DoctorMotorcycle's Turbo Kit Development for 86-03 Sportster 1200's

[ChinCactus]

You guys build some great bikes!

[DrMotorcycle]

Originally Posted by ChinCactus

You guys build some great bikes!

Thanks

[DrMotorcycle]

So far we're nearing 10,000 street miles of testing. At least 500 1-4 gear pulls on pump 91 (on 10psi), at least hundred pulls in 100+ degree weather, hot idle testing, cold start testing, 20 or so different jetting combinations, countless timing map/setup changes, plenum changes, exhaust manifold changes, and a ton of other minor stuff. I've gotten to know the Evolution Sportster very well at this point, having lived with it rain or shine for the past 12 months.

I've also received a ton of feedback from many different sources; with all of this knowledge, I'm going back to the drawing board one last time to build the ultimate draw-thru setup for the Sportster. It will incorporate the following;

-A Custom Programmed Ignition system that uses a MAP sensor which will allow us to simulate the higher idle and cruise timing of the stock ignition, while also being able to greatly reduce ignition advance under high throttle situations, and high boost situations. This also means that the ignition curve will automatically pull more timing in the event you run more boost. A huge win for reliability!

-The ignition setup will also have outputs for a fuel-pump, inputs for a quickshifter and/or 2-step launch control. It will be up to the customer to decide whether you want a 2-step or quick-shifter. I will be experimenting with both before bringing the kit to market, it will be an option in a drop-down menu when ordering on my website.

-The new turbo I'm using is much more suited to the torquey character of the long-stroke twin. It's considerably smaller than the T28, which means it will spool much, much earlier and be very "punchy"; pretty muich 0 lag. It will still support 200HP @ the crank.

-Smaller turbo will allow the kit to be suitable for 883's as well

-Whole kit is being relocated; it will be tucked in near the bottom of the cylinders and very close to the bike, freeing up all of the legroom that the old kit took up. Will work on both mid controls and forward controls.

-Plenum volume is going to be increased another 50%; the total volume will be close to 1.5x displacement, a huge increase from the original setup which basically went straight into the heads (probably 300cc?).

-Exhaust manifold is going to have equal length primary tubes and a proper 2-1 merge with exhaust pulses facing away from each-other and towards the hotside of the turbo. This change will help keep the Air/Fuel Ratio the same between the front and rear cylinders and also help with preventing reversion/pushing the dirty mix back into the cylinders.

That's the bulk of the changes. The main reason for doing this is that I want the kit to be of the highest quality for my customers. I also believe that once the final kit goes into production, it will be very obvious how much thought and development went into the final product. The goal is to have 100% of my customers satisfied with the kit. Just don't think that's possible with the current setup on the sportster.

BTW, current setup on the sportster will be for sale. Will include a brand new, never used turbo and all new gaskets with it. Will also be adding the proper 2-1 merge to this header before selling; I want to see how it impacts how it runs. My gut instinct says it's going to be better in every way.

Sorry for the rant, just want 'yall to know where we're at. I'm thinking production will start late q2/summer of this year.

-Jimmy

[Tomcatt]

Originally Posted by DrMotorcycle

-Exhaust manifold is going to have equal length primary tubes and a proper 2-1 merge with exhaust pulses facing away from each-other and towards the hotside of the turbo.

Sure you don't want un-equal length primary tubes so the exhaust pulses are more evenly spaced entering the collector?

[MODO SIKLER]

Originally Posted by DrMotorcycle

.....This is a Thunder Power Jet, installed on a Mikuni VM Roundslide. You can see that it's referenced to the float bowl, which it where it draws the fuel from. After just over half throttle, the Thunderjet begins to add fuel.

I had an epiphany; instead of running the Thunderjet to the float bowl and supplying crappy 91 ocatane pump gas, why not just install a second Thunderjet that is referenced to a 50/50 water/meth reservoir!? It's so exceptionally simple, I think I'm going to throw a leather bag on the right side of the bike, drill/tap a hole into a Stainless Steel water bottle, add a vent, and plop it on the bike. Then all I'd need to do is install a second thunderjet into the carb and re-tune.......

I've done this same thing on air cooled VW engines. After adding turbocharging, the alcohol/H2O setup was added. Helped to control detonation (Yuma, Az after all ... hot hot hot).

[DrMotorcycle]

Originally Posted by Tomcatt

Sure you don't want un-equal length primary tubes so the exhaust pulses are more evenly spaced entering the collector?

Goal for the exhaust manifold is mainly to switch to a better merge design, that in and of itself is where more of the improvement is going to be IMO. Going from "log" style merge to a proper collector. Just trying to avoid the massive disparity in length from the previous manifold. As stated, I think that's why the front cylinder is so prone to detonation. I can pull timing on individual cylinders now so it's not as big of a concern.....but worth a shot.

I can order 180 degree u-bends for modestly cheap; the less weld joints it takes to get to the final setup, the better. Bringing the front cylinder down near the front of the cam cover and looping it back up via a u-bend is going to be the ticket I think.

[DrMotorcycle]

Before moving on to the smaller turbo/re-designed setup, I had to know; was the exhaust manifold design holding back the power?

So I re-fabricated it; Changed to a CNC "transition" flange, made a proper 2-1 merge collector w/exhaust pulses facing the turbo, which merged into a 2.25" diameter pipe right before entering the turbo. I also quickly added an external wastegate as I had one laying around, and they're just a much better way to control boost.

Result? It's quieter, and that's about it. Didn't really seem to impact anything positive or negative with regards to spool, power or response. Was pretty surprised by this, it was a let down after all that fabrication work.

Final revision setup is coming soon, it will incorporate everything I've learned about how the Evo Sportster responds to boost. Need to finish the Twin Turbo Virago build before whipping up the final kit that will be coming to market this year.

I'll keep 'yall posted.

[tussuck]

Good update. Two questions:
1. What drove the draw-through vs. blow through? I know that DT provides charge cooling due to the fuel mixture etc and that a lot of folks say you must run an Intercooler on BT (not that I ever used one and it did not seem to matter)
2. Oddly enough some aftermarket units support Boost - Thundermax for example, although it implies an EFI engine.

[sportsterpaul]

Thank you and good luck!

[DrMotorcycle]

Originally Posted by tussuck

Good update. Two questions:
1. What drove the draw-through vs. blow through? I know that DT provides charge cooling due to the fuel mixture etc and that a lot of folks say you must run an Intercooler on BT (not that I ever used one and it did not seem to matter)
2. Oddly enough some aftermarket units support Boost - Thundermax for example, although it implies an EFI engine.

I just don't like blow-through. If I'm going to go through the effort of putting a fuel pump and fuel pressure regulator on the thing, I might as well finish the job and go EFI. I did blow-through on a Twin Turbo Moto Guzzi and that was my first and last. Float stuck one day, fuel pump flooded the motor. Stranded.

Originally Posted by sportsterpaul

Thank you and good luck!

Thanks