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    Thread: Building the Ultimate 1983 Rabbit GTI (vw mk1)?

    1. 02-14-2017 12:32 PM #551
      I finished the installation of the 3-axis accelerometer in the car and then did a fine tuning of the calibration in software on the ECU such that the sensors now read accurately to less than +/-0.005g for acceleration, and around +/-0.01-0.02g for braking and corning. I still need to confirm that vibration and electrical noise from the ignition system won't reducing the accuracy, but if noise is added to the signal I can always run a smoothing function in the ECU diagnostics and effectively cut out the noise.

      I installed the 25.4mm master cylinder and adjusted the brake pedal linkage, adding back one spacer (for a total of 2) between the servo and MC, and setting the pedal position such that the MC engages immediately within the first 1/10" of foot pedal travel. I also installed the mini proportioning valve in series with the existing Wilwood prop valve and then ran system brake pressure tests. It turns out that I had originally installed and set the Wilwood prop valve correctly as re-testing this weekend proved that even when set at the minimum setting, about 550-600psi of rear pressure is still present when the front pressure is 1000-1500psi (which explains why I was experiencing rear lockup).

      With the 25.4mm MC replacing the 22.2mm MC, the brake pedal travel is indeed 30% shorter and the force required to stop at a given rate is also 30% higher as expected. The reason for swapping MCs was done mainly to avoid having the pedal travel too far, making heal-and-toe braking into corners for downshifting purposes almost impossible - too much pedal travel puts the right foot at a sharp angle to the throttle making it way too easy to excessively rev the engine. Having 4 piston callipers up front takes more fluid volume to operate, causing the MC piston to travel further, etc., hence the preference for the new 25.4mm MC. And since I had previously decided that I liked less servo vacuum for a firmer pedal feel, all I needed to do to get back to the same pedal feel was to turn up the servo vac 30% and all is well.

      The new mini prop valve (Deltrol p/n 10120-40, Speedway p/n 910-31357) allows the rear pressure to be reduced all the way to zero if desired (for RWD burnout competitions this is what people want) so I was sure it would help me with my problem and it did work as expected. With the valve 80% turn off I got to a max pressure of 500psi and it ramps to that pressure over approx 1s so it has a damping effect on the rear pressure when the pedal is pressed which is actually not a terrible thing - if the prop valve is adjusted to the threshold of rear lockup this will soften the effect and reduce the tendency for a sudden change in direction (i.e. the rear of the car swinging wildly around to the front).

      I also installed Wilwood E type pads on the front which have about 20% higher coefficient of friction than the previous BP10 type pads - so once they are warmed up to around 250-300 degrees F the fronts will have more braking sensitively than before which may allow me to adjust the rear pressure up higher. When I am doing lots of track laps I will switch to BP20 pads which have the greatest coefficient of friction at temperatures above 800-1000 degrees F and again, I may be able to dial up the rear pressure more again. The idea is to have the rear brakes do as much work as possible to off-load the work the fronts have to do.

      I will be switching to the new front racing axles soon which require extended length racing type studs so I went ahead and installed extended length studs in the rear allong with the new Gorilla open backed 'tuner' nuts which are required when running extended length studs - I also had to use conical to ball seat adapters as the 'tuner' nuts are not generally available with conical seats - and I already have to run conical h/w for my Enkie/Hoosier racing wheels and slicks. I think they look decent enough on the OEM VW Snowflakes and they sure are a lot easier to mount/dismount than the OEM bolt system too.

      The snow and salt should be washed away by rain over the next week and I may then have a chance to do some road testing to confirm that I didn't add too many spacers between the servo and MC (last time I had 3 spacers and after a few minutes of driving the car started to self brake - likely caused by the brake system warming up and expanding a bit (my tolerances were too tight/aggressive).

      New photos here: http://derekspratt.com/HTML/Automoti...on_Brakes.html

      New video here: https://www.youtube.com/watch?v=kPs_5LBROeo

    2. Senior Member dubdaze68's Avatar
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      02-14-2017 04:25 PM #552
      Self braking, eh? Your car is afraid to go as fast as you intend to go.

      "No no no no NO NO!"
      DCIVW
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    3. Junior Member magnessr's Avatar
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      02-15-2017 10:11 PM #553
      Quote Originally Posted by Derek Spratt View Post
      Magnessr, which ITBs are you going to use? Will you run a dual set of injectors? How long with the runners be? Which block/heads? ABA/9A? Custom header too? Lovin' it.
      Planning to run the Bahn Brenner Borla 45mm ITB's. Single injector setup. I am unsure of runner length but don't want to run a plenum. Engine is a 9A 16v from a Passat. Head will be get a port/polish job and TT 34/28.5mm valvetrain with 288 cams. Block will be bored to 84mm, pistons 12.3CR with stock stroke. I will likely do a TT 4-2-1 header but that is tbd.

      Right now I am doing all the suspension/chassis modifications. I have a G60 engine to throw in with my 02A trans while I build the 16v engine as it will take some time. KW V3 coilovers. Wilwood 10" front brakes. Mk3 rear discs. Poly bushings. Etc.

      Plan is full track car. Can't wait to get it together over the next few months and ready for spring/summer.




      Sent from my iPhone using Tapatalk
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    4. Member rabfan's Avatar
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      02-25-2017 12:56 AM #554
      Hey Derek, I've been absent from Vortex for a long time but just found your website and thread. Very inspiring build. I have finally begun rebuilding my 84 gti(bought in '93).
      I strongly appreciate you documenting everything as you did and including where you had interior work done. Sadly my budget isn't as vast as your but I hope to bring the car to some level of former glory.
      Cheers,
      RJ

    5. 02-28-2017 12:31 AM #555
      I got the OEM axles pulled out and installed the new 500hp rated axles but it was a ton of work: first the spindles/hubs needed to be pulled apart so the new hubs (larger splines and shaft, 32mm nuts, etc.) could be pressed in with fresh bearings, then I over-extended the axle angles when installing them and had to re-build the inner CV joint on one side as the ball bearings had fallen out, then the inner cer-clip on one side was binding against the axle so it all had to pulled out yet again, and finally it all went back together successfully.

      After driving around with the new axles I can say that they definitely have tighter tolerances so all I am now left with is a bit of that on-off-on throttle free play from the limited slip diferential that I will simply have to live with - it is only noticeable during slow city driving in heavy traffic. That diff also whines a bit in comparison to the OEM unit - but I don't really notice the increase in mechanical noise much.

      The new 25.4mm master cylinder setup feels great - more pedal effort required but the pedal travel is now minimal so heel-and-toe downshifting will be much easier to do - and I simply like a stiffer brake pedal anyways. I just crank up the electric ECU controlled servo vacuum when I want an easier braking effort. The 2nd in-line proportioning valve has indeed solved my front-rear brake balance problem. Panic stops result in straight line skids now. I will wait for warmer weather with cleaner streets before fine tuning the balance setting (too much salt and sand dust still on the roads).

      I did have to back off somewhat on my brake pedal preload - I have a custom linkage that allows me to set the servo/MC preload to reduce pedal travel but I was at the point where there was a bit of self braking once the system was fully warmed up - backing off the brake pedal 1/4" solved that problem and now there is a softer initial brake response for the first 1/4-1/2" of travel which is actually a good thing. I am very happy with the end result.

      I changed the oil (another fill of the break-in oil) at 300kms and will finally switch over to full synthetic oil at the 600-800kms point. It is likely just in my head but I think the engine runs better with the fresh oil in it.

      I did a total of 6 acceleration runs with my new accelerometer and consistently saw over 0.5g of raw acceleration from 5,000-8,000rpm in 2nd gear which is quite something considering that I have the longer final drive ratio gearing installed in the transmission (I can reach almost 120kph/70mph in 2nd gear), so that means I am pulling with about 25% more Gs at 70mph than my old '87 Mustang did with its 340hp engine at 40mph. The GTI feels very alive above 5,000rpm and in fact it feels a little dangerous/unstable - you simply don't want to put your foot all the way into it unless the road is straight and smooth as the car will start to dance around and head into the rubarb if you aren't totally in control of things - you need to hold on to that steering wheel and keep things heading in the right direction. Heaven knows how I am going to handle another 100hp of nitrous on top of this.

      It is very easy to convert acceleration data into torque and hp - you just need to know the actual weight of the car and the rpm and wheel diameter and you have a direct measurement of the power being produced at the wheels. You need to perform a coast-down test to determine the losses due to wind resistance and rolling losses and that is all. I have confirmed 200hp at the wheels at 7,500-8,000rpm and 150ft-lbs of torque at 6,000rpm. Using the commonly accepted 20% drivetrain loss estimate for manual transmission cars that is 240hp and 178ft-lbs of torque for a 2.1L normally aspirated engine which actually idles like a stock engine at 1000rpm - that is a rare experience (for cars without computer adjustable cam profiles). I realize now that the hp calcs from October 2016 were based on the Holley ECU fuel flow tables at 101MPa of vacuum were over-estimating the hp simply because my MAP signal is actually only 99MPa at full throttle, not 101MPa so I never get to the absolute top of the fuel tables in practise ...

      Oh, and I just ordered some Sparco EVO racing seats and 4 point racing belts to keep me safe and secure while being tossed around at the track - the stock GTI seats are a bit wobbly and don't really have the aggressive racing-type side bolsters to keep me firmly locked in place and in total control of this wild hare. I'll use the stock seat belt mounting points to fabricate and install a mini roll-bar and seat/seat-belt brace structure, plus I have ordered a pair of GTI seat frames to allow me to fabricate mounts for these Sparco seats that will simply attach to the stock seat h/w in the floor.

      I have included the wheel hp/torque measurements for a similar 2 litre ABF motor with the same Techtonics 288 race cams and similar heads and compression, but with the OEM log-style intake system below. It achieved the same torque at the same rpm but ran out of high-end breathing due to the intake manifold, where-as my ITBs allow power to keep building past 8,000rpm. ITBs and careful ECU programming also allow my engine to idle and have excellent part throttle/low rpm drive-ability where-as this other car barely idles and has terrible sounding part throttle response:

      http://forums.vwvortex.com/showthrea...BF-Info-inside

      288 cam, 11.5cr 2L ABF motor with common intake plenum on the rollers at NGP
      http://www.youtube.com/watch?v=1YeZNElfsNo

      288 cam, 11.5cr 2L ABF motor with common intake plenum at startup and idle
      http://www.youtube.com/watch?v=VILRqAkv24I

      My new video is here: https://youtu.be/2Iofa-6ooho

      My new photos are here: http://derekspratt.com/HTML/Automoti...on_Brakes.html and http://derekspratt.com/HTML/Automoti...rformance.html

    6. Member
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      Now: 84 Gti Callaway. Then: 79 Rabbit; 83 Gti, 80 Scirocco S, 86 Gli, and a few flips.
      02-28-2017 11:44 AM #556
      It always makes my day to see a post and new video on the Spratt GTI! For those that feel the same way check out Project Binky on YouTube.
      Great update Derek and can't help but continue to admire your pursuit towards "perfect". Looking forward to your acceleration tests so I can get a
      feel for how this amazing car performs vs. other modern day cars. You will need more tire when the time to comes to push that extra go fast button!
      Hoffa

      My 84 Callaway
      WANTED: Callaway/Moroso 1.8 valve cover throttle bracket and plastic vent tube Pls PM if you have one kicking around

    7. 03-04-2017 01:40 PM #557
      I can't wait to see the seat install. I'm looking into getting racing seats for my mk2 scirocco but don't know what to do scout seat belts.


      Sent from my iPhone using Tapatalk

    8. 03-07-2017 01:53 PM #558
      After further thought I have decided to purchase the unique Tech-53 callipers (made specifically for Tech-53 by Wilwood) and replace my standard-issue Wilwood Powerlites as the Tech-53s have 68% larger piston area, which will vasty increase my stopping power relative to brake pedal force, and more importantly will improve my front/rear circuit bias such that I can run without the 2nd proportioning valve.

      After a long discussion with Fred, the owner of Tech-53, about my brake bias issues, pedal pressure requirements for a panic stop, etc. it became very clear that my Wilwood PowerLite 4x1.25" piston callipers were undersized relative to the task at hand - in fact they are only 15% larger in total area than the stock single piston callipers so they don't effectively shift enough of the brake bias forward to avoid premature rear wheel lockup.

      Fred is an aerospace engineer who has put in a lot of time into thinking about the lack of properly spec'd 4 piston callipers that are available for mk1 and mk2 cars so he went about negotiating a deal with Wilwood to have some large piston callipers custom made to his specs. They use 1.625" diameter pistons vs the 1.25" diameter pistons in my Wilwood Powerlite callipers, thereby providing 68% more clamping pressure (and therefore braking torque) - and that means that for a given brake pedal pressure the car will stop 68% faster - up to the limit of the tires, with minimal increase in pedal travel. Since I have a huge, race oriented 25.4mm master cylinder, pedal travel and feel will not be negatively impacted. Fred says the 23.8mm MCs are an ideal street match to his callipers and that 25.4mm MCs are awesome on the track - since I like a stiff brake pedal I am pretty sure I'll like the feel on the street as well, given that I am already pretty happy with the way my existing system feels.

      Fred also pointed out that the G4 rear aluminum callipers are 2mm larger than the steel G1-3 callipers (38 vs 36mm) so that aggravates the premature rear lockup issue. I am confident that I will be able to eliminate my 2nd proportioning valve now and also be able to dial back the Wilwood valve to reduce the time delay effect in rear circuit pressure build-up.

      I have completed a brake conversion table with all of the common after market setups (brake torque, front-rear bias, etc.).

      My excel spreadsheet analysis can be found here: http://www.derekspratt.com/Misc/VW_M..._Analysis.xlsx

      New video here: https://youtu.be/3kIS1SCCXPU

      New photos here: http://derekspratt.com/HTML/Automoti...on_Brakes.html
      Last edited by Derek Spratt; 03-08-2017 at 03:52 AM.

    9. 03-14-2017 02:13 AM #559
      We still have winter conditions in the Pacific Northwest for the most part, but there are the occasional days when the sun is out and temperatures are up enough to do some driving/testing. The roads still have a lot of sand on them so traction is limited and the sand gets into the brake system as well ...

      My first attempt at driving around the block with the new big piston Tech-53 callipers was cut short by some nasty sounds coming from the front wheel area. I had obviously checked the clearances so I was puzzled about what the sounds were. My inspection found that the control arm ball joints were lose - the 'grade 8.8' bolts were actually stripped and so the ball-joints were barely being held in place. Yikes! It turns out that the crap bolts were imported junk and are now being replaced with OEM/German grade 10.9 h/w. Double-check the h/w on any aftermarket control arm/ball joint combination products that you may purchase ...

      Another area where cornering noise was coming from was due to the new CV boots sticking/rubbing each of the folds against each other - by 'lubricating' them with rubber care treatment they became quiet as well. Finally, sand was getting into the brakes causing some intermittent scraping sounds (I don't use OEM dust shields to help cool the rotors on the track).

      With all of those gremlins out of the way I was able to do some braking tests: the Tech-53s take about 1" more travel, which makes sense, as the volume of fluid required to push those big pistons is greater, but the force required is a lot less, making the brakes feel very responsive and powerful, which is what I was hoping for. I will look into adjusting the brake pedal linkage again, putting a bit of pre-load on the system - and double-checking that I am not over doing it as in prior attempts to reduce pedal travel. With the large 25.4mm master cylinder paired to these Tech-53 callipers the pedal feel and travel are close to ideal now. The biggest area of improvement comes from re-balancing the front/rear braking bias - I have now fully opened up the 2nd proportioning valve and panic stops in the rain did not cause pre-mature rear wheel lockup so all is well. I will start to back off the reduction setting in the main Wilwood proportioning valve next ...

      I need more time to drive in dry conditions, which I should be getting by the end of the weekend so stay tuned for more commentary on this new braking system. I am all smiles for now.

      New video here: https://youtu.be/2CBfxonS7_8

    10. Senior Member dubdaze68's Avatar
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      03-14-2017 09:12 AM #560
      Fred is an amazing guy, and I've got to see most of his parts lineup in person. To say "Quality" is an understatement, and he backs everything he makes. He's also a nut. Love that wily Canuck.
      DCIVW
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      03-14-2017 01:45 PM #561
      Quote Originally Posted by dubdaze68 View Post
      Fred is an amazing guy, and I've got to see most of his parts lineup in person. To say "Quality" is an understatement, and he backs everything he makes. He's also a nut. Love that wily Canuck.
      x2, check out his Scirocco/racecar builds, his username is fredybender.
      Work: it works, ibtches.

    12. Member Blade3562's Avatar
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      03-14-2017 03:10 PM #562
      Someone needs to sell Derek some 1552s. The Extra inch of snowflake would just put it over the top. Can't wait to see how this holds up over the long run! I'm sure it's a blast to drive!

    13. Member veedubman72's Avatar
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      03-14-2017 05:32 PM #563
      or he could contact Fredybender for that too. Custom 2 or 3 piece snowflakes


    14. Member Blade3562's Avatar
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      03-14-2017 11:54 PM #564
      Don't get me wrong I think people who build custom wheels have some talent, but I'd be afraid about impact analysis etc. Especially living in NEOH.

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      03-15-2017 08:01 AM #565
      AFAIK legally DIY wheels are designated for track use only, not the street because they don't have regulatory approval?
      Work: it works, ibtches.

    16. 03-20-2017 01:48 PM #566
      After tracking down the grinding noises from the front end while testing the system I noticed that the clearance from the outside edge of the rotor to the inside surface of the calliper was minimal on the driver side and there was evidence of some minor contact. I was able to loosen and move the calliper to gain more clearance but decided that for racing thermal expansion purposes that I would increase the gap from 0.020" to 0.070" by milling the rotor down from 10.1" to 10.0" - this still left enough surface area for 100% brake pad contact so there will be no reduction in braking performance. I also had some minor contact between the outside edges of the callipers and the inside surfaces of the 14x6" OEM Snowflake wheels so I have swapped out the 3mm spacers for 5mm spacers.

      After bedding the new pads the brake feel from this new Tech-53 big 4 piston calliper system is incredible. I did some brake pedal linkage adjustments such that the pads contact the rotors when there is less than 1/4" of pedal travel so the brakes are now very responsive. I believe that these callipers are a huge advance in mk1/mk2 brake performance/feel and certainly address the prior issue of front/rear system bias - I have not backed off the proportioning valve but will do so later today and do some more testing. Even with the valve at its current setting the car stops urgently with only moderate brake pedal pressure. I also think that the 25.4mm master cylinder is an ideal match to these Tech-53 callipers.

      With the prop valve backed off 2 full turns I was able to get all 4 tires to enter a skid condition together at the same time. Max braking deceleration was almost 1.1g with the street R-compound Bridgestone Direzza-II 185/60-14 tires (when the air and road temperatures were only 50 degrees F) so this little bunny is stopping with the best of them now!

      I made the decision to be safe on the race track with Italian Sparco racing seats that will hold me securely in place for improved driving accuracy, equipped with 5 point harnesses to keep me safe if something bad happens (note, I am going to attempt to use a Simpson single anti-submarine lower belt rather than the dual belt Sparco design as I think they are cross-compatible with both cam-lock systems). I received my new racing Sparco EVO seats which are really nice and started the process of cutting up some OEM seat bases to use as a foundation for a 1x1" square tube mounting base for the seats - the idea is to have the convenience of the stock mounting locations and fore-aft adjustability. I am also fabricating a cross-tube to mount the shoulder belts to that will attach to the upper and lower frame bosses for the OEM seat belts. I will likely race with just the driver seat installed - no passenger or rear seats for weight reduction purposes (unless I am showing off and having a passenger on the track which will happen from time to time). I am also fabricating a horizontal extension plate for the shifter as it is too far forward to reach comfortably when held in place by a 5 point harness.

      New photos here http://derekspratt.com/HTML/Automoti...on_Brakes.html and http://derekspratt.com/HTML/Automoti..._Interior.html

      New video here: https://youtu.be/URlhhBzP4e4
      Last edited by Derek Spratt; 03-20-2017 at 09:44 PM.

    17. 03-20-2017 01:50 PM #567
      I didn't know about these custom snowflakes - very interesting ... thx for sharing!

    18. 03-21-2017 04:52 AM #568
      What pads did you get, Derek?

    19. 03-22-2017 03:30 AM #569
      I had been struggling with poor shifter feel/engagement into 1st gear and so I set about disassembling the shift linkage in order to step-by-step find out where the problem area was. The transmission selector lever itself had a nice positive feel and clean engagement of each gear but I found that something in the linkage was resisting full movement into the 1/3/5 gear positions. It turned out that the rubber ball lever end wasn't moving smoothly and upon closer inspection I could see that the metal rod portion of the rubber ball lever was binding on the metal bracket that it is inserted into - and this was caused by the shifter rod being at the wrong angle as it entered the positioning bushing/bracket. So I pulled the shifter rod out of the car and bent it about 7 degrees about 8" back from the end and it was then perfectly parallel to the black mounting bracket assembly and positioned the metal bracket right in the middle of the rubber lever arm. I was worried that my 0.040" metal shim inside the metal bracket was causing binding with the rubber ball but once everything was aligned properly and greased up, the rubber ball rotated smoothly and didn't bind at all. With a 1/2" lengthening of the upper ball-joint arms to re-align with the new setup, everything was tested and then re-torqued into place. The result is 100% improved shifter feel and perfectly positive engagement in every gear. I am in shifter heaven now.

      New photo here: http://derekspratt.com/HTML/Automoti...ine_Trans.html

      New video here: https://youtu.be/efkgKI02wjc

    20. 03-22-2017 03:34 AM #570
      Fred/Tech-53 supplied 2 sets of pads: Hawk HPS for street use, and Hawk DTS60 for track use. The HPS pads, once fully bedded, provide huge stopping torque (estimated 20-40% greater than for OEM pads) - they use a 'Ferro-Carbon' material that is quoted to be low dust, low rotor wear, quiet and powerful. I would agree with that from my initial use. By comparison, my Wilwood E pads on the other Wilwood callipers created larger amounts of brake dust.
      Last edited by Derek Spratt; 03-22-2017 at 01:48 PM.

    21. 04-03-2017 11:15 AM #571
      I finished the fabrication of the seat mounts for the new Sparco EVO racing seats using the mounting flanges and legs from a junker set of OEM seats - they worked out very well - a little lower position than the stock seats and full adjustability of fore/aft position using the OEM mechanism and slope using some bolting options with the Sparco mounting flanges. Should be sweet!

      I don't have a tube bender so Ted at JetFab in Richmond, BC will be fabricating the bolt-in roll hoop which will use the stock seat belt mounting points to secure it to the body of the car. The hoop will have the cross-bar for the shoulder harness mounting points plus a central camera mount. When it is complete I will send the seats and hoop out for powder coating.

      I am also fabricating a rear shock tower cross-brace that also connects into the rear bumper mounts which will be needed as a mounting location for the nitrous and air tanks (the 4500psi air tank pressurizes the nitrous bottle to 925psi and holds it exactly at 925psi using a regulator rather than relying on a heater which doesn't keep the nitrous pressure constant while it discharges). I don't think the brace will actually have much effect on stiffening the chassis further as it is already welded up with a sub-frame, cross-bracing and will soon have the roll-bar ...

      I was complaining about the Walbro 393 fuel pump making a nasty noise so I talked with Kinsler Injection which supplied me the whole fuel injection system and most of the engine sensors, wiring harnesses, etc. and they said 'check your 25 micron intake and 10 micron output filters' so I did and found the intake filter completely plugged up with a nasty black sludge which looked like jello! The intake filter is a steel mesh so I cleaned it while I replaced the 10 micron paper filter and also replaced the pump as it had been damaged from the stress of pumping against such a massive restriction. The black sludge could simply be from old gas sitting in the tank for months at a time (if that is true it is actually from bacteria which is always present in fuel, more in ethanol enhanced fuels which also are hydroscopic and suck up water). There is also the possibility that my dumb attempts to seal-up my old fuel tank level sender with silicon sealant (since replaced with a new sender and o-ring) may have caused this as the silicon dissolved in the fuel. Anyway, I will keep an eye on this issue and service the fuel system filters more often. Next time I will do this when the tank is almost empty, rather than completely full! It would have been smart to have installed a fuel tank line valve too - I rely on hose-end plugs to service the fuel system.

      Finally, I have put 1100kms of mountain driving on the GTI so far with 700kms of that this last week alone - 3 days of driving to Whistler, with 25,000' of total vertical climbing. I switched out the Joe Gibbs break-in oil now for their 10-30W hotrod conventional oil which contains lots of ZDDP zinc to protect my solid lifter cams/tappets which are under extreme pressure from 8,000rpm and high lift racing cams and springs. I will switch again to their 20-50W oil when I get to the track in May. I may eventually switch to their synthetic oil with ZDDP added to it after 5,000kms.

      New photos here: http://derekspratt.com/HTML/Automoti..._Interior.html

      New video here: https://youtu.be/8uoPBxHzO3A

    22. Senior Member dubdaze68's Avatar
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      04-03-2017 12:03 PM #572
      How is the powerband? Is it pretty streetable?
      DCIVW
      CE.

    23. 04-13-2017 02:31 AM #573
      For over 30 years now I have been measuring vehicle performance using accelerometers and then using either my own programming or off-the-shelf software programs to further analyze and predict performance, helping to choose rpm shift points, gear ratios, wheel and tire combinations, etc.

      For this project I again used accelerometer measurements, along with fuel flow data from the Holley ECU to confirm the engine torque and hp curves and I loaded that data into Excel and added nitrous in varying amounts to see what kinds of torque/hp curves could result and then fed that data into a drag racing simulator, Drag Racing Pro v2.0, and adjusted all of the vehicle and driving info to produce realistic 0-60mph and 1/4 mile charts and graphs, using my newly acquired Hoosier 225/50-15 DR2 drag radials on 15x8" rims, using my excel data. The results are as follow:

      Engine only (no nitrous): 0-60mph 4.1s, 1/4 mile: 12.3s @ 112mph

      Variable nitrous to produce a flat 200 ft-lbs torque curve: 0-60mph 3.8s, 1/4 mile: 11.8s @ 117mph

      60hp nitrous at all times: 0-60mph 3.5s, 1/4 mile: 11.5s @ 120mph

      80hp nitrous at all times: 0-60mph 3.4s, 1/4 mile: 11.3s @ 123mph

      The simulator shows that a FWD car like the mk1 golf is severely traction limited due to the weight on the driving wheels being only 50% during acceleration, vs a RWD car that would have 80+%. So even with slicks and a solid trans mount and stiff springs the best I can hope for is a 1.9s 60' time and a little over 0.81g of acceleration in 1st gear.

      I already know that 1st gear on the motor alone with sticky street tires is a 50-60% throttle gear, but with nitrous even 2nd gear with slicks becomes a problem. It will be fun to get the car on the track soon and find out (May 12th is the 1st local track 'test and tune' day that I will be ready for).

      Ted/Jetfab has the roll-bar finished now so it is out for powder coating. Seat mounts are done too so all safety gear that I want to have for track days is now 'good to go'.

      New video here: https://youtu.be/6s9wYpSIfik

    24. 04-13-2017 02:34 AM #574
      Using ITBs really tames the 288 race cams such that the idle-4500rpm range is very stock like, then the motor wakes up and become a full race engine above that point, pulling hard past 8000rpm. You can idle around town and short shift and put your foot down at 1500rpm and it just pulls away .... amazing. I am a lucky guy.

    25. 04-14-2017 12:26 AM #575
      Or a talented one.

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