tfreer85

Okay so I like just about everyone else has a fetish for ITB's, but realize the Harrop and Kinsler are way to $$$ for the HP gain on a street driven vehicle. So this leads me to the build/fabrication part of things which is much more fun anyways. In my search for inexpensive ITB setups I came across these guys
http://www.extrudabody.biz/servlet/t...sh-45mm/Detail

The only problem is they only carry 45mm TB's, where it seems like Harrop and Kinsler are both in the +50mm range. My motor is a '00 LS1, will I have any flow issues with the 45mm? Will it hurt my performance? I'm not too concerned if I loose a little HP as I will already have too much for my car.

Thanks for any help, concerns, or hardcore math!

Tyson

P.S. Its an LS1 T56 swap into a 72 Datsun 240z

chuntington101

if you are ok with 45mm take a look at motorbike carbs/ITBs! they are really compact and amzing pieses of kit.

if not have a look for guys making throttle bodies. these are a company in the UK (its the first i came across so pardon the prices! lol) http://www.webcon.co.uk/alpha/thrott...price_list.htm

should be a very interesting project mate. please keep us updated!

Chris.

FieroZ34

iTrader: (1)

If you have the tools and the knowledge, I'd suggest going one of two routes:

1) Motorcycle throttle bodies. They are pretty easy to find, REALLY cheap (Under $200 per side), easily fabricated/adapted, integrate fuel injectors/fuel rail, already have the throttle shaft setup, and they are available in a wide range of perfect sizes.

2) Small throttle bodies from a import or slow domestic. Most automotive 4cyl use like 40-50mm throttle bodies, so just buy 8 of the same kind. It'd take some precision fabrication to get the throttle shaft connecting all 4 per side, but they'd be hella cheap from a junkyard. Problems in that they don't integrate injectors, so you'd need to find a place to put bungs, or just build some mounts to put them at the air horn.

I think the extrudabody pieces are a bit overpriced, when you can pay ~$100 for the exact same thing off of a motorcycle.

chuntington101

great idea on the small domestic throttle bodies!!

i bike carb/injection has really taken of here in the UK. loads of people are starting to runthem as a) they are often easier to fit in the tight engine bays we have over ehre and b) they are soooo cheap! lol

thanks Chris.

briannutter

Would you want to put a 1.771 mm restictor in front of your 2.02 valve? You will need to subtract the area of the throttle blade itself in the wot position, then make sure the net square inches of the bore is at least as big as the venturi below the valve (which is around 85-90% of the size of the valve). Most of the people I know running ITB's run WAY bigger area than their valve sizes.

tfreer85

I've looked into these before, searching on ebay and finding 2 sets in good condition are hard to do. Also, are their brands I should be looking? Suzuki, etc. etc. Are there other considerations, or things I should look for with the motorcycle ITB's?

This brings up the next question, what is the ideal or MINIMUM size I should be looking for?

koolrayz

iTrader: (26)

subscribing

FieroZ34

iTrader: (1)

Ya you'll have to check eBay a few times a week, but they are on there. And the good condition part isn't really important, so long as they aren't damaged, because you will be cleaning them I'm sure anyways. I'd figure out what the optimal size for you is (That I can't help you with), then find the bikes that have that size. Then just hunt eBay for them. But no one brand is superior to the other in quality or performance of the TB unit, they are just different in sizes.

The only other consideration I'd look for is where the fuel injectors are located. Some companies like Kawasaki still put the injector right after the throttle blade. Whereas Yamaha is starting to use dual injectors, one after the plate, and one above the air horn. For your project I'd find one that places the injector after the throttle plate, as that will make it easier and the TBs will idle a lot better. You will probably end up needed to use the motorcycle fuel injector, but I'm not so sure this is a bad thing. Any ECU can control that injector just as well as it can the LS1 ones. They are no different in form, just grounding the circuit to open it. But I'm not sure what size the bike injectors are, you'll need to find that out as well and make sure they are right for your engine.

I don't think a standard automotive fuel injector will "bolt right into" a motorcycle rail. But it'd be worth it to double check that!

tfreer85

Couldn't the injector housing be modified for an automotive one? It doesn't "seem" like it would be too difficult to change out. But like you said need to research how the motorcycle injector compares to the car injector flow wise. If they flow the same I don't see why the motorcycle injectors wouldn't work. I saw the yamaha's with the dual injectors started thinking forced induction but slapped myself back into reality. So then the big question that still remains, is figuring out the flow/size of the individual ITB's then going from there on picking brand/type of ITB's. Based off of looking at both the Harrop and Kinsler +50mm plus will be ideal. Anyone out there be able to do the math for me or have the formula or have any books to help me figure it out?

Thanks guys,

Tyson

chuntington101

the bike guys run twin injectors per cylinder cos it offers better fuel air mix than with a single injector. this is cos the fual has more time to mix properally with the air. it all leads to more power!

also i heard bikes run staggerd injection, they fire twice, once on the like a normal injector and once when the valve is shut. this eman they can run small injectors and still get the fuel dilivery.

thanks Chris.

FieroZ34

iTrader: (1)

Kind of. The Yamaha uses dual injectors, in a Dual Stage Fuel Injection. Thus the small Primary injectors are mounted between the throttle plate and intake valve, as close to the intake valves as possible (Spraying right on them). Thus at idle, and low-mid range RPM levels, the bike runs smooth and has good throttle response. However once the throttle is opened up a bit, and the bike travels through the 7,000-8,000rpm spread, the primary injectors phase out, the air horns slide down the intake runner to shorten runner length, and the much larger secondary injectors phase in. These are located at the very top of the runner, right below the sliding air horns. Thus as rpm reaches 7-8, the airflow is great enough and has enough velocity that the HUGE amounts of fuel will mix very efficiently, and will get into the cylinder very quickly. But the secondary injectors are too big, and too far up the intake tract to provide good idle, low rpm performance, and throttle response. It really gives the best of both worlds, a bike that idles like a Cadillac, but screams up high like a Formula One car. Just another part of the technological advancement that's enabled the bike to have just as much low end torque, throttle response, and gas mileage as the 7,000rpm redline Buell's, but then come alive and brutally scream to the 17,000rpm redline. It's quite a ride!

This image is of the 1000cc R1, but the 600cc R6 has a very similar setup.

chuntington101

FieroZ34, the same thing has been done on loads of clubsport cars over here for the same reason! MOST engines give a good power and torque increase over sinbgle injectors.

thanks Chris.

FieroZ34

iTrader: (1)

I agree most cars can handle a single injector per cylinder. However once you get into really large sizes, typically for boosted applications, they aren't able to open and close as fast as the PCM needs them to. Since today's injectors are very good, most automotive applications will suffice on a single without any idle or low-speed issues. However on the sportbikes, the RPMs they turn are so high, and the volume of air is so great, that the large injectors will hurt idle and low speed performance. Particularly if you are at 2,000rpm, and go WOT, a lot of bikes will stumble. However the dual stage injection allows you to go WOT at 2,000 as smooth as an LS1.

chuntington101

i was saying that twin injection is a good idea.

i have seen back to back testing of tiwn vs. single setups and on all (but the rover K-series engine) twin injectors have been better. these tests where done on the same engines running fine on a single, but the twins netted more power!

Chris.

Wnts2Go10O

iTrader: (12)

not an ls1 but heres a buddys car converted http://ultimatecarforum.com/smf/index.php?topic=2056.0

Beaflag VonRathburg

iTrader: (176)

I've been considering this for a long time. I'm going to have to take some of these hints...