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GX200 Turbo project

NewbCarter

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Sorry everyone for the lack of progress , mainly due to college , now its the coronavirus stuff , Croatia is on lockdown , meaning nothing but the essential shops are open .

I havent really worked on the turbo project at all , mainly since i took the chance of the little free time i had to work on the Rondo project , got the thing running properly finally with a new HL360 carby , hit close to 13k RPM , which by the cartcalc app is around 75-80km/h . I have a second SH frame to work on too , and an engine to fix up .. so the turbo project is in parallel with that .

I did however think about getting a pressure-washer pump , and building a DIY load-tester since im pretty sure with no load only boost im going to see is me hitting the thing with a hammer... soo .. will see
 

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Finally some work done. Experimental setup, to see if turbo would even spool. Engine is giving me trouble tho, seems to be backfiring, for no apparent reason.
 

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NewbCarter

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After some investigating.. The culprit was the sparkplug. Changed it out, retuned the carb and it sprung to life. The factory exhaust manifold however, didnt like the additonal heat, and weight bouncing around.

After a couple of minutes running, it broke around the stock weld seam.

Tho for results, the turbo seemed to spool up, tho without the compressor side hooked up to anything, this doesnt mean much. I supplied oil via the gear pump, i still need to figure out a mount, pulleys and belt for it.
Oiling looked decent, especially when the turbo heated up.
 

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NewbCarter

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So far , its interesting.. to say the least .

A youtuber i check on from time to time , did a draw-through setup with the same turbo on a 670 predator V-twin .. His claims were that it was too restrictive .. and soon the turbo blew its guts out due to overspeeding apparently .

Lot of conflicting data aswell .. Well , one way to find out i guess.
 

karl

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So far , its interesting.. to say the least .

A youtuber i check on from time to time , did a draw-through setup with the same turbo on a 670 predator V-twin .. His claims were that it was too restrictive .. and soon the turbo blew its guts out due to overspeeding apparently .

Lot of conflicting data aswell .. Well , one way to find out i guess.

I dont think you will run into that issue, at least with a gx200.

I put about half a dozen hours on the kohler command 624cc v-twin with the same turbo, stock wastegate, draw through, I think 10psi. Engine still runs great.

https://youtu.be/TA_dkRjER70

I did however swap the engine for a N/A command , 674cc, and its does not have near the pep the turbo engine did, but still plenty for my needs :p It simply destroyed the lawn before.

Cant wait to see it make some boost! Im sure it can be done. you'll get there.
 

NewbCarter

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I dont think you will run into that issue, at least with a gx200.

I put about half a dozen hours on the kohler command 624cc v-twin with the same turbo, stock wastegate, draw through, I think 10psi. Engine still runs great.

https://youtu.be/TA_dkRjER70

I did however swap the engine for a N/A command , 674cc, and its does not have near the pep the turbo engine did, but still plenty for my needs :p It simply destroyed the lawn before.

Cant wait to see it make some boost! Im sure it can be done. you'll get there.

Oh , no doubts it probably will boost a bit , afterall im not expecting much . Just commenting that alot of the info iv been searching makes no sense .

As far as i know , these are used in Kei-class cars in Japan , so 47kW limit . Id say a three cylinder 660cc car engine flows quite a bit more than a predator V-twin .

Iv also been planning a small change in the oiling department ... but will see when it comes to that .
 

65ShelbyClone

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Oh , no doubts it probably will boost a bit , afterall im not expecting much . Just commenting that alot of the info iv been searching makes no sense.

Anything specifically?

As far as i know , these are used in Kei-class cars in Japan , so 47kW limit . Id say a three cylinder 660cc car engine flows quite a bit more than a predator V-twin.

That's true, which is why I don't believe the overspeed hypothesis here:

A youtuber i check on from time to time , did a draw-through setup with the same turbo on a 670 predator V-twin .. His claims were that it was too restrictive .. and soon the turbo blew its guts out due to overspeeding apparently .

The kei cars you mentied have engines of 600-660cc and three times the power (~60-66hp) of a 670 Predator, so restriction was not the issue. His VZ21 was probably a cheap counterfeit, installed improperly, used improperly, or all the above.
 

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Anything specifically?

Well , mostly the turbo data / compressor maps . The alliexpress ad. stated it should be ran between 7-11psi , with no exceeding 12psi , otherwise its lifespan is "drastically reduced" . Even tho the stock wastegate almost fully opens at 7psi . (.5 something bar ) .

If you go by the "general" data sheets , this thing should be good for gasoline engines between 27-123 or so HP . So okay ... and then you look at the max flow rate , and its again , a rather wide range for such a small unit . .63 cubic meters of air per minute ... to something like 6 cubic meters per minute. Fun fact my Renault Twingos 1,2L engine at the redline of 6500RPM displaces 3.15 cubic meters of air per minute !

So , mostly where im going with this is that the data is fishy , bear in mind im no turbo expert , far from it . Just that some of the data is kinda hard to put in perspective considering other factors ...
 

65ShelbyClone

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Oh, yeah, all that kind of stuff.

First and foremost, don't believe anything you see in the ad from a Chinese turbo bootlegger. It's half misinformation and the rest lies.

Also try to think in mass airflow whenever possible; volumetric airflow just muddies the water IMO.

Part of the problem is that IHI never released a proper compressor map. The most believable one I can find is on the left below.

It looks like it may have actually originated from IHI. The flow axis is in units of mass. When I convert the middle flow island to lbs/min, it comes out to a believable 6.6lbs/min or roughly 66hp at 10psi. That's right in line with stock kei car output.

The "map" you'll see most is this colorful one on the right and it actually is from IHI, but notice that it's for an RHF3, not an RHB3. The RHF series is more modern and higher performance. There is no way an RHB3 would support 25psi and 150hp like that map shows.
 

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NewbCarter

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I did some math with advice from @65ShelbyClone , and if i did it correctly , the red dot on the graph is where the Chonda engine sits ... not too promising .

Data i used : 212cc engine capacity , 80% VE , 4500RPM , the planned horsepower is 10HP which at the ideal 14.7:1 ratio and with the air at 28C , 15% humidity and 0m above sea level (1013hPa) gives 0.00825 KG/s of air . Pressure ratio ended up being 1,11 ( Boosted L/min / N/A L/min )Inkedrhb31_LI.jpg
 

65ShelbyClone

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I did some math with advice from @65ShelbyClone , and if i did it correctly , the red dot on the graph is where the Chonda engine sits ... not too promising .

Data i used : 212cc engine capacity , 80% VE , 4500RPM , the planned horsepower is 10HP which at the ideal 14.7:1 ratio and with the air at 28C , 15% humidity and 0m above sea level (1013hPa) gives 0.00825 KG/s of air . Pressure ratio ended up being 1,11 ( Boosted L/min / N/A L/min )

Your plot on the compressor map looks correct. That's the main difficulty with turbocharging these small engines; even the smallest turbos are a bit too large. You can get the airflow and boost up without making more power by using a more boost-friendly AFR in the 10.8-11.5 range, but it probably won't make a huge difference.

Is 10hp all that you're trying to get?
 

NewbCarter

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Your plot on the compressor map looks correct. That's the main difficulty with turbocharging these small engines; even the smallest turbos are a bit too large. You can get the airflow and boost up without making more power by using a more boost-friendly AFR in the 10.8-11.5 range, but it probably won't make a huge difference.

Is 10hp all that you're trying to get?
Im keeping the engine bone stock, so yes. Since i have some 2stroke engines in plans, this thing will probably be returned to N/A after im done, and the turbo will be used for testing on a different project.

Plan was to use this as a basis for a minibike, but probably will use a 2stroke.
 

65ShelbyClone

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It'll probably still make boost though. Warped Perception was able to get 3-4psi on a much smaller engine making 6-7hp with that boost. Your engine should easily make that much power as a baseline.

 
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VC10786

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Any updates? I am running a very similar setup on my kart. GX140 with VZ21/RHB31 turbo. Was piped up to stock carb but had difficulty with tuning so I ordered a VM22 Mikuni carb. Is running a fuel pump + regulator required on a draw-through system? Trying to figure out if I need to have fuel pressure rise proportionally to intake pressure, or if the engine will simply suck the fuel through the jets adequately despite the turbo if I have the right carb/jet size. Input appreciated, thx.
 

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