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Thread: Sams TFSI turbo conversion (maybe!?)

  1. #21
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    Great project and development work Sam.
    Track Car: 06 Polo GTI Red Devil mkII
    Daily: 2010 VW Jetta Highline
    Gone but not forgotten: 08 Polo GTI
    ** All information I provide is probably incorrect until validated by someone else **

  2. #22
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    Thanks fellas

  3. #23
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    Ok its looking like I'll have a stock wastegate actuator on hand soon which means i'll be able to thow in something that'll keep the car running around while I remove the Turbosmart actuator that's in the car now and mod it for use on the Golf Mk6 turbo. So this is my wastegate actuator spring question:

    It looks like Golf Mk6 Gti Stg 1 and 2 tunes run up to 18-20psi. Another member on here has sent me a log of a more conservative Stg 2 tune where even its 15-16psi peak held till about 4750rpm but then trailed off to 12psi at redline. That's on 2litres. While those numbers seem pretty high for such a small turbo relative to 2 litres, I'm thinking that with only 1781cc to play with, that I'll probably have to do the same. Stock Golf 6 Gti's run about 9psi peak boost standard on what I can tell are 5psi actuator springs. For my Turbosmart IWG-75 actuator I have 5psi, 7psi and 10psi springs, meaning that I can feasibly run gate pressures of 7, 10, 12, 15 and 17psi. My
    wastegate flapper's port will stay stock diameter although it will have its entry smoothed to flow a little better, so nothing dramatic happening there.
    So what gate pressure should I run? I'm thinking 10 or 12psi.

    caveat: I am on stock rods with this motor with 300hp/300 lb ft touted as the max they'll handle. Sounds very high to me given that its less likely to burst into wheelspin than most cars since it has an LSD and runs R specs when on the track.

  4. #24
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    Some tips from my experience with stock bottom ends (not VW's). Avoid lots of boost at low rpm as it places the same combustion pressure loads on the pistons, rods and big end bearings but it lasts longer than the same boost at higher rpm. Hence more time to bend the rods, "push" through the oil film etc. It also often requires retarding the ignition to avoid detonation, which isn't good for a stock bottom end.

    My rule of thump, don't get carried away with boost under 3,000 rpm. Plus I generally run lower boost in 1st and 2nd in a FWD car, it just results in wheelspin that is very difficult to control even with an LSD. I "tune" the engine on the dyno, but I tune the "car" on the track. Often what looks OK on the rollers doesn't work so well when the racing rubber hits the road.


    Cheers
    Gary
    Polo GTi 2017, Golf Mk7 110TSI Highline, Golf Mk7.5 R, Skyline R32GTST, Stagea RS4,

  5. #25
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    Yep that was what we are most likely to do. We have the capability to do boost by gear. I haven't got that in place with the existing tune but yeah I reckon it'll be needed when the new turbo goes in.

    I think I've settled on the 10psi actuator spring. The 7psi Turbosmart spring would be a small 2psi upgrade over the stock IHI one, but we are going to be doubling the boost, so base based on that order of magnitude I think 10psi will be a good start.

  6. #26
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    I have most success (with controlling boost) when I use a wastegate spring that is not too much less than the minimum boost (in the usable rpm range). That way the boost controller doesn't have to work as hard. For example I'm running a 1 bar spring for a minimum of 1.3 bar of boost on the Skyline, on the Evo we ran a 1.25 bar spring for a minimum of 1.5 bar of boost. But they are built engines with turbos that don't really provide a lot of boost under 2,500 rpm. In your case 10 psi might be OK for up to the 3,000 rpm if that's your target.

    Cheers
    Gary
    Polo GTi 2017, Golf Mk7 110TSI Highline, Golf Mk7.5 R, Skyline R32GTST, Stagea RS4,

  7. #27
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    I had a good look at the wastegate port last night. There is a 1mm wide ridge around the entire inside circumference of the port. It looks like the cutting bit that went into the port didn't go all the way in and left a lip that you could nearly cut your finger on. With that taken out the port will flow a lot better than it first looked so hopefully yeah 10 psi will be the go.
    Thanks for that Borg Warner pdf you sent me Gary. That was a good read. It was an eye opener to see them say that at full throttle you can have 40% of gases flowing through the wastegate - I hadn't imagined it'd be that much so I'm keen to do a bit of work in that area.
    I'll forward that to my mate who's planning the engine side of his 2J build now. He's agonising over whether an internally gated efr is the way to go with 550 whp or if he should start from scratch with an external gate so that'll be helpful. thx

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