3.0 16V engine mods, etc

[Thom]

Well yes, thanks for that - I got confused with the actual meaning of duty cycle as I had never hit the max value of 100 in the fuel table before. In the first years with this engine I spent quite some time scaling up the values in the fuel table after lowering the Master Fuel to the lowest possible value in order to maximise resolution in the fuel table which makes tuning the fueling easier. I remember lowering the Master Fuel from 8 to 5ms and that the engine would stall with 4ms or less.

Fuel pump is a Bosch 044. I don't log fuel pressure. Stock 968 camshafts.

With 1200cc injectors several basic online calculators suggest values ranging from 700 to 760 hp at the crank but with the power not being put to the ground because of a slipping clutch I cannot say that the car feels 700 hp fast. I suspect the previous turbo had already put the clutch on its last legs and the new one has just made clearer that it could not handle all the torque available on full load. Also the OS Giken LSD locks in a very smooth and progressive manner and I could not always tell for sure if it was the clutch that was slipping or the rear wheels that were lightly spinning under full load at upper rpm... until eventually getting that unmistakable strong smell of a burnt clutch with the larger turbo. At least the clutch can apparently still handle light to medium loads as I found out leaving for dead a guy in some BMW E46 who showed up in the rear view mirror whilst on the way back home... Small consolation and all that.

[TC72]

It would be worth adding a fuel pressure sensor or gauge - I bet it's dropping at the end there! Remember the flow rate of the pump drops with pressure, and at 26psi and (I assume) 43psi base pressure, you are at ~70psi total fuel pressure. On an 044, that limits fuel flow to 245lph or ~600hp worth(at the target AFR).

Making too much power is a good problem to have, but still a problem!

[Bergerac]

That's a good pickup, it would be interesting to see if that's reflected in the higher load rows in fuel table.

[333pg333]

All interesting results and reading Thom. So can we glean from this that the new turbo at the same psi is slightly laggier but with the increase in boost responds equally as quickly as the '76? And that the smaller compressor might have suffered with too much back pressure at 25psi +. Therefore a little difficult to compare Apples with Apples. Did you record a 100-200kph time with the old setup when the clutch was holding firm? Wonder what the new one will do. That car was already scary fast!

On another note, I had a clutch from South bend some years ago. I'm sure it was the same material that Tom described. I'm trying to remember what engine was on which car when I had that, but it worked fine and didn't lose much in terms of stock engagement. If you really struggle I could see if the guy down here who I got mine from is still in business. Sort of a Milledge of the clutch world lol. Mine would be too race car for street comfort but I'm sure he can dial it back a little.

[Tom]

My SB was their 'Feramic' material with their own PP. The PP was a Sachs unit that they modified by changing the fulcrum point. I was pretty stiff, but still street-able. It was stiffer than the KEP1 if memory serves. I also remember briefly mulling the need for a second 044 pump when I was approaching 500/500 on the dynojet using e85, but ultimately decided enough was enough... You might not be that far away on pump/racing gas though...?

[Thom]

Patrick, the hotside is the same as before (GT35 1.03), and that was partly the point of changing turbos : testing a new compressor with exactly the same turbine and see the difference.
Compared with the '76 the '82 is laggier in terms of boost but apparently less in terms of torque in the low and mid range (and it walks all over the '76 up top). The instant mid range kick is gone as the torque curve seems flatter and higher everywhere, again like a large NA engine. Let's put a sprinter and a rugby player side by side on the starting line of a running course. The sprinter (smaller turbo) may reach its peak speed (peak boost) more quickly but the higher drag coefficient of the rugbyman (larger turbo) means he will push more air all the way to the finish line (choking point of the head), if that makes sense. The amount of air moved during the course is far more relevant to overall performance than how quickly either runner reach their peak speed. Obviously this is with a course (or engine top end) that can flow a decent high amount of air... A large turbo like the '82 on a 8V head might be comparable to asking the rugby player to sprint over a shorter distance : the race will be over before he can get anywhere close to how much air he can push.
The '82 compressor wheel is probably a better match to the GT35 1.03 hotside than the '76, which shone on full load but could not flow as much as the larger '82 at lower loads. We could say that the fun has been replaced with more efficiency, both with their own advantages and drawbacks, but I think the larger turbo will be fun as well with a functional clutch, although in a different way.
For what the datalogging is worth the best the car did with the '76 was 6s between 100 and 200 kph but that was only once when all the stars had aligned for some reason and there was no wheel spin or clutch slippage yet, in the early days of pushing the boost to 23+psi. If this time was to be bettered that would be with a flatter torque curve that I think the '82 can provide.
Thanks for the help. I will let you know if I can't sort myself out.

I will upgrade the fuel pump together with the injectors after fixing the clutch. The DW350iL seems a straightforward replacement to the 044?

Anyway, lots of work in perspective whilst the car felt pretty solid and complete already with the smaller turbo, but as always I think it will be worth it in the... ahem... "end". Lol.

[333pg333]

My SB was their 'Feramic' material with their own PP. The PP was a Sachs unit that they modified by changing the fulcrum point. I was pretty stiff, but still street-able. It was stiffer than the KEP1 if memory serves. I also remember briefly mulling the need for a second 044 pump when I was approaching 500/500 on the dynojet using e85, but ultimately decided enough was enough... You might not be that far away on pump/racing gas though...?

We have 3x 044 pumps in our car. Quite a noisy little hive in the spare wheel well!

[333pg333]

Patrick, the hotside is the same as before (GT35 1.03), and that was partly the point of changing turbos : testing a new compressor with exactly the same turbine and see the difference.
Compared with the '76 the '82 is laggier in terms of boost but apparently less in terms of torque in the low and mid range (and it walks all over the '76 up top). The instant mid range kick is gone as the torque curve seems flatter and higher everywhere, again like a large NA engine. Let's put a sprinter and a rugby player side by side on the starting line of a running course. The sprinter (smaller turbo) may reach its peak speed (peak boost) more quickly but the higher drag coefficient of the rugbyman (larger turbo) means he will push more air all the way to the finish line (choking point of the head), if that makes sense. The amount of air moved during the course is far more relevant to overall performance than how quickly either runner reach their peak speed. Obviously this is with a course (or engine top end) that can flow a decent high amount of air... A large turbo like the '82 on a 8V head might be comparable to asking the rugby player to sprint over a shorter distance : the race will be over before he can get anywhere close to how much air he can push.
The '82 compressor wheel is probably a better match to the GT35 1.03 hotside than the '76, which shone on full load but could not flow as much as the larger '82 at lower loads. We could say that the fun has been replaced with more efficiency, both with their own advantages and drawbacks, but I think the larger turbo will be fun as well with a functional clutch, although in a different way.
For what the datalogging is worth the best the car did with the '76 was 6s between 100 and 200 kph but that was only once when all the stars had aligned for some reason and there was no wheel spin or clutch slippage yet, in the early days of pushing the boost to 23+psi. If this time was to be bettered that would be with a flatter torque curve that I think the '82 can provide.
Thanks for the help. I will let you know if I can't sort myself out.

It is only after fixing the clutch and upgrading injectors that the 044 will tell if it needs upgrading. The DW350iL seems a straightforward replacement?

Anyway, lots of work in perspective whilst the car felt pretty solid and complete already with the smaller turbo, but as always I think it will be worth it in the... ahem... "end". Lol.

When one thinks about it, just changing to a slightly larger compressor (measured in mm's and grams) makes such a difference moving a ton and a half car. Clever things these turbos. You've probably tested more than most. We thank you for your service to the greater 944 turbo community! It will be interesting to see just how different this is now once you've got the clutch sorted. Whether the extra and more linear tq will mean a faster 100-200 times. I suspect it will. Your relatively modestly sized rear wheels/tyres might holler in submission!

As for ever finishing modifying this car...I shan't hold my breath.

[Thom]

Sorry, there are some interesting comments I had not replied to.

Looks like a pretty positive result- new turbine wheels perform so well in terms of back pressure. It really makes high boost on pump fuel more practical, and engines really love it.

Well, I believe Garrett GT turbine wheels have been around since the mid 90s, so they're hardly new technology. I'd have tried a more recent G35 gladly if they were not so damn expensive and testing the GTX3582R was on the map since it came out more than 10 years ago, so when I saw an unused one for sale at a very decent price and knowing it would be a straight fit I did not think for too long... first and foremost all for testing's sake.

All interesting results and reading Thom. So can we glean from this that the new turbo at the same psi is slightly laggier but with the increase in boost responds equally as quickly as the '76? And that the smaller compressor might have suffered with too much back pressure at 25psi +.

Well no, the '82 is definitely laggier than the '76 and makes the car a less dynamic drive through the gears and twisties regardless of peak boost, though that's not an exactly fair comparison due to the slipping clutch. The '76 was a lot of fun at any boost level thanks to its quick response whilst the '82 may only be fun at higher boost levels to compensate for its slower response. EGT was reasonable with the '76 which suggests back pressure was not an issue, but the f'ing clutch did not allow me to push it to more than 30 psi though I think it would have done great. You may remember how hard it hit with 23 psi of boost, making any attempt at trying more boost somewhat redundant anyway. Depending on how traction gets with a solid clutch the more linear delivery of the '82 makes 30+psi boost pressures definitely more conceivable, at least as long as the mountain of torque does not end up breaking anything

[Tom]

What fuel are you running Thom? Hearing of 30psi makes me break out in a cold sweat...