who has any experiances for a 4-1 system for there V4, the only thing i remember hearing about them was it wasn't overly great for the mid range... but i might remember it wrong.

i have a DIC system getting repaired and am looking forword to fitting it but would like to know what others have thought it there 4-1 and did they encounter problems with the rev range.

cheers
rhory

Not sure mate, Iv heard twin stacks are best for top end power hence why they use them for road races like IOM more than short circuit racing, might just be bollox I heard tho

I met Graeme France on saturday and he said they adjust the position of their end can to tune the power curve on their 29's, quite interesting really, that might help on your system as the 29 is a 4-1

I reckon the V4 has it's own issues to be dealt with as it is a pair of twins rather than an IL4 which has the balancer pipes betwen 1,3 and 2,4.

Moving the can, or changing the tuned length of the system will move the peak power around - shorter pipes suit higher revs and so, with my best armchair engineering skills, should be a peakier motor.

On the V4 Rhory it seems that the stacks are able to produce the outright power figures but the fact that HRC ran single cans for a long time on the 30s and 45s shows that they can work.

Is your DIC system one of the bent ones? Alloy pipes and wonky can?

I have had lots of systems nowadays and the best for power was the black HRC wannabe one that was too loud and melted my fairings.. The stack was great but I am not sure it had the top end of the other system.

The Hiperform is a long system and in the short running I had on the NC race bike it felt great. A dyno will tell all though..

yes mark the DIC system i have would have had the curved can but someone whopped it off before i got the hold of it and whilst they where in the mood to chop things they chopped off two more important bits ,see pictures ....


and it's got a little reminder of where the sidestand goes ...

i was given a MICRON carbon can with a bit of damagelast week, so i chopped off the marks and it brounght the can lenght down to 390mm,10mm off whats on the rest of the bikes.

i've only ever seen one other bike with a DIC system and it was in a shoproom over here,sold pretty quickly and was never seen again. so i'd like to hear what people think of a 4-1 on a V4,surely someone on the WWW or GreyBike has had one before,maybe francey or our friends in the US ?

ok help me with my understanding of this as maybe we can piece something together before i fit it then i can come back with an answer for sure

4-2-1 = systems offer a good mid range but lower bhp
4-2 = systems offer a higher bhp but mid range suffers
4-1 = systems ......insert answer here ?

I'll take a stab

You are looking at the exhausts wanting to evacuate the gases by allowing lower pressure at the end so the flow is the right direction
You also want the secondary effect of the pressure waves assisting in scavenging the linked cylinders and also, if you are really lucky and have a lot of valve overlap, then you can have the exhaust assist in sucking in the intake charge.

I see it that the shorter a primary exhaust pipe (the most important one) then the higher revs, shorter frequency pipe it is.

So, the "sweet spot" for scavenging is a higher up the revs.

Ideally you want the pipes paired - so the 4-2 - or 2-1 can be tuned so mch better.

I cannot figure out the crank throws for the 1,3 and 2,4 cylinders as I am drinking..but I think they are 180 degrees apart?

hmm rambling a bit..hmmm



So, a 4-1 is going to be a lightweight, larger bore (?) and shorter primaried system..and so suited to high revving efficiency.

royster81 wrote:ok help me with my understanding of this as maybe we can piece something together before i fit it then i can come back with an answer for sure

4-2-1 = systems offer a good mid range but lower bhp
4-2 = systems offer a higher bhp but mid range suffers
4-1 = systems ......insert answer here ?

my understanding of it was this:-
4-1= topend power
4-2-1= mid range
4-2 = somewhere between mid-top