samana76

Hello everyone. This past Monday I attended my second ever track day event with my 1988 944 Turbo S. I purchased the car about 7 months ago in stock form and in these past few months have been doing a few mild upgrades to up the performance a little without hindering it’s magnificent daily drivability and reliability.

In essence the upgrades I did are the following:

- Fabspeed performance exhaust package (3.0" maxflo mufflers with deluxe tip, catbypass with downpipe, and turbo outlet pipe)
- Pauer Tuning TiAL 38mm wastegate
- Rogue's A-Tune Package
- Lindsey Racing manual boost controller set to 16 psi
- Autometer Boost gauge
- Innovate Motorsports Air Fuel Ratio gauge with wideband controller and oxygen sensor

Here is the video of the fastest lap I achieved throughout the day. A 1:58.16.


So I encountered a few problems, not many, but a couple, one of which could have been a really dangerous.

The first problem is when lifting off after accelerating for a while, like the long straight to the finish line in Laguna Seca, there is a loud ‘pop’ out of the exhaust. So loud in fact that in exceeded the maximum sound limit imposed of 92 db. The sound measured was 94.4 db. Below you will see a few clips edited together of this phenomenon. In the last clip you can actually see a pretty large puff of smoke coming out of the exhaust when the ‘pop’ occurs. Can someone please explain why it is doing this and what I can do to make it stop (if there is a way)? It could be problematic for future track days I would like to attend at Laguna Seca.


Another problem was that I found myself topping off the engine with about 1/3 quart of oil after every 20-25 minute session. On Sunday I did a complete oil and oil filter change and put 50 weight racing oil. Is it normal that the engine consumes oil (and this much oil) when pushed so hard?

Finally the biggest problem I encountered, fortunately for a very short moment, was with the brakes. On the last lap of the fourth session, which was about a 25 minute long session, right at the end the straight, when I was typically reaching about 105-107 mph before slamming on the brake pedal for Andretti Hairpin, the brakes were completely gone. I mean the pedal went all the way to the floor without doing a thing. And for the whole lap I basically had no brakes whatsoever. I was extremely fortunate that at the Start/Finish line before I reached Andretti Hairpin I got the meatball flag indicating I had a mechanical problem (exceeded sound limit) so I let go of the accelerator long before reaching the hairpin turn and began feathering the brakes (realizing just then I hadn’t any). I pumped the brakes many times and fortunately slowed down enough to make the turn safely. I then proceeded to complete the circuit and extremely reduced speed and off the line so that I could make it back to the pit area. I was very surprised this happened. I checked that I had not ruptured a brake line and lost fluid, but nothing was damaged and no fluid was lost. When the car cooled down (the wheels were cooking) the brakes were working fine once again and the final session presented no problems at all, although, of course, I was not pushing them as hard as the previous session. Did I boil the brake fluid? Or are the brake pad to be blamed? What can I do to solve any or either of these problems? Well, the brake pad, I would imagine I need to replace them with racing pads, but was that really the problem? If so what pads do people use for track days? Has this ever happened to any of you? I really need to understand and solve this problem before I do another track day.

Thank you all for reading this long post and, as always, thank you so much for your help and suggestions.
Igor

David Floyd

Straight thru exhaust your going to get some pops, agree with Rob on the brakes, oil consumption sounds normal

Rogue_Ant

Yep, the pop is fuel burning in the exhaust (which is why you see a bit of black smoke on the last drive-by). Extremely common on turbo cars with straight-through exhausts. This is more likely to happen if you do not let completely off of the throttle during shift. You could also try enleaning the fuel mixture a little bit (go to FQS position # 2).
I also suggest running a resonator where the cat was.

333pg333

Lol...welcome to 951ownership. All sounds totally standard practice to me.
Pops have been covered. Wait until you discover E85. You'll get flames!
Oil, yes these cars churn through it on the track. Do you have a decent catchcan? What is the 50w you're using? Would be worth considering some sump baffling especially for that track. Also upgrade your oil cooler. Really important!
Brakes...many of us have had that code brown moment where the pedal goes to the floor. You should upgrade to s/steel brake lines, race fluid, race pads and ducting to the rotors. Even then I didn't have a perfect pedal until I went with slotted rotors. It's also easy to introduce too much heat by over using the brakes. Not saying you're doing this but something to be aware of.
What suspension do you have?
Must be a great track. Love to drive it one day.

jerome951

Long ago when my TurboS was stock I'd get brake fade when overusing the brakes. Make sure the strut-mounted air deflectors are installed and use a good quality racing fluid (I use ATE Type 200/Gold as it's relatively cheap) and bleed shortly before the event.

As a 2nd DE driver you probably don't need racing pads unless the pads you have are crap. Pull the pads and if they look shiny (i.e. glazed from overheating), get some better pads for the track. You can rough these up on concrete and use them on the street.

At this point in your learning cycle you should focus on using the brakes less, not more, and carrying speed through the corners.

As others have said, the pop and oil consumption sound normal. My wastegate outlet points downward so I get a nice flash of flame from under my car occasionally. Scares the other racers so gives me an advantage. ;-)

LUCKY DAVE

You have committed the time honored track car mistake of increasing engine power first when you should have increased chassis performance first.
Your brake fluid boiling experience sounds about right at Laguna with a stock street car, Laguna is notoriously hard on brakes.
The brake fix is as noted by others, looking at your vids you're parking it on corner entries which is (A) normal for a first timer (B) cooking the brakes more than usual for this track. More seat time will help this, so will upping chassis performance/grip so you don't have to brake so much.
Oil consumption sounds about right, expect to add some after every session.
Keep at it, it's the most fun you can have with clothes on

URG8RB8

Igor:

Looks like questions have been answered, just wanted to say nice progress in a short amount of time. Keep up the good work!

jerome951

Oh, forgot to mention..

Make sure your rotors are on the correct side. The vanes are curved so that air flows from the center of the rotor outward. Reversing them backwards will cook them in no time. I've even seen professional shops put them on backward.

MC951

As previously mentioned, you should bleed brakes prior to an event and if you overcook them like you did, it’s a good idea to bleed them again before going back out on the track. It’s easy to do and considered basic maintenance like checking the oil level and air pressure and brake pad wear.
As for pad choice, there are a lot of them out there. I’ve used, and been happy with, Pagid orange pads although they are loud and squeaky on the street. I just picked up some Porterfield pads and will try them at the next event. They’re much cheaper than the Pagids at about half the cost.

LUCKY DAVE

I have been using Hawk DTC-70 pads the last couple years, with good results. They cost about the same as Pagids, the initial bite is comparable to Pagid blacks, but a bit easier to modulate at threshold. Heat tolerance seems about the same.
In addition, with the DTC-70's I seem to get less rotor surface cracking (not none, just less) than with any of the various Pagid compounds I have run. I have found solid OEM rotors are the most crack resistant, avoid cross drilled or slotted for serious track use.
Some of my 911 fiends swear by Porterfields, I should give them a try.
No track worthy pads are street friendly, squealing like a stuck pig at less than full effort. That's just the way it is.

333pg333

ps...can't believe that Pop transgresses the Track DB restrictions. It's a damn racetrack and that isn't loud by any means. Sounds good to me. Miss that sound.

Oddjob

Yeah, I dont think I have ever heard of sound restrictions below 100 dB before, leave it to Kalifornia to go over board on that too. Amazing that you were even allowed to run gasoline powered cars.

An occasional backfire on lift-off is relatively normal. On every shift, its running too rich. If you dont have an AFR wideband, at least check your plugs - guessing they will be charcoal.

If you run on the track, use high quality track compound pads and a good brake fluid.

Oil consumption is an engine condition indicator. The more worn the engine rings, valve guides/seals, and turbo seals are, the more oil the engine will use. Under a quart a day is pretty good for a 944, over is telling you something. Also, keep an eye on hot oil pressure, at high rpm load and at idle.

David Floyd

Here is a clip of my car and pop, 3" exhaust from turbo back, with a second small round muffler in place of the cat. The second muffler eliminated drone at highway speeds and mellowed the note, would take care of your sound limit at the track

Iridium

Laguna kills brakes. You are boiling your fluid, you need better fluid and venting to the brakes. Don't skimp, and reflector aren't enough for Laguna, you want to duct them. Run good race pads.

Some will tell you it's overkill, but it only takes once and you'll stuff the car and be lucky not to get hurt. Don't skimp on brakes, especially with Laguna as your home track.

samana76

Thank you everybody for your great advice and comments and positive feedback. I truly appreciate it.
I apologize with everyone for not writing sooner. This past week has been quite frantic and I was not able to get back to thank everyone.

I value highly all the suggestions everyone has given and I will definitely upgrade the brake pads and brake fluid before my next track day. I will look into the rotors as well but first want to check if mine are in good condition.

This weekend I will also try to lean the fuel mixture a little bit as Joshua suggested - although it will be difficult to test the "pop" problem on the street, but I'll see.

I have one more question which is track related. I realized there really isn't a good location to hook the car up should I need to be towed on the track. Where would you guys suggest I install a tow hook so that it isn't to prominent as I use the car regularly on the street as well - so something that doesn't poke out too much or that can be attached and removed easily just for track days.

Ah, I was almost forgetting, some of you are amazed about the Laguna Seca sound restrictions. Indeed there is a coalition of people that unfortunately are trying to do whatever they can to basically shut down the track. One of the cards they are playing is the sound restriction. Basically they were able to lower the sound restriction to 90 db for most of the year. There are only about a dozen days throughout the year where the sound restriction is raised to 92 db. I have never exceeded the restriction except for that one time (which saved me from possibly going off at the end of the straight as I began slowing down before the hairpin turn right when my brakes faded) due, I believe, to the "pop". I will try to get that corrected and next time I go to the track I will request to have the sound measured.

Thank you all again.
Igor