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Draw through: distance carb to turbo?


Stephtell

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'Evening!

 

I'm currently running a modified Super E on my draw through GSX but will convert it to run a Mikuni HSR 45 this winter.

Now I'm thinking that the closer the carb is to the turbo, the better it'll be as far as response goes...what says you?

 

Since I'd have to make a new adapter to fit the HSR I might as well make it a lot shorther than the one currently fitted...this will move the carb inwards so it sits underneath the fueltank.

Might not be the pretiest but I'm thinking it should improve the lower RPM running...?

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LOL

 

Thanks for that! I thought it should improve things somewhat, glad to have confirmation on that!

 

The previous owner couldn't get the HSR to deliver enough fuel for 300 BHP, hence fitment of the S&S but as far as I'm aware 300 BHP should be no problem for the HSR?

 

B.t.w. how did you get to 1460cc??

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2 hours ago, Stephtell said:

LOL

Thanks for that! I thought it should improve things somewhat, glad to have confirmation on that!

The previous owner couldn't get the HSR to deliver enough fuel for 300 BHP, hence fitment of the S&S but as far as I'm aware 300 BHP should be no problem for the HSR?

B.t.w. how did you get to 1460cc??

There isn't a snowball in hells chance of any HSR fueling 300hp! The float bowl is massively too small and pressure needed to fill it and keep up with demand is so excessive that it floods at anything other than mid range and up! 250 'ish hp with nitrous assist is about the only way i've seen of getting close!

If - as the other poster noted - it is a Rajay........it'll never flow enough air even with F flow bits - Sorry!

1460cc ? piece of piss.................... M O N E Y ! :D:D:D:D:D

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Well it's not a RayJay!

 

It's a Turbonetics T3/4 hybrid with a 48AR STG 3 turbine and 50E blower.

It's been dyno'd at 285 BHP at the rearwheel with the super E so around 300 at the crank.

 

As for fuelling: Sean from Big CC seems to think the 45 will easily do it if the fuelentry is properly modified?

You can also get floatbowlspacers although Sean reckons that won't work.

 

Thing is the 'E is massivly overfuelling right now so i want to combat that.

Won't a rising rate FPR sort things out?

Edited by Stephtell
added something
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I know Sean well and all through the 'Phil Wood' years with the Spondon Kat and he could never manage it then even using a 48mm version HSR (from memory) so don't know what will have changed? A rising rate FPR is usually a bit of a 'band aid' on EFI systems - never heard of a successful use with carbs. I'm guessing that dealing with non linear fuel pressure plus addition of boost pressure will give moderately unpredictable results?

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I spoke too sean multiple times in the past and he gave me good advice while buildin the kwaksuki

 

rising rate just won't work he has been there and binned that plan the carb wil flood.

he told me that on woody's cat the last 100 mtr on the strip was done with a shot of nos cause the problem with drawthrough on big ass hp is getting fuel in the floatbowl

he mentioned that a bigger floatbowl does not solved this problem

only thing you can do is order the seat and needle that allows you to get more fuel in the bowl faster

gert jan had a hsr on the turbonetics in the past mounted with a rubber you can easily order at mikuni

Edited by Leblowski
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13 minutes ago, Leblowski said:

I spoke too sean multiple times in the past and he gave me good advice while buildin the kwaksuki

 

rising rate just won't work he has been there and binned that plan the carb wil flood.

he told me that on woody's cat the last 100 mtr on the strip was done with a shot of nos cause the problem with drawthrough on big ass hp is getting fuel in the floatbowl

he mentioned that a bigger floatbowl does not solved this problem

only thing you can do is order the seat and needle that allows you to get more fuel in the bowl faster

gert jan had a hsr on the turbonetics in the past mounted with a rubber you can easily order at mikuni

Don't think gert jan bike went past 270 ish bhp

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No he did not indeed on his old set up I have seen 230 on the dyno at street or track don't know what GJG did after that.

Pascal installed the s&s and al the trick stuff after he bought it from gjg to get bigger numbers

 

Edited by Leblowski
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I have a HSR45 for the bike as well as all the fitting so could easily swap over, I prefer making my own bits though as I'd like to improve on what is already there.

I might stick the HSR back on for some low boost running around town untill I sort out the S&S properly.

 

Mind you, it's lots better already after fiddling with it!

Btw. the bike did do over 270 BHP

Edited by Stephtell
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I know but the bike didnt do 270 when it was owned by gjg as far as i know

so if you have all the bits just put it back but install a thunderjet to get midrange good 

changing the place of the carb wont change anything in how the bike runs on low rpm it al comes down to tuning 

there nothing wrong in how it was designed and installed by gjg

as they say Never change a winning team

Edited by Leblowski
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16 minutes ago, Stephtell said:

But this topic isn't about 'things the bike did when GJG had it' so who cares? :)

The bike has changed a lot since those day's!

Your asking questions obviously cause you want to improve things referring to how it was wich worked is perfectly right imho cause this can help you.

you ask questions we answer.

if you want to convert to efi check wizzy pop slingshot on here

 

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Think we have a misunderstanding with regards to the GJG bit, can't be arsed to explain but I misread an earlier post and two of our posts crossed so all is well! :)

I'm pleased to see people repsond to question asked and I appreciate all the input!

A thunderjet to get the midrange right?

On the Mikuni you mean?

 

I have one on the S&S but the S&S is overfuelling really badly so will need sorting:

 

It has MAHOOSIVE jets, 1 to 2 psi static fuelpressure, a Thunderjet and the accelerator pump 3 full turns out and the enrichener 2 turns out!

OVERKILL anyone? The fuell almost poured out the exhaust in liquid form...so to speak.

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Yes a thunder jet on the mikuni

when you use it you can use the main jet to tune between 3000 and approx 5000 rpm and the thunderjet to top off fuel at higher range this wil improve drivability on low speeds 

it gets smoother in that range

you just cannot get it smooth with just the idle and mainjet cause you need a mainjet as big as the emulsiontube when you have over 200 bhp then ridability in midrange is shit

thunderjet worked for me

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230 on about 10 psi 

i needed a 260 mainyet to get it rich enough under boost without thunderjet so it was riding like a highly tuned two stroke on of on of then fbm adviced me the thunderjet.

i experimented with different gasneedles also for a smoother ride wich helped out also it does make a huge difference

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With regard to the  2-stroke bit:

 

At the moment is stumbles and grumbles low down but as soon as it clears it's throat is picks up it's skirt and fuck's off like a scalded cat!

Good fun!

My concern is borewash due to the excess fuell and the risk of fouling the plugs.

 

Mind you, it does start on 102 now and idles without problems so already some improvement!

I've disabled the acceleration pump and adjusted the idlemixture, next step is to check fuelpressure as I believe it's flooding the carb.

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  • 3 weeks later...

The main problem with

HSR is not the size of float bowl. Increasing the size will not help as it's the flow into the bowl that's the restriction. It doesn't matter how big you make it, it'll still run low on big power if you can't supply the fuel. The first mod to do is REDUCE the needle valve size to 0.8mm and supply with 3-4psi fuel pump. You can reduce the restriction further by doing away with the tight fuel elbow into the bowl, replacing it with a straight connector. The standard needle is larger but will allow fuel to push past and overflow if you use a pump. My hsr42 will flow more than twice the original set up. At 4psi it will flow over 5 litres/min. 

Edited by Zepp
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Hi Stephtell,

Both Leblowski and I watched in awe when this bike was built and dragraced years back by master mechanic GJG. You seem to be a little annoyed that it gets recognised, but in fact you can be very proud you're the owner now (actually I'm envyous because you were smart enough to buy it!) and it's even been improved ever since. 

The reason Leblowski shows you old photos is that it could be the easy way to revert to original HSR as it ran great. On top of that, I have had the opportunity to ride Leblowski's Kwaksuki once, and if anyone can point you in the right direction its him.

BTW.... the original yellow was awful IMHO! Looks much better now.

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