GSXR slingshot air intake pipes, did they do anything?

[Upshotknothole]

Putting fairings back on to a GSXR 750 for the first time in over 15 years and it's kinda weird. Trying to remember, did the air intake pipes from the upper fairing do anything other than help cool the area around the carbs? This is a 750N(us market, same as the M), and the last time I ran fairings was on a 750J with flatslides and I honestly can't remember if I still had them or not on that bike. There's a few on Eblag for about $100 a set, but if not needed I'll skip them and focus more on getting everything painted to match.

[Gixer1460]

Whether they did anything is debatable outside of Suzuki R&D but the theory goes like this - on a bike with a fairing the area inside it and around the carbs is a low pressure zone which messes with carb function (how much is anyone's guess!) The nose on a fairing exhibits high pressure and possibly 'venting' some of that high pressure 'ram air' into the inter fairing low pressure zone reduces its effect! On the flip side many, many bikes with and without fairings use carbs successfully so maybe its all hype and marketing bollux!

[Upshotknothole]

Thanks, suspected as much. They can wait for the time being then.

[Crass]

Well one of the pipes directs cool air onto the cylinder head area,  so on a bike with no water cooling and relying to a certain extent on air cooling I would regard that as advantageous. Otherwise it it trapped behind the large headstock casting receiving some air which has previously heated up by passing through the oil cooler. The second pipe delivers cool air to the airbox, which otherwise has to get its supply from the hot air blown off the engine. Again, I would expect that to be beneficial.

Edited August 5, 2021 by Crass

[Joseph]

Indeed @Crassi would side with you on that theory.

On my 1216 bike (semi faired, these air tubes not fitted), i have a sump oil temp sender and a cylinder head temp sender and there is around 10°C difference between the 2. 

I could try fitting the head cooling tube maybe that could help, it could give an answer as to it's efficiency.

I think general consensus is that if the factory deemed that the technical need justified the extra cost, it is of use on the bike

 

Edited August 5, 2021 by Joseph

[Upshotknothole]

This is a mostly stock 750 with pods on the carbs. The tube that plugs into the cross member on the frame and blows over the top of the carbs I always suspected was more for cooling the area around the carbs than anything. Airbox I’d think would be drawing from the cooler air around the rear wheel/battery area. But like I said, it’s been years since I’ve ran full plastics. 

[TonyGee]

i'd go with the pipes, better to be on the cooler side than the hotter side.  it was designed that way. 

[Joseph]

On W bikes in standard form the "carb pipe" exits just around the intake boot of the airbox

[Crass]

22 hours ago, Upshotknothole said:

This is a mostly stock 750 with pods on the carbs. The tube that plugs into the cross member on the frame and blows over the top of the carbs I always suspected was more for cooling the area around the carbs than anything. Airbox I’d think would be drawing from the cooler air around the rear wheel/battery area. But like I said, it’s been years since I’ve ran full plastics. 

No, I don't think that's correct. The pipe feeds into the cross member and there are exit holes on the rear side of it. The airbox top butts up to the underside of the cross member, so the air does not reach the carb tops but rather flows along the top of the airbox and feeds to the intake at the rear. It gives a flow of direct, cool air to the airbox inlet which would otherwise have to rely on hot air which has been blown back off the engine. Even with the airbox removed you are still getting a flow of dense, cool air to the pod inlet area although things will not be working quite as they were designed to do with the airbox removed. 

Edited August 6, 2021 by Crass

[Oilyspanner]

A bit late on this one.....did some thinking on this one a while ago : particularly on a faired bike, at speed you have high pressure on forward facing surfaces,  but down the sides there's a drop in pressure. At high speed the engine requires large amounts of air, which further lowers the pressure within the bodywork..this would muck up fuelling that seems fine on a static dyno, so any air that can be fed from the high pressure area towards the air intake is a good thing..it lessens the potential losses at high speeds.

Engines don't drag air in, they lower the pressure within them and it's the far higher surrounding pressure that rushes in to balance the pressure imbalance...if the surrounding air pressure is lowered, engine efficiency drops too.....so the tubes do help !

[Upshotknothole]

Thanks for all the replies. Got a set in the mail coming from Canada that should be here soon. As soon as I get all the body work back on this bike, it’s back to repairing all the damage the thieves did to my 7/11 and no more talk of stock bikes. 

[Gixer1460]

9 hours ago, Oilyspanner said:

A bit late on this one.....did some thinking on this one a while ago : particularly on a faired bike, at speed you have high pressure on forward facing surfaces,  but down the sides there's a drop in pressure. At high speed the engine requires large amounts of air, which further lowers the pressure within the bodywork..this would muck up fuelling that seems fine on a static dyno, so any air that can be fed from the high pressure area towards the air intake is a good thing..it lessens the potential losses at high speeds.

Engines don't drag air in, they lower the pressure within them and it's the far higher surrounding pressure that rushes in to balance the pressure imbalance...if the surrounding air pressure is lowered, engine efficiency drops too.....so the tubes do help !

I said that up top - but no one was listening LOL!

[Upshotknothole]

I’ve got tubes! 

[Otatts]

Interesting read! I’d always wondered of the cooling tube effectiveness. I’m getting tubes welded through my tank (I’ll be honest…more for looks than anything else) ,  fed  from the windshield vents via some hose ah la yoshimura suzuki America race teams. 
I had debated whether to have them exit on top of the head for cooling or at the carbs for air feed. 
from what I could tell it was for carbs. Bit different from race bikes but I guess the theory is the same. 
 

Edited August 15, 2021 by Otatts

[Joseph]

On 8/11/2021 at 10:06 AM, Gixer1460 said:

I said that up top - but no one was listening LOL!

I'd say that my "if the tight ass factory spent the money, it is of use" is worthy of any physics explanations 

Edited August 15, 2021 by Joseph

[Upshotknothole]

11 hours ago, Otatts said:

Interesting read! I’d always wondered of the cooling tube effectiveness. I’m getting tubes welded through my tank (I’ll be honest…more for looks than anything else) ,  fed  from the windshield vents via some hose ah la yoshimura suzuki America race teams. 
I had debated whether to have them exit on top of the head for cooling or at the carbs for air feed. 
from what I could tell it was for carbs. Bit different from race bikes but I guess the theory is the same. 
 

Yup, those were for air to the airbox, airtech still makes the upper fairing with the intakes where the mirrors would go.

[Otatts]

@Upshotknotholeyeah it’s where I got mine from along with the carb side covers.  Keen to see if it makes any notable difference 

[Upshotknothole]

5 minutes ago, Otatts said:

@Upshotknotholeyeah it’s where I got mine from along with the carb side covers.  Keen to see if it makes any notable difference 

Yosh seemed to think it helped. If anything it’ll look really trick. 

[Otatts]

23 minutes ago, Upshotknothole said:

Yosh seemed to think it helped. If anything it’ll look really trick. 

Yeah that’s 100% why I’m doing it 

[Upshotknothole]

Finally installed them tonight. Even more crap to remove to work on it now. I think I’ll get rid of all of the breathers going from the carbs to the small cleaner box later. Also, has anyone see these rubber inserts in the back of the cross member before? I can’t find them in the parts diagrams. 

[Crass]

No, mine hasn't got those rubber inserts.