DJF1

As most of you have probably realized I'm the unlucky pb that owans the 91 S4, that Colin displayed its damaged cams and lifters on the "not for the faint of heart" thread... No I did not intend to get new cams, as tempting as they were, budget has exploded into pieces for this year...

But, since this happened, twist my arm and we went with a set of the stage 2 beauties that Colin has produced.

I have been driving the car since last night. First impressions are that these cams even with my dead stock configuration worth every single penny.

The Sound: changed slightly, a bit more brawnie, rough idle just like my race car. Love it! I think I may bump the idle by 50 rpms or so for the sweet spot, but you cant help but smile at the traffic light with the car going brap brap brap, knowing that something interesting is under the hood.

The butt dyno:
I picked up HP+ torque. No ifs or buts about it.From idle the pick me up and go even on the standard 2nd gear start has much improved. for sure more torque between 2-4 grand, very usefull in traffic.
On WOT from the start it pushes me back to 4K rpm, then the torque flattens ( I guess that is where I need a new exhaust, but wholly, after 5 grand it reminds me of my 993, it revs very hard all the way to the redline, picking up speed at a much faster pace than normal.

These 2 differences are very pronounced and especially on the top end it feels amazing,,, could not stop grinning and pushing it just to feel the same rush. Only problem is that at that point the car is doing lots of speed for our back roads so I had to back off...

As a conclusion, my misfortune was an opportunity and even though the dog house is looming over my head for this expense, it is for sure worth it and at a lower cost of new GT cams...

928mac

I am sorry that you had such a nasty repair Danny, and no I did not know it was anyone that hung out on the forum.
I am glad Colin got it straightened out for you so quick.
Thanks for the review of the cams, I was wondering if the grind was wild enough and from your explanation and the brap brap idle they sound perfecto.
When it is time for me to get cams, Colin and I will talk.

danglerb

More power is always a lot of fun.

Mike Frye

Has anyone done a before vs. after dyno of just the cams being changed?

SMTCapeCod

Is there a ECU remap/sharktune that goes with the cams? If not, seems like there would be more to be had...

DJF1

oh there is no doubt that a remap etc needs to be done. In my case it was not a planned upgrade but more a need to replace and go as the car is my daily driver..., but yes next year at some point for sure tuning is on the horizon...

docmirror

If the batt was disconnected for more than 10 minutes(I expect), then your car will recharacterize itself somewhat(within parameters of the LH programming) to the new cams.

the flyin' scotsman

Was anything else done to add to the performance?

Bill Ball

That was fast. Nice work. Enjoy!

dr bob

Danny--

What did you use for lifters and springs? Just curious...

Lizard928

We did one on TerryGT's car but his stock exhaust was at the limit and it made the same power as the cats killed all the flow. I will be installing headers and a full dual 2.5" system soon. Once I do that, the car will go back to the dyno and see what it makes. Again, no tuning was done to the car at this time.

There is at this time not a "chip" to just plug in. The car would definitely make more power with a retune. The mid range needs to be fattened up and the upper RPMS leaned out some.

The battery was disconnected yes, but the learning does not adjust the map up/down at specific points that I have noticed. So tuning is required.

No, nothing else was done.

Springs are lindsey racing springs that we had a group buy on earlier.
Lifters are good used lifters that I inspected carefully.

Unfortunately there was a slightly tighter budget, along with a real time crunch, we had no time to be able to get in the light weight lifters as the car is a daily driver. However I have been using good used lifters on two other installs and have seen zero problems arise from this. This is one of the reasons I went German Chill Cast on these camshafts so as to be able to run stock lifters and not specialty ones.

DJF1

Colin, I ave been thinking about the results from Terry. I'm very puzzled by them. In my case, the difference is so pronounced that there is absolutely not a chance that the car is making the same power as before...
I really compare it with the change that I use to experience when I had both my 993's. The stock one was good, the race car a different beast in terms of power.
Yes we are not talking about 50+ hp here, but by God, there is a considerable chunk that was found here...

Lizard928

Danny,

It is possible that Terry's stock cats are partially clogged for one reason or another.

There is something else that I have run across. With the flappy left closed the car accelerates slower in 1st, 2nd and 3rd compared to the flappy pegged open. Yet on the dyno the car made the same power regardless. These cams allow the engine to breath much freer. So the lower gears where the engine can actually rev faster it leads to much faster acceleration.

Personally I like the way these cams change the performance of the 928 regardless of the additional power they make.
To give those of you an example of this. Go and drive a 1985/85 Euro S 5 speed. Then go and drive a 1987/88 928S4.
While the S4 generates more power, the Euro is a much funner car to drive and begs to be held at the upper RPMs more because of the way the engine responds.
These cams bring the S4 into the Euro area for power and fun! Instead of hitting 3500 RPM and slowly accelerating, they hit 3000RPM and the car gets more acceleration.

Another good example of this type of performance change was when I drove a 350Z It had amazing torque off the line but quickly petered out. Yet when the car is put on a dyno it shows good power numbers because the engine is being forced to rev at a slow rate for generating a good graph.

the flyin' scotsman

Very interesting observations Danny.

I had a set of colins cams in my hands this year but didnt pull the trigger........may have to revisit the idea but like many/most were waiting for Gregs stroker bottom end to be fully available

docmirror

The O2 sensor sets a specific mixture value. When compared to the MAF values, the LH provides a pulse width equivalent to that which is required to satisfy the mixture ratio.

Provided you are taking in more air with the new cams, it will be sensed by the MAF(that is it's job), and the LH will widen the pulse width to maintain the correct F/A ratio so that the emissions are correct.

Which is a long way of saying; 'yes it does'. However, in my first post I did qualify the statement that it falls within the parametric limits on the original LH.

You actually confirmed this with your 'butt dyno' statement. If you are getting more air(new cams), you are either getting more fuel with it, or you are running a super lean mixture. Since the LH will not allow a too lean mixture to affect the CO and NOx, it will calibrate the injector pulse width accordingly.