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

[sportsterpaul]

Sounds exciting, anxiously await.

[DrMotorcycle]

Long story short, Billet wheel turbo didn't go as planned, as of right now it's on its way back for an inspection, and the sportster is back to sitting.....again.

I've been preparing my Virago Bobber and cleaning it up to get it ready to sell, and it's 95% of the way there. Just need to get a few small details squared away. Once that bike sells, the funds are going to go towards buying and testing a Genuine Garrett Turbo. I'm in talks with a a new turbo supplier that says they can convert the them for $250. The turbo's are $800 pre-tax, so after everything we're looking at $1,100 for just the turbo. Ouch.

That said, if it all works out, it's better for both the customer and myself if we have higher quality components. This sitting without a bike sucks, especially when I have a shortlist of "ready to buy now" prospective customers who are just waiting on me at this point.

Just a waiting game now.

[ChinCactus]

Two steps forward I guess. Gotten get it right before you sell.

[Steve9]

Yeh
Good you are getting everything sot before selling that cool setup

[sportsterpaul]

The “good things” in life are worth waiting for. You efforts speak volumes towards your integrity and what is to become the final product, we thank you.

[DrMotorcycle]

Originally Posted by ChinCactus

Two steps forward I guess. Gotten get it right before you sell.

For sure.

Originally Posted by Steve9

Yeh
Good you are getting everything sot before selling that cool setup

Thanks, yeah it's been a long time coming.

Originally Posted by sportsterpaul

The “good things” in life are worth waiting for. You efforts speak volumes towards your integrity and what is to become the final product, we thank you.

Thanks Paul.

[DrMotorcycle]

Well the Virago sold quickly as I had it listed very low, so I'm thankful to have the cash from that right now. The Development of the Sportster Turbo kit has me spread pretty thin; fully planned on being ready to sell late last year, and here we are already halfway through 2023! Insanity.

Currently have a few side projects in the shop right now; the guy who bought my virago had a non-running Yamaha WR426 he wanted to get going so I'm slamming that bike out right now, then moving on to get my Turbo KZ650 back on the road so I can sell it.

Need to wait until I get paid on the 21st of this month to order the new Garrett Turbo, and the new supplier says it's a 2 week lead time, so we're looking at early July before she's back on the road, and then I'm just going to have to bang out some miles on the old girl, get some dyno numbers, and button up the technical/installation side of things and we'll be ready.

So close I can taste it!

[DrMotorcycle]

That's the new turbo before tax and shipping, so we're looking at $1,400 for just the turbo alone now vs. $250 that I had in the china turbo's after the carbon seal conversion.

New turbo supplier just let me know that they CAN'T convert the small GT15 sized Garrett Equivalent turbo to carbon seal like they said they could. So we're stuck with the T25 hotside turbo which is a massive letdown. Really loved the punchy midrange power of the GT15 turbo, it spooled so fast and just really had that "hit". I don't even know if I want to go back to the larger frame turbo it sucked so much. The next size up that they can convert is still a fair amount smaller than the original T-28....but it's closer than it is further if that makes sense, unlike the GT-15.

Price of Argon has gone up 25% since the last time I filled up, so there's another $50-75 per kit too, and the price of really everything in the kit has gone way up since I started development.

I don't know what to do at this point.

[sportsterpaul]

Sleep on it clarity comes in the morning………

[DrMotorcycle]

Spent more time thinking about this and really doing a deep dive on the specs of the original T28 turbo I used, the Current GT15, and the GBC17-250 that is the current possible alternative.

Original T28 was a .6 A/R compressor, 43/60mm compressor wheel, .64 A/R turbine 53/46 turbine wheel.

GT15 that was on Version 2.0 .35 A/R compressor, 36/49mm comp wheel, .35 A/R turbine 35/41 Turbine wheel.

The Genuine Garrett GBC .52 Compressor A/R, 36/49mm comrpessor wheel, .5 A/R turbine housing 44/40 turbine wheel.

A/R, or "Area over Radius" essentially refers to the size of the volute in relation to it's radius. A larger numerical number increases HP capability but also results in more lag. Turbine A/R has the largest effect on spool, followed by the size of the compressor/turbine wheels.

As we can see from the specs, the Garrett GBC unit is actually closer to the GT15 than I originally thought, even sharing the exact same size compressor wheel. The turbine wheel is slightly larger on the GBC, and the Turbine housing is quite a bit bigger (.5 vs. .35). Not only is it bigger, it's also a larger frame turbo, so there's no way around the fact that we're going to lose some response in exchange for more power.

One of the things I'm going to try in order to recover some spool is to switch to smaller diameter primary tube. This has the side benefit of helping free up a bit of room that we're losing to the bigger frame of the GBC turbo.

The last thing is the physical size of the turbo itself, which other than what I just mentioned.....there's not much else we can reasonably do. I don't see a way this would work with forward controls at all now. The turbo is just so much larger on the turbine side in comparison to the GT15. New turbo supplier said they can machine the housing so that we can go to v-band mount, which could maybe buy us an inch if we're lucky. Moving the right footpeg out might be an option but the turbine would be right next to your leg....far from ideal.

Any thoughts I'm all ears.