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

[DrMotorcycle]

EXCITING NEWS!

I was under the impression this whole time that Garrett no longer made the GT15 as it isn't listed on their website. Turns out, they do in fact still manufacture it, and there's multiple different websites that you can purchase it from. I'm able to source these turbo's brand new for $600! So stoked about this. More than likely I'm going to have 2 different options for the turbo; you can either go with a Genuine Garrett core, or you can go with an eBay core.

Either way, the turbo's will be converted to carbon seal, and then be machined to accept a billet wheel, and then re-balanced. So regardless of which route you go, you'll have a Billet Wheel turbo that can support 150+rwhp on higher boost. These turbo's have 360 degree thrust bearings and will be balanced to specs exceeding the industry standard.

Speaking of HP, the last thing we need to answer before coming to market is how much power this makes, so my sportster will be going on the dyno to get some numbers. Not to caveat this to death, which I feel people often do with dyno numbers; It's been 111* during the day here in Arizona, the air is nasty. I don't even have 20* of timing in the bike right now, and the AFR's dip into the 10's and then settle in the mid 11's at WOT. So keep that in mind when I post the dyno sheet.

We're back on track to release the kit before summer is over.

Cheers!

[DrMotorcycle]

Quick Update; Switched to a 3" downpipe on the Sportster and I'm pleased to say it cured a couple of issues that in my mind were unrelated. Additionally, I'm going to make one final tweak to the plenum that I think will pick up an additional 5HP or so before finally going to the dyno to get some numbers. Shooting for Late August/Early September timeframe at this time. It's getting the last 10% out of the setup that's going to separate this kit from the inevitable copy-cat kits that I know are going to hit the market eventually.

The development of this turbo kit represents 18 months of my life that I dedicated to making the best draw-thru turbo setup I possibly could for the Harley Sportster. 6 (or was it 7?) revisions of the first turbo setup, a complete clean sheet re-design, and an additional 3 more revisions to end up with the final design. So many obstacles, so many hours in the garage spilling gas on my hands, pulling my hair out chasing driveabilty and response, 100's of instrumented WOT pulls, over 10,000 street miles, all to FINALLY end up at a point where I can honestly say; there's really not much more I can do to improve this kit.

See you soon!

[ChinCactus]

She looks mean!

[84rzv500r]

yes been following this! the packaging has improved greatly... no more intrusive than he stock exhaust or the 38 flat slides and K&N's on my XR...

[DrMotorcycle]

Originally Posted by ChinCactus

She looks mean!

Thanks!

Originally Posted by 84rzv500r

yes been following this! the packaging has improved greatly... no more intrusive than he stock exhaust or the 38 flat slides and K&N's on my XR...

Thanks, yeah it's come a long way. You can touch your knee's to the tank and not hit anything on both sides. Other than the carb taking up a little room you barely notice it's on there.

I actually just acquired an Ironhead, once I bang out my KZ650 Turbo build and also the Twin Turbo EFI GS400 Dune Bike (lofty project; 100HP, 400CC, Long Travel/paddle tire Mad Max dune machine), I'm building that bike, and turbo kit testing will begin for Ironhead Sportsters.

Should have a kit for the Ironheads out around this time (possibly earlier) next year. Then it will finally be time to tackle the FI sportster's.

[DrMotorcycle]

Quickshifter works! I'm not going to call it a "quickshifter", I think a WOT Shifter or drag shifter would be more appropriate. I'm using a rear brake light switch to close the circuit on the ECU. The blackbox ECU's that will be coming with my turbo kit have a specific quickshift function that allow me to adjust the killtime. Spent a lot of time on this, playing around with different kill times and finally settled on something that works consistently.


This is going to be an option for those of you who have more drag oriented bikes, and because of the way it operates, my recommendation would be to use it only for higher throttle positions and above 3,500RPM or so. You really need more killtime down low and less up higher, and same goes for being in higher gears. So you have to compromise a bit with the killtime and optimize it for a certain RPM range. The way I will be sending it to the customer, it will be optimized for Wide-Open, Full throttle shifts at High RPM. I've been consistently banging the gears (including the 1-2 shift), Full throttle, no clutch staying at full boost and just clicking off gears, it's really fun. Beats the hell out of chopping the throttle!


As far as the rest of the kit, I feel comfortable saying the GT15 Kit is ready for production. The order books will be open on my website (www.doctor-motorcycle.com) as soon as I get my turbo's back from the shop that does the carbon seal conversions. They typically have a 2-3 week lead time, so we're very close! I'm going to be building these turbo kits in runs of 3, to prevent myself from being too overwhelmed in the beginning, and they will be sold in a first come, first serve manner. I have a shortlist of people that are interested; if you'd like to be added to the shortlist to be e-mailed 24 hours before the kits are live on the website, please send me a message.

Also, I will be making a separate big turbo kit for those of you that have cams/headwork that want a lower backpressure, more power focused turbo setup that will work with cams that have 40* or more of overlap. One of the last things I need to do (that I've been putting off forever, lol) is weld a bung onto the exhaust manifold of the Current GT15 turbo setup and run some bundy tubing from it to a boost gauge, and compare the backpressure to boost ratio. I suspect that on low boost (12psi and less), even the GT15 will work just fine with aftermarket cams, but I need to verify first before going out on a limb and saying that.

Methanol injection setup is in the works too, just need to move a few kits first.

See you soon folks!

[Tomcatt]

Originally Posted by DrMotorcycle

... I'm going to make one final tweak to the plenum that I think will pick up an additional 5HP or so before finally going to the dyno to get some numbers...

Results???

[DrMotorcycle]

Originally Posted by Tomcatt

Results???

Haven't gone to the dyno yet, will post numbers when I have them. Everytime I call the shop the dyno is taken, they only do pulls from 7-9am, after that it's too hot.

[DrMotorcycle]

This is the kit in it's final form. I wanted to make one last update to this thread before hitting the dyno next week. Pre-production kit will be listed on my website after the product launch before year end. As you can see, there's no exact date - The EFI, Twin Turbo, Intercooled GS400 build we took on needs to be done before the kit is available....or it's never going to get done. We're doing a complete, in-depth walk-through of how to convert a motorcycle to EFI, which to put plainly...it's been a massive undertaking, and I've been redlining myself since the build started, as you often do when you're pushing the boundaries of your skillset. I need to keep my sanity too, hence the lack of a definite date.

Pre-production kit - It won't be as polished as the final kit. Things like custom packaging, custom booklets, and some minor stuff that I'm going to forget. Going to focus heavily on feedback from the initial handful of customers. Nothing is set in stone at this stage - If something obviously needs to change based off feedback, we can do that. In fact, the more nuanced the feedback is, the better.

Speaking of nuance;

Recently found myself going down the rabbit hole again tinkering on the Shop Sportster, and made an additional 2 plenums and A-B tested them. So this is the 5th plenum on the version 2.0 setup (lol). Suffice to say, the plenum that's on it is a noticeable improvement over the old one, and the bike is running the best it ever has. THIS is how I expected the bike to pull 2 years ago during the initial build, THIS is how people expect a turbo sportster to ride. TORQUE. Midrange Punch, and it keeps pulling until the stock D cam has left the party. 6,300-6,400 it's time to grab another gear. Rev limiter is set at 7k btw, which I suggest you avoid on stock springs.

So how it appears in these photo's is exactly the final setup. The tune-up in it now is the ultra conservative, 20* peak timing tune with REALLY rich AFR's at WOT. There's 10-15whp left in this tune-up if you wanted to get aggressive on the timing and also lean it out. Though I'd recommend to save that type of tune up for the track only. Running the bike to the ragged edge is up to you, just know that when you start advancing the timing and chasing that last little bit, the margin of error goes from broad to very thin.

The main reason for this last little update; I've acquired a set of cams that I'm going to A-B test. It won't be done the same day, but the conditions will be very similar. As for what cams they are/specs; they aren't bolt-in, they have a significant amount of overlap, and a LOT more duration than the stock D cam. They are the exact opposite of the conventional "turbo cam", and more along the lines of a "hot street" grind. In fact, by most conventional turbo wisdom....it should be all wrong. Maybe. We'll see.

[DrMotorcycle]

https://i.postimg.cc/VvzHr4BP/20231108-145518.jpg

Thank you to Jeremy at Adrenaline Performance in Mesa, Arizona. He got me in for a dyno run with a 2 hour notice. This was after calling 5 different shops with dyno's who either outright refused ("we don't TOUCH bikes older than 2006" ), or "yeah it's $400 an hour, we don't do numbers only".

Before we get into this; please note the valvesprings losing control of the valvetrain at 6,400. With a D cam, I wouldn't expect it to continue gaining that much more power, but it's worth noting. I think we could've maybe cracked 90whp if the valves didn't float. The pulls were done in 4th gear as well, which from what I can surmise means the numbers will be lower by around 5%.

The result above is the "out-of-the-box" tune with 22* of ignition advance, 9psi, The AFR's (he's going to send me the graph) dipped into the low 11's on this pull.

Unfortunately, I only purchased a "numbers only" dyno pull, not a full on dyno tune that would allow me to really fine tune the bike and squeeze out everything we can from it. I think an additional 2-3 degrees of advance alone would've got us to 90/90 or more @62-6300.......on an otherwise stock rigid 1200 motor w/stock D cam. Hell, running the bike in 5th gear probably would've put us at 90whp in and of itself.

Really, really would have liked to advance the timing a bit more as there's enough left on the table to do so, especially given that I'm still running the same timing map I ran in the bike when it was 110* out. If you wanted to get aggressive with the timing and run 25-26 degree's, and then dyno the bike in 5th....it will hit the magical 100whp.

Even though this may disappoint some of you, I actually came away pretty happy today. These bikes are factory rated at 50HP, and we just put down 85whp on the first stab of an out-the-box setup. I'm tossing around the idea of going back to the dyno, requesting that it be dyno'd in 5th, and then adding 2 degree's of advance and leaning out the thunderjet a half turn. I think that alone will take us well into the 90/90 area, and may even flirt with 100whp even with the floating valves.

More than likely going to go back one more time before the kit goes into production, just to at least get a 9Xwhp run on the board before starting the advertising for the kit. Being in the mid 80's will seem underwhelming without having context of everything, so in the meantime, I'm just going to send a link to this thread so people can get the context with the numbers.

I'm currently offering pre-production kits to anyone who can drop their bike off at my home shop to have the kit installed and tuned. This way I can give you a proper, dialed in setup (tuned with my wideband) to maximize power and safety. PM me if you're interested.

Cheers!

P.S. Special thanks to those of you who've encouraged me over the years (it's been that long!) since the development began. There were many issues I ran into during the development, some of which aren't talked about on here, that I thought for sure would be insurmountable. And at times, I seriously considered just giving up and moving on.....so glad to have stayed the course, and that wouldn't have been the case had it not been for many of you providing words of encouragement (SportsterPaul, IronMike, Steve9 and ChinCactus come to mind). XLForum will always have a special place in my heart, in large part due to the Elder Memebers who've been around for a long time providing encouragement and feedback. Can't think of another forum that reminds me of the golden era of internet forums (mid late 00's) more than this one. So thank you!