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Re: 3.0 16V engine mods, etc
Posted: Mon Aug 04, 2025 9:15 am
by Thom
Just got back from a 600 mile drive, 90% of which on the highway, and can confirm the initial obervations that the larger compressor provides more instant torque at throttle tip-in, which makes the car a friendlier and smoother drive under low loads/vacuum than with the previous turbo and this results in better fuel efficiency as cruising at 150kph / 95mph in 6th has returned a respectable 29.5 mpg (imperial) or 24.5 mpg (US) or 9.6L / 100km. The engine picks up in 6th down low a little better than with the previous turbo. There is just more meat everywhere down low, though fat-free meat obviously as it is still not a large NA V8. These small gains are very appreciable in real world driving conditions though.
Re: 3.0 16V engine mods, etc
Posted: Wed Aug 06, 2025 7:24 pm
by 333pg333
Sounds like a worthwhile change then Thom. Is this with the new clutch?
Re: 3.0 16V engine mods, etc
Posted: Thu Aug 07, 2025 4:18 am
by Thom
This is still with the 4 spring 930 clutch disc.
Yes, so far I think the larger turbo was a worthwhile change. Honestly on the first drive I was disappointed with the loss of "response" and thought I would move back to the previous turbo sooner than later but the more I drive it the more it grows on me and how smoother the engine runs and how some relevant figures such as EGT have evolved in the right direction now prevail over the loss of response. It just took me a little while to adjust to the larger turbo and how it performs. Even if I cannot run the engine with "high" boost yet I think it is still a very good balance between response, torque and power, although in a different way than with the previous turbo, suggesting planets can align in different manners after all!
I took another car to its periodic technical visit this morning and although it makes a comfortable 500 bhp with a very responsive and high revving NA engine, my immediate thought at the wheel after the long drive with the 944T last week was how deceivingly fast, partly due to the low-ish compression ratio, the 944T felt in comparison. Effortless is perhaps at this stage the term that defines it best.
Re: 3.0 16V engine mods, etc
Posted: Sun Sep 14, 2025 10:32 am
by Thom
Re: 3.0 16V engine mods, etc
Posted: Mon Sep 15, 2025 5:48 pm
by ROB III
Nice Office!
Kudos to the decorator.
Re: 3.0 16V engine mods, etc
Posted: Mon Sep 15, 2025 6:48 pm
by Tom
Paint work is looking good! How is the engagement on the South Bend clutch? Smooth as stock? I worry a bit about my recommendation because it looks like a more aggressive disk than the one I had.
And, at the risk of annoying you....

- Vibrant Boost Brace.jpg (7.08 KiB) Viewed 1156 times
Re: 3.0 16V engine mods, etc
Posted: Mon Sep 15, 2025 10:59 pm
by Thom
Engagement is nearly as good as stock as long it's not asked to work for too long in stop start traffic as it begins to be a little juddery when hot. What is not so good though is that the biting point is way higher on the pedal even after lowering it to the maximum possible. This is a PITA on a car where the biting point was at the same height in the 19 years I've had it and I've been struggling to adapt to it. Could the supposedly less progressive nature of the new disc give a false impression that the biting point is at a different height?
No room for one of these rods as the sleeve at the IC inlet is too short. This is the first time this happens since fitting the custom intercooler and I suspect that's because ambient damp goes through rubber on long periods of letting the car sit unused. It should be fine again after degreasing the connection.
Re: 3.0 16V engine mods, etc
Posted: Mon Oct 13, 2025 11:38 am
by Boostfeen
New Grand Prix white is looking clean let us know how she looks on first drive after put back together Thom
Re: 3.0 16V engine mods, etc
Posted: Fri Dec 12, 2025 8:04 am
by Thom
Boostfeen wrote: Mon Oct 13, 2025 11:38 am
New Grand Prix white is looking clean let us know how she looks on first drive after put back together Thom
Well, there is a picture
here, which
@Tom made me the honour of using for the latest banner - I bow to you Sir but the car is not worth it!
The car has been out only 3 times since picking it up with the fresh sills from my buddy 3 months ago, each time in poor/wet weather (to pick up stuff for other cars that have been taking way too much of my spare time lately

). The new clutch is still difficult to adjust to, very on/off, and the car has definitely lost its easy-going, drive around/shopping trolley abilities but trying to see the glass half full in that the clutch now demands a level of focus in line with the straight-line performance. Jumping back into this car after enjoying others with far less punch is always a surprise and opening the throttle to run at only atmospheric pressure whilst casually cruising in 5th brings the speed from 60 to 100 mph in the effortless and comfortable manner of a jet about to take off, suggesting the larger turbo flows just what the head needed to show its true colours even at the lightest loads, making the car not only a rear tyre executioner but the ultimate long distance cruiser. It may sound like a hyperbole but it really creates its owner weather and you better be on it when you open the tap.
Upgrading the fuel delivery is on the back burner though I may upgrade from the 044 to the new pump when I have a few days off at the end of the month, as it really is an easy job.
Thanks to all who still have an interest and sorry for not spending as much time on this car as it deserves and post interesting updates, but sorting the fuel delivery may be mostly needed for a clean glory run on the dyno and I have a feeling bottom end bits may kiss the shop floor if pushing the turbo above 26 psi where it seems to perform best.
Re: 3.0 16V engine mods, etc
Posted: Sat Dec 13, 2025 10:09 am
by ROB III
@Thom
SIR, with all the work you have done and shared with photos along with trials and tribulations, you clearly belong on the banner.
Clean, fast, well-engineered, being used as it should be without the restrictions in the US, its a great example of what the platform can become with time.
