actually yeah... our caravan to sac the other day for sacS2Kdays was around 85-90 degrees, i loved how the car ran.

im took my 80mm horn today and replaced it with the new 50mm from Fuji Racing... i will try it tomorrow.

50mm length



80mm length

 

Longer, as long as you can get away with.

 

yeah true, but these short ones will be used for normal driving, prolly put a Uni filter on it... to and from the races... then switch over to the longs ones for autox.

im gonna do a dyno with the short ones with filter and compare the graphs.

 

I'm curious to see what kinda difference the 50mm's make vs the 80mm's....

I like your injectors

 

thanks nate... i love those injectors too. only 50-60% duty cycle at WOT. and theyre small and subtle.

50s i heard will give you more topend and 80 is lowend to mid. i like the 80s but jimmy from fuji sent me these small ones for street use.

 

I'd be willing to bet that your right, the 50's should actually be used on the track, as they'll probably have the highest peak gains, where the 80's should be used on the street or autocrossing for the added midrange.

I thought I was running 80's until i noticed that your horns overlap...mine are separated by about 1mm...now I'm curious as to what ones I'm running...

 

Im no ITB expert, but I think he is simply referring to the length of the horns, not the width. You have have shorter horns that overlap or longer one that dont. That would be based on the taper angle.

Also, yall could be talking apples and oranges as the fuji ITBs could be a different distance from the head then the jenveys, thus the length of the horns would be adding length from a different mounting positions.

 

Unfortuneately like with most aspects of this engine, basic engine theory does not apply. The longer we lengthened the runners the more power we made everywhere, they probobly want to be 160mm long or more. Obviously I am running more cam and a longer stroke but that said, one would think based on your thoery (which I too shared at one point) a shorter runner would provide greater gains up top, this simply did not pan out however. Packaging ofcourse is an issue however. Maybe if someone ran an ITB setup in a Lotus 7 kit they could really prove out the optimal length. We simply don't have enough room in there to go the distance. I think you will find a noticeable power loss with the 50mm length. I will post my dyno graph of the longer horn setup along with horn specs as soon as we figure out what exactly worked best for us.

 

Fuji Racing is a Jenvey ITB... uses all jenvey TB, manifold, rail... then put together with his FPR, etc.


it is as simple as longer runner, low and midrange tq and power.... shorter is all topend. diameter will be for air velocity.

nate, yeah my 80mm is a jenvey horn, they overlap... i think the diameter on your is ok, you just need it to be 80mm long, and it will have wider range.

 

where are you getting the different length hornes from? i would love to find a supplier for different length hornes...

Ryan