Home made GSXR throttle body conversion

dynofiend · Post by **dynofiend** » Sun Apr 19, 2009 9:01 pm

Hi guys,

Thought some of you might be intrested in a little side project I have going at the moment. GSXR throttle bodies on a modified 1.6 manifold.

Careful shaping of the runners has meant ive been able to achieve a completely smooth transition from hose joiner to manifold, which is often the achilles heel of most home brewed ITB setups.

No idea when ill eventually get the things fitted, as I also want to combine them with a heavily skimmed head to raise compression and retard the cam timing. Will also be advancing the ignition and running as high octane fuel as I can get away with without knock. Probably also a nice flowing header and no cat for better exhaust flow.

Unmodified runner

Half modified runner

Finished, excuse the ultra long stacks, they will need to be shortened!

Can see the transition from hose to manifold as a thin silver line just after the blue bit on this pic, no step at all.

Anyone with good contacts to standalone ECU suppliers greatly appreciated

brownie · Post by **brownie** » Sun Apr 19, 2009 9:32 pm

Thats looking pretty,cool,Keep us informed,Whats the thottle body setup worth to buy out of interest?
I know the japs do this sort of setup .Quite common from what i've seen.

poison · Post by **poison** » Sun Apr 19, 2009 11:24 pm

Nice, does the length or I guess distance from throttle body to inlet valve make a difference to where the power is? I know on V8's the risers under the carbs are of a critical lenght for where the power comes in?

One thought, you've probably got this covered, but if not you will need to make a solid bracket or the carb's will shake themselves off in no time.

There was a guy on TradeMe selling a manifold and set of MX5 carbs for ages. I have some Japanese MX5 mags one of them has some pictures of carbs and manifolds, if useful to you I can scan them and post the pcitures.

Euen · Post by **Euen** » Mon Apr 20, 2009 10:59 am

Nice, does the length or I guess distance from throttle body to inlet valve make a difference to where the power is? I know on V8's the risers under the carbs are of a critical lenght for where the power comes in?

Definitely. From memory the longer the runner, the higher up the rev range band you get the impact.

This is one of the headaches I have at the moment. I have a set of Toyota throttle bodies sitting on the bench at the moment but the engine bay on the TG tapers which limits the runner length for number 1.

The other thing I want to research a bit is the optimum injector location. The BP head has the injector on the head but the Toyota arrangement has the injector out on the runner, just on the inside of the throttle body.

Dyno, they are looking good. I saw your thread on Miata.net as well. I agree with Poison about some form of support underneath. Looking at you photos it doesn't look as if it would be easy though. There are plenty of mounting points on the block though.

I can't see the injectors in your photos, are you just using the Mazda injectors in the head?

Cheers

Euen · Post by **Euen** » Mon Apr 20, 2009 11:07 am

Just as an aside, there is nice set of throttle bodies on Trademe at the moment.

http://www.trademe.co.nz/Trade-Me-Motor ... 875361.htm

E

dynofiend · Post by **dynofiend** » Mon Apr 20, 2009 8:11 pm

Cheers for the comments.

Runner length is quite important. In a nutshell though, the longer, the better. My runners are about 12" long so theoretically will be producing peak power at or around the mx5 redline. Perfect

Ill be making a bracket for sure, already started on one infact but would like to use the original bracketry on the block if possible. But the carbs wont shake themselves off, cos theyre throttle bodies not carbs :p

Ill be using the standard mazda injector position. Using the bike TB arrangement would need a custom fuel rail making (the gsxr has no return line). Also, the only advantage to injectors further away from the valves than from standard, is for use at higher rpms. I wont be running much higher rpms than standard so I dont really need to extra distance to allow for better mixing.

Cost of the setup obviously depends on how much you can source the parts for. I have a whole spare head, and this setup, and have probably spent about $350 ish on everything so far. The big cost will be the ECU though, which is something im putting off until ive played around with everything else.

Ideally ill also be making an airbox to enclose the stacks incorporating an air filter, but making this so it becomes 'open trumpet' at the flick of a lever from inside the car. Means I can cruise at low noise levels, and open up the TBs for optimum power and noise

Growler · Post by **Growler** » Wed Apr 22, 2009 12:51 pm

And if you are smart, you could make runner lengths adjustable!

dynofiend · Post by **dynofiend** » Wed Apr 22, 2009 6:40 pm

Well thats the beauty of hose connector setups

Euen · Post by **Euen** » Fri Apr 24, 2009 11:12 pm

I got it wrong. Seems that a longer ITB runner is better at lower rpm. I've just been doing a bit more reading on it but there is still a lot more to do. Sorry if I caused any confusion

Cheers
Euen

poison · Post by **poison** » Mon May 04, 2009 5:40 pm

OK I have to ask, what's the point of individual throttle bodies? I have to
assume you keep the EFI, if so how to you measure the airflow? If you're not
keeping the EFI is there any benefit? I guess you would at least get awesome
airflow.

sprsta · Post by **sprsta** » Mon May 04, 2009 5:53 pm

with a map sensor an earlier post hiden under one of the pictures said

"Anyone with good contacts to standalone ECU suppliers greatly appreciated "

sprsta · Post by **sprsta** » Mon May 04, 2009 6:01 pm

just a thought would this work with toyota 4age quad throttles and could retain the afm using the plenum looking thing that feeds them if you didnt want to fork out for a standalone dont see why it wouldnt

poison · Post by **poison** » Mon May 04, 2009 6:25 pm

Isn't the whole benefit in that you don't need to use a plenum? It would
look great seeing quad carbs sitting there. You could put the map sensor
half way down one of the risers, or even between 2 of them to get better
averaging. Mind you putting a map sensor in a high velocity area increases
the risk of misreading as the air flowing past can cause a vacuum in any
small pipe on the side.

sprsta · Post by **sprsta** » Mon May 04, 2009 6:43 pm

good point might also be abit of fun with the fpr

Habanero666 · Post by **Habanero666** » Mon May 04, 2009 7:10 pm

Love this design, and those headers

2low2c · Post by **2low2c** » Mon May 04, 2009 8:00 pm

all after market ecus use tps not map sensors on itbs becuse there is not a steedy enough vacuum and vacuum is to low. on a road car with a brake booster all the runners need to be linked after the trottle bodys for the brakes but this dosn`t give enough signal for a map sensor.

WideOpenThrottle · Post by **WideOpenThrottle** » Mon May 04, 2009 8:04 pm

Looks like you cant turbo this set up or route in cold air???

Habanero666 · Post by **Habanero666** » Mon May 04, 2009 8:18 pm

Cold air done easy! pull out the right hand indicator! ( track use only).

Thats true 2low2c.

2low2c · Post by **2low2c** » Mon May 04, 2009 8:39 pm

you can turbo itbs nissan gtr and gtir both run itbs.

WideOpenThrottle · Post by **WideOpenThrottle** » Mon May 04, 2009 8:47 pm

ITBS??? [induction throttle body system]? [irate thrasher biting someone]?? excuse my ignorance

Habanero666 · Post by **Habanero666** » Mon May 04, 2009 8:52 pm

ITB's = Independent throttle bodies

WideOpenThrottle · Post by **WideOpenThrottle** » Mon May 04, 2009 8:59 pm

Cheers Hab!

Habanero666 · Post by **Habanero666** » Mon May 04, 2009 9:04 pm

No probs, wideopenthrottle. hahaha, I stuffed up it's actually "individual throttle bodies"

Euen · Post by **Euen** » Mon May 04, 2009 9:20 pm

They can also be known as IRTBs, Individual Runner Throttle Bodies.

The 4AGE (AE111) ITBs take the brake booster off a single intake and the crank case breather off another (intakes 1 and 4). Vacuum for the FPR is fed off No.1 and there is another small vacuum line off No 4 which drives an actuator on the throttle which I assume to be some kind of idle speed control. There doesn't appear to be a feed for MAP.

If you need a MAP feed, most suggestions are to link the vacuum from all 4 intakes to get a more consistent vacuum reading.

One of the advantages of ITBs is that they allow you to tune the intake length for the rev range you want your peak power at. They also regarded as being more responsive than a single throttle body with a plenum chamber. The other thing in their favour is that they sound absolutely brilliant.

On the downside, they can be a pita to tune a they all have to be balanced and it doesn't take much to knock them out of tune. You would also need an after market ecu to run them on a MX5.

Poison, yes they do retain the injectors, but depending on the type of manifold you get they can also allow you to move the injector further away from the head, allowing better atomisation of the fuel before it enters the combustion chamber.

Post by **jif** » Mon May 04, 2009 11:17 pm

you don't need the plenum, but then if you're running them 'naked' you'll either need carbs or a ECU that can handle the funky non-linear throttle-airflow-MAP response. Also the MAP signal can be pretty jagged, I understand. And putting a filter over the throat messes with the airflow. And then theres balancing flow between them. Nothing's easy

If you have the plenum, there's some issues with sizing/ tuning it ... Chris Chu in Canada did a lot of messing around with this.

There's a BRG running around on the North Shore with what sounds like IRTBs ... it's the one with the dirty fart blast mark around the tail pipe

Sounds cool, though any turbo would leave it sucking dust thru those pretty IRTBs

So the dream setup has just changed to an IRTB'd engine, ... with a turbo... on a nice v8. bugger !

Jeff (now with v8 powah)