944 Turbo S Engine Rebuild Thread
- Thread starter Eldavo
- Start date
Another decent run out this morning and wowsers- what a difference in the car!
I reviewed the VEMS log files to try and get the boost dialled in, it uses a PID closed loop system but there is a boost lookup table as well that was unpopulated. I went through last week’s run to note down the solenoid duty cycle at given rpm points and boost pressures and then populated the table with these figures. I then extrapolated the data into any blank boxes to get a good baseline for the PID to work on top of. Everything is set to 22psi but I scaled that back to 18psi and set my Overboost fuel cut at 19psi.
The results were epic, seeing full 18psi by 3k rpm and it holding it there as long as I dared keep my foot in for. No Overboost issues at all, just consistent quick spool and plenty of "area under the curve” - went back into the logs and tweaked a couple of numbers that I’d extrapolated with the actual data and I was happy that I was there or thereabouts even to start with.
Also chased down an annoying rattle just below 2krpm that seemed to be coming from under the dash but ended up being the horn pad on my steering wheel not being clipped in all the way!
Here‘s the table I ended up with - YMMV as they Yanks say!
I reviewed the VEMS log files to try and get the boost dialled in, it uses a PID closed loop system but there is a boost lookup table as well that was unpopulated. I went through last week’s run to note down the solenoid duty cycle at given rpm points and boost pressures and then populated the table with these figures. I then extrapolated the data into any blank boxes to get a good baseline for the PID to work on top of. Everything is set to 22psi but I scaled that back to 18psi and set my Overboost fuel cut at 19psi.
The results were epic, seeing full 18psi by 3k rpm and it holding it there as long as I dared keep my foot in for. No Overboost issues at all, just consistent quick spool and plenty of "area under the curve” - went back into the logs and tweaked a couple of numbers that I’d extrapolated with the actual data and I was happy that I was there or thereabouts even to start with.
Also chased down an annoying rattle just below 2krpm that seemed to be coming from under the dash but ended up being the horn pad on my steering wheel not being clipped in all the way!
Here‘s the table I ended up with - YMMV as they Yanks say!
Dan944t
New member
excellent stuff mate! well chuffed for ya, looks like all is going really well[
]
my top half is still off the engine but ready to put back in now,...but i did something really bad ,..i took out the kkk26 and i have now given myself the massive task of building a twin scroll exhuast system and grafting on a Holset hx35 turbo on her [8|] wish me luck! i’m gonna bees it, there’s not a lot of room for it so a lot of modification needed to make this happen.
well chuffed for you mate, i long for that feeli my of driving mine down the road again miss it like mad, been nearly 3 years now i think?
atb
Daniel
]my top half is still off the engine but ready to put back in now,...but i did something really bad ,..i took out the kkk26 and i have now given myself the massive task of building a twin scroll exhuast system and grafting on a Holset hx35 turbo on her [8|] wish me luck! i’m gonna bees it, there’s not a lot of room for it so a lot of modification needed to make this happen.
well chuffed for you mate, i long for that feeli my of driving mine down the road again miss it like mad, been nearly 3 years now i think?
atb
Daniel
Thanks Tony, I won’t be making the 944 get together at Goodwood though, it’s a little far to travel to be standing in a car park. Hoping to make some track days this year though.
There have been developments with regards to the previous engine build issues I encountered but it‘s a slow and ongoing process.
There have been developments with regards to the previous engine build issues I encountered but it‘s a slow and ongoing process.
Spot the difference to the earlier post.
Well done, the suspension has been raised 15mm - very observant of you []
Took the usual route for a Sunday morning coffee and the "running in” 500 miles has now been ticked off. I kept it under 19psi of boost, 5k rpm and 120 . . . erm, km/h [:-]
Still pulls like a train, still makes lots of nice noises but no longer bottoms out or scrapes and I’ve tweaked the KW CS settings a tad too. Going for an alignment this week to dial a bit of camber out and make it overall a bit less fighty as it’s running Turbo Cup alignment settings and it’s a bit too pointy for more road usage.
Well done, the suspension has been raised 15mm - very observant of you [
]Took the usual route for a Sunday morning coffee and the "running in” 500 miles has now been ticked off. I kept it under 19psi of boost, 5k rpm and 120 . . . erm, km/h [:-]
Still pulls like a train, still makes lots of nice noises but no longer bottoms out or scrapes and I’ve tweaked the KW CS settings a tad too. Going for an alignment this week to dial a bit of camber out and make it overall a bit less fighty as it’s running Turbo Cup alignment settings and it’s a bit too pointy for more road usage.
Now it’s no longer scraping I have decided to tempt fate by fitting an ankle chopper splitter. Hopefully it won’t rip my bumper off completely.
Given the scrapes on the bottom of the previous splitter this may not be staying on permanently- we’ll see.
Also fitted some 18” wheels with normal road tyres for a change and despite the cries of heresy nobody has died and they’re still attached to the car!
Given the scrapes on the bottom of the previous splitter this may not be staying on permanently- we’ll see.
Also fitted some 18” wheels with normal road tyres for a change and despite the cries of heresy nobody has died and they’re still attached to the car!
924Srr27l
New member
blade7 said:Eldavo said:
[
Sounds familar...........Skitty / fighty etc..?
"Going for an alignment this week" to dial a bit of camber out and make it overall a bit less fighty as it’s running Turbo Cup alignment settings and it’s a bit too pointy for more road usage.
18's ! ? F1 are going for those next year, it's causing allsorts of issues! several seconds slower than the current 13's,
It's a change that's been done "all for Show" and no go! ... but they will sort it eventually by changing all the suspension rates and geo to cope with the extra weight and lower profile tyre sidewal.
R
Nice try WodgePot, it was like that before I fitted the wheels as the alignment settings are the French Cup Car race settings.
I don’t care about F1, nor do I see the relevance between what F1 are doing and me - I fitted them because I like them, simples! I’ve got different compound track tyres on two sets of 17s and a set of 16” CS wheels too with A048s on IIRC - plenty of options to ply with and not had to drill superfluous holes in any of them.
I don’t care about F1, nor do I see the relevance between what F1 are doing and me - I fitted them because I like them, simples! I’ve got different compound track tyres on two sets of 17s and a set of 16” CS wheels too with A048s on IIRC - plenty of options to ply with and not had to drill superfluous holes in any of them.
924Srr27l
New member
Eldavo said:
Well that is just "class" ! [
] (Don't like F1 but like French cup Racing!)Of course your and my car is nothing like a current F1 car! (Well my Carbon chassis is currenty being built!
)....but the relevance Mr. my car has a Geometry set up the same as a 944 French Cup "RACE car" !! maybe that's why it's skittish ? LHD settings! ?
Why oh why I ask?? Funny how this doesn't work on public roads no ? all to do with compliance , the lack of it, or too much of it, and / or incorrect tyre contact patches and more..
Which is why there is a LOT of relevance to the fastest catorgary circuit racers (F1) as they (And you) need to make some changes to make the car better right?
Good that you've got plenty of options, you can swap them about for the "looksey" bit and change and gain road and track performances accordingly...
Getting back to Speed, Imagine how much more you could play with your pressure settings (Not just tyres) if your car also was 250kg lighter...back to the Drill and holes bit ! [
]R
Blade - Boost control was relatively straightforward to set up but did need a bit of playing and logging as the PID wasn’t quite as good as I expected. Mind you I never found the similar "fuzzy logic” on the Apexi AVC-R that reliable either. The advantage of data logging and then filling the lookup table is repeatability - if you need any pointers on setting yours up just ask.
Waylander - thanks, I think so too.
Roger - Thank you for throwing your fingers at the keyboard to elucidate me with your opinion. I genuinely don’t care what you think, but I do appreciate the length and barely contained angst of your posts. PMSL as the kids say, like shooting fish in a barrel getting a bite from you.
Waylander - thanks, I think so too.
Roger - Thank you for throwing your fingers at the keyboard to elucidate me with your opinion. I genuinely don’t care what you think, but I do appreciate the length and barely contained angst of your posts. PMSL as the kids say, like shooting fish in a barrel getting a bite from you.
Eldavo said:
I'm not familiar with the VEMS PID system but will say that the APEXI does it's job well if setup correctly. The thing is, most, including myself prefer a high duty cycle to dial out lag, however, the higher the duty cycle the higher the boost spikes to expect and thus less control of boost. I get around this with a seperate stepper boost gauge with an audible warning which I set at 1 BAR to give me an idea of where I am in the boost range without needing to take my eye off the road. I also have control of the ECU boost override which I currently have set at 1.5 BAR. The time span between hitting 1 and 1.5 BAR is next to nothing so the audible wsrning is used to think about backing off WOT, a little...
Like all things with modified engines, it's the overall package which makes a good drive, individual components need to match up well with eachother to run reliably.
Pete
I should’ve been clearer - the AVC-R is great but it was the "Fuzzy Logic” aspect that I wasn’t that impressed with. Once I’d set the duty cycle per rpm it was fine. Quite a bit of trial and error though to get there - and as you’ve experienced with your boost spikes it’s only a single DC setting per rpm column.
Where VEMS shines for boost control is the logging facility and also the resolution per rpm column. Rather than just, (e.g.) 52% at 3500rpm for 18psi with the Apexi you can set the individual DC for (e.g) 6,8,10,12,14,16 and 18psi at 3500rpm from the logs. So no boost spikes as each individual cell is the perfect DC for that rpm and boost level.
The best thing about boost control being undertaken by the ECU is that the Overboost protection is still enabled too.
Where VEMS shines for boost control is the logging facility and also the resolution per rpm column. Rather than just, (e.g.) 52% at 3500rpm for 18psi with the Apexi you can set the individual DC for (e.g) 6,8,10,12,14,16 and 18psi at 3500rpm from the logs. So no boost spikes as each individual cell is the perfect DC for that rpm and boost level.
The best thing about boost control being undertaken by the ECU is that the Overboost protection is still enabled too.
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