FTO AUSTRALIA

Here's my maths, anyone good at this and know a lot about calculating supercharger boost?
127mm crank pulley
Alternator pulley 52mm
Supercharger pulley 65.5mm (stock pulley)
127/52=2.44 ratio crank to alternator
52/65.5mm alternator to supercharger pulley (stock) = 0.79

2.44*0.79 = 1.93 final ratio

SC outputs 650cc per pulley rotation (I think, different figures out there though some say more)
650*1.93=1254cc per crank turn as we're driving the charger faster than the crank.
(just for interest 8000 engine rpm * 1.93 =15440 supercharger rpm at max engine revs - I will be driving it a lot faster than this though in the near future)

Engine breathing capacity (in an ideal world) 999cc per crank turn (half engine displacement).
1254-999=255 extra cc being put into the engine per crank turn so this is under boost.
255/999=0.255 bar
14.7*0.255=3.75 psi expected (i'm expecting it to be low on the stock pulley)
I have a boost gauge arriving in the next week or so too to help verify.

I'm going to get a 51 or 52mm supercharger pulley ordered, that should see me at 9psi but need to verify my actuals first.

Wouldn't the 'absolute pressure' logged be vacuum? Where in the cycle is it reading 164?

I could be wrong, probably am, but absolute pressure should read around 70 at idle, then climb as you open the throttle until the boost kicks in and then it will drop and pass through to negative (which is actually positive) as it builds boost? Or have I got this all wrong

Shane001 wrote:Wouldn't the 'absolute pressure' logged be vacuum? Where in the cycle is it reading 164?

I could be wrong, probably am, but absolute pressure should read around 70 at idle, then climb as you open the throttle until the boost kicks in and then it will drop and pass through to negative (which is actually positive) as it builds boost? Or have I got this all wrong

Ooo I don't know that's got my head in a spin.
The 164 is at 70% throttle and around 5000rpm I think but also think it's a red herring (or just too hard to get my head round).
Going to take the readings from the Greddy sensor voltage instead.

On mine I log and tune to absolute pressure, and idle is about 70kPa, (farken Bens big penis) W.O.T! full revs is about 260kPa, and off throttle from full revs drops to nearly 0. I'm NA so that definitely has to be vacuum. (wish it wasn't though... )

Edit: Farken Bens big penis farken word farken filter

Interesting since I made a base map for mine it's running great not rich anymore but idle is now at 2k when warm going for dyno tune this week but would like to sort it myself. How did you lower yours rob?

Interesting since I made a base map for mine it's running great not rich anymore but idle is now at 2k when warm going for dyno tune this week but would like to sort it myself. How did you lower yours rob?

Mine was nothing to do with the tune it was all just little air leaks here and there.

Today I made some scones.
But I also made and fitted a spacer for the drivers side engine mount out of some left over 5mm ally plate and also fitted 5mm of washers to the gearbox mount (6 x 2.5mm washers to be exact - 3 bolts) to drop that side.


I'm hoping this will have lowered the engine 5mm giving me extra bonnet clearance but to be honest may not have done anything due to the cross member underneath, do I also need to fit washers here?

I use washers on the lower cross member as well...

I was going to say that you needed to do the cross member as well. But Ben got in first lol.

Ok thanks guys I will whack some washers on there too.

One of the first drives, not great videos i'm afraid and only really good for hearing the noise (which will be much louder when I drop to a smaller pulley).
http://s248.beta.photobucket.com/user/R ... 8.mp4.html
http://s248.beta.photobucket.com/user/R ... 9.mp4.html

I'm not waiting for more boost, just ordered a Kavsport supercharger 20% reduction pulley (for mini cooper s).

Rob Furniss wrote:I'm not waiting for more boost, just ordered a Kavsport supercharger 20% reduction pulley (for mini cooper s).

I'm expecting boost to increase to somewhere in the region of 8-9psi which will be pretty nice (hopefully i've got my calculations right and it's no more than 9psi).
My bottom engine mounts are not up to the job and were already on their way out, been in touch with RPW about some poly ones but need to take mine off and drive up there to match them up. (In my wifes car not mine with no bottom mounts)

F*ck RPW, get meek inserts, press 'em in.

viewtopic.php?f=23&p=249882#p249882

Thanks Ben, will have a read through that thread shortly.

Did a little bit of logging earlier and i'm getting 100% throttle now and 1.68 volts on the greddy 3 bar map sensor at 3500 rpm and 1.77 volts at 5800.
Found this table earlier:
Pressure Sensor Specs:
PSI - Voltage - inHg

-14= 0.54 -- 28.504
-13= 0.60 -- 26.468
-12= 0.67 -- 24.432
-11= 0.74 -- 22.396
-10= 0.81 -- 20.36
-9= 0.88 -- 18.324
-8= 0.95 -- 16.288
-7= 1.02 -- 14.252
-6= 1.09 -- 12.216
-5= 1.16 -- 10.18
-4= 1.22 -- 8.144
-3= 1.29 -- 6.108
-2= 1.36 -- 4.072
-1= 1.43 -- 2.036

0= 1.50
1= 1.57
2= 1.64
3= 1.71
4= 1.78
5= 1.84
6= 1.91
7= 1.98
8= 2.05
9= 2.12
10= 2.19
11= 2.26
12= 2.33
13= 2.40
14= 2.46
15= 2.53
16= 2.60
17= 2.67
18= 2.74
19= 2.81
20= 2.88
21= 2.95
22= 3.02
23= 3.09
24= 3.15
25= 3.22
26= 3.29
27= 3.36
28= 3.43
29= 3.50
30= 3.57
31= 3.64
32= 3.71
33= 3.77
34= 3.84
35= 3.91
36= 3.98
37= 4.05
38= 4.12
39= 4.19
40= 4.26
41= 4.33
42= 4.39
43= 4.46

So looks like i'm getting 4psi at 5800 which I was expecting, glad i've ordered that smaller pulley.

Well half of what i'm waiting for to double the boost has arrived, just a tool to remove the stock pulley which is an interference fit.


The other thing i'm waiting for is a much smaller pulley - a two piece clamp on style, and should see me above 8psi.
Think I will get a bit of heat on it too to help pop it off, i've used one of these (although a different make) before on the other build and not successfully, ended up taking it somewhere for them to sort so hoping to have better luck.

Once fitted I will have to drive carefully until I fit the rad and pump for the charge cooler (something more to order!) as it's dry at the moment so not really doing much.
I've also had a digital boost gauge arrive but don't have anywhere to mount it yet, I have an old Kenwood double Din stereo at the moment so might buy a single din one to free up a slot and mount the gauge underneath in a blanking plate.

After that it's cambelt change time (I have an oil leak and not sure when the cambelt was last done since I bought the car), then getting an engineering certificate and then a tune on the rollers at RPW.
Looking forward to getting it down the drags after that and seeing what she will do.

In before Christmas?

Astron_Boy wrote:In before Christmas?

Lol

It is running and i've been using it but only at 4psi, had an 80km run the other day (and didn't blow up).
But no I won't get all that done before crimbo but expecting the boost-upping-pulley any day which is easy to fit once I get the stock pulley off.
I think it will be into January before I get the rad and pump fitted and attempt to do the cambelt etc, I want to get it to the drags in January.