Turbo or supercharged 2Ts?

**FastFred** · 28th January 2015, 13:38

Originally Posted by breezy

Hey I think that was TeeZee at Taumarunui, he said his bike farted all the way around the track ....

**ken seeber** · 29th January 2015, 00:11

The dude in the video explaining how the supercharging of crankcase scavenged 2 strokes is basically correct. However, there can be benefits in that the potential greater throughput of fresh mixture can assist in achieving a greater mass of fresh charge (displacing any combusted gas) at the time of exh closure. However (again) this must be offset by the power loss to drive the supercharger.
The situation is different with a turbocharger. In this case, the exhaust gases drive the turbocharger, incurring an overall pressure rise in the exhaust upstream of the turbo. All thing being equal, this can result in a charge density at the time of exh closure being much greater that what is normally experienced. Lots of factors to consider in this as well though, eg crankcase pumping capacity. So, more mass of mixture to be combusted means more power. Just google turbo 2 strokes, eg snowmobiles and it can be seen that this is the case.
Dunno what this might mean in terms of Bucket rules rewrites, but is a consideration.

Long live 2 strokes though!

**ken seeber** · 29th January 2015, 05:53

Further to this though, I suppose that one could artificially increase the back pressure of the exhaust of the supercharged engine (by say a smaller tailpipe) to raise the overall system pressure. This would lead to a higher level of trapped charge mass at the time of exh port closure.
Lots of things to try.

**turbokemi** · 30th January 2015, 06:34

I know this is a bit off topic, but I have a turbocharged 2stroke snowmobile, it's a skidoo 2004 800cc twin, works great, I run on 98 octane pumpgas and have 170 hp, original hp is 130 hp, I'm now wating for a new head with a bit lower compression so I can run on higher boost, now I'm running on 0,5 bars on pumpgas and 0,9 on race fuel, it's a rotax 800 engine, stock engine with forged pistons

**FastFred** · 30th January 2015, 06:52

Originally Posted by turbokemi

I have a turbocharged 2stroke snowmobile, it's a skidoo 2004 800cc twin, works great, I run on 98 octane pumpgas and have 170 hp, original hp is 130 hp, I'm now wating for a new head with a bit lowe compression so I can run on higher boost, now I'm running on 0,5 bars on pumpgas and 0,9 on race fuel, it's a rotax 800 engine, stock engine with forged pistons

That is very interesting, especially some idea of the boost pressures. I cant see your attached image but we would love to know more.

**turbokemi** · 30th January 2015, 08:02

here is my test video, it was running a bit to rich in this video, but I have re jetted it now, and it runs smooth, more videos are coming

**turbokemi** · 30th January 2015, 08:05

and there will come more videos of 2 stroke and 4 stroke projekts on my youtube channel

**turbokemi** · 30th January 2015, 08:12

[IMG]D:\bilder\ailo_kemi on Instagram_files\turbo rev.jpg[/IMG]

**turbokemi** · 30th January 2015, 08:40

Originally Posted by Sketchy_Racer

Here's one to wet your appetite TZ

I have turbocharged 2 stroke engines, seems to work creat!

**FastFred** · 30th January 2015, 08:44

Originally Posted by turbokemi

- here is my test video, it was running a bit to rich in this video, but I have re jetted it now, and it runs smooth, more videos are coming

Great to see the video clip complete with turbo pressure blowoff squeek when you close the throttle.

Was there much involved in installing the turbo? did you have to modify the exhaust pipe much?

Not much snow here for snow sleds but very interested in two strokes and what can be done with them and I think the technology being developed for snow sleds now may be what revives big capacity 2T road bikes in the future.

**koba** · 30th January 2015, 09:27

[QUOTE=turbokemi;1130824142here is my test video, it was running a bit to rich in this video, but I have re jetted it now, and it runs smooth, more videos are coming[/QUOTE]

Did anyone else see this as a scary skull thing before the video plays?
Like a snow version of these guys...

**turbokemi** · 30th January 2015, 16:37

Originally Posted by FastFred

Great to see the video clip complete with turbo pressure blowoff squeek when you close the throttle.

Was there much involved in installing the turbo? did you have to modify the exhaust pipe much?

Not much snow here for snow sleds but very interested in two strokes and what can be done with them and I think the technology being developed for snow sleds now may be what revives big capacity 2T road bikes in the future.

No mods on exhaust or port timing,I just deleted the silencer and welded turbo french on the pipe and added more springs between the engine and the pipe to hold it in place when the boost hits, I can take some photos when I go for riding, I'm waiting for a new turbo domes for my rktek billet head so I can run on higher boost on pump gas, actually it's quite simple to turbo charge a 2 stroke carburetor engine, I changed the vacuum fuel pump with a walbro electric pump because when you boost a 2 stroke the vacuum disappear in the crank case and you need a fuel pressure regulator that will increase the fuel pressure when the boost hits, and you have to pressurize the fuel float with boost, I can explain with a video or some pictures, and I had to change the reeds to turbo reeds that can handle more flexing, I actually did go down on the main jets from 400 to 360, and added adjustable power jets so I can rich or lean the fuel mix on the run when the temperature changes or the altitude

**turbokemi** · 30th January 2015, 16:54

The thing when you turbocharge a 2 stroke is that you need a bigger turbo then in a 4 stroke, like I use a garrett gt2860rs turbo, on a car this turbo is suitable from 1,5 liters to 2,5 liters, have a potential to make 350 hp, on a 2 stroke 800cc this is the smallest turbo you can use and the limit for the turbo is 250hp on 800cc twin 2 stroke, if more power is wanted then gt 2871 or a gt30 turbo is the way to go, and a ballbearing turbo is to recommend, they need less oil pressure and spool twice as fast up then a standard journal bearing, I had a journal bearing turbo at first, but it sucked, I had to use a big oil pump that draws a lot of amps to run, and my stator was working on the limit, so I bought a boondocker turbokit oil pump, small, low amp draw and just enough oil pressure to use on a ballbearing turbo, boondocker developed this pump to use on 2 stroke turbo systems

**TZ350** · 30th January 2015, 17:15

Thanks for that, the info is very helpful, there are a few of us here interested in trying a turbo, but our engines are much smaller than yours, the principle is the same I guess, just smaller.