Draw through carb tech?
Discussion
Anyone have any experience with a draw through carb turbo setup? If so I would like to know if there is an intake track maximum length, and if it must be "all" downhill toward the intake plenum? Also what carb works best with this type of setup? Ive heard an SU carb works well, and also a Mukuni HSR42. This is a motorcycle.
And before anyone gets carried away and saiz "why not EFI"? Is because thats what we normally do with all our 300+hp bikes, but this one is a little twin cylinder crusier that is going to be a low cost low boost (6 psi) engine. We dont want to run a stand alone system on this one
Any help greatly appreciated.
Chad
And before anyone gets carried away and saiz "why not EFI"? Is because thats what we normally do with all our 300+hp bikes, but this one is a little twin cylinder crusier that is going to be a low cost low boost (6 psi) engine. We dont want to run a stand alone system on this one
Any help greatly appreciated.
Chad
from memory - I think draw thru carb systems are to be well avoided - something to do with the fuel going throught the compressor housing and poor throttle response - a blow thru carb system is more preferable - you just gotta make sure you pressurize the flaot chambers in order to prevent the fuel being blown out of the flaot chambers - if you are using CV carbs you will need to ensure the CV slides operate correctly when under boost too........I did a ram-air system on a standard honda black-bird and the theory of operation is quite similar - I pressurised the float chambers and the CV slides via the CV slide vent tube in the middle of the 4 carbs - and it went like a missile!
The fuel going through the compressor is a good thing. The vaporising fuel cools the charge - kind of like a built-in intercooler - and the mixing of fuel and air is beyond reproach. You do need to provide a big blow-off valve as a safety measure in the event of backfires (I say "need", but there is at least one respected contributor to this forum who gets away without it 
) and you need to make sure the seals round the compressor drive shaft can cope with petrol being present. And you have the huge advantage of not having to piss around with the carb to (a) make it work at all under boost and (b) make it work properly in terms of delivering the correct fuel/air mix.
No need for the inlet tract to run downhill, as the petrol will be nicely vaporised after going through the compressor, so it won't pool (at least not while the engine's running; you might get a few charges' worth of pooling when you switch off, but that just means you need less choke to start it).
You can't use an intercooler, but you won't need one anyway, because of the cooling effect of the petrol vaporising and the low boost pressure you're planning.
You want the intake tract length as short as possible, but that's always the case for any boosted setup (he says with something of an oversimplification).
SU carb, yes of course, goes without saying
What engine is it - is it a 360-degree parallel twin? If so you could make a very neat setup - turbo mounted on the front of the engine as close as possible to the exhaust ports (watch out for clearance for the front wheel on full bump), SU carb on the compressor inlet, compressor outlet pipe runs over the top of the head then divides in two to reach the inlet ports.
If it's a 180-degree parallel twin or a V-twin it's more of a problem because of the unequally-spaced intake pulses. A fair bit of experimentation will be required, involving plenum chambers, different intake tract path lengths to the two pots, different valve timing on the two pots, to get good even fuel distribution between the two pots at all speeds - without variable intake tracts and/or variable valve timing you won't be able to get it right all the way through the rev range, so it'll be a compromise.
) and you need to make sure the seals round the compressor drive shaft can cope with petrol being present. And you have the huge advantage of not having to piss around with the carb to (a) make it work at all under boost and (b) make it work properly in terms of delivering the correct fuel/air mix. No need for the inlet tract to run downhill, as the petrol will be nicely vaporised after going through the compressor, so it won't pool (at least not while the engine's running; you might get a few charges' worth of pooling when you switch off, but that just means you need less choke to start it).
You can't use an intercooler, but you won't need one anyway, because of the cooling effect of the petrol vaporising and the low boost pressure you're planning.
You want the intake tract length as short as possible, but that's always the case for any boosted setup (he says with something of an oversimplification).
SU carb, yes of course, goes without saying
What engine is it - is it a 360-degree parallel twin? If so you could make a very neat setup - turbo mounted on the front of the engine as close as possible to the exhaust ports (watch out for clearance for the front wheel on full bump), SU carb on the compressor inlet, compressor outlet pipe runs over the top of the head then divides in two to reach the inlet ports.
If it's a 180-degree parallel twin or a V-twin it's more of a problem because of the unequally-spaced intake pulses. A fair bit of experimentation will be required, involving plenum chambers, different intake tract path lengths to the two pots, different valve timing on the two pots, to get good even fuel distribution between the two pots at all speeds - without variable intake tracts and/or variable valve timing you won't be able to get it right all the way through the rev range, so it'll be a compromise.
wow great info! Much appreciated!!!
I like the idea of the draw through as it sounds like it is alot easier to jet and dooes not require higher pump pressure to stay above manifold pressure.
I had a new HSR42 Mukuni w/accel pump under my bench at work collecting dust so I was going to use that, as I have seen a few motorcycles with this carb, but if you can point me toward the SU carb of choice I will grab one of those aswell, so I have both to test while on our dyno.
Its a Triumph 865cc air cooled (and oil) paralell twin, and this one actually fires 270 degree intervals, 9:2:1 comp. Ive allready chopped the exhaust off so I have 2 x exhaust manifolds to make the turbo manifold with, the GT12 actually fits very close to the head on the front of the engine and is inside the frame rails so no chance of bumping it with the front fender or tire.
The reason I asked about intake track length is that it will be around 14 inches from compressor housing to the inlet plenum, I just got a hold of an old turbo book and it has ALOT of draw through setups on 4 cyls, 6,s and V8's, and they deffenatly have uphill climbs on there draw throughs, the biek wont have a massive uphill its just the way the compressor fits it exits at the top and has to do a 180 bend, then straight aong the engine and then a 90 into the intake plenum.
Peak HP is not our goal with this one, drivabilty is, I want to make it as smooth off idle and mid range as possible, so if you think there is one carb better then the other please advise, and if its an SU is there a certain model I should be looking for?
Il get pics of the parts and location of parts tommorow when Im at work, so yu can get a better idea of the bike.
again I appreciate all the help, im lost without EFI and computers lol
Chad
I like the idea of the draw through as it sounds like it is alot easier to jet and dooes not require higher pump pressure to stay above manifold pressure.
I had a new HSR42 Mukuni w/accel pump under my bench at work collecting dust so I was going to use that, as I have seen a few motorcycles with this carb, but if you can point me toward the SU carb of choice I will grab one of those aswell, so I have both to test while on our dyno.
Its a Triumph 865cc air cooled (and oil) paralell twin, and this one actually fires 270 degree intervals, 9:2:1 comp. Ive allready chopped the exhaust off so I have 2 x exhaust manifolds to make the turbo manifold with, the GT12 actually fits very close to the head on the front of the engine and is inside the frame rails so no chance of bumping it with the front fender or tire.
The reason I asked about intake track length is that it will be around 14 inches from compressor housing to the inlet plenum, I just got a hold of an old turbo book and it has ALOT of draw through setups on 4 cyls, 6,s and V8's, and they deffenatly have uphill climbs on there draw throughs, the biek wont have a massive uphill its just the way the compressor fits it exits at the top and has to do a 180 bend, then straight aong the engine and then a 90 into the intake plenum.
Peak HP is not our goal with this one, drivabilty is, I want to make it as smooth off idle and mid range as possible, so if you think there is one carb better then the other please advise, and if its an SU is there a certain model I should be looking for?
Il get pics of the parts and location of parts tommorow when Im at work, so yu can get a better idea of the bike.
again I appreciate all the help, im lost without EFI and computers lol
Chad
I dont know if these links will work but this is one of our latest projects... its a Rocket 3, with a 2.3 litre turbocharged, intercoled, EFI with secondary injectors, alot of work went into this one, rides as smooth as silk untill you open it up, then it smokes the 240 rear tire at just about any speed.
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[/URL]The water injection guys have problems with impellor blade erosion when they use upstream injection. I think you'd need to be sure that the fuel was all vaporised before then, and that might be difficult. Gut feeling is that however you try, there will always be *some* element of wall wetting and puddling. Obviously from the point of view of tuning and throttle response the more wetted area you have the worse it will get.
Not disagreeing re water and erosion, but suck-through used to be a pretty standard method in the days before everything was injected, and the turbos seemed to cope OK as long as they had the correct type of seal on the compressor shaft. Without analysing it, my gut feeling is that fuel droplets will be smaller and less dense than water, and should therefore be less of a problem; there may also be chemical effects with water, but again not with fuel. I'd guess that these days, with the preponderance of injected systems, the tricky bit will be getting a petrol-sealed turbo.
WRT wall wetting/puddling, my thinking is that we're dealing with a fairly compact installation fitted round the top end of a bike engine; unless particular measures are taken to cool the intake tract it'll probably run at a sufficient temperature that there won't be much scope for trouble.
Carbs - the Mikuni HSR is a "guess-and-by-God" carb as opposed to the feedback-controlled constant-depression SU. It may give a tad more top-end power but it will be harder to set up, and especially if your goal is drivability and a good low-end performance the SU will be better. In terms of size, the choice is between HS4 (1.5", 38mm) and HS6 (1.75", 44mm)... probably the HS6 but the HS4 is not out of consideration. The HS series of SUs is the one to go for, as later variants began to suffer from being pissed around with in the name of emissions control, which made them more complicated, harder to work with/on, and lost that lovely mixture adjusting nut on the main jet.
The Garrett GT12 seems to be a pretty huge turbo. Why that one - is it because you've got one lying around? I can't help thinking that something designed for getting hundreds of bhp out of Scooby engines is going to be a tad oversized for this job... Also, it seems to use both oil and water cooling. Perhaps you'd be able to get away with not connecting the water cooling because you're using it at a fraction of its rated power, but I wouldn't like to depend on that. I can't help thinking it's going to be distinctly suboptimal, especially if drivability and a good bottom end are important I'd be looking for something off a tiddly-engined little Japanese car that produces 80bhp or a bit more. Or perhaps an MG Metro Turbo turbo. (In fact, to go against myself a bit here, that might well be the beast to look at; you get the turbo and the SU carb, already set up for blow-through and pretty much the right size, and the car will have the correct fuel pump as well; much of the fiddly stuff has already been done for you.)
It's probably worth pointing out that you can often assemble turbos with the compressor and turbine housings at different relative orientations to make the plumbing easier.
You can probably take advantage of the asymmetry of the turbo to provide different intake tract path length for the two cylinders to help even out charge distribution - this would be more of a top end effect, at the bottom end the events will all be too slow to play these sort of tricks with a practically-sized installation. This is another area where suck-through has an advantage, as you've got more freedom to lay out the plumbing between turbo and intake ports. I'd guess you'd also want to have a bit less intake valve lift and duration on the first of the two to fire.
WRT wall wetting/puddling, my thinking is that we're dealing with a fairly compact installation fitted round the top end of a bike engine; unless particular measures are taken to cool the intake tract it'll probably run at a sufficient temperature that there won't be much scope for trouble.
Carbs - the Mikuni HSR is a "guess-and-by-God" carb as opposed to the feedback-controlled constant-depression SU. It may give a tad more top-end power but it will be harder to set up, and especially if your goal is drivability and a good low-end performance the SU will be better. In terms of size, the choice is between HS4 (1.5", 38mm) and HS6 (1.75", 44mm)... probably the HS6 but the HS4 is not out of consideration. The HS series of SUs is the one to go for, as later variants began to suffer from being pissed around with in the name of emissions control, which made them more complicated, harder to work with/on, and lost that lovely mixture adjusting nut on the main jet.
The Garrett GT12 seems to be a pretty huge turbo. Why that one - is it because you've got one lying around? I can't help thinking that something designed for getting hundreds of bhp out of Scooby engines is going to be a tad oversized for this job... Also, it seems to use both oil and water cooling. Perhaps you'd be able to get away with not connecting the water cooling because you're using it at a fraction of its rated power, but I wouldn't like to depend on that. I can't help thinking it's going to be distinctly suboptimal, especially if drivability and a good bottom end are important
I'd be looking for something off a tiddly-engined little Japanese car that produces 80bhp or a bit more. Or perhaps an MG Metro Turbo turbo. (In fact, to go against myself a bit here, that might well be the beast to look at; you get the turbo and the SU carb, already set up for blow-through and pretty much the right size, and the car will have the correct fuel pump as well; much of the fiddly stuff has already been done for you.) It's probably worth pointing out that you can often assemble turbos with the compressor and turbine housings at different relative orientations to make the plumbing easier.
You can probably take advantage of the asymmetry of the turbo to provide different intake tract path length for the two cylinders to help even out charge distribution - this would be more of a top end effect, at the bottom end the events will all be too slow to play these sort of tricks with a practically-sized installation. This is another area where suck-through has an advantage, as you've got more freedom to lay out the plumbing between turbo and intake ports. I'd guess you'd also want to have a bit less intake valve lift and duration on the first of the two to fire.
The Garrett GT12 is a TINY turbo, it fits in the palm of my hand, its actually the smallest turbo I have ever seen, we are use to T3's and T04 on our bike setups. The compressor flows in its effecieny range from around 4 - 13 lb/min which is good for making around 80 - 130 crank hp and the bike makes 65hp at the crank and hopefully can make around 100 - 110 with the turbo at the crank which should get me around the 90 - 100 rwhp mark if all goes well.
And yes it does have a water jacket which can be left blank with plugs, but im actually going to run oil through it with a separte oil cooler just for that loop, it has to be better then air cooling it, i know its made for water and it is normally only around 15 psi, but im sure the housing can handle the 40 psi that this oil pump makes, its worth a try thats for sure.
Im gunna check out ebay for one of those SU's that you have mentioned, unless you know of a good sorce of them? Or are they stil available new?
Yah before EFI it seemed like a good amount of turbo setups where the suck through configeration.
Did get any pics today, to many customers at the shop the turbo Triumph got the back burner today, Il probably check things out again on Tuesday after the holiday.
Thanx again for teh hep much appreciated!
Chad
And yes it does have a water jacket which can be left blank with plugs, but im actually going to run oil through it with a separte oil cooler just for that loop, it has to be better then air cooling it, i know its made for water and it is normally only around 15 psi, but im sure the housing can handle the 40 psi that this oil pump makes, its worth a try thats for sure.
Im gunna check out ebay for one of those SU's that you have mentioned, unless you know of a good sorce of them? Or are they stil available new?
Yah before EFI it seemed like a good amount of turbo setups where the suck through configeration.
Did get any pics today, to many customers at the shop the turbo Triumph got the back burner today, Il probably check things out again on Tuesday after the holiday.
Thanx again for teh hep much appreciated!
Chad
Yah I have already clocked the turbo to point the exhaust housng and compressor in the direction I want, its not that I want the compressor to exit at the top its the only way I can have it exit with the way it fits in between the frame rails. It actualy had a roll pin in the center housng to locate the exhaust housing in a certain direction but that was quickly removed with some pliers, maybe the GT12 was mass produced for a certain model veheicle so they pinned the exhaust housing in place to make fitting easier for the normal mechanic.
Chad
Chad
skinart said:
The Garrett GT12 is a TINY turbo, it fits in the palm of my hand, its actually the smallest turbo I have ever seen, we are use to T3's and T04 on our bike setups. The compressor flows in its effecieny range from around 4 - 13 lb/min which is good for making around 80 - 130 crank hp and the bike makes 65hp at the crank and hopefully can make around 100 - 110 with the turbo at the crank which should get me around the 90 - 100 rwhp mark if all goes well.
Oh, that's interesting. There must be two different turbos called GT12 because when I looked it up on Google it found a big bastard good for 500bhp
Very useful to know that, as such a tiny beast could come in handy for a project of my own. The help goes both ways! I'd also somewhat underestimated your power outputs (probably through checking out the wrong model of bike, base engine in a different state of tune) so forget the HS4, the HS6 is the one.
skinart said:
And yes it does have a water jacket which can be left blank with plugs, but im actually going to run oil through it with a separte oil cooler just for that loop, it has to be better then air cooling it, i know its made for water and it is normally only around 15 psi, but im sure the housing can handle the 40 psi that this oil pump makes, its worth a try thats for sure.
The housing probably can, but you'll need to change the seals I reckon - not only for the pressure but for the different fluid.
skinart said:
Im gunna check out ebay for one of those SU's that you have mentioned, unless you know of a good sorce of them? Or are they stil available new?
They are still available new but are not cheap. Ebay's probably a good bet. Time was when you could walk into any scrapyard and pick up as many as you wanted... Burlen Fuel Systems are the people for all stuff SU-related.
Yah if you go to Garrett's website its the smallest turbo available that they make, its an awesome little thing, and for $499 U.S its a bargain!
www.turbobygarrett.com/turbobygarrett/catelog/Turbochargers/GT12/GT1241_756068__1.htm
sorry I dont know how to make a link like you did in your above post.
Change the seals in the turbo for the oil through the water passage? As far as I understod its just a cast water jacket that has only one in and one out, i didnt think there was an seals in this water jacket area, just a hollow cast section that surrounds the centre section of the turbo, could be rong thoug ive never cut a turbo in half to check lol, this is from what I have kinda seen when I look into the jackets, someone please correct me if i am rong.
DAMN those things are expensive new! Found a couple on ebay I should be able to grab for under $50, Il keepan eye out for the number 6 though!
Is this the number 6?
http://cgi.ebay.com/ebaymotors/ws/eBa
Looks like its in good shape and shuld go for alot cheaper then new i would hope
Chad
www.turbobygarrett.com/turbobygarrett/catelog/Turbochargers/GT12/GT1241_756068__1.htm
sorry I dont know how to make a link like you did in your above post.
Change the seals in the turbo for the oil through the water passage? As far as I understod its just a cast water jacket that has only one in and one out, i didnt think there was an seals in this water jacket area, just a hollow cast section that surrounds the centre section of the turbo, could be rong thoug ive never cut a turbo in half to check lol, this is from what I have kinda seen when I look into the jackets, someone please correct me if i am rong.
DAMN those things are expensive new! Found a couple on ebay I should be able to grab for under $50, Il keepan eye out for the number 6 though!
Is this the number 6?
http://cgi.ebay.com/ebaymotors/ws/eBa
Looks like its in good shape and shuld go for alot cheaper then new i would hope
Chad
skinart said:
Yah if you go to Garrett's website its the smallest turbo available that they make, its an awesome little thing, and for $499 U.S its a bargain!
www.turbobygarrett.com/turbobygarrett/catelog/Turbochargers/GT12/GT1241_756068__1.htm
sorry I dont know how to make a link like you did in your above post.
www.turbobygarrett.com/turbobygarrett/catelog/Turbochargers/GT12/GT1241_756068__1.htm
sorry I dont know how to make a link like you did in your above post.
Beautiful, thanks for that link. (To see how to make a link quote my previous post and look at the [url] [/url] codes.)
skinart said:
Change the seals in the turbo for the oil through the water passage? As far as I understod its just a cast water jacket that has only one in and one out, i didnt think there was an seals in this water jacket area, just a hollow cast section that surrounds the centre section of the turbo, could be rong thoug ive never cut a turbo in half to check lol, this is from what I have kinda seen when I look into the jackets, someone please correct me if i am rong.
Just me covering all possible bases since I haven't looked inside it either
If there are seals they will probably need changing. If there aren't, no problem. skinart said:
DAMN those things are expensive new! Found a couple on ebay I should be able to grab for under $50, Il keepan eye out for the number 6 though!
Is this the number 6?
http://cgi.ebay.com/ebaymotors/ws/eBa
Looks like its in good shape and shuld go for alot cheaper then new i would hope
Chad
Is this the number 6?
http://cgi.ebay.com/ebaymotors/ws/eBa
Looks like its in good shape and shuld go for alot cheaper then new i would hope
Chad
Yes, but it's a very old one and the choke linkage is missing. It looks beautiful but I wouldn't assume it won't need rebuilding. I'd go for a more recent one, still with the big nut on the bottom (which is for adjusting the mixture) but with the "nut" on top in black plastic rather than brass (it's only for fingers, so plastic isn't a problem) and a nylon tube linking the bottom of the float chamber to the jet - with that setup you can change the orientation of the float chamber relative to the carb body, which gives you more freedom of choice over what angle the carb is mounted at (ideally they go horizontal, but it's very common for them to be at a slight angle like that one is because it makes them easier to fit in).
Ive been doing a little more research and have noticed that most draw through systems have started with larger bore carbs and have made excelent top end power but idle and midrange have been very erratic, and not very streetable. Then they have put it restrictors to bring the venturi size down and although they have lost top end power they say that idle and midrange is very smooth and very responsive.
The bike comes stock with twin 38mm CV carbs, I may split the pair and maybe even try one of those. These bikes make on average around 48 whp, and although it would be nice to make around 100 - 110 which im sure it could with a very minimal amount of boost, I would be much happier to make 80 whp and have it super smooth.
Good thing is I have a few different carbs I can try and a dyno next to my work bay, so within a few hours I should find out exactly which carb gives the best all round performance.
Exhaust manifold will be built tommorow, so il soon be posting pics on the project.
Thanx for everyones help.
Chad
The bike comes stock with twin 38mm CV carbs, I may split the pair and maybe even try one of those. These bikes make on average around 48 whp, and although it would be nice to make around 100 - 110 which im sure it could with a very minimal amount of boost, I would be much happier to make 80 whp and have it super smooth.
Good thing is I have a few different carbs I can try and a dyno next to my work bay, so within a few hours I should find out exactly which carb gives the best all round performance.
Exhaust manifold will be built tommorow, so il soon be posting pics on the project.
Thanx for everyones help.
Chad
Edited by skinart on Tuesday 8th August 03:12
skinart said:
Ive been doing a little more research and have noticed that most draw through systems have started with larger bore carbs and have made excelent top end power but idle and midrange have been very erratic, and not very streetable. Then they have put it restrictors to bring the venturi size down and although they have lost top end power they say that idle and midrange is very smooth and very responsive.
Yeah, that's a classic carb size compromise situation
It's less of a problem with an SU (or other constant-depression type carb) as they automatically vary the effective bore size to suit the airflow, but it still needs to be considered. skinart said:
The bike comes stock with twin 38mm CV carbs, I may split the pair and maybe even try one of those. These bikes make on average around 48 whp, and although it would be nice to make around 100 - 110 which im sure it could with a very minimal amount of boost, I would be much happier to make 80 whp and have it super smooth.
38mm = 1.5" = SU HS4.
As you no doubt know carbs have an easier time of it on a forced-induction setup because the airflow through them is more or less steady, so they are supplying mixture all the time as opposed to just when the inlet valves are open; also the lack of transient effects helps. My rule of thumb for an initial carb size choice is to look at the size used on a cooking-tuned, single-carb four-pot giving roughly the same amount of power as the projected conversion... 100bhp suggests HS6 but you don't drop too far before you're into HS4 territory.
While Japanese CV bike carbs don't have the simplicity and ease of fiddling of an SU, given that you already have some CV carbs of a sensible kind of size I must say I would go with your start-with-what-you've-got approach if I was doing the same conversion myself.
skinart said:
Good thing is I have a few different carbs I can try and a dyno next to my work bay, so within a few hours I should find out exactly which carb gives the best all round performance.
There is no substitute for a dyno for making accurate comparisons... but where drivability is concerned, because subjective factors ("feel"
are involved, one would ideally conduct street tests as well. skinart said:
Exhaust manifold will be built tommorow, so il soon be posting pics on the project.
Looking forward to seeing them!
Well I have both a 38 and 42mm CV carbs from other bikes that I can try, and will go from there after seeing and feeling the results.
After calling everyone in town and across the pond I could not find anyone that make the GT12 inlet weld on exhaust flange or the exhaust exit flange, so I had to take it to the local laser cutter to get them made, so I now have 10 of each so if you know of anyone that needs any I got them lol.
Also orderd a bunch of 90's and 180's alum piping for intake, got them from burns stainless, wow they are pricey, we normally get all our inlet piping for half the price for 4 times as much, but no one else carries 1'3/8 lol tiny little plumbing.
Hey whats your thoughts on running the intake plumbing, should I run it along the side of the engine where air can pass around it, or should I run it over the top of the engine? Im thinking about keeping the fuel from condensing and not sure if the abient air will be to much cooling for it and make the fuel pool, where along the top of the engine it will stay alot warmer. Again looking at some of the draw through systems in some old turbo books and alot have used dual core piping and actually run water through it to keep the fuel from condensing, but then again you dont want to intake charge super heated where lots of hp is lost, so kinda gotta find the happy medium.
I wish they had an EFI model of this bike, im so glad we dont do to many carb projects lol
And actually the bike CV carbs and very easy to fine tune, I have never worked on a car SV carb but the bike carb is very very easy to tune and work on. The needles are very lean from the factory so a quick couple of shims under the needle make richining up the midrange very simple, and pilot jet can be changed in no time at all, and although it dosent have an adjustable main jet, its very quick and easy to change and we have al sizes in stock. And if thats not enough fine tuning I will grab a dynojet jet kit with a 5 clip adjustable needle.
Chad
After calling everyone in town and across the pond I could not find anyone that make the GT12 inlet weld on exhaust flange or the exhaust exit flange, so I had to take it to the local laser cutter to get them made, so I now have 10 of each so if you know of anyone that needs any I got them lol.
Also orderd a bunch of 90's and 180's alum piping for intake, got them from burns stainless, wow they are pricey, we normally get all our inlet piping for half the price for 4 times as much, but no one else carries 1'3/8 lol tiny little plumbing.
Hey whats your thoughts on running the intake plumbing, should I run it along the side of the engine where air can pass around it, or should I run it over the top of the engine? Im thinking about keeping the fuel from condensing and not sure if the abient air will be to much cooling for it and make the fuel pool, where along the top of the engine it will stay alot warmer. Again looking at some of the draw through systems in some old turbo books and alot have used dual core piping and actually run water through it to keep the fuel from condensing, but then again you dont want to intake charge super heated where lots of hp is lost, so kinda gotta find the happy medium.
I wish they had an EFI model of this bike, im so glad we dont do to many carb projects lol
And actually the bike CV carbs and very easy to fine tune, I have never worked on a car SV carb but the bike carb is very very easy to tune and work on. The needles are very lean from the factory so a quick couple of shims under the needle make richining up the midrange very simple, and pilot jet can be changed in no time at all, and although it dosent have an adjustable main jet, its very quick and easy to change and we have al sizes in stock. And if thats not enough fine tuning I will grab a dynojet jet kit with a 5 clip adjustable needle.
Chad
Edited by skinart on Wednesday 9th August 05:24
skinart said:
Hey whats your thoughts on running the intake plumbing, should I run it along the side of the engine where air can pass around it, or should I run it over the top of the engine? Im thinking about keeping the fuel from condensing and not sure if the abient air will be to much cooling for it and make the fuel pool, where along the top of the engine it will stay alot warmer. Again looking at some of the draw through systems in some old turbo books and alot have used dual core piping and actually run water through it to keep the fuel from condensing, but then again you dont want to intake charge super heated where lots of hp is lost, so kinda gotta find the happy medium.
I'm going to reserve judgement on this one until we know how you're doing as regards charge distribution between the two pots. If it was a 360 deg parallel twin I'd go for over the top of the engine, but if you find it desirable for charge distribution to have an asymmetrical inlet system, then round the side of the engine may be the neatest method. You could always lag it if there's a problem.
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