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Thread: Sam's build thread

  1. #1811
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    Quote Originally Posted by sambb View Post
    Ok. Has anyone ever gone to that extreme in IPRA or aside from budget constraints is it more a case of not wanting to be that guy that's so far outside of the spirit of the rules?
    Simon Philips from Vic has Datto 1200 Coupe turbo for U2L, it uses highly modified A Series engine, Jordan drove it at the 2018 Tailem Bend Nationals. It's power to weight is pretty effective being a light chassis but the rpm limit of the pushrod valve train is a bit limiting. When it was N/A he dabbled with a Honda CB 1000/1100/1300 cylinder head, which would fix the valve train issues and let it rev to what it could do. It's big advantage over the N/A U2L is of course torque, at 21 psi it would have ~50% more torque than the best N/A engine.

    A couple of guys have had a go at turbo Mk1 Suzuki Swifts (they are pre 1986), just destroke them to 1200. But getting a transaxle in them to handle the torque is not easy. Plus cooling system, driveshafts, uprights, etc makes it an expensive exercise, with pretty much everything being bespoke. Compared to the off shelf gear for Hondas, Nissans, Toyotas etc. Someone with the time and budget will do it eventually, but it will require patience and lots of engineering effort.

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

  2. #1812
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    yeah ok. sounds like a mega undertaking to motorcyce head a car block. I know that the same capacity reduction thing has been done with 1.8 blocks with my engines head to get it down to 1200cc to fit into the under 2 L class. No idea if they sleeve them too but they'd have to be destroking which would need a whole new crank yeah. Its already well undersquare so they'd have to do it that way to get it down to 1.2 surely.

  3. #1813
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    Gary, wondering if I could pic your brain RE inlet manifold design. For now I'm pretty much stuck with the single throttle system as my tuning happens via the stock ECU so I think a quad throttle arrangement is a way off.
    The large port AGU inlet manifold that I have for when I do the rebuild is an ugly work of fart - huge 'dents' in it to accommodate the alternator and dipstick and a weird throttle body angle that points the plate at cyl 1 and runs the air along the roof of the plenum which looks to be just a packaging compromise rather than a design aim.
    So say I was to cut clean off and leave the runners onto their base plate, I was looking to do a barrel plenum welded onto that. sort of like the pic below:
    Sam's build thread-hand-built-sheet-metal-intake-manifold-21-jpg
    That constrains me to the same runner length but should result in a better throttle body angle and uniform plenum - I hope. I'm thinking it'd be best to retain also the length from runner flange at the head to back wall of the factory plenum in case helmhotz tuning was something they'd put a bit of effort into. But I can adjust total plenum volume this way. Ive seen it written that plenum volume should be 80% of the swept volume of the engine which in my car would be 80% of 1.8L = 1.4L. Does that hold true for forced induction cars?
    Also I remember you saying that a smaller plenum boosts response which is a biggn' for me. At the time you were talking about quad throttles though so I was wondering if that also holds true for single throttle bodies? ie would I aim to go no more than 1.4L plenum and then offset down from there to get a more responsive setup.
    would be stock throttle body, and as you know a golf 6 gti turbo with breathing mods + tune.

    Other option would be to also just cut off the smaller Polo plenum and weld that to the large port runners, as the polo mani has a direct side feed throttle body position and a less curvaceous dented plenum simply because it is smaller.



    any help massively appreciated. My back has given out so I need some bench work to go on with at the moment.

    thx

  4. #1814
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    The inlet plenums that have worked best for me taper towards the last cylinder (eg; Pulsar GTiR), this evens out the airflow so the last cylinder doesn't get the most air.

    Sam's build thread-pic5-jpg

    Even then, when we are tuning we find we need to add a bit more fuel to the last cylinder/s (particularly on an inline 6) as they still get a bit more air than the earlier cylinders.

    The total amount of air between the inlet valves (IV) and the throttle body (TB) is what affects the instantaneous throttle response. Obviously when we close the throttle we get a partial vacuum behind it which has to be filled when the throttle is opened. That's why the really responsive turbo cars run ITB's (much smaller distance between the TB and the IV).

    The overall objective is to keep the volume between the single TB and the IV's as small as possible but not so small as it invokes turbulence in the inlet port. I would treat the 80% (of engine capacity) rule of thumb as the maximum, that's from TB to IV's, not just the plenum itself. Making the inlet runners a little longer and the plenum a little smaller will help in reducing the port turbulence.

    Then you have to fit it all into the available space, which generally compromises the "ideal" design. But who cares, just add 0.1 psi of extra boost to compensate.

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

  5. #1815
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    That's unreal info Gary. I'll start filling my 3 different 1.8T 20V manis with water to see where they all sit relative to one another and build a plan.
    I'll also let my 2JZ mate know. He's bent on a plazmaman mani but I'm not sure if they have more of a drag strip motivation to their volumes rather than hillclimb/circuit.

    thanks

  6. #1816
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    Partner & I wanted to pick up some stuff at the blue+yellow shop today but got there and found the carpark just about full so just turned around and went back home. About an hour round trip, mostly in slow but moving traffic. It's been cool and rainy here and to stop the windscreen fogging up I turned the AC on after a while. Then noticed that coolant temps were heading back downwards, to about halfway between cold and 90C. Anyone else noticed this? Coolant level seems fine. Turned the AC off and it went back up to normal reasonably quickly.

    I guess it decided to turn the rad fan on because it would pull air through the AC heat exchanger? Sam I noticed you mention a few times here the coolant temp gauge showing a heavily damped version of reality; did you notice any change in behaviour after you ripped your AC out?

  7. #1817
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    your temps would have come down because when the AC compressor kicks on, both sets of radiator fans are activated. More airflow for the condenser also equals more air for the radiator inadvertently even if it doesn't really require it (ie requested by its own coolant temp sensor), so your coolant temp drops. Should be normal.
    Yeah the stock water temp gauge is super damped. Frm watching temps real time direct from the sensor its apparent that anything from 75 or so degrees up to nearly a hundred all show as one happy position on the car.
    Having the AC gear out hasn't really affected street temps but I think it does cool more efficiently on the track now - less pre radiator obstruction. I broke into the high speed relay in the radiator fan control module and wired it to a by pass switch in the cabin so that I can run all fans continuously manually to keep the car coolant temps under control on the line at hillclimbs or to start the cool down asap once the red flag gets waived on a track day session, just to be kind to the car.

  8. #1818
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    Decided it was time to finally add an oil pressure gauge. I wanted something that has minimum pressure presets that trigger a loud audible alarm and flashing face in case the pressure nose dives on the track. I also have a sneaking suspicion that the engine is dying a slow death and I wanted to get a read on that before any funds go its way.
    The stock oil pressure switch isnt good enough to be relied upon. You can actually unplug it whilst running and nothing will show and it wont be until your next start up that it'll flash and in the heat of the moment you'd never notice it on the track anyway.

    Sam's build thread-img_0590-jpgSam's build thread-img_0593-jpgSam's build thread-img_0600-jpgSam's build thread-img_0601-jpgSam's build thread-img_0599-jpgSam's build thread-img_0603-jpg

    So the pressure sender mount I used was a tee with male and female M10x1.0 threads either end to allow the stock pressure switch to be relocated to the end of the tee, and then with 1/8th NPT ports. Turned out to the right way to go as I now have a spare 1/8th NPT port and the stock pressure switch fit neatly on the end without fouling anything.
    So all works fine. White daytime lighting and amber night time and flashes bright red if the pressure falls below the preset. The accompanying audible alarm is very loud (luckily it can be permanently muted) and will be able to be heard with a helmet on for sure. Despite how it may look in the pics the gauges are perfectly visible for my driving position and visibility only gets better when I'm sitting lower in the car in the race seat.

    Sooooo....problem is the pressures. When water up to temp and oil at 100 degrees with car thoroughly heatsoaked my running pressures are fine eg 55 psi at 2500rpm which is regulation for the car and parks itself at 60psi above that which is the factory pressure relief in the oil pump. At idle though it'll sit at 14psi. The manual says 20-25psi apparently which I need to confirm.
    I am due for an oil change which I did just now so we'll see tomorrow if fresh oil and a jump from 5W-30 to 5W-40 gets the hot idle pressures into the pocket.

  9. #1819
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    I agree the factory pressure monitoring is a bit hit and mostly miss. Pretty convinced it cost me a bearing, which turned into another engine. I over compensated by fitting a Forge sump.
    Sam, I havent quite forgotten about the exhaust. I'll contact you tomorrow.

  10. #1820
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    Hey Gav. In the process of making baffles for my next sump at the moment. Just trying to locate some oil control gates to use. Found someone who supplies the Cosworth style flexible viton flaps but might still go aluminium hinged style if I could find anyone in the world who even sells them.

    Gav whats your take on the base oil pressure I'm seeing on the engine. Is 20-25psi the accepted range to your knowledge?

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