Project "Ultimate 1983 Rabbit GTI"
Index of Project web pages
Project Overview, Goals & Initial design specs
Project car initial condition
Bodywork & Paint
Suspension, Wheels, Tires & Braking System
Engine & Transmission
Electrical & Fuel System
VW Vortex Thread on this project
My original 1983 Rabbit GTI (owned 1983-1987)
Back in 1983 the VW Rabbit GTI delivered 0-60mph times of 9.7s and 1/4 mile performance of 17.7s @ 77mph. Those numbers seems very slow by today's standards, but they were class leading #s in the day (see all of the magazine reviews posted on my original GTI page).
With only 1800-1900lbs (race prepped with stereo, A/C and rear seats removed or fully decked out), even just on the 'motor' alone (at 240hp), thishot little GTI should have equal acceleration (until wind resistance starts to hold it back above 80mph) as my 2004 505hp AMG Mercedes Benz did, due to the 4300lbs weight of that car (and most other late model cars). That car did the 1/4 mile in 12.2s at 117mph and delivered a 0-60mph time of 4.2s. When the 100hp dry flow nitrous system is engaged, this GTI should be one fast and furious car, if the power can be transmitted from the wheels to the road surface ... stay tuned. Could it run a 10s 1/4 mile time slip?
33 years to the month, my GTI sat again in my childhood home’s driveway: I took delivery of my original GTI in May of ’83 but it didn’t get licensed until August ’83 (no job, no money, no license …).
I drove about 3 hours in the car in total today - yes it was driven in the rain and got nice and dirty (I took my family and my dad out for rides), shaking out the initial bugs and gremlins. It will be about 1-2 months to get the car behaving the part (fast, fun, safe and semi-civilized). I discovered lots of things that need addressing already: the brakes are a bit mushy and need professional bleeding, the steering alignment also could use a pro setup alignment, there are some squeaks and rattles, the fuel gauge needs calibration, one of the radiator fans is DOA (I don’t think I will need 2 after all so maybe it will just be disabled), for some reason the engine shuts off at 6,000rpm, just as the fun starts, there was a fuel leak when I topped up the tank, the windows don’t roll up properly, it is a bit harsh and noisy, etc - you get the idea ...
The GTI is spending the night at the mechanics and should be certified road worthy tomorrow so it can be fully licensed. I will then have time to run system diagnostics on the crank and cam triggers - I suspect that the old-school analog inductive crank sensor is crapping out and may have to be replaced with an external digital hall effect crank sensor (which requires that a 60-2 tooth wheel be placed between the crank pulley and the crank itself). There may be something else going on but the computer says 'lost sync' in the RPM readout and the ECU goes a bit nuts for a while so ...
With fuel in the tank, carpet mats, A/C, stereo, sun-roof, full interior, etc. it scaled in at 1950lbs, with a 66/33 weight distribution. With some of this crap pulled out on race days I'll have an 1800lbs car.
I have 3/4" gaps from the top of the tires to the fenders all-round so ride height is perfect. Suspension is H&R race springs and Bilstein race struts and shocks. A bit stiff but not as bad as I thought it might be. Still, I will also order in some H&R sport springs and try them out - September 1, 2016
I got the car inspected, certified road worthy, and licensed this week and then went out and drove it around for more than 3 hours - what a joy!
I confirmed a number of basic performance parameters via a series of full throttle acceleration runs and some hard cornering and slaloming dynamic tests: There is practically zero body roll with this suspension system and there is tons of grip but the car is not overly stiff/harsh except on rough concrete expansion joints where the car bounces around with its short wheel base. The estimated 0-60mph time seems around 4s but the tires can't hold the power in 1st gear at any RPM >3,500 so I won't know the true potential until I bolt the slicks on at the track. The computer has provided fuel data which allows me to estimate power and torque #s by using BSFC (for a street engine 0.5lbs/hp-hr of fuel consumption is reasonable but highly tuned race engines such as mine are more efficient at around 0.42lbs/hp-hr). At 0.42 BSFC my engine is putting out 260hp @ 7,250rpm and 200 ft-lbs of torque from 4,500-7,000rpm which is quite something. Obviously this needs to be backed up with dyno pulls, g-meter acceleration data, and track 1/4 mile racing results. I'll have the g-meter acceleration data in a few weeks. [see update below - this was estimating hp from the top rows of the fuel table at 101-102MPa - in practice the engine only sees 99MPa so power is actually 240hp, not 260hp]
The engine exhaust smells more than I think it should and the oily black soot in the exhaust pipe indicates that the rings have not fully seated yet. I took out the spark plugs and they are absolutely clean looking on the electrical contacts but the metal base rings are a bit oily. I also used a computer/USB microscope to look into the combustion chambers and inspect the pistons, block cylinder walls, and valves - I saw cross-hatching marks still on the cylinder walls which look evenly shiny 360 degrees around, but the edges of the combustion chambers were a little oily looking, with one cylinder actually showing a small drop of oil on the wall, plus the piston crowns looked a little fouled in spots and also a bit wet in spots from oil. The question I now have for engine builders is: how long should it take for my rings to seal (I only have about 4-5 hours of real engine running time where I have been driving the car and less than 10 full throttle acceleration runs to attempt to fully seat these racing rings)? Is there a problem with my rings not seating? I have been using Joe Gibbs Driven Racing Oil 00106 BR 15W-50 Break-In Motor Oil.
After my 3hr drive I realized that my new mini Denso alternator was burned out/DOA. It could have been my ECU control circuit which tricks the alternator into limiting its output voltage to 13.8V (for my LiFePO4 battery) by providing 14.6V into the Vsense input when the output reaches 13.8V. Anyway, I have ordered a PowerMaster 8188 XS Volt 75 Amp mini Denso alternator from Summit Racing with expedited shipping - this unit has fully adjustable output voltage capabilities plus an input that when grounded will reduce the output voltage 1.25V to cut the power draw from the engine by over 50% - saving a few hp during WOT acceleration runs - October 30, 2016
Power estimate from the ECU fuel tables - estimated about 20hp too high due to the use of 101-102MPa MAP values rather than 99MPa where the engine actually operates - see below ...
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 above 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:
288 cam, 11.5cr 2L ABF motor with common intake plenum on the rollers at NGP
288 cam, 11.5cr 2L ABF motor with common intake plenum at startup and idle
- February 27, 20167
My accleration and power measurements ...
Reference check: 288 cam, 11.5cr 2L ABF motor with common intake plenum on the rollers at NGP ...
The racing seats I just ordered for track and high performance driving needs ...
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 - March 20, 2017
I have been fooling around with my braking system, trying to set my rear brake line pressure to the correct level to avoid rear-first lockup conditions without success, and it didn't make any sense to me as I have a Wilwood adjustable proportioning valve in the system. I also wanted to explore ways to continue to improve the responsiveness of the brake pedal - to have it activate as quickly as possible with the minimum brake pedal travel, so I also sourced a 25.4mm master cylinder to swap in replacement of my current 22.2mm MC. This would have the net effect of reducing pedal travel 30% while increasing pedal effort by the same ratio, and since I already prefer running my brake servo vacuum at 50-70% of maximum available vac I can do the swap and maintain the same pedal effort by simply turning up the vacuum (I have an electric vac pump under ECU software control so this is easy to adjust on the fly in the car - I have a panel dial that I can simply turn).
Anyway, I sourced a 3,000psi line pressure gauge with the appropriate adapter fittings to screw into the blanked-off MC ports front/rear and also the bleeder valve ports on the front and rear disk callipers. I first tested the MC and both circuits showed 750psi without servo vac and 1500-1600psi with max vac. Note, I have a custom brake line setup with 1 circuit to the front and another to the rear to accommodate my proportioning valve - similar to many US spec cars.
Next I tested the line pressures at the front callipers and again saw the same 750-1,500psi range. Finally on the rears I saw 500psi at minimum prop valve setting and 1,500psi at full prop valve setting - the surprise was that I realized I had been turning the prop valve in the wrong direction when doing panic brake stop tests.
By reference the factory test settings for VW mk1-mk4 cars is around 1,500psi max for the fronts and 510psi for drum rears and a bit less (around 490psi) for rear disks, depending on the car. The front/rear bias ratio will depend on a lot of factors - the weight bias of the car front/rear, most importantly while under panic braking, and then the type of front and rear callipers or drums - how much fluid volume is required to move the pistons - the piston area x # of pistons will determine the total force applied to the rotors.
In my case I have upgraded to Wilwood 4 piston callipers so the volume of fluid that needs to be moved to get to maximum braking pressure is much higher than for a stock single piston calliper. I didn't do all of the calculations but I think that the 22.2mm MC is a bit small for the Wilwoods and also that the rear bias needs to be fairly low, in the 550psi range.
I'll wait for the ice and snow to melt (Hopefully later in January) and will get back out for some more panic stops with the current 22.2mm MC before swapping it out for the 25.4mm MC - January 2, 2017
After doing some more reading about the Wilwood proportioning valves I now understand that when they state 100-1000psi adjustment range they are not telling the whole story - their valves can only reduce the rear brake pressure to 57% of the fronts so if the fronts are 1000psi the rears will be 570psi. I did measure around 500-550psi at the rears during the testing above with the line pressure gauges installed but with the extreme front weight bias of my FWD GTI and my grippy rear disks/pads I may need to go lower still - as low as 400psi, so I have sourced a really tiny and cool little prop valve that can lower the pressure all the way to zero if needed and I will put it inline with the rear circuit so I can reduce the pressure even more if I need to. Once I go to the effort of swapping in the 25.4mm master cylinder I don't want to have to re-bleed the brakes yet again if I still experience rear lock-up ... better to take this additional step now while everything is apart - February 7, 2017
Josh had proudly sourced some OEM German axle assemblies for me but I found that they had some free-play in them which resulted in a bit of 'slap' when going on/off the throttle as that slack was taken up. Rotating the wheels about 1/4" was the total amount of movement but it was enough to make driving a bit annoying at times when feathering the throttle in city traffic. One theory is that I was using the brakes to load the engine when it was initially fired up on jack stands and the axles weren't totally level, causing the power to be transmitted thru the CV joints at an angle - that may have stressed them and worn them? Anyway, I ordered some expensive 500hp rated racing axle assemblies from The Driveshaft Shop in NC and they are superb quality, using CVs that are 40% larger with all components upgraded end to end. There is no free-play in these assemblies so I look forward to installing them soon - February 7, 2017
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) - February 13, 2017
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 - February 27, 2017
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_Mk1_Big_Brake_Conversion_Analysis.xlsx
- March 7, 2017
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 - March 13, 2017
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! - March 20, 2017
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)- March 21, 2017
The shift rod before it was bent to be parallel to the black bracket assembly - you can see that the rubber ball isn't centered - causing binding and travel limiting of the 1/3/5 gear positions ...
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. When decelerating from 5,000rpm the MAP signal drops to 17MPa which is the equivalent of 25" of mercury vacuum so the rings on the pistons have sealed nicely - April 2, 2017
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 - April 12, 2017
Index of Project web pages
Project Overview, Goals & Initial design specs
Project car initial condition
Bodywork & Paint
Suspension & Braking System
Engine & Transmission
Electrical & Fuel System
VW Vortex Thread on this project
My original 1983 Rabbit GTI (owned 1983-1987)