Sam's build thread

[Sirocco20348]

Australian delivered mk4 golfs (AGU) are all large port. There are other large port 1.8t motors aswell - AEB...

1.8T 20V Engine codes FAQ | Club GTI

[sambb]

you're joking. Hmm interweb bum steer then. But all naturally aspirated engines are large port yeah? Whats the going rate for a large port head?

[HaydEn]

you're joking. Hmm interweb bum steer then. But all naturally aspirated engines are large port yeah? Whats the going rate for a large port head?

$100 or so. See them cheap all the time, most of the time they have a bottom end attached to them for that price though.


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[sambb]

ok another thing then... I read this and that about using NA cams. They seem to have more or less the same minimal overlap but a lot more lift. Some say do the inlet and then the more mental the engine gets go to the NA exhaust cam as well, but then other peoples put up dyno sheets where they make zero gain and loose bottom end. Any experience with NA cams from the Mk4 guys?

[Sydneykid]

My view is that turbo charged Golf's especially from MK5 onwards (and Polo's) have twin goals, performance and fuel economy (which is also heavily emissions related). Hence the small ports which, together with turbo sizing, promotes low rpm torque (really low rpm), such as making boost at just above idle. This gives the instant shove in the back (performance) plus negates the need for higher rpm (economy & emissions). Conversely the N/A engines need the larger ports to make decent performance (less torque, more horsepower), but in doing so they sacrifice the really low rpm torque, need higher rpm to make horsepower and hence result in increased fuel use and emissions. That's why we have 1.4 litre turbo engines making the torque of a 2.5 litre N/A engine with the emissions and fuel usage of a 1.4 litre engine.

IMHO the smaller ports (in the later turbocharged engines) has far more to do with fuel economy and emissions than some small low rpm performance gain. Since, in competition, we only care about performance, making more horsepower at lower boost levels is the target.

On camshafts, it's all about matching, for example if you have a camshaft set up that works really well from say 4,500 rpm to 8,000 rpm then you need to size the turbo to match that. It's no good trying to match a 2,500 rpm to 5,500 rpm turbo to those cams. Playing around with the cam timing can make a small difference, for example (in Evo's and Skylines) advancing the inlet cam 4 degrees and retarding the exhaust cam 2 degrees means making the same boost 500 rpm earlier.

There is no real substitute for matching the turbo sizing with the rest of the engine hardware, so have your targets firmly in mind before you start. If you want an engine that makes good boost (torque), say, at 2,000 rpm then small ports and turbo cams are the go. If your aim is good horsepower at say 7,000 rpm, then big ports and N/A cams are more likely to help with that.


The Garret GT2560 is the standard turbo on the S15 200SX, they are OK for around 310 bhp at about 1.2 bar. A common upgrade on 180SX/S13 with the CA18 (1.8 litre), they are very responsive but run out of airflow (efficiency) at around 6,250 rpm. Personally, for a competition biased car with rods and pistons, I'd be looking more in the BW 6258 sizing and running it at around 1.5 bar for 360 bhp. Still well in their 76% efficiency range at 145,000 shaft rpm and they can run at 75% all the way down to 0.7 bar for around 220 bhp at 95,000 rpm. They also can handle 2.2 bar at 75% (155,000 rpm) for the same horsepower (~360), OK for an engine with lots of restrictions, so they are very flexible. Handy if you want to use the same turbo on an existing (unopened) engine while you build a decent one.


Cheers
Gary

[sambb]

hmm I need to think very much on the engine path.

In other news I found this vid of a teardown of the brand new 2020 Supra/BMW B58 engine:
https://www.youtube.com/watch?v=MckxlP60cnY

[sambb]

Ok these are my options
- throw my 90,000km motor in off the stand as is. It didnt use a drop, had great compression and only ever really a stage 1 tune which didnt pull a dot of timing. Bolt on the Golf Mk6 turbo and new gearbox inc plate diff and away I go. Aim long term to be building the engine that comes out at my leisure and properly.
OR
same motor but with some hardware I may be able to get my hands on for a very good price. A set of 20mm wrist pin x beam forged rifle drilled rods and audi S3 pistons. It'd literally just be a re-rod job though. I'd check the mains to make sure there's no nastiness and then bolt them back up. Then if I can find one, a large port head (may as well if the small port is coming off) or if I'm very nice to a mate get him to take the small port out to some compromise degree towards being a biggish small port. I think the S3 pistons are 9:1 vs 9.5:1 for the Polo which hopefully wouldnt be a detriment when the turbo I'm putting on is a low down breather anyway. Then the engine that comes out can just be for spares.
thinking thinking....

[Sirocco20348]

Yeh i watched that engine tear down aswell, the BMW engine is absolutely amazing.

Plastic intake manifold with integrated intercooler.
Exhaust manifold integrated into the block.
Timing chain at rear of engine.

Im also amazed that the supra is similar length as a GT86, but achieves a lower center of gravity than a gt86 even with the inline 6.

[sambb]

I couldn't work out if it also had an air to air intercooler or if those cores that came out of the front were just radiator/air con and water - air IC heat exchanger. Probably not as stacking 4 cores (another for air to air) would get a bit fat unless it runs an air to air core ahead of the front wheels.
Its weird enough on the new TFSI fours seeing the turbo just bolt direct to the head but it looks downright weird with the turbo having two short runners going onto the head of a 6cyl.
Knowing what the Japanese aftermarket will be like for this engine, the BMW guys will be cheering knowing that they'll actually be able to get parts out of Japan rather than TUV'd german EU priced stuff only.
I saw a vid recently where they put a stock Supra on a wheel dyno and it read way over the stated hp if you back calculated it to crank hp. English dyno too not USA.
I saw a vid where the designers were explaining how they designed the car knowing full well what the aftermarket would do. Eg the faux air ducts are actual air ducts that tuners can open up when additional cooling is needed. It has reinforced points for additional strut/body bracing that they didn't utilize from factory, the rear boot lid has reinforced steel so that it can support functional downforce producing wings etc etc.

[sambb]

Its a bl**dy big difference. But yet the best bit of info I've read re the small vs large ports effect on low down torque argument, was where someone quoted the small port vs large port factory torque/rpm figures on 150hp engines with the same K03 turbos. The torque peak/rpm was identical irrespective of port size. Like the person who quoted the factory details suggested, that's got to mean that the turbo will be the bigger determinant of spool/torque rpm than port size alone yet obviously the bigger ports will benefit you further up the rev range.

Just thinking , my IC pipework is 2in diameter. That's a c.s.a of 3.142 sq in. Just one large port has a c.s.a of 2.24 sq in. Assuming I was to retain 2in pipework there's not some rule of thumb that dictates a port sizes can be a max % of pipework size or anything is there? I mean one large port will be over 70% the csa of my IC pipework. I know that dynamically the whole process is about volumes being pushed through but is that where I might run into trouble and actually loose bottom end compared to a small port if I'm not over 300hp?

[Sirocco20348]

Its a bl**dy big difference. But yet the best bit of info I've read re the small vs large ports effect on low down torque argument, was where someone quoted the small port vs large port factory torque/rpm figures on 150hp engines with the same K03 turbos. The torque peak/rpm was identical irrespective of port size. Like the person who quoted the factory details suggested, that's got to mean that the turbo will be the bigger determinant of spool/torque rpm than port size alone yet obviously the bigger ports will benefit you further up the rev range.

Just thinking , my IC pipework is 2in diameter. That's a c.s.a of 3.142 sq in. Just one large port has a c.s.a of 2.24 sq in. Assuming I was to retain 2in pipework there's not some rule of thumb that dictates a port sizes can be a max % of pipework size or anything is there? I mean one large port will be over 70% the csa of my IC pipework. I know that dynamically the whole process is about volumes being pushed through but is that where I might run into trouble and actually loose bottom end compared to a small port if I'm not over 300hp?

Not sure about the math, but pretty much the unwritten rule for IC piping in the 1.8t is 2.5". The majority of the stock piping is larger than 2".

Well known tuning company in the UK mk4 scene, RTECH, have proven time after time that 2.5" or larger gives the best results, even on the smaller K03/k03s turbos.

They seem to get ridiculous results, 265hp K03s figures, and are all about 'flow', the bigger and straighter the pipework the better.

I was worried about response with the larger 2.5" IC pipework and the 3" downpipe with the k03s but after getting it I have no regrets. The turbo has no problems what so ever.

[Sydneykid]

Ditto, I have found 2.5" is the go for anything over ~250 bhp. I'm still using 2.5" into the intercooler on the Skyline for ~700 bhp as that matches the compressor outlet, then it has 3" from the intercooler to the plenum. As long as the bends are constant diameter I have found zero difference in the air flow (ie; no measurable back pressure) at up to 60 lbs per minute.

FWIW the current M3/M4 BMW's with the same engine have air to water intercoolers. Which if I had my time over I would do on the Skyline.


Cheers
Gary

[sambb]

hmmm ok. another reason to ditch the SEAT Sport IC then. Its in's and outs are 51mm I.D which the pipework that came with it matches. I remember (before I removed it) that the plastic pipe that runs down between the crank pulley and chassis rail constricted down to less than 50mm.
Yeah I did find the notion that a 3in dump would compromise spool up, to be absolute rubbish with the main difficulty turning out how to keep traction when it came on so hard/early. I wont be shy at all at going to 2.5in on the IC pipework then.
thanks guys!!

[metalhead]

My understanding is that bigger dump pipe basically always results in better spool. Pressure difference across the exhaust side of the turbo, you really can't go too big on dump pipe on a turbo car in my (admittedly non-expert) opinion.

[metalhead]

You all set for the weekend Sam?