Supercharging Through Bike Carbs

[steve_wilson]

thread revival...

 

as the winter modification season comes round again i've been looking into doing this on my 2.0 pinto, currently running around 10.8:1 compression ratio on standard pistons, which is pushing it as it is, so i will need to reduce compression if i am to go ahead with a supercharger.

 

 

i'm sure this is a question that has a million answers but what compression ratio should i be aiming for to run a supercharger? or if there is an online guide or calculator that i could use to work it out...

 

 

to decrease the CR i was thinking about either using a thicker head gasket or a de-comp plate. what are peoples thoughts on this?

i dont really want to put forged bits in the engine due to cost, i would rather run low boost.

 

 

i have a piper300 cam in at the moment which if i remember correctly has too much overlap for any type of blower, so what cam would people recommend for a blown pinto?

 

thanks, steve

[Guest loopyonion]

Not to start an argument, but I've always run a higher compression with a good size intercooler. Keeping the air cool will help reduce problems, boost can be sorted easier as its a supercharger, and has a linear curve in comparison to turbo spool. I've never been a fan of 7.5 or 8:1 ratios, two flat to drive.. If you must lower, speak to Mike at Ferriday Engineering, he can sort you a spacer plate to your spec thickness.

[Guest loopyonion]

Maybe aim for 9.5:1 with 6-7psi, good ecu with MAP sensor input to retard the timing etc. decomp plate would help, but the pistons won't take much pinking before they crack.

 

Cheapest option over winter would be to look for some cosworth pistons on eBay, however, could be a minefield of knackered equipment.

[Guest ianjenn]

The need to lower compression will depend on the size of the supercharger. If you stick with the M45 or M62 I don't think you will need to adjust the compression ratio.

[steve_wilson]

hi all

 

thanks for the replies, will do some calcs tonight to see what can get me 9.5:1 hopefully the standard thickness head gasket will do it, dont want to run a decomp plate unless i have to.

 

i was thinking an m45 will do the trick, however i can imagine that at some point i'll get bored of the power and want more, so maybe an m62 is what i should go for?

 

getting back to cam choice... which is best for a blown pinto. i'm guessing high lift with no overlap?

 

thanks, steve

[Guest Pinto]

ring newman cams and speak to david hes a really helpful chap and will advise on what you need, good prices there too compared with same spec profiles from kent etc... high lift short duration.. not sure when standard pinto springs bind but he will know..

 

a decomp plate will aid detonation too.. piston to head clearance is optimum @ .75mm - 1.0mm any bigger squish areas lead to problems

 

I'm charging my NA YB and its running 10.5:1 CR. not really sure on the number crunching calcs but I found this post a good read..

 

http://www.preludepower.com/forums/archive/index.php/t-231658.html

[steve_wilson]

looks like a standard 1.6mm head gasket will get the CR down to about 10:1 which i feel a bit more comfortable with.

 

cam wise, ive done a bit of research and people say the standard injection cam is very good, but the ideal cam is one of the short duration, high lift cams i.e. the high torque cams or "caravan cams" as they are sometimes known.

 

i will make a new thread about this now as i'm going more and more off topic!

 

thanks everyone so far, steve