Hi All
Okay so my current engine is a zetec st170 running off bike carbs, think from zx6r or gsxr and the ignition is from a megajolt. In my forever search
for more power I stumbled across info about adding a supercharger. (it already has a 50hp shot of nitrous). So I have fitted an eaton m45 (think it is
?) from a mercedes. At the moment it is still on the same jets as the carbs were set at prior to supercharging.
The fuel is now fed from an MSD 2225 fuel pump to a mallory 4309 fuel regulator (which gives fuel pressure 1psi above boost). The regulator has a line
from the homemade plenum and the carb float bowls are pressurised using an 8mm pitot tube. I have lowered the floats by 1mm and set the baseline fuel
pressure to 2.5psi.
I had my first run out today and was surprised to find that the fuel pressure goes off the scale of my 15psi gauge on acceleration. I was expecting a
boost pressure of around 7psi Is this correct? My return line is 8mm and not restricting things.
Actually after checking I think I have miscalculated my actual boost. The crank pulley is approx 130mm and the supercharger pulley 70mm giving ratio
of 1 - 1.8 so 10-11000 revs of the supercharger at 0.7l per rev. Think that means I will get 12psi boost but I am confused about engine displacement.
Now I'm thinkin I might need an intercooler as the boost is higher than i thought?? and if I do have to fit an intercooler which one is best
there are thousands on ebay!!
I have a rolling road booked in for next week so just wanted your opinion on my set up. Is there anything I have missed? ?intercooler? The engine
seems to over rev at gear change a bit but otherwise runs okay? I have fitted a bypass valve from magnatec to ease the pressure at idle. Any other
suggestions will be most welcome?
Best wishes
alex
[Edited on 11/4/11 by ianjenn]
[Edited on 11/4/11 by ianjenn]
Excuse my naivety but how do you supercharge carbs? I'm guess with an air box but would love to find out more....
well I'm no expert and things could go hideously wrong. After much internet surfing there is loads of info about turbocharging motorbikes and I have applied the same theory to my car. Using a pitot tube (type into google) I am pressurizing the float bowl so that the carbs can function under boost. The rolling road will be very interesting!!
I also have a ST170 with ZXR9 carb's.
Would love to supercharge mine one day....
Some info on intercooler sizing here:http://www.unclebobsturbos.com/newbie.html
Given my above post I have no idea if it's any good...
Good work, I look forward to seeing how this one progresses As I've said before I'd like to swap the weber on my XR2 turbo for a set of bike carbs.....
Hi All
At my last rolling road the air correction jets were blocked off as I was running an air filter. I am wondering if the air correction jets now need to
be unblocked as the carbs have a plenum and are pressureised. Does anyone know if I am makin any sense. Just wondering if this is the cause of my over
revving atgear change
thanks
alex