333pg333

Did I read that you're still running on 16" wheels/tyres? What size? I think that will be one of the reasons that you're locking up on the fronts. Too much speed with the new motor and it overwhelms your contact patch area. Not sure if you can borrow a friend's larger wheel/tyre setup to see the difference. Sure, you do increase unsprung weight but the benefits outweigh the negatives. With that much torque and power you will get better braking with a larger footprint.

Hood vents can help by relieving underhood pressure which in turn gives reduces frontal lift. Different vents work more effectively. I've seen some guy do comparisons with various vents in a windtunnel to lesser and greater efficacy. Splitter will add to this, especially if you have one with diffusers in there.

So you physically can't cross your arms? Is that due to shoulder issues? One thing that I do in my crappy street car which is a front wheel drive Nissan with typical poor lock to lock ratio, I preset my turn by moving my hands/arms off the wheel prior to getting into a tight turn. Hard to explain but here goes. If I am moving up to a 90 degree left hand turn I come into the turn with hands in normal 10 to 3 position. While I'm braking I move hands clockwise into approx 6 o'clock position. I can then turn full lock anti clockwise without running out of possible arm movement and comfortably make the turn. I mean this is just on the street in tight situations. You might be able to convert this over to tight turns on the track. Other small to medium turns you should be able to do this without shuffling unless you really have a massive limitation on rotational movement of the arms. Whatever works for you of course. On my track car we have 295 x 11.5" on the fronts and we don't have full lock available as we've put in a sort of steering limiter, yet I don't have to take my hands off the wheel at all...to my knowledge. Unless maneuvering in the pits.

Player0

Yeah 245/45-16 in the front and 255/50-16 in the rears.

I have a set of Cayman OZ rims here in 255/35-18 and 285/35-18 that do fit the car. Late offset rims though so I need to use 21mm of spacers on them. I'm putting in longer rear studs so that I can run them this year (already did the fronts last year). Using the rims on the street makes the car feel way more planted. The rear slips much less under throttle.

I'm super nervous about using these wheels on the track with the spacers and the stock 17mm ball joints (early 944 units that mount to the steel arms). I have really good studs and hubs but it will still put extra strain on the bearings and front spindles. The brake calipers swim in that open space as well. I've heard of failures on other cars where a caliper bolt snapped but having the rim close to the caliper prevented it from swinging all the way off.

I've been thinking that if I do this, I'll bite the bullet and go all in on late-offset, sell all the 16 rims and go 18s. Eliminate the spacers. Just haven't made that commitment yet. If I can't make breaking work better on the 16s with the spring rate/aero, I'll probably go that route for sure.

333pg333

Yes, that's what I'd be doing if I were you. Good luck!

Peter Vail

I am pretty sure I am now the owner of car #4 on the registry. I have recently pulled the motor from that car in order to get rebuilt. Working to get it back together by may.

Dutch944

I’m done.. 643HP 761NM at 1.4 bar.

not sure if there were others who ever did something similar, I still cant wrap my head around how this was possible

refresh951

Nice results. You may want to be careful running that high of boost pressure on a 16V. 20 psi on a 16V results in much higher cylinder pressure than an 8V due to increased VE and generally motor will not live long.

Dutch944

true! But that’s why I have a mapswitch; low or high boost.
low boost still give me 383hp and 510nm 😂0.5bar 355pk 444nm

0.6bar 383pk 508nm

0.8bar 441pk 597nm

0.9bar 481pk 620nm

1.1bar 548pk 658nm

1.2bar 584pk 697nm

1.3bar 611pk 708nm

1.4 bar 643pk 761nm

Voith

Nice! What CR and turbo did you use?

Dutch944

see here!

refresh951

I like the 0.8 Bar

Dutch944

so do I.. I’m now running 0.6 or 1.2 bar! Will do some testing in the next weeks, going to the track on the 14th.
Ofcourse I will be running low boost then

Thom

I don't understand this. IVC will dictate the dynamic compression ratio. Boost "should" have little to do with it if the ignition timing profile is adjusted "accordingly", taking into account the static CR.

People seem to recommend building a 16V turbo engine with a static CR no lower than 9:1, but IMO this is not the best way to proceed. I spent quite some time calculating different dynamic compression ratios depending on IVC and other variables for my 16V engine so that it could handle more than 18 psi reliably, and so far it has.
For what it's worth, Duke progressively reduced the static CR on his various 16V builds, as he probably found out that more than 9:1 was too much, and even if I am using stock 968 camshafts that are way "softer" than his super aggressive camshafts, I believe I have found a pretty good balance between outright performance, engine response, everyday usability and, hopefully, long term reliability, with a static CR lower than 9:1.

Chris White

actually the 8v heads are better at low to midrange torque than the 16v head due to cam timing and general design. As the RPMs go up the 16v heads do flow a lot better but peak cylinder pressure is not higher than the peak pressure of a 8v head at the same boost.

Thom

8V heads flow less, thus fill cylinders more quickly down low. Stock 8V and 16V cam profiles are IMO excellent for "low" CR and "high" boost applications.

refresh951

Thom - I am in agreement with you concerning CR. Never used more than 8:1 and a couple motors lower than 8:1 and had pretty good results. I argued this quite often as I recall.

My statement was about boost pressure on a 16V vs 8V. Many use boost pressure numbers comparitively between 16V and 8V motors. My point is that running 20 psi on an 8V with say E85 can be pretty sustainable (assuming proper mods, tune, ect.) where on an 16V motor likely not. Because VE is higher on the 16V (at a given boost pressure), it flows more and cylinder pressures are higher and more power is produced. A 16V motor run consistantly at higher boost (say 20 psi) is not very reliable in my experience. If you run a 16V motor consistantly at 20 psi boost pressure (with no knock) and pull the head you can see how much things are moving around by inspecting the head gasket. My experience says 0.8 bar can be pretty sustainable. Every application is different but just my 2 cents from my limited experience.