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

[DrMotorcycle]

Originally Posted by Nibelungen

Interesting... midrange monster...
a question.... why not to fit her with a proper exhaust?

Fair question, I actually have a few exhaust ideas in my head, one a "traditional bobber" style, the other a more cafe style w/reverse cone muffler. Just want to ride the new setup for a bit before going back into fabrication again.

Originally Posted by brucstoudt

^^^ ''proper'' rules don't apply with forced induction.

[DrMotorcycle]

Made a new exhaust, it probably wouldn't work with forwards, that's one thing I need to buy and mock up on my bike to check. The new exhaust surprisingly made it much quieter, I actually prefer it this way. You can get on the gas and not wake the dead like an N/A straight pipe Harley. You can hear intake induction noises when rev-matching, due to the plenum I think. Hearing a combination of induction noises and turbo noises is the best of both worlds!

I've got the bike where you can start it cold, hop on and go. I'm going to be testing out smaller plenums over the next couple of months to see how it responds, and also getting the bike on the dyno to see where it's at. Once I have dyno numbers and some concrete data on plenums, we'll be only a few weeks away from going into production.

2-step launch control is on the bike, I have it set to 3,100RPM. Hold it on the launch limiter for even just a second or two and it builds 3psi instantly; let the clutch out and it swings to full boost and takes off like a bat outta hell. Going to recommend this for very experienced riders/drag racers only. I'll wire in the pin on the ECU so that the end user can wire it up to a N/O switch. The circuit is activated via ground; right now I'm just using a bar-mounted killswitch.

Final note; For some reason, the 04-06 bikes are extremely popular for hot-rodding, and 3 out of 4 people that hit me up have one. The ignition setup on those bikes is triggered by the crank, and not adjustable like the nosecone setups. Additionally, Harley tied the ECU in with other electrical systems on the bike, so I can't use my supplier for the ignition system. The only options are the Dyna DSPT-1 (which has pre-programmed curves, but to my knowledge, cannot have custom curves programmed) and the Daytona Twin-Tec, which does allow custom programmed curves.

The issue is, even though I can program curves, it's MAP based using the stock MAP sensor, and I don't know how it will respond to boost. More than likely the sensor will just run out of range, but that remains to be seen. I might be able to adapt a different map sensor, but I don't know if the Programming Software (that I'll have to buy) has cells for pressure higher than ambient. If it doesn't, that's a huge bummer.

Then add in the fact that the 04+ bikes have 9.7:1 comp in addition to the super early closing W cam, and I'm hesitant to offer setups for those bikes without actually testing and tuning one myself.

Might have to call Daytona and probe a few questions before seeing if I can find someone who's willing to make the trip to AZ for me to make them a turbo setup for an 04-06 bike. I'd offer you a huge ($1k off) discount and free install, but I'd need the bike for 3 weeks/month to get a reliable timing map in the bike.

Because of this, I'm sticking with my original intention of only offering my kits for the 86/03 bikes, at least until I can get some questions answered, and some miles put on a newer bike. Might have to just buy a rubber mount myself......

[Nibelungen]

it seems a good work
by the way
it's not stuff for forwards imo

[DrMotorcycle]

Originally Posted by Nibelungen

it seems a good work
by the way
it's not stuff for forwards imo

Maybe not this exact setup (it still isn't ready yet), but this is good feedback. So thanks. I agree with you btw, this current setup would not work with forwards, and it didn't really occur to me until it was actually on the bike and I sat on it.

Still work to do for sure.

[DrMotorcycle]

Just wanted to drop in and say, the sportster is still alive and well, and I'm still riding the bike just about every day, usually at least 30 miles/day and the occasional trip to my favorite riding spot to hit some twisties; those are 120 mile days.

Here's a link to a video I shot about a month ago on a beautiful afternoon. As stated in the video, the bike is on a conservative tune, very soft timing map, rich fueling, there's at least 10hp left in it with less fuel and more timing. I've heard some people say they don't like turbo's because they're worried about it "kicking in" when they don't expect it or something to that effect.....that's not how it works. The boost is entirely dependent on throttle position. More throttle = more boost. Cheers!

https://www.youtube.com/watch?v=E3uhaeMqjqQ&t=1s

[sportsterpaul]

Thanks for sharing, keep it safe!

[ChinCactus]

She sounds great! Nice Video.

[Iron Mike]

Nice work

Bartlett lake road,… one of my favorite Sunday evening rides. Everyone is gone by then.

[DrMotorcycle]

Minor Update -

I'm in talks with my turbo supplier about upgrading the turbo to a Billet Compressor wheel, which is going to be standard on the kits from here on out. Since they already have the turbo and the bike is going to be down anyway, I figured since we're already going to have to machine the turbo housing to accept the billet wheel....might as well look into going just a little bigger on the compressor wheel to pick up another 5-7hp on the same boost level.

Also;

Strongly considering just going with a Genuine Garrett GBC 14-200 at this point, rather than buying the eBay turbo's and having all the work done. The Garrett's already have Billet compressor Wheel's as standard (GTX Gen II wheel's; as good as it gets) and even have inconel turbine wheel's. Very high quality.

Thing with that is, a Garrett GBC turbo, after carbon seal conversion ($250) and tax/shipping, is going to be over $1k, which is over double what I have in the eBay turbo. Leaning towards going with the Garrett and splitting the difference and accepting a little less profitability in order to have a Genuine, Made in the USA turbo. Just seems like the right thing to do, considering these are American made Motorcycles.

I'll eat some of the cost, and so long as my other input costs don't keep going up at an alarming rate like they have been, I still think we'll be under the 4k mark.

Thoughts?

[DrMotorcycle]

Okay, Billet compressor wheel was added by my turbo source, we went also went bigger; from a 36/48mm stock cast wheel to a 39/51MM billet wheel, which according to them, should be worth 20whp on a maxed out setup (i.e. 20+psi). We're still using the GT15 frame turbo with the small hotside, so the spool should be very similar to what it was before, but with more power. I'm prepared to lose a bit of spool if it means we can pick up 5-10whp on the same boost level. This is one of the last things I wanted to get sorted before going to the dyno.

Based off how the bike feels seat of the pants, the torque is going to come in hard and early, hold steady to about 4,800 or so, and then start dropping, where the HP will take over and build to about 5,800 or so and then start rolling over. It's going to mirror the power delivery of the D cam, just with a lot more everywhere. Unlike the larger frame T25 hotside turbo's that everyone seems to use that take forever to hit peak torque, the GT15 turbo hits like an electric motor, and only gives up when the camshaft does.

The turbo should be here early next week, and it's going to take a little bit of tuning to get it where I want it before going to the dyno. Would really like to see this bike crack the 100whp mark, but that depends on a lot of factors obviously. I'm running 18 degrees of total advance peak, and 9psi of boost for the dyno run. More than likely it won't crack 100whp on that low of a timing setting, but this is the "you can run it in the Arizona heat" setting. Just know there's a ton of power left on the table.

Can't wait to test out this finalized setup! Once we have dyno numbers and I put another couple thousand miles on the kit, it's ready for production. Possibly in time for fourth of July?

See you soon folks.

-Jimmy