Turbocharging carburated motorbike engine.

[SPARKY]

great stuff guys!!!!!!!!!!!!

[Friday1]

I don't think you need a plenum that is 2X the displacement size unless you are running a "blow through" system. The plenum on blow through is to lessen surges. On a suck through system (I think you said you were doing a suck-through system) you could use a THUNDER JET system. It is popular with S & S carbed Harley dragbikes. I am not sure there is enough vacuum in a small single cylinder application for suck through turbo, but it is a great starting place for a design for a smaller motor THUNDER JET. It allows extra fuel at midrange RPM and gives an S & S carb a third fuel circuit. Hope this helps, Friday

[moirmyster]

Hey guys havnt been on site for a while,as i lost interest in project.
thanks for all your input some great ideas.
I got motivated again and this is where im up to.Ok if fixed the over heating problem hooked up a oil cooler seems to work fine.On pump gas it runs mint as.
I am in the prosses of running on methanol it goes really well on it runs alot colder and keeps the air intake ice cold,it goes awsom on the mainjet,but im finding it real hard to tune it on the pilot jet.soon as gets off the gas and wind it on again it bogs really bad.Iv tried smaller jets to huge jets,seems little beter with big jets.
Im running a 1.5mm pilot jet and a 3.2mm main jet.
I was thinking part of the problem is u need alot of compression to make methanol work well.As my engine is only 8:1 compresion ratio.
It doesnt make any boost on the pilot jet.but on the main it makes lots off boost it increases the compression ratio maybe that why it runs fine on the main jet,does this theory sound correct.
I tried running on methanol with no turbo ran like a peace of junk was worse.
All so why would i have to run a spark plug 2 steps colder
some one may hav a idea.

 

[Boostedballs]

It sounds to me like it wants more timing.

[moirmyster]

It sounds to me like it wants more timing.

So in guessing u mean needs to be advanced or retarded?

[Boostedballs]

More advance. With the lower compression and alky, you should be running lots of timing. You might have stepped your plugs colder because they appeared a little white or did they have melted electrodes? Too much retard can make the engine run too hot and make the plugs run too hot as well.

A large plenum is a good idea on blow-throughs and sometimes draw-throughs. In a draw-through, too big of a plenum will create fuel drop-out and too little will cause compressor surge. Both hurt performance. If you must run a draw-through, I would match the plenum to the cam. Try to make it "adjustable" by making it too long at first and connect the pieces with rubber hose. Then you can trim one piece a little each time until the power starts to fade in the RPM range you want. Then space the two sections to make up for half of the last cut. Make sure to adjust the jets at each test.

Also, think about the "gas spring effect" in regards to port+plenum length. This can give you some free power in certain RPMs. "helmholtz resonator" or whatever it's called...

Personally, I am going with a blow-through setup on my Sportster so I can run a large plenum and an intercooler.


Let's see some photos, they are worth 1000 words. A large single cylinder engine could have issues blowing it's whole exhaust load into a small turbine housing, especially if it's too close to the exhaust valve. In a multi-cylinder engine, the turbine housing has a chance to take the exhaust in small steps. Compare this to dumping a liter of water down the sink with a large cup versus a bunch of shot glasses filled with water one at a time. The water can still get down the drain in about the same amount of time, but the sink will momentarily back-up with the large dump and flow continuously with the small shot glasses dumped one at a time. You can lessen the effect by having a larger turbine housing or more volume in the exhaust between the valve and the turbine.

As far as compressor oil seals- Ideally, you want a carbon seal. Most turbos come with a piston-style ring seal. You can run the ring style with the blow-through but it's a good idea to have a second throttle butterfly DOWNSTREAM of the compressor that is adjusted to be just a little more closed than the real throttle butterfly, except WOT. This will give you enough pressure delta to keep the oil from getting sucked into the plenum. This idea has worked well for a lot of blow-throughs but I wouldn't attempt it if your bike must spend a lot of time at idle.



 

[moirmyster]

Thanks for that,i think il try fidling with the timing havnt tried that yet.
Il try get some photos up so u can hav a laugh lol.
Iv proble done a million thing wrong.But it runs fine on pump gas so must be doing something right.
Check my spark plug it definetly not to white it a nice tanned coulour.

[moirmyster]

hey guys
Had a play round with it the other day done a few jetting changes and adjusted the timing got it running sweet as goes mean
I had it to rich on the pilot jet.
Ill get some pics up for u guys to have a look at.

[moirmyster]

ok i have another problem now,as i have made more horsepower,i am wreaking gears in the gear box done third gear as is the most used gear.the dogs are ok just breaking off teeth.iv put a differnent gear box in a 5 speed,standard box is a 6 speed,the 5 speed is ment to be stronger.is there any way of making the gears harder,or any other things i could try.

[1212FBGS]

breaking off the teeth is a common problem with motorcycle trans... althow i have had billet gears made for my turbo motors the real problem is with the shafts themselves... usually 2nd and 3rd gears are in the center of the trans shafts, under power the shafts flex apart and the power crawls up the tooth face where there is less engagement and ultimately there will be less teeth . harder gear teeth is not the best way to go. i think we made my gears out of 6310 it was the same material used in off shore power boat drives, it takes a shock load much better and then we had them surface hardened for wear (yeah right).. my advise is to have new shafts made. i can give you a recommendation as to someone who can make em for ya but being a really really low production run you are probably looking somewhere north of $2g
Kent

[Queeziryder]

breaking off the teeth is a common problem with motorcycle trans... althow i have had billet gears made for my turbo motors the real problem is with the shafts themselves... usually 2nd and 3rd gears are in the center of the trans shafts, under power the shafts flex apart and the power crawls up the tooth face where there is less engagement and ultimately there will be less teeth . harder gear teeth is not the best way to go. i think we made my gears out of 6310 it was the same material used in off shore power boat drives, it takes a shock load much better and then we had them surface hardened for wear (yeah right).. my advise is to have new shafts made. i can give you a recommendation as to someone who can make em for ya but being a really really low production run you are probably looking somewhere north of $2g
Kent

As Kent so rightly says, you are going through the weakest links within your engine. You may make the trans strong enough, but then you will start jacking the shafts aparts, thus going thu' cases (I had the same problem on my drag bike)

I would recomend talking to Chris Wiesmann who makes trans for F1, Indy, Power Boats, Drag Racing etc and is very helpfull. His company Traction Products is based in Costa Mesa California

Neil

[oz]

ok so iv got this bike going really good now,i ported the head and oversize valves,has got heaps more power than a stock one.my problem now is its getting to hot as its making more power.Its hard to keep cool as its air cooled engine.i raced it the other day for about 10 mins and it got that hot it nipped up,let it cool down and its away again.the engine hasnt got a oil cooler so the only thing i could think off is some how hook one up,like with a external oil pump.
has any one got any suggestions.

Ever thought of running alcohol it should run cooler.
Oz

OOps should have read right to the end

[1212FBGS]

Neil
Wiesmann makes some pretty nice stuff...i think they get 5 or 6 g's for a kawi trans.... It took quite a while for Steve Rice to get him to finish the zx trans.....i think it would be pretty hard to get him to do something for and old Honda single
kent

[Queeziryder]

Hi Kent,
I know, I trashed a couple of 4-speeds on my bike, before going over to the 3 speeder. Then I just started trashing cases, in 1 season I went thru' 4 sets of KZ cases

Depending upon the trans design, you could take out top gear and put in a double width 1st

Neil

[moirmyster]

ok thanks for the ideas,im not wanting to spend much,as its just a hack around bike.think i might just stick to puting in second hand gears,or splash out on new 3rd and 4th gears,think the gears were quite worn gone through the hardening,more than likley my problem.