
Supercharger Throttle Response
#1
Posted 16 April 2009 - 12:45 PM
driving my mini yeseterday (120bhp 1380) I realised I needed way more power than a step in camshaft and a raised CR would get me, so I'm now seriously looking into an m45 supercharger conversion. my block hasn't been decked before (only had a very light surfacing) and the pistons are powermax 73.5 (i think these are 9cc dish as standard) and sit 40 thou down the bore
I prefer the supercharger idea over a turbo, as I'm not looking for mega power, and I like the smooth delivery of the SC setup over the sudden torque surge of a turbo. I think the torque of the 1380 with a low boost (8-10psi) supercharger could work very nicely.
What's the throttle response like on the suck through supercharger setups? I've been looking at vids on youtube, and saw this earlier:
LW7iIXagMNo
it's a lovely setup, but it looks like it's got a massive delayed response when the throttle is opened in the first few seconds of the vid.
Is this due to the long inlet tract? would it be less sluggish if a weber were used mounted on the side of the charger?
Aside from the master cylinder clearence, is there any reason why the carb can't be mounted closer to the charger, like in the Moss Kit fitted to matrix's mini featuers in mini world a few months ago? I'm guessing the HIF kits available only bring it to the front for ease of fitment.
I've got both a weber 45 and an HIF44, as I've only just upgraded to the weber this year, so that's not an issue. I'm not looking to do it until after Bh2N either, as I've just got the car perfect, and I want to have a summer of hassle free enjoyment from it for a change (yea right).
Any advice on various suck through setups using the Eaton would be great. having looked at all the kits available, the Vmax kit seems of far better quality than the others, and the range of additions such as charge cooling, large bore pipework, and choice of weber or SU, seems very impressive.
Cheers
Nick
#2
Posted 16 April 2009 - 01:32 PM
#3
Posted 16 April 2009 - 02:44 PM
#4
Posted 16 April 2009 - 02:46 PM
#5
Posted 16 April 2009 - 03:07 PM
The pickup on my 1380 now is very quick indeed, I wouldn't want to end up with really poor throttle response.
Anyone got any comments about whether it's worth using a weber with the setup? when the HIF44 seems to be enough to cope with up to 200bhp or so....
I love the idea of the vmax kit, with a few extras, if I could add 40bhp to my engine that would be amazing!
#6
Posted 16 April 2009 - 04:37 PM
ah cool, so long as that's not the norm then!
The pickup on my 1380 now is very quick indeed, I wouldn't want to end up with really poor throttle response.
Anyone got any comments about whether it's worth using a weber with the setup? when the HIF44 seems to be enough to cope with up to 200bhp or so....
I love the idea of the vmax kit, with a few extras, if I could add 40bhp to my engine that would be amazing!
I would say youd be looking at about 160bhp running bout 7psi,the boost is very quick literally with the throttle.tell u what ill post a video later if i can,u on here later? might need a hand uploading not the best with computers !!!!!!!!
#7
Posted 16 April 2009 - 04:47 PM
you will add more than 40 bhp fitting a super charger
my first supercharged engine was standard except for a 276 cam and made 111.8 bhp and 106 lbf toqure at the wheels
adding a supercharger will add 40-50% more power
a good 1380 should see about 150-170 at the wheels
my jonspeed kit superchargered 1340 engine on dyno no throttle delay
another vid
Edited by THE STIG, 16 April 2009 - 05:08 PM.
#8
Posted 16 April 2009 - 05:35 PM
I would say youd be looking at about 160bhp running bout 7psi,the boost is very quick literally with the throttle.tell u what ill post a video later if i can,u on here later? might need a hand uploading not the best with computers !!!!!!!!
That would be awesome if you could mate! If you need a hand with posting the vid, add me on msn ([email protected]) and I can talk you through it

you will add more than 40 bhp fitting a super charger
my first supercharged engine was standard except for a 276 cam and made 111.8 bhp and 106 lbf toqure at the wheels
adding a supercharger will add 40-50% more power
a good 1380 should see about 150-170 at the wheels
my jonspeed kit superchargered 1340 engine on dyno no throttle delay
Wow, I didn't expect it could make as much as that. it's currently running 100 at the wheels, so 140+ at the wheels would certainly be VERY interesting!
What power did your 1340 make Stig? Having had both, are there any major pros and cons of both the Jonspeed or the Vmax kit? I'm currently swaying towards Vmax, as it looks like a very professional setup, and I like the idea of stainless manifolds, and the larger bore manifold kit they offer.
I'm currently trying to work out what CC head I'll need for the correct compression ratio, and the only thing I'm stuck on is my current deck volume. I'm comming out with 4.31cc, but I'm unsure if that's correct.
pistons are 40thou down the bore (after a 10thou skim on the block) which is 1.016mm
pi 73.5²/4 = 4243.46mm² = 4.243cc x 1.016 = 4.31cc
based on that, a 28cc head would give me 8.56:1, or a 30cc head would give me 8.24:1
I'm just not sure my deck volume calcs are correct.
Sorry, I've gone a bit off topic here!
#9
Posted 16 April 2009 - 06:26 PM
so 12.5 for pistons and gasket and 30cc n head = 8.3
really want 8.1 , 8.2 max
i use this caculator to work out my compression ratios http://www.johnmaher.../enginecalc.htm
as for kits my personal experiance
vmax took 12 weeks to turn after being told 5 and had to go back as was twisted never answered phone or emails for weeks
jonspeed closer to me and always someone there
found no differance in performace between the kits jonspeed had a few things that made it better and easier to fit than vmax kit
its up to people to check out all kits and make up there own mind
#10
Posted 16 April 2009 - 06:32 PM
#11
Posted 16 April 2009 - 08:05 PM
As far as compression ratio goes, is there really that much difference between 8.2:1 and 8.3:1? I know some people with the minispeed kit are running 8.7:1 without problems.
if I were to have my pistons machined for more dish, I assume the engine would have to be stripped down. I'd ideally like to not pull the bottom end apart, as it was very solidly built just 6k ago, and if I were to pull it apart, I'd want to replace all the bearings and rings, which I don't think is needed yet.
Am I right in thinking that 30cc is the max a head chamber can be taken out too?
I know there are decompression plates available, but these sound like such a bodge to me.
#12
Posted 16 April 2009 - 08:33 PM
But for a moderate power increase and great midrange pull an SC can be good.
#13
Posted 16 April 2009 - 09:43 PM
throttle response is near instant and very good.
#14
Posted 16 April 2009 - 09:54 PM
My current engine peaks around 7000rpm, and pulls very well to 7500. On an engine already producing near 120bhp, surely the charger would add more than just 15-20bhp?
Thanks for all the info guys, it's pretty clear I've got a lot to learn about forced induction setups on a mini!
#15
Posted 16 April 2009 - 10:13 PM
you also need to take into account the ring land volume which i think is 0.78cc for a 1380. this is in the yellow vizard book. its the volume between the piston and cylinder wall above the top compression ring
cheers
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