the other on the onrushing traffic ahead.

al 965

The modern wide band o2 sensor and moniter displays readings almost instantly. The NGK unit is the same one that Y65MPH on here uses on his EFI engine and I think he feels safe with it and he recomended it to me. I am very happy with it, and with the senser mounted about 6" from the outlet of my GTK turbonetics turbo if I compare real time readings with the readings from doing data logs with the Inovate they are close unough for me. It is no harder for" as you said " my aunt to moniter it as it is for her to moniter the tach. She still uses the data monitering for tunning.

911addict

"It is no harder for" as you said " my aunt to moniter it as it is for her to moniter the tach. She still uses the data monitering for tunning. "

Its so funny that you tell us who is monitoring your gauges :-)
Is your grandma watching the boost-gauge over your shoulder at the same time? (Picture: Al hurtling along on full boost, with 2 grey haired dears falling about inside.)

I vote this thread as one with the most obsure detail.

Paul SA

Hi Guys
I have a 91 3.3 Turbo with 65000km's. The car is ex Austria, is LHD and I have owned for about 18 months. The photos show the car at Porsche Centre Cape Town having a new clutch installed. I have gone for the RS upgrade with a new flywheel to match and also RS engine mounts. The other photo shows the new RUF 19 inch wheels I installed last year. The mechanic pointed out that the front wishbone bushes are collapsing - need to buy complete wishbones at about $ 1200 or can one get aftermarket inserts?

A question I have is why does no one go the 3.6 crankshaft route to get more power and torque? My car is basically standard with only a RUF wastegate upgrade with a 1 bar boost spring. I have changed the door panels to RS using Southbound motor trimmers to do in black leather.

Cheers

Paul

Metal Guru

Elephant Racing make aftermarket front suspension bushings for a lot less than $1200.
Why is no one using a 3.6 crank? Cost could be a reason

Paul SA

Thanks Paul B

I will contact them, its not that urgent yet.

I have decided to put a new 3.6 crank and rods into my motor, have purchased a new one from Porsche and will get around to it. The old crank i can use in my 71 RS replica race car's spare engine so wont go to waste.

Paul SA

Polman

I have stripped a Scart Cat bypass from my 3,3 Turbo I purchased from Oxford in September last year....The 3,3 engine in original outfit is enough for me... It was mounted together with a G-pipe...Very great sound …and at least 25 extra BHP. Cat and G-pipe is for sale…cheap!!

JamesE

Sorry, but no where near 25bhp. Final exhaust gains nothing, CAT improves throttle and might add a few bhp ~5, tops.

The original CAT does suffer badly from blockages, due to fuel passing through the system, though. CAT removal is a good mod to do, but wont add much BHP.

Metal Guru

Is this opinion based on the Fabspeed mis-information video on their web site?
The stock suitcase exhaust turns 90 degrees, then 180 degrees so it's hardly the last word in low backpressure. It's also girthy (25 lb.)
When I switched to the RarlyL8 muffler I gained a lower boost threshold and power I could feel. It wasn't 25 bhp (more like 15) but it's all good, not to mention a 18 lb weight reduction right where it matters most.

JamesE

I did back to back, when I first got my car on G-Force's dyno. I consider anything less than 5bhp noise on a chassis dyno.

A straight through exhaust, no muffler, no Cat, is best for power. However, the sound is nasty. Adding back the rear muffler knocked a couple of BHP off, but made it drivable. Cat made biggest difference. This was comparing to a proper Swan-neck by-pass, not one of these tight 180deg 'C' jobs.

The bigger issue, as mentioned above, is that the stock Cat gets blocked as it does not like neat fuel which our cars pump out with the crappy CIS.

jeff91C2T

Good comments on exhaust related changes. I can offer my experience for those contemplating updates to the exhaust system;

I base lined my 91 Turbo after a motor rebuild and made 313 rwhp (.8 bar, Powerhouse headers and B&B muffler). The same day there was a all stock 91 Turbo except for a 1 bar spring getting dyno'd as well. He made 301 rwhp. At 3k rpm I was making 100 ft*lbs more torque. In short I was at full boost while he was just getting started.

I found that my B&B muffler was splitting at the seams. These mufflers are known to have flow issues as well as durability. I sacrificed the B&B and fabricated a Borla XR-1 straight through muffler. This was the only change. We dyno'd again and boost increased to .9 bar and I made 347 rwhp.

My take away from this was the exhaust system can be considered a significant variable in how boost is generated and power developed, especially at what RPM. A nice increase in area under the curve for sure. And add in the weight reduction and sound (if you like it louder) for an additional bonus.

Exhaust is certainly a good place to consider when looking at mod's...

JamesE

Sorry, I dont buy that. Those numbers are wrong. I have done this to death, same day, same dyno, every combination.

The standard muffler is not a restriction. I have no idea about B&B.

Mid bhp for a 3.3 1bar, headers, cat delete is about 360 flywheel bhp or 310 rear wheel bhp.

jeff91C2T

In your death testing, at what rpm did you reach 300 ft lbs of torque?

I don't think the final (peak) HP number is as important, as the method of dyno'ing is a major variable. It's the improvements we're chasing.

The old B&B muffler is a known "plug". This goes back many years and after this was determined there was enough noise they went on to offer a newer sport version. I'd call this a fix to what they were selling. I can't speak to the stock muffler and cat as on my car they were already removed.

As far as the numbers being wrong, a 3.3l at 1 bar with headers makes a bit more then you state. Many, many results over the years to back this up. As an example check post six on the thread below;

http://forums.pelicanparts.com/911-9...no-thread.html

Worth mentioning again, at the end of the day it's area under the curve that one might consider over peak hp. Look at the torque at 3.2k (in post six)....I'll take 300 ft'lbs 500 to 1000 rpm sooner over a few peak hp.

JamesE

You can work out the limits to this problem quite easily. You can do that yourself with a bit of simple maths.

So, if you could generate the extra 0.2bar 100% efficiently (which you can't) you would make less than 360 flywheel BHP. Your figures equate to 408 flywheel BHP. Thats nearly 50BHP from headers. Isn't happening.

I agree area is the key, but that doesn't change the fact that 1Bar + headers is approx 360 flywheel BHP. There is lots of BS talked around BHP numbers. The simple way to compare is to log some AX22 60-130 MPH times. There is enough data to be able to work you true BHP. So, log some data and we can workout what your engine is making.......