944 Turbo S Engine Rebuild Thread
- Thread starter Eldavo
- Start date
TTM said:
Yes actually - went down to the PCGB event at The Motorist on Sunday in it, bit of a pig to drive, especially at low speeds/pulling away. Wouldn’t Rev out past 4K rpm when on boost either - get like the spark was being blown out.
But a great run down nonetheless and lots of opportunity to talk to people about the car and about their 944s.
First run of the day was spiky as hell - all over the place and managed 228bhp. Was fluttering under boost and misfiring under load.
Changed to a colder range plug, reduced the plug gap slightly and also the dwell times for the coil pack weren’t right. With this resolved it ran like a champ all day - for 8 hours in 38°C heat in the dyno cell!
By lunchtime we were consistently seeing 355-ish at about 13/14psi boost and then worked on the low speed driveability and load figure.
Changed to a colder range plug, reduced the plug gap slightly and also the dwell times for the coil pack weren’t right. With this resolved it ran like a champ all day - for 8 hours in 38°C heat in the dyno cell!
By lunchtime we were consistently seeing 355-ish at about 13/14psi boost and then worked on the low speed driveability and load figure.
Then we worked up in 1 psi increments mapping ignition and rudimentary boost table as we got higher - still lots of work for me to do on the boost table with some logging required as we simply ran out of time.
Called it a day at 18psi and 404.8bhp which given the ambient temps we were happy with for now. Plan is to run it and enjoy it then if I want I can head back when it’s cooler and push it further.
I was a smidge disappointed with the final headline figure but the huge positives were that numerous back to back power runs never saw inlet temps above high 40s/low 50s (within 15° of ambient) and the coolant temps stayed in the double digits as well at all times.
Then I drove home in rush hour, it sounded great and was responsive and smooth. Until a lovely country A-road opened up in front of me and I squeezed the throttle before loudly proclaiming F*** ME! It’s a rocketship! Completely different animal to my previous engine (it’s laggy AF at the moment until I sort the boost table out) but it just revs and revs and surges to the redline whereas my old engine was a gob of low/mid range torque and had shot it’s load where this one is screaming forwards. I floored it at 50mph joining the motorway and promptly lit the rear tyres up in a way that sounds cool telling people now but took me by surprise and was a buttock clencher for sure!
Will I tweak it to more power? Probably. Would that make it undriveable on anything other than a track? Probably.
Very happy with it and I feel like I’m operating well within the parameters (boost and ignition timing) of the engine.
Called it a day at 18psi and 404.8bhp which given the ambient temps we were happy with for now. Plan is to run it and enjoy it then if I want I can head back when it’s cooler and push it further.
I was a smidge disappointed with the final headline figure but the huge positives were that numerous back to back power runs never saw inlet temps above high 40s/low 50s (within 15° of ambient) and the coolant temps stayed in the double digits as well at all times.
Then I drove home in rush hour, it sounded great and was responsive and smooth. Until a lovely country A-road opened up in front of me and I squeezed the throttle before loudly proclaiming F*** ME! It’s a rocketship! Completely different animal to my previous engine (it’s laggy AF at the moment until I sort the boost table out) but it just revs and revs and surges to the redline whereas my old engine was a gob of low/mid range torque and had shot it’s load where this one is screaming forwards. I floored it at 50mph joining the motorway and promptly lit the rear tyres up in a way that sounds cool telling people now but took me by surprise and was a buttock clencher for sure!
Will I tweak it to more power? Probably. Would that make it undriveable on anything other than a track? Probably.
Very happy with it and I feel like I’m operating well within the parameters (boost and ignition timing) of the engine.
TTM
Active member
Nice results. Your efforts are paying off and I bet it is a lot nicer to drive with a properly sporty engine delivery than it ever was with the 8V engine, on par with the sporty nature of the chassis.
In view of the figures achieved :
- what injector size are you using and what duty cycle are you seeing at peak power rpm?
- what sort of air filter (type and size) are you using and is the crankcase venting to atmosphere or back to the turbo inlet like original?
- for a given boost target, are the figures in your duty cycle boost table all the same between say 4000 rpm and peak rpm or do you need to increase them to hold onto your boost target?
- do you have a compressor map for your turbo?
- what intercooler and piping size are you using?
In view of the figures achieved :
- what injector size are you using and what duty cycle are you seeing at peak power rpm?
- what sort of air filter (type and size) are you using and is the crankcase venting to atmosphere or back to the turbo inlet like original?
- for a given boost target, are the figures in your duty cycle boost table all the same between say 4000 rpm and peak rpm or do you need to increase them to hold onto your boost target?
- do you have a compressor map for your turbo?
- what intercooler and piping size are you using?
TTM said:
Injectors are Bosch 960cc units - not checked the duty cycle on the logs but satisfied they’re big enough.
Air Filter is a K&N in the front passenger wing, again a big boy sized for 650bhp IIRC - crankcase vent goes from top of AOS, through a Mishimoto catch can to turbo inlet like the original.
I’ve been out playing and logging runs this weekend - peak boost was 4800rpm on the day, now hitting it at 3650rpm so a big improvement in driveability. DC figures increase slightly to hold target but between the lookup table and the PID on top, boost doesn’t tail off until I run out of balls and lift.
Not sure on the compressor map, it’s the factory HX35 compressor AFAIK.
Intercooler is a "Stage 1" factory job with the modified end tanks. Pre intercooler pipework is 2.5” and post is 3” (I think). However, repeated back to back full bore dunno runs in 38 degree heat didn’t see IATs rising significantly higher - 15 degrees over ambient tops.
Now I’ve managed to get some more hard miles under my belt I completely agree with you - it’s the engine the chassis deserves. My only struggle is finding enough room to keep my foot in long enough to rev it out in a gear that won’t cause a cloud of tyresmoke. The top of 3rd now sees me near enough at 100mph but more importantly I don’t feel like I’m stressing the engine too badly which is where I want to be for longevity.
TTM
Active member
Peak injector DC would be interesting to know to put in context with the peak power your reached on the rolling road.
FWIW I was running a too small air filter until recently and noticed that the turbo had so much headroom with the 16V head that it was sucking air hard from anywhere it could, namely picking up oil from the crankcase through breather hoses and filling up the catch can which was full of engine oil. There was a small puddle of oil at the bottom of the previous intercooler. In addition to installing a larger air filter along with the custom intercooler I have also deleted the connection between the catch can outlet and the turbo inlet, to make sure no oil vapour was going to make its way into the inlet loop, and I do not think that providing vacuum to the crankcase is needed on a fresh engine with supposedly minimum blow-by. After a few hard runs now you may want to check if your catch can is also filled with oil, even if your air filter seemed large enough right from the start.
I would guess that the std intercooler is the bottleneck in your set up and may seriously hinder performance, explaining why you did not make even more power, and again how much oil in the catch can should give a clue or two of how the components of the inlet loop balance eachother in terms of flow... Using oil quantity in the catch can to guesstimate flow, how about that for an exotic measuring tool? [
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FWIW I was running a too small air filter until recently and noticed that the turbo had so much headroom with the 16V head that it was sucking air hard from anywhere it could, namely picking up oil from the crankcase through breather hoses and filling up the catch can which was full of engine oil. There was a small puddle of oil at the bottom of the previous intercooler. In addition to installing a larger air filter along with the custom intercooler I have also deleted the connection between the catch can outlet and the turbo inlet, to make sure no oil vapour was going to make its way into the inlet loop, and I do not think that providing vacuum to the crankcase is needed on a fresh engine with supposedly minimum blow-by. After a few hard runs now you may want to check if your catch can is also filled with oil, even if your air filter seemed large enough right from the start.
I would guess that the std intercooler is the bottleneck in your set up and may seriously hinder performance, explaining why you did not make even more power, and again how much oil in the catch can should give a clue or two of how the components of the inlet loop balance eachother in terms of flow... Using oil quantity in the catch can to guesstimate flow, how about that for an exotic measuring tool? [
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The absolute maximum pulse width I’ve seen across a dozen logged runs is 15.4mS at 6490 rpm which gives a duty cycle of 83.29%. For the majority of time under full boost, duty cycle sits between 68% and 74%.
Well after 300 road miles and a hard day on the dyno, this was the contents of my catch can:
Well after 300 road miles and a hard day on the dyno, this was the contents of my catch can:
TTM
Active member
~80% DC with 960 cc/min injectors seem high-ish for ~400 crank hp but not wildly out of range either.
That is very limited content in your catch can and that is good. We can now ask ourselves if every component indeed balance each other perfectly but I can't help thinking that the std intercooler may be the bottleneck in your set up.
So many variables anyway, like compression ratio and cam timing that I did not ask about... If it feels good just enjoy it and congrats on a job well done!
That is very limited content in your catch can and that is good. We can now ask ourselves if every component indeed balance each other perfectly but I can't help thinking that the std intercooler may be the bottleneck in your set up.
So many variables anyway, like compression ratio and cam timing that I did not ask about... If it feels good just enjoy it and congrats on a job well done!
scam75 said:Super progress Dave, you must be chuffed! Maybe we can think about fuel lines for my poor little 8 valve soon.............we won't be having a race!
Stuart
Aye, I’ll put together a list at some point.
Dropped it off at the garage yesterday as the aircon needs oil/gas and I’ve finally tracked this persistent oil leak down. I’ve also determined that I can’t be bothered fixing it spannering away on my back under my QuickJacks so taking a day off to go work in the Indy’s next week and sort it there with their transaxle specialist, his ramp, and tools - that way when I’ve had enough I can make the brews instead.
Sorted - When I’d resealed the front lower balance shaft housing in-situ I had torn the onion seal gasket on the front of the shaft. Might not seem much but +5 bar of pressure meant it was leaking out of the side and running down the back of the housing. £1 fix - although changing the other two seals (£25) at the same time in case they’ve been damaged with riving it about.
Dan944t said:
I spoke far too soon.
Put it back together, still leaking.
Changed the oil filter console gasket again in case I'd screwed it up, still leaking.
I was then away with work so missed a day or so of swearing and head scratching.
Turns out its the freeze plug on the front of the block behind the water pump that's not sealing 100%. I must admit that I would probably have never tracked it down to there hunched under my QuickJack ramps. So a £3 part that will be here this week from Germany followed by £00000000's in labour - all of which will be promptly forgotten when I take it out for a good thrashing without leaving any drips!
Dan944t
New member
Eldavo said:
bumma , but if you’ve found the source then great! not sure what the freeze plug is though? can’t picture it ,… will have to try look that up
bloody shame about the labour mate but believe me when i say i’ve thrown away double figures in the past which is why i do all my own stuff now ,…had a 944 since age 17 so had a costly life with so called specialists that have done more damage than good
hope all goes to plan mate [
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