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944S2 16V Turbo Build
Final pieces of the puzzle are coming into place, headers and cross over are back from coating, not the custom setup I originally planned but thats something Ill look at in the future. Fabricator is lined up next week for intercooler piping and exhaust/wastegate mods.
EMAP sensor installed as well which is tapped from the stock o2 sensor port
EMAP sensor installed as well which is tapped from the stock o2 sensor port
This car keeps throwing up curve balls but I guess that's the challenge of a build without heaps of off the shelf parts.
Apparently the Tial F46 wastegate doesnt play nice with the early one piece crossover pipe. I should have tried a bit harder to get a later 2 piece pipe but my fabricator snookered me by changing the crossover flanges to the 16V pattern rather than the headers to the turbo pattern. Im going to have to add the extra flange in to make it work for now.
Apparently the Tial F46 wastegate doesnt play nice with the early one piece crossover pipe. I should have tried a bit harder to get a later 2 piece pipe but my fabricator snookered me by changing the crossover flanges to the 16V pattern rather than the headers to the turbo pattern. Im going to have to add the extra flange in to make it work for now.
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This is turning out better than expected. I cut off the stock flange from the wastegate outlet pipe and it lined straight up with the new flange wed mocked up.
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I have a TTV flywheel that I was considering using. Thom are you saying that for a streetcar you would stick with the stock flywheel because it has better inertia? It has better inertia because the bulk of the weight is further from the center, am I following that correctly?Thom wrote: Fri Dec 20, 2024 10:34 pm -1.5 kg if I remember right, which with a KEP2 made a massive difference for me. Just wanted to somewhat warn you before you have everything buttoned up and figure out, possibly after spending further time on teething issues and on the tune, that the overall experience is eventually let down by excessive inertia in the rotating assembly. Out of the box the TTV flywheel may have the same mass as the stock flywheel but it is a rather crude design with a more or less uniform weight distribution over its radius and will cause more inertia than a stock flywheel. My machine shop had lightened both my former stock flywheel and my current TTV flywheel for me and although he got them down to the same final weight he found difficult to get inertia with the TTV flywheel down to the same level as the lightened stock flywheel, and I can feel this in the way the engine reacts to throttle inputs. I would say it's "just ok" by now.
With that said and depending on your experience and how you want your car to drive it may actually suit you fine. Here's just my real world feedback for you.
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Thom
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It is probably more a question of what sort of triggering you prefer to use, but since you have bought a standalone ECU I would suggest using the TTV flywheel for its 60-2 triggering. That's a no brainer to me especially with a 16V set up.944m3 wrote: Tue Apr 08, 2025 12:18 pmI have a TTV flywheel that I was considering using. Thom are you saying that for a streetcar you would stick with the stock flywheel because it has better inertia? It has better inertia because the bulk of the weight is further from the center, am I following that correctly?
What I meant to say in my previous post was that the stock FW would give less inertia than the TTV if either had been lightened by the same amount, but I am pretty sure they would feel very similar out of the box.
HOWEVER I must also add to my previous post that the inertia on throttle lift off can depend on the settings of the overrun fuel cut and I have been able to get a satisfying dynamic behaviour by adjusting those a little further. I think it's as good as can get now, at least matches well with how quickly gearchanges can be made with the 968 'box. This may be a detail but has always been of paramount importance to me to make for an enjoyable and dynamic driving experience at any pace, regardless of vehicle speed.
'90 944 turbo
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BasHenneman
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Okay now 3rd time trying to respond here…944m3 wrote: Tue Apr 08, 2025 12:18 pmI have a TTV flywheel that I was considering using. Thom are you saying that for a streetcar you would stick with the stock flywheel because it has better inertia? It has better inertia because the bulk of the weight is further from the center, am I following that correctly?Thom wrote: Fri Dec 20, 2024 10:34 pm -1.5 kg if I remember right, which with a KEP2 made a massive difference for me. Just wanted to somewhat warn you before you have everything buttoned up and figure out, possibly after spending further time on teething issues and on the tune, that the overall experience is eventually let down by excessive inertia in the rotating assembly. Out of the box the TTV flywheel may have the same mass as the stock flywheel but it is a rather crude design with a more or less uniform weight distribution over its radius and will cause more inertia than a stock flywheel. My machine shop had lightened both my former stock flywheel and my current TTV flywheel for me and although he got them down to the same final weight he found difficult to get inertia with the TTV flywheel down to the same level as the lightened stock flywheel, and I can feel this in the way the engine reacts to throttle inputs. I would say it's "just ok" by now.
With that said and depending on your experience and how you want your car to drive it may actually suit you fine. Here's just my real world feedback for you.
100% recommend the TTV / SPEC FW. Used stock and TTV on my 968 and the TTV was much better.
For the ECU the TTV doesnt matter for the 16v as its the same
Im sure there was a revision to the TTV flywheel a couple of years ago, I wonder if Thoms flywheel predates that. I don't have a stock turbo flywheel to compare to but mine didn't feel overly heavy compared to my smaller S2 flywheel