R1 Carbs (lots of pics)

[VintageRice]

I drove mine all weekend in the rain. Was a little worried but my horns are so far up that no water got there. Running through deep puddles might change this though. I want to build a snap on "airbox" for winter for my carbs. Something with a small inlet that faces rear. That way theres no "driect shot" to the carbs for moisture.

 

(some) Snowmobiles use this type of airbox without filters. Just routes air though passages so water cant flow to the carbs.

[The Dat-side]

Finally! got to the end! (Skimming tho)

 

Now what's the difference between R1 and R6?

Size of the engine? Size of the carbs?

[datzenmike]

tristin, I was reading that properly tuned pipe lengths were actually cramming in enough extra air to make the equivalent of up to 3 PSI boost!!!! That's FREE untapped power that never goes out of tune, never needs re-building, or an inter cooler, oil supply, timing ... anything. Just waiting for someone to do some math and cut the pipes the right length.

 

There aren't many motors today that don't take advantage of proper runner length to tap into free power and torque.

[VintageRice]

tristin, I was reading that properly tuned pipe lengths were actually cramming in enough extra air to make the equivalent of up to 3 PSI boost!!!! That's FREE untapped power that never goes out of tune, never needs re-building, or an inter cooler, oil supply, timing ... anything. Just waiting for someone to do some math and cut the pipes the right length.

 

There aren't many motors today that don't take advantage of proper runner length to tap into free power and torque.

 

Post that article. Hows that even possible?!?! 3PSI??

[Ratty260z]

Finally! got to the end! (Skimming tho)

 

Now what's the difference between R1 and R6?

Size of the engine? Size of the carbs?

 

R1 is the 1 liter vs the 600cc on the R6, The carbs are probably the same size or close and mostly jetting difference, Most bike carbs are 36-38mm and others are about 40mm or 44mm on some I believe.

[72240z]

3psi of boost by most APROX formulas is like 30hp. On some motors I could see the proper intake making a 30hp difference. Not an L series because of the combustion chamber design but def in most modern motors, esp the larger ones .

[VintageRice]

I want a free 30 hp.......dont really believe it though. People try SOO hard to get 200 hp n/a out of a Ka24e. Some say its never been done. U mena to tell me the right size air horns will do it? meh.....

 

I'll believe it when I see it!!

[Tristin]

3psi of boost by most APROX formulas is like 30hp. On some motors I could def see the proper intake making a 30hp difference. Not an L series but def something like an LS motor.

 

Yeah, but the principles should still carry over. The L-series may be far less efficient compared to the LS-series when it comes to using that "3psi" of boost, but there has to be some benefit I would assume. Then again it could be negligible...

 

I doubt it though as Spudly is making decent power with only 5psi of boost with his turbo setup (I think that's his number). Regardless how you get a greater amount of intake volume... Whether its by turbocharger, supercharger, of intake runner length... 3psi is still 3psi.

[VintageRice]

All this PSI talk makes me want a slug..........

[72240z]

I edited my post before I saw your reply. Ya it carries over but the combustion chamber design in the L series heads are all pretty poor by todays standards. Modern heads have amazing swirl and flow characteristics where an intake mani will have a much greater effect. Coupled with low displacement you will def see less then optimal gains.

 

Believe it when you see it? Look up aftermarket vs stock LS series intakes. The fast series is claming over 30hp gain, you even get a gain adding an ls6 intake to an ls1. There are tons of examples. 3psi equiv is like super optimal but its def possible, again esp with larger motors that are flowing lots of air through modern design heads. Obviously engine size and head design are precursors.

[72240z]

His 5psi I bet if dynoed is close to 50hp gain over well running N/A. It always is aprox. The lower PSI do nothing but negate shitty flow. If you do that without brute force by flowing properly you can gain the same. Up to a certain point of course which here is arguable 3psi equiv lol.

 

Which is exactly why if you flow tune a turbo motor you get more power and efficiency at the same boost.

[datzenmike]

3psi of boost by most APROX formulas is like 30hp. On some motors I could see the proper intake making a 30hp difference. Not an L series because of the combustion chamber design but def in most modern motors, esp the larger ones .

 

Well normal air pressure is just under 15 PSI so in theory a turbo motor with 15 PSI boost should double the power. Half the boost (7.5 PSI).. half the power. Half of that half (3.75 PSI) or 1/4 the power. So on a 100 hp motor about 25 HP... BUT this is theoretical best. 3 PSI may be optimistic. Say half again or 1/8 of 100 HP. That's about 12 hp. To be fair 10 might be possible. Hell I'll take 10 free HP for absolutely no mods required.

 

Does someone know how much more power 3 PSI boost makes?

[72240z]

The rule of thumb is 1psi to 10hp. Things change that ratio one way or the other but its pretty widely accepted to making approximations.

[Tristin]

I should have explained my postion a little better, but I was on my phone waiting for my car to warm up so I could leave work.

 

72, I fully agree that something like the LS or any newer engine will see significantly more gains due to an increase in intake pressure over our 40yr old heads. Without reading what Mike did, I do not agree with his number or 3psi increase with just adding a couple inches to the runners. What I do know, is that there will be a sweet spot that will have a beneficial change based off your runner length, flange porting, air horn shape (if youre running them), plenum volume (which most arent running with this setup), etc. I doubt you will see 30hp change, but I would estimate you could easily see 5hp.

 

I do agree with your point that just changing intakes on cars can dramatically change their intake efficiency; I have seen it hundreds of times first hand. Many cars gain about 5-6hp by just changing from the stock airbox to a short ram intake and even more if using a true cold air intake. Ive even seen double digit increases just by getting rid of the stock crap airbox.

 

I would have to look at Mikes data to see where hes getting his numbers. Im sure I can still pull a few free ponies out of thin air (pun intended) by changing up my design.

[datzenmike]

The rule of thumb is 1psi to 10hp. Things change that ratio one way or the other but its pretty widely accepted to making approximations.

 

I dunnow..... By this a A 100 hp L20B would make 200 hp with only 10 PSI which isn't double the atmospheric pressure. (assuming that double the air makes double the power) By your reckoning running about 2/3 more air makes double the hp.

 

 

 

72, I fully agree that something like the LS or any newer engine will see significantly more gains due to an increase in intake pressure over our 40yr old heads. Without reading what Mike did, I do not agree with his number or 3psi increase with just adding a couple inches to the runners. What I do know, is that there will be a sweet spot that will have a beneficial change based off your runner length, flange porting, air horn shape (if youre running them), plenum volume (which most arent running with this setup), etc. I doubt you will see 30hp change, but I would estimate you could easily see 5hp.

 

Yeah the real world governs and 5 hp gain is more believable but if it does indeed give 7-10 hp I'll take that too. It's still basically free... well not free, it's available and going to waste if you don't use it.

[Tristin]

Its free in the aspect that were already making a custom intake to mount the carbs... might as well make it right so get the most out of it. This is all common practice in SMIM fabrication... What I do see happening though is that the gains are going to be almost negligible for most on this. Very few people port match their manifold, no one runs a plenum (except Spudly and his design is horribly inefficient), and no one is looking for flow data on the air horns they are installing.

 

Deciding to use 6in runners over 9in runners (or vice versa) would be beneficial, but I think the positives to that length wouldnt be seen since thats the only thing you're doing for your intake. Theres a reason that SMIMs are expensive... quite a bit of thought goes into them and that doesnt include the labor to put it together.

[72240z]

Its not a linear ratio Mike, they say it holds true within a small range up to about 14psi where power in theory is doubled. A 100hp L20b at 14lbs or about 1 bar should make 200hp or close to it. Google it, there are tons of info on it because everyone always wants to know what they will make at so and so psi blah blah lol. I just ate too many bacon wrapped scallops and cant type so much out lol. For our convo purposes 1psi:10hp holds up.

 

There is def way more to flow tuning it then just adding or subtracting inches from the mani. Though in gross specs just adding or subtracting length will most def effect your max hp and tq accordingly. 6" runner is beneficial if you want higher end hp and easier breathing at higher rpm and 9" is beneficial if you want higher tq lower in the band.

 

I personally opted for a short anti reversion manifold because I could make up tq with higher rear dif ratio and still be happy. Where as I couldnt do much to make up for hp loss. Say nothing for the fact a main point of itbs to for better breathing at high rpms. Though thats not the only point and that was just my personal thinking for my build.

[Tristin]

There is def way more to flow tuning it then just adding or subtracting inches from the mani. Though in gross specs just adding or subtracting length will most def effect your max hp and tq accordingly.

 

Thats my point exactly. People running R1 carbs wont do any of the other necessary items to enact a great enough change in tuning... everyone just slap a bank of carbs on a manifold and goes. Then they find whatever velocity stacks fit and are cheap. So the only thing in that they can change (if they were to make their own manifold) would be runner length.

[datzenmike]

Well I would tune the length of the velocity stacks. Didn't someone here get a muffler shop to flair some exhaust pipes? All the roadster uses is a 1/4" flair on the SUs.That's so good an idea I may do it. All you have to do is add or subtract some length and it doesn't have to be straight, hell look at the KA24DE intake.

 

Yes there is port matching all the way from end to end but length tuning is going to make way more gains than port matching ever will. (I would do both).

[Tristin]

I believe it was Vintage who had an exhuast shop flare a set for him... but he did that because it was cheap, not because he wanted a specific shape. And yes Mike, as long as the pipe is smooth, its not required to be straight.

[72240z]

Tuning stacks is like a whole other can of worms. Thats going into air turbulence and pulse. Most data I read seems to hands down support longer vs shorter stacks within reason.

 

Ya the ka is an example so is the ld28. The vg33 in nissan trucks is too its mani is actually folded doubling the length. Lots of engines to is, its free low end tq lol. Thats why most trucks utilize that style mani where the sports car counterparts with the same motors dont.

[Tristin]

Tuning stacks is like a whole other can of worms. Thats going into air turbulence and pulse. Most data I read seems to hands down support longer vs shorter stacks within reason.

 

Here is a little image:

 

[VintageRice]

VERY interesting image! My Stacks might actually be REDUCING airflow. ooops.. still look rad though. :D

[VintageRice]

Well I would tune the length of the velocity stacks. Didn't someone here get a muffler shop to flair some exhaust pipes? All the roadster uses is a 1/4" flair on the SUs.That's so good an idea I may do it. All you have to do is add or subtract some length and it doesn't have to be straight, hell look at the KA24DE intake.

 

Yes there is port matching all the way from end to end but length tuning is going to make way more gains than port matching ever will. (I would do both).

 

Yuuuuuup. Me.

 

 

[Tristin]

At least they look good right?