I remember that name from some of my old Hot Rod mags. A modern top fuel car must advance the timing in the neighborhood of 70 degrees BTDC because nitromethane burns so slow and sooooooo long.



MrHorsepower

 

Drilling vs Spring Cutting

I feel both of these mods go for the same goal from different angles.

Somebody somewhere (this site?) said if the spring was too spongy, it could cause the slider to fluctuate over rough terrain, causing unintended thottle position changes. Logical, but debatable from either side of the argument.

If I drag raced, I would have cut the coils. Beings I ride across the desert at stupid speeds, I opted to drill the slide.

jbt

 

I was curious what effect cutting the spring would have on hill climbing? Will the slide drop fast enough with the short spring to maintain torque?

 

I have an end cap and stage 3 jetting on my DS... I took it to an 1/8th mile track and ran it I was stuck at consistant 9.80s I went over took off the airlid and took the filter out completly just to test it out... I droped 2 10ths down to 9.60s made 3 passes and they where all 9.60 then I put the filter back on and went home..lol... so in my experience more air the better even to the extreem of not running a filter...

 

Buttfungus and Mr HP definately make sense. What about if you could run the direct mount K&N and also hook up the carb vacum tube at the same time? Come to think of it, I think my quad was a little slower when I ran 100 octane as well. Guess I will have to do some experimenting of my own. Im not to big on cutting the slide or spring on the carb. I figure Mikuni put a considerable amount of MONEY, TIME, EFFORT and R&D into the design of the carb before selling it.

 

DSJobber,

You might want to order up an extra spring to give it a try. I have the spring cut on one of my DS' and I did notice a difference on one, but not the other. (I moved the spring from one to the other.) Unfortunately for me, I wasn't jetted properly for the area (like 6,000 feet instead of the usual 2000 - 3000) and the extra gas it put in the cylinder made the low end rich bog I had even worse. I'm eager to try it again at a lower altitude where the machine has the proper jetting. (It made my 100% stock Baja bog, and my 2001 DS with E-Series pipe showed no notable change - both of them running 87 octane gas now.)

 

Sounds like a fun way to melt a piston! - your running quite lean

 

if I was running lean wouldent it be popping or something??? now I have a K&N filter on there and the lid removed...

 

I use my own fabricated inlet system for my direct mount K&N. I have the vacuum line hooked up to the inlet system and in my opinion it works quite a bit better than stock.

I'm pulling enough air that I need a 187.5 main jet (mikuni) to supply enough fuel.... My slide is open all the way for sure!!!

 

Gaskett, do you have a pic of this adaptor? Iwona see[img]i/expressions/face-icon-small-happy.gif[/img]
although I havent tried the clap on system, I have tride the no lid and jetting up to 180, it felt great on bottem but I lost races to bikes I could beat with the lid on and jet to 172.5.
I would like to see the custom adaptor though.