BlurComet

While searching, I found the question 'What does prepping the carb for boost mean, and how do I do it?' asked several times within threads, but none were answered. So, I thought that some of you veterans could maybe post up a clear definition of what all this entails, and share your own personal experiences. Would be a great addition to the archive!

lovintha7

Well, you've got 30 views and no replies.

I can tell you the problem with it, but I'm not sure of the solution, you may want to contact Sterling on this one.

The problem:

When you pressurize the carb higher than the fuel pressure, the air forces the fuel back through the lines to the tank. A rising rate FPR helps with this, but I think they're something with the floats that you need. I believe they have to be filled with foam or else they "float" in the compressed air, closing the fuel off.

$100T2

iTrader: (1)

If you are gonna start a thread with "How to:" in the title, you should actually know how to do it yourself, and post the step by step process. People are gonna think this thread is helpful, and it currently is not.

Re-Speed.com

iTrader: (3)

Boost is pressure. Just visualize all the possible air leaks when air is forced in the top to find what you need to block off or fix. Pressure will push fuel out every space it can find. i.e. around throttle shafts and stuff. The floats will be under pressure and could collapse as well. You should pick up the Corky Bell turbo book.

You can also build a box around the entire carb. This lessons the amount of work to get it to run under boost.

-billy

BlurComet

Well, it is titled a How-to thread for when we get a good description and possibly pictures going, and it can be posted in the archive. Just a little more search friendly. I also plan on learning how to and doing this and posting up some useful info, just thought a thread like this could help out some people before I get mine done (probably about 3 months before I can take a look at it).

Now then, aside from $100T2's whining (j/k), there's some good stuff going here If anyone else would like to contribute, feel free

Directfreak

iTrader: (2)

I was just going to post this. This would be an easy and "relatively" inexpensive solution to boost prepping a stock nikki. All you would need is the right jetting, and you'd be good.

BlurComet

Very cool..... I'm assuming what you guys are talking about refers to more than just a carb bonnet? I think I may have seen this somewhere.... I'll take a look around....

vipernicus42

iTrader: (4)

That makes some strange sense!

With just the bonnet, the pressure inside the carb is way higher than the pressure outside the carb, making what's on the inside want to come out any way it can.

By boxing off the whole carb, you equalize the pressure on both sides an so the problem is lessened/eliminated.

Still though.. it's a kind of ghetto solution. There *is* a way to boost prep a nikki, I don't know how, but I think it was FBII who got Robert to do his.... IIRC.

Jon

FB II

yes, talk to robert at rotary shack.

Re-Speed.com

iTrader: (3)

A carb box is more old school than ghetto. Strapping the carb box down with duct tape would be ghetto.

The only thing I can think of would be a rising rate regulator so the fuel pressure goes up when the boost goes up. This should keep it from pushing the fuel back at the pump. Oh, and jetting as mentioned above.

There is a formula for the size the box should be.

Or you can draw through.

Seriously though, the book I mentioned above has 90% of the answers you are looking for. I will warn you though, both draw through and blow through have some information but the book mostly talks about boost with FI. As most have moved on to this.


-billy

coldy13

Good luck getting anyone that knows how to boost prep a nikki to tell you. Robert is the only person I can think of that knows how to do it. I used one of his boost prepped nikkis for a while, it worked great. I bet he would sell you a boost prepped nikki, but I doubt he will tell you how to do it.

BlurComet

Heh was afraid that would be the case. Guess everyone's out to make a buck I also thought that a FPR would do the trick for the fuel push back problem, and I will be running one of these to make sure mine goes well. bwaits, I really don't have much to do today, so I think I'll swing by Books-A-Million and see what they got. Good to see more people contributing

85rotarypower

From my understanding, boost preping a nikki is basically the same as a holley. You need to seal ANYTHING that might possibly leak. This means finding a way to seal the throttle shafts and some way to keep the gaskets from possibly blowing out. Next you need to make your floats "hard" so they don't collapse under boost. The floats on a nikki are hollow. I don't know what you would use for this, but some kind of expanding foam thats resistant to gas should work. The last part has already been mentioned. A 1:1 rising rate fuel pressure regulator. Basically, for 1 psi of boost, the FPR will raise the fuel pressure 1 psi.

If your only going to run low boost (no more than 7 psi), then you shouldn't have a problem with leaks in stock form. But the solid floats and RRFPR are a must.

Sterling

The Nikki has solid floats. And sealing up the shafts, etc, is not the problem. Fuel pressure issues are fixed with a rising rate regulator.
The problem is that the transition circuit is engineered for 14.7- 16 psi, not for 21+ psi.

BlurComet

Nice! I have some knowledge concerning carbs, but I've never heard of a transistion circuit

Does what your saying mean that if you were building a 6-7 psi turbo system, you wouldn't even have to mod the carb?? I wouldn't recommend this to everyone reading, just trying to get some clear info

Re-Speed.com

iTrader: (3)

More info please sterling. Where does the 14.7/16 come from?

-billy

dscsk8er55

I think what he is saying is that the stock carb fuel press. is at 14psi. So 14psi (base pressure or without boost) + 7psi (boost from turbo) = 21psi. Tell me if i am wrong or not.

Sterling

14.7 psi is atmospheric. Add your boost to that.
The idle air bleeds and transition bleeds and emulsion tubes all work great at atmospheric pressure...14.7 psi @ sea level, +/- a little as you go up & down.
But every orifice has a point where the flow rate is maxed out completely- just like a stock Nikki can only flow 313 cfm @ 14.7 psi, whereas a Sterling can flow 465.
The emulsion tubes need to bleed off signal and aerate the fuel at the same time, and they do that really well...at 14.7 +/- psi.
The best way to maintain perfect fuel pressure and boost calibration is to put the regulator in a box with the carb. Then there are no "bounces" in pressure, and the change is reflected immediately. Rising rate regs have to be done correctly to work, and I'm not the one to ask; I've never installed one.

I'm not certain what Robert does, and I haven't asked him. I respect the idea of "proprietary information"...That is to say, someone has the right to keep info to himself that he has worked hard to research and develop until he no longer needs to make money on it. He said it just wasn't worth the effort when he sold me a stack of Nikkis last year. He showed me several cars that had his distinctive Weber box, and I doubt he wants to play with Nikkis. (Too much work, I think. )
We tried a boost-prepped Sterling with FBII, but we must've misunderstood him when he stated that he didn't mind working with us to develop the project, because he didn't send it back to us to be worked on further when it failed. Instead, as I understood it, he sent the carb off to Robert -under the advisement of Seanrot. (Thanks again, nimrod. )
Of course, that left a pretty foul taste in my mouth because I have my own reasons for supporting and respecting the idea of proprietary info.
So after the bullshit stopped, we put the project on the back shelf. When Carl started working on it again, he got it as close to air tight as you can for under a gazillion bucks, but we didn't have the test rat or the time for the jetting R&D.

Since then, we haven't had enough inquiries to warrant the extra time to develop the Boost Prepped Sterling Carb. It will have to wait until we get another test rat, or I start the SterlingCharger project.

Re-Speed.com

iTrader: (3)

A little less info sterling. J/K

So as I understand it from this thread:

The stock NIkki can be run under boost by building a box around it. A rising rate regulator within the box would be a good idea.

The stock Nikki can be run under boost by building a carb bonnet and sealing off a number of spots on the carb.

Neither solution does anything for the internal circuitry being less than adequate without modifications.

Nikki floats are solid and can withstand the pressure.

Development from either party is not moving forward at this time.



-billy

BlurComet

Very cool, Sterling. You really know your stuff Sorry to read about how the development of the Sterling Boost Prepped carb never really got off the ground, it's a shame If you do start having some customers show a genuine interest, how much time do these developments usually take? Ah, that's not exactly a fair question; nevermind.... Thanks for that last post; if people can follow what your saying, it really helps!

Sterling

bwaits, a regular old regulator can go in the box, so long as it's diaphragm can handle the pressure.
BlurComet, Robert is gonna know alot more about turbo setups than me, but he'll keep terying to sell you on a Weber and say that a modded Nikki can't touch it. I really disagree.
As far as the development of the Boost Prepped Sterling Carb, it's a matter of what makes money. We make so little money doing just modded street carbs as it is, that R&D has to be justified at some point by revenue. So even if we did have some testing done, there's no telling "how much is enough" when it comes to a boosted engine.
-Ya wanna slap on a carb that we've tried with great success on one other guy?
Our motto for the short-term would be what? ..."Well, it didn't blow the first one up! "


You have to really screw up big to wreck an NA engine with a carb, but a turbo? It doesn't take much to wreck one.
I'm not saying that when Carl and I decide to go for broke and quit our jobs to live the "good life" and roll around in all the bucks that come pouring in from the ole Nikki modding sugar boat ( )that we won't try it again, just that it's not top priority.

Right now, we're working out some details on easier production of a ported manni configuration that Carl spent about a gazillion hours getting just right. (The BananaManna?)

680RWHP12A

it took me a year to figure out how to boost prep a nikki, now that i know how(all the little tricks) its really not that hard... but like sterling said , "poprietary information...That is to say, someone has the right to keep info to himself that he has worked hard to research and develop until he no longer needs to make money on it. " thanks for that sterling....
dont get me wrong, i always try to help people as much as i can
as far as fb2's nikki that rx7carl did, i never commented on that deal and i definatly never recieved the nikki to inspect it/fix it/etc..

i do prep nikkis to work with boost but i stress they use alot of gas and dont perform as a stock nikki would as far as driveability

FB II

yea, seanrot may have suggested some stuff but i never went thru with it. had i, then my car would have been running a year ago instead of a month ago.

what robert says is true, it does waste some gas, but that really doesnt matter to me and you do sort of have to learn the science of driving it correctly. when i'm challenged on the highway i cannot just slam the gas. but if i brake boost everything is great.... which is what i like to do anyways. now that i've got it down it's as if nothing changed. people think i have a fuel injected car when they ride in it, but they don't realize what my foot is doing to create that smoothness. but all i can say is it's pretty fuggin fast. definately beat all my expectations!

BlurComet

Hmmm.... good to read these posts.... How prepping the nikki effetcs drivability many people don't take into account. It's common to lose mileage due to the larger jets, but FBII, could you and Robert give us a close estimate of MPG this setup should average (conservative driving, because I doubt to many of us really worry about the gas needle when we want to let her loose!)?

EDIT: BTW Robert, I sent you guys an email before I even started this thread Was just wondering if you guys check your mail anymore

FB II

well, it really depends. honestly i can't because every time i drive it i only cruise for a bit until i get a nice stretch of road... which there's always a stretch no matter where i go... and i boost the **** out of it. but even so, a full tank has yielded me around 240miles. i used to get around 280 with the n/a setup on average which included alot of wot runs. so really it's not too bad considering i'm over double my hp. but, the car runs even cooler than before, and timing is always advanced so maybe that helps? doesnt matter tho because i get to all my destinations with such ease. oh and highway passing is so easy now... just give it half throttle in 5th.. makes about 5psi and i'm going from 60 - 80mph in a few seconds and i'm ahead of traffic. AHHHHHHHH i will never go n/a again!