Turbo YZ


350 replies to this topic
  • grayracer513

Posted April 08, 2009 - 08:19 PM

#41

It is true that thumpers present problems when running turbos, and they have a greater tendency for lag than twins do. But that can be resolved the same way as with multi-cylinder engines: use a small enough exhaust scroll to get the shaft speed up early. You sacrifice some in terms of the ultimate boost the unit will produce, but you should be able to get it over ten pounds pretty easily.

The problem I see with concealing it under the seat/air box, even if you make the air box able to survive it (might consider replicating the outer covers in aluminum) is that the heat from the exhaust side will heat the intake, and there's no place for an intercooler in this setup. It may cause no problem, but there's something to look out for.

  • FinchFan194

Posted April 08, 2009 - 08:38 PM

#42

hell yeah is right! ill wait for a muddy day to ride it the first time that way i wont have enought traction to wheelie over backwerds! haha it will take some time to make work. i just got in from working on it. took the carb off (pain in the ass), finished my temporarty oil return line and took my turbo off so we can put an angle in the compresser tube to get the charge tube around the shock. while i got the turbo off should i set the shock a little bit stiffer?

also i have a bunch of heat fome/tape off of old snowmobiles. that plus the aluminum gards i plan to build should help with the under-seat-heat problem. i plan to put the sides off the airbox back on so the turbo can not be seen. but they will probably get to hot. maby ill put some kinda vents in them.


Maybe you should relocate the seat to the top of the handlebars! That ought to keep you from going over backwards j/k I personally would love to see some video of you riding I bet the thing is NUTS. Good luck gettin er done.

  • gbalias

Posted April 08, 2009 - 09:39 PM

#43

yz480doinwork keep up the work and keep posting the pics... It's funny how everyone thinks there a expert when someone else is doing the faberication, ahh the joy of the internet...



id say im an expert at building turbo systems and tuning/building high performance A/M fuel injection systems. trained, certified, and many years experience. anything else?



I can help you out with the welding, I find it pretty enjoying actually. We're down to 4 day weeks now.


have him ^ do the fab work


ive done a lot of manifold and exhaust fabbing but it all starts with CAD for me. the less room for error, the less work youll have to do later. but then again, some of our cars can be sold for like 20 YZ's. :thumbsup:


either way, i still wanna see this thing in action. keep it up.


oh, and please, please check that compressor map for that turbo. it might never build boost if its way off.

  • TIG88

Posted April 09, 2009 - 12:39 PM

#44

Hell yeah man!!!!!!!!! Fire her up and let her EAT! Take some video of the action and shut up all the nit-pickers!!!!!! oh yeah wear a helmet and possibly a cup!



No body here is trying to nit-pick this guy. We're just trying to lead him in the right direction and give him some pointers. It seems like the people who have given him detailed advice are pretty knowledgeable in out fields. Hell, I offered to weld the exhaust. I think we all wanna see this thing making 80ft roosts somewhere, but its a little more complicated than slapping a turbo on and tearin through some mud.

  • yz480doinwork

Posted April 09, 2009 - 01:08 PM

#45

No body here is trying to nit-pick this guy. We're just trying to lead him in the right direction and give him some pointers. It seems like the people who have given him detailed advice are pretty knowledgeable in out fields. Hell, I offered to weld the exhaust. I think we all wanna see this thing making 80ft roosts somewhere, but its a little more complicated than slapping a turbo on and tearin through some mud.


exactly, yes, there are a lot of people who know there stuff here. if my exhaust wasnt already on i would think about having tig do it. maybe in the future i can have it re-done. i know its no good to build engines on a budget but im watching my money. i have spend just over 1/4 of a what a yfz kit costs. i dont plan on spending more than half.

oh, and please, please check that compressor map for that turbo. it might never build boost if its way off.


i did do some research before i went and bought a turbo. i talked to 2 moto a little, and someone that helped build that bike. i also talked to a guy that builds yfz kits and i was on yfz tech looking for info. there are three turbo's i heard have been used. the garrett gt12, gt 15 and an areocharger turbo. the areocharger is really neat but it was way out of my price range. since i had heard both the gt12 and gt15 had been used i had to come to some decision. after looking on garrett i found that the GT12 required oil and water but the GT15 only required oil. then i found a GT15 brandnew on ebay for less than 1/2 cost. i decided to go with that. that way i wouldnt have to mess with antifriez lines. it may be a little big tho. im hoping with my bigbore and port and polish job everthing will work out nicely. but if it dosn't ill end up buying a GT12. i have looked at compresser and turbine maps alot but i honistly dont know how to read them. can some one explain to me how to read these. and what the X and Y axis's have to tell me. thanks

yz480

  • TIG88

Posted April 09, 2009 - 01:22 PM

#46

This might help you out a little:

http://www.enginelogics.com/cmaps.html

From what I understand the GT15 is a pretty small turbo. I would bet it would light. Id bet it will have an almost 2 stroke-ish like hit in the upper powerband.

Do you plan on strengthening the valve-train, or a better headgasket or something?

  • yz480doinwork

Posted April 09, 2009 - 01:35 PM

#47

i wasnt planing on it but it may be needed. but on 5 pounds maybe not. i have heard the GT15 is a little to big for this engine but i hope it works. ill look at that link. i was doing the calculations trying to read the map but i didnt get far. i did find out that my 478 cc engine flows 70.601851 cubic feet per min. idk if im doing this right? but i need that calculated to pounds of air pr min. maybe that line will help. what do you guys recomind for valve train stuff?

  • yz480doinwork

Posted April 09, 2009 - 01:39 PM

#48

haha i aleady looked at that page. thats how i got to that stat i posted. ill try to get farther

  • yz480doinwork

Posted April 09, 2009 - 01:51 PM

#49

at sea leavle, 75 degres F, 8000 RPM, 5 pounds of boost a 478 cc engine moves 7.026314 pounds of air per min. , that dont sound right but 7.02 puts me in a good spot of the X axis of the graph. did i do this right? the way its looking if the pressure ratio was 1.75 i would be at the max effency on the graph. i still have no idea what im doing lol.

  • grayracer513

Posted April 09, 2009 - 02:25 PM

#50

i wasnt planing on it but it may be needed. but on 5 pounds maybe not. i have heard the GT15 is a little to big for this engine but i hope it works. ill look at that link. i was doing the calculations trying to read the map but i didnt get far. i did find out that my 478 cc engine flows 70.601851 cubic feet per min. idk if im doing this right? but i need that calculated to pounds of air pr min. maybe that line will help. what do you guys recomind for valve train stuff?

The symptoms of too large a turbo are a reluctance to run into positive pressure, followed by a huge spike in power once it does go positive. It will also be very difficult to jet, and if run without a waste gate will spool up pressure infinitely until something flies off. This was the case with the first turbo job I was ever involved with, which was an old 750 Honda. The turbo was given to my boss, not selected for the project. It screamed, but was nearly unrideable.

at sea leavle, 75 degres F, 8000 RPM, 5 pounds of boost a 478 cc engine moves 7.026314 pounds of air per min. , that dont sound right but 7.02 puts me in a good spot of the X axis of the graph. did i do this right? the way its looking if the pressure ratio was 1.75 i would be at the max effency on the graph. i still have no idea what im doing lol.

One thing that is difficult to graph and calculate about the way turbocharged engines behave is that the engine is "normal" until there is enough exhaust volume being produced to raise the compressor speed high enough to create positive manifold pressure. Once that happens, the exhaust volume increases by virtue of the additional fuel/air being throughput, and the shaft speed is increased. In essence, the engine gets "bigger", and produces more exhaust, which creates more boost, which creates more exhaust.... In a very real sense, it feeds on itself.

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  • yz480doinwork

Posted April 09, 2009 - 02:36 PM

#51

The symptoms of too large a turbo are a reluctance to run into positive pressure, followed by a huge spike in power once it does go positive.


this is why i am questioning getting a low compression piston. if the turbo is to large and it takes a bit to get into the "positives" i would like to have the snap or torque of stock compression. this turbo is wastgated so there wont be a problem of spiking or overboosting. i was just out working on my carb. i put a 205 in for a main jet. it will pry be way rich but at least it wont be too LEAN. problem now is i lost my dam washer and o-ring off my air/fuel screw. im having the best of luck. haha but my oil filter cap came in today so im hoping to have the oil line ran tonight.

  • gbalias

Posted April 09, 2009 - 04:33 PM

#52

its coming together.

youre gonna be running above 100% VE once you get into boost. do you have a way of metering the fueling to dial it in under those conditions?

are you going to remap the timing as well?

both need to be done for a reliable setup. only way to tune right is on a steady state. no matter what anyone else tells you.

  • grayracer513

Posted April 09, 2009 - 04:47 PM

#53

The problem with HC pistons in turbocharged engines is that the combination of the compression ratio and the increased pre-compression pressure in the cylinder often results in pre-combustion heat that is excessively high for combustion to be controlled properly, resulting in severe detonation at times.

What needs to be understood is that while increasing compression ratio and increasing boost pressure both increase pre-combustion pressure and power, they increase power for different reasons. HC pistons improve the combustion efficiency of the engine by a fractional margin. Supercharging increases power by increasing throughput, essentially making the engine bigger than it really is. It is realistically possible to more than double the fuel/air throughput of some engines by supercharging, which has the effect, for all practical purposes, of doubling its size. It is usually necessary to back down from the ideal compression ratio for a normally aspirated engine when supercharging it in order that the dynamic pre-combustion pressures don't rise to an impractical level. The loss in static compression ratio is generally more than compensated for by the increase in volume throughput that results from even as little as +5 pounds of manifold pressure.

  • MuDPoUNdeR

Posted April 09, 2009 - 04:52 PM

#54

Gray what do you do for a living? After saying what you did in your last post here it makes me wonder ...

  • grayracer513

Posted April 09, 2009 - 05:29 PM

#55

I get paid to think.

  • yamaha6j

Posted April 09, 2009 - 05:40 PM

#56

That's powerfull !!! Gray where can we send the money, because you haven't charged us a dime.

  • gbalias

Posted April 09, 2009 - 06:47 PM

#57

What needs to be understood is that while increasing compression ratio and increasing boost pressure both increase pre-combustion pressure and power, they increase power for different reasons. HC pistons improve the combustion efficiency of the engine by a fractional margin. Supercharging increases power by increasing throughput, essentially making the engine bigger than it really is. It is realistically possible to more than double the fuel/air throughput of some engines by supercharging, which has the effect, for all practical purposes, of doubling its size. It is usually necessary to back down from the ideal compression ratio for a normally aspirated engine when supercharging it in order that the dynamic pre-combustion pressures don't rise to an impractical level. The loss in static compression ratio is generally more than compensated for by the increase in volume throughput that results from even as little as +5 pounds of manifold pressure.



what he said = VE

but all that is relative to displacement as far as the ratio of compression reduction to the amount of desired positive pressure in the 'manifold' ... plus not to mention the quality and construction of the internal components.

another misconception foiled....fact: lowering compression ratio increases EGT's. so you have to find the delicate balance, especially since its not an intercooled setup you got goin here.

  • grayracer513

Posted April 09, 2009 - 07:50 PM

#58

another misconception foiled....fact: lowering compression ratio increases EGT's. so you have to find the delicate balance, especially since its not an intercooled setup you got goin here.

An intercooler's primary job is to reduce the heat created entirely within the intake by the compression of manifold air, although they will certainly help with heat picked up through radiation/convection from the exhaust. The big problem with exhaust gas temps (EGT) is in damage done to the turbine blades.

It is true that as compression ratios drop, EGT's will rise, but in a gasoline engine, you still have the problem of controlling detonation, and this will usually trump just about every other consideration in building a very high performance turbo system.

One thing we found on the second twin turbo Chevy application I worked on was that lengthening the exhaust between the engine and turbine contributes more to lowering the EGT at the turbine than it does to any delay in compressor response. When we extended the system, we were able to run more boost at the same resultant EGT.

  • yz480doinwork

Posted April 09, 2009 - 08:13 PM

#59

great info Grey & gbalias. running only 5 pounds of boost, which side should i go for? lowing compression or keeping it the same while keeping heat down? is the heat difference that sugnificant? say between a 11.5:1 ratio and a 9:1 how much would the temp actually drop? what ratio should i go for?

  • grayracer513

Posted April 09, 2009 - 08:48 PM

#60

You should be able to run 7-9 pounds with 10:1 or less with 97 -100 octane, but you may want to invest in a programmable ignition from MSD to give you more control over the timing.

The reduction in EGT with higher compression is really more noticeable in a normally aspirated engine, and the temperature drop in the exhaust is due to the improvement in combustion efficiency; more of the burn occurs in the chamber and less outside. But once things start spooling up, all bets are more or less off, and EGT becomes more a product of the amount of fuel being burned than of decreased efficiency. Still, you should try to use as high a compression ratio as you can. It may take some experimentation, but I'd guess you'll end up around 9 or 10:1.





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