gday folks,
im chasing pics, info, advice on draw thru carby turbo set ups.....
im building an old skool muscle bike atm, so am looking for whatever info i can have reguarding a draw thru set up.
engine in question is a CB750 SOHC 750cc 4cyl (spare me the honda jokes!)
also if anyone has parts to suit, PM me.
cheers.joe.
from my limited experiance with one on a 6 cyl holden years back there reliable once setup but a pain in the ass to get right !
Advice don't bother with fuel injection so cheap nowdays its a better option , or go blow through so you can run enough boost to make it worth while turboing it in the first place. Better throttle responce less lag higher boost(ability to run intercooler).
If you really still want to just cause you can , use a single large SU carb off a car. Burst strip in outlet side of turbo manifold between intake of motor is a good move to. Use a blow off valve but dump excess straight to air, dont recurculate it. Keep intake manifold between turbo and head short and lower volume half size of motor cc up to motor cc. Best position for turbo is behind motor for this. (easyest)
Good luck.
I would say no to a bov cause you are venting air/fuel mix that could end badly.
I don't like draw through carby cause all I read on OSS is that they are extremely hard to get running well compared to blow through and blow through carbs can be even harder again than blow through Efi
If I was going to do blow through I would use 2 tb's of a newer bike with one as a primary for reasonably ok throttle response on small throttle and the other set up as a secondary that went from 0 - 100% open all in the last 40% odd of the throttle.
i had a draw through with a webber on a gemini years ago. worked great,
if i was going to do it on a bike id prob use a single SU carbie.
Na venting air fuel mix is cool , just make sure its not going anywhere you dont want cooked (and the filth knowing what it is) lol If you want real fun pop a spare spark plug in the output pipe and run it out the back for big flame/pops on over run looked great on the rolla lol
thanks guys,
ive played with turbo's in cars and bikes before, all of it as a blow thru set up. however this new build im doing, is based around a 1974 honda cb750.
ive got plenty of modern brake and suspension parts to go on it, but want to keep the body work and motor old skool, and keep a look of a early 80's race bike.
hence why the thought of draw thru set up, thats what was popular in the 80's, and i figured it would fit in best with the build.
also, i dont think the original carbs that came on the honda would like boost all that much tbh.
cheers.joe.
Use a smaller turbo like a T25 get it carbon sealed, and use a Mikuni HSR42 of a yank tractor. I've just had one on the dyno that a mate has built on a stock 1127 motor using a T3 turbo with HSR42 carb, running 160 at 6.5psi boost on stock compression, should be able to run about 8psi on the 1127 motor once a lock up clutch is fitted. Get yourself an adjustable wastegate so you can tailor the boost levels. Jetting can be a bit of a pain to get set up, but it is straight forward enough. If you intend to run a blow through then get a set of CV carbs and respace them to suit, and again use a smaller turbo like a T25, you won't need a carbon seal, and with pitot tubes the jetting will be almost stock, although you sometimes need to drop a size on tha mainjet. either way get yourself a low pressure fuel pump and regulator for draw through or a rising rate regulator for blow through. Both systems have their advantages and disadvantages.
This is my mr turbo set up, for my 81 GSX1100 not fitted as yet, these come up on ebay US from time to time. They dont use the rajay turbo anymore (now a Garrett), I have a HSR42 carb as per Dynomutts suggestion. My system is 25yrs old and aside from the Garrett and a newer waste gate it is still availible from Mr turbo. DO NOT deal with Mr turbo Australia. They are useless! Hope it gives you some inspiration.
thats the shit!!
fuck yeah,nice work!!!
cheers.joe.
Never put a blow off valve after the carby, EVER....
Not only is there the chance you'll catch of fire, you'll get put off the road faster than something really fast...
Do these photo's mean you'll getting your act together Geoff?
Does it go yet?Mine doesn't
It will be going very soon
2nd gear has cracked the shits and was beating the insides with a hammer, 3rd isn't happy either.quote:Originally posted by 80s freak
It will be going very soon
I've sacked them both and 6th give me a funny look so i fucked it off as well.
Other than the motor being in half its awesome
Gimmy a call and ill hook a niger up.
there would be no point putting a blow off valve after the carbie anyway, it wouldnt do anything.
it would stop the compressor from stalling tho
Compressor is running in hi vac when the throttle is shut, very different to blow through when the compressor back pressure stalls the turbo , i wouldn't worry about a bov..
saw a mr turbo oldschool kawasaki kit wednesday, guy that had it was not sure if it was z900, gpz900 or zzr1100, could be for sale but the headers would need modding for bike use as its been in a car and swept over the head. everything else is in std position, garrett turbo ,needs attention, probably strip and clean , s&s carb i think .
As others have said you do not use a BOV on a draw through, You really do not want pressurised air/fuel mix being blown out of the plenum covering you and the bike just waiting for a source of ignition to barbecue your bollocks. The plenum should have a couple of burst plates, but these are not really needed. A wastegate of about 38mm should be sufficient, ideally an adjustable one, you can add a simple boost controller into the mix, start with a low pressure spring of around 5 psi and then add regulated boost pressure on top of the diaphram to increase the boost level that the wastegate opens at. Get a good quality glycerine filled boost gauge, and test it with a small pump with a known accurate gauge. Check the wastegate using the same method. For a roadbike around 1100/1200cc go with an HSR42, if you go with an HSR45 you'll get more outright power at the top, but it can make them a little lumpy down the bottom end. Depending on what amount of boost you intend to run you will need some method of retarding the ignition, a Dyna2000 ignition has a retard facility which can be activated by a boost pressure switch mounted to a welded boss on the plenum. Mount the boost gauge on one of the vaccum take offs on the inlet stubs, it's easier than welding another boss onto the plenum. Oil pressure can be an issue, especially on plain bearing cranks which run much higher oil pressures than roller bearing cranks, so some form of restriction in the oil line often a 120 mainjet fitted into one of the oil fittings will be enough. On roller bearing motors getting the pressure high enough can be difficult, higher outpur oil pump gears are available for some engines.
currently looking to do the standard 1974 honda sohc motor, internally gated, garret t2 turbo from a turbo nissan exa or something simular no more then 6psi, unsure on what carby to use, i wonder if the hsr42 carb would be to big for it?
i'll make a custom header, dump pipe and plenum chamber.
cheers.joe.
Most of the turbo's out there today are not suitable for use in vacuum the piston ring type shaft seals will leak large amounts of oil, you need to be sure you get a carbon seal type turbo or at least one that can be converted to the better seal.
42 may be a bit big on the old 750
definitly a carbon seal for the draw through, no bov, just use the wastegate.
If you're offended, you've only yourself to blame
Booster are parts still available for the old rajay turbos?
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