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Yet another turbo build (but bike is actually running already)

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  • Yet another turbo build (but bike is actually running already)

    Hi all. For starters, sorry for long first post, but as I kept writing, more and more things came to mind that I would like to write to you people. But now to the case itself.

    Yes, there has been quite a few turbo build thread that.., well.., never got finished, or atleast the topics have went dead without actually seeing a running and boosting bike. There is though atleast one person that I am aware in this forum with the running rear mounted turbo 600 and from his messages I have also gathered some helpful tips for my build. I also have some questions below for people with more knowledge as there is still few small problems I am dealing with (mainly spark).

    As for my bike, it is running currently, but the bike is still in it's tuning state, so it runs and boosts, but not perfectly. As it's not even spring yet here in Finland, the weather is pretty cold and I have been able to ride the bike with this setup only about 200 km (~120 miles).

    Here is a little preview from my very first ride with it being boosted. I have a camera to record my wideband and boost gauge, as there is no time to see what they read when I accelerate it (life flashes before my eyes when boost kicks in ) And as it is still using the stock carbies as a blowthrough type of system, there is no way to properly datalog (Innovate Wideband actually has a logging software but needs a laptop to log and I really don't want to carry that on a backbag with while riding the bike).

    I have done some more work on the bike after this video was recorded. I have been having issues with boost creeping and on some accelerations I have very briefly boosted just over 1 bar (about 15 psi) after 9k rpm. Below 9k rpm boost has stayed at around 0,4 bar (~6 psi). I plan to ride only with around 0,5bar (~8 psi) so no intercooler. Also after 7k rpm I have been having issues either clutch slipping (only stiffer clutch springs) or the rear wheel slipping (currently have a "Kreylyn style modded and extra bracing on the swingarm with a busa 6" and 190 wheel). Bike has lifted it's front wheel only once when the boost has come on. Boost creeping I think is caused by my internal wastegate not flowing enough. I have ported it now, and ridden the bike once, but my memorycard went full after 2 min, so unfonately no "datalog" from that run.
    • Question 1: Is pre Katana 600 clutch with 6 spring plate any better than the 750 with the 4 spring plate, is there any more pressure to hold the clutch without slipping? Both bikes use the same clutch disks and basket, but the inner parts are a bit different as other is 4 spring and other 6 spring. If I remember corrently looking at the part numbers GSXR 750 (first watercooled models) have the same inner 6 spring parts as pre 600 Katana? Or is there any other bolt-on clutch with better gripping power than current stock.
    Bike also runs a little rich all the time (better too rich than too lean), especially at wot as it is near 10 and I would like it to be about 11. Cruising is also around 12-14, depends little from the speed I am cruising. Stock jets are 105 and I have currently size 100 on #1 and #4 and 102,5 jets on #2 and #3 on the carbs as those were the next smallest sizes I currently have on hand. Next are all size 98, so I will install those when I have time to dismantle the bike again, because the first jet install did pretty much nothing to wot mixtures. Fuel level on the carbs is also currently a tad too low, as there is a little hesitation, bogging and mixture goes extremely lean for a second when blipping the throttle at cruising. I have some kind of knowledge on what to do next but all tips are welcome. Needles are currently at center position.

    As for my setup and some info of it, as some people propably would like to know some more about the hardware side of things.
    • Turbo is a Garrett GT20 from a ~2000 model Merceces Benz 200 CDI. It's from 2.2 liter diesel inline 4, so the turbine housing is a bit smaller than in a GT20 petrol version turbo. Can't find any exact specs online for this turbo as it is a 3 bolt version, not 4 as all other GT20 spec sheets are what I have found.
      • Turbo was only 50€ (55$) so decided "what the hell, lets give it a try and see how it works". Bike starts building boost at around 4-5k rpm, reaches 0,4 bar at about 7k rpm and maybe still starts to overboost after 9k rpm. Still need to do more riding and "datalogging" to determine is it still so after porting the wastegate. Some people say that a low rpm boosting bike is dangerous as there is a high risk of getting boost spike in the middle of a corner. Haven't ridden this bike enough yet to tell that how this thing handles corners considering boost levels. On the highway speeds cruising at 100 km/h (60 miles per) the bike is already boosting around 0,2 bar with the rpm sitting at the 5k rpm. I also used some online calculator to determine how much the Merc has airflow at it's peak rpm and how much my 750 has airflow at it's peak rpm, and the bike has less. So it probably should not cause the turbo to stall at peak rpm on my bike. But time will tell as I continue my tuning and riding.
    • Custom made log type exhaust manifold with the turbo at front
    • Because the turbo housing sit just above engine oil level I have to run oil container and a scavenge pump, which is a Facet Posi-Flow (in the UK people have been running these on boosted B12 engines years and years without issues)
    • Custom made sheet metal plenum with custom made steel boost piping and silicon couplers
    • Custom made 2,5" turbo back exhaust with Viper exhaust can
    • In-tank walbro 255 style fuel pump with 3 psi base pressure (one pain in the ass to install and would go with an external if I were to do this again)
    • Genuine malpassi fuel regulator (which is meant for turbo carb systems)
    • Some generic blow off valve
    • Wastegate is internal running with the stock wastegate actuator, which had to be modified from vacuum operated to boost operated
    • Ebay find oil catch can straight from China
    • Ignition is still stock, but retarded about 5 degrees by turning the ignition back plate. There might be some issues with my ignition not coping at high rpm as I can hear some pops from my exhaust on wot near redline.
      • Question 2: With this I could use some info from people with more knowledge. I am currently running the stock plugs JR9C which are twin tip. Should I run JR9B which are single tip and gap them smaller, or is there a cheap (and I really mean cheap mod) to run different coil/coils which have stronger spark. Dyna coils are an option, but a bit on the expensive side locally here in Finland. Any other generic powerfull, yet cheap coils which are 3 ohm like the oem coils?
    I also have a ton of pictures and videos of the bike, so if people are interested, I can try to write and share more here of the bike from the very beginning of the build. Sorry about the photobucket banners on the pics. It seems that it has changed to a chargeable service since I last used it.

    Here is how she sits at the moment (no side fairings currently on)

    A little close up from the turbo and oil drain system

    Modded swingarm

    Swingarm from a different angle

    Wider rear wheel from the back (before braces were added)
    Last edited by IhmeJanneFIN; 04-10-2020, 12:21 AM. Reason: Edited the coil question
    Suzuki GSX 750 F -94
    - 600 tailmod
    - Full 1200 bandit exhaust with Viper can

  • #2
    Been doing some work again on the bike. Took carbs out and installed 98 jets to all carbs and and lifted the fuel level back to stock (was 1 mm lower). WOT is now quite ok since it's around 11-12 according to my "video logs" but everywhere else bike's behaviour went actully worse. Once fully warmed up it would splutter and stutter at low speed cruising around 2-3k rpm and idle was very rough and "soggy, wet type of running". So took carbs out again and lowered fuel level back down the 1 mm and the bike still runs rich all around but would not splutter that much at lower rpms. Cruising at 80 kmh or above is still around 11-12 once fully warmed and with a slightest blib would lean bog (afr goes very lean) and then start to run again like nothing has happened. Have been playing with pilot screws also and they have been between 1 to 2 turns out with an afr at idle betweeen 11-14. Bike would also always hesitate around 4k rpm when accelerating, but after that it starts to boost and "off we go" like no worries of the world at all.

    Which has puzzled me all the time tuning this bike has been the rich cruise afr no matter what I do with the pilot screw settings, needle height or main jet size. If I set the idle afr to around 15 it starts and runs idle fine, but the screw would be only about 1 turn out and cruising afr would still around 11-12. Been googling different forums about cv carb tuning and then I came across few topics of the rubber plugs and if they are needed in different carbs etc. Well after reading numerous posts of those and few Kreylyns sticky worthy explenations, I came to an conclusion that those rubber plugs must be leaking and providing extra fuel to the idle circuit causing unwanted high mixtures.

    As the weather is going to take a turn to colder side I have time in the garage to inspect this suspection of mine and order new rubber plugs just to be sure. Hopefully this would solve my richness problems.

    If anyone has any different ideas for the richness, or anything other considring something on this bike I am happy to hear them out.
    Suzuki GSX 750 F -94
    - 600 tailmod
    - Full 1200 bandit exhaust with Viper can


    • #3
      Great looking job! I haven't seen much turbo Katanas around. it is nice to see fellow katanist doing some extreme.

      ps. terveiset oulusta!


      • #4
        Originally posted by Byge View Post
        Great looking job! I haven't seen much turbo Katanas around. it is nice to see fellow katanist doing some extreme.

        ps. terveiset oulusta!
        Thanks. Have been riding the bike now for about 1500 km in total. Now the bike rides quite good actually. Only "problem" I have is hard startup, especially on a hot bike if it sits for a few minutes. It has a veeeeeeeeeery long crank and have to help with throttle. Don't know if it's the fuel level or what. I have played with the fuel level a little bit and it sits now about 0,5mm lower than stock. If I raise it, bike starts better when cold, but once it's warm it idles very rough and runs rich everywhere. If I lower it, bike tends to lean stutter when giving it throttle.

        Anyhow, bike starts building boost around 5k rpm and is already boosting about 0,5 bar at 6-7k rpm and after that about 0,7bar. I have a "Turbosmart" 40mm external wastegate and a screamerpipe which goes under the bike. I like the screamer pipe a lot, it sounds phenomenal . Also at first gear it's damn near impossible to do a quick acceleration without boost wheelie as the boost kicks just before this engines first "power spot" in so low and quickly. Next gears it just pulls, no boost wheelie.

        I have to get it to the dyno in the next few weeks on my summer holiday to see how much power it actually makes. I am hoping for atleast 150hp at the crank, which is already a hefty 50% increase in power, and everything above it is just extra. And I am planning to have the turbo registered so if something happens to the bike (someone stoles it, crash etc) insurance company wont deny payment because of it not having the turbo registered and illegal because of that.

        Ps. Terveiset Limingasta. Tää pyörä pyörii Oulun seudulla niin moikataan jos tavataan.
        Last edited by IhmeJanneFIN; 06-27-2020, 06:01 AM. Reason: First post left a bit early.
        Suzuki GSX 750 F -94
        - 600 tailmod
        - Full 1200 bandit exhaust with Viper can


        • #5
          Took the bike to dyno yesterday and max power was 174hp from the crank with 0,65 bar (~9,4psi) of boost. That was achieved using 0,5 bar with spring pressure only. First run of the day with 0,2 bar spring and actual boost of 0,35bar was 143hp from crank. The wastegate cracks open at the spring pressure, but the actual boost is a bit higher than. That seems to be the case with other people also using Turbosmart style wastegates. Will post the dyno chart later when I am back from my holiday trip.
          Suzuki GSX 750 F -94
          - 600 tailmod
          - Full 1200 bandit exhaust with Viper can


          • #6
            Here's the dyno chart as promised and some story telling.

            This pull was ran on 6th gear and WOT from 3000 rpm to around redline at 12 500 rpm. Throttle was released before actual spark cut, because it would make a huge flame pop from exhaust and screamer pipe and this would make a powerspike to the dyno chart (we had one like that before this pull). Top speed with current gearing (17-46) would be around 255 km/h (about 160 mph).

            Fueling on wot is little bit on the rich side before the boost comes on (need to work on that). I currently have factory pro needles on the leanest setting, because the bike runs best with those needles with max of 3/4 throttle openings and when I am cruising. OEM needles don't give as much torque on off-boost situations and with oem needldes bike seems to have flat spots before boost kicks in. And quite frankly, I rarely use wot on the street as it is not necessary with this much power and how quickly it comes on. Bike will wheelie on first gear easily with part throttle also and speeds would be on the illegal side in a hearbeat. Anyhow, the rich situation at wot I think is the reason why torque line is "sawblade like" around 4-5 k rpm. Well, theres quite a drop at 7000 rpm also and it's not exactly smooth anywhere else either, but quite good I think.

            But as you can see, the bike reaches desired boost levels of 0,5 bar around 6500 rpm, just before the 7000 rpm power spike which this engine has when it's naturally aspirated (as far as I can remember this bike as NA), so on the road, above 7000 rpm all hell breaks loose with this bike.

            On this dyno pull it seems to have started to boost quite right away at 3k rpm, but in real life the boost gauge needle starts to move to positive side around 5000 rpm and full boost is just before 7000 rpm.

            Ps. Here is a little compilation of how the bike sounds if I take the bow off and block that hole and let the turbo flutter.

            Any comments on the bike? Have I done a horrible job turboing this bike?

            About the chart:
            Black line is the horsepower (from crank, the dyno calculates the drivetrain loss).
            Red line is the torque in Nm.
            Purple line is the boost pressure in bar.
            Y1 = horsepower 0-200
            Y2 = torque 0-150 Nm
            Y3 = boost 0-1 bar

            Suzuki GSX 750 F -94
            - 600 tailmod
            - Full 1200 bandit exhaust with Viper can